Executive Summary

With the end of the Cold War, many tens of tons of weapons plutonium (WPu) and hundreds of tons of highly enriched uranium (HEU) are expected to be declared surplus to U.S. and Russian military needs. These materials are the essential ingredients of nuclear weapons, and limits on access to them are the primary technical barrier to nuclear proliferation. The existence of large excess stocks of these materials poses a clear and present danger to national and international security.

The report of this panel's parent committee (NAS 1994) recommended an array of steps to reduce this danger, including: verified declarations of total stocks of warheads and fissile materials; bilateral monitoring of warhead dismantlement; secure interim storage of the nuclear-explosive materials resulting from dismantlement, under bilateral and (as quickly as possible) international safeguards; and disposition steps beyond interim storage, designed to make it more difficult to reuse these materials in weapons. The steps beyond interim storage are much less challenging for HEU, which can be “denatured" by blending with natural or depleted uranium, than for WPu, for which no counterpart to this straightforward denaturing process exists. The work of this panel, which supported the parent committee and was reflected in the committee's report, has been confined to disposition of WPu beyond interim storage and, more specifically, to measures that involve irradiation of the plutonium in nuclear reactors or its immobilization with reactor wastes.

The primary motivation of the U.S. government in its search for the best approach to disposition of excess WPu is to minimize the security risks posed



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Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options Executive Summary With the end of the Cold War, many tens of tons of weapons plutonium (WPu) and hundreds of tons of highly enriched uranium (HEU) are expected to be declared surplus to U.S. and Russian military needs. These materials are the essential ingredients of nuclear weapons, and limits on access to them are the primary technical barrier to nuclear proliferation. The existence of large excess stocks of these materials poses a clear and present danger to national and international security. The report of this panel's parent committee (NAS 1994) recommended an array of steps to reduce this danger, including: verified declarations of total stocks of warheads and fissile materials; bilateral monitoring of warhead dismantlement; secure interim storage of the nuclear-explosive materials resulting from dismantlement, under bilateral and (as quickly as possible) international safeguards; and disposition steps beyond interim storage, designed to make it more difficult to reuse these materials in weapons. The steps beyond interim storage are much less challenging for HEU, which can be “denatured" by blending with natural or depleted uranium, than for WPu, for which no counterpart to this straightforward denaturing process exists. The work of this panel, which supported the parent committee and was reflected in the committee's report, has been confined to disposition of WPu beyond interim storage and, more specifically, to measures that involve irradiation of the plutonium in nuclear reactors or its immobilization with reactor wastes. The primary motivation of the U.S. government in its search for the best approach to disposition of excess WPu is to minimize the security risks posed

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Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options by this material. As long as this material remains in readily weapon-usable form, it will: continue to be vulnerable to theft (by parties other than the possessor state) and diversion (by the possessor state) for use in nuclear weapons (which we call the direct risks); send the signal that a reversal of current arms reductions remains possible, with negative consequences for arms reduction and nonproliferation efforts (the indirect risks). The timing of disposition options is crucial to minimizing both types of risks. Minimizing the time until the start of operations to transform the surplus WPu into forms less easily used for weapons, and minimizing the time until this transformation is completed, are of obvious value in reducing the direct risks of theft and diversion. An expeditious approach reduces the indirect risks, moreover, by signaling commitment to irreversible arms reductions and seriousness in addressing proliferation hazards. While the direct risks are significantly greater in the former Soviet Union, under current economic and political circumstances, than in the United States, the indirect risks apply equally to both countries. To reduce the risks in both categories, the two countries should proceed expeditiously, and more or less in parallel, with programs of WPu disposition that move beyond the status quo—guarded interim storage of plutonium "pits" in the form in which they emerge from weapon dismantlement—to make it significantly more difficult for this plutonium to be reused in weapons by the original possessor state or by others. In considering the options for using irradiation in nuclear reactors or immobilization with reactor wastes to provide such barriers, the panel has addressed, on a comparative basis, technological readiness, institutional requirements, economics, and environment, safety, and health. We have given the greatest weight, however, to the security characteristics of the various options—their capacity to reduce rapidly the direct and indirect security risks posed by prolonged storage of the plutonium as pits, while minimizing any new security risks arising from the disposition options themselves. (The task of comparing those long-term disposition options within the panel's purview with other options, as well as the task of comparing all these options with indefinite storage, was left to the parent committee.) THE SPENT FUEL STANDARD The panel recommends that the goal for WPu disposition operations to be undertaken in the next few decades should be to meet what this panel and the parent committee call the "spent fuel standard." This means making the excess WPu roughly as inaccessible for weapons use as the much larger and growing

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Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options quantity of plutonium in spent fuel from commercial nuclear power reactors.1 The "reactor-grade" plutonium found in commercial spent fuel, while it could be used to make nuclear bombs (NAS 1994, pp. 32-33), poses much smaller risks than separated plutonium in this regard because of the mass, bulk, and intense radiation field of the spent fuel assemblies and because of the additional technical sophistication and resources required for chemical separation of the spent fuel plutonium from the accompanying fission products and uranium. Options for the disposition of WPu that leave it more accessible than the plutonium in spent reactor fuel would mean that the WPu would continue to pose a unique safeguards problem indefinitely. Conversely, accepting substantial costs, complexities, risks, and delays in order to go beyond the spent fuel standard to make the WPu significantly less accessible for weapons use than the plutonium in commercial spent fuel would not be justified unless the accessibility of the global stock of plutonium in spent fuel were to be similarly reduced. Promising and Unpromising Options for Meeting the Spent Fuel Standard Two options have emerged from the panel's investigations as the most promising ones for the timely disposition of excess WPu to the spent fuel standard: the current-reactor/spent-fuel option would use light-water reactors (LWRs) or Canadian deuterium-uranium (CANDU) reactors of currently operating types or evolutionary adaptations of them, employing mixed-oxide (MOX) fuel in a once-through mode, to embed the WPu in spent fuel similar to the larger quantity of such fuel that will exist in any case from ordinary nuclear electricity generation; the vitrification-with-wastes option would immobilize the WPu together with intensely radioactive fission products in heavy glass logs of the type planned for use in the immobilization of defense high-level wastes. Under current U.S. policy, the ultimate fate of either of these waste forms is expected to be a geologic repository. Our conclusion that these two options are the most attractive ones in our purview does not depend, however, on emplacement of the waste forms in a particular repository or by a particular time, or 1   When currently planned arms reductions are complete, the United States and Russia are each expected to have approximately 50 metric tons (MT) of excess weapons plutonium. At the end of 1990 there were about 260 MT of plutonium in military inventories worldwide and about 650 MT of plutonium that had been produced in commercial power reactors. Of this commercial reactor plutonium, about 530 MT were in irradiated spent fuel and 120 MT were in mixed-oxide (MOX) fuel or stored as plutonium oxide. New production of commercial reactor plutonium during the first half of the 1990s was about 70 MT per year.

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Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options even on emplacement in a repository at all: the key point is that once the plutonium is embedded in spent fuel or waste-bearing glass logs of suitable specifications, it will be approximately as resistant to theft or diversion as the larger quantities of plutonium in commercial spent fuel and will represent neither a unique security hazard nor a large addition to the radioactive waste management burdens that the spent fuel and immobilized defense wastes would pose in any case. All other options in the panel's purview were found to have significant disadvantages compared to the preceding two. Specifically: Some of the options fail to meet the spent fuel standard, in that the barriers they provide against the reuse of the plutonium for weapons are substantially lower than those of typical commercial spent fuel. This is so for "spiking" options that irradiate WPu-MOX quickly to levels much lower than those typical of commercial spent fuel, and for vitrification of the plutonium in a glass matrix that does not include large quantities of fission products. Some of the options meet the spent fuel standard but require more time and expense to do so than do the current-reactor/spent-fuel and vitrification-with-wastes options. This is so for building advanced LWRs or advanced liquid-metal reactors (ALMRs) for use in a once-through mode, and for building high-temperature gas-cooled reactors (HTGRs) for use in a once-through mode with moderate burnup. Some of the options could exceed the spent fuel standard by destroying a larger fraction of the plutonium or by reducing the proportion of the plutonium-239 isotope that is most attractive from a bomb-maker's viewpoint, but doing this would take longer and cost more than the preferred options, and it would only bring a significant security gain after the investment of the still larger amounts of time and money needed to apply the approach to civilian as well as military plutonium. This is the case with use of an HTGR in a high-burnup, once-through mode, with development of nonfertile fuels for LWRs or LMRs, and with use of either current or advanced reactor types (including accelerator-based convertors) in a multiple recycle mode to achieve high destruction of plutonium. Some of the advanced nuclear technologies considered and rejected by the panel for the WPu disposition mission in the decades immediately ahead might be appropriate for a later campaign to move beyond the spent fuel standard for military and civilian plutonium alike, if society decides to do that, and continuing study of such possibilities at the conceptual level is certainly warranted. The choices eventually made about this will be tightly intertwined with society's choices about how much of its energy will come from nuclear sources and with what technologies this nuclear energy will be provided; these are important

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Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options questions, but the panel was not asked to address them and did not need to do so in order to address the narrower and shorter-term question of how to reduce expeditiously the security risks from excess WPu. The Leading-Candidate Options: Specific Cases and Their Timing In terms of timing, which as argued above is a crucial element of security, the current-reactor/spent-fuel option and the vitrification-with-wastes option are roughly comparable to each other and superior to the other options in the Reactor Panel's purview. The limiting ingredients on when the current-reactor/spent-fuel approach in the United States could begin processing plutonium would be providing the needed MOX fuel fabrication capacity (no such capacity is currently operational in the United States) and obtaining the necessary approvals and licenses (use of MOX fuel in U.S. power reactors is not now licensed). The limiting ingredients on when the vitrification-with-wastes option could begin processing plutonium would be building or modifying the vitrification facilities to handle plutonium and determining a combination of melter configuration and log composition that provides adequate assurance against accidental criticality in the melter and the repository. Although the timing of all disposition options is subject to influences that are not entirely predictable, the panel judges that with a prompt decision to proceed in this direction—and given high national priority assigned to the task— fabrication of WPu-MOX fuel could begin in the United States as soon as the year 2001. This timing would entail bringing to operability the partly completed MOX fabrication facilities at the Fuel Materials and Examination Facility (FMEF) at the U.S. Department of Energy site in Hanford, Washington, with a capacity of 50 metric tons of heavy metal (uranium plus plutonium) in MOX fuel per year. For the range of 3.0- to 6.8-percent plutonium in heavy metal contemplated for use in LWRs, this would correspond to 1.5-3.4 metric tons of WPu per year, so that a nominal 50 metric tons of WPu could be fabricated into MOX in 15-33 years of operation. If it were decided instead to build a new MOX fabrication facility at a government site from scratch—perhaps with a capacity of 100 metric tons of heavy metal or 3.0-6.8 metric tons of WPu per year—fabrication of WPu-MOX fuel in the United States might, optimistically, begin as soon as 2003, and 50 metric tons of WPu could be fabricated thereafter in 7-17 years of operation. Most if not all of the 109 commercial LWRs operating in the United States in 1994 would be capable, without significant modification, of operating with at least one-third WPu-MOX fuel in their cores. (The remainder of the core would contain ordinary low-enriched uranium—LEU—fuel.) Only a small fraction of these reactors, representing about 7 percent of the 1994 U.S. LWR capacity, would be needed in order to load 50 metric tons of WPu, fabricated at the FMEF

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Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options into MOX with 4.0-percent plutonium in heavy metal, over a period of 25 years—say, starting in 2002 and finishing in 2026—assuming one-third MOX cores.2 If instead of FMEF, a new MOX fabrication plant with twice FMEF's capacity were used and went into operation in 2003, then loading its output into 14 percent of U.S. LWR capacity using one-third MOX cores would lead to completion of loading of the WPu-MOX by about 2016. There is, of course, a security trade-off associated with increasing the number of reactors using MOX in order to reduce the duration of the campaign. The number of reactors needed to load a given amount of WPu-MOX in a given period can be reduced if the fraction of MOX in the core can be increased. Three 1,221 -megawatt-electric (MWe) pressurized-water reactors (PWRs) operating at Palo Verde, Arizona, and one 1,240-MWe PWR that is 75-percent complete in Satsop, Washington, were designed to use 100-percent MOX cores, and U.S. reactor manufacturers have indicated that a significant number of the other operating U.S. reactors could use 100-percent MOX cores safely without major modification. Assuming this capability is confirmed by regulatory review, just two 1,200-MWe-class PWRs using 100-percent MOX cores with 4.0-percent plutonium in heavy metal could load 50 metric tons of WPu in 25 years; with WPu-MOX from FMEF, this job could be finished as soon as 2026. Given twice the WPu-MOX output from a new plant that started in 2003, four reactors with these specifications could finish this job by about 2016. Alternatively, if a WPu loading of 6.8-percent plutonium in heavy metal in a 100-percent MOX core passed safety review, two 1,200-MWe-class PWRs using the output of FMEF could load 50 metric tons of WPu in 15 years, finishing around 2016. If the use of 100-percent MOX cores in order to hold down the required number of reactors is desired but the existing U.S. reactors suitable for this turn out to be unavailable for the WPu disposition campaign, modifications to one or more of the other operational or under-construction U.S. LWRs would make it possible, at tolerable cost, to use these in the 100-percent MOX mode (again, assuming favorable safety review). The modifications would entail addition of more control absorbers and corresponding changes to the hardware at the top of the core, and if applied to reactors already operating would require a substantial shutdown period to complete. This could be done well within the period that will be required in any case to bring a U.S. MOX fabrication capability into operation; the extra cost of this approach is, rather, the loss of electricity supply and associated revenues if a working power reactor needs to be shut down for an extended period. 2   For example, six 1,250-megawatt-electric pressurized-water reactors using MOX containing 4.0-percent plutonium in heavy metal in 33 percent of their cores, operating at a capacity factor of 75 percent, and irradiating their fuel to 42 thermal megawatt-days per kilogram of heavy metal, would load among them 2.0 metric tons of WPu per year and thus would complete the loading of 50 metric tons of WPu in 25 years.

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Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options If, for some reason, no combination of currently operating and partly completed U.S. LWRs was deemed attractive for the WPu disposition mission, it would be possible at the cost of a few years' delay to construct a new dual-purpose (WPu disposition/electricity-generation) reactor or reactors on a government site. The logical choice of reactor type for this function, given adoption of the spent fuel standard and the desirability of minimizing the delay, would be an evolutionary LWR. Such reactors are technically mature, have achieved final design approval from the Nuclear Regulatory Commission, and are under construction overseas; they would offer the smallest increases in time and cost, compared to using currently operating reactors or finishing partly completed ones, of any new reactor type.3 Given a timely decision to proceed, fuel loading in a new evolutionary LWR could begin, optimistically, as soon as 2005. Another way to accomplish the current-reactor/spent-fuel option would be through the use of some of the heavy-water-moderated CANDU reactors in commercial operation in Canada. These reactors appear to be capable of using 100-percent MOX fuel without physical modification. Given favorable regulatory review and Canadian interest in participating in nuclear arms reductions in this way, it would be possible for two currently operating CANDU reactors of 769 MWe each to process 50 metric tons of WPu into spent fuel somewhat less radioactive than that from U.S. LWRs in about 24 years of operation. (Canada has 22 CANDU reactors totaling about 15,000 MWe.) Analysis by AECL Technologies 4 indicates that MOX CANDU fuel in the needed quantities for this scenario could be fabricated in the United States at the FMEF. Assuming FMEF operation starting in 2001, the last of the WPu-MOX could be loaded into the two CANDUs in 2025. The panel believes that the timing of the current-reactor/spent-fuel option in Russia could be similar to that in the United States or Canada, given a Russian decision to proceed in this direction. For safety reasons, if this option is selected the only currently operating Soviet-designed reactors that should be used are the 950-MWe VVER-1000 LWRs, which are similar to Western PWR designs. Russia has six such reactors in operation and Ukraine has nine. Depending on the results of a safety analysis of high plutonium loadings in this reactor type, and on the acceptability of high plutonium content in the spent fuel, it might be necessary to bring into operation some of the additional VVER reactors currently standing unfinished in Russia if the goal is to process 50 metric tons of WPu in 30 years of operation within that country alone.5 In the most straight- 3   Advanced light-water reactors (ALWRs) of the passive type are based on proven technology, but they have not yet reached the stage of licensing approval and thus would entail more time and cost to bring into operation than would the evolutionary LWRs. HTGRs, ALMRs, and other advanced reactor types would entail still greater development costs and delays. 4   AECL Technologies is the U.S. branch of Atomic Energy of Canada, Limited. 5   As a technical matter, the VVER-1000 reactors in Ukraine could be used along with those in Russia, but sending Russian WPu to Ukraine could raise difficult political issues. Based on one

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Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options forward scenario, the WPu-MOX fuel for the VVER-1000s would be fabricated at a partly completed facility at Chelyabinsk-65, which could be finished for this purpose. If WPu-MOX fuel were produced not in the United States or Russia but in the existing or planned MOX fabrication plants in Europe and Japan, and if agreements on institutional arrangements for doing this could be reached expeditiously, a current-reactor/spent-fuel disposition campaign might be able to start 2-3 years earlier (by avoiding licensing and plant-completion delays in the United States and Russia). The campaign might also be able to be completed more rapidly once started if enough European or Japanese MOX fabrication capacity were available and it were used to make WPu-MOX for more reactors than in the fabrication-limited cases described above. A shortened campaign would entail the security liability of using MOX in a larger number of reactors than otherwise, however. If MOX fabrication capacity beyond civilian needs is not available, this accelerated approach would also have the shortcoming of increasing the stock of civilian separated plutonium (because of its displacement in MOX fabrication by WPu), unless civilian plutonium separation were slowed down until WPu disposition was complete. The earliest possibility for implementing the vitrification-with-wastes option in the United States would seem to be at the U.S. Department of Energy's Savannah River plant, where vitrification operations to immobilize the defense high-level wastes (HLW) at that site are scheduled to begin at its Defense Waste Processing Facility (DWPF) in 1996. Although some technical issues require resolution before a decision to proceed can be confidently made, the panel believes that the necessary preparations for adding WPu to this process could be completed by 2005. It would then be possible to incorporate 50 metric tons of surplus U.S. WPu, at 1.3-percent WPu by weight, in the 2,200 logs of 1,700 kilograms each that are scheduled to be produced during the last eight years of the currently planned DWPF campaign, that is, from 2006 through 2013. Groundbreaking for a vitrification facility similar to Savannah River's DWPF is expected sometime this year at the U.S. Department of Energy's Hanford site. It is to be used to vitrify the military high-level waste now stored at that location, which is roughly comparable in quantity to that at Savannah River. By virtue of its later time schedule, the Hanford facility might be more readily and economically modifiable than the DWPF to accommodate WPu in the vitri-     third MOX fuel, 4.0-percent plutonium in heavy metal, average burnup of 40 megawatt-days per kilogram heavy metal, and 75-percent capacity factor, five VVER-1000 reactors would need just over 30 years to load 50 metric tons of surplus WPu. One official of the Russian Ministry of Atomic Energy has said that only four of that country's six operating VVER-1000 reactors are suitable for MOX fuel. If this problem were to be addressed by completing some of Russia's unfinished VVER-1000 reactors, modifications could be made during the completion of construction to permit use of 100-percent MOX cores in these reactors, which would reduce the number of reactors required for the WPu disposition campaign.

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Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options fication process, all the more so if criticality considerations prove to require extensive changes to the current DWPF design. The timing of a WPu vitrification campaign in Russia probably would be similar, if an early decision were made to proceed in that direction. A waste-vitrification facility with a nominal output of 1 metric ton of glass per day has been in operation at the Chelyabinsk-65 site in Russia since 1987. The phosphate glass composition employed at this facility appears to be less suitable for plutonium disposition than is the borosilicate glass planned for U.S. vitrification facilities. To our knowledge, the time and money that would be needed to modify the Russian facility to make borosilicate instead of phosphate glass and to integrate WPu with its process stream have not been estimated, but these requirements seem unlikely to differ greatly from those we have estimated for the modifications that would be needed to U.S. vitrification facilities. Russian authorities, however, have so far strongly resisted approaches to WPu disposition that would "throw away" the plutonium without generating any electricity from it, irrespective of arguments that electricity generation with WPu is costlier than with LEU. While the estimates of timing provided here for variants of the current-reactor/MOX option and the vitrification-with-wastes option differ in detail, the uncertainties in both cases—relating more to resolution of institutional issues in the reactor case and to resolution of technical issues in the vitrification case—are bigger than the differences in the reference-case point estimates. Thus it would not be meaningful to say more than that the two sets of options are comparable. Under the most optimistic assumptions that we consider defensible, any of the advanced-reactor options would be at least a full decade slower to get started than our leading-candidate options would be, given a timely decision to proceed. The delay could easily be longer even for the best developed of the advanced options (HTGRs, LMRs), and it would probably be two decades or more for the least well developed of them (molten salt reactors, accelerator-based convertors). We believe that the direct and indirect security risks of delays of this magnitude should be considered unacceptable, given that the current-reactor/spent-fuel option and the vitrification-with-wastes option provide the means to avoid these risks and given that the advanced-reactor options do not, according to our assessment, offer sufficient advantages in other aspects of security, economics, or environmental, safety, and health characteristics to offset their timing liability. OTHER ASPECTS OF SECURITY With respect to those aspects of security that depend on the details of handling, processing, and transporting various plutonium forms, vitrification entails

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Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options fewer and somewhat simpler steps than the current-reactor options, and hence would be somewhat easier to safeguard. With respect to security of the final plutonium forms, the current-reactor options obviously meet the spent fuel standard, and the panel judges that the vitrification option meets this standard also. The plutonium in the spent fuel assembly would be of lower isotopic quality for weapon purposes than the still weapons-grade plutonium in the glass log, but since nuclear weapons could be made even with the spent fuel plutonium this difference is not decisive. Under typical assumptions, the radiological barrier presented by glass logs would be about three times smaller than that presented by a fuel assembly (but still very high), and the mass of a glass log—containing, coincidentally, about the same amount of plutonium as a fuel assembly—would be about three times greater.6 The difficulty of separating the plutonium from the accompanying materials would be roughly comparable in the two cases. To summarize the situation with respect to security of the current-reactor/MOX and vitrification options: (1) the two options are comparable in timing; (2) vitrification has a modest advantage in safeguardability of the handling, processing, and transport steps; and (3) the current-reactor/spent-fuel option has a modest advantage in the barriers associated with the final plutonium form because of the difference in plutonium isotopics. The panel concludes that the two approaches are comparable in security overall, that either would be adequate, and that no other option known to us is superior. Use of advanced reactors could reduce the quantity of residual plutonium from the disposition process, even on a once-through basis in the case of the HTGR, and with the assistance of reprocessing and plutonium recycle in other cases. Reprocessing and recycle could also accomplish such reductions in conjunction with current or evolutionary LWRs. In some of these cases, most notably the HTGR, the residual plutonium's isotopic quality for weapon purposes could also be reduced to below that characteristic of typical spent LWR fuel. As noted earlier, however, these changes would not bring much reduction in overall security risk unless commercial spent fuel stocks were similarly transformed. Although society might eventually decide to do this and might choose advanced reactor types for the purpose, transforming today's very dangerous stocks of 6   For example, a large glass log of the type expected to be produced at Savannah River's DWPF would contain 1,700 kg of glass in a 450-kg steel jacket; at 1.3-percent WPu in glass, it would hold 22 kg of plutonium; and, at the expected defense high-level-wastes content of 20 percent by weight it would produce a gamma-ray dose rate of 2,600 rem (roentgen-equivalent-man) per hour at the surface of the container 30 years after the log was produced. By comparison, a MOX fuel assembly from a Westinghouse PWR would have a mass of about 660 kg, would contain about 18 kg of plutonium after irradiation to 40 megawatt-days per kilogram of heavy metal (assuming initial WPu content of 4.0 percent of heavy metal), and would produce a gamma-ray dose rate of 7,900 rem per hour at the surface of the assembly 30 years after discharge from the reactor.

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Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options excess WPu to meet the spent fuel standard does not require advanced reactors and should not wait for them. ECONOMIC COMPARISONS The monetary costs of alternative approaches to the disposition of WPu are of secondary importance compared to the security aspects. The panel has nonetheless devoted considerable effort to developing a reasonably comprehensive and internally consistent set of estimates of the costs of alternative approaches, including accounting for electricity revenues where appropriate, in order to try to sort out diverse claims in the literature about the costs or profitability of WPu disposition operations, to assist in ranking options that are not readily distinguishable on security grounds, and to facilitate planning for the needed investments. The panel's estimates indicate that the most likely costs for the borosilicate-glass/vitrification option and for the less costly among the current-reactor/spent-fuel options both fall in the range of $0.5-$2 billion (1992 dollars), expressed as the discounted present value, as of the start of plutonium disposition operations at the reactor or melter, of the stream of incremental costs associated with plutonium disposition, less electricity revenues where it is appropriate to count them. (The real discount rate assumed was 7 percent per year.) The range of central estimates for all of the current-reactor options extends from $0.5 billion to about $5 billion in these terms. The lowest central estimate, at about $0.5 billion, is for the option using currently operating U.S. LWRs that need no modification to use MOX safely, with the fuel fabricated at the FMEF at the Hanford site. Four of the options studied have central-estimate costs around $1 billion: use of MOX fuel from FMEF in currently operating CANDU reactors in Canada; use of MOX from FMEF in a single, currently mothballed, partly completed PWR that would be completed for this purpose; use of MOX from an entirely new fuel fabrication plant in currently operating U.S. LWRs that need no modification to use MOX safely; and vitrification with defense high-level wastes at the Savannah River site. The estimates in the range of $5 billion are for options involving the construction of both new reactors and new MOX fabrication facilities. Although the central estimates in all cases considered correspond to net costs, the panel's judgmental 70-percent confidence intervals include a possibility of profits from WPu disposition in some of the cases in which reactors that would not otherwise operate are completed or built from scratch for the purpose of WPu disposition and use MOX fuel from FMEF. A profit from plutonium disposition would only occur, however, if the fabrication of MOX fuel were significantly cheaper than now appears likely (compared to fabrication of equivalent LEU fuel), and if, at the same time, the electricity produced in the reactor could be sold at prices somewhat higher than now seem likely. (For

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Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options every case in which light-water reactors for plutonium disposition could charge high enough electricity prices to make a profit, an even larger profit would arise if the same reactors used LEU fuel rather than MOX, without addressing the problem of WPu disposition.) The range of $0.5-$5 billion—covering the best estimates of net present value, at reactor or melter startup, of most of the options considered—corresponds to $10,000 to $100,000 per kilogram of WPu, or $40,000 to $600,000 for a nominal “bomb's worth" of 4-6 kilograms. Even the higher figure is probably less than what this weapon material once cost to produce, as well as much less than would be spent in the attempt to recover such material if it went astray. It is incomparably less than would be spent to try to deter or otherwise prevent its use in the form of a bomb in the hands of a potential adversary. Thus, funding should not be allowed to become a barrier to carrying out plutonium disposition. ENVIRONMENT, SAFETY, AND HEALTH (ES&H) The greatest dangers to public welfare associated with the existence and disposition of WPu are unquestionably those connected with national and international security—that is, the dangers associated with the potential uses of this material in nuclear weapons, as well as the dangers that could be posed for global arms reduction and nonproliferation prospects by failure to manage the WPu in a manner widely understood to preclude its reuse in weapons. The preeminence of these security dangers, however, should not obscure the need for careful attention to the ES&H risks posed by the WPu under the different possible options for its disposition. The panel regards it as very important that the governments involved express in the strongest terms their commitment to respect reasonable ES&H constraints in their WPu disposition programs, and that they demonstrate this commitment by promulgating promptly an appropriate set of ES&H criteria for the WPu disposition process and by putting in place whatever mechanisms and resources are required to give confidence that those criteria will be met. The panel believes that options for plutonium disposition should: comply with existing regulations, of the country in which disposition takes place, governing radioactivity and radiation from civilian nuclear-energy activities; comply with existing international agreements and standards on the disposition of radioactive materials in the environment; and not add significantly to the ES&H burdens that would result, in the absence of programs for disposition of WPu, from appropriate management of civilian nuclear-energy generation and of the environmental legacy of past nuclear weapons production.

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Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options The panel believes that both the current-reactor/spent-fuel and vitrification-with-wastes approaches, suitably designed, can meet these criteria. Most of the ES&H impacts of WPu disposition using either of these options can be expected to represent modest additions, at most, to the routine exposures to radiation and risks of accident associated with other civilian and military nuclear-energy activities underway in the United States. There is no apparent reason that the activities involved in WPu disposition using either of these approaches should not be able to comply with all applicable U.S. ES&H regulations and standards. While there are differences in detail in the ES&H challenges and risks posed by the two options—e.g., a somewhat more complicated set of plutonium-handling operations for the reactor options than for the vitrification option, and a greater relative increase in plutonium content of the final waste form for the vitrification option than for the reactor options—these differences do not consistently favor one class of options or the other, and none is large enough in relative or absolute terms to justify choosing one class of options over the other. ES&H issues that will need further attention in the next phase of study of these options include: developing and testing the systems to ensure adequate safety against criticality accidents in the melter for the vitrification option; confirming the conditions under which full-MOX cores can be used without adverse impacts on safety in reactors of currently operating commercial types; and determining the conditions that will provide for adequate assurance against long-term criticality in geologic repositories containing either spent fuel or glass logs from plutonium disposition operations. These issues differ considerably in the nature and complexity of the work that will be needed to settle them to the satisfaction of the technical and regulatory communities, but it is the panel's judgment that suitable approaches exist for all of them. Both the current-reactor/spent-fuel option and the vitrification-with-wastes option would add WPu to a set of nuclear activities that would be going on in any case, and both would leave the residual WPu in a waste form—spent fuel in one case and HLW-bearing borosilicate glass logs in the other—that will exist in large quantities and will need to be safely managed whether used for WPu disposition or not. The panel emphasizes, in this connection, that a U.S. geologic repository is not likely to be ready to receive wastes of any kind before 2015. Vitrified waste logs, with or without plutonium, and plutonium-containing spent fuel from nuclear reactors, whether WPu has been incorporated in some of it or not, will need to be stored in engineered facilities until a geologic repository is ready to receive them.

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Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options RECOMMENDATIONS Parallel Project-Oriented Programs The current-reactor/spent-fuel and vitrification-with-wastes options are the two leading contenders for plutonium disposition to the spent fuel standard. Because it is crucial that at least one of these options succeed, because time is of the essence, and because the costs of pursuing both in parallel are modest in relation to the security stakes, the panel recommends that project-oriented activities be initiated on both options, in parallel, at once. Although both of these options are technically feasible and have been recommended by the panel in part because they can be deployed comparatively rapidly, some significant uncertainties accompany both of them. The areas of uncertainty in the current-reactor/spent-fuel option are primarily in licensing and public acceptance. Those in the vitrification-with-wastes option relate mainly to criticality and to the technical issues of mixing plutonium and high-level wastes. Further paper studies will not significantly reduce these uncertainties; the best way to reduce them is through the experience gained in moving toward implementation. In connection with the current-reactor/spent-fuel option, work should be started to seek out specific reactors and MOX fabrication options that would minimize multiple plutonium transportation steps so as to reduce this aspect of security risk, to identify locations that are most amenable to public acceptance, and to ascertain the willingness of the plant owners to participate and the conditions they would impose. Detailed engineering studies should be completed and licensing applications submitted to the Nuclear Regulatory Commission. From that base, the sound cost estimates, schedules, and financial plans that are essential to considering full project authorization could be prepared. In connection with the vitrification-with-wastes option, laboratory work and realistic testing should be started to address the technical uncertainties. Research and development plans, program schedules, and key milestones should be defined. As the results of the research and development are obtained, detailed cost estimates and ES&H analyses can be developed and submitted to the U.S. Department of Energy and the Defense Nuclear Facilities Safety Board in pursuit of project authorization. The pursuit of the two options in parallel, as project-oriented tasks with near-term milestones and aggressive schedules, should be aimed at bringing both processes online by the end of the century or as shortly thereafter as possible. It would be a mistake to spend tens of millions of dollars and additional years of paper studies to try to demonstrate, in the absence of actual work toward deployment, which of the two options should be selected over the other. It will likely be less expensive in the long run, and clearly superior from the security and ES&H perspectives, to proceed with both now. If either option falters

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Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options due to technical, licensing, or other difficulties, the pursuit of the other option can continue without the loss of time that would have been associated with choosing early and choosing wrong. Indeed, it may prove to be desirable to implement both options for different parts of the stockpile: as one example, it may turn out that reactor approaches are preferable for the relatively pure plutonium in the components of dismantled weapons, while vitrification may prove to be the better alternative for the tons of plutonium that exist in scrap, solutions, and other forms. We recommend, therefore, that the U.S. Department of Energy's Programmatic Environmental Impact Statement process (scheduled to be completed in 1996) should be oriented toward a decision to pursue both the current-reactor/spent-fuel option and the vitrification-with-wastes option, not toward a decision to eliminate one or the other. Subsequent preparation of Environmental Impact Statements (EISs) for both options, and the participation of the public in these processes, should proceed in parallel too. The inclusion, in the EIS and public participation processes, of the results of the specific project-oriented activities mentioned above will be essential to the success of those processes. Full project authorization for one of the options would not be granted until the EIS is completed and approved. Working with Russia The fundamental objective of the WPu disposition program will not be achieved unless the Russians carry out a disposition program in parallel, on a similar time scale, and adhering to disposition standards equivalent to those of the United States. The project-oriented activities recommended above would lend themselves to forming joint projects with the Russians to assure such a parallel approach. Joint projects will also serve to develop a technical consensus on the disposition process and standards, which, as pointed out elsewhere in this report, does not exist today. The panel recommends that the United States immediately initiate joint project-oriented activities with Russia covering both the MOX and the vitrification options. The panel also strongly concurs with the parent committee's recommendation that the United States and Russia should continue discussions with the aim of agreeing that whatever disposition options are chosen, an agreed, stringent standard of accounting, monitoring, and security will be maintained throughout the process—coming as close as practicable to meeting the standard of security and accounting applied to intact nuclear weapons. The Longer Term Follow-on studies should continue on the longer-range questions of whether and how the residual security risks of WPu and other plutonium should eventually be reduced beyond the spent fuel standard. It is essential, however, that

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Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options such longer-range studies not be allowed to draw resources or attention from the pursuit of the two options closest to hand for moving rapidly toward achieving the spent fuel standard for the weapons plutonium that poses a "clear and present danger" today. REFERENCES NAS 1994: National Academy of Sciences, Committee on International Security and Arms Control. Management and Disposition of Excess Weapons Plutonium. Washington, D.C.: National Academy Press, 1994.