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6 Long-Term Disposition INTRODUCTION Long-term disposition of the excess plutonium from dismantled nuclear weapons the third stage in the process beginning with dismantlement of weapons and intermediate storage of fissile materials will be a long, complex, and expensive endeavor. · All of the plausible options stretch out over decades, counting both the time required to get ready to begin and the time needed to complete the disposi- tion campaign. · All options are likely to involve a net economic cost, rather than providing a net profit from this material. · All options involve unresolved issues and risks of uncertain magnitude. · None of the options is sufficiently developed to be chosen as the preferred approach until outstanding questions are answered. This chapter offers not a final answer but a road map for arriving at one; it is intended to provide guidelines for the necessary national and international debate to come, to narrow the focus of attention to the subset of options most likely to minimize risks, and to provide plausible end points for the dismantle- ment and storage activities now under way. 141
142 LONG-TERM DISPOSITION In considering this situation, the committee has reached the following set of recommendations: · Because of the long times required for all disposition options, Missile ma- terial storage arrangements lasting well over a decade will be an essential part of any disposition policy (see Chapter 5~. These storage arrangements should be designed to meet the same stringent standards of security and accountability applied to stored weapons, and they should include international monitoring. Because of the uncertainties surrounding all disposition options, these inter- mediate storage approaches must be designed to be capable of extension for many decades if necessary. The appropriate arrangements for intermediate storage are to a large extent decoupled from long-term disposition decisions and are currently more urgent. · Storage should not be extended indefinitely. Because of the liabilities of indefinite storage of excess weapons material for the nonproliferation and arms reduction regimes, the risk of breakout involved in such storage, and the risks of theft in the event of a breakdown in government authority, there are sub- stantial reasons to pursue other disposition approaches that provide additional barriers against use of this material in weapons. Indeed, one of the key criteria by which disposition options should be judged is the speed with which they can be accomplished, and thus the degree to which they curtail the risks of pro- longed storage. · Disposition options other than extended storage should be pursued only if they reduce overall security risks compared to leaving the material in storage, when both the final form of the material and the risks of the various processes needed to get to that state are considered. In the current unsettled circumstances in Russia, this minimum criterion is not trivial. · To the extent practicable, safeguards and security measures should main- tain the "stored weapons standard" of accounting and security throughout the disposition process. The process must take place under agreed monitoring and security that form part of the overall regime for management of fissile materials described in previous chapters. . · An appropriate standard for the ilna1 product or clsposltlon options IS that they transform the weapons plutonium into a physical form that is at least as inaccessible for weapons use as the much larger and growing stock of pluto- nium that exists in spent fuel from commercial nuclear reactors. (This existing problem will itself change over time as the radioactivity decays, repositories or monitored retrievable storage sites become available, and approaches to safe- guards and security and nuclear fuel cycles evolve.) Incurring substantial addi- tional costs, complexities, risks, or delays in order to go further and eliminate the excess weapons plutonium completely or nearly so would not be justified
LONG-TERM DISPOSITION 143 unless the same approach were to be taken with the global stock of civilian plutonium. · The two most promising alternatives for the purpose of meeting the spent fuel standard are: 1. The spent fuel option, which has several variants. The principal one is to use the plutonium as once-through fuel in existing civilian nuclear power reactors or their evolutionary variants. Candidates for this role are U.S. light- water reactors (LWRs), Russian LWRs, and Canadian deuterium-uranium (CANDU) reactors. The use of European and Japanese reactors already licensed for civilian plutonium should also be considered for Russian weapons plutonium. 2. The vitrification option, which would entail combining the plutonium with radioactive high-level wastes as these are melted into large glass logs. The plutonium would then be roughly as difficult to recover for weapons use as plu- tonium in spent fuel. A third option, burial in deep boreholes, has until now been less thor- oughly studied than options 1 and 2, but could turn out to be comparably attractive. Further research is needed to answer important outstanding questions concern- ing each of these three options. · For the spent fuel option, existing or partly completed reactors are pre- ferred over newly built reactors, to avoid the delay and capital cost of building entirely new facilities. If problems of licensing and public approval for existing reactors prove insurmountable, one or more new reactors might be built on a government-owned site; if so, these should be reactors of sufficiently well- proven design so as not to create additional technical and licensing uncertain- ties. Reactors of more advanced design examined by the committee do not offer sufficient advantages for this mission to offset the delays and extra costs their use would entail. · Although the spent fuel standard applied to excess plutonium is an ap- propriate goal for next steps, further steps should be taken to reduce the prolif- eration risks associated with nuclear power and the global stock of plutonium, including plutonium in spent fuel. Options for near-total elimination of pluto- nium may have a role to play in the longer-term effort to reduce the risks posed by global plutonium stocks. Research on defining and exploring these options should be continued at the conceptual level. ' The spent fuel option, in which the weapons plutonium would actually be converted to spent fuel, should not be confused with the spent fuel standard: it is merely one means of meeting that standard. As discussed later, spent plutonium fuels would have some differences from ordinary spent fuels, including higher plutonium concentrations.
144 LONG-TERM DISPOSITION · Institutional issues in managing plutonium disposition may be more complex and difficult to resolve than the technical ones. The process must be carefully managed to provide adequate safeguards, security, transparency, and protection for environment, safety, and health; to obtain public and institutional approval, including licenses; and to allow adequate participation in the decision making by all affected parties, including the U.S. and Russian publics and the international community. Adequate information must be made available to give substance to the public's participation. A more effective decision making proc- ess to address these issues is needed within both the U.S. and the Russian gov- ernments, as discussed in Chapter 1. · It is important to begin now to build consensus on a road map for deci- sions concerning long-term disposition of excess weapons plutonium. Because disposition options will take decades to carry out, it is critical to develop op- tions that can muster a sustainable consensus. The remainder of this chapter outlines the considerations that led to these conclusions. It begins by describing the categories into which the many techni- cal options for long-ten disposition can be divided and the criteria for judging among them. It then goes on to discuss each option and how it fares under those criteria. Finally, it outlines the committee's recommendations. THE RANGE OF CHOICE The options for long-term disposition can be divided into three broad classes, as illustrated in Figure 6-1: 1. Indefinite Storage: In this approach, the plutonium would continue to be stored in directly weapons-usable form indefinitely, with no specific decision concerning whether, when, and how storage would be terminated.2 During such storage, safeguards and security would provide the primary barrier to pro- liferation. Political measures, such as a formal commitment to non-weapons use and continuing safeguards, would provide the primary barrier to reuse of the material for weapons by the state from whose weapons the material came. Al- though intermediate storage is essential to all disposition options, for reasons already mentioned the committee does not recommend that it be extended in- definitely. 2. Minimized Accessibility: In this concept, barriers would be created physical, chemical, or radiological to make the steps needed to use the pluto- nium in weapons (acquisition of the plutonium, processing, weapon manufac- ture) more difficult either for potential proliferators or for the state from whose 2In separating "indefinite" storage from "inte~ediate" storage, this report uses "indefinite" to mean approaches in which storage itself is considered the disposition option, and no end point to the storage has been defined. In this nomenclature, storage would be considered "intermediate" even if it lasted for several decades, if the material were awaiting processing in a chosen disposition option.
LONG-TERM DISPOSITION 145 Indefinite Storage ~ Materials Remain in Weapons / Usable Form Barriers to Reuse / in Weapons Based on Politics and Secutity Measures Intermediate Storage FIGURE 6-1 Plutonium disposition Minimized Accessibility Physical, Chemical, or Radialogical, Barriers Reduce Availability for Weapons Use Elimination ~ Material Nearly \ Completely Removed from \ Human Access \ OPTIONS Use Reactors (no reprocessing JO required) / LWR, CANDU, LMR, MHTGR, etc. Disposal Vitrification Deep Borehole Underground Explosion Sub-Seabed Repository Burial Use Reactors (reprocessing required) LWR, CANDU, LMR, MHTGR, etc. An Disposal Space Launch Ocean Dilution weapons it came. The plutonium would continue to exist, and some form of safeguards would continue to be required. The spent fuel, vitrification, and deep-borehole approaches are examples. 3. Elimination: In this concept, the plutonium would be removed from hu- man access completely, or nearly so, for example, by fissioning the plutonium atoms or by launching it into deep space. The point in such a process at which the plutonium can be considered "eliminated" for example, whether burning 99 percent of the plutonium would be sufficient- is somewhat arbitrary, but any "elimination" option should ensure that retrieving enough plutonium for a nuclear explosive from whatever remains would be extremely difficult. One plausible standard is to describe any option in which only a few grams of plu- tonium would remain in a large truckload of waste as an elimination option.3 3 The International Atomic Energy Agency (IAEA), for example, considers that materials no longer require safeguards if the remaining fissile material in them has been "consumed," or so diluted as to be "practically irrecoverable" for weapons use. Quantitative measures for termination of safeguards, which might provide one standard for judging when to consider fissile material "eliminated," have not yet been finalized. Interview with Thomas Shea, IAEA Safeguards Division, August 1993. See, for example, A. Fattah and N. Khlebnikov, "A Proposal for Technical Criteria for Termination of
146 LONG-TERM DISPOSITION Use or Disposal. A complementary categorization is whether the pluto- nium would be used or disposed of. The use options would fission some frac- tion of the plutonium in power reactors, converting its energy content into elec- tricity. The disposal options would throw away the plutonium's energy content. Since plutonium is more expensive to use as nuclear fuel than widely available low-enriched uranium, either the use or the disposal options would require a subsidy. The different signals relating to civilian nuclear power that would be sent by using excess plutonium or throwing it away are discussed in more detail below. U.S. and Russian Contexts. It is possible-even likely that the optimal approaches to long-term plutonium disposition will be different in the United States and Russia. The risks involved in storing, handling, processing, and transporting plutonium are much higher in Russia under present circumstances, and the two countries' economies and plutonium fuel policies are different. Most of the key officials responsible for these issues in the Russian government strongly prefer options that use surplus weapons plutonium to generate electric- ity in reactors; it would be difficult to convince Russia to pursue disposal op- tions in the near term (though perhaps not impossible, particularly with suf- ficient financial incentives). Although U.S. and Russian disposition approaches may differ, rough paral- lelism in the timing and scale of long-term disposition would be desirable, so that both nations' available plutonium stocks would remain comparable. After long-term disposition, neither nation's excess plutonium should be much more accessible for use in weapons than the other' s. While the United States and other industrialized countries cannot dictate particular disposition options to Russia, they will have a significant influence on Russian decisions in a variety of ways ranging from simply setting an ex- ample on the one hand, to financial assistance, negotiated agreements to pursue particular approaches, or outright purchase of former Soviet weapons pluto- nium on the other. Other Forms of Military Plutonium. The primary focus of this report is the excess weapons plutonium resulting from arms reductions, which is initially in the form of pits from dismantled nuclear weapons. Both the United States and Russia, however, also have large quantities of military plutonium in scrap and residues from past operations of their nuclear weapons complexes, most of which are also likely to be considered excess. Although the amount of pluto- nium in these forms is smaller than the amount in pits that will result from arms reductions, the volume is much greater; the variety of forms of material is wide; and the environment, safety, and health (ES&H) risks are substantial for Safeguards for Materials Characterized as Measured Discards," Journal of Nuclear Materials Management, May 1991.
LONG-TERM DISPOSITION 147 some forms. Even characterizing the constituents of these materials accurately is difficult. Some of these materials can readily be processed to plutonium metal or oxide that could then be fed into many of the disposition options described be- low. Some reactor options (typically the more advanced ones that would take longer to bring on-line) are more capable than others of handling variations in the form of the initial fuel feed, though there are materials that none of the re- actor options could plausibly handle. Moreover, processing of some of these materials would raise difficult environmental issues of its own. The vitrification option, described below, may be a particularly promising approach for stabiliz- ing and ultimately disposing of the plutonium in these less tractable forms. CRITERIA FOR DISPOSITION OPTIONS Security issues should be the primary criteria for choice among the long-term disposition options. Each long-term disposition approach generates risks and opportunities with respect to theft, rearmament, and the arms reduc- tion and nonproliferation regimes that depend on political and technical factors that will evolve over the long time periods involved in disposition. The commit- tee judges the following security risks related to long-term disposition choices to be of greatest concern: Risks of Storage: Prolonged storage of excess weapons plutonium would mean a continuing risk of breakout, as well as of theft from the storage site. In addition, extended storage of large quantities of excess fissile materials, par- ticularly in the form of weapons components, could undermine the arms reduc- tion and nonproliferation regimes. Thus, long-term disposition options should minimize the time during which plutonium is stored in accessible forms. The timing for each long-term disposition option is dependent on three factors: its technical readiness or uncertainty, the speed with which public and institutional approval could be gained, and the time required to implement it once developed and approved. Risks of Handling: Nearly all disposition options other than indefinite stor- age require processing and usually transportation of plutonium, in ways that could increase access to the material and complicate accounting for it, thus in- creasing the potential for diversion and theft. In order to ensure that the overall process reduces net security risks, an agreed and stringent standard of security and accounting must be maintained throughout the disposition process, ap- proximating as closely as practicable the security and accounting applied to intact nuclear weapons. The committee calls this the "stored weapons stan- dard." Hence, choices among long-ten disposition options should be weighted in favor of those that minimize:
148 LONG-TERM DISPOSITION · the number of transport steps, and the risks involved in each; · the number of sites at which plutonium is handled, and the risks at each of those sites; and · any processing steps with high accessibility and low accountability. Risks of Recovery: A third key security criterion for judging disposition options is the risk of recovery of the plutonium after disposition. The committee believes that options for the long-term disposition of weapons plutonium should seek to meet a "spent fuel standard" that is, to make this plutonium roughly as inaccessible for weapons use as the much larger and growing quantity of plutonium that exists in spent fuel from commercial reactors. Options that left the plutonium more accessible than this existing stock would mean that this material would continue to pose a unique safeguards problem indefinitely. Conversely, as long as civilian plutonium exists and continues to accumulate, options that went further than the spent fuel standard and sought to eliminate the excess weapons plutonium entirely would provide little additional security, unless the same were done with the much larger amount of civilian plutonium. Thus, options for the next steps in long-term disposition of weapons plutonium shouldfocus on those in the "minimized accessibility" class. Over the longer term, however, steps should be taken to go beyond the cur- rent spent fuel standard, to further reduce the accessibility for use in weapons of the entire global stock of plutonium. Elimination options are among the pos- sibilities for this purpose and could be seen as a second, long-term step for all plutonium (both military and civilian). The difficulty of using plutonium in spent fuel for nuclear explosives arises from its chemical dilution in the fuel (with plutonium typically consisting of roughly 1 percent of the spent fuel weight); the radioactivity of the fission products with which the plutonium is mixed (which, for years after the fuel leaves the reactor, would give anyone attempting to the handle the spent fuel without appropriate protection a lethal dose of radiation within minutes); and the isotopic composition of the plutonium (which includes more of the less de- sirable isotopes of plutonium than weapons-grade material does, somewhat complicating the construction of nuclear explosives). (See "How Accessible is Plutonium in Spent Fuel?" p. 150.) Eventually, physical barriers will be im- posed as well, when this material is consigned to geologic repositories; these physical barriers will have to compensate for the long-term decline of the radio- logical barrier. Chemical barriers alone, such as diluting the plutonium or combining it chemically with other elements, will not be sufficient to match this combination of chemical, radiological, and isotopic barriers, and therefore cannot meet the spent fuel standard. Thus, the leading options the committee has examined in- volve both chemical and radiological barriers (in the case of the spent fuel and vitrification options) or substantial physical barriers (in the case of the deep-borehole option).
LONG-TERM DISPOSITION 149 The three security criteria just outlined represent a kind of coarse filter for disposition options: any option that cannot bring the weapons plutonium to the spent fuel standard within a few decades with low to moderate security risks along the way does not deserve further consideration. Signals Relating to Civilian Nuclear Fuel Cycles. The goal of long-term disposition should be not only to ensure that the plutonium from dismantled weapons is not reused in weapons, but also to reduce net security risks from all fissile materials. Thus, policymakers must be attentive to possible indirect ef- fects that the choice of disposition options might have on the proliferation risks posed by other fissile materials in the world, as well as its direct effects on the surplus weapons material. The political signals sent by the choice of particular disposition approaches might encourage the development and use of more pro- liferation-resistant nuclear fuel cycles; encourage the use of more proliferation- prone nuclear fuel cycles; or serve to set a standard for improved safeguards and security for other fissile materials. Under the Carter administration, the United States decided not to reprocess civilian plutonium or pursue plutonium fuel cycles, and launched a major in- ternational effort to convince other countries that' such separated plutonium fuel cycles were uneconomical and posed significant proliferation risks. Elements of that policy were incorporated in the Nuclear Non-Proliferation Act of 1978, which remains U.S. law. Although the Reagan and Bush administrations re- versed the Carter administration's opposition to domestic use of separated plu- tonium, for economic reasons none 'has ensued. Both of these administrations continued to strongly oppose plutonium separation in countries judged to pose proliferation risks, while raising no objections to continuing plutonium separa- tion programs in Japan and Europe. On September 27, 1993, the Clinton ad- ministration announced a nonproliferation initiative that makes clear that, while the United States will not interfere with reprocessing in Japan and Europe, "the United States does not encourage the civil use of plutonium and, accordingly, does not itself engage in plutonium reprocessing for either nuclear power or nuclear explosive purposes." The initiative called for an exploration of "means to limit the stockpiling of plutonium from civil nuclear programs."4 Given this background, policymakers will have to take into account the fact that choosing to use weapons plutonium in reactors would be perceived by some as representing generalized U.S. approval of separated plutonium fuel cycles, thereby compromising the ability of the U.S. government to oppose such fuel cycles elsewhere. Conversely, choosing to dispose of weapons plutonium with- out extracting any energy from it could be interpreted as reflecting a general- ized U.S. government opposition to plutonium recycle. Either choice could have an impact on fuel cycle debates now under way in Japan, Europe, and Russia. 4 White House Fact Sheet, "Nonproliferation and Export Control Policy," September 27, 1993.
150 LONG-TERM DISPOSITION
LONG-TEAM DISPOSITION 151
152 LONG-TERM DISPOSITION Choice of a reactor option would not necessarily reopen the issue of reproc- essing, however, since the spent fuel standard can easily be met by once-through fuel cycles. (Only the use of reactors for plutonium "elimination" would require reprocessing.) Whatever is done with excess weapons plutonium, moreover, will affect only a small portion of the world's current and future plu- tonium inventory. For either the use or the disposal options, if the United States wishes to maintain a policy of generally discouraging separated plutonium fuel cycles, or if it wishes to make support for such cycles contingent on stringent safeguards and security measures, it will need to make a clear statement of how its choice fits within that broader context. Non-Security Criteria. Protection of the environment, safety, and health (ES&H), along with public and institutional acceptability, are also essential criteria for all disposition options. Additional important criteria, described in Chapter 3, include the cost of the option, and its compatibility with other poli- cies and objectives. As noted elsewhere, however, the committee does not believe that the fu- ture of civilian nuclear power which depends on economic, political, and technical issues outside the scope of this study should be a major criterion for choosing among disposition options. Tritium Production. Tritium production was not part of the committee's charge, and it has not examined alternatives for this purpose in detail. There is, however, no essential reason why plutonium disposition and tritium production need be linked, and there appear to be good arguments why they should not be. At present, arms reductions are continuing at a rate of more than 5 percent per year, thus outpacing tritium decay. The reactor or accelerator capacity that would ultimately be needed to produce enough tritium to support an arsenal of the size currently projected is many times less than that needed to carry out disposition of 50 tons of weapons plutonium over 20 to 40 years. Thus, tritium production capacity will be easier to provide than plutonium disposition capac- ity and should not bias consideration of alternatives for the latter purpose. At such low production levels, accelerator production of tritium may be preferred over reactor production, and purchase could also be considered, though that would raise other policy issues. From a policy perspective, producing new weapons materials in the same reactor being used for disposition of other weapons materials would have im- portant ramifications for the nonproliferation and arms reduction regimes, local political support, and safeguards. In particular, President Clinton's commit- ment to put excess U.S. fissile materials under International Atomic Energy Agency (IAEA) safeguards would mean that if tritium production and pluto- nium disposition were carried out in the same reactor, either the tritium pro- duction reactor would have to be under IAEA safeguards or the plutonium would have to be removed from safeguards during disposition.
LONG-TERM DISPOSITION 153 Cost savings from carrying out both plutonium disposition and tr~tium pro- duction using the same process and facilities would probably not be large, and must be balanced against the complications outlined above. In summary, the committee believes that the potential for producing tritium should not be a ma . ~ ~ . . . jor cnter~on for c eciding among plutonium disposition options. Figure 6-5, at the end of the chapter, summarizes in a matrix format the committee's judgment of how the various options rate under these criteria, with the main options representing the rows and the criteria the columns. Most of the remainder of this chapter is devoted to a description of the three major categories of options for long-term plutonium disposition, directed toward sup- porting the judgments in that chart.5 THE OPTIONS Indefinite Storage Indefinite storage could be pursued for several decades with costs and ES&H risks substantially lower than those of the other disposition options. New storage facilities would eventually be required, as would plutonium processing to deal with long-term deterioration of the pits. This would increase costs and ES&H risks, but these might still remain below those of most other disposition options. This option would also offer the greatest flexibility for later use of the plutonium. A decision to store excess weapons plutonium indefinitely, however, would have a number of important liabilities. Of all long-term disposition options, indefinite storage would entail the highest risk of breakout and of proliferation by theft from the storage site. Prolonged storage of large quantities of excess fissile materials, particu- larly in the form of weapons components, would send the message that the na- tion storing these materials was maintaining the option to rebuild its Cold War- era nuclear arsenal. Such perceptions could politically undermine efforts to pursue deeper reductions, to bring other nations into the arms reduction regime, and to maintain and strengthen the nonproliferation regime. Finally, plutonium storage without a designated end point would be difficult to justify to the public; communities in which plutonium is now stored have demanded and received assurances that they will not become the final resting grounds for this material. s The reactor, accelerator, and vitrification options are discussed in more detail in Management and Disposition of Excess Weapons Plutonium: Report of the Panel on Reactor-Related Options, (Washington, D.C.: National Academy Press, 1994), while the other disposal options are considered in Appendix C. References for the descriptions of the various options in this chapter can be found there. The description of the reactor options that follows is more extensive than that of the disposal options, in part because there are more variants of the reactor options, and in part because the issues involved in the reactor options are somewhat better understood; the relative lengths of the discussions, however, should not be construed as indicating the committee's preferences.
154 LONG-TEAM DISPOSITION For these reasons, poststorage disposition options should be explored, de- cided on, and carried out expeditiously. Continuing to store this material in- definitely would mean either (1) a decision that the security risks of the proc- essing steps involved in any of the other options were too great for the foreseeable future, particularly given conditions in Russia; (2) a rejection of the disposition options proposed to date, and an expectation that better options would be developed in the future; (3) a failure to decide and act; or (4) an ex- plicit decision to maintain a capacity to rapidly reincorporate this plutonium into nuclear weapons. More exotic approaches to storage, designed to reduce the liabilities just described, have been proposed. For example, plutonium pits in casks might be placed in monitored, retrievable storage in a mined geologic repository.6 As described below, such approaches would not be acceptable for long-term dis- posal. Although they might have some advantages for intermediate storage, they would do little to reduce the breakout threat or the political hazards of prolonged storage, and the risk of theft can be addressed by other means at ex- isting or planned storage sites. Minimized Accessibility Options Reactor Options A wide range of reactors-existing, evolutionary, and advanced~ould use weapons plutonium in their fuel (for an illustration of the general steps in- volved, see Figure 6-2~. By doing so, they could seek to meet the "spent fuel standard" described above, typically by using the fuel in a "once-through" cycle, or they could seek to eliminate the plutonium nearly completely, by repeatedly reprocessing and reusing it. The spent fuel options are described here, while the elimination op- tions are described later, in a section of their own. In the spent fuel approach, a substantial fraction of plutonium would re- main in the spent fuel. The main goal of this approach is not so much to de- stroy the plutonium by fissioning the plutonium atoms or transmuting them into other elements-as to contaminate it with highly radioactive fission prod- ucts, requiring difficult processing before it could be used in weapons. In addi- tion, this option would shift the isotopic composition of the plutonium from "weapons-grade" toward "reactor-grade." As noted in Chapter 1, however, formidable explosives can still be made from reactor-grade plutonium.7 6 See Luther Carter, "The Other Side of the Mountain," Washington Post, August 22, 1993, p.C4. 7 Weapons-grade plutonium, produced by comparatively brief irradiation of uranium in reactors, typically has some 93 percent plutonium-239 (Pu-239) and 6 percent Pu-240; reactor-grade plutonium contains much larger fractions of Pu-240 and other isotopes. See "Reactor-Grade and Weapons-Grade Plutonium in Nuclear Explosives," Chapter 1, p. 32.
LONG-TERM DISPOSITION 155 Powdered PuO2 (~1 g/cc) ~Mixed Oxide (MOX) BAND PmIl=t lo. < 1 Pad in 10 Fl~r.trir,nl Power ~UtDUt FIGURE 6-2 Steps in the spent fuel option Source: Redrawn from The Department of Energy's (DOE's), Plutonium Disposition Study (Washington, D.C.: U.S. Department of Energy, 1993~. In all the once-through options, enough plutonium would remain in the fuel to require safeguards comparable to those employed for typical commercial spent fuel. For all plutonium destruction fractions achievable in such a once- through cycle (roughly, between 20 and 80 percent), the quantity of plutonium remaining in the spent fuel would be substantial between 10 and 40 tons re- maining from a disposition campaign beginning with 50 tons of weapons plu- tonium. Although substantial, these residual quantities would be small com- pared to the growing world stock of civilian plutonium in spent fuel. Thus, within the range of plutonium destruction achievable without reprocessing, the specific destruction fraction would have little impact on overall security risks, either those of the remaining plutonium in this spent fuel or those of the global stock of plutonium in spent fuel. Another possibility, discussed as a separate option in some studies, is to use much briefer irradiation of the weapons plutonium typically for only a few months to "spike" the plutonium with fission products, creating some radia- tion barrier to its use in weapons more rapidly (or with fewer reactors) than would be possible in the spent fuel option. In itself, this approach would not meet the spent fuel standard, and hence would not provide an adequate barrier to use of the material in weapons over the long term. But since the resulting
156 LONG-TERM DISPOSITION partly used fuel could be reused in reactors, this spiking approach might be considered as a possible step along the road to the spent fuel option. Existing, Newly Built, and Advanced Reactors for the Spent Fuel Option. Either existing reactors (possibly with modifications) or newly built reactors constructed for the purpose could process excess weapons plutonium into spent fuel. New reactors built for this purpose, particularly those of more advanced design, would require more time and money. The initial capital cost of a new nuclear reactor amounts to billions of dollars, and such reactors would take many years to build particularly in the United States, where nuclear cons~uc- tion has encountered intense opposition in recent years, and no reactors have been ordered since 1978. The number of nuclear reactors already available in the United States would not be a limiting factor for this mission; fuel fabnca- tion capacity and political, institutional, and licensing issues will be the pacing elements. For the conversion of weapons plutonium to spent fuel, new reactors would not offer sufficient advantages to offset their disadvantages in time, cost, and uncertainty unless institutional and political obstacles to the use of exist- ing or partly built reactors were to prove insurmountable. If that were to be the case, a new reactor could be built on a government- owned site, thereby potentially simplifying the licensing and public acceptance issues. In that case, the reactor chosen should be one of sufficiently known de- sign to avoid unnecessary technical uncertainties and licensing delays. For transforming weapons plutonium into spent fuel, the more advanced designs do not offer sufficient advantages to overcome their liabilities of cost, timing, and uncertainty.8 The same conclusion holds for new fuel types for existing reactors (such as so-called nonfertile fuels, which do not contain uranium-238 (U-238) and therefore do not produce more plutonium as they are burned). Research and development on advanced reactors and fuel types are of in- terest only in the context of the future of nuclear electricity generation, includ- ing the minimization of security and safety risks. As part of that future, they These cost, timing, and uncertainty issues are described in more detail in Management and Disposition of Excess Weapons Plutonium: Report of the Panel on Reactor-Related Options (op. cit.). Past analyses have reached similar conclusions regarding these liabilities of more advanced reactor designs. The Department of Energy's (DOE's) Plutonium Disposition Study (Washington, D.C.: U.S. Department of Energy, 1993) for example, warned that advanced concepts such as liquid metal reactors and high-temperature gas-cooled reactors were "significantly less mature than the light water reactors," which "would be expected to result in greater development and deployment costs and schedule risks."(Vol. 1, p. 4). Similarly, a study prepared for DOE in February 1993 estimated that the total costs of such advanced systems (measured in net dollars per kilowatt-hour) would be significantly higher. (See Ronald P. Omberg and Carl E. Walter, "Disposition of Plutonium from Dismantled Nuclear Weapons: Fission Options and Comparisons," Lawrence Livermore National Laboratory, February 5, 1993, UCRL-ID-113055, p. 19.) The committee was also influenced by the National Research Council report on the future of nuclear power, which rated these advanced systems as "low" for economy, market suitability, maturity of development, and licensing, while evolutionary light-water reactors were rated "high" in all of these respects, see National Research Council, Nuclear Power: Technical and Institutional Options for the Future (Washington, D.C.: National Academy Press, 1992), p. 105.
LONG-TERM DISPOSITION 157 may offer the possibility of pursuing the "elimination" approach in the long term, not only for weapons plutonium but also for the much larger quantities of civilian-sector plutonium. Advanced reactors should not be specifically devel- oped or deployed for transforming weapons plutonium into spent fuel, because that aim can be achieved more rapidly, less expensively, and more surely by using existing or evolutionary reactor types. In saying this, the committee does not intend to recommend either for or against the development and deployment of advanced reactors for commercial electricity production, which is beyond the scope of its charge. If new reactors are built for commercial power production, and if by that time the disposition of weapons plutonium has not been com- pleted, their possible contribution to that goal should be reviewed in the context of the alternatives available at the timed U.S. law prohibits the use of commercial nuclear facilities for military applications. There is no prohibition, however, on the use of military material for civilian purposes, the situation examined here. Indeed, use of low-enriched uranium (LEU) from formerly military highly enriched uranium (HEW) stocks in civilian reactors is already planned; use of fuels produced from plutonium stocks is different in specifics, but not in principle. In Russia, the adequacy of existing reactors for the weapons plutonium disposition mission is not as obvious as in the United States, as few Russian reactors are safe enough to continue operating over the long term. But, as de- scribed below, the VVER-1000 LWRs the safest of the Russian reactors would be sufficient to carry out this mission. Here, too, if new reactors must be built for the plutonium disposition mission, for political or institutional reasons they should be existing or evolutionary types rather than advanced types. As noted above, long-term disposition options may differ in significant re- spects in Russia and the United States. In what follows, the use of each coun- try's own reactors is considered first, followed by other nations' reactors that might also be used. The description of the use of U.S. plutonium in U.S. LWRs will be the most detailed, with other options described in significant part by comparison to that base case. U.S. PLUTONIUM IN U.S. LWRs Feasibility and Reactor Requirements. Commercial reactors of the types currently operating in the United States, known as light-water reactors, offer the technical possibility of transforming excess weapons plutonium into spent fuel within a few decades. Such a plutonium disposition campaign could probably begin within roughly a decade, paced by the need to provide a pluto- nium fuel fabrication capability (no such facility is currently operational in the United States) and a variety of institutional issues, including licensing and 9 Advanced reactor options for production of spent fuel are described in more detail in Management and Disposition of Excess Weapons Plutonium: Report of the Panel on Reactor- Related Options (op. cit.) and are considered only briefly below.
158 LONG-TERM DISPOSITION public acceptance (no U.S. LWRs are currently licensed to handle plutonium fuel). Once started, the campaign could be completed within 20-40 years, paced by the number of reactors participating (which involves important trade-offs between the advantages of processing plutonium more rapidly with more reac- tors and the associated risks of greater transport and more widely dispersed handling of plutonium); whether the reactors use plutonium in one-third or in all of their reactor cores; the fraction of plutonium incorporated in the fuel; and the average length of time the fuel is kept in the reactor. A subsidy would be required, compared to providing the same electricity from the same reactors with standard LEU fuel (an issue discussed in more detail below). For this purpose, plutonium would be mixed with natural or depleted ura- nium to produce a "mixed-oxide" (MOX) fuel, which typical commercial LWRs could use in one-third of their cores without major modification. The technical feasibility of using such fuels is amply demonstrated. Indeed, a num- ber of reactors in Europe are operating with one-third MOX cores today (with fuel performance demonstrated to be comparable to that of uranium fuel), and more reactors are slated to begin using such fuels in both Europe and Japan in the near future. Using one-third MOX cores, U.S. LWRs, with typical capacities of about 1 gigawatt-electnc (GWe) each, could transform 50 metric tons of excess weap- ons plutonium into spent fuel- substantially similar to what is already pro- duced by these reactors in 150 to 250 reactor-years of operation.~° Put an- other way, 5-8 GWe of reactor capacity (out of a total U.S. LWR capacity of about 98 GWe) would have to be used to accomplish the job in 30 years. Using MOX in all of the reactor core would cut the number of reactors or the time required by a factor of three. Because the nuclear characteristics of plutonium differ from those of uranium, however, most current-generation LWRs could use MOX in their entire reactor cores only if they were signifi- cantly modified, by adding more control rods and possibly increasing the effec- tiveness of each rod. To modify already operating reactors in this way would require safety review and a substantial shutdown penod, and the costs have not yet been estimated. There are, however, three operating U.S. reactors and one unfinished reactor, called System-80s, that were designed with the inherent capability to handle a full core of MOX fuel though such operation is not in- cluded in their current licenses and a detailed safety review to assess the ade- quacy of the design would be required. In addition to the fraction of the reactor containing MOX, two other factors determine how many reactor-years would be needed to process a given amount a For example, EWRs of 3000-MWt (thermal megawatts) capacity running at a capacity factor of 70 percent, using one-third MOX fuel containing 2.5 percent plutonium by weight, kept in the reactor to an average burnup of 30,000 megawatt-days per metric ton of "heavy metal" in their fuel (30,000 MWd/MTHM), would process 208 kilograms of weapons plutonium per reactor-year, requiring 240 reactor-years to process 50 metric tons of plutonium, or eight reactors operating for 30 years. ~ These are the three reactors at Palo Verde, Arizona, and the incomplete Washington Nuclear Project 3 (WNP-3) reactor in Washington State, discussed in more detail below.
LONG-TERM DISPOSITION 159 of plutonium: the percentage of plutonium in the MOX, and the length of time the fuel remains in the reactor (known as the burnup, measured in megawatt- days per metric ton of "heavy metal" (uranium or plutonium) in the fuel- MWd/MTHM).~2 For example, the System-80 reactor could process 50 metric tons of excess weapons plutonium in 60 reactor-years using a 100 percent MOX core with a relatively low enrichment of 2.5 percent and an average burnup of 31,000 MWd/MTHM; increasing the initial enrichment to 6.8 percent (roughly the maximum likely to be possible without requiring changes to the reactor) would allow the job to be done in 30 reactor-years, even if the burnup were in- creased to 42,000 MWd/MTHM. The safe use of enrichments of 6-7 percent requires neutron-absorbing ma- terials such as erbium (known as "burnable poisons") to help control the nu- clear chain reaction; this too would require safety review. In addition to reduc- ing the number of reactor-years required, such high enrichments would reduce overall fuel fabrication costs, as discussed below. Fuel Fabrication. Providing adequate plutonium processing and MOX fuel fabrication capability would be an important pacing factor for processing excess weapons plutonium in U.S. LWRs. Plutonium pits would have to be shipped from Pantex (where no plutonium processing capability yet exists) to a site capable of disassembling the pits and converting the resulting metal to plutonium oxide. No facilities for carrying out pit processing on the required scale are currently operating, but facilities at Savannah River, Los Alamos, and possibly elsewhere could be modified for this purpose, and as mentioned in Chapter 5, new technologies for efficient pit con- version are being developed at the national laboratories.~3 Because plutonium is more radioactive and requires greater safeguards than low-enriched uranium, facilities for fabricating uranium fuel cannot sim- ply switch to fabricating plutonium fuel; special MOX fabrication facilities must be provided. Although there are no MOX fabrication facilities currently operating in the United States, a nearly complete facility designed to produce plutonium fuel for experimental fast reactors at the Hanford site in Washington State, known as the Fuel and Materials Examination Facility (FMEF), could be modified to produce MOX fuel for light-water reactors. Although further study of this modification is required, the committee has received estimates (which may be optimistic) that this facility could be modified to produce 50 metric tons of fuel per year or more (containing roughly 3 metric tons of weapons pluto- nium, at 6-7 percent enrichment), while meeting current safeguards and ES&H standards, within roughly five years of receiving a go-ahead, for a cost in the range of $75-$150 million. Alternatively, a new plutonium fuel fabrication fa '2The reactor's capacity factor its average output in a given period divided by its rated capacity also has some impact. Most well-run reactors have capacity factors in the range of 60-80 percent for LWRs, and as high as 90 percent for CANDUs (which do not have to shut down to refuel). }3 This step-which is necessary for most, but not all, of the disposition options win probably cost of order $100-$300 million for 50 tons of plutonium.
160 LONG-TEAM DISPOSITION cility could be built; estimates provided to the committee (which are almost certainly optimistic) indicate that such facilities could be built for between $400 million and $1.2 billion, depending on their capacity. Siting, building, and li- censing such a facility would probably require a decade or more. Reactor and Institutional Options. Many variants of such a U.S. MOX- burning plan can be imagined, involving different facilities and different insti- tutional arrangements (such as a mix of government and private involvement). As noted earlier, if possible it would be desirable to use existing or partly completed LWRs for this mission, to avoid the delays and costs of building new facilities. Existing U.S. commercial nuclear reactors are owned and operated by private utilities. If these reactors were to be used for plutonium disposition, sev- eral institutional options suggest themselves: · provision of plutonium fuel to utilities by the government, at the same or lower cost as the utilities pay for equivalent low-enriched uranium fuel (the government absorbing the expected extra costs of fabricating plutonium fuel); · government acquisition of reactors, turning them into government-owned ~ . . . . . plutonium c ~lsposltlon sites; or · a mix of private and government roles in control and management of the sites. For example, the government might acquire the reactors and turn them into a federal site, managing them in partnership with private entities. The private entities would manage the production and sale of electricity, because the federal government is barred by the Atomic Energy Act from directly selling electricity from nuclear facilities on private markets. The private en- tities might provide all or part of the initial investment, reducing the up- front capital cost to the government. Given the international implications of an excess weapons plutonium dis- position program, and the need to set stringent standards for security and safe- guards, a government role is required. Moreover, the problem of gaining the necessary approvals and licenses for MOX reactor operations might become easier if the sites were federal facilities-either sites already owned and oper- ated by the government, or commercial reactors acquired and turned into fed- eral sites for the plutonium disposition mission. The following are a few of the most obvious specific candidates for this role. Operating Reactors at Palo Verde. Three System-80 LWRs are operational at the Palo Verde site in Arizona, owned by a private utility. As noted above, with license amendments these could operate with full-MOX cores without modification. If the utility agreed to participate, the federal government could cover any additional costs in using government-furnished MOX fuel and could provide the necessary new safeguards and security at the site, while the utility could otherwise continue to operate the reactors much as they are operated to- day. Additional financial incentives might be required to convince the utility to
LONG-TERM DISPOSITION 161 undertake the new political and licensing burdens involved. Using these reac- tors would limit handling of "fresh" plutonium and MOX fuel to two sites one where the MOX fuel would be fabricated (presumably a site within the nuclear weapons complex) and the Palo Verde reactor site. Utility and public reactions to this concept have not been explored. Partly Completed Reactors in Washington State. Two partly completed nuclear reactors exist in Washington State: Washington Nuclear Project (WNP) 3 is a System-80 reactor, 75 percent complete, in the western part of the state, roughly 150 miles from the Hanford nuclear-weapons complex reservation; WNP-1, 63 percent complete, is not a System-80 and would have to be modi- fied to handle a full core of MOX as its construction was completed, but it has the advantage of being physically located on the Hanford reservation. One or both of these reactors could be acquired, completed, and operated by the federal government (possibly in cooperation with a private entity) for the plutonium disposition mission. If the MOX fabrication capability at Hanford were used, this would have the significant advantage of confining all plutonium handling to two federal sites in the same state (or even a single large site, if Drily the WNP-1 facility on the Hanford reservation were used). A consortium of private companies has put forward a proposal for a government-private partnership to pursue this approaches Acquisition of Other Existing Facilities: If both the Palo Verde and the VVNP facilities were unavailable or faced insurmountable licensing or public approval difficulties, there are several other U.S. reactors that utilities may be willing to provide to the government, either because they were never completed i4 this concept, known as the "Isaiah Project," is being put forward by a team consisting of Battelle, Science Applications International Corporation, and Newport News. (Briefing for NAS Panel on Reactor-Related Options for Disposition of Weapons Plutonium, May 7, 1993.) In their proposal, the private consortium they would set up would acquire and complete the reactors at its expense (deeding ownership of the reactors to the government), and receive revenue to pay for debt service and profit. The government would pay for reactor operations, fuel fabrication, storage, and disposal, and provide a contractual guarantee of particular quantities of steam for electricity production. Advocates for this concept have emphasized the possibility that the private entity could borrow several billion dollars against the future revenues of the project, which could be provided to the government to finance other endeavors, such as assistance for plutonium disposition in Russia. This is misleading, however, as future costs assigned to the government in this concept would come to substantially more than the sums that could be borrowed. Hence, as with other approaches, the project would ultimately involve a net discounted present cost to the government, not a net discounted present value. Borrowing against future revenue, with the accompanying promise of large future government expenditures, would simply amount to deficit financing by other means. This point is equally applicable to other approaches involving private financing of initial capital costs in return for government promises of later subsidies. Another operating reactor, WNP-2 is also located on the Hanford reservation, and like WNP-1, could be modified to handle a full core of MOX fuel. This would require shutting down an operating reactor for modification, with the accompanying cost of lost revenue, and the utility that owns the reactor would have to be persuaded to allow its use for this purpose. This option, however, would have the significant advantage of providing two reactors and a fuel-fabrication facility on a single nuclear- weapc~ns complex site. The time and cost for modifying and licensing WNP-2 might turn out to be less than the time and cost of completing and licensing WNP-3.
162 LONG-TERM DISPOSITION or because their continued operation is becoming economically uncompeti- tive.is These could be acquired, modified for full-MOX cores, and used much as the WNP reactors might be. Principles for Institutional Arrangements. The specifics of such institu- tional arrangements require further study, but several basic principles suggest themselves: · As noted above, the government should have a strong role, to ensure that the approach fits with broader national policies relating to arms reduction and nonproliferation, that adequate security and safeguards are maintained, that any necessary openness to international inspection is maintained, and that appropriate ES&H standards are met. · The number of sites should be minimized, to consolidate monitoring and safeguards functions and reduce the risks of plutonium theft. · The sites should probably be federal facilities (either already owned by the government, or acquired for this purpose), to ease the task of gaining the necessary approvals and licenses and of maintaining the security and inter- national transparency mentioned above. · Any increase in government competition with private electricity generation should be minimized to the extent possible. · If private investment can genuinely reduce government costs and up-front federal capital investments, it should be encouraged. But assessments of such possibilities must include realistic appraisals of all likely future costs and revenues, and the financial risks of government commitments to future sub- sidies or operations. Approvals and Licenses. In addition to fuel fabrication, approvals and li- censes are important pacing factors. The United States initiated a licensing process for using MOX in LWRs in the 1970s (the Generic Environmental Statement for Mixed Oxide fuel, or GESMO), but this process was terminated when President Carter decided to end government support for the plutonium fuel cycle. Although there do not appear to be fundamental obstacles to licens- ing a small number of U.S. reactors to handle MOX, particularly if no reproc- essing is involved, it is likely to take the better part of a decade before the req uisite fuel fabrication and reactor sites are licensed and operational. Substantial public controversy would almost certainly attend siting and construction of a plutonium fuel fabrication facility, and the use of plutonium fuel in U.S. reactors. There are important open questions concerning the licensing process for the various plutonium disposition facilities. Currently, the Nuclear Regulatory Is By some estimates, there may be a dozen or more reactors in the United States that are in danger of being shut down well short of their design lives because utilities have other, more economical alternatives available. These reactors would be prime candidates for acquisition by the government for . . . . . . t :~e p utomum ( .lsposltlon mlsslon.
LONG-TERM DISPOSITION 163 Commission (NRC) regulates only civilian nuclear power plants. The Defense Nuclear Facilities Safety Board (DNFSB) was established by Congress to pro- vide a form of regulatory oversight for the Department of Energy (DOE) weap- ons facilities, but it is an advisory body and does not have regulatory power. If one or more nuclear plants for plutonium disposition were owned by DOE, the DNFSB could be asked to provide oversight. Nevertheless, it is virtually certain that any such facility would have to meet NRC safety standards, and the com- mittee believes this is desirable. Gaining approval by the DNFSB would probably take even longer than gaining NRC licenses, because the DNFSB staff is much smaller than the NRC's and has less regulatory experience. Moreover, DNFSB oversight might be more likely to be challenged in court. Licensing a MOX fabrication facility would also be time-consuming; it, too, might be done under either the NRC or the DNFSB. Under the National Environmental Policy Act (NEPA), Environmental Impact Statements (EISs) are likely to be required for several of the facilities, and the time required to prepare these and obtain approval for them would be substantial. Public approval in the areas near the relevant facilities will also be a criti- cal factor. Problems of public approval and licensing could be lessened somewhat if both the plutonium fuel fabrication facilities and the reactors handling MOX fuels were on federal sites. This is the main argument for building new reactors at existing DOE sites, rather than relying on existing civilian reactors. There is a good chance, however, that these problems could be addressed at some existing reactors, particularly if they were acquired as new federal sites. Chances for local public approval for the operation of FMEF for MOX fuel fabrication or the construction of new MOX facilities might be im- proved if the jobs associated with the fabrication plant and those that might be associated with reactor modification and operation were provided in the same area. Safeguards and Security. The discussion to this point has focused pri- marily on feasibility and timing. Another important criterion identified above is safeguards and security, enumerated under the "risks of handling." An agreed system of safeguards and security, as part of the overall regime for fissile mate- rial storage and management discussed in Chapters 4 and 5, should be adopted. Given the stringent security procedures and the low incidence of terrorism in the United States, risks during transportation are substantially lower in the United States than in Russia at the moment. The scale of transport required will depend to a great degree on the number of sites, and in particular on whether conversion of pits to oxides, fuel fabrication, and the relevant reactors would be located at the same site or at several widely dispersed locations. The number of sites at which this plutonium is handled, the number of shipments of pluto- nium, and their length should be minimized to the extent possible, to limit the risks of theft.
164 LONG-TERM DISPOSITION Once the plutonium is in the form of bulk oxide, rather than individually packaged pits, precise accounting to detect any diversion will become consid- erably more difficult. This will be a particular problem at the fuel fabrication facility, where the accounting system will need to have the capability for timely detection of diversion or theft of even a very small percentage of the facility's throughput. The IAEA and the EURATOM (European Community's Safe- guarding Agency) have been working for years (with assistance from the U.S. Los Alamos National Laboratory) to develop new techniques for safeguarding such large plutonium bulk-handling facilities because similar large facilities for civilian plutonium processing are scheduled to open soon in Europe and Japan. Nevertheless, some of these techniques are still in development, and it is doubt- ful that material accounting alone will be able to guarantee that diversion of enough plutonium to make a bomb could be detected within days. It will probably not be possible to achieve the stored weapons standard of accounting when dealing with complex, multistage processing of plutonium in bulk form. Therefore, in addition to stringent material accounting, there should be exten- sive containment, surveillance, and security measures to ensure that no pluto- nium leaves the site without authorization. Indirect Impact on Civilian Fuel Cycle Risks. As noted above, policy- makers considering plutonium disposition options should be aware that the use of U.S. weapons plutonium in U.S. LWRs could be seen as a significant change in U.S. policy, which has been not to pursue a plutonium fuel cycle. Such a shift could have an impact involving decisions on civil plutonium policies in Europe, Japan, and elsewhere. Cost. As noted earlier (see "The Value of Plutonium," Chapter 1, p. 24), the cost of this approach depends on a large number of assumptions concerning figures that are uncertain and also on how one conceptualizes the calculation. The required subsidy for using MOX fabricated from weapons plutonium rather than LEU in existing LWRs is likely to range from several hundred million to a billion dollars. If reactors had to be built, completed, or modified, or if the dif- ferences between LEU and MOX spent fuel involved higher disposal costs for MOX, those expenses would have to be added to this figure. Environment, Safety, and Health. With appropriate modifications, it should be possible to operate U.S. LWRs with full-MOX cores while meeting the same safety standards that pertain to LEU fuel. The plutonium processing necessary for this option (pit conversion and fuel fabrication) would inevitably result in wastes, risks of accident, and worker hazards. Careful design and the application of sufficient resources, however, should enable these facilities to comply with current regulatory standards. MOX operations have been demon |6 For a more detailed cost analysis of this option and other reactor-related options, see Management and Disposition of Excess Weapons Plutonium: Report of the Panel on Reactor- Related Options, op. Cit.
LONG-TERM DISPOSITION 165 strafed in Europe, but have not yet been undertaken in the U.S. regulatory environment.~7 The spent fuel resulting from this option would be similar in most respects to ordinary LEU spent fuel, but there are important differences. MOX spent fuel will contain more plutonium than typical spent fuel (raising potentially greater criticality concerns after eventual emplacement in a geologic repository) and will emit more heat for a longer time (which has an impact on the reposi- tory volume required to hold a given number of fuel assemblies). The possibil- ity that the somewhat different chemistry of the MOX spent fuel would affect long-term rates of release of radioactive materials in the repository would also have to be examined. This different spent fuel would have to be separately li- censed as an acceptable waste form for geologic disposal, meaning additional costs and potentially additional delays. Once these issues are addressed, how- ever, it should be possible to store and dispose of MOX spent fuel as safely as LEU spent fuel. If the reactors used for this purpose would have operated with LEU in any case, the total amount of spent fuel to be disposed of in a geologic repository would not be increased as a result of plutonium disposition; even if reactors were operated specifically for plutonium disposition, the total amount of added spent fuel would be a small fraction of the planned capacity of the first U.S. repository. The Spiking Option. To "spike" the plutonium more rapidly than it could be processed into spent fuel would require a larger fuel fabrication facility (implying a higher capital cost) and more frequent reactor shutdowns for re- fueling (implying more lost revenue). Expanded fuel storage capacities at the reactor sites would also be required, to handle the fuel between the time when it was spiked and when it was recycled into the reactor to finish burning it to spent fuel. Hence, the costs of the spent fuel option would increase significantly if spiking were used as a first step. In addition, the radioactive exposures that might be incurred by workers in reintroducing the spiked fuel into the reactor would require careful examination. In the committee's judgment, the security for the material that could be gained by this more rapid but less extensive irra- diation could be achieved more simply by providing appropriate security at the plutonium storage site; given its substantial costs, the spiking step on the path to the spent fuel option in LWRs is probably not worthwhile. Summary. Processing weapons plutonium to spent fuel in existing U.S. LVVRs is technically feasible. The time needed to provide fuel fabrication ca- pability and acquire the necessary approvals and licenses would probably be 8- 10 years or more. Given favorable safety reviews, the use of full-MOX cores ]7 For a more detailed discussion of the environment, health, and safety issues associated with the use of plutonium in LWRs and other types of reactors, see ibid. ax Like LEU spent fuel, this spent fuel would be stored for a period and then placed in a geologic repository. A U.S. repository is not expected to open before at least 2010, and that date remains highly uncertain.
166 LONG-TEAM DISPOSITION appears clearly preferable to one-third MOX cores. No insurmountable safe guards or ES&H obstacles appear to confront this option. The subsidy required to use plutonium rather than uranium in U.S. reactors would be between several hundred million and one billion dollars, not counting costs of reactor modifica- tions, approvals, or additional costs of spent fuel disposal. Advantages: Technically demonstrated; moderate cost; moderate timing; clearly meets the spent fuel standard. Disadvantages: Safeguards and security issues in plutonium handling and transport; likely public controversy over plutonium processing, fabrication, transport, and use; possible impact on other countries' civilian plutonium pro- grams contrary to existing U.S. plutonium fuel policies. Conclusion: This option is a leading contender for long-term plutonium disposition. Major Outstanding Issues: Although the use of MOX fuels in LWRs is technically demonstrated, further study of the following technical issues is required: · confirming the safety of System-80 reactors operating with full MOX cores, and investigating the possibility of modifying other existing LVVRs for full- MOX operation (including the specifics of the modifications that would be required, the likely shutdown time required, the cost of modification, and the likely licensing issues); · examining the capability of the Hanford FMEF facility for LWR fuel fabri- cation, including cost and schedule for bringing it on-line, capacity, and ability to meet current safeguards and ES&H requirements; · examining the cost and schedule for building new MOX fabrication facilities designed to meet safeguards, security, and ES&H requirements, for compari- son to the FMEF option; · examining the facilities, methods, costs, schedules, safeguards, and ES&H issues for large-scale processing of pits to oxide; · examining technical issues in adapting MOX operations to the U.S. regula- tory environment; · assessing the acceptability of disposition of spent MOX fuel in geologic repositories; · examining ES&H issues throughout the process, particularly in pit process- ing and fuel fabrication; and · examining safeguards issues, particularly the ability to adequately safeguard MOX fuel fabrication facilities processing several tons of weapons-grade plutonium per year. Further investigation of several institutional issues is also needed: · licensing MOX fabrication facilities and reactors operating with plutonium fuels, including 100 percent MOX cores; · addressing likely political opposition to plutonium fabrication and use
LONG-TERM DISPOSITION 167 · arrangements for ownership and management of the facilities; . arrangements for financing the operations, including the possibility of incor- porating some private-sector financing; · arrangements for safeguards and security, including international agree- ments in these areas; and · the likely magnitude of the political impact of U.S. use of weapons pluto- nium in reactors on the use of separated plutonium fuels in other countries. RUSSIAN PLUTONIUM ~ RUSSIAN LWRs The major differences in using Russian LWRs to process Russian excess weapons plutonium include much higher security risks in the disposition proc- ess, because of the current economic and political upheavals in the former Soviet Union; much lower availability of funds to finance the process; a smaller existing infrastructure of safe reactors; and different economic conditions, plu- tonium fuel policies, and licensing procedures. Of the Russian reactors operating or under active construction, probably only the 950-MWe VVER-1000 light-water reactors, which are similar to Western designs, are adequately safe and have adequate capacity to carry out the plutonium disposition mission. Although the VVER-1000 reactors do not meet international safety standards, the consensus of foreign experts is that with planned upgrades they will be adequately safe, and that the Russian gov- ernment will continue to operate them for the long term in any case. A sub- stantial international program is under way to upgrade their safety. It does not appear that the use of MOX fuel would significantly degrade (or improve) the safety of these facilities. Earlier VVER designs and even more the RBMK graphite-moderated reactor design (used in the ill-fated Chernobyl reactor) do not meet acceptable safety standards and should not be considered for this mis- sion; the Russian BN series fast reactors are discussed separately, below. Russia has seven VVER-1000 reactors in operation, though some officials of the Russian Ministry of Atomic Energy (MINATOM) believe that because of varying designs, only the four most recent of these should be considered safe candidates for plutonium use. Several other VVER-1000s are under construc- tion. Ten more operating VVER-1000s, and several additional facilities under construction, are located in Ukraine. The capability of VVER-1000s to process weapons plutonium should be similar to that of most U.S. LWRs. Indeed, the modifications required for a full-MOX core might not be as extensive as in the case of U.S. reactors, be- cause the neutron spectrum in these reactors is somewhat less energetic. None of the VVERs have yet operated with MOX fuel, however, and substantial safety analyses would be required. MINATOM officials acknowledge that studies of MOX in VVER-1000s are just beginning and do not yet include the possible use of weapons-grade
168 LONG-TEAM DISPOSITION plutonium.~9 Because of the delays in commercializing fast breeder reactors that would consume plutonium separated by reprocessing, all other major re- processing countries except Britain have decided to use plutonium as MOX in LWRs, to avoid the buildup of large stores of separated plutonium. Russia has not yet taken this route, preferring to save both military and civilian separated plutonium for eventual use in breeder reactors (see below). Russia already has some 25 tons of excess civilian separated plutonium, and more is building up every year, in addition to the excess military plutonium resulting from arms reductions. Some use of MOX in VVER-1000s is now being considered for the long term, however, during the transition to a breeder economy that MINATOM officials envision. Whether that transition will occur within the next several decades, and what will happen to the stored separated plutonium if it does not, remain controversial. If full-MOX cores proved acceptably safe, with enrichments of perhaps 5 percent plutonium in the fuel, two VVER-1000 reactors could transform 50 metric tons of weapons plutonium into spent fuel in 30 years.20 Each opera- tional VVER-1000 is scheduled to be shut down for roughly one year for safety improvements under the ongoing program of international safety assistance. With enough lead time for proper design and preparation, the modifications necessary to handle a full-MOX core could be made during this period, without substantially extending the length of the shutdown. Altematively, VVER-1000s scheduled for completion in the near future could be modified for this purpose as they are completed. The public versus private issues in Russia are somewhat simpler, since MINATOM runs both the nuclear weapons complex and the civilian nuclear reactor industry. But as noted above, U.S. or international financial assistance may well be required if long-term disposition of excess weapons plutonium in Russia is to be accomplished in the foreseeable future. Just as private invest- ment might help reduce up-front capital costs in the United States, private in- vestment or loans from international financial institutions such as the World Bank or the European Bank for Reconstruction and Development might help |9 Evgeniy Kudriavtsev of MINATOM, for example, reported to the IAEA in April 1993 that "no serious investigations on military plutonium utilization in reactors of the VVER-type have been conducted in Russia," though he indicated that a future facility for fabricating MOX fuel for VVER- 1000s is planned (see E. Kudriavtsev "Russian Prospects for Plutonium Accumulation and Utilization," unpublished paper presented to an IAEA meeting on problems of separated plutonium, April 1993). See also Yu. K. Bibilashvili and F. G. Reshetnikov, "Russia's Nuclear Fuel Cycle: An Industrial Perspective," IAEA Bulletin, Vol. 35, no. 3, 1993, and V.S. Kagramanyan, "Utilization of BN-800 Fast Reactors of Isolated Plutonium Being Accumulated in the Russian Federation," unpublished paper, April 1993. 20 If, on the other hand, these reactors were limited to one-third MOX fuel, at a relatively low enrichment of 2.5 percent, nine reactors would be required to accomplish the same task. Since there are only seven operational VVER-1000s in Russia, either completion of additional reactors or use of some reactors in Ukraine would then be required. Given the uncertainty and conflicts surrounding Ukraine's nuclear activities, however, it would be preferable not to involve Ukrainian reactors in the use of weapons-grade plutonium.
LONG-TERM DISPOSITION 169 finance the operation in Russia, reducing the "line-item" costs that would have to be borne by any single government. These institutions are already consider- ing helping Russia complete the VVER-1000 reactors under construction, to facilitate the shutdown of older unsafe reactors. Fuel Fabrication. As in the United States, the time at which such disposi- tion could begin would be paced by the availability of a MOX fuel fabrication facility. Although Russia has laboratory-scale MOX fabrication facilities, no production facility with the required capabilities is currently operational. A MOX fabrication facility with an intended capacity of about 100 metric tons of heavy metal per year- enough to feed four VVER 1000s using full- MOX cores (processing as many tons of plutonium annually as the percentage in the fuel) is reportedly roughly 50 percent complete at the Chelyabinsk-65 site. Completing the plant would require several years at a cost in the range of hundreds of millions of dollars. The standards of safeguards, security, and ES&H that this plant was designed to meet or could practicably be modified to meet-are unknown. Alternatively, a new MOX fabrication facility dedicated to the excess weapons plutonium disposition mission could be constructed. The German company Siemens has proposed using disarmament assistance to build a replica of the Siemens fabrication facility already built at Hanau (currently idle because of licensing disputes), which has a design capacity of 120 metric tons of heavy metal per year. Siemens estimates the cost of building such a facility in Russia at less than half a billion dollars, and believes that it could be accomplished within a few years. Similarly, the French state-owned company COGEMA has expressed interest in Participating in Providing MOX fabrication capability. -Aura _~v-~ _A _~_ ADA red -~-~r~ =~ all r- Approvals and Licenses. The political and institutional climate for pluto- nium use in Russia differs from that in the United States. In Russia, the gov- ernment and the nuclear industry (controlled by MINATOM) are committed to a closed fuel cycle, including plutonium fuels, emphasizing fast breeder reac- tors. MINATOM wishes to save the excess weapons plutonium for eventual use as start-up fuel for future breeder reactors. Others indicate a desire to sell the excess plutonium. All maintain that weapons plutonium has value that must be exploited. At the same time, the Russian public, after decades of government secrecy and the Chernobyl disaster, has become increasingly wary of all things nuclear, and distrustful of all government environment and safety assurances. Public resistance to plutonium use may therefore be significant. The regional and local authorities in Tomsk, for example (a major production site for weapons pluto- nium), have gathered sufficient strength in opposing the siting of a weapons plutonium storage facility there to call into question the viability of the plan. The regulatory agency that in principle is empowered to regulate nuclear facil- ity siting and licenses, GOSATOMNADZOR, is seeking its role in the new Russia, and its future powers and attitudes toward plutonium use are uncertain.
170 LONG-TERM DISPOSITION Thus, the time required to gain the required licenses and approvals in Russia is more uncertain than in the U. S. case, and could ultimately prove to be either longer or shorter. Safeguards and Security. The risks of theft in transporting and processing plutonium in Russia under present circumstances appear high. Indeed, some analysts have argued that continued storage of the plutonium under high secu- rity until the Russian political and economic situation had stabilized would pose fewer risks than the processing and transport involved in the MOX option. There are some important mitigating factors, however. As with the Han- ford facility in the United States, the unfinished MOX fabrication facility in Russia is at a major nuclear weapons facility. In addition, the pattern in build- ing the new VVER-1000 reactors has been to build several at a single site; at Balakovo, for example, there are four operating VVER-1000s, while another site has three. Thus, it might be possible to accomplish all processing of bunk plutonium at existing nuclear weapons complex sites, and all reactor use of plutonium fuel at one additional site. As in the U.S. case, all of the disposition steps should be subject to an agreed system of safeguards and security. Indirect Impact on Civilian Fuel Cycle Risks. Assistance for using MOX in Russian reactors would inevitably provide a boost to the plutonium fuel cycle in Russia. There might also be some political impact in other countries whose civilian plutonium programs are controversial. Russia also has some 25 tons of separated civilian plutonium waiting to be fabricated into fuel; some Russian officials and European analysts have sug- gested that they should fabricate this material into fuel before beginning the use of weapons plutonium, since civilian plutonium builds up radioactivity that makes it difficult to handle more quickly. Thus, disarmament assistance for construction of a MOX facility might in effect sponsor civilian plutonium use in Russia and commercial competition for MOX fabricators in Europe. Cost. Russian costs are uncertain, and no detailed analysis is possible with the information available. It is clear, however, that Russia has an overcapacity of low-cost LEU available for fueling its thermal reactors, which it is trying to market in the West to earn hard currency. It is also clear that significant up- front capital would be required to provide requisite plutonium fuel fabrication capability and to modify reactors to handle full-MOX cores. Therefore, substi- tuting weapons plutonium for uranium in Russian LWRs would require a sig- nificant subsidy; the size of the subsidy would probably be in the range of hun dreds of millions of dollars. ES&M. To a large extent, the ES&H impact of plutonium disposition in Russian reactors would depend on the resources applied to mitigate these im- pacts and the standards set. Standards for ES&H protection in the former Soviet Union were low, and the resulting legacy of environmental devastation is
LONG-TERM DISPOSITION 171 now becoming clear. New ES&H policies are evolving in Russia, with uncer- tain prospects. Summary. Processing weapons plutonium in Russian LWRs, operating and nearly completed, appears technically feasible. The time required to pro- vide fuel fabrication capability and acquire the necessary approvals and licenses is highly uncertain. If safety reviews are favorable, the use of full-MOX cores appears clearly preferable to one-third MOX cores. The risks of theft or diver- sion of materials during disposition would be worrisome, given the current up- heavals in Russia. ES&H issues are difficult to address in detail, given the evolving state of Russian standards. Similarly, costs are difficult to estimate; some subsidy to displace uranium fuel, which is currently very cheap in Russia, would be required. Advantages: Technically feasible; moderate cost; moderate timing; meets the spent fuel standard. Disadvantages: Major safeguards and security issues in plutonium han- dling and transport; supports infrastructure for civilian plutonium fuel cycle in Russia; possible impact on other countries' civilian plutonium programs con- trary to U.S. fuel cycle policies. Conclusion: This option is a leading contender for long-term plutonium . . . disposition. Major Outstanding Issues: The technical issues involved in this option are similar to those involved in the use of U.S. LWRs. Further examination is needed of: · modifications required to ensure the safety of VVER-1000 reactors; · the safety of operating VVER-1000 reactors with full-MOX cores and mod- erately high plutonium loadings, including the specifics of the modifications that would be required, the likely shutdown time required to make those modifications, the cost of modification, and the likely licensing issues involved; the capability of the unfinished Chelyabinsk MOX facility for LWR fuel fabrication, including cost and schedule for bringing it on-line, capacity, and ability to meet current safeguards and ES&H requirements; · the cost, schedule, and capabilities of new MOX fabrication facilities, rela- tive to the Chelyabinsk option; and · issues, including ES&H and safeguards, concerning processing of pits to oxide. . The institutional issues are also similar to those in the United States, ex- cept that much greater safeguards risks and political and regulatory uncertain- ties are involved. Further study is needed of: · arrangements to provide adequate safeguards and security in the current cir cumstances in Russia, including international agreements in these areas;
172 LONG-TERM DISPOSITION · licensing and gaining local approval for the operations required in the evolving regulatory and political environment in Russia; · arrangements for financing the operations, including the possibility of partial financing through disarmament assistance and loans from international fi- nancial institutions; and · the likely magnitude of political impact of assistance for weapons-plutonium use on the use of separated plutonium fuels in other countries. CANADIAN CANDU REACTORS Commercial heavy-water-moderated reactors in Canada, known as CANI)U reactors (for Canadian deuterium-uranium), appear to be capable, without physical modification, of handling 100 percent MOX cores. As in the LWR case, favorable regulatory review of the safety of their operation in this mode would be required. This option appears technically and economically feasible for either U.S. or Russian excess weapons plutonium, but major politi- cal questions remain open. The current standard CANDU design could transform 50 metric tons of weapons plutonium into spent fuel in roughly 30 to 100 reactor-years of opera- tion, depending on the initial enrichment of the fuel.2i Canada has 20 CANDU reactors totaling about 14 GWe (46 thermal gigawatts; GWt); a number of these are at sites with as many as eight reactors at a single location. All the pacing elements for plutonium disposition based on existing CANDU reactors would be the same as those for using U.S. LWEs (fuel fabrication, licenses, the num- ber of reactors, the enrichment and burnup of the fuel), except that there would be the added complication and uncertainty of seeking U.S.-Canadian agreement. Compared to the use of U.S. LWRs, the use of CANDU reactors has both advantages and disadvantages. Advantages include: Fewer Modifications for Plutonium Use: In normal CANDU operations with natural uranium fuel, more than half of the energy is provided by fission- ing plutonium produced in the fuel as the reactor operates. As a result, adding plutonium to the initial fuel would represent a smaller change in the physics of the reactor core than in the case of LWRs. Moreover, the structure of the CANDU reactors allows plenty of space for added controls, and additional neu- tron absorbers could be dissolved in the heavy-water moderator used in the re 2) A CANDU-6 reactor, with a capacity of 2,125 Mwt, operating at a capacity factor of 90 percent and an average fuel burnup of 16,000 would process 524 kilograms of plutonium per year if the initial plutonium content in the fuel were 1.2 percent (corresponding to amount required to provide die maximum fuel life the reactor manufacturer estimates current fuel designs could sustain without further development and testing). It could process more than 2,000 kilograms of plutonium per year if the initial plutonium content were 4.6 percent (the maximum enrichment the manufacturer estimates could be accommodated in existing CANDUS without modifications requiring some development). These rates correspond to 95 and 25 reactor-years, respectively, to process 50 tons of weapons plutonium.
LONG-TERM DISPOSITION 173 actors. Thus, relatively few physical modifications would be required to handle substantial quantities of plutonium in CANDU reactors. Simplified Fuel Fabrication: CANDU fuel is produced in smaller and simpler units than those typical of LWRs, potentially reducing the fabrication cost, which is a substantial fraction of the total cost of MOX use. No Reactor Shutdown Required for Spiking: CANDU reactors are de- signed to be refueled without being shut down. Thus, although the spiking ap- proach would still require added capital expenditures for a larger fuel fabrica- tion facility, it would not decrease revenue as a result of reactor downtime for refueling. The CANDU option also has important disadvantages: Uncertain Canadian Acceptance: The use of existing CANDUs would have to be approved by the Canadian government, the reactor operators (primarily the Ontario Hydro utility), and the relevant regulators (the Atomic Energy Control Board). Atomic Energy of Canada, Limited (AECL), the gov- emment-owned designer of the CANDU systems, appears to support this concept, and the Canadian government has reportedly suggested to U.S. repre- sentatives that the two countries form an expert group to explore the idea. But further discussions between the U.S. and Canadian governments would be re- quired before it could be determined whether this approach had enough politi- cal support to be a practical option. Canada has previously avoided using either enriched uranium or plutonium fuels in CANDU reactors and might reject this plutonium use option as well. Yet Canada has also traditionally played an ac- tive role in disarmament; playing a central role in disposition of materials re- sulting from nuclear arms reductions might well be appealing enough to over- come the resistance to use of weapons materials. Canadian public acceptance is also an open question. Large-Scale International Plutonium Transport: The distances over which plutonium would have to be transported to be burned in CANDU reactors would be significantly greater than those in using U.S. or Russian LWRs for disposition of those countries' plutonium, even if all the CANDU reactors in- volved were at a single site. The attendant controversies and risks of theft would be correspondingly greater. Possibly more important in political terms than sheer distances is the need for the material to be shipped across interna- tional borders, to a non-nuclear-weapon state. Lower Radioactivity and Smaller Isotopic Changes: Because of the rela- tively short burnups that can be achieved with current fuel designs in CANDU reactors (even if the fuel were enriched with plutonium), the resulting spent fuel would be somewhat less radioactive than spent fuel from an LWR, and the isotopic composition of the plutonium in it would remain closer to that of weapons plutonium. Safeguards Issues of On-Line Refueling: Fuel can be removed from CANDU reactors at any time without shutting down the reactor, and the fuel
174 LONG-TERM DISPOSITION elements are substantially smaller and more portable than is the case for LWRs. Therefore, CANDUs require more intensive safeguarding than do LVVRs. For fuel containing more plutonium, still more intensive safeguarding would be needed. Both CANDU reactors and the fresh MOX fuel in store at either an LWR or a CANDU require continuous safeguarding in any case, however. Moreover, the task of accounting for and securing complete fuel assemblies for either a CANDU or an LWR is substantially easier than that of accounting for bulk plutonium at a MOX fabrication plant. Therefore, the net additional secu- rity risks of using CANDU reactors for this mission compared to using LVVRs would be relatively small. Fuel Fabrication. Like the United States, Canada has no MOX fuel fabri- cation capacity. Fabricating MOX fuel for CANDUs at the Hanford FMEF fa- cility would be the most expeditious approach, with the same caveats as in the LWR case. The fabrication capacity needed to process 50 tons of excess weap- ons plutonium in a 25-year campaign in a single reactor using fuel containing 4.6 percent plutonium (the maximum that the manufacturer believes can be used without substantial changes to the reactors) would be 44 metric tons of heavy metal per year, which is within the capability envisioned for FMEF. Spiking all the material in a few years before burning it to spent fuel would require a fuel fabrication capacity substantially larger than that provided by FMEF. Approvals and Licenses. Gaining approval of the various Canadian insti- tutions and the Canadian public would be a major hurdle for the CANDU op- tion. Licensing reactor operations with plutonium would probably be a less dif- ficult issue than securing agreement on the basic approach. Licensing proce- dures and standards for plutonium use in Canada are different from those used by the U.S. Nuclear Regulatory Commission. Safeguards and Recoverability. The safeguards concerns regarding fuel fabrication are similar for LWRs and CANDUs. Because of the need to trans- port plutonium over longer distances, transport risks would be somewhat greater for CANDUs, and because of the reactor's on-line refueling capability and the portability of the fuel elements, the risks of theft or diversion of fabri- cated fuel from the reactor could be somewhat greater as well. Both of these risks could be reduced to very low levels with the application of sufficient resources. Indirect Impact on Civilian Fuel Cycle Risks. The political impact of this approach would be more complex than in the U.S. LWR case. On the one hand, by providing excess plutonium free of charge to another nation, the United States would be demonstrating that it saw no economic value in the ma- terial and was encouraging its use in reactors only as an arms control measure. On the other hand, the United States would still be encouraging use of pluto
LONG-TERM DISPOSITION 175 nium in reactors on a scale wider than would otherwise be the case in a non- nuclear-weapon state. Cost. The cost of this option is difficult to estimate since no one has yet at- tempted to fabricate MOX fuel for CANDU reactors on any significant scale. On the one hand, an argument can be made that the subsidy required would be less than in the LWR MOX case, because (1) the fuel is simpler and probably cheaper to fabricate; and (2) the MOX fuel would have a higher energy content (and hence a longer fuel life) than the natural uranium fuel that CANDU reac- tors normally use, so the increased per-kilogram cost of fabricating the MOX fuel would be compensated, in whole or in part, by the reduced amount of fuel to be fabricated. On the other hand, the subsidy required might also be higher than in the LWR case because the amount of natural uranium CANDU fuel that each kilogram of MOX would substitute for (whose cost would be subtracted from the MOX cost in calculating the subsidy required) would be more than $1,000 cheaper than the LEU LVVR fuel that a kilogram of MOX could substi- tute for.22 Further study would be required to clarify these cost issues. Environment, Safety, and Health. Use of plutonium in CANDU reactors raises the same general concerns as those described for LWRs. Summary. Processing weapons plutonium to spent fuel in existing CANDU reactors appears technically feasible. Canadian approval would be required and is uncertain. Once agreement on the basic approach had been reached, providing fuel fabrication capability and acquiring the necessary ap- provals and licenses would probably take the better part of a decade, as with LWRs. No insurmountable safeguards or ES&H obstacles are apparent, though the on-line refueling used in CANDU reactors would require intensive safe- guarding. The subsidy required to substitute MOX fuel for uranium is uncertain and could be either less or more than in the LWR case. Advantages: Technically feasible; moderate cost; moderate timing; meets the spent fuel standard. Disadvantages: Uncertainty of Canadian acceptance; potential safeguards and security issues resulting from required international transport and on-line refueling of CANDU reactors; possible impact on other countries' civilian plu- tonium programs contrary to existing U.S. plutonium fuel policies. Conclusion: Using plutonium as MOX in existing CANDU reactors is a leading contender for long-term plutonium disposition. 22 Whatever might be achieved by using a fuel enriched in plutonium, it is likely that an even better economic result could be achieved by using enriched uranium fuels, which would not involve the extra handling costs of plutonium. But at the outset of its reactor program, the Canadian government made a political decision not to pursue reactor fuel cycles involving technologies, such as enrichment, that could be used to make weapons-grade materials. The use of MOX fuels could be perceived as contravening that policy. Thus, the subsidy for use of plutonium in the case of CANDUs arises in comparison to a fuel cycle that is currently less than optimally efficient, given current fuel prices.
176 LONG-TERM DISPOSITION Major Outstanding Issues: Major technical issues outstanding for CANDU reactors are largely identical to those described above for U.S. LWRs. The institutional questions are also similar to those relating to U.S. LWRs, except for the questions of Canadian agreement to this option, including the specific international arrangements for shipping weapons plutonium to Canada. The different Canadian regulatory environment requires further examination. SUBSTITUTION FOR CIVILIAN PLUTONIUM IN EUROPE AND JAPAN Under established civilian plutonium fuel programs, commercial reactors in Europe and Japan are scheduled to process more than 100 tons of civilian plutonium over the next decade. Plutonium storage and transport arrangements, fuel fabrication capabilities, and reactors licensed to handle plutonium for this task already exist or are planned.23 One possibility for long-term disposition of excess weapons plutonium, therefore, is to substitute this weapons material for civilian plutonium. Pits would be processed to plutonium oxide in their country of origin, and the resulting oxide shipped to Europe or Japan for fabrication and use.24 That initial processing and shipment step would be the only aspect of plutonium handling beyond that already planned with the important caveat that all these facilities would now be using weapons-grade, rather than reactor- grade, plutonium. From the point of view of civilian nuclear energy production, the weapons plutonium would be less radioactive (and therefore easier to fabn- cate) and have slightly higher energy content than the reactor-grade material it would replace, but would change the physics of the reactor somewhat, possibly requiring some modest adjustments. What would happen to the displaced civilian plutonium? Three main pos- sibilities exist: one is to expand MOX operations in these countnes, involving more reactors and fabrication facilities than those currently planned, so as to process both the civilian and the excess weapons plutonium. The advantages of this approach over using the plutonium in the country from whose weapons it came do not appear compelling, since similar fabrication facilities and reactors would have to be licensed and built. Another possibility is to continue reprocessing and MOX use as planned, and to store the separated reactor-grade plutonium displaced by the weapons plutonium. The net result would be to convert an excess stock of separated 23 As of 1993, eight LWRs in France, seven in Germany, and two in Switzerland were using MOX fuel, and more were licensed to do so. Belgium and Japan plan to begin loading MOX fuel in commercial reactors later in the decade. 24 Alternatively, rather than making use of both the reactors and the MOX fabrication capabilities existing or planned in Europe and Japan, one might make use of only the MOX fabrication capabilities shipping the resulting fuel back lo the country of origin. In that case, however, another round of international shipments of plutonium would be required; and since these existing and planned MOX fabrication facilities will have a hard time handling all the projected civilian plutonium, adding weapons plutonium would mean that separated civil plutonium would build up. some of the reactors in Europe and Japan currently scheduled lo use plutonium fuels would not receive the products of these fabrication facilities as expected and would have to switch back to uranium fuels.
LONG-TERM DISPOSITION 177 weapons-grade plutonium to an excess stock of separated reactor-grade pluto- nium of roughly equal size-a step the committee concludes to be of too limited benefit to justify the complications of the required international agreements and the risks of the required international transport. The third possibility is to defer reprocessing until existing excess stocks of separated plutonium (both weapons-grade and reactor-grade) are consumed. Reprocessing plants would be kept in cold standby until then.25 This would require complex international agreements altering a web of existing contracts and spent fuel management policies. Nevertheless, this approach appears con- siderably more promising, since it could consume both the projected surplus of weapons plutonium and the projected surplus of separated civilian plutonium, without necessarily undermining long-term plutonium fuel cycle plans in any fundamental way.26 If the necessary agreements could be reached expeditiously, this would be by far the most rapid reactor option, since the pacing steps of building new fabrication capacity and licensing the various facilities would be avoided; as noted, more than 100 tons of plutonium are expected to be processed in this way over the next decade in any case, so it would be technically possible to process the entire stock of U.S. and Russian excess weapons plutonium during that period. Reaching the necessary agreements could involve extended and unpredictable delays, however. Approvals and Licenses. Gaining agreement to alter the international ar- rangements and contracts that currently govern reprocessing and plutonium fuel programs would take considerable effort. France and Britain share much of the world market for commercial reprocessing and have just completed multi- billion-dollar investments in new facilities. Any proposal to defer reprocessing for an extended period would be seen as a threat to these businesses. Even sub- stantial financial compensation might not be sufficient to overcome such objec- tions. A multinational negotiation would be required in a forum not yet defined If some relevant countries were interested in pursuing this option but oth- ers were not, the substitution of weapons plutonium for civilian separated plu- tonium might be only partial. Britain, for example, might agree to defer opera- tion of its Thermal Oxide Reprocessing Plant (THORP) and fulfill its contracts 25 An important part of this problem is that a substantial amount of the plutonium slated to be used as fuel in civilian reactors over the next decade has already been separated some 60 tons in Europe and Japan as of the end of 1992. Thus, decisions would have to be made as to whether the weapons stock (which poses a somewhat greater proliferation risk) or the civilian stock (which will build up radioactivity more quickly in storage, requiring further processing if storage is prolonged) should be used first. 26 The Natural Resources Defense Council, which first suggested this substitution approach, has also argued for an agreement to permanently shut down civilian reprocessing. Such a permanent shutdown, however, is by no means essential to the basic concept, and even if agreement on such a far- reaching step could be reached, doing so would almost certainly be time-consuming, delaying implementation of the option. It is also possible that the parties involved in existing reprocessing contracts might themselves agree, during the period of deferral, to terminate these contracts rather than merely delaying them, with appropriate financial compensation.
178 LONG-TERM DISPOSITION with weapons plutonium instead, even if France continued with its reprocessing operations as planned. By the time such measures could be seriously consid- ered, however, it is likely that THORP will already be operating. If reprocessing were deferred for an extended period, more spent fuel stor- age would be required. From the point of view of utility owners of nuclear reac- tors in countries such as Germany and Japan, the opportunity to ship their spent fuel elsewhere "out of sight, out of mind"-is one of the primary advantages of reprocessing, and they might be very reluctant to agree (and might be legally constrained not to agree) to an additional decade's worth of spent fuel simply building up at their reactor sites. It is an open question whether the public in France and Britain would accept the alternative of highly radioactive spent fuel continuing to be shipped from abroad to reprocessing sites in their countries for storage, with no reprocessing planned for years to come. It is also uncertain whether the Russian government would accept this ap- proach since, like the HEU deal (which has raised some controversy in Russia), it would involve shipping large quantities of a key strategic material abroad. Again, financial compensation-provided as a security subsidy by the interna- tional community-would probably be required. The international controversy provoked by the recent shipment of 1.7 tons of reactor-grade plutonium oxide from France to Japan suggests the political difficulties faced by the much larger shipments required for the plutonium dis- position mission. To displace civilian plutonium to be used in Europe with Russian excess weapons plutonium, however, only overland transportation would be required. Overland plutonium shipments in Europe are common and relatively noncontroversial, and the association with arms reduction should also help reduce public criticism. In addition, shipment of large quantities of weapons-grade plutonium, rather than merely reactor-grade plutonium, to non-nuclear-weapon states such as Japan and Germany would almost certainly arouse controversy in those countries and in neighboring states. Safeguards and Security. Since the weapons plutonium would displace separated plutonium operations that would take place in any case, the net addi- tional safeguards issues involved in this option are less substantial than those in other cases. The net additional risks would come from the pit processing re- quired for all options; the large-scale international shipment of plutonium, cen- tral to this option; and the difference in proliferation risk involved in the shift from reactor-grade to weapons-grade plutonium. The risks involved in the large-scale international transport of plutonium required in this option are difficult to judge and depend on the resources ap- plied to reducing them. Once the weapons plutonium arrived in Europe, the risks of diversion or theft during processing and use would be substantially lower than if the material were used in Russia, given the greater social and economic turmoil now taking place there. The need for an agreed, international
LONG-TERM DISPOSITION 179 approach to safeguards and security is even more obvious here than it is in other cases. Indirect Impact on Civilian Fuel Cycle Risks. This "substitution" option sends a variety of signals. Parties interested in maintaining the momentum of commercial reprocessing might view the approach as a fundamental threat to the plutonium fuel cycle (particularly if the option of shutting down civilian reprocessing entirely is considered). Critics of the use of separated plutonium fuels might see an approach that tied disposition of weapons plutonium to con- tinued large-scale MOX operations as irrevocably confirming MOX plans that might otherwise be canceled, and as conferring the political legitimacy of dis- armament on MOX operations. Cost. In this option, a variety of parties would probably demand financial compensation for the materials used or the disruption of previous plans. Russia would probably insist on financial compensation for plutonium used abroad in this way, making it effectively a plutonium purchase arrangement similar to the LIEU deal. The reprocessors whose contracts would be delayed or canceled would probably also require compensation, perhaps by means of continued payments on the existing contracts (since those who were to receive plutonium would still be receiving plutonium without reprocessing). Delaying reprocess- ing of a decade's worth of spent fuel would require additional spent fuel storage at either reactor or reprocessing sites. All told, the subsidy required to finan- cially compensate all the relevant parties might be comparable to the subsidy required to burn plutonium in LWRs that would otherwise burn LEU, discussed above.27 ES&M. As with safeguards and security, the net additional ES&H burden would probably be smaller than that for other options, since the weapons plu- tonium would displace commercial plutonium that would be used in any case. As with other options, there would be some ES&H risks involved in the proc- essing of the pits to oxide, and steps to minimize the risks of accidents during the international shipment would be required. But there might also be some ES&H benefits: workers at MOX fabrication facilities, for example, would be exposed to lower radiation doses from weapons plutonium than they would have been from reactor-grade plutonium, and adding a decade or more to the time spent fuel would be stored prior to reprocessing would reduce the radioac- tivity of the fuel when it was eventually processed. 27 Under a financing scheme put forward by the Natural Resources Defense Council, money from MOX-burning electric utilities that would have been paid, under existing reprocessing contracts, for reprocessed civilian plutonium would instead be divided between (1) paying a fair rate of return to the investors in commercial reprocessing plants that would not be operated and (2) paying Russia for its weapons plutonium. The option, in this concept, would not require subsidies beyond those already being paid for reprocessing and MOX use. Additional subsidies would probably be required, however, for purposes such as compensating the reprocessing workers who would be laid off, setting up the required international arrangements for management and transport, additional spent fuel storage, and the like.
180 LONG-TERM DISPOSITION Summary. Substituting excess weapons plutonium for reactor-grade plu- tonium in existing civilian plutonium fuel programs, with an associated delay in production of additional separated civil plutonium, would be the quickest practical means of disposition for excess weapons plutonium if the complex international agreements required could be achieved, but that is very much an open question. More than 100 tons of weapons plutonium could in principle be processed in this way over the next decade, and over a longer period the accu- mulated excess of civilian plutonium could be consumed as well. The large- scale international transport of separated weapons-grade plutonium required in this option would be controversial and would raise risks of theft. The subsidy required to compensate the various parties is difficult to estimate, but might be comparable to the other LWR options. Advantages: Potentially quick; moderate cost; meets the spent fuel stan- dard; does not lead to significant net expansion in global handling of separated plutonium; could potentially eliminate both the excess weapons plutonium and the projected excess civilian plutonium. Disadvantages: Complex international agreements required; reaching nec- essary agreements could involve major delays; large-scale international pluto- nium shipments required; could reinforce programs for the use of separated plutonium that might otherwise be canceled or scaled back. Conclusion: Substituting weapons plutonium for civilian plutonium in planned plutonium fuel programs, with an associated delay in production of additional separated civilian plutonium, is a possibility for long-term plutonium disposition, but is less attractive than the reactor alternatives previously discussed. Major Outstanding Issues: In this case, the only technical issues are those in the initial stages (including processing pits to oxide and providing adequate security for the international plutonium transport) and some relatively minor reactor and fuel fabrication issues related to the shift from reactor-grade to weapons-grade plutonium. The institutional issues include: · the acceptability of the option to the various parties, including those in Russia, the United States, France, Britain, Germany, and Japan, among others; · the specifics of arrangements for deferral of reprocessing and increases in spent fuel storage; · the specifics of the international arrangements for the large-scale transporta- tion of plutonium required, and means to address public acceptance of such transport; · arrangements for safeguards and security throughout the process, including the initial transport; · financial compensation, both for the parties providing the plutonium and for the parties whose existing plans would be disrupted; and
LONG-TEAM DISPOSITION 181 · the degree to which such an arrangement might perpetuate programs involv- ing the widespread use of separated plutonium fuels that might otherwise be canceled or scaled back. OTHER OPTIONS INVOLVING PLUTONIUM TRANSFERS The CANDU option and the option just described require shipment of weapons plutonium to other countries. A variety of similar options could be envisioned. For example, Russian excess weapons plutonium might be shipped to the United States for disposition there, either in LWRs, by vitrification, or by other means; Russian plutonium might be shipped to Canada for use in CANDUs; or U.S. plutonium, like Russian plutonium, might be shipped to Europe and Japan to substitute for civilian plutonium there. The use of Russian excess plutonium in U.S. or Canadian reactors would have the advantage that the risks of diversion or theft would probably be lower than they would be if it were fabricated into fuel and used in Russia. The risks of theft involved in the transatlantic shipment could be reduced to low levels if naval forces helped protect the shipment, but the controversies involved would be substantial. The United States would not only have to pay a subsidy for the use of plutonium in reactors, but would probably have to pay Russia for the plutonium as well. In general, this is not likely to be politically attractive in the United States (where it might be seen as shipping a big problem from Russia to the United States) or in Russia (where it might be seen as shipping away a na- tional patrimony). It would seem ironic to ship plutonium from a nation that viewed it as a valuable asset to one that did not. Because the purchase in this case would be strictly bilateral rather than multilateral, however, it might be negotiated more quickly than the substitution for civilian plutonium described above; the basic arrangements would closely parallel the nearly complete HEU deal. The CANDU option would be comparably attractive if Canada were inter- ested in pursuing it. In the most likely approach, the plutonium would be pur- chased from Russia by the United States, fabricated into fuel in the United States, and would only then be transferred to Canada. The committee rejects the reverse operation shipping U.S. weapons plu- tonium to Russia for use in its reactors. The security and safeguards problem would be increased, the reactors that would use the material would be less safe, and many in the United States would argue that shipping more plutonium to Russia would give Russia a greater potential breakout capability should the government there change in the future. The option of incorporating U.S. weapons plutonium in a substitution for civilian plutonium in existing plutonium fuel programs in Europe and Japan, however, should be kept open, though all the caveats described above would apply. The primary additional liabilities of this approach (compared to using only the Russian excess weapons plutonium in this way) would be that transat- lantic shipment would be required, and that the delay and disruption imposed
182 LONG-TERM DISPOSITION on existing plutonium programs in Europe would be greater. As with the use of Russian plutonium, this would involve shipping weapons-grade plutonium to a number of non-nuclear-weapon states whose plutonium programs are already arousing concern. Moreover, there would not be the motivation, present in the Russian case, of removing the material from an area of current economic and political instability that increases the risks of theft. EXISTING FAST REACTORS FOR THE SPENT FUEL OPTION Experimental and prototype liquid-metal reactors (LMRs) exist in a few countries. LMRs (also known as "fast" reactors because of the greater energy of the neutrons in their reactor cores) were originally designed to "breed" more plutonium than they consume. Today, however, their potential role in consum- ing plutonium and other long-lived actinides and fission products as part of a waste management approach known as "actinide recycle" is also being explored. These reactors have generally been designed to test concepts for re- peated reprocessing and reuse of plutonium, an approach applicable to the elimination option (discussed below) but not to the spent fuel option. However, if operated without reprocessing, on a once-through cycle, existing fast reactors offer some near-term capacity for transforming weapons plutonium into spent fuel, particularly as many of them have been designed to use plutonium fuel. If operated as "breeders" as originally designed, these reactors would produce more plutonium than would be fissioned (also true in the case of LWRs with one-third MOX cores), but this plutonium would be embedded in the highly radioactive spent fuel and "blanket" material from the reactor. Of the few existing LMRs, however, even fewer are now in operation, and some face substantial technical or safety problems: · In the United States, the experimental breeder reactor (EBR-II) has far too little capacity to play a significant role. The Fast Flux Test Facility (FFTF) reactor, currently on standby and requiring 18 months or more to begin opera- tions, has sufficient capacity to carry out the initial spiking mission (requiring perhaps 25 years to process 50 tons of plutonium), but its life would then be largely consumed, and some additional facility would be required to carry out the spent fuel option. Moreover, this facility produces no electricity and thus no revenue. Hence the committee rejects this approach. · In the former Soviet Union, there are two operating fast reactors of sig- nificant size, the BN-350 in Kazakhstan and the BN-600 in Russia. In princi- ple, these reactors have sufficient capacity to transform roughly 1 ton of pluto- nium per year into spent fuel. There are questions about these reactors' safety (particularly in the case of the older BN-350), and they certainly cannot operate long enough for disposition of 50 tons of plutonium. Moreover, the cores of these reactors were designed for uranium fuel, and although some tests of a few plutonium fuel assemblies have been carried out in these facilities (including some with weapons-grade plutonium), MINATOM officials report that "a
LONG-TEAM DISPOSITION 183 complete conversion of these reactors to MOX fuel is not possible owing to their design and physical features."28 Russian concepts for construction of larger BN-800 reactors are discussed in the next section. · In France, there are two fast reactors, the expenmental-scale Phenix (233 MWe) and the commercial-scale Superphenix (1,200 MWe). Both are currently shut down, in part because of unexplained changes in the rate of the nuclear chain reaction in the core of Phenix. Superphenix has operated only intermit- tently and has now been shut down for so long that it has lost its license, but a relicensing process is under way. If it could operate safely with greater avail- ability than in the past, Superphenix could, by itself, convert 50 tons of excess plutonium to spent fuel in 20 years. However, Superphenix's past record gives little basis for confidence in future performance, and shipping weapons plutonium to this facility does not appear to have any major advantages over the more general substitution approach described above. Britain and Japan also have fast reactors either operational or soon to be, but these are too small (250 and 280 MWe, respectively) to be of significant value for the spent fuel option. In short, the use of existing fast reactors should not be pursued further as a major option for disposition of excess weapons plutonium. OTHER EXISTING REACTORS There are a variety of other existing reactors that might be used to process weapons plutonium. These include, among others, the plutonium production reactors in the United States and Russia, graphite-moderated reactors, gas- cooled reactors, and a variety of research reactors. None of these appear to offer any significant advantages compared to the options described above, and most appear to have major disadvantages in the areas of cost, safety, or capacity.29 The committee does not believe that any of these other existing reactors merits further consideration for the plutonium disposition mission. CONSTRUCTION OF EVOLUTIONARY OR ADVANCED REACTORS FOR THE SPENT FUEL OPTION If licensing and public acceptance issues facing existing reactors prove in- sunnountable, a plausible but more costly approach would be to build one or more new reactors, probably on a government-owned site. Such new reactors could be of established designs or evolutionary or advanced designs; a variety of different reactor types have been proposed for this mission.30 Licensing and 28 See Yu. K. Bibilashvili and F.G. Reshetnikov, "Russia's Nuclear Fuel Cycle: An Industrial Perspective," IAEA Bulletin, Vol. 35, no. 3, 1993, and Kudriavtsev, op. cit. 29 Even Japan's Fugen heavy-water-moderated reactor, which has been using plutonium fuels for years, is not suitable because its capacity (557 MWt, 165 MWe) is far too small for it to play a major part in the disposition of weapons plutonium. 30 For a general assessment of nuclear power approaches, see National Research Council (op. cit.). For assessments of several advanced reactor concepts for the plutonium disposition mission, see DOE, Plutonium Disposition Study, op. cit.; and Omberg and Walter, op. cit.
184 LONG-TERM DISPOSITION acceptance problems may of course be faced by new reactors built on a govern- ment site as well, but these may be less than those that might face the use of existing facilities. Advanced Light-Water Reactors (ALWRs). A number of advanced light-water reactors (ALWRs) are being developed in the United States and overseas, to meet future nuclear power needs. Their goal is to reduce cost and improve safety compared to previous LWR designs. Some are evolutionary ap- proaches conceptually similar to existing designs; others would make a greater departure from existing designs in order to emphasize the concept of passive safety. The System-80+ reactor developed by ABB-Combustion Engineering, a follow-on to the System-80, is designed for a full core of MOX fuel; other de- signs could be modified to handle full-MOX cores. Some of these designs, in- cluding the System-80+, are well along in the process of design review by the Nuclear Regulatory Commission. Although these designs may have significant advantages for power production, they would not process plutonium any faster, per unit of power produced, than existing reactors. Modular High-Temperature Gas-Cooled Reactor (MHTGRs). The modular high-temperature gas-cooled reactor (MHTGR) is cooled by high- temperature helium and moderated by the graphite blocks that form its core structure. Its fuel consists of tiny pellets of plutonium or highly enriched ura- nium, less than a millimeter in diameter, coated in several layers of protective material, which are bonded into fuel rods that, in turn, are loaded into the graphite blocks. (In Russian HTGR concepts, the small particles are bonded into tennis-ball-sized spheres of graphite, which can be loaded into and re- moved from the reactor without shutdown.) The MHTGR has been designed for improved safety for the next generation of nuclear power. It has not yet met commercial acceptance, in part because of high estimated capital costs. In its recent Plutonium Disposition Study, for example, the Department of Energy found that the MHTGR was the least cost-effective of the five reactors stud- ied.3i It is undergoing NRC design review, but is less far along in that process than the evolutionary ALWRs. Because of its unique fuel design, the MHTGR can potentially achieve very high burnup, destroying as much as 80 percent of the total initial plutonium on a once-through cycled The amount of plutonium remaining in the fuel would still be substantial, however, requiring safeguards comparable to those required for other spent fuel. Given the large global inventory of civilian plutonium, the 3i U.S. DOE, ibid. General Atomics, the maker of the MHTGR, has criticized this conclusion, arguing that a new HTGR concept, using direct-cycle gas turbines, would be more cost-effective, and that the time lines for other reactors used in the study were more optimistic than those used for the MHTGR. 32 Figures greater than 90 percent that are sometimes quoted refer to fissioning of Pu-239 or its transmutation into other isotopes, rather than destruction of total plutonium.
LONG-TERM DISPOSITION 185 security advantage of this high destruction fraction for one small part of the stock would be small.33 Using MH:TGRs for plutonium disposition would be expected to cost somewhat more and take somewhat longer, given the licensing uncertainties, than the use of ALWRs. To address the cost issue, General Atomics (GA), the MHTGR's developer, has proposed moving from traditional steam-turbine elec- tricity generation to running the turbine directly with the high-temperature he- lium coolant from the reactor. If successful, this might reduce capital costs and increase efficiency, thereby increasing revenue. This technology, however, re- quires further development and would introduce an additional set of licensing issues. General Atomics has agreed with MINATOM to pursue joint develop- ment of such a gas-turbine high-temperature reactor (GT-HTR), if the U. S. government decides to provide funding for the project. Advanced Liquid-Metal Reactors (ALMRs). Advanced liquid-metal re- actors (ALMRs), follow-one to existing LMRs, are under development in a number of countries (though the ALMR acronym is sometimes used to refer only to the U.S. program). Reprocessing and recycling of plutonium is an integral part of the operat- ing concept of these ALMRs. The most significant advance in the U.S. ALMR program, for example, is a pyroprocessing approach intended to significantly reduce the costs, wastes, and proliferation risks of reprocessing. In this inte- grated reprocessing approach, plutonium is never fully separated in a form that could be used directly in nuclear weapons, thereby reducing safeguards concerns.34 Such reprocessing and reuse of plutonium is applicable to the elimination option (described below), but not to the spent fuel option. If operated in a once- through mode, however, ALMRs could be used to transform weapons pluto- nium into spent fuel. The capital costs of these liquid-metal reactor concepts are generally higher than those of LWRs, however, and they are much less close to being licensed in the United States than are evolutionary ALWRs. These reactors are of greater interest for the elimination option than for the spent fuel option. 33 Advocates also point out that the high burnup of the MHTGR leads to an even more degraded isotopic composition than ordinary spent fuel. Although this would create some additional heat and radiation management issues in the design of a nuclear weapon from this plutonium, the relative problems of pre-initiation would not be greatly increased, since in straightforward designs such as those potential proliferators might use, pre-initiation is very likely even with the isotopic composition of ordinary reactor-grade plutonium. 34 This approach would mitigate concerns regarding theft of plutonium or covert diversion of material under safeguards. Possession of such a facility, however, would still offer a state the technology needed to produce separated plutonium for weapons, should it choose to do so openly. Since the United States and Russia already possess large nuclear arsenals, this is not a special concern in the context of this report. It must be remembered in considering the potential implications of a worldwide breeder economy employing such technologies, however.
186 LONG-TERM DISPOSITION MINATOM'S preferred disposition option is to use both weapons pluto- nium and separated civilian plutonium in the three to four BN-800 next- generation liquid-metal reactors it hopes to build. Like other ALMR ap- proaches, however, this raises concerns regarding delay, uncertainty, and cost. Some MINATOM officials continue to predict that the first BN-800 will be operational by 1997, with others following shortly thereafter.35 Although con- struction of the first two of these reactors was begun some time ago, it has been halted for several years as a result of lack of funds and disagreements among the various agencies and publics whose approval is required. These factors are likely to delay completion of these facilities for a substantial period. The cost of these reactors is likely to be significantly higher than the cost of LWRs of equivalent capacity, or the cost of other sources of electricity, and in the current economic environment in Russia, such a large-scale subsidy is likely to be diffi- cult for MINATOM to justify. Safety reviews of the BN-800 design may also result in delays. Because of these factors, some top MINATOM officials ac- knowledge that the first BN-800 is unlikely to be operational for at least 10-15 years.36 Even this estimate appears optimistic; it is difficult to rely on the avail- ability of these facilities on any set schedule. Plutonium would be a less costly fuel for these reactors than uranium (in contrast to the LWR case), because of the higher costs for uranium purchases and enrichment for their more enriched fuels. But Russia already has more separated civilian plutonium than needed to operate these reactors: each reactor requires only 2.3 tons of plutonium as startup fuel, and each produces more plutonium than it consumes thereafter. To use both the 25 tons of civilian sepa- rated plutonium already in stockpile and the nominal 50 tons of excess military plutonium in these reactors would mean continuing to add more fresh pluto- nium as spent fuel is removed, rather than allowing the reactors to fuel them- selves through reprocessing and recycle of the plutonium they produce. The net result would simply be a much larger quantity of spent fuel awaiting reprocess- ing in the fuel cycle for these reactors; the only potential cost advantage would arise from deferring payment of the costs of reprocessing for a longer period. In MINATOM's concept, the plutonium in the BN-800 spent fuel would ultimately be reprocessed and reused. Thus, although the weapons plutonium would initially be embedded in highly radioactive spent fuel (as in other spent fuel options), it would then be separated again. Only a few tons would exist in separated form at any one time, however. The BN-800 as currently conceived does not incorporate the integral reprocessing approach envisioned for future U.S. liquid-metal reactors (described below) and thus raises greater safeguards and security concerns. In short, compared to the use of VVER-1000 reactors or vitrification (see below), the BN-800 approach would involve higher capital costs, whose financ 3s Kudriav~sev, op. cit. 36 See Boris Nikipelov, remarks reported in Mark Hibbs, "Waste Disposal Top Priority for Back End, Nikipelov Says," NuclearFuel, July 19, 1993.
LONG-TEAM DISPOSITION 187 ing is uncertain; probable long delays; more uncertain reactor safety; and greater safeguards and security risks. Nor would the weapons plutonium play any essential role in the BN-800 program. Similarly, some Japanese officials have suggested that an international group fund a special-purpose LMR to be built in Russia to consume excess weapons plutonium. Like other ALMR concepts, this does not appear competi- tive with existing or evolutionary-design LWRs for transforming excess weap- ons plutonium into spent fuel. Summary of Advanced Reactors for the Spent Fuel Option. Advantages: New evolutionary or advanced reactors could meet the spent fuel standard; evolutionary designs at existing government sites might be easier to license and more acceptable to the public than the use of existing reactors for plutonium disposition. Disadvantages: Longer time and higher cost than for existing reactors; more advanced designs have significant cost and schedule uncertainties. Conclusion: Construction of new reactors cannot be justified for this mis- sion unless existing reactors are unavailable and alternative disposition options prove unpromising; if new reactors are built for this mission, they should be based on existing or evolutionary LWR designs, rather than advanced concepts. Disposal Options BURIAL WITHOUT PROCESSING In principle, plutonium in pits or other forms, after placement in suitable canisters, could simply be buried in geologic repositories such as Yucca Moun- tain or the Waste Isolation Pilot Plant (WIPP), assuming these will eventually open. Plutonium buried in this way would be much easier to recover and use than would plutonium in commercial spent fuel. Thus, this approach does not meet the spent fuel standard, and the committee therefore does not believe that this option should be pursued. In addition, such direct disposal approaches would raise difficult licensing questions concerning the acceptability of pluto- nium forms such as pits for repository disposal. Advantages: Potentially cheap and quick. Disadvantages: Poses only modest barrier to recovery; licensing and public acceptance concerns. Conclusion: Does not merit government support for the plutonium dispo . . . . siphon mission. VITRIFICATION One possibility for preparing plutonium for disposal is to combine it with other nuclear wastes that are already being prepared for disposal. In several countries, including the United States, radioactive high-level waste (FEW) is to
188 LONG-TERM DISPOSITION be mixed with molten glass in a process known as vitrification, producing highly radioactive glass "logs" that will be stored for an interim period and then buried in geologic repositories. Such vitrification plants are operational in several countries, and the process can be considered technically demonstrated. Excess weapons plutonium could also be vitrified-either with HLW, with other highly radioactive species, or in a glass bearing only the plutonium it- self but this would add some technical uncertainties. If plutonium were vitrified along with HLW in the vitrification campaigns currently planned, the glass logs produced would be resistant to theft by virtue of their large size and mass (the U.S. logs are to be some 2 meters long weigh 2 tons), their high radioactivity levels, and the need for chemical separation to retrieve the plutonium. In addition, in both the United States and Russia, these logs are to be stored at major sites in the nuclear weapons complex, with ac- companying physical security arrangements (which could be increased further if plutonium were added to the logs). Additional barriers to theft eventually would be provided by isolation in a waste repository and, perhaps, intermixing with outwardly similar waste logs that do not contain plutonium (making it very difficult for a potential proliferates attempting to remove logs from the repository for reprocessing to identify the correct ones to remove). The task of extracting the plutonium from the glass logs would be roughly comparable in difficulty to extraction of plutonium from spent fuel bundles, requiring a sub- stantial remotely operated chemical processing capability. Moreover, experi- ence with separating materials from such glass is far less widely disseminated than experience with spent fuel reprocessing. Although the glass logs scheduled to be produced in planned U.S. HLW vitrification campaigns would be signifi- cantly less radioactive than fresh spent fuel (comparable instead to SO-year-old spent fuel), the canisters in which they would be emplaced would still emit doses of more than 5,000 reds per hour at the surface. The plutonium in the logs would remain weapons-grade, rather than being isotonically shifted toward reactor-grade as in the case of the reactor options, but as noted in Chapter 1, nuclear explosives can be produced from either reactor-grade or weapons-grade plutonium. Thus, the committee judges that the plutonium in such glass would be approximately as inaccessible for weapons use as plutonium in commercial spent fuel particularly as in both the United States and Russia, the major vit- rification operations are at nuclear weapons complex sites, with all the associ- ated security. If the plutonium were vitrified without HLW or other highly radioactive species, so that the glass logs could be handled without remote-controlled equipment, the barrier to reuse would be much lower. The task of extracting the plutonium could be modestly complicated by adding various mixes of chemi- cally similar elements (such as rare earths) to the glass, but this approach has not been examined in detail. Whatever the mixture, it would still be substan- tially easier to process than plutonium in highly radioactive glass requiring remote handling. For states such as Russia or the United States, a chemical
LONG-TERM DISPOSITION 189 barrier alone would be insignificant. For others, it is the committee's judgment that most potential proliferators with the technical expertise, personnel, and organization required to produce an operable nuclear weapon from separated plutonium a substantial technical task in itself would also be able to extract plutonium chemically from a glass log not spiked with radioactivity. Thus, vit- rification without HLW or other radioactive species is not a viable disposition option in itself, though it might be a first step. If the initial step of vitrifying the plutonium separately before later revitrifying it with HLW were an alternative to longer storage of plutonium in pit form, and could be accomplished quickly and for modest additional cost, this might be a useful approach. Since plutonium has never been vitrified on a substantial scale, more technical uncertainties exist than in the case of the MOX option. The extent of the further engineering work required is delineated in a set of open questions below. The most straightforward way to vitrify weapons plutonium with radioac- tive wastes would be to incorporate it in the HLW vitrification campaigns already planned. At DOE's Savannah River Site, a multibillion dollar program to vitrify HEW, centered on the Defense Waste Processing Facility (DWPF), is slated to begin in 1994-1995 and to continue for the next 20 years. Several thousand highly radioactive 2-ton glass logs will be stored on-site for an in- terim period and eventually buried in a geologic repository. There have been many years of delays and substantial cost overruns in this project, and it is pos- sible that delays and difficulties will continue. Yet it is likely that by the time the approvals and modifications necessary to add plutonium to the process could be completed probably 8 to 12 years this system will be operational.37 Once a plutonium vitrification campaign began, it could be accomplished relatively rapidly: Savannah River estimates that 50 tons of plutonium could be incorporated into the planned vitrification campaign in eight years, without increasing the amount of glass produced, at a loading of 1.2 percent by weight in the glass. If higher loadings could be achieved (7 percent plutonium has been dissolved in a somewhat different glass form in laboratory-scale experiments), the time could be reduced accordingly. Thus, if the uncertainties are resolved favorably, the total vitrification campaign could probably be accomplished at least as quickly as the MOX option, and possibly significantly faster. Similarly, plutonium could be vitrified by using the not-yet-constructed Hanford Waste Vitrification Project (HWVP) melter instead of, or in addition to, the DWPF. Since it is not yet built, the H~tVP might be easier to adapt to this mission, though its date of availability is highly uncertain. The project is currently on hold pending review of the plans, and it appears likely to be de 37 Although the current DWPF melter is very large, there appear to be some advantages in smaller melters (which may in fact be considered for the second-generation DWPF melter). If it turns out that using small melters would speed the process of plutonium disposition, that option should be pursued.
190 LONG-TEAM DISPOSITION rayed for a substantial period.38 Vitrification facilities are operational or under construction in several other countries and could in principle be used for this mission, but their use would require international agreements and shipments comparable to those described above for the reactor options. Alternatively, a waste form could be developed specifically for this mis- sion, rather than piggy-backing on planned vitrification campaigns. This would have the advantage that the waste form could be designed specifically for opti- mum containment of plutonium. To provide a radiological barrier, the waste might incorporate the highly radioactive cesium-137 that is stored in substan- tial quantities at Hanford or the wastes stored in a hardened (calcine) form at the Idaho National Engineering Laboratory, instead of the liquid HLW cur- rently scheduled for vitrification. In the case of a glass waste form, smaller melters specifically designed for plutonium vitrification could be used to reduce criticality concerns in the melter. Although this approach might simplify the task of vitrifying the plutonium, the total costs would be higher because all the costs of production, handling, and disposal of this waste form (including the potentially substantial costs of providing and operating facilities capable of handling the highly radioactive materials that might be added to it) would have to be charged to the plutonium disposition mission, rather than only the net additional costs of adding plutonium to a previously planned HLW vitrification campaign. It is extremely unlikely that a U.S. geologic repository will be ready to re- ceive nuclear wastes of any kind before 2015. Consequently vitrified waste logs, with or without plutonium from weapons, will have to be stored in engineered facilities until a geologic repository is ready to receive them; with plutonium in the logs, safeguards would be required. The same is true, of course, for spent fuel from nuclear reactors. All of the planned capacity in the Yucca Mountain repository will be filled by wastes already scheduled to be produced. Therefore production of additional waste products specifically for weapons plutonium disposition (rather than piggy-backing on planned HEW vitrification cam- paigns) would require either displacing other wastes now scheduled to go into Yucca Mountain, expanding that repository's capacity, or waiting for an inde- terminate time until a second repository became available. Again, the same is true for spent fuel, if the reactor used for plutonium disposition would not oth- erwise have operated and produced this waste. Approvals and Licenses. Certifying the safety of the additional processes needed to add plutonium to currently scheduled HEW vitrification campaigns would take several years. Careful attention would have to be paid to melter de- sign to ensure against criticality, and to the system for treating gases released 38 Another HLW vitiation facility is being built at West Valley, New York, but the amount of glass to be produced there is too small to support the full plutonium disposition mission. There seems little point in building plutonium-handling facilities there if either Savannah River or Hanford, both of which have extensive plutonium-processing experience, could accomplish the mission.
LONG-TEAM DISPOSITION 191 during vitrification (the "offgas"), which must prevent release of plutonium into the environment and accumulation of plutonium within the offgas system itself. These engineering issues, while challenging, appear resolvable. Gaining public acceptance at the relevant sites may be more difficult, but if (1) the pub- lic is included in the decision-making process, (2) the association with arms reductions is made clear, and (3) a plausible case can be made that once proc- essed, the plutonium will eventually be shipped elsewhere for burial in a geo- logic repository, then public approval should be achievable. Overall, licensing and approval for this approach would probably be easier than for MOX, at least in the United States. Siting approval and licensing for a vitrification facility dedicated solely to plutonium disposition would probably be more protracted than for an approach piggy-backing on already scheduled HEW vitrification campaigns. Certification of the plutonium-bearing glass as a suitable waste form for emplacement in a geological repository would be the highest hurdle. Introduc- ing plutonium into Yucca Mountain would be nothing new: the nominal 50 tons of excess weapons plutonium is small compared to the 600 tons of pluto- nium in the spent fuel to be placed in the repository. But this plutonium would be in HEW glass, which would not otherwise contain substantial quantities of plutonium, rather than in spent fuel. The performance of the glass in preventing release of this plutonium, how- ever, is expected to be at least as good as that of the spent fuel, and it appears that the addition of plutonium would not degrade the ability of the glass to con- tain its other radioactive constituents. A number of studies indicate, moreover, that because of its extremely low solubility plutonium is not a major contributor to potential long-term health risks from the repository in most scenarios. Thus, although containment of the plutonium in the repository and preventing re- leases to the environment would require careful examination in the process of licensing such waste forms for disposal, these issues should be resolvable. Criticality of the logs over the very long term remains a concern. The amount of plutonium that can be placed in the glass without it going critical is greatly increased by the presence of boron (which absorbs neutrons), in the bor- osilicate glass. But the solubility of boron in water is much higher than that of plutonium. Over tens of thousands of years, if the materials in the repository were exposed to water, the boron in the glass could leach away, leaving behind the plutonium and the uranium-235 it produces by radioactive decay. Prelimi- nary calculations suggest that with plutonium loadings in the range of 1-3 per- cent, the logs would not be capable of sustaining a chain reaction even if all the boron and lithium leached away, unless water also filled a large fraction of the volume of the log. With similar assumptions concerning leaching away of neu- tron poisons and flooding with water, spent fuel (particularly MOX spent fuel, with its higher plutonium content) would also pose the possibility of criticality in the repository.
192 LONG-TERM DISPOSITION The result, if the waste did go critical, would be a low-power underground reactor, similar to the Oklo natural reactor that operated in Africa more than a billion years ago, which would generate heat in the repository and convert some fraction of the buried plutonium to buried fission products. While the quantity of fission products produced would be substantially smaller than those origi- nally buried in the repository, they would be produced at a time thousands of years in the future, when nearly all of the original fission products would have decayed away and the engineered barriers to prevent their release might have failed. Although such a low-power underground reactor would not necessarily be a threat to public health or safety, this issue could interfere with licensing, and it is prudent to resolve it sooner rather than later. One promising approach is to add another neutron poison to the glass, whose solubility in the repository environment is comparable to or lower than that of plutonium, such that it can be demonstrated that it will not be leached from the glass more quickly than the plutonium. Some of the rare earths, such as gadolinium, might be candidates. More research on this long-term criticality concern is required, but the committee believes that with methods such as these, the issue can be resolved in a few years at modest cost. Safeguards, Security, and Recoverability. As noted earlier, the difficulty of extracting plutonium from the glass logs would be generally comparable to the difficulty of extracting plutonium from spent fuel, with respect to both the complexity of the chemical engineering operations involved and the intensity of the radiation fields with which anyone handling the logs would have to cope. As for the opportunities for diversion or theft of the materials, it is impor- tant that all necessary plutonium operations for the vitrification option- both pit processing and production of the plutonium-bearing glass-could be carried out at a single nuclear weapons complex site with extensive safeguards and security. Thus, the number of required transportation and storage steps, and the associated opportunities for theft, would be less than in most of the reactor options. Fabrication of HLW waste logs would also be easier to safeguard than fab- rication of MOX fuel bundles.39 Monitors would have to confirm only the sin- gle step of mixing the plutonium with the HLW. Once that step had taken place, the plutonium would be in an intensely radioactive mix and very difficult to divert. There would be no capability within the vitrification facility for re- separating the plutonium from the HLW. MOX fabrication, by contrast, re- quires many steps involving large-scale bulk handling of plutonium with inher- ent accounting uncertainties, and at each step of the process the plutonium remains in a form from which it could be readily reseparated. For the glass operation, however, once the plutonium had been mixed with the HLW and incorporated in glass, the very high radioactivity and strong neu- tron absorption of the glass log would make accurate nondestructive assays of 39 Interview with Thomas Shea, IDEA Safeguards Division, August 1993.
LONG-TERM DISPOSITION 193 the amount of plutonium in the glass difficult. Thus, the traditional material accounting approach of detailed measurement of the inputs and outputs of the plant might have to be modified, with safeguards relying more on confirming that the plutonium was mixed with HLW, and on containment, surveillance, and security measures to ensure that no plutonium was removed from the proc- essing area or from the site without authorization. Although this would be an engineering challenge, adequate technologies exist to safeguard the glass pro- duction process, particularly given its inherent simplicity compared to the MOX fabrication process. Once the logs had been produced, they could be stored and safeguarded relatively cheaply until repositories were ready to accept them, in facilities al- ready planned, just as in the case of spent fuel. Indirect Impact on Civilian Fuel Cycle Risks. Treating pure weapons- grade plutonium as a waste to be disposed of would demonstrate the U.S. policy of generally discouraging the use of separated plutonium reactor fuels. Cost. A team at the Savannah River Site has estimated that vitrification with HLW would cost some $600 million, plus approximately $400 million to carry out the preliminary steps, including pit processing (which would also be required for the reactor optionsJ.40 The same team puts the cost of vitrification without HLW at less than $200 million (plus the same $400 million pre-proc- essing cost). These estimates are uncertain by at least a factor of two. The cost of a separate plutonium vitrification campaign that incorporated radioactive materials such as cesium-137 would be much higher, because the high costs of processing highly radioactive glass would then have to be borne entirely by the weapons plutonium disposition mission, rather than being shared by HLW dis- posal operations already planned. ES&M. The ES&H issues of adding plutonium to planned vitrification campaigns require further study. Because the plutonium is far less radioactive than the HLW, the net additional radioactivity to which workers would be ex- posed at the melter stage would be negligible. However, potential exposures in earlier processing must be considered, along with the risks of plutonium form- ing an aerosol that could be inhaled. Potential accident scenarios that could result in criticality or release of plutonium to the environment must be carefully addressed. Although these issues would pose engineering challenges, the state of the art should permit stringent regulatory standards to be met. Concerns related to the long-term environmental impact of placing pluto- nium-bearing glass into geologic repositories are described above. 40J.M. McKibben et al, "Vitrification of Excess Plutonium," Westinghouse Savannah River Company, WSRC-RP-93-755, 1993; and additional information provided by McKibben. This is an undiscounted estimate; discounting by 7 percent per year (see Chapter 3) would reduce the billion-dollar figure by roughly half, for comparison to other options. These estimates also include previtrification in a plutonium-only glass; eliminating this step would probably lower costs somewhat.
194 LONG-TERM DISPOSITION Vitrification of Russian Plutonium. It would also be possible to vivify Russian excess weapons plutonium. A waste vitrification facility with a nomi- nal output of 1 ton of glass per day is in operation at the Chelyabinsk-65 site in Russia and, by September 1993, was reported to have processed 150 million curies of radioactive waste, at a loading of between 150,000 and 200,000 curies per ton. The glass produced has somewhat higher loadings of radioactivity than are planned at Savannah River. Nearly 700 million curies of HLW remain in waste tanks at this site, similar to the holdings at Savannah River and some- what more than the amount at Har~ford.4i The phosphate-glass composition employed at this facility appears to be both less durable and less resistant to criticality if plutonium is embedded in it than the borosilicate glass planned for U.S. vitrification. Although borosilicate glass forms have been studied in Russia, the committee is not aware of any Russian plans to switch to a borosili- cate glass, or of any estimates of the cost and schedule for modifying the Russian facility to produce borosilicate instead of phosphate glasses. Some of the small melters developed in the U.S. vitrification program, however, are relatively low cost and transportable, and could therefore be shipped to Russia for a vitrification campaign there if modification of existing Russian melters proved too costly. Russia has operational remote-handling fa- cilities that could be used to operate such melters while incorporating HLW or cesium capsules in the product to create a radioactive barrier. Such small melters could be used to produce either small glass logs (which would pose a somewhat lower barrier to theft) or large glass logs like those produced in larger melters. The net cost of this approach depends on whether it is seen as an alternate way of handling the HLW vitrification campaigns already planned (in which case much of the cost might be offset by reductions in other vitnfica- tion costs) or as a separate campaign for disposing of weapons plutonium. In general, Russian authorities have objected to weapons plutonium dispo- sition options that would "throw away" the plutonium without generating elec- tncity. Moreover, given the environmental legacy of past handling of pluto- nium and the widespread public distrust of government safety assurances, gaining public acceptance and licenses for a plan to bury plutonium in a reposi- tory in Russia might be difficult. MINATOM itself has recently emphasized the environmental dangers of burying long-lived actinides such as plutonium, as part of its advocacy of a closed fuel cycle in which plutonium would be reproc- essed and reused. The ease of storing and safeguarding the vitrified logs, how- ever, would make it possible for Russia to defer decisions on committing them to geologic disposal for a substantial penod, as in the case of spent fuel. 4iInterview win Donald Bradley, Pacific Northwest Laboratory, October 1993. See also D.J. Bradley, "Radioactive Waste Management in the Former USSR: Volume III," Pacific Northwest Laboratory, PNL-8074, June 1992. For figures on wastes in the U.S. complex, see, for example, U.S. Congress, Office of Technology Assessment, Long-Lived Legacy: Managing High-Level and Transuranic Waste at the DOE Nuclear Weapons Complex, (Washington, D.C.: U.S. Government Printing Office, May 1991).
LONG-TEAM DISPOSITION 195 Applicability to Other Forms of Plutonium. As noted, vitrification may have an important role to play in dealing with the many tons of plutonium that exist as scrap and residues in both the United States and Russia. Small melters that could be set up on-site to vitrify these scraps and residues and thereby both stabilize them to reduce the hazards of near-term storage and prepare them for ultimate disposal-deserve consideration. Summary. Vitrification of excess weapons plutonium with HLW or other highly radioactive materials appears to be a feasible approach to creating a dis- posal form roughly as inaccessible for use in weapons as plutonium in com- mercial spent fuel. The technical uncertainties in this approach, however, are greater than for the MOX option. By incorporating plutonium into already planned HLW vitrification campaigns, tens of tons of plutonium could be dis- posed of in a campaign lasting less than a decade, beginning roughly a decade from now, for a probable cost of the order of $1 billion. Vitrification of Russian plutonium would require overcoming strong Russian government resistance to options that throw away plutonium's energy value and would be somewhat more complicated because of different vitrification approaches currently in place in Russia. Advantages: Moderate timing; moderate cost; meets the spent fuel stan- dard; can be accomplished at single government-owned nuclear weapons com- plex site; process easier to safeguard than MOX fabrication. Disadvantages: Unresolved technical uncertainties; discards energy value of plutonium; may be unacceptable to Russian government for Russian plutonium. Conclusion: Vitrification is a leading contender for long-term plutonium disposition. Major Outstanding Issues: Subjects that require further study include: · the amount of plutonium that can be dissolved in the glass, while maintain- ing an acceptable waste form for ultimate geologic disposal; · the required modifications to existing vitrification approaches; · criticality safety in the melter and safety of the system to treat gases released . . . A. . during vltntlcatlon; · relative advantages of large and small melters for this mission; · long-term performance of plutonium-bearing glass in a repository environ- ment, including effect of plutonium on glass stability, boron leaching, criti- cality risks, and the use of neutron poisons in addition to boron to mitigate criticality; ES&H and safeguards; · recoverability of plutonium in HLW glass, compared to spent fuel; · costs and schedule to incorporate U.S. excess weapons plutonium in the Sa- vannah River vitrification campaign, the Hanford vitrification campaign, or a separate vitrification campaign; .
196 LONG-TERM DISPOSITION · costs and schedule to modify the ongoing Russian vitrification campaign to produce borosilicate glass and incorporate plutonium, or of a separate plu- tonium vitrification campaign; and · applicability of vitrification options, particularly those using transportable melters, to plutonium in other forms, such as scrap and residues. A plutonium vitrification campaign would presumably be carried out by the government organizations already working on vitrification. Institutional issues would include: · safeguards and security for the process, including possible international agreements; · licensing and local approval for plutonium vitrification operations; · the likely political impact of plutonium disposition on other countries' plu- tonium fuel programs; and · the likelihood of Russian government and Russian public agreement to vit- rify Russian excess weapons plutonium. DEEP BOREHOLES Very deep boreholes-perhaps 4-kilometers deep-have been considered in several countries for disposal of spent fuel or HEW, and this is a possible approach for plutonium disposal as well. Excess weapons plutonium would generate far less heat than spent fuel or HLW, and would take up much less space, but it could raise greater concerns regarding potential criticality. Because of the boreholes' great depth and the very low permeability of granite, bore- holes might isolate such materials from the biosphere for an even longer period than mined geologic repositories could. Nevertheless, beep borelioles have~-not~~~~~~ ~~ ~~~~ ~~ been selected as the preferred disposal method in any country, in part because of the greater difficulty (compared to mined geologic repositories) of engineer- ing the disposal site, characterizing the physics and chemistry of the surround- ing rock, monitoring the material once emplaced, and retrieving it if required. Sweden currently has the most active remaining program examining deep- borehole disposition as a backup to the preferred mined repositories. Boreholes have received far less detailed study than have mined repositories, and therefore a larger number of outstanding technical issues remain. Boreholes have been drilled in crystalline rock to depths of 1.5 kilometers or more. in the United States and four other countries, though the mission of emplacing large quantities of material at depth would pose somewhat different challenges. In current concepts, the material would be placed in canisters in roughly the bottom 2 kilometers of a 4-kilometer-deep hole, with clay seals separating each canister and a long column of clay, topped by concrete, on top of the entire assembly of canisters. Figure 6-3 illustrates this concept. Pluto- nium might be placed in specially engineered canisters after being processed A, ... _
LONG-TERM DISPOSITION 197 Mined Geologic Repository / ~ Surface Facilities Shafted l Bioschere ~ Deep Borehole Repository `~ Borehole 1 if-Borehole FIGURE 6-3 Deep borehole disposal Source: Redrawn from Woodward-Clyde Consultants, Very Deep Hole Systems Engi- neering Studies (<San Francisco, Calif.: Woodward-Clyde Consultants, 1981~. and combined with neutron poisons to reduce criticality risks.42 Fifty tons of excess plutonium could be placed in one or several holes. Cost estimates for drilling such holes are in the range of $100 million. The process could be ac- complished quickly once the necessary approvals and licenses had been se- cured (a problem discussed below). The risk of the material being released into the environment from the Borehole requires further study. There are substantial reasons to believe, how- ever, that this risk should be low if the borehole is in an area free of geologic activity that might bring the material to the surface, and free of vertical faults in the rock that might create a pathway for the material to migrate toward the surface. In particular, the very saline water that is often found at great depth would make it virtually impossible for material in the Borehole to rise toward the surface by convection: this water is significantly denser than the fresher water above and therefore does not rise through it even if heated. 42 The committee does not believe its role is to suggest drastic changes in current waste management approaches unless they are necessary to solve the plutonium disposition problem. Hence, it would not recommend the Borehole approach for disposing of plutonium that had already been vitrified with HLW, or transformed into spent fuel in reactors, unless U.S. policy for disposal of HEW and spent fuel changed to favor the borehole approach. This does not appear likely.
198 LONG-TERM DISPOSITION Plutonium in deep boreholes on the territory of Russia or the United States would be inaccessible to potential proliferators, but would be accessible to the state in control of the borehole site. Redrilling the hole could be accomplished within a few months. Such activity would be observable weeks or months before the plutonium was retrieved, particularly if the site were subject to agreed monitoring (unmanned seismic detectors could sense any drilling activity). Thus, deep boreholes represent a class of options that go a long way toward eliminating the proliferation risks posed by excess weapons plutonium, but do not go quite as far in reducing the potential breakout risks associated with this material's existence. Given that leading segments of the Russian government see plutonium as a valuable asset that must not be irrevocably thrown away- but also perceive the proliferation risks associated with the material~ptions such as the borehole approach might be attractive, representing in a sense a form of "storage" of plutonium, greatly reducing near-term security risks while saving the plutonium for the day when it can economically be used as fuel. Gaining the necessary approvals for such an approach could be problem- atic. In the United States, a new waste disposal method would have to pass the same hurdles that have raised difficulties for geologic repositories, including: site selection; congressional approval, including funding; regulatory approval; and public acceptance. Deep-borehole disposal faces obstacles on each count. Over the years, Congress has allocated billions of dollars for studies of geologic repositories, and has taken the politically difficult step of selecting a site. Ob- taining approval for an entirely new approach would be difficult, as would gaining the necessary funding. The regulatory agencies have struggled for years to develop a regulatory framework for licensing a mined geologic repository, and they have developed some technical competence for reviewing repository proposals. Deep-borehole disposal, although similar in some respects, would require new regulations and new expertise. Perhaps more importantly, it would require the Nuclear Regula- tory Commission (NRC) to develop licensing methods without the ability to monitor or readily retrieve the materials emplaced; initial monitoring and re- trievability are a central basis for current NRC repository licensing concepts. Furthermore, the NRC would likely require quantitative values for the parame- ters that characterize the local geochemistry of the rock, the extent of fracturing of the rock, the details of water flow, and similar factors (as it has for Yucca Mountain). Obtaining comparable data for deep-borehole sites would be a ma- jor challenge. Failure analysis, particularly of the disposal process, has yet to be done. None of these tasks is impossible, but they will take time. Public accep- tance is also uncertain: the public would have to be convinced that this ap- proach was acceptable for plutonium disposal, though it was not being pursued for HEW or spent fuel. During the approval period, the plutonium would re- main in intermediate storage, with all the associated problems discussed previously.
LONG-TEAM DISPOSITION 199 In the different and evolving regulatory environment in Russia, where no consensus on repositories or sites has yet been reached, these matters are diffi- cult to judge, although they might present fewer problems than in the United States. Advantages: Implementation steps are quick and relatively low cost; ap pears to present low environmental and safety risks; greatly reduces prolifera- tion risk; may be more politically acceptable to Russian government than other disposal options. Disadvantages: Readily recoverable by host government; requires further development; possibly large costs and delays in licensing a new geologic dis- posal approach. Conclusion: At present, because it is less fully developed, the borehole op tion ranks behind the spent fuel and vitrification options as a contender for long-term plutonium disposition, but further research could show it to be com- parably attractive. Major Outstanding Issues: The borehole option is the least thoroughly studied of the options the committee has identified as deserving further atten- tion. Outstanding technical issues include: · mechanisms for possible transport of radionuclides to the surface; · advantages and disadvantages of different geologies and sites for borehole disposal; · methods of collecting data on the characteristics at depth of potential sites, sufficient to permit analysis necessary for site selection and licensing; · approaches to monitoring and retrieval of emplaced materials; · preprocessing required to create an acceptable waste form for disposal and reliably prevent criticality in the borehole; · techniques for emplacement of the material in the hole; · potential failure modes, particularly during emplacement, and their possible consequences; and · costs, including those for site selection, data collection, analysis, licensing support, drilling of the hole, emplacement, and follow-up monitoring. The primary institutional issues to be addressed in this case relate to licens ing, including specific approaches, difficulties, and likely schedules, in both the U.S. and the Russian contexts. SUB_SEABED DISPOSAL Disposal of HEW by burial in the mud layer on the deep ocean floor "sub-seabed disposal" has long been considered the leading alternative to mined geologic repositories.43 In recent years, however, with the choice of 43 This sub-seabed option in mid-ocean areas should not be confused with the idea that wastes should be placed in the "subduction zone," where one tectonic plate is slipping beneath another and the wastes would therefore be carried deep beneath the earth's crust. The problem with this approach is that
200 LONG-TERM DISPOSITION mined geologic repositories as the primary disposition approach, sub-seabed disposal has received little further attention or funding. This approach could also be used with weapons plutonium. The differences between plutonium and HEW are noted above in the discussion of deep-bore- hole disposal. The deep ocean floor in vast mid-ocean areas is remarkably geologically stable; smooth, homogeneous mud has been slowly building up there for mil- lions of years. The concept envisioned for HEW was to embed it in containers perhaps 30 meters deep in this abyssal mud, several kilometers beneath the ocean surface. One approach for doing so would be place the material in long, thin "penetrators" inert metal shells that would be dropped from ships and would then penetrate easily into the mud, which, it is believed, would flow to reclose the hole above them (see Figure 6-4.) The penetrator casing could be expected to last for as much as a few thousand years long enough for the main radioactive components of HEW to decay, but not long enough for plutonium to do so but the mud itself would be the primary barrier to release of the material into the ocean, because the time required for diffusion of radionuclides through this mud would be very long. Although there are some life forms in the upper meter or so of the mud, sampling studies indicate that the emplacement depths envisioned for this purpose are far below the depths where life forms exist that would be expected to have a major impact on transport of radionuclides to the surface. Moreover, although huge deep-ocean storms that perturb the ocean bottom have been detected in some areas of the ocean, floor samples demon- strate that other areas have been free of such storms for substantial periods of geologic time. The suitable seabed area exceeds the land area available for deep geologic repositories by several orders of magnitude. If this method were used for excess weapons plutonium, some preprocess- ing would probably be desirable to limit the risk of criticality, particularly as the plutonium containers would eventually flood with water. The processed material (perhaps a plutonium-boron composite) could be placed directly into the penetrators, which would then be emplaced by ship. The process could be quick, if licensing and public acceptance obstacles could be overcome. A1- though the committee has not done a full cost analysis, implementation of this option might be in the lower range of costs, probably amounting to several hundred million dollars for the nominal 50 tons of excess weapons plutonium. As with the borehole approach, however, the costs of developing and licensing the option would be far higher than the costs of implementation. The recoverability of plutonium placed in penetrators in the sub-seabed mud would depend on several factors. If the plutonium remained confined in the penetrators and if the location where they were embedded was even "fast" seafloor motions proceed at a rate of the order of ~ centimeter per year, meaning that in all of historic time (some 5,000 years) the material would only have moved 50 meters. Furthermore, the subduction zones are geologically active and unpredictable prone to volcanoes, among other phenomena. For these reasons the committee did not consider the subduction-zone option any further.
LONG-TERM DISPOSITION 201 \ BASIC ~8 BOOSTED AL. hi, DRILLED / FIGURE 6-4 Sub-seabed disposal Source: Redrawn from JK Associates, The Subseabed Disposal Project: Briefing Book 1985(JK Associates: 1985~. approximately known, countries with sophisticated deep-ocean technology could recover the plutonium, albeit at some cost. Sonar could detect the solid penetrators in the mud. Once detected, the penetrators could be retrieved by ocean drilling ships, or by ordinary ships equipped with a small derrick that could be lowered to the bottom for canister retrieval. Clearly, knowledge of the precise location (which would be available to the country that emplaced the penetrators) would make the job easier. For less developed countries and sub- national groups, recovering plutonium from the seabed might be more costly and time-consuming than recovering plutonium from spent fuel. To limit such recovery possibilities, the area in which the plutonium-bear- ing canisters had been deposited could be monitored for an indefinite time, if that were agreed on. In addition, recovery could be made more difficult by the use of"stealth" canisters designed to be difficult to detect with sonar, or by eliminating the detectable penetrators sooner rather than later, for example, by using canisters designed to dissolve soon after emplacement or using drills that would pump a plutonium solution directly into the mud, at appropriate depth, without the use of a canister. Such concepts have not been considered for the disposal of HEW, where retrieval is not an issue and the canister provides a
202 LONG-TERM DISPOSITION major barrier to release of the radioactive materials, most of which decay far more rapidly than plutonium. Sub-seabed disposal would face intense political opposition from many quarters, and a complex web of national and international legal hurdles and regulations. The U.S. Marine Protection, Research, and Sanctuaries Act, also known as the Ocean Dumping Act, forbids all dumping of high-level radioac- tive waste at sea and has been interpreted as including sub-seabed disposal. In addition, the London Dumping Convention of 1972 bans "ocean dumping" of high-level radioactive waste. The parties to the convention have never agreed on whether it prohibits emplacement of wastes beneath the ocean floor, but a majority of the parties have expressed that view in the past. The parties have agreed that if the technical feasibility of the concept is demonstrated and one or more countries wished to pursue such a disposal approach, the convention would be the appropriate forum in which to consider the matter. On November 12, 1993, the United States and 36 other nations voted to ex- tend the convention to ban dumping of low-level radioactive waste as well. Proposals for an explicit prohibition on sub-seabed disposal are reportedly slated to be discussed in 1994 or 1995. Further, the Law of the Sea Treaty, if it enters into force, would create an international authority that would regulate activities on the seabed, which would presumably assert authority over sub- seabed disposal. In addition to this legal framework, any proposal for disposal in or below the oceans is likely to provoke intense public and political opposition, both within the United States and internationally. In short, gaining approval from a majority of the parties to the London Dumping Convention for sub-seabed dis- posal of plutonium, and overcoming the political, legal, and regulatory hurdles (including providing experimental data that do not yet exist), would be diffi- cult, uncertain of success, time-consuming, and expensive. Given the strong resistance of many countries to placing such wastes anywhere in or below the ocean, the committee does not believe that such an approach should be pursued if it is merely to address excess weapons plutonium a problem that only two countries (the United States and Russia) are faced with, and for which other options are available. Only if the sub-seabed option were reopened for other purposes would this avenue be worth considering in more detail. Advantages: Technical implementation potentially quick and moderate to low cost; makes recovery of the plutonium by likely proliferators difficult. Disadvantages: Recoverability by emplacing state; direct conflict with in- ternational agreements; public acceptability and licensing difficulties, which could mean substantial delays and costs. Conclusion: Options to reduce retrievability are worthy of some further study, but not a leading contender.
LONG-TERM DISPOSITION 203 UNDERGROUND NUCLEAR EXPLOSIONS The Russian company CHETEK, associated with the Arzamas-16 nuclear weapons laboratory, has proposed that plutonium be disposed of with under- ground nuclear explosions. Hundreds or thousands of pits would be arranged around one or more nuclear devices at an existing underground nuclear test site.44 The detonation would vaporize both the pits and tons of rock surround- ing the blast, instantly incorporating the plutonium in a glassy matrix of vapor- ized and rehardened rock. This method is potentially quick and of moderate cost: depending on the number of pits destroyed in each blast, the number of explosions required might be in the range of a few to a few dozen, implying a cost of hundreds of millions to a few billion dollars. This method results in embedding tens of tons of plutonium in a com- pletely nonengineered and inherently somewhat unpredictable waste form, in an underground location not selected for or designed as a long-term repository, thus raising severe environmental concerns. In particular, concerns over poten- tial long-term criticality of the underground plutonium, after possible differen- tial leaching of different constituents in the rock, would be far more difficult to address than in the case of the vitrification or spent fuel options, since there would be no opportunity to engineer the resulting waste form with this problem in mind. The amount of plutonium coming from tens of thousands of weapons would be an order of magnitude more than has already been deposited at these sites in the course of past nuclear testing. Moreover, this approach would conflict directly with the current U.S. and Russian policy of extending the cur- rent nuclear testing moratorium and pursuing a comprehensive ban on nuclear testing. This option would also face major problems of public and institutional acceptance. Finally, the material would be recoverable by the state that emplaced it, providing a plutonium mine with substantially more plutonium in each ton of rock than there is gold in some mines that are profitably mined today, and with dramatically lower near-term radiological hazard than is the case for the spent fuel or vitrification options. Advantages: Potentially quick and moderate cost; makes recovery of the plutonium by potential proliferators difficult. Disadvantages: Substantial environmental concerns; directly conflicts with current nuclear testing policy; remains recoverable by emplacing state; doubtful public acceptability and licensing. Conclusion: Does not merit government support for the plutonium dispo sition mission. 44 In principle, if nuclear safety issues could be adequately resolved, nuclear weapons themselves could be destroyed in this way, without requiring disassembly. Although this might significantly speed the overall disarmament process, it would mean throwing away the valuable materials in the warhead, such as highly enriched uranium, as well as those that have little value. In any case, the overall approach has so many liabilities that this variant is not of great interest.
204 LONG-TERM DISPOSITION ENCAPSULATION WITH SPENT FUEL BUNDLES OR ~GH-LEVEL WASTE LOGS Several variants of the direct burial option have been proposed in which excess weapons plutonium might be hidden among the highly radioactive ma- terials that will be buried in deep geologic repositories. For example, spent fuel bundles will be placed in large casks for repository disposal: the excess weap- ons plutonium could be formed into fuel bundles of identical shape and appear- ance, and placed inside casks containing other genuine spent fuel bundles. It would be effectively impossible to identify the casks that contained such "mock" fuel bundles from the outside, and it would be difficult for potential proliferators, even if they could get into the repository and find one of the ap- propriate casks, to open it safely with equipment that could plausibly be brought into the repository. Removing casks from the repository for later opening would be possible in principle, but difficult and easily detectable. A similar idea is to place canisters containing critically safe arrangements of some plutonium-bearing material, such as plutonium oxide or a plutonium- bearing glass without fission products, into casks containing spent fuel or HLW glass logs. Compared to vitrification with HEW, these approaches seek to make the plutonium nearly equally inaccessible to potential proliferators, while leaving it in forms that would be recoverable by the emplacing state. As discussed in the case of the deep-borehole option, such recoverability means that these ap- proaches would do less to reduce breakout risks or potential negative impacts on the arms reduction and nonproliferation regimes than would other ap- proaches. Recoverability could increase the prospects of political acceptance by the Russian government, however. These approaches cannot be implemented until geologic repositories are available. In the United States, this will not occur until after 2010; in Russia, the effort to develop an underground repository is in its early stages. In both countries, the possibility that a permanent repository would not be available for many decades cannot be excluded. In addition, if these techniques were used for permanent disposal rather than intermediate storage, the forms in which the plutonium was placed into the repository would have to be analyzed as to criti- cality risks and licensed as acceptable waste forms for disposal. Even more than in the case of the vitrification option discussed above (where the form in which the plutonium would be placed has been designed and studied for years as a repository waste form), this is problematic and could involve significant delays and costs. Advantages: Technical implementation quick and low cost; makes pluto- nium largely inaccessible to potential proliferators; may be more politically acceptable to Russian government than other disposal options.
LONG-TERM DISPOSITION 205 Disadvantages: Easily recoverable by host government; new geologic dis- posal waste forms could raise environmental issues and licensing delays; cannot be implemented until repositories become available. Conclusion: Does not merit government support for the plutonium dispo . . . . sltlon mission. Beyond the Spent Fuel Standard Although the spent fuel standard is an appropriate goal for excess weapons plutonium disposition, further steps should be taken to reduce the proliferation risks posed by all of the world's plutonium stocks, including plutonium in spent fuel. Separated reactor-grade plutonium poses risks less than, but comparable to, those of separated weapons-grade plutonium. Spent fuel poses proliferation risks that are initially far lower, but increase with time as the intense radioac- tivity that provides the most important barrier to recovery of this material de- cays. It is time for the governments of the world to turn their attention to this problem again, to examine how nuclear power can best be managed to mini- mize these risks. That broad question is beyond the charge of this study and will be affected by many economic, technical, and political factors outside its purview many of which have changed since the last major international re- view (the International Nuclear Fuel Cycle Evaluation, or INFCE) and are dif- ficult to predict. Nevertheless, a few remarks are in order. First, as discussed in Chapter 5, an improved international regime of safeguards and security for all separated plutonium and HEU, and ultimately for spent fuel as well, is required. The ur- gent problem of managing fissile materials from dismantled weapons should be used as the occasion for drawing the world's attention to building such a regime. In the longer term, further measures to limit human access to plutonium in spent fuel particularly older spent fuel are desirable. There are two main options available for this purpose: disposal of the material in locations that are relatively physically inaccessible (such as the geologic repositories, deep bore- holes, or sub-seabed options described above) or elimination of the material, either by fissioning or transmuting nearly all of it or by removing it essentially completely from human access (such as by shooting it into space). Complete elimination of plutonium has received considerable attention in debates over disposition of excess weapons plutonium. As noted above, the ad- ditional costs and complexities of the elimination options for excess weapons plutonium would be of little benefit unless also applied to other accessible plu- tonium, including the global stock of plutonium in spent fuel. At the same time, in considering possible elimination options for that larger stock, it is essential to remember that as long as nuclear power is being produced by fission of U- 235 in fuels that also contain U-238, plutonium will continue to be produced.
206 LONG-TERM DISPOSITION Thus until nuclear power is no longer produced in this way, there cannot be a "plutonium-free world." In general, the substantial costs of eliminating a large fraction of the global plutonium stock could not be justified if (a) the best of the nonelimination op- tions were able to offer acceptably low proliferation risks; or (b) the steps lead- ing to the elimination options would themselves generate security risks beyond those of the nonelimination options (as could be the case, for example, with some concepts for eliminating the plutonium by repeated reprocessing and reuse). Given these considerations, the committee believes that a limited research program should continue to examine long-term plutonium elimination options, but that no decision to move in the direction of eliminating the large stocks of plutonium in spent fuel can be made today. The only decisions in this area fac- ing the United States or other countries at the moment concern research priori- ties: none of the plausible elimination options will be ready for development or deployment decisions for years to come. There are three main "elimination" options that is, options for removing plutonium essentially completely from human access: 1. launching it into space, beyond earth orbit; 2. diluting it in the ocean (where it would be so dilute as to make recovery im- practicable); or 3. fissioning or transmuting nearly all of the atoms of the plutonium. As with the spent fuel approach, this latter option has several variants. Any of these three approaches would have either to address the entire mass of spent fuel (roughly 100 times greater than that of the plutonium alone) or include reprocessing on a massive, unprecedented scale to separate the pluto- nium from this larger mass. Both possibilities raise major complications and costs. Space Launch This concept has been examined in some detail for disposal of high-level waste-and rejected. It should also be rejected for plutonium. Launching the material into low-earth orbit (which requires a velocity of about 8 kilometers per second) would not be sufficient because material in such orbits falls back to earth over time scales that are short compared to the half-life of plutonium. Therefore the material would have to be launched into an orbit around the sun unlikely to encounter the earth (which would require a velocity of the order of 11 kilometers per second), or be put on a path to fall into the sun (more than 18 kilometers per second) more than or to escape the solar system entirely (16.8 kilometers per second). Since the size of the necessary rocket increases exponentially with speed, this would multiply the cost manyfold, compared to launching the material only into low-earth orbit.
LONG-TERM DISPOSITION 207 The rockets used would have to be extremely reliable; yet the possibility of a launch explosion or a rocket failure that would result in the material reenter- ing from space, immediately or after some time, could not be ruled out. There- fore the plutonium would have to be put in a reentry vehicle strong enough to reliably remain intact after any plausible accident, and a system might even have to be built to retrieve material left in low-earth orbit by rocket failures. The needed reentry vehicle would probably have a mass of the order of two to three times that of the plutonium itself. The reentry vehicles would be lofted into low-earth orbit by one rocket and then given the extra velocity required to escape; hence, both the reentry vehicle and the rocket to lift it beyond its initial orbit would have to be lifted to low-earth orbit, increasing the weight that must be carried to that height by nearly another factor of ten. Thus, disposing of 50 tons of weapons plutonium in this way would require lifting more than 1,000 tons of material into low-earth orbit. Costs for such launches currently amount to some $10,000 per kilogram, which would result in a total cost in excess of $10 billion, not including any development and licensing costs. Launch costs may be greatly reduced in the future, but when one considers that the costs of the necessary development program alone would probably be comparable to the total cost of other options, it seems extremely unlikely that the space launch option could be made competitive, even when it is considered strictly on a cost basis. Of course, there are many problems other than cost. Given the severe con- sequences if a substantial quantity of plutonium were dispersed in the atmos- phere, the design of the reentry vehicle containing the plutonium would have to provide virtually perfect confidence that plutonium could not be released in the event of an accident. It is hard to imagine how the public would be convinced that such near-perfect confidence was justified, and therefore public acceptance of this option appears extremely unlikely. Moreover, assuming that the payload remained intact in the event of an accident, it would fall to earth, and its possi- ble recovery by potential proliferators would pose a major security risk. As noted earlier, options for going beyond the spent fuel standard to total elimination of excess weapons plutonium that involve substantial additional costs, risks, or delays are not justified unless they are applied to the much larger stock of civilian plutonium as well. In this case, including the total global spent fuel stock would greatly increase the costs and risks just described, which are already likely to be prohibitive. Advantages: Would make plutonium essentially completely inaccessible for use in weapons. Disadvantages: Costly, time-consuming, risky, and unacceptable to the public. Conclusion: Does not merit government support for the plutonium dispo . . . . sltlon mission.
208 LONG-TERM DISPOSITION Ocean Dilution The cheapest and quickest method of making excess weapons plutonium completely irrecoverable would be to dilute it in the ocean. A single ship or submarine, equipped with long tubes through which to expel a dilute plutonium solution at great depth into large volumes of water (so that the concentration even when first put into the ocean would be within the U.S. regulatory stan- dards for drinking water), could disperse 50 tons of plutonium into the ocean in perhaps five years. Since ships and submarines are currently being retired short of their design life, there would be no need to pay for buying one, and the direct cost would be only the expense of modifying the platform for the dilution mis- sion and operating it for the requisite period of time. The cost of the steps re- quired to gain approval for carrying out such an undertaking, including what- ever licensing would be required, would greatly exceed the cost of actually carrying it out and are difficult to estimate. The committee notes, however, that international standards for disposition of low-level radioactive wastes in the oceans, administered by the International Atomic Energy Agency (IAEA), include important factors not considered in the U.S. regulations, including the fact that certain ocean species consumed by hu- man populations, such as seaweed and mollusks, accumulate plutonium in their tissues in concentrations as much as 3,000 times higher than those in the sur- rounding environment. With this factor included (and assumptions concerning how much of such seafood coastal populations consume, described in Appendix C), the volume of ocean into which the plutonium would have to be diluted to meet U.S. dose standards would be more than 100 million cubic kilometers, over three times the volume of the mixed surface layer of the oceans. It is ex- tremely unlikely that the plutonium could be successfully mixed into such a large volume, with no local "hot spots" where the concentration would be sig- nificantly higher, at any reasonable level of effort. Moreover, human knowledge of physical and biological processes in the open ocean is not sufficiently com- plete to predict with confidence what would happen if substantial quantities of plutonium were diluted in the ocean, or to be certain that all mechanisms by which dangerous concentrations could accumulate in a local area had been ruled out. Public and international opposition to any proposal to dispose of plu- tonium in this way would surely be intense. If, as mentioned above, the London Dumping Convention is amended to prohibit disposal of even very dilute radio- active waste in the oceans, this option would be unambiguously banned. Such a dilution approach would be even more out of the question if applied to the entire global stock of plutonium because far more radioactivity would be added to the ocean in that case. That problem would be more severe still if a decision were taken to dilute the entire spent fuel mass, rather than only the plutonium contained in the spent fuel, to avoid the costs of separating the plu- tonium from all the world's spent fuel.
LONG-TERM DISPOSITION 209 Advantages: Quick (not counting licensing and approvals); moderate cost; makes plutonium completely irrecoverable. Disadvantages: Substantial environmental hazards; conflict with interna- tional regulations; certain public and international opposition; likely licensing and approval delays. Conclusion: Does not merit government support for the plutonium dispo . . sition mission. Fission and Transmutation Since neither space launch nor ocean dilution is acceptable, technologies designed to fission or transmute nearly 100 percent of the plutonium are the only plausible elimination approaches. Plutonium destruction fractions greater than 80 percent appear attainable only with the help of fuel reprocessing and plutonium recycle. With such repeated reprocessing and reuse, virtually any type of reactor could in principle be used in an elimination option: while only fast-neutron reactors can fission all isotopes of plutonium, reactors with a thermal neutron spectrum, such as LWRs, can in principle transmute those isotopes they cannot fission into other isotopes they can, as part of their normal operations. Policymakers considering these elimination options should be under no il- lusions concerning the scale of the effort required. Completing a program to burn a large fraction of the world's plutonium stocks to 99 percent or more- including developing, deploying, and operating the necessary technologies and facilities would cost tens or hundreds of billions of dollars and take many decades or even centuries. The time required is a complex function of the percentage of plutonium consumed in each reactor cycle; the fraction of the plutonium in the fuel cycle that is actually in the reactor where it can be consumed; and the amount of plu- tonium lost to waste in processing. In the simplified calculations currently be- ing done, which do not include reactor development and construction time, the period required to achieve such destruction fractions is not dependent on the total amount of plutonium to be destroyed; rather, the amount of plutonium determines the reactor capacity required to meet these schedules. Consider, for example, a simple case in which a hypothetical reactor sys- tem were capable of consuming 10 percent of the plutonium in its core each year, and the amount of plutonium in the supporting fuel cycle (awaiting re- processing, in fuel fabrication, and the like) were equal to the amount in the reactor core. In this simple case, if there were no processing losses, 5 percent of the total remaining amount of plutonium in the system would be consumed each year. But because that total remaining amount would be declining con- stantly, the amount of plutonium consumed each year would also decline. Un- der this hypothetical model, it would take some 90 years before 99 percent of
210 LONG-TERM DISPOSITION the plutonium was destroyed.45 If one considered the fact that some plutonium would be lost to waste on each reprocessing cycle, the 99 percent destruction figure might never be achieved~epending on the effectiveness of the reproc- essing technology in reducing such losses. Such simple calculations indicate that the current design of the Advanced Liquid Metal Reactor would take hun- dreds of years to reduce stockpiles of plutonium and other transuranics by 99 percent. The accelerator-based conversion (ABC) concept could in principle achieve comparable results in decades rather than centuries (because of its much smaller reactor and reprocessing inventories), but to do so would involve several major challenges (see below). Thus, such an approach would require a commitment of unprecedented length and, at least for the near term, substantial subsidies. Institutional arrangements lasting many decades or even centuries would be required to manage such an effort.46 Whether or not such a plutonium elimination approach should be pursued is a subject integrally tied to the future of nuclear power and fuel cycles, going well beyond the committee's charge. If it were to be pursued, it is premature to select a particular reactor system as the preferred option for this purpose. The National Research Council's Panel on Separations Technology and Transmuta- tion Systems (STATS) is considering various options for nearly complete elimination of actinides (and possibly some long-lived fission products) as a waste treatment approach (known as actinide burning). The committee bene- fited greatly from discussions of the STATS panel's work. Its report, expected in 1994, should provide a useful basis for setting policy and research priorities in this area. Here, the committee confines itself to brief remarks on the various options: LWRs. Though today LWRs are only rarely considered for this role, the technology by far the most widely demonstrated and well-understood ap- proach to nuclear power~ould in principle be used for actinide burning, by repeatedly reprocessing their spent fuel and recycling it as MOX. With suitable reprocessing, 100 percent MOX-fueled LWRs could consume plutonium some- what faster per unit of thermal reactor power than MOX-fueled liquid-metal reactors. Complex issues would arise concerning the buildup of less desirable isotopes after repeated recycling, which is also the case with several of the other 45 Considering only the percentage of the original actinides destroyed is somewhat unfair to the actinide burning concept, since the actinide burners would produce electricity, that might otherwise be produced by LWRs operating on a once-through cycle, which would create an ever-increasing stockpile of actinides to be dealt with. Thus, a fairer approach is to compare the time-dependent inventory of actinides in the actinide burner concepts to the ever-increasing inventory that would be created by LWRs providing an equal amount of electricity. This somewhat shortens the time required to reach a given destruction percentage. 46 See Lawrence Ramspott et al., "Impacts of New Developments In Partitioning and Transmutation on the Disposal of High-Level Nuclear Waste in a Mined Geologic Repository," Lawrence Livermore National Laboratory, UCRL-ID-109203, March 1992. For a comparison of the fraction of actinide inventory destroyed as a function of time for various concepts, see Jor-Shan Choi and Thomas Pigford, "Inventory Reduction Factors for Actinide Burning,"unpublished paper.
LONG-TERM DISPOSITION 211 options described below. The repeated reprocessing and reuse of separated plu- tonium would raise significant proliferation risks, and this approach is there- fore probably not desirable if the primary goal is to reduce overall security risks. Similar remarks apply to CANDU reactors. LMRs. Liquid-metal reactors, with their fast-neutron spectrum, can fission all isotopes of plutonium and are frequently put forward as a prime candidate for nearly complete plutonium elimination. Several countries are examining their potential as actinide burners. As noted above, some advanced LMRs, such as that being researched in the United States, employ an integral reprocessing technique in which the plutonium is never fully separated, mitigating some of the safeguards concerns that would otherwise arise from the repeated reprocess- ing and recycling required for the elimination option. Nonfertile Fuels. The net rate of plutonium destruction would be increased somewhat if additional plutonium were not produced during reactor operations. This could be accomplished with the use of fuels that do not contain isotopes that produce fissile materials when they absorb neutrons (as the U-238 in typi- cal reactor fuels today does). Since they do not "breed" fissile materials, these are known as "nonfertile" fuels. Several concepts for such fuels have been pro- posed, all of which would require considerable development, both for the fuels themselves and to address reactor safety issues involved in their use. The advantage offered by such fuels for a plutonium destruction campaign may be less than is commonly thought. This is because even without such non- fertile fuels, simply increasing the plutonium concentration in ordinary fertile fuels would substantially reduce the amount of new plutonium produced for a given amount of energy generated (or for a given amount of weapons plutonium burned). For example, doubling the plutonium concentration in fuel (for example, 3.5 to 7 percent of heavy-metal atoms in MOX fuel for an LWR) would require, if the power level were to be kept the same, that the neutron flux in the fuel be lowered by a factor of two, by using control absorbers and neutron poisons. This lowered neutron flux would reduce the rate of production of new pluto- nium by about a factor of two (a bit more, actually, because the extra plutonium loading in the fresh fuel replaces fertile U-238 atoms). Higher initial plutonium loadings would reduce that rate still further. Thus, fertile fuels with high fissile loadings (such as might be used in liquid-metal reactors, for example) can re- duce the production of new plutonium substantially. Since, in addition, even nonfertile fuels cannot burn their plutonium con- tent down to zero (because at low enough concentrations of plutonium in rela- tion to neutron-absorbing fission products, a chain reaction can no longer be sustained), it seems unlikely that the development of such fuels for reactors not already designed to use them (the HTGR being the main example of a reactor type designed to employ nonfertile fuels) could provide an advantage large enough to justify the required level of effort.
212 LONG-TERM DISPOSITION Accelerator-based Conversion (ABC). Accelerator-based conversion (ABC) systems have been under study as a means of eliminating plutonium, and of fissioning actinides and transmuting fission products in order to reduce the longevity of radioactive wastes. In this concept, a reactor that was subcriti- cal meaning that the neutrons within it could not sustain a chain reaction without outside input is driven by neutrons produced by a beam of particles from an accelerator hitting a target. In the concepts that have received most examination, the subcritical reactor would have a fluid fuel (either an aqueous slurry or a molten salt) that would be fed continuously out of the reactor, re- processed to remove fission products, and fed back into the reactor.47 This option is only at the early paper-study stage and cannot be available on a large scale for decades. Both the proposed subcritical fluid fuel reactor technology and its fuel cycle technology are extremely challenging and un- proven. The reactor, for example, would have a radiation flux of order 10 times that in current LWRs, raising serious engineering issues concerning the sur- vival of the reactor materials. Reprocessing would take place within days or weeks after the fuel left the reactor, forcing the approach to deal with unprece- dented levels of radioactivity; at the same time, proponents claim that reproc- essing losses would be unprecedentedly low. If the estimated performance could be attained, however, such systems could destroy plutonium at a rate (per unit of thermal energy) comparable to those of the other destruction-oriented options and could reach high reduction factors for plutonium inventory more rapidly than many of the other options. The continuous on-line reprocessing proposed for ABC would offer some advantages in waste reduction and in safeguards against plutonium theft or covert diversion (but again, probably not against open diversion by the system's operators) shared in varying degrees by other advanced systems that use such reprocessing. Molten-Salt Reactors. Molten-salt reactors, based on the system explored in the 1950s-era Molten Salt Reactor (MSR) Experiment have also been pro posed as destroyers of plutonium. This concept is similar in many respects to the molten-salt ABC, except that the reactor is fully critical and therefore no accelerator is required. Proponents claim that MSRs offer major safety advan tages over existing light-water reactor technology. However, like ABC, MSRs would take decades to develop, license, and deploy. Pebble-Bed Reactors. Pebble-bed reactors (PBRs), originally developed for nuclear rocket applications, have also been proposed for use as plutonium destroyers. Like ABC and molten-salt systems, they are in the early stages of development. 47Solid-fue} concepts have also been examined but are perceived as not having some of the advantages of the fluid fuel approach.
LONG-TERM DISPOSITION 213 Modular High-Temperature Gas-Cooled Reactors (MHTGRs). In principle, the MHTGR could also be used in an elimination mode, by reprocess- ing and recycling its spent fuel. Reprocessing this fuel would be complex, how- ever, and MHTGR advocates have not pursued this approach in recent years. As indicated above, it is too soon to choose among these options. Addi- tional research is desirable to clarify the issues involved in elimination options in general and to identify the most promising options for that purpose. CONCLUSIONS Figure 6-5 summarizes the committee's judgments concerning the long- term disposition options described in this chapter. Any figure of this kind can only be an illustrative overview of the options and issues; by their nature, such figures are oversimplifications. Moreover, these ratings are inevitably judg- mental. The committee chose to use only three ratings high, moderate, and low" because the information available cannot confidently support more de- tailed assessments. This inevitably means that there may be wide variations among options that receive the same rating; two options might each be expen- sive enough to be rated as having "high" cost, for example, but one might be several times as expensive as the other. The committee has not attempted to reach an "overall" rating for each op- tion, since readers may rank the criteria differently. Such an overall rating can- not be reached simply by averaging highs and lows across columns. For exam- ple, as described earlier, the committee does not consider indefinite storage an acceptable option, because the black mark under "risks of recovery" with all it implies for the risks of theft, breakout, and the arms control and nonprolifera- tion regimes more than outweighs the low risks and costs of this option. Criteria. All the criteria are described in the negative, so that "high" cor- responds to high risks or costs, whereas "low" is a more favorable rating. The first three columns of the chart are all related to the speed with which an option could be accomplished, which the committee considers to be one of the principal criteria for choice (discussed under "Risks of Storage" in the text). "Technical Uncertainty" affects both timing and the degree of assurance of suc- cess, as does the following column, "Difficulty of Public/Institutional Accep- tance." The latter category includes licensing and public approval issues, and, where necessary, issues related to the approval of international parties. The third column, "Time to Execute," refers to the time required for implementa- tion once the obstacles represented by the first two columns have been over- come that is, once development is complete and the requisite licenses and approvals have been obtained. This includes the time required for any necessary facility construction or modification, and the time during which the option would be processing the excess plutonium stock.
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216 LONG-TERM DISPOSITION As in the text, "Risks of Handling" refers to the risks of theft or diversion of materials during the various processes involved before the material reaches its final state, while "Risks of Recovery" refers to the risks that the material might be recovered for weapons use (by the state from whose weapons it came or by others) after disposition was complete. Hence, the latter, combined with the several timing criteria, effectively portrays the committee's judgment of the option's political impact on arms reduction and nonproliferation (assuming that equivalent levels of transparency would be applied to all options); this impact does not receive a separate column in the chart. The "ES&M Risk" and "Cost" categories are self-explanatory. The final column, "Fuel Cycle Policy Signal," refers to the issue relating to more general U.S. fuel cycle and nonproliferation policies described in the text: those options involving the use of weapons plutonium in reactors would send the signal that the United States approved of such use, at least for this limited purpose, whereas the disposal options would send the signal that even for the pressing problem of plutonium disposition, the United States did not approve of the use of plutonium fuels. In this column, therefore, the committee simply indicates whether the option would or would not use plutonium in reactor fuel, rather than attempting a high, moderate, and low categorization. Ratings. For all the criteria other than "Technical Uncertainty," the option of using 100 percent MOX fuel in U.S. LWRs is used as the standard for a moderate rating. (Technical uncertainty for the LWR MOX option is rated low.) Options that involve greater risks or costs than MOX in LWRs are rated high, while those that involve significantly lower risks or costs are rated low. Options Indefinite Storage Indefinite storage is among the more complex options to rate, because for the next several decades storage would be relatively simple, safe, and low cost (at least in the United States), but these judgments would change if it were truly extended indefinitely. Indefinite storage is rated as having low technical uncertainty and time to execute because storage can be (and is being) implemented immediately. Stor- age is rated as low in risks of handling and ES&H risks (because no processing is involved), and low in cost (by assuming costs comparable to those at Pantex, rather than commercial charges for plutonium storage). The difficulty of ob- taining public and institutional acceptance is rated moderate, although it would probably be quite difficult to gain public approval for storage that was explicitly presented as lasting indefinitely, at least in the United States. Indefinite storage is the only option on the chart rated as having high risks of recovery, since the
LONG-TERM DISPOSITION 217 material could be removed from the storage site and used for weapons at any time. Minimized Accessibility LWRs with 113 MOX refers to the use of existing or modified LWRs, either U.S. LWRs using U.S. plutonium or Russian VVER-1000s using Russian plu- tonium. These are rated as having low technical uncertainty. They are rated moderate in most other categories, but high under risks of handling, because the material would have to be transported to three times as many sites as in the case of LWRs with 100 percent MOX cores. As described in the text, there are likely to be higher risks of handling in the former Soviet Union under present circumstances than in the United States. LWRs with 100 percent MOX (which, like the previous entry, refers to the use of existing or partly completed LVVRs, in this case with modifications as necessary for use of full-MOX cores) are rated moderate in all categories except technical uncertainty, which remains low, as in the case of LWRs with one- third MOX, because the modifications needed to accommodate full-MOX cores are not sufficient to create substantial uncertainties or require major development. CAND Us, like full-MOX LWRs, are rated moderate under all criteria ex- cept technical uncertainty, which is rated low, because this option would not require a major development program. The moderate rating for difficulty of acceptance is more doubtful than in the case of LWRLs, since Canadian accep- tance of plutonium fuel use remains uncertain. Similarly, the cost rating for CANDU reactors is more uncertain. Substitution for civil plutonium is rated high for difficulty of acceptance, because of the complex web of arrangements that would have to be changed to implement this option, but low for time to execute, because the scale of MOX use already planned is large enough to consume 50 or 100 tons of weapons plu- tonium quite rapidly if this option were agreed to. ES&H risks are rated low because there would be virtually no net additional risks compared to the pluto- nium use already planned; risks of handling would be rated low for the same reason, except that there is some significant difference in theft and diversion risk in the shift from reactor-grade to weapons-grade plutonium, and there are the risks of transport of the plutonium from its current location. Hence the risks of handling are rated moderate. Vitrification with high-level waste is rated moderate on all criteria except risks of handling, where it is rated low, because of the somewhat greater ease of safeguarding described in the text. The technical uncertainty, which is moder- ate, is greater than in the case of the reactor options just described. Although time to execute is also rated as moderate, vitrification might be accomplished somewhat more rapidly than the LWR and CANDU options if technical uncer- tainties are resolved.
218 LONG-TERM DISPOSITION Deep boreholes are rated high on technical uncertainty because they would require more development than either the existing reactor options or the vitrifi- cation option. They are rated high for difficulty of public and institutional ac- ceptance because of the likely difficulties of obtaining the necessary licenses. Boreholes are rated as having moderate risks of recovery, with the caveat that recovery would be less difficult for the state in control of the borehole site than would recovery of plutonium in spent fuel. Although the cost of implementation itself would probably rate as low, boreholes are rated moderate on cost because of the development and licensing programs required. These costs could in fact ultimately be in the high category (as is also the case with other nonrepository disposal options). Boreholes are judged moderate on ES&H risks, but if techni- cal uncertainties are resolved favorably, these risks could turn out to be low. Sub-seabed disposal is rated high in technical uncertainty because consid- erable development would still be required before this option could be imple- mented-but it is the most fully developed of the options receiving this rating. This approach is rated as having high difficulty of public and institutional ac- ceptance, because of the legal barriers and likely intense international oppo- sition to such disposal. As with deep-borehole disposal, however, time to exe- cute and risks of handling are rated low, and cost is rated moderate because even though implementation costs could be low, the costs of development and licensing would be substantial. Detonation with underground nuclear explosions is rated high for technical uncertainty, even though it is clear it could be done, because of the many unre- solved safety and environmental issues. Similarly, it is rated as having high ES&H risks and acceptance difficulties. Existing LMRs without reprocessing are less susceptible to across-the- board ratings than some of the other options because there are wide variations in the design and characteristics of these facilities; moreover, some are in coun- tries where the excess weapons plutonium is located, whereas for others, the plutonium would have to be shipped and agreements negotiated. Existing LMRs are rated as low in technical uncertainty because the use of plutonium in these reactors is amply demonstrated; however, there are outstanding technical issues regarding the safety of some of these facilities. The time necessary to execute is rated high, because of the relatively small capacity, advanced age, or poor availability records of the existing LMRs. ALWRs refers to LWRs built for this mission, whether existing or follow- on designs. Technical uncertainty is rated low (though this judgment applies primarily to existing and evolutionary designs). Time to execute is rated high because licensing and building new reactors would take substantially longer than using existing facilities. New LMRs (without reprocessing, and MHTGRs are rated high on time to execute and cost, because of the delays and costs of development, licensing, and construction for these advanced reactors, both of which are estimated to involve higher life cycle costs in the current market than evolutionary LWRs.
LONG-TERM DISPOSITION 219 Elimination Ocean dilution is rated as having high technical uncertainty, because al- though it is clear it could be done, there are large uncertainties concerning the ultimate ecological impact. It is rated moderate for cost, although the cost of implementation would be low, because of the likely costs of developing the op- tion and attempting to gain approval for it. Space launch is rated high for ES&H risks, because of the risks involved in possible launch accidents, but this rating could be reduced with a payload de- sign that provided high-confidence plutonium containment for all plausible accidents. LWRs or CANDUs with reprocessing are rated as having high time-to- execute and costs (as are all of the other reactor reprocessing options) because of the very long time required to eliminate nearly all of the plutonium by this means, and the high costs of reprocessing and recycle. Technical uncertainty is rated as moderate because the plutonium use demonstrated to date has not in- volved multiple-recycle fuel with its different mix of isotopes. Risks of handling are rated as high, because these options would involve repeated separation, transport, and use of separated plutonium, while several of the other reprocess- ing options are or can be designed to maintain the plutonium in a more theft- resistant form. ES&H risks are rated as high because of the record of ES&H impacts of reprocessing in some countries, but the committee notes that appro- priate application of resources would greatly reduce these risks. LMRs with reprocessing are also rated as having moderate technical uncer- tainty, because while some of these systems are being designed for a similar actinide-burning mission, considerable development is still required. Their handling and ES&H risks are rated as only moderate, rather than high, on the assumption that new reprocessing techniques that reduce wastes and safeguards risks would be employed. MHTGRs with reprocessing are rated as having high technical uncertainty, since a reprocessing approach has not been pursued for HTGRs in recent years, and such a plutonium elimination objective has not been examined in detail. Like LWRs and CANDUs with reprocessing, they are rated as having high risks of handling, because of the repeated reprocessing and use of fully sepa- rated plutonium that would be required. ES&H risks are rated as high, on the analogy to LWRs and CANDUs with reprocessing, but the same caveat applies. ABC is rated as having high technical uncertainty, because of the large amount of technical development still required. It is rated moderate for ES&H risk, but that judgment is quite uncertain: if ABC fulfills its proponents' expec- tations, ES&H risk could be quite low, but it is also possible that unexpected ES&H risks could arise. MSR and PBR receive the same ratings across the board as ABC, for much the same reasons. It is too soon to tell which of these technologies would be
220 LONG-TERM DISPOSITION preferable for the missions their advocates propose, if these missions are pursued. RECOMMENDATIONS · It is important to begin now to build consensus on a road map for deci- sions concerning long-term disposition of excess weapons plutonium. Because disposition options will take decades to carry out, it is critical to develop op- tions that can muster a sustainable consensus. · Storage should not be extended indefinitely, because of (1) the negative impact that maintaining this material in forms readily accessible for weapons use would have on nonproliferation and arms reduction, (2) the risk of breakout and (3) the risks of theft from the storage site. One of the key criteria by which disposition options should be judged is the speed with which they can be ac- complished, and thus the degree to which they curtail the risks of prolonged storage. · Disposition options beyond storage should be pursued only if they reduce overall security risks compared to leaving the material in storage, considering both the final form of the material and the risks of the various processes re- quired to get to that state. In the current unsettled circumstances in Russia, this . . . . . . ., - . minimum cnter~on IS a slgnlilcant one. · The United States and Russia should begin discussions with the aim of agreeing that whatever disposition options are chosen, an agreed, stringent standard of accounting, monitoring, and security will be maintained throughout the process-coming as close as practicable to meeting the standard of security and accounting applied to intact nuclear weapons. · Disposition options should be designed to transform the weapons pluto- nium into a physical form that is at least as inaccessible for weapons use as the much larger and growing stock of plutonium that exists in spent fuel from commercial nuclear reactors. The costs, complexities, risks, and delays of going further than this "spent fuel standard" to eliminate the excess weapons plutonium completely or nearly so would not be justified unless the same ap- proach were to be taken with the global stock of civilian plutonium. · The two most promising alternatives for the purpose of meeting the spent fuel standard are: 1. The spent fuel option, which has several variants. The principal one is to use the plutonium as once-through fuel in existing commercial nuclear power reactors or their evolutionary variants. Candidates for this role are U.S. light- water reactors (LWRs), Russian LWRs, and Canadian deuterium-uranium (CANDU) reactors. The use of European and Japanese reactors already licensed
LONG-TERM DISPOSITION 221 for civilian plutonium should also be considered for Russian weapons plutonium. 2. The vitrification option, which would entail combining the plutonium with radioactive high-level wastes (HLW) as these are melted into large glass logs. The plutonium would then be roughly as difficult to recover for weapons use as plutonium in spent fuel. A third option, burial in deep boreholes, has until now been less thor- oughly studied than alternative 1 and 2, but could turn out to be comparably attractive. · A coordinated program of research and development should be under- taken immediately to clarify and resolve the uncertainties the committee has identified regarding each of these three options. The aim should be to pave the way for a national discussion, with full public participation, in order to make a choice within a very few years. · Applying the spent fuel standard narrows the options considerably: 1. Options that irradiate the weapons plutonium in reactors only briefly ("spiking"), leaving it far less radioactive than typical spent fuel, and with little change in its isotopic composition, should not be pursued except possibly as a preliminary step on the road toward the spent fuel option. (Even for that pur- pose, in those cases the committee has examined, the possible advantages of the spiking option over continued storage do not appear to be worth the substantial cost of such spiking approaches.) 2. Options that involve only a chemical barrier to reuse such as vitrifica- tion of plutonium without HEW or other fission products should not be pur- sued, except possibly as a first step toward adding radiological or physical bar- riers as well. 3. Advanced reactors should not be specifically developed or built for transforming weapons plutonium into spent fuel, because that aim can be achieved more rapidly, less expensively, and more surely using existing or evolutionary reactor types. 4. Options that strive to destroy a large fraction of the plutonium without reprocessing and recycle, using existing or advanced reactors with nonfertile fuels, should not be pursued because such approaches cannot destroy enough of the plutonium to obviate the need for continuing safeguards, and the modest reduction in security risk that could be achieved is not worth the extra delay, cost, and uncertainty that development of such approaches would entail. · Production of tritium should not be a major criterion for choosing among disposition options. · Institutional issues in managing plutonium disposition are complex and the process to resolve them must be carefully managed. The process must pro- vide adequate safeguards, security, and transparency, as well as protection for
222 LONG-TERM DISPOSITION the environment, safety, and health; obtain public and institutional approval, including licenses; and allow adequate participation in the decision making by all affected parties, including the U.S. and Russian publics and the interna- tional community. Adequate information must be made available to give sub- stance to the public's participation. · Although the committee did not conduct a comprehensive examination of the proliferation risks of civilian nuclear fuel cycles, which would have gone beyond its charge, the risks posed by all forms of plutonium must be addressed. · While the spent fuel standard is an appropriate goal for next steps, fur- ther steps should be taken to reduce the proliferation risks posed by all of the world's plutonium stocks, military and civilian, separated and unseparated; the need for such steps exists already, and will increase with time. Options for near-total elimination of plutonium may have a role to play in this effort, and research on defining and exploring these options should be continued at a con- ceptual level. These options, however, can only realistically be considered in the broader context of the future of nuclear electricity generation, including the minimization of security and safety risks-the assessment of which is beyond the scope of this report. Studies of that broader context should have as one im- portant focus minimizing the risk of nuclear proliferation, and should consider nuclear systems as a whole, from the mining of uranium through to the disposal of waste; should consider feasible safeguarding methods as elements of devel- opment and design; and should take an international approach, realizing that other nations' approaches reflect their differing economic, political, technical, security, and geographic situations and perceptions.