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Medical Isotope Production without Highly Enriched Uranium 11 Progress in Eliminating HEU Use The focus of this chapter is on the third charge of the statement of task for this study (Sidebar 1.2), which calls for an assessment of “The progress that is being made by the DOE and others to eliminate all use of HEU in reactor fuel, reactor targets, and medical isotope production facilities.” Presently, the Department of Energy’s (DOE’s) highly enriched uranium (HEU; see Sidebar 1.1) elimination efforts are being carried out under the Global Threat Reduction Initiative (GTRI). This initiative is focused on the minimization of HEU in civilian research and test reactor fuels and targets. Research and test reactors that have defense-related missions and naval reactors used to power surface vessels and submarines are out of the scope of this program.1 Nuclear research and test reactors (Sidebar 11.1) have been in operation for more than 60 years. They underpin the development of power and propulsion reactors and are major research tools in the fields of nuclear physics and engineering, nuclear chemistry, materials science, and biology, and they contribute to scientific and technological advances in medicine, industry, and agriculture. Research reactors have become indispensable for the production of medical isotopes to supply a rapidly increasing demand 1 The amount of HEU in storage or use in declared Nuclear Weapon States for defense and naval propulsion purposes dwarfs the amount of HEU that is currently being used for civilian research reactor fuel and targets. The HEU under the control of the defense establishment is maintained under high security conditions to prevent its diversion for use by rogue states or terrorists.
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Medical Isotope Production without Highly Enriched Uranium SIDEBAR 11.1 Research and Test Reactors Research and test reactors are used primary as a source of neutrons for scientific and technical research and development applications and for the industrial production of isotopes. They are designed with high-power-density cores to produce a high thermal neutron flux (typically 1014–1015 neutrons per square centimeter per second) but have much lower thermal outputs (typically < 100 MW thermal) than reactors used to produce electricity (typically ≥ 3,000 MW thermal). These reactors have a wide range of designs, but typically comprise a cluster of fuel elements and control rods in a pool or tank of water with graphite, beryllium, or heavy-water reflectors. The cores and reflectors typically contain empty channels for irradiation of targets and test materials, and some reactors are designed with apertures in their pool or tank walls through which neutron beams can be accessed. HEU is well suited as a fuel for these reactors because it provides a high density of U-235, which allows high neutron fluxes to be obtained in a compact core configuration. Maintaining this high performance can be a substantial technical challenge when converting these reactors to use LEU fuel because existing fuel designs result in U-235 densities that are too low. Conversion may require a redesign of the fuel elements and/or the development of LEU fuel material that has high U-235 densities. This fuel material must be stable under the irradiation conditions that exist in these high-performance cores. As discussed in the text, suitable replacement LEU fuels have not been developed for some very-high-power-density reactors; these reactors cannot be converted until such fuels are developed. The development of such fuels is a major current focus of the RERTR program. for diagnostic and therapeutic procedures based on nuclear medicine techniques. More than 700 research reactors are known to have been commissioned worldwide, and 240 of these are currently in operation in 55 countries (Table 11.1); another 9 reactors are in various stages of construction and several more are planned. Since 1975, significantly more research and test reactors have shut down each year than have started up. Of the 240 operating research reactors, 203 are or were fueled with HEU. Almost all of these reactors are supplied with HEU of U.S. or Russian origin with only a small number supplied with HEU produced in the People’s Republic of China (simply referred to as China in the following discussion). The commerce in HEU for research reactors was recognized as a potential source of nuclear weapons-usable material beginning in the mid 1970s. Increasing concerns about the proliferation of HEU prompted the formation of the Reduced Enrichment for Research and Test Reactors (RERTR)
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Medical Isotope Production without Highly Enriched Uranium TABLE 11.1 Country List of Research and Test Reactors as of December 2008 Reactors Worldwide HEU-Fueled Reactors Identified for Conversion by the GTRI Country Operational Under construction Planned Shutdown Decommis-sioned Total Fully converted Partially converted Shutdown before conversion Not converted Albania Algeria 2 Argentina 5 2 2 2 0 Australia 1 2 1 1 1 Austria 1 2 2 1 1 Bangladesh 1 Belarus 1 Belgium 4 2 1 1 Brazil 4 1 1 Bulgaria 1 1 1 Canada 8 2a 1b 5 3 6 3 3 Chile 1 1 2 1 1 China 14 2 2 8 2 1 5 Colombia 1 1 1 Cuba Czech Republic 3 2 2 1 1 Democratic P.R. of Korea 1 Democratic Rep. of the Congo 1 1 Denmark 2 1 1 1 Ecuador Egypt 2 European Union 1 Finland 1 1
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Medical Isotope Production without Highly Enriched Uranium Reactors Worldwide HEU-Fueled Reactors Identified for Conversion by the GTRI Country Operational Under construction Planned Shutdown Decommis-sioned Total Fully converted Partially converted Shutdown before conversion Not converted France 12 1 14 5 7 1 1 5 Georgia 1 Germany 12 11 23 5 2 2 1 Ghana 1 1 1 Greece 2 1 1 1 Hungary 2 1 1 1 India 5 1 4 1 1 Indonesia 3 1 Iran, Islamic Republic of 5 2 1 1 Iraq 2 Israel 2 1 1 Italy 4 5 5 1 1 Jamaica 1 1 1 Japan 13 7 3 7 2 5 Jordan Kazakhstan 3 4 4 Korea, Republic of 2 2 1 1 Latvia 2 Libyan Arab Jamahiriya 1 2 2 Madagascar Malaysia 1 Mexico 3 1 1 1 Morocco 1 Myanmar
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Medical Isotope Production without Highly Enriched Uranium Reactors Worldwide HEU-Fueled Reactors Identified for Conversion by the GTRI Country Operational Under construction Planned Shutdown Decommis-sioned Total Fully converted Partially converted Shutdown before conversion Not converted Netherlands 3 2 3 2 1 Nigeria 1 1 1 Norway 2 Pakistan 2 2 1 1 Peru 2 Philippines 1 1 1 Poland 1 2 2 1 1 Portugal 1 1 1 Romania 2 1 1 1 1 Russian Federation 49 1 36 11 12 12 Saudi Arabia Serbia 1 1 Serbia and Montenegro Slovakia Slovenia 1 1 1 South Africa 1 1 1 Spain 1 3 Sri Lanka Sweden 3 1 2 2 Switzerland 3 2 1 2 1 1 Syrian Arab Republic 1 1 1 Taiwan 1 1 3 2 1 1 Thailand 1 1 Tunisia 1
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Medical Isotope Production without Highly Enriched Uranium Reactors Worldwide HEU-Fueled Reactors Identified for Conversion by the GTRI Country Operational Under construction Planned Shutdown Decommis-sioned Total Fully converted Partially converted Shutdown before conversion Not converted Turkey 1 2 1 1 Ukraine 1 2 1 1 United Kingdom 2 7 27 2 2 United States 41 117 69 28 17 11 Uruguay 1 Uzbekistan 1 2 1 1 Venezuela 1 Vietnam 1 1 1 TOTAL, WORLD 240 9 4 246 170 129 53 5 4 67 NOTES: There are currently 203 HEU-fueled reactors in operation worldwide; 125 of these operating reactors are in scope of the GTRI and 78 operating reactors are out of scope of the GTRI. See text for discussion. aMaple-1 and Maple-2 reactors; development discontinued in May 2008. bMaple X, which is planned as a materials test reactor and to take over the experimental program of the NRU reactor and support CANDU reactor development. SOURCES: Data from the IAEA Research Reactor Database (http://www.iaea.org/worldatom/rrdb/) and a written communication to the committee from DOE-NNSA. program2 by DOE in 1978. This concern was reiterated over the period 1978–1980 by the International Nuclear Fuel Cycle Evaluation (INFCE) sponsored by the International Atomic Energy Agency (IAEA). At about that time the somewhat arbitrary3 definition of HEU as uranium enriched in 2 The objectives of this program are to reduce and eventually eliminate all commerce in HEU for research and test reactors by developing, testing, and qualifying higher density fuels and targets as well as the conversion procedures to allow reactors to operate safely and efficiently on LEU with a minimal loss in reactor performance. 3 Glaser (2006) reviewed the rationale for selecting the less than 20 percent enrichment criterion for LEU. He concluded (pp. 18–19) that “Uranium fuel below 20% virtually elimi
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Medical Isotope Production without Highly Enriched Uranium the fissile isotope U-235 to 20 percent or more (≥ 20 percent) was internationally accepted (see Sidebar 1.1). The main program objective of RERTR was to reduce and eventually eliminate all commerce in HEU for research reactors. Around the same time as INFCE, the former Soviet Union initiated a similar program to reduce the enrichment of fuel for research reactors in its client states, initially from 80 or 90 percent to 36 percent. However, this Soviet program did not become widely known in the West until the Russian Federation (RF) became a full partner in RERTR in 1993.4 The progress that DOE and others have made to eliminate the use of HEU in research reactors is largely a result of the RERTR program and falls neatly into two major periods: 1978–2004, when RERTR and associated spent fuel return programs had modest resources and progress was relatively slow; and 2004–present, when RERTR and associated fuel return programs became part of the GTRI. RERTR PROGRESS: 1978–2004 The RERTR program has been focused on conversion of HEU research reactor fuel as well as conversion of HEU targets that are used to produce medical isotopes, because both fuel and targets contain direct-use material.5 The progress made by the RERTR program during this period is described below. Research Reactor Fuel The primary concern of the RERTR at its inception was the elimination of HEU reactor fuel. Efforts on elimination were concentrated on the conversion of reactors to low enriched uranium (LEU) fuels, and especially on the development, testing, and qualification of higher density LEU fuels (see Chapter 7) for use in reactors that could not convert to using existing qualified LEU fuels without incurring a significant technical penalty in performance (see Sidebar 11.1). nates the possibility that the material could be directly used for the construction of a nuclear explosive device. Specifically, as some straightforward considerations show, LEU cannot be used in a simple gun-type device, both because of its large critical mass and the corresponding neutron emission rate. Simultaneously and coincidentally, at an enrichment level between 15–20%, plutonium production is sufficiently suppressed to minimize the total strategic value of the material if implosion-type technology is available. For both reasons, the 20% limit represents a reasonable and even optimum choice as a conversion goal for research reactors.” 4 The Russians essentially declared themselves to be partners at the October 1993 RERTR Conference in Japan. 5 Direct-use material is directly usable in nuclear weapons. Such materials include HEU and separated plutonium.
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Medical Isotope Production without Highly Enriched Uranium The RERTR program work was led by DOE with help from the Department of State (DOS), which provided diplomatic assistance, and Argonne National Laboratory (ANL), which provided technical assistance. In the early 1990s, a significant role in the program was also played by an ad hoc group of research reactor operators from around the world known as the Edlow Group.6 This group successfully lobbied for the reinstatement of the Foreign Research Reactor Spent Nuclear Fuel (FRRSNF) Acceptance Program, which came into force in May 1996, initially for a 10-year period. In 1997, a tripartite initiative involving the United States, RF, and IAEA, known as the Russian Research Reactor Fuel Return (RRRFR) program, was also initiated. The FRRSNF Acceptance Program accepts the return of certain fuels containing HEU of U.S. origin. Aluminum-clad fuel is returned to the Savannah River site (SRS) in South Carolina, and TRIGA reactor fuel is returned to the Idaho National Laboratory (INL). DOE pays for fuel returns from other-than-high-income countries. High-income countries pay for their own fuel returns. There are other types of spent fuel (e.g., spent fuel with zirconium alloy cladding and oxide pellets as fuel meat) from demonstration reactors and one-off reactors such as the pebble bed reactor and a ship reactor in Germany and mixed oxide-burning fast breeder reactors in France and the United Kingdom. For the most part, the large spent fuel inventories from these shutdown reactors and some special experimental fuels (e.g., nitride fuel) and HEU booster rods are still in Europe and were never considered to be part of RERTR or the spent fuel return programs. The importance of these spent fuel return programs to the success of RERTR in this period cannot be overemphasized. Other than the altruism of complying with RERTR principles, the return of a research reactor’s HEU spent fuel to safe and secure facilities in the United States and Russia is the only tangible incentive for a reactor to convert to LEU. Over the 26-year initial period of the RERTR program, only 38 U.S.-designed research and test reactors were converted from HEU fuel to LEU fuel, and not a single Russian-designed reactor was converted. During the same period, more than 200 research reactors, the majority fueled with HEU, permanently shut down because of obsolescence, problems with aging materials and facilities, and (in a very few cases) the perceived cost of conversion. Given the large number of reactor shutdowns relative to conversions during this period, an outsider might conclude that the RERTR program 6 The group was named after its leader, Jack Edlow, of the Edlow International Company, who advised the ad hoc group of research reactor owners and operators on how to effectively convey their request for reinstatement of the spent fuel return program to the appropriate branches of the U.S. government through meetings with and letters to senior officials.
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Medical Isotope Production without Highly Enriched Uranium was waiting for time to accomplish its job. However, this characterization would be unfair. The modest funding of RERTR during the period, the long lead times required to develop, test, and qualify new high-density reactor fuels, and the time required to test a series of mixed LEU and HEU fuel cores7 all conspired to slow progress. Given these facts, it could be argued that progress was even better than might have been realistically anticipated. Of the new reactors commissioned during this period only one of significant power, Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II)8 in Munich, Germany, as well as a few Chinese Miniature Neutron Source Reactors9 (MNSRs) were started up with HEU. It was recognized from the beginning of the RERTR program that to convert many research reactors, particularly materials testing reactors and high-flux/high-performance reactors, without a serious loss of performance would require the development of higher density LEU fuels. ANL provided technical leadership for the development of high-density LEU fuels working in collaboration with the international community of fuel developers for research reactors. The program successfully developed and qualified LEU silicide fuels. These fuels have uranium densities of up to 4.8 g U/cm3 compared with typical aluminum-based HEU fuel densities of 1.6 g U/cm3. The FRRSNF was also successful during the initial period of the RERTR program, transporting enough fresh and spent HEU (much of the latter which had lost its self-protection10) to make several nuclear weapons to safe and secure facilities at SRS and INL. Meanwhile, the RRRFR program accomplished fresh HEU return shipments from Serbia, Romania, Bulgaria, Libyan Arab Jamahirya (Libya), and Uzbekistan to safe and secure facilities in the RF. All of this Russian-origin fuel is scheduled to be downblended to 7 For many reactors, conversion from HEU to LEU fuel takes place in stages by gradually replacing the HEU fuel elements with LEU fuel elements. The replacement can take up to 10 years per reactor for design and testing of mixed LEU and HEU cores to ensure that conversion could be carried out safely. 8 The research reactor FRM-II began routine operation in April 2005. It is fueled with Russian HEU purchased by the Euratom Supply Agency. 9 The Chinese-built MNSRs are low-power (27 kW) research reactors used primarily for neutron activation analysis, education, and training. The reactor cores contain less than 1 kg of HEU that is enriched in U-235 to 90 percent or greater. According to IAEA’s current research reactor database, there are four MNSRs in China and one each in Ghana, Iran, Nigeria, Pakistan, and Syria. 10 During their residence in a reactor, fuels and targets become radioactive as the result of the buildup of highly radioactive fission products such as Cs-137. This radioactivity is said to give the fuel or target “self protection” because it makes those materials difficult and hazardous to handle without specialized expertise and facilities. However, the targets used for medical isotope production are typically irradiated for only a few days, so there is not much buildup of fission products. Thus, the targets (and the waste resulting from their processing) lose their self protection in a relatively short time (1 to 2 years) after removal from the reactor (e.g., von Hippel and Kahn ; see also Vandegrift et al. ).
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Medical Isotope Production without Highly Enriched Uranium LEU. Unfortunately, no Russian-origin HEU spent fuel was returned under the program during this period. Targets for Isotope Production RERTR target conversion efforts were focused primarily on targets used to produce medical isotopes. As was the case for reactor fuel, it was recognized that conversion required the development of new target designs to accommodate the required five-fold increase in the amount of LEU to contain the same amount of fissionable U-235 as HEU (see Chapter 7). By the mid 1990s, MDS Nordion in Canada, the largest producer of molybdenum-99 (Mo-99), was using as much or more HEU per year in its targets as some high-flux research reactors used in fuel. Moreover, target burn-ups are only about 3 percent; consequently, the waste11 from target processing is still HEU and loses its so-called self-protection after a short period. All four large-scale producers of Mo-99 were using HEU targets during this period (and are still doing so): MDS Nordion obtains Mo-99 from HEU targets that are irradiated in the National Research Universal (NRU) reactor in Canada; Mallinckrodt and the Institut National des Radioéléments (IRE) obtain Mo-99 from HEU targets that are irradiated in the Belgian Reactor II (BR2), the High Flux Reactor in the Netherlands, and the Osiris reactor in France; and Nuclear Technology Products (NTP) Radioisotopes obtains Mo-99 from targets that are irradiated in the Safari-1 reactor in South Africa. See Chapters 2 and 3 for additional information about these producers. Two important conversion-related actions were accomplished during this initial period. First, ANL, supported by research reactors in Indonesia and Argentina, began a program to develop higher density LEU targets using uranium metal foil. These targets are described in Chapter 7. Second, the Comisión Nacional de Energía Atómica (CNEA), an important regional Mo-99 producer in Argentina, converted to LEU-based Mo-99 production using high-density aluminum-uranium dispersion targets in 2002. These targets are also described in Chapter 7. It would be accurate to say that this conversion was the result of the RERTR program and CNEA’s desire to market an LEU-based Mo-99 production process to other countries. CNEA relied heavily on the scientific literature and the advice from ANL for target design and dissolution process development. Note that the Australian Nuclear Science and Technology Organisation (ANSTO) was also producing Mo-99 during this period using 1.8–2.2 per- 11 None of this HEU waste from Mo-99 production has been returned to the country of origin. It remains in storage at isotope producers’ sites or in offsite facilities.
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Medical Isotope Production without Highly Enriched Uranium cent LEU targets. ANSTO is in the process of converting to the LEU targets and dissolution process developed by CNEA (see Chapter 3). RERTR PROGRESS: 2004 TO PRESENT In May 2004, within DOE’s National Nuclear Security Administration (NNSA), GTRI became a vital part of the U.S. National Security Strategy:12 To keep fissile material out of the hands of rogue states and terrorists … we must address the danger posed by inadequately safeguarded nuclear and radiological materials worldwide. The Administration is leading a global effort to reduce and secure such materials as quickly as possible through several initiatives including the Global Threat Reduction Initiative (GTRI). In the same timeframe, other policy statements relating to the use of HEU in the civilian community were made. During the analysis concerning recommencement of the recovery of spent fuel by the RERTR program, part of the final Environmental Impact Statement issued by DOE stated:13 A key goal of United States’ nuclear weapons nonproliferation policy is to reduce international civil commerce in HEU, since HEU can be used directly in the production of nuclear weapons. IAEA’s director general also announced that agency’s position on HEU elimination during this period:14 The countries involved should join forces to step up their efforts towards minimizing and eventually eliminating the civilian use of HEU. Joint research should be conducted to address the remaining technical hurdles involved in converting from HEU to LEU the operations of facilities (including research and large pulse reactors as well as critical facilities) and the production processes for medical isotopes. The United States and Russia have also expressed strong support for civilian HEU elimination as evidenced by the February 24, 2005, Joint Statement by President George W. Bush and President Vladimir V. Putin on nuclear security cooperation: 12 The National Security Strategy of the United States of America, March 2006. 13 http://www.epa.gov/EPA-IMPACT/1996/May/Day-17/pr-16570.txt.html. 14 http://www.iaea.org/NewsCenter/Statements/2006/ebsp2006n010.html.
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Medical Isotope Production without Highly Enriched Uranium The United States and Russia will continue to work jointly to develop low-enriched uranium fuel for use in any U.S.- and Russian-design research reactors in third countries now using high-enriched uranium fuel, and to return fresh and spent high-enriched uranium from U.S.- and Russian-design research reactors in third countries. With its broad mission to reduce and protect vulnerable nuclear and radiological material located at civilian sites worldwide, the GTRI automatically subsumed the mission of RERTR and associated fuel return programs into its portfolio. During this second period, the RERTR program received increased funding, increased visibility, and much more direct involvement by senior DOE-NNSA leadership resulting in accelerated progress. Increased funding led to acceleration in reactor conversion, fuel development, and a major new effort to promote the development of an LEU fuel fabrication facility. The demonstration of leadership by example through the recent U.S. domestic conversions of Florida, Texas A&M, and Purdue University research reactors has been accompanied by an increased rate of international reactor conversions. A more collaborative international approach is demonstrated by the Global Initiative to Combat Nuclear Terrorism, which includes principles and actions to address HEU minimization. This initiative has been adopted by 75 partner countries, including Belgium, Canada, France, and the Netherlands. The creation of GTRI during this period has directly resulted in: Direct coordination between RERTR and the HEU fuel return programs for the U.S.-origin and Russian-origin HEU, the FRRSNF, and the RRRFR program, respectively; Development of a standardized incentive and implementation policy; Greatly increased collaboration with IAEA to develop several Coordinated Research Projects (CRPs). In 1978 RERTR was a good idea for reducing the proliferation of weapons-usable HEU. After the September 11, 2001, attacks on the United States, it was seen by many as an even better idea. Surprisingly, however, it took more than 2 years for it to be reflected in significantly increased funding for the GTRI program in the United States. Research Reactor Fuel The GTRI has a strategic plan to convert 125 reactors of the remaining 203 HEU-fueled reactors still planned to be operating by 2018
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Medical Isotope Production without Highly Enriched Uranium (Table 11.1; Figure 11.1) and thereby minimize the commerce in HEU for research reactors but unfortunately not eliminate it. As shown in Table 11.1, four reactors that were identified for conversion within the GTRI have been shut down. The remaining 78 research reactors have defense-related missions, unique fuels, special-purpose designs, or are located in countries that currently do not cooperate fully with the United States on reactor conversion programs. These 78 reactors are not targeted for conversion under the GTRI and are in fact considered to be out-of-scope of that initiative. DOE-NNSA maintains a substantial and fluid list of these reactors.15 HEU will continue to be transported to these out-of-scope reactors until they are eventually shut down, and also to the nuclear navies of the world, most of whose propulsion reactors are HEU fueled.16 As a consequence, the original RERTR mission has been effectively modified from the goal to eliminate commerce in HEU for research reactors to a lesser goal of minimization. As of December 2008, the status of the conversion program is as follows (see Figure 11.1): 58 reactors have been fully or partially converted and 4 reactors were shut down before conversion; 38 of these conversions took place between 1978 and 2004 and 20 conversions (including conversions of 2 Chinese reactors) took place between 2004 and present; 40 reactors are estimated to be able to convert using existing qualified LEU fuels; and 27 reactors are planned for conversion with advanced LEU fuels that still need to be developed and qualified. A new high-density uranium-molybdenum (U-Mo) alloy fuel is under development that would allow the conversion of at least 19 of these reactors. Additional analysis is required to determine whether any of the remaining 8 reactors can be converted using this fuel. The GTRI program is focusing much effort on the development of these advanced high-density fuels, particularly U-Mo alloy fuels, with the goal of qualifying these advanced fuels by 2010. As noted above, the GTRI has converted 20 reactors in the period of nearly 4 years since it assumed responsibility for RERTR. This represents 15 Not all states have reported on their out-of-scope reactors, and IAEA inspectors do not visit research sites in weapons states to verify the presence of such reactors. Many of these out-of-scope reactors are located in Russia. DOE-NNSA and IAEA have information on some, but probably not all, of these reactors. 16 France uses LEU fuels in its propulsion systems.
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Medical Isotope Production without Highly Enriched Uranium FIGURE 11.1 Current status of the program for converting research and test reactors from HEU to LEU. a considerable acceleration over the pre-GTRI conversion rates, which averaged about 1.5 conversions per year. Moreover, the rate of conversions will likely increase over the next few years if funding levels are maintained, technical resources remain committed to conversion, and the government cooperation continues in countries where conversions are to be carried out. The future success of GTRI in converting the remaining HEU-fueled reactors will also depend on the successful development of higher density fuels based on U-Mo alloys. Following the successful development of uranium silicide fuels, the program turned to the development of U-Mo alloys in an aluminum matrix with an initial goal of achieving densities in the range of 7–9 g U/cm3. The program moved forward slowly, initially with limited funding. By 2004, hopes for the rapid qualification of such fuels had been severely dampened by failures of U-Mo dispersions in both plate and tube geometries in research reactors in Belgium, France, and Russia. These failures were all traced to the development of unstable interaction layers between the U-Mo fuel particles and the Al matrix, which caused swelling and decohesion of the fuel “meat” (Figure 11.2). One promising remedy that has been identified is to add 2–4 weight percent of silicon to the fuel matrix, which appears to drastically reduce the rate of swelling. Also, increasing the weight percent of Mo to 7–10 percent allows the fuels to perform in a stable manner under irradiation, even without the addition of silicon (Figure 11.3). These approaches, along with other proposed material fixes and improvements in the fabrication technology for fuel plates, provide some confidence that the qualification
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Medical Isotope Production without Highly Enriched Uranium FIGURE 11.2 Micrographs of U-Mo fuels showing (left image) interaction layers around the U-Mo particles (yellow areas), (middle image) lenticular-shaped voids at the interfaces with Al matrix (black areas), and (left image) decohesion of the fuel meat. SOURCE: Courtesy of Patrick Lemoine, Commissariat à l’Energie Atomique (CEA), France. FIGURE 11.3 Micrographs of irradiated U-Mo fuel material before (left) and after (right) the addition of silicon. SOURCE: Courtesy of Idaho National Laboratory. of a second generation of U-Mo dispersion fuel having densities of about 8.5 g U/cm3 will be viable over the next 2 to 3 years. ANL has been joined by INL as lead technical laboratory on new fuel development, and investigations have been initiated with the research reactor fuel development community worldwide. The partners are in Argentina, Canada, France, South Korea, and Russia, including both national laboratories and commercial fuel developers. This collaboration is a concerted effort to understand the swelling behavior of U-Mo fuels and overcome it. In a parallel effort, work to develop more advanced fuels (described below) is well underway. Uranium silicide and U-Mo fuels are not suitable to convert all remaining reactors, however. In particular, five high-performance reactors in the United States (the Advanced Test Reactor [ATR] at INL; the High Flux Isotope Reactor [HFIR] at the Oak Ridge National Laboratory; the National
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Medical Isotope Production without Highly Enriched Uranium Bureau of Standards Reactor [NBSR] at the National Institute of Standards and Technology in Maryland; the Missouri University Research Reactor [MURR] at the University of Missouri; and the Massachusetts Institute of Technology [MIT] reactor) will require higher density fuels. U-Mo monolithic fuel with a density of approximately 16 g U/cm3 is under development for this purpose. This fuel has not yet been qualified for use. GTRI identifies 27 research reactors that could utilize this U-Mo monolithic fuel for conversion.17 U-Mo-Al dispersion fuels having densities of 8–9 g U/cm3 are also under development. Candidate reactors for using this fuel are BR2 in Belgium, and the remote handling facility, ORPHEE, and the Jules Horowitz Reactor, all in France. Conversion feasibility studies need to be completed for these reactors. The Jules Horwowitz Reactor is under construction (see Table 3.2) and is slated to begin operation in 2014. It will use uranium silicide fuel having a 28 percent enrichment until the U-Mo-Al dispersion fuel is qualified. In Russia, fuel is qualified for specific reactors with focus on macroscopic behavior of fuel assemblies, and the fuel may be available for some reactors as early as the end of fiscal year 2009. Reactor-specific conversion efforts will continue for several years for Russian-designed reactors. In Europe, data collection for fuel qualification will be more basic and widely applicable but must be reviewed by each country’s regulator before use. The GTRI is planning a joint fuel qualification program with all the key European stakeholders. Preliminary evaluations suggest that the fuel testing for European dispersion qualification could be completed in roughly 3 years (i.e., by the end of 2011), which would culminate in an element test in BR2 (see Koonen, 2008). This element test would represent the final step in dispersion fuel qualification and as a lead test assembly for the BR2. The United States will provide fuel performance data and fuel design support required to complete this effort. The monolithic fuel qualification effort is primarily focused on supplying fuel for the U.S. reactors and potentially the FRM-II reactor, but this fuel could also potentially be used with reactors that could also use U-Mo-Al dispersion fuel. Fuel tests will be performed to support qualification of the “base” fuel form that supports conversion of MIT, MURR, and NBSR by the end of 2011, assuming a 1-year review by the U.S. Nuclear Regulatory Commission. Additional tests will be performed to enable qualification of “complex” fuel forms (which support conversion of ATR, HFIR, and potentially FRM-II) by the end of 2013. Although the dispersion fuel can use existing 17 The work on high-density U-Mo monolithic fuels does not provide a pathway for conversion to high-density U-Mo targets, because the stable Mo-98 in the targets would dilute the Mo-99 produced by fission. See Chapter 7.
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Medical Isotope Production without Highly Enriched Uranium commercial fuel supply infrastructure, the supply of monolithic fuel will require the development of new fuel fabrication capability. The HEU spent fuel return programs in the United States and Russia have played an important role in encouraging reactor operators and their authorities to convert. The importance of these programs is further underlined by the fact that the Edlow Group has remained together and renewed their call for a further extension of the FRRSNF as its termination date approached in 2006. Partially as a result of their efforts, the program was extended for another 10 years, to 2016, which almost reaches the strategic goal of the GTRI to complete the “in-scope” conversions by 2018. In Bratislava in February 2006, the United States and the RF pledged to continue work to return fresh and spent fuel from the U.S.- and RF-designed research reactors in third-world countries. In addition to committing to specific goals, as described below, this Bratislava Initiative18 also resulted in an agreement to provide progress reports every 6 months on accomplishments. These reports have proven to be a useful mechanism to drive programs forward at an accelerated pace. The seventh such report was made on June 7, 2008. This initiative resulted in 336 kg of fresh and 157 kg of spent Russian origin HEU fuel (enough for about 20 nuclear weapons; see Sidebar 1.1) being returned during this period (compared with only 105 kg of fresh HEU during the previous period). These shipments included the first return of Russian-origin HEU spent fuel in RRRFR program history. That fuel was returned from Uzbekistan, the Czech Republic, and Latvia.19 As of June 2008, FRRSNF had returned a grand total of 1146 kg of HEU in 41 shipments from 28 countries and RRRFR a grand total of 598 kg of HEU to safe and secure facilities in the United States and the RF, respectively.20 Approximately 40 percent of the HEU that the program has targeted for return has actually been returned to date. The 1146 kg returned to date is only about 20 percent of the 7335 kg U.S.-origin HEU that is abroad. However, NNSA has “moved the goal posts” and now considers 6016 kg of the total, which is located in Belgium, Canada, France, and the United Kingdom, to be “Material considered to be secure or to have an acceptable disposition path.” If one accepts this statement, then almost 91 percent of the “planned” U.S. origin HEU has 18 A fact sheet concerning the details if this initiative can be accessed from DOS at http://www.state.gov/p/eur/rls/prsrl/2005/42694.htm. 19 An additional 155 kilograms of HEU research reactor fuel was returned to Russia from Hungary in October 2008. 20 The results were presented by Jeff Chamberlin, Nuclear Removal Coordinator for the National Nuclear Security Administration, at the 2008 INMM Annual Conference in July 2008.
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Medical Isotope Production without Highly Enriched Uranium already been removed, and the ongoing program will be mainly repatriation of LEU from converted reactors. Although the overwhelming majority of operating research reactors in the world were designed either in the United States or the former Soviet Union, several other countries have designed and built research reactors in their own countries and/or foreign countries. These include Argentina, Canada, China, France, Germany, and the United Kingdom. Since the inception of RERTR, the only new reactor to be fueled by a significant quantity of HEU was FRM II in Germany, which may become an unfortunate precedent in the future.21 Although China is not officially a full partner in the conversion program, its announcement of the conversion of the 125 MW High Flux Engineering Test Reactor (HFETR) and associated HFETR-China22 is an encouraging sign that China too is moving to replace HEU fuel with LEU fuel. The IAEA-sponsored CRP involving China, IAEA, and the GTRI has enabled feasibility studies and conversion safety analyses to be conducted for several MNSRs both within and outside of China.23 The feasibility studies were completed in May of 2008. It has been determined that conversion of the MNSRs to LEU fuel is feasible without any compromises to performance or safety. Publication of an IAEA TecDoc that reports the results of this CRP is planned for sometime in 2009 that reports the results of this CRP. The Chinese have signed tripartite project and supply agreements with IAEA and Ghana, Syria, and Nigeria to take back the spent fuel from their MNSRs. China has also indicated in writing to IAEA that it would also take back the spent fuel from Iran and Pakistan.24 Targets for Isotope Production All four large-scale producers still obtain Mo-99 from HEU targets. However, some progress on target conversion has been made since 2004. Following Argentina, another small producer, the Indonesian National Atomic Energy Agency (BATAN), is close to LEU conversion using the foil 21 Nikolay Arkhangelsky (Rosatom, Russia), one of the world’s foremost research reactor experts, asserted in a November 2008 presentation that a limited number of very high power research reactors fueled with HEU may be required in the future to obtain sufficient neutron fluxes for some applied scientific experiments. He argues that such fluxes cannot be obtained using LEU. 22 These reactors are located near Chengdu in Sichuan province and have been fully converted to LEU silicide fuel. The Min Jiang Test Reactor (MJTR) on the same site uses irradiated fuel from the HFETR and will convert to using LEU fuel when the current supply of HEU fuel is exhausted. 23 The CRP is described at http://www.iaea.org/OurWork/ST/NE/NEFW/rrg_MNSR.html. 24 The information on China’s plans was provided to the committee in a written communication from Ira Goldman at IAEA.
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Medical Isotope Production without Highly Enriched Uranium targets and a modified Cintichem process pioneered by ANL. Successful processing of irradiated LEU foil targets has been demonstrated (Briyatmoko et al., 2007). As noted previously, the Australian replacement reactor, OPAL, will use CNEA’s high-density LEU target design and dissolution process. As described in Chapter 7, ANSTO is expected to become a large-scale producer of Mo-99. A CRP initiated by IAEA and supported by GTRI is developing techniques for small-scale indigenous producers of Mo-99 using fission of LEU or neutron activation. This initiative is described in Chapter 3. The CRP has contracts involving the irradiation of LEU foil targets with Chile, Libya, Pakistan, and Romania, while Argentina, India, Indonesia, Korea, and the United States (ANL, MURR) are providing technical support through memoranda of understanding.25 Poland and Egypt made successful requests to participate in the CRP after it had begun and are now actively involved. If the CRP achieves its goal, all new indigenous producers of Mo-99 will use LEU target technology or neutron activation technology freely provided through the supporters of the CRP. Clearly, this is notable progress toward the minimization of HEU at research reactors. As noted in Chapters 7 and 10, conversion of the targets used for Mo-99 production to LEU is technically feasible for all current processes, including those used by the four large-scale producers. In the cases of Argentina and Indonesia, conversion has been demonstrated not to affect product purity or product yield (Chapter 8). At present, GTRI has a limited ability to support conversion efforts, especially in a financial sense. While the reluctance of major producers to convert is understandable from a business standpoint, pressure to convert may grow as international efforts to minimize the civilian use of HEU intensifies. As discussed in Chapter 10, DOE can play an important role in conversion by providing technical support and, working with DOS, through continuing diplomatic interactions with producers’ home countries. Finally, the committee notes that little or no progress has been made by the GTRI in minimizing the HEU waste resulting from medical isotope production. This waste is accumulating at producers’ sites or at regional storage facilities (see Chapter 3). Of particular concern is the liquid HEU waste that is stored in the fissile solution storage tank (FISS tank) at the Chalk River, Ontario, site. The quantity of HEU in the tank has not been publicly disclosed, but the tank is likely to contain well in excess of 100 kg of HEU.26 25 The four major commercially based isotope producers are observers in the CRP and have also provided some technical support. 26 AECL stopped adding HEU waste to the tanks sometime between 2001 and 2006 and is now grouting the waste and storing it onsite. A final disposition pathway has not been determined.
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Medical Isotope Production without Highly Enriched Uranium The fact that the FISS tank wastes at Chalk River have not been solidified has led to speculation within the committee that these materials are seen as a hedge against a cutoff of HEU exports to Canada by the United States. HEU could be extracted from these liquid wastes and used to produce targets.27 At least two options exist for eliminating this waste. First, the wastes could be converted to LEU by adding natural or depleted uranium, a process known as “downblending.” Downblending would likely be a relatively simple step for the liquid wastes at Chalk River if there is enough space in the FISS tanks to accommodate additional material. Downblending solidified HEU wastes, which exist in calcined or grouted waste forms, would likely require mechanical treatment to introduce depleted or natural uranium so that the mixture could not be easily separated. These solid wastes might have to be dissolved before they could be downblended, which could be difficult. A substantial volume of radioactive waste would be generated from this process. The second option would be to return the waste from processing U.S.-origin HEU to the United States for downblending and storage. The liquid wastes would have to be solidified before they could be shipped, but the existing solid wastes might be shippable in their current forms. Whether there is a current legal and policy framework to return these wastes to the United States is unclear to the committee. Finally, in addition to the HEU wastes from Mo-99 production, Atomic Energy of Canada Limited (AECL) is also storing about 45 kg of HEU that was intended for use for Mo-99 production in the Maple reactors. This material has apparently become surplus in light of AECL’s decision to discontinue work on these reactors (see Chapter 10). At the time the present report was being completed, AECL had not announced whether it would return this HEU to the United States. FINDINGS AND RECOMMENDATIONS The third charge of the statement of task calls for an assessment of the progress that is being made by DOE and others to eliminate all use of HEU in reactor fuel, reactor targets, and medical isotope production facilities. The committee has developed the following findings and recommendations to address this task: The committee finds that DOE-NNSA, in collaboration with ANL/INL and with the assistance of IAEA through the RERTR program, has made substantial progress in converting reactors and targets. In particular, 27 A representative of IRE informed the committee that reprocessing of Mo-99 production wastes to recover HEU is an option for that organization as well if it cannot obtain fresh HEU.
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Medical Isotope Production without Highly Enriched Uranium substantial progress has been made in converting HEU-fueled reactors to LEU fuels. New technologies for LEU-based production (i.e., targets and processing) of Mo-99 have been developed by ANL and tested by some small producers. However, these technologies have yet to be adopted by large-scale producers of Mo-99. Minimization of the commerce in civilian HEU and its use in research reactors worldwide, together with the return of research reactor spent nuclear fuel and HEU waste from isotope production to safe and secure facilities in their countries of origin, will help to reduce proliferation risks. The committee finds that the GTRI has made substantial contributions to these minimization and return goals: The period 1978–2004 was marked by slow but steady progress, whereas progress accelerated during the period 2004 to the present. The committee recommends that the GTRI be continued until research and test reactors worldwide have converted fuel and targets to LEU or permanently shut down and their HEU fuel has been returned to the country from which it originated. Despite these successes, the committee finds that the program faces several challenges. First, the startup and continued operation of the HEU-fueled FRM II reactor in Germany sets an unfortunate precedent for possible future construction of HEU-fueled research reactors. Second, there are 78 HEU-fueled research and test reactors operating throughout the world that are out of scope of GTRI. The majority of these are old and by the end of the current GTRI program their numbers are likely to be much fewer. Nevertheless, from a purely technical perspective, it is difficult to understand why most of these reactors cannot be converted. The committee recommends that DOE-NNSA, in cooperation with IAEA, make an effort to maintain an up-to-date and comprehensive database of the research and test reactors of the world, including large pulse reactors, critical facilities, and reactors with a defense-orientated mission.28 The committee also recommends that these reactors should be investigated to determine if it is feasible to convert them to LEU; if so, they should become in-scope for the program. Finally, the committee finds that converting Mo-99 production worldwide to LEU will continue to be a major challenge for the reasons described in detail elsewhere in this report. Chapter 10 lists some actions that DOE and other parties can take to accelerate the conversion to LEU-based Mo-99 production. The committee recommends that the RERTR increase its focus on eliminating the HEU wastes from Mo-99 production from U.S.-origin HEU, by examining options for downblending this waste or encouraging its return to the United States. 28 These reactors do not include HEU-fueled naval propulsion reactors or related test beds and training reactors.