Plutonium End Game
Managing Global Stocks of Separated Weapons-Usable
Commercial and Surplus Nuclear Weapons Plutonium
Arjun Makhijani
January 2001
Arjun Makhijani
January 2001
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Press Release
Chapter One: Nature of the problem of commercial plutonium
Chapter Two:
A Brief History of Commercial Plutonium
Chapter Three: Assessment of the current situation
Chapter Four: Disposition of US-Russian Surplus Military Plutonium
Chapter Five: Alternative Disposition Options |
Chapter 5: Alternative Disposition OptionsThe most detailed investigations regarding the fate of surplus plutonium have been done in the context of the disposition of surplus military plutonium. However in the past couple of years, disposition of commercial surplus plutonium has also become a more pressing issue, as the costs, proliferation risks, environmental liabilities, and management scandals surrounding reprocessing and MOX use have grown and become more evident due to a variety of factors. Detailed attention has begun to be given to the various options for disposition of commercial plutonium, other that its use as MOX fuel in reactors. Since commercial plutonium is now admitted to be an economic liability even by the US National Academy of Sciences and the British House of Lords Science and Technology Committee,61 it is only logical that the disposition of commercial plutonium should be considered integrally with that of military plutonium Moreover, US-Russian military plutonium disposition is likely to involve Cogéma and BNFL, the very companies that possess the largest stocks of commercial plutonium. These companies have, or could develop with greater facility than most others, the expertise needed to immobilize plutonium in order to put it into non-weapons usable forms. Since the publication of the US National Academy of Sciences study on plutonium disposition in 1994, it has been generally accepted that there will be net costs associated with plutonium disposition, whatever disposition route is taken. In that context, the methods best suited for managing commercial separated plutonium and surplus weapons plutonium should be decided in light of the need to achieve security and environmental goals within a reasonable cost and time. Since commercial plutonium is a liability rather than an asset in the economic sense of these terms, continued commercial reprocessing only exacerbates the economic burden, besides adding to proliferation concerns. It is a huge waste of resources to continue reprocessing even from the point of view of those who believe that plutonium may be a valuable fuel a few decades hence. Such an eventually has receded farther from the horizon over the past two decades. Should it appear imminent and desirable a few decades from now, there will be time enough to re-consider the question. Current world uranium resources are large; they are not going to run out overnight. Continued commercial reprocessing is an unacceptable economic and proliferation gamble that is, moreover, harming the environment without providing any concomitant benefit except to entrenched plutonium bureaucracies that refuse to see the writing on the wall. A halt to reprocessing for a prolonged period or a complete termination of commercial reprocessing programs is an issue that is now more closely linked to plutonium disposition than when the military surplus was the main policy issue under consideration. It is necessary halt commercial reprocessing immediately. That way the stocks of plutonium will not be growing via reprocessing even as precious resources are being expended to reduce surplus military plutonium stocks. In light of this analysis, the actions needed for sound plutonium management and disposition that are consistent with security, environmental and economic criteria can be enunciated as follows:
Three technical issues associated with non-fuel disposition of plutonium impact considerably how the above general ideas would be put into practice:
Isotopic composition of plutonium The only technical advantage of a MOX fuel route for disposition, assuming that reprocessing is halted, is that the isotopic composition of weapon-grade plutonium can be changed to reactor-grade plutonium. But since reactor grade plutonium can also be used to make weapons, if separated, this is not a large advantage in non-proliferation terms. Because immobilization cannot achieve isotopic degradation of weapons grade plutonium, it became an issue in US-Russian negotiations as a point in favor of MOX fuel as the disposition route. However, the problem of the potential re-extraction of plutonium from its immobilized form and its possible re-use by the United States or Russia for weapons purposes can be resolved by simply putting the immobilized plutonium under IAEA safeguards. That would provide a multilateral guarantee that surplus weapons plutonium would never again be re-extracted and used to make nuclear weapons. Spent fuel standard In 1994, the US national Academy of Sciences defined the "spent fuel standard" as the desirable goal for plutonium disposition. By this measure, the barriers to theft and reuse of the plutonium would be comparable to that facing the use of plutonium present in nuclear power reactor spent fuel. For practical purposes, light water reactor spent fuel has been the specific reference material. The spent fuel standard provides measures for:
It is important to remember that the appeal to the spent fuel standard to provide the yardsticks for assessing plutonium disposition standards is based on a negative argument. Since most of the plutonium in the world is contained in light water reactor spent fuel, methods of plutonium disposition that would provide non-proliferation barriers greater than such spent fuel are not justifiable. Thus, the spent fuel standard represents a practical ceiling for plutonium disposition efforts. Whether the spent fuel standard should also constitute a practical floor for evaluating plutonium disposition has not been subjected to comparable scrutiny. A number of factors lead to the conclusion that the actual achievement of the spent fuel standard should be a secondary consideration in the current US-Russian program. For instance, the spent fuel standard does not give adequate weight to the fact that nuclear weapons states, notably the United States and Russia, would be highly unlikely to re-use disposition weapon-grade plutonium in weapons. This is because they have huge available surpluses of separated weapon-grade plutonium due to reductions in nuclear weapons stockpiles that will endure for the foreseeable for the future. Moreover, a principal practical problem that has emerged with the spent fuel standard should be explicitly recognized. The fact that immobilization does not change the isotopic composition of the plutonium has been one of the Russian arguments against immobilization. This has been used to promote the use of plutonium as a reactor fuel in the name of disposition that would meet the spent fuel standard. Had there been no plan to use MOX fuel in breeder reactors and to reprocess MOX spent fuel, this argument would at least have had the merit of consistency. But the US-Russian plutonium agreement allows Russia to reprocess MOX spent fuel after a time as short as ten to fifteen years, re-creating the problem of rising separated plutonium stocks. Further, the agreement also meets the Russian goal of allowing the use of plutonium in breeder reactors. While breeder reactors may be operated in a mode so as to degrade the isotopic composition of the plutonium, they can also be operated so as to improve it. Since there are no long-term restraints on how these reactors would be operated, Russia could, in the long-term, increase its stocks of weapon-grade plutonium under its civilian nuclear power program. This can be accomplished by putting uranium-238 in the "blanket" surrounding the breeder reactor core. The high purity plutonium-239 that can be created in the blanket can then be mixed with reactor-grade plutonium. With sufficient high-purity ("super-grade") plutonium, a large amount of reactor grade plutonium can be converted into weapon-grade plutonium. The practical goal of long-term conversion of weapon-grade plutonium into an immobilized form containing reactor grade plutonium will therefore not be met by the US-Russian plutonium disposition agreement. Unfortunately, the scope of the most recent study of the spent fuel standard by a special panel of the National Academy of Sciences did not include the use of MOX in breeder reactors, even though that is Minatom's preferred option for the Russian use of MOX made from weapon-grade plutonium. The scope of the study was defined by the Office of Fissile Materials Disposition of the Department of Energy.62 A more urgent and realistic goal would be to put plutonium into non-weapons-usable forms for a long period of time in order to:
One problem that has emerged is the potential lack of sufficient cesium-137 to provide a large enough radiation barrier to theft if the plutonium is vitrified with high-level waste. In Europe, the potential insufficiency of cesium-137 arises from that fact that much of the high-level waste generated from reprocessing has already been vitrified. In the United States, the failure of the In-Tank-Precipitation process at the Savannah River Site has created an even more acute question in this regard. This process was designed to separate cesium-137 from a large volume of salt crystals and liquid high-level waste. The cesium would have been added to the vitrification process and provided the radiation barrier that would be a central element of the achievement of the spent fuel standard in the immobilization disposition program. Two broad approaches to address this question have been suggested. One approach, put forward in Germany, is to make non-fuel quality MOX pellets, put them into fuel rods, and then put the fuel rods into canisters together with spent fuel.63 The whole assembly would then have a high radiation barrier to theft. However, the MOX itself would not provide a significant barrier to re-separation of plutonium from the depleted uranium, were the MOX fuel rods to be removed from the spent fuel canister. Another disadvantage of this approach is that it would keep the MOX plants operating for a considerable period of time. It would thereby leave open the possibility of the manufacture of MOX fuel for reactors as well as impure MOX pellets designed for disposition without use as fuel. From a non-proliferation standpoint, it would be preferable to have an approach that eliminated the manufacture of MOX altogether. This can be done with the ceramic immobilization approach in the United States for part of the surplus weapons plutonium. Since the basic process of pressing and sintering is the same as for MOX, but the size and composition of the immobilized product is different, it may be possible to modify existing MOX plants, especially the Sellafield MOX plant, which has not yet been commissioned, to accomplish this. It may also be useful to examine another approach to creating a radiation barrier to theft. Immobilized ceramic pucks can be placed in glass logs without fission products. (Thorium-232 may be added to the ceramic. This would make re-separation of the plutonium more difficult because thorium is chemically analogous to plutonium.) The vitrified canisters can then be placed inside another specially manufactured canister that contains a small amount of cesium-137. This container would therefore have high gamma radiation, but the bulk of materials inside the container would not have significant gamma-emitting materials. The elimination of self-absorption of gamma radiation in the glass log allows a reduction of cesium-137 requirements by about an order of magnitude. According to calculations done at the Savannah River Site, 135 grams of cesium-137 (12,000 curies) could provide a radiation barrier of about 5,000 rad per hour.64 Exposure to such an intense radiation field would result in a lethal radiation dose in about five minutes. Separated cesium-137 is available at the Hanford Site in Washington State. Our view is that achieving the spent fuel standard in all respects is not as crucial as creating sufficient barriers to theft and re-extraction by non-nuclear weapons states and non-state groups. Early completion of disposition should be a high priority, since timeliness is least as important as any other single factor in the achievement of non-proliferation goals. The choice of options will depend on the specific country, decisions regarding the use of existing facilities, availability of storage, the situation regarding the creation of the radiation barrier, and the specific combinations and amounts of commercial and military plutonium that are to be put into non-weapons-usable form. For instance, the options in France and Britain will be affected by their relationships to the US and Russian plutonium disposition programs. This is because BNFL and Cogéma are involved in US surplus plutonium disposition issues directly (in the case of Cogéma) or indirectly, in the case of BNFL, which is the site contractor (via its Westinghouse subsidiary) for the DOE-owned Savannah River Site in South Carolina. Immobilization matrix The current US immobilization plan involves the fabrication of a titanate ceramic into which a small percentage of plutonium as been mixed. The resultant ceramics pucks would be placed in a steel frame and then surrounded by vitrified high-level waste (see below). While the method would accomplish the non-proliferation oriented disposition goals that we have discussed above, there is some question whether it could meet long-term environmental goals. Specifically, glass may disintegrate rather rapidly under the conditions that may prevail in Yucca Mountain, the only repository site now being investigated in the United States.65 Secondly, a titanate ceramic waste form appears to be vastly inferior to zirconium-based compounds (either oxides or other compounds). Damage to the structure of the waste matrix is created by the alpha particles emitted by plutonium in the process of radioactive decay. Such damage appears to be far more rapid and complete with titanate than with some zirconium-based matrices. Preliminary findings from recent research, sponsored by the DOE's own Office of Basic Energy Sciences, and done at the University of Michigan and the DOE's Pacific Northwest and Los Alamos National Laboratories shows that zirconium-based compounds may be highly resistant to radiation damage. The results indicate that the present titanate-based ceramic would be "completely damaged by the radiation in less than 1,000 years ...[while they] will not sustain damage for periods up to 30 million years." The international research team "included scientists at the Australian Nuclear Science and Technology Organization and the Indira Gandhi Centre for Atomic Research in India."66 Moreover, earlier work at the University of New Mexico, indicates that zircons, which are stable natural compounds, may provide the route by which to develop waste forms that could contain long-lived radioactive materials far better than presently proposed matrices. US-Russian plutonium disposition options The main reason that the United States is pursuing a MOX program, so far as stated policy goes, is Minatom's insistence that plutonium is a long-term energy resource that cannot and should not be discarded today as a waste. This Russian objection to immobilization is somewhat spurious since neither the MOX nor the immobilization option require either side to actually construct a repository or to dispose of MOX spent fuel or immobilized plutonium in it. The main interest in Russia seems to be the financial assistance that would be associated with a light water reactor MOX program (which is not a preferred Minatom program) and the creation of an infrastructure for breeder reactor MOX fuel production. Of these factors, the financial is probably the strongest, since Russia does not have the money to build an economy that would be even partly run on breeder reactors. It has only one large breeder reactor in operation today. We believe that a far better negotiating approach would be to immobilize Russian plutonium without requiring its disposal. The US should follow a similar program. The main elements of a Russian-US agreement, possibly with partial financing from western Europe and Japan, could be as follows:
The United States has chosen the "can-in-canister" approach as its preferred immobilization strategy. This involves the mixing of plutonium dioxide with depleted uranium dioxide and non-radioactive ceramic titanates, and then pressing the mixtures into hockey-puck-sized elements that are stacked in a stainless steel container - see Figure 1. Apart from the question of the type of matrix used to contain the plutonium, there is the issue of how to provide a strong external radiation field that would be the main barrier to diversion of the immobilized plutonium, and one of the main barriers to its re-extraction. Under the present DOE plan, a number of these containers would be positioned in a bird-cage arrangement inside the large canisters in which high-level waste is now being vitrified at the Savannah River Site in South Carolina. The plutonium is thus immobilized in a ceramic matrix located in vitrified high-level waste. As we have discussed above, a principal technical hitch in this scheme is that only high-level waste sludge is currently being vitrified, and this fraction of the waste does not contain enough cesium-137 to provide a sufficient radiation barrier. The options are to:
The Russian approach could parallel that adopted in the United States. Early storage of immobilized plutonium under IAEA safeguards (option 3 above) is highly desirable in Russia. Since Russian high-level wastes at the Mayak facility in the southern Urals are in acidic form, it is possible for Russia to immobilize its plutonium via high-level waste vitrification or by creating an external radiation barrier as described in option 1 above. In the latter case, a calcining facility as well as other special facilities would have to be built. A high-level waste vitrification plant has operated at Mayak. A new plant has been built but has not been completed. Russia's commercial separated plutonium is stored at Mayak, while its main military plutonium store appears to be at Tomsk-7. |
Source: Courtesy of T.H. Gould, Lawrence Livermore National Laboratory, Livermore, California
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Making impure MOX that could be put into fuel pins for storage with LEU spent fuel is not an option for the United States or Russia since neither country has a MOX fuel fabrication facility. The option of adding thorium-232 to either the ceramic pucks or to the glass logs needs to be carefully evaluated. Thorium-232 has a decay chain consisting of short-lived decay products that build up to equilibrium in a couple of decades. Thallium-208, one of these decay products, is a very strong gamma emitter. Hence, immobilization with thorium-232 would also provide a durable radiation barrier, though due to technical limitations on thorium loading, it would not physically prevent theft as would be the case with a gamma radiation barrier created by cesium-137. Moreover, thorium is a close chemical analog of plutonium. Hence the addition of thorium would make re-extraction of plutonium from the ceramic pucks far more difficult for non-state groups and for most non-weapons states. The main disadvantage of adding thorium-232 to the immobilization process is that thorium-processing facilities would have to be built in order to remove the decay products before preparing the ceramic powder mix. Such removal is necessary for worker protection, since the ceramic mix would be prepared in a glove box environment, rather than a heavily shielded, robotically operated facility. One way around this problem would be to add thorium into the molten-glass and high-level waste mix. Since high-level waste vitrification is carried out entirely remotely, it would not be necessary to mix the plutonium with the thorium in the process of making plutonium-containing ceramic pucks.68 Yet, the mixing thorium in the glass would add to the complexity of plutonium re-extraction. This strategy may allow for plutonium immobilization in glove box facilities, allowing it to be completed in a relatively short-time. At the same time, shielded facilities could be used for the addition or thorium, making it unnecessary to process thorium solely for the purpose of separating it from its decay products. The United States and Russia should step up their own as well as joint immobilization efforts to ensure that commercial and surplus military plutonium is immobilized as rapidly as is compatible with health and safety, so that it can be put under IAEA safeguards at an early date. In the meantime, both expeditious completion of the storage facility now being built in Russia as well as arrangements for thorough bilateral safeguards of surplus plutonium in both countries is highly desirable. Finally, it is imperative that both countries stop the operation of their reprocessing plants, so as to prevent an increase in separated plutonium stocks even as they are spending resources to immobilize plutonium. Britain The British situation differs from the one in the United States in that Britain has a large scale MOX fuel fabrication facility, the Sellafield MOX Plant (SMP), that could be used for the purpose of disposition. As we have noted, it has been proposed that the SMP facility be used to make impure MOX that could be put in fuel pins. These pins could then be stored with LEU spent fuel, which would provide the radiation barrier. This option has the disadvantage that it would entail the opening of SMP, and enable the production of MOX for use as a fuel, with is attendant adverse non-proliferation consequences. Another possibility is to investigate the conversion of the SMP to fabrication of hockey-puck size plutonium ceramics like those that are to be produced in the United States. This would entail modifications in the sintering furnace and changes in the presses that are used to compress the oxide powders into pellets. However, such a conversion may enable the use of the structure, glove boxes, powder preparation and mixing equipment and much of the other infrastructure associated with the SMP, without allowing for its use for MOX fuel production. This would have the additional advantage of being compatible with US disposition, so that the two programs could reinforce each other in terms of technical experience, safety, cost, etc. However, a detailed study is needed to establish its technical feasibility. A technical study on plutonium immobilization has been started in Britain.69 It may also be possible to combine the option of storing immobilized plutonium with LEU spent fuel with the option of immobilizing it in sizes that are different from those of spent fuel rods. Assemblies of such off-size immobilized plutonium rods could then be stored interspersed with spent fuel assemblies. One advantage of such a approach would be that if existing MOX plants are converted to immobilization, it would be far more difficult technically, politically, and financially, to re-convert them to MOX manufacture. The level of protection against re-extraction would be somewhat lower because the immobilized plutonium assemblies would be more readily distinguishable from the spent fuel assemblies. However, this lowering of the re-extraction barrier would be marginal relative to the high barrier provided by the external gamma radiation emanating from the spent fuel. Further, as discussed above, the barrier to re-extraction from the ceramic pucks could be increased by the addition of thorium-232 during the immobilization process. In this case, thorium process facilities would have to be built or existing facilities converted to thorium processing. The overall non-proliferation merit of schemes that avoid the use of MOX facilities as such is far greater than that of the fabrication of impure MOX for storage with spent fuel. Plutonium immobilization in forms other than MOX-fuel-type forms would provide further incentive to ending MOX fuel use and to ending commercial reprocessing. Specifically it would decrease the incentive for keeping the THORP and the UP2 and UP3 reprocessing plants. France France separates far more commercial plutonium than all other countries combined. It also has the largest MOX fuel fabrication facilities and is the world's principal supplier of MOX both inside and outside France. However, even the French government now acknowledges that reprocessing MOX fuel use even in a limited number of reactors has raised and will continue to raise the price of electricity compared to the option of LEU fuel only (see Chapter 3). The financial incentive to shut down reprocessing and MOX fuel production has heretofore been diminished by large foreign reprocessing and MOX fuel fabrication contracts. Further, BNFL's troubles arising from the MOX data fabrication scandal may provide greater business opportunities to Cogéma to make MOX fuel for BNFL's Japanese customers. The U.S.-Russian MOX fuel agreement also promises to further entrench Cogéma in its course of reprocessing and MOX fuel use, and provides it with additional leverage in the internal economic and political discourse in France. This is because these foreign relationships are a source of export revenues. However, with the planned phase out of nuclear power in Germany and the high-level of resistance to MOX fuel use in Japan after the BNFL scandal and the Tokaimura criticality accident, France's foreign plutonium business is in some jeopardy, notably in the long-term. France again seems to be at a watershed with respect to plutonium fuel use. Will it continue to spend billions of dollars chasing a plutonium mirage, or will it end reprocessing? How the La Hague facility would shut down its reprocessing plants and transition into plutonium management and immobilization is more complex than just the problems of technical conversion. French nuclear waste law prohibits the storage of foreign spent fuel in France, but allows its import for reprocessing. The vitrified high-level wastes and as well as intermediate level wastes are to be sent back. German nuclear power plants do not have enough storage space for spent fuel, complicating the problem of a practical phase out strategy for nuclear power plants, as well as a termination of reprocessing contracts. The present general approach is to build on-site storage, as well as storage for returned vitrified glass logs from France. Further compounding difficulties is the fact that most high-level waste in France has already been vitrified. This presents issues similar those in the United States and Britain arising from a shortage of gamma-emitting fission products to provide a radiation barrier. Finally, the conversion of existing MOX facilities in France to immobilization will pose greater problems (if it can be done at all) since they have already been commissioned for plutonium fuel fabrication. Broadly speaking the options for immobilizing plutonium are similar in France, but it is likely that new immobilization facilities will have to be built (as is also the case with the United States and Russia). On the positive side France has far more experience with operation of large scale MOX fuel fabrication that could enable it to design and operate plutonium immobilization facilities more rapidly that other countries.
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Institute for Energy and Environmental ResearchJanuary 2001
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(continued from Chapter Four) 61. NAS 1994, p. 3 and House of Lords 1999, pp. 63-66. 62. NAS 2000, p. 2 and Appendix A. 63. Kueppers et al. 1999. 64. John Plodinec, personal telephone communication to Noah Sachs, November 28, 1994. See Makhijani and Makhijani 1995. 65. Makhijani 1991. 66. August 9, 2000, University of Michigan, College of Engineering press release. Contact Janet C. Harvey-Clark, janethc@engin.umich.ed 67. See Makhijani and Makhijani 1995 for details. 68. High-level waste contains gamma-emitting radionuclides and must be processed remotely. Plutonium is mainly an alpha-radiation emitter. Since alpha radiation is not penetrating - a piece of paper can stop it - plutonium processing generally requires only glove box use for worker protection purposes. 69. David Lowry, personal e-mail to Arjun Makhijani, 8 August 2000. |