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1

Disposition of High-Level Waste and Spent Nuclear Fuel: An Overview of the Societal and Technical Challenges

The development and use of nuclear technology, which began in the early 1940s, has produced a substantial inventory of radioactive waste— material with no current or currently known future use. The most radioactive fraction of this waste must be isolated from humans and the environment, because it produces hazardous levels of ionizing radiation that may persist for a long period of time and because some components of this waste can be used to make nuclear weapons. Sidebar 1.1 describes the types and origins of this waste. For convenience, all such waste materials are referred to collectively as high-level waste (HLW) in this report, with the more precise terms used only as necessary to avoid ambiguity.

Sidebar 1.1: What is High-Level Waste and Where Does it Come From?

High-level waste, spent nuclear fuel, highly enriched uranium, and plutonium are the radioactive materials of concern in this report. Because all are related to nuclear processes, they have some similarities but also have significant differences: how they are produced, what is in them, and what hazards—for safety and security—they represent. The key characteristics of relevance when considering disposition alternatives are the intensity of the radiation emitted, the rate at which the intensity decreases, and the ease with which the material can be misused in nuclear weapons. The most relevant characteristic that these materials have in common is that all represent a hazard for very long times into the future, unless measures are taken to isolate them from the human environment.

After uranium is made into fuel for a nuclear reactor, it is used to produce energy. In the process, some of the uranium fissions—splits—producing energy



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Page 7 1 Disposition of High-Level Waste and Spent Nuclear Fuel: An Overview of the Societal and Technical Challenges The development and use of nuclear technology, which began in the early 1940s, has produced a substantial inventory of radioactive waste— material with no current or currently known future use. The most radioactive fraction of this waste must be isolated from humans and the environment, because it produces hazardous levels of ionizing radiation that may persist for a long period of time and because some components of this waste can be used to make nuclear weapons. Sidebar 1.1 describes the types and origins of this waste. For convenience, all such waste materials are referred to collectively as high-level waste (HLW) in this report, with the more precise terms used only as necessary to avoid ambiguity. Sidebar 1.1: What is High-Level Waste and Where Does it Come From? High-level waste, spent nuclear fuel, highly enriched uranium, and plutonium are the radioactive materials of concern in this report. Because all are related to nuclear processes, they have some similarities but also have significant differences: how they are produced, what is in them, and what hazards—for safety and security—they represent. The key characteristics of relevance when considering disposition alternatives are the intensity of the radiation emitted, the rate at which the intensity decreases, and the ease with which the material can be misused in nuclear weapons. The most relevant characteristic that these materials have in common is that all represent a hazard for very long times into the future, unless measures are taken to isolate them from the human environment. After uranium is made into fuel for a nuclear reactor, it is used to produce energy. In the process, some of the uranium fissions—splits—producing energy

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Page 8 and fission products. Another portion of the uranium is transformed into plutonium, some of which also fissions. When the fuel is removed from the reactor it is labeled spent nuclear fuel (SNF). This SNF is highly radioactive from the decay of the fission products, is still generating heat, and contains some plutonium as well as unconsumed uranium. In the United States, the Department of Energy maintains the label SNF for this spent fuel and does not formally classify it as high-level waste. The U.S. Nuclear Regulatory Commission does classify spent nuclear fuel as HLW. Most countries do not count SNF as high-level waste. The distinction is maintained because of the uranium and plutonium in SNF, which can be used for further energy production or, as discussed later, for nuclear weapons. The HLW, when SNF is not included, does not contain very much plutonium or uranium and is therefore not a proliferation concern, and is in that sense not a security threat. To extract plutonium and uranium from SNF, chemical or electrometallurgical processes are used to separate the fission products with high levels of radiation and heat generation, leaving the plutonium and uranium with little radioactivity or heat generation. The fission product waste stream is labeled HLW in all countries. This material represents a health hazard because of the radiation, as well as the toxic properties of some of the materials. Security issues relate primarily to the ability to make nuclear weapons. Such weapons use highly enriched uranium (HEU), which is enriched in uranium-235, and plutonium. Manufacture of most nuclear fuel does not produce HEU, although some special fuel does use more HEU than other nuclear fuels. Plutonium comes from reactor operations. What is called “Weapons-grade” plutonium is manufactured by running a reactor in a very short cycle, extracting the fuel, processing the fuel, and extracting the plutonium. If the reactor is run in a normal energy-producing cycle, the resulting plutonium has a lower concentration of the most attractive isotope, plutonium-239, and higher concentrations of other isotopes, which make handling the material more difficult and make it less attractive for bomb manufacture. As the United States and Russia (and countries of the former Soviet Union) moved forward in arms control treaty negotiations, each country dismantled large numbers of nuclear weapons, resulting in an increasing amount of HEU and weapons-grade plutonium being stored. “As a result [of these treaties], 50 or more metric tons of plutonium on each side are expected to become surplus to military needs, along with hundreds of tons of highly enriched uranium. . . . The existence of this surplus material constitutes a clear and present danger to national and international security” (NAS, 1994, p. 1). Some have argued that reactor SNF is not a serious security threat because reactor-grade plutonium differs from weapons-grade plutonium. However, “[p]lutonium customarily used in nuclear weapons (weapons-grade plutonium) and plutonium separated from spent reactor fuel (reactor-grade plutonium) have different isotopic compositions. Plutonium of virtually any isotopic composition, however, can be used to make nuclear weapons. . . . Thus, the difference in proliferation risk posed by separated weapons-grade plutonium and separated reactor-grade plutonium is small in comparison to the difference between sepa-rated plutonium of any grade and unseparated material in spent fuel” (NAS, 1994, p. 4). Another argument is that only separated plutonium is of concern, not SNF, but “[s]pent fuel poses proliferation risks that are initially far lower, but increase with time as the intense radioactivity that provides the most important barrier to recovery of this material decays” (NAS, 1994, p. 205).

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Page 9 “Because plutonium in spent fuel or glass logs incorporating high-level wastes still entails a risk of weapons use, and because the barrier to such use diminishes with time as the radioactivity decays, consideration of further steps to reduce the long-term proliferation risks of such materials is required, regardless of what option is chosen for disposition of weapons plutonium” (NAS, 1994, p.2). The National Research Council's (NRC's) report, The Disposal of Radioactive Waste on Land (NRC, 1957; see Sidebar 1.2), which was written at the request of the U.S. Atomic Energy Commission, marked the beginning of a decades-long process, still under way, in which governments in the United States and elsewhere have sought to identify disposal sites for HLW, including the effort that is now under way at Yucca Mountain, Nevada. Repository research and siting efforts are under way in many other countries as well, most notably, Belgium, China, Finland, France, Germany, Japan, Russia, Sweden, and Switzerland. Additionally, Canada, Italy, Mexico, the Netherlands, Taiwan, South Korea, Spain, and the United Kingdom have storage programs for their HLW. Moreover, HLW in need of safe management is also located in nations that are part of the former Soviet Union, in countries having Soviet-designed nuclear power reactors, and in other countries. Figure 1.1 illustrates the general concept of a geological repository. ~ enlarge ~ Figure 1-1 Deep geological repository concept.

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Page 10 Many national programs are seeking improved methods for addressing the safe and responsible management of HLW. Some countries have begun a phased approach to repository development, while others have suspended their programs until some later date when, it is hoped, advancements in knowledge will allow more informed decisions to be made. In the United States, for example, the U.S. Department of Energy is considering a plan for a HLW repository at Yucca Mountain that would be designed for ultimate closure (disposal) but would provide the capability to delay for centuries, or even indefinitely, the date of actual closure (see Sidebar 1.3 ). The final decision on closure would therefore be made by a future generation. In Canada, a federally appointed panel has recommended that the government postpone the search for a repository site until broad public acceptance of the geological isolation approach has been achieved. In Germany, there has been intense public opposition to moving spent fuel to an interim storage facility at Gorleben, the site of the German candidate repository, and the decision on whether to proceed with development of a repository at Gorleben has been delayed. In the United Kingdom, a House of Lords committee conducted a full-scale inquiry into the management and disposal of radioactive wastes after a government decision to cancel a proposed underground research laboratory project at Sellafield. Spain has halted its siting program, and in Hol- Sidebar 1.2: The Changing Context of Geological Disposal Many changes have occurred in practices and policies for waste disposal since publication of The Disposal of Radioactive Waste on Land (NRC, 1957). Particularly important is the composition of the accumulating inventory of HLW. In the 1950s and 1960s, it was widely assumed that essentially all spent nuclear fuel (SNF) would be reprocessed to recover uranium and plutonium. Today, the United States and some other nations have established national policies not to reprocess SNF, but rather to dispose of it directly. England and France have built and still operate reprocessing facilities; Japan has a reprocessing facility under development and has also sent its SNF to England and France for reprocessing; and Russia currently is reprocessing some of its SNF. Germany, Belgium, Switzerland, and the Netherlands have reprocessing contracts with France and the United Kingdom. Some plutonium produced from reprocessing facilities is recycled in lightwater reactors, and the remainder is stockpiled. It has greatly diminished value as a reactor fuel because there are plentiful supplies of uranium on world markets and because the technology of fast breeder reactors, which need plutonium as fuel, has not been developed to reach economical feasibility. Plutonium is also viewed as highly dangerous because it can be used to fabricate nuclear explosives (see Sidebar 1.1 ). The United States and Russia now have sizable inventories of plutonium from dismantling nuclear weapons that both nations have declared to be surplus (NAS, 1994). This surplus plutonium may be burned in current nuclear reactors, or it may be designated as waste.

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Page 11 land all work on specific disposal projects has been formally suspended for 100 years. Chapter 4 of this report provides a summary of the status of national HLW programs. In the midst of this general picture of forced or planned delays in repository programs, there are some more positive examples. In the United States, the Waste Isolation Pilot Plant (WIPP) has gone into operation as the first geological repository designed for disposal of transuranic waste (see Sidebar 4.1 ). 1 A community in Finland has agreed to host a HLW repository, and application has been made for a siting permit. The low- and intermediate-level waste programs in Sweden and Finland have been successful, and the Swedish HLW program is advancing, although more slowly than originally planned. Repository programs have not moved ahead as they were expected to by the technical community and by the political leadership that has sought advice from the technical community on management of HLW. In many countries, when—and even if—the country will move ahead toward geological disposal are now open questions (NEA, 1999a). QUESTIONS TO BE ADDRESSED IN THIS REPORT The committee used the following seven questions to frame the discussions at its November 1999 workshop ( Appendix B ) and to frame the deliberations that led to this report: 1. How can safety be assured for HLW? 2. How can safety and security against human actions be assured for HLW? 3. What are the inherent limits to assuring safety and security by geological repositories or by surface storage? 4. Why has there not been more progress toward geological disposal? 5. Are there available alternatives to geological disposition or surface storage? 6. Do national programs have to choose now between geological repositories and surface storage? 7. Are new initiatives needed in international cooperation? These issues are discussed briefly below to set the context for the more detailed discussions that appear in subsequent chapters of this report. 1 The U.S. government defines transuranic waste as waste that is not HLW but contains alpha-emitting isotopes that have atomic numbers greater than 92 and half-lives greater than 20 years in concentrations that exceed 100 nanocuries per gram. This waste is comprised primarily of materials contaminated with plutonium and other actinides from weapons production activities. Transuranic waste is considered to be a component of long-lived intermediate-level waste or “alpha-bearing” waste in other countries.

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Page 12 Sidebar 1.3: What is the Difference between Disposal and Disposition? The committee uses the terms disposition and disposal in very precise ways in this report, as illustrated by the figure below. The term disposition is used to describe the active management of radioactive waste, either in distributed or centralized storage facilities located at or near the earth's surface, or in yet unsealed underground geological repositories designed for permanent isolation of waste. The term disposal denotes an end to the need for reliance on active management for assuring safety and security of the waste. The figure below illustrates some of the attributes of facilities designed for disposition or disposal of radioactive waste. Facilities designed for disposition require an ongoing vigilance and commitment of resources by society to isolate the waste. Because these facilities are designed to allow for retrieval of the waste, society is able to keep its options open in terms of how waste could be managed in the future. Properly designed disposal facilities, on the other hand, provide safety and security without active management, thus freeing society from future resource commitments, although society would probably maintain vigilance through activities such as long-term monitoring. Disposal facilities are also characterized by a decreasing degree of reversibility. Although a closed and sealed disposal facility could, in principle, be opened and the waste retrieved, such actions could be costly and would require care to avoid exposing workers to high doses of radiation. The bottom arrow on the figure illustrates one of the important conclusions of this report: namely, the committee's expectation that, with time, most national programs will move from a reliance on disposition to disposal. As discussed elsewhere in this report, however, the time scale for this transition may be decades to centuries. ~ enlarge ~

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Page 13 How Can Safety Be Assured for HLW? Safe management of HLW requires the containment of radioactive materials so that they do not impact adversely on human or environmental health. Safety has been a paramount criterion since the initial studies on HLW management. The summary of the 1957 NRC report states, “Unlike the disposal of any other type of waste, the hazard related to radioactive waste is so great that no element of doubt should be allowed to exist regarding safety” (NRC, 1957, p. 3). 2 Assuring that any releases of radioactivity from a repository will fall within acceptable limits has continued to be a major focus of discussion in the planning of geological repositories in the United States and in other countries. The problem of assuring safety was considered initially by many of those involved in development of geological repositories to be closely linked to the selection of rock type. The 1957 NRC report found salt deposits to be promising, but did not recommend salt deposits without qualification. For disposal of liquid waste as contemplated at that time, the report noted problems with salt such as the structural weakness of salt cavities, and recommended a research program for further investigation. The report noted as the “second most promising method” the formation of “a silicate brick or slag which would hold all elements of the waste in virtually insoluble blocks” (NRC, 1957, p. 5). Thus, the 1957 report considered, as an alternative or supplement to finding a favorable geological setting, the development of an engineered barrier that would prevent radioactive materials from migrating into the geological environment from the original containment structure. More than four decades later, many national programs have carried out extensive investigations of a variety of rock types and geological settings as candidates for geological repositories. 3 Much is known about the potential performance of candidate geological settings and engineered barriers, but the situation is now widely recognized to be more complex than originally expected. An important approach developed to reduce the impact of this complexity and of the resulting uncertainties is to employ multiple barrier systems, with engineered and geological barriers working together to give a robust overall safety system. A robust approach to 2 This quote has been included as evidence that the authors of the 1957 NRC report regarded assurance of safety as a paramount goal. The current committee also regards assurance of safety as a paramount goal, but it believes that the criterion “no element of doubt should be allowed to exist” is potentially misleading, given the complexities and inherent uncertainties in predicting events that could lead to the release of radioactivity. See the discussion later in this chapter, “What Are the Inherent Limits to Assuring Safety and Security by Geological Repositories or by Surface Storage?” 3 Deep seabed disposal also has been proposed as providing isolation. This is discussed in Chapter 7 .

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Page 14 dealing with uncertainties is particularly necessary because of the long time scales to be considered. The radioactivity of most fission products lasts less than a thousand years, but radioactive decay for actinides such as plutonium and neptunium takes place over a much longer time, up to millions of years. Four decades of experience show that surface storage facilities can provide secure containment, as long as the storage facilities are maintained and managed adequately to assure containment integrity. Maintenance and control of storage facilities by responsible institutions for periods up to a few centuries is considered reasonable (IAEA, 1999). There are no technical reasons why such facilities could not be rebuilt periodically, provided adequate resources are allocated for this purpose, technical expertise is maintained, and the inventories remain of a manageable size. Technical means to evaluate and demonstrate safety are discussed in Chapter 6 of this report. How Can Safety and Security Against Human Actions Be Assured for HLW? Human intrusion into a repository and the consequent release of radioactivity could happen inadvertently. It must be expected that humans will continue to drill into and mine the earth to search for and recover a variety of materials that a future society may find valuable. It is difficult to anticipate how effective warning signs or other measures might be in alerting future miners and drillers that they could encounter HLW at a repository site established centuries or millennia before their time or whether such warnings would be necessary. Inadvertent human intrusion into a repository usually has been considered only as a safety issue. In 1995, the Nuclear Energy Agency (NEA) published a recommendation that deliberate intrusion should not be covered in repository safety analysis (NEA, 1995b). Most of the repositories being contemplated for current national programs could be opened by a future generation using today's mining technology—for example, for future utilization of uranium and plutonium as an energy resource. The most serious threat from deliberate intrusion may be the recovery of materials to make nuclear weapons. In this case, the visibility of such intrusion may be important. The committee uses the term “security” as a parallel term to safety to highlight the problem of human actions that could compromise safe HLW management in a different way, namely by the retrieval of fissionable components of HLW such as plutonium with the intent of making nuclear weapons, or by the dispersal of highly radioactive materials over populated areas as an act of terrorism. The risk of human intrusion, including both inadvertent intrusion and deliberate intrusion, is a concern for both waste storage and underground disposal.

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Page 15 These issues also are discussed in Chapter 6 and Chapter 7 . What Are the Inherent Limits to Assuring Safety and Security by Geological Repositories or by Surface Storage? During the 1990s, experience in many national programs that investigated geological disposal demonstrated the need for flexibility and for accommodating the inherent limitations in the information that scientific investigation can provide about the geological setting and the durability of engineered barriers. These important limitations in scientific understanding comprise “scientific uncertainty,” which can be reduced but not entirely eliminated by further research. This term will be used frequently throughout the report, with the committee's recognition that the relative importance of different uncertainties lies in their potential consequences. All are not equally important. A robust safety system with built-in redundancy can reduce the consequences of uncertainties in the performance of individual components. Current scientific and technical knowledge might be interpreted as leading to pessimism that “every element of doubt” (the phrase used in the 1957 NRC report) regarding the safety of HLW can be eliminated. However, extensive analysis of uncertainties may allow the overall doubts to be resolved. The British philosopher Francis Bacon wrote in 1605: If a man will begin with certainties, he shall end in doubts; but if he will be content to begin with doubts he shall end in certainties. Today, it is understood within the waste management community that the design and assurance of the safety of geological repositories must be a carefully considered exercise in making decisions in the face of scientific uncertainty. For long-term surface storage, the uncertainties are of a different character: they involve uncertainties as to whether the needed commitment of the necessary resources and vigilance will be maintained by society in the distant future. Chapter 6 introduces concepts from risk analysis and decision making in the face of uncertainty (see Sidebar 1.4 ). Characterizing uncertainties is also discussed in Chapter 6 and Chapter 8. Why Has There Not Been More Progress Toward Geological Disposal? The technical challenges in designing and constructing a geological repository for HLW and assuring its safety have proved to be larger than many experts originally expected. Surface storage is much easier to construct than a geological repository, but ongoing maintenance is required. In addition, there are a number of important societal issues. In particular, radioactive waste is feared by many members of the general public, and

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Page 16 Sidebar 1.4: Risk and Safety Many areas of science and public policy are concerned with assuring public health and safety. Modern methods for analysis of safety involve assessing both the likelihood and the severity of situations involving harm: to humans, to property, or to aspects of the environment. Such analysis is often described as “risk analysis.” in this context, “risk” is defined as a description of possible harm, in terms of both the probability of occurrence and the severity of the consequences. In some public health and safety contexts, the probability of occurrence can be obtained from available statistical information. However, in many contexts, such statistical information is not available. Judgments about probability of occurrence must be based on other types of information, such as extrapolation from observed data or predictive use of scientific models. For example, the risk of developing cancer as a result of exposure to low doses of ionizing radiation (from radioactive waste or from other sources) cannot be observed directly from epidemiological data, but rather is estimated from data on increased cancer incidence following exposure to higher doses of ionizing radiation. (For details, see the series of NRC reports “Biological Effects of Ionizing Radiation” [BEIR].) Broader discussions of risk and the use of risk analysis can be found in recent NRC reports such as Understanding Risk: Informing Decisions in a Democratic Society (NRC, 1996a), Science and Judgment in Risk Assessment (NRC, 1994b), and Improving Risk Communication (NRC, 1989b). An historical overview of the development of the concept of risk is found in Bernstein (1996). A good modern overview on risk and uncertainty is found in Morgan and Henrion (1990). there is a distrust of experts and organizations that manage this waste. Often, national programs have regarded management of HLW as a purely technical problem, rather than both a technical and a societal problem (see Sidebar 1.5 ). As a result, the institutional and decisional processes often have been poorly equipped to deal with the societal challenges encountered. Meeting the societal challenges involves achieving better understanding of the answers to questions such as the following: 1. What explains the public concerns about the management of HLW? 2. How have such concerns been addressed in national waste management programs and with what results? 3. What lessons have been learned, and what new approaches are emerging, to gain increased public support and confidence in the making and implementation of decisions concerning the storage and disposal of HLW? The status of national programs is summarized in Chapter 4 . Chapter 5 discusses public perceptions and attitudes toward radioactive waste, particularly HLW. Chapter 5 and Chapter 8 also address how public participation and public confidence might be enhanced through broader, more transparent processes for decision making and for implementation of decisions on management of HLW.

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Page 17 Sidebar 1.5: Who are the Public and the Technical Community? HLW is an example of a public policy issue in which there is a widespread perception of a division between the public and technologists. On one side appear to be the technical and scientific experts in the technologies and processes involved with HLW. These experts include not only physical scientists, but also engineers and managers, workers in the nuclear industry, social scientists, and policymakers who have engaged themselves in radioactive waste issues. Members of the public, on the other side, may lack specialized training or experience, but nevertheless many have genuine interest—and sometimes concerns or fears— about radioactive waste. In developing this report, the committee recognized that both groups are heterogeneous in their knowledge and in their feelings, perceptions, and judgments about HLW. The word “community” should not be taken to imply consensus. Also, by its choice of terminology, the committee does not wish to imply that any interested parties are, or should be, excluded as participants in the public policy process. In this sense, all persons are members of the public, all should be enabled to engage in discussion and debate, and all can help in implementing recommendations to address the challenges posed by HLW. A continuing theme in the 1999 workshop that initiated this report and in the committee's subsequent discussions was encouragement of openness and participation in discussion and debate about both societal and technical challenges. With the above in mind, the committee refers in this report to “the technical and scientific community” or “the technical community” and to “the public,” “segments of the public,” or “members of the public” depending on which term best fits the context. Are There Available Alternatives to Geological Disposition or Surface Storage? A considerable amount of study has been devoted over many years to alternatives to geological disposal of HLW. Among those that have received the most consideration are disposal in the seabed, partitioning and transmutation 4 (P&T) of long-lived isotopes, and continued surface storage. P&T can reduce the amount of actinides and long-lived fission products, but its actual efficiency in practice is unknown, and inevitably some radioactive waste will remain. This waste will require management in a geological repository or in surface facilities. These alternatives are discussed in Chapter 7. 4 According to this concept, which is discussed in Chapter 7 , long-lived isotopes would be separated (“partitioned”) from other waste components and changed (“transmuted”) into other, shorter-lived isotopes by a nuclear process, for example, neutron irradiation.

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Page 18 Do National Programs Have to Choose Now Between Geological Repositories and Surface Storage? Many discussions of the need for geological repositories have taken the position that current generations have an ethical imperative to avoid imposing the burden of ongoing surveillance and management and, ultimately, disposal on future generations. At a time when many considered that assurance of the safety of geological repositories would easily be accomplished and demonstrated, this objective was accepted widely. As difficulties have emerged both with making the technical case for repository safety and with gaining public acceptance of repository programs, the feasibility of this objective has been increasingly questioned. The argument is predicated on acceptance of the assumption that a sealed repository represents less of a future burden than stored wastes for which one is still free to choose a disposal option. Many parties within the international HLW community now are considering the merits of a strategy involving emplacement of HLW deep underground in a facility designed for permanent closure but with the intent to carry out monitoring for a considerable period of time with an ongoing possibility of retrieval, as opposed to a program that involves relatively prompt closure of a repository and the absence of planned activities thereafter. Several factors motivate ongoing study and monitoring rather than expediting repository closure as soon as the HLW can be emplaced. First, active monitoring of the response of the geological site and of the engineered barriers to the waste may lead to adjustments to improve the robustness of the containment system. Second, provisions for ongoing monitoring may be viewed by some members of the public as preferable, so that if very unlikely failures in containment or unexpected events should occur at the repository, effective and timely action can be taken to avoid releases of radioactivity into the biosphere. Third, retrievability may become desirable in the future because of the energy value of components such as uranium and plutonium in spent fuel. The counter-arguments are that safe disposal is thought already to be feasible, and that delaying closure for a long time presents a greater hazard. Retrieval from a closed geological repository remains, in principle, possible for a very long time, although it may be comparable in cost to repository construction after the repository has been closed. These issues are discussed further in Chapter 6 and Chapter 7. Are New Initiatives Needed in International Cooperation? Most of the planning of HLW management has been through individual national programs. Most nations with commercial nuclear power reactors have a nuclear waste program or have plans to establish such a

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Page 19 program in the near future. The concept underlying these national programs is that a nation with commercial nuclear reactors will retain its own HLW, either in the form of spent fuel or as the waste residue from reprocessing, and will dispose of this waste in its own territory. The United States and several European nations are far along in planning HLW repositories, but no country has approved a design and commenced construction, although the United States has started operation of a geological repository for long-lived transuranic intermediate-level waste (the Waste Isolation Pilot Plant, see Sidebar 4.1). The national HLW programs regularly share technical data and the results of ongoing scientific research, and many scientific experts participate in multiple national programs. International conferences are held regularly, and international organizations such as the NEA, the International Atomic Energy Agency, and the European Union have promoted consensus building on appropriate principles and technology for a HLW program. Several factors suggest that it may be appropriate to increase the extent of international cooperation on HLW. The motivating factors and potential new initiatives are discussed in Chapter 9 .