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Diversion-resistance criteria for future nuclear power
Diversion-resistance criteria for future nuclear power R.H. Williams and H.A. Feiveson
In order for nuclear power to make a major contribution to global energy, it would have to be made not only safe and cost-effective but also highly diversion-resistant. For nuclear power developed on a large scale, the current system o f international safeguards is inadequate to this challenge. What would be required are a redesign o f nuclear technologies, to make them far less attractive sources o f nuclear weapons-usable materials than existing and planned technologies, and an internationalization of sensitive nuclear facilities, as proposed in the 1946 Acheson-Lilienthal Plan. The nuclear industry must come to recognize that its long-term viability depends on its being able to offer a peaceful atom that is unambigously distinct from the military atom. Keywords: Nuclear power; Plutonium; Proliferation
Concern about the global greenhouse warming is leading to reconsideration of the nuclear power option. Two problems that must be dealt with effectively in order to have a resurgent nuclear industry the risk of reactor accidents and high cost - are being given focussed attention. But another important issue - the nuclear weapons connection to nuclear power - has been given scant consideration to date in the policy discussions revisiting the nuclear option. Inherent in nuclear technology is the fact that the chain-reacting materials that produce energy inside a reactor can also be used for making nuclear explosives. One of these materials, plutonium, a byproduct of the production of nuclear energy, is particularly worrisome. A one gigawatt (GW) light-water reactor (LWR), the dominant type in most of the world, discharges approximately 200 kg of plutoThe authors are at the Center for Energy and Environmental Studies, Princeton University, Princeton, NJ 08544, USA.
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nium annually in its spent fuel - enough for more than 20 nuclear weapons. For a resurgent nuclear industry large enough to contribute substantially to reducing the greenhouse problem, the potential for diversion would be daunting. Suppose that concern about the greenhouse problem were to lead to a level of nuclear power for electricity and fuel applications adequate to replace one quarter of the present global level of fossil-fuel use. Such an emphasis on nuclear power could require a ten-fold increase in global installed nuclear capacity to 3 000 GW. In current reactors, a nuclear capacity of this magnitude would produce over 500 000 kg of plutonium per year. This is bad enough. But concerns about uranium supply at such a high level of nuclear power development would lead to pressures for the development of nuclear power systems based on 'plutonium-breeder' reactors in which plutonium bred in the reactor is routinely separated from spent fuel in nuclear fuel reprocessing plants and recycled in fresh reactor fuel. A 3 000 GW nuclear system based on plutonium-breeder reactors would place into global nuclear commerce approximately 5 000 000 kg of separated plutonium per year. It is difficult to imagine human institutions capable of safeguarding these plutonium flows against occasional diversions of significant quantities to nuclear weapons. Because of the high diversion risk inherent in a 'plutonium economy', an alternative nuclear system that is diversion-resistant as well as safe and costeffective would have to be developed before nuclear power could play a major role in the energy future of the world.
Criteria for diversion resistance The current system of applying international safeguards (inspections) on otherwise nationally-owned and operated nuclear power facilities would not be adequate to the task of uncoupling nuclear power and nuclear weapons technologies with nuclear power developed on a large scale.This truth was recog543
Diversion-resistance criteria for future nuclear power
nized at the beginning of the nuclear era. According to the March 1946 Acheson-Lilienthal Report: 1 We have concluded unanimously that there is no prospect of security against atomic warfare in a system of international agreements to outlaw such weapons controlled only by a system which relies on inspection and similar policelike methods. The reasons supporting this conclusion are not merely technical but primarily the inseparable political, social, and organizational problems involved in enforcing agreements between nations, each free to develop atomic energy but only pledged not to use bombs. To make nuclear power acceptably diversionresistant it is necessary to virtually eliminate access to weapons-usable materials - plutonium and uranium enriched in uranium-235 or uranium-233 to levels above some 10-20% 2 (ie containing less than 80-90% uranium-238, the presence of which renders low-enriched uranium unusable for weapons purposes). This implies a significant level of international control over nuclear power technology 3 - the central recommendation set forth in the A c h e s o n Lilienthal Report. We take this recommendation as a point of departure in exploring the prospects for making nuclear power sufficiently diversion-resistant that it could play a major role in the global energy future. We consider a nuclear power system consisting of two segments: international centres containing all sensitive nuclear technologies and activities that are maintained under tight physical security by the International Atomic Energy Agency, and national facilities that are maintained under the existing system of safeguards. Depending on the characteristics of the nuclear technology, the mix of centres and national facilities could range from almost all significant activity under international control to a relatively small number of international centres serving a large number of national facilities. Within such a framework, the nuclear power system should be designed to satisfy the following criteria: •
•
•
•
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Restrictions on sensitive nuclear technologies and materials shall be non-discriminatory among nations. Fissionable weapons-usable material that is not contained in spent fuel and facilities to enrich uranium or to separate plutonium shall not exist outside international centres. As far as possible, fissionable weapons-usable material that is not contained in spent fuel shall not be produced even at the international centres. Spent fuel shall be stored and disposed of in international centres.
Reactors under national authority shall be designed to reduce to very low levels the production of weapons-usable materials in spent fuel (of the order of a critical mass or less per year per gigawatt of capacity). The first criterion arises from the consideration that an international regime in which sensitive nuclear technologies and materials are available to some countries deemed 'safe' or 'non-proliferating' but denied to other countries regarded as 'proliferationp r o n e ' is i n h e r e n t l y unstable. A stable nonproliferation regime can be achieved only if the rules regarding the availability of nuclear technologies are the same for all countries. The requirement of the second criterion - that weapons-usable material does not exist outside international centres - would be a major deterrent to criminal or terrorist diversions of weapons-usable material. The third criterion, to minimize the production of separated weapons-usable material even at international centres, would be a valuable additional safeguard against such diversions. Experience has shown that nominally tight security systems safeguarding a wide range of valuable materials can occasionally be breached by sufficiently determined and clever groups. Satisfying the second and third criteria would also deny nations quick access to nuclear weapons-usable materials and thus largely eliminate the risk of 'latent proliferation', whereby nations move inexorably toward a nuclear weapons capability whether or not they have deliberately chosen to acquire nuclear weapons. 4 If civilian nuclear power programmes provided easy access to weapons-usable material, governments could proceed, at little cost, to a point but one step away from the acquisition of nuclear weapons, without actually making the final decision to go nuclear and without making their intentions clear in advance. But if nuclear weapons-usable material is not readily available, it would be easier for those opposed to acquiring nuclear weapons to prevail in government decisions relating to nuclear weaponry. It would be difficult to secure a consensus within the government bureaucracies of most nonnuclear weapons states on the desirability of acquiring nuclear weapons, because it is possible only in exceptional cases to make a persuasive case that security would be enhanced by having nuclear weaponry. Moreover, the longer the time required to acquire nuclear weapons, the greater the risk of 'getting caught'. Even if the second and third criteria were satisfied, substantial quantities of plutonium, albeit un-
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separated might still be contained in the spent fuel. While the plutonium in spent fuel is 'protected' against diversion by the intense radioactivity of the nuclear fission products and is therefore much less accessible than separated plutonium, it is feasible for a country intent on acquiring nuclear weapons to build, in a period of several months, a crude ('quickand-dirty') reprocessing facility adequate to extract enough plutonium from spent fuel inventories to make a few nuclear weapons. 5 The temptation to do this could become great in certain crisis situations. Therefore, the fourth criterion calls for delivering spent fuel discharged from national reactors as quickly as practicable to international spent fuel repositories. An advance commitment to deliver spent fuel to these repositories should be made a condition for any country's acquisition of nuclear technology. Even with the requirement to send spent fuel to international repositories, there would be opportunities to divert some spent fuel during the 'coolingoff' storage period at the reactor site or during transport. The last criterion, therefore, requires nuclear engineers to design nuclear reactors for use outside international centres in such a way as to minimize the quantities of weapons-usable materials in their fuel inventories and in the spent fuel discharged from them. If this criterion were met, the time required to obtain weapons-usable materials from spent fuel in crude reprocessing facilities would be so lengthened and the risk of getting caught would be so significantly increased that the incentive to mine the spent fuel or reactor inventories for weapons-usable materials would be greatly diminished. Meeting this criterion would also greatly decrease the incentive to eventually mine the spent fuel for commercial purposes, with all the attendant risks of using separated weapons-usable materials for nuclear fuel. Satisfying the criteria set forth here would not make nuclear power diversion-proof- no technical or institutional fix can do that. Nor would it prevent nations determined to acquire nuclear weapons from doing so. But satisfying these criteria would make the nuclear power route an unattractive one for acquiring nuclear weapons. To reduce proliferation risks to truly low levels, effective measures would also have to be taken to reduce the incentives of non-nuclear countries to acquire nuclear weapons. This would require nuclear-weapons states to reduce their dependence on nuclear weapons and to sharply separate their weapons programmes from their civilian nuclear power programmes. Specifically, the nuclear
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weapons states would have to move to curtail or halt altogether the production of fissile material for weapons and reduce their stockpiles of weapons. Such moves are more plausible now than they have ever been, in part because of recent political developments in the Soviet Union and Eastern Europe and the dramatic improvement in East/West relations. Moreover, the USA and the USSR are working toward substantial reductions in strategic and tactical nuclear weapons; for this reason, and also because of safety and environmental problems at weapons production complexes, discussions of a cutoff in fissile material production for weapons have begun in both countries. The restructuring of civilian nuclear power that we call for here would be an effective complement to such actions by the nuclear weapons states. Both courses of action are necessary to the establishment of an effective nonproliferation regime.
Discouraging reprocessing and plutonium recycling For the present generation of nuclear power plants operating on a 'once-through' fuel cycle, the risks of proliferation and criminal or terrorist diversion of nuclear weapons-usable materials are limited by the fact that weapons-usable material is never isolated. The fresh uranium fuel is dilute in the fissile isotope, uranium-235 (about 3%), and the plutonium produced in the reactor is not separated from the spent fuel. As long as the plutonium remains locked in the spent fuel, it is partially protected against diversion to nuclear weapons use by the intensely radioactive products of nuclear fission. But when nuclear fuel is reprocessed to recover the plutonium for use in fresh fuel, either in breeder reactors or in reactors of the current type, diversion risks increase sharply. 6 Consideration of ongoing recycling activities, though modest in scale compared to such activities in a full-blown 'plutonium economy' based on breeder reactors, gives an indication of the nature of these risks. France, Great Britain and Japan already have operating or under construction commercial-size reprocessing plants to separate plutonium from spent fuel. Under current reprocessing schedules, based on already negotiated nuclear fuel-reprocessing contracts, over 20 000 kg of plutonium will be separated annually by the year 2000 in Europe and Japan. Japan and several European countries have initiated programmes to recycle the separated plutonium in current LWRs. Under these programmes, it is
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planned to fabricate the separated plutonium into plutonium-uranium (mixed-oxide) fuel rods and recycle these in scores of reactors. As the programmes come to fruition, much of the plutonium being separated will be placed into commerce within Europe and between Europe and Japan. This commerce will involve hundreds of shipments annually by trucks, trains, ships and planes. Spent fuel will be sent from more than 100 reactors to reprocessing plants; the separated plutonium will be sent to fuel-fabrication plants; and the mixed-oxide fuel fabricated at these facilities will then be sent to the reactors using the mixed-oxide fuels. About half of the separated plutonium will be transported across international boundaries, including from Europe to Japan. The security challenges of protecting such shipments are suggested by the arrangement surrounding the first large shipment of plutonium from France to Japan: 7 In 1984, 250 kilograms of plutonium oxide, separated in France from spent fuel from Japanese reactors, was returned to Japan by cargo ship. The ship carried only the plutonium; it made no intermediate stops; it was escorted partly by French and US warships; and it was continuously tracked by satellites by officials in Japan. Thus large-scale commerce in separated plutonium will present a safeguards challenge of colossal proportions and is completely inconsistent with our criteria for diversion-resistance. Indeed, the diversion risks are so glaring that it is an implicit premise of the countries undertaking plutonium recycling that neither the separated plutonium nor the recycling technologies will be made available to the developing countries. While the countries undertaking the recycling are not themselves likely proliferators, they are deceiving themselves if they think that they will be able routinely to recycle tens of thousands of kilograms of separated plutonium annually while the rest of the world accepts the dictum that separated plutonium is not for them. Moreover, it is in the developing countries where much of the nuclear capacity would have to be located in a resurgent nuclear future. A global energy scenario emphasizing a variety of energy sources that would help cope with the greenhouse problem was developed in a recent study by the US Environmental Protection Agency. In this scenario, the developing countries' share of worldwide nuclear power increases from 2% in 1985, to 5% in 2000, to 38% in 2025, to almost 60% in 2050. 8 In this context it would not be realistic to expect that recycling technology could be utilized in Europe and Japan but denied to the developing
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world in the long run. Reconstructing nuclear power therefore requires that commercial reprocessing and plutonium recycling be halted and deferred indefinitely, and that emphasis instead be given to nuclear technologies which do not involve these activities. How realistic is it to expect that this can happen? The USA, Sweden and Canada have already abandoned these activities, and the Soviet Union is not believed to be pursuing reprocessing on a commercial level. Although it will not be easy to persuade countries still engaged in reprocessing and plutonium recycling to abandon these activities, there should be no resistance based on economic incentives. Several studies have shown that, at today's uranium prices, reprocessing and recycling in LWRs or in breeders is simply not economic. 9 Even where reprocessing can be considered a sunk cost, it may not be economic to recycle plutonium. Although the recycling would save some expenditures on uranium and enrichment, these savings would be offset by the extra costs for security at reactor sites to guard the separated plutonium, for fabricating the mixedoxide fuels, and for storing and processing the separated plutonium before it is fabricated and recycled. Although France currently finds reprocessing profitable and Britain also expects to, this is because other countries - primarily Japan - have helped to finance their reprocessing operations through longterm reprocessing contracts. Were these contracts not to be renewed, reprocessing might look economically unattractive even to France. Non-renewal of the contracts is not out of the question. Japan, West Germany, Sweden and some other countries originally sent their spent fuel to France and to Britain for reprocessing largely because of laws that required their nuclear industries to demonstrate how they would deal with spent fuel before nuclear power was allowed to expand further. The problem is 'solved' by sending the fuel out of the country but only temporarily, because the high-level waste and plutonium are to be returned. Furthermore, spent mixed-oxide fuel will probably have to be disposed of without reprocessing because it is difficult to reprocess, and the contained plutonium cannot be used again in LWRs. Nor is reprocessing required for waste disposal. Spent fuel and high-level waste pose broadly similar problems in terms of repository design for final disposal. The fission product contents are essentially identical, and the heat outputs per tonne of original uranium are similar for the first hundred years. 10
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Diversion-resistance criteria for future nuclear power
Establishing international centres While the once-through system satisfies most of our first three criteria and provides a powerful safeguard against criminal and terrorist diversion and latent proliferation, the protection offered by oncethrough fuel cycles is not complete. Nations could still build quick-and-dirty reprocessing plants to separate plutonium from spent fuel. And, as long as some countries have the enrichment capacity needed to produce low-enriched uranium fuel, it will be difficult to deny indefinitely enrichment technology to other countries that want it. Accordingly, initiatives to establish various international nuclear centres should be launched concurrently with initiatives to stop reprocessing and plutonium recycling. One set of such centres is needed for repositories to receive and store spent fuel under international authority. Finding sites for such repositories that are acceptable to the public will be a major challenge. For example, it is already proving to be extraordinarily difficult to identify and establish acceptable sites for spent fuel storage in the United States; it is not easy to imagine a US citizenry willing to accept spent fuel produced in foreign nuclear power plants as well. But if some such sites can be identified, the internationalization of spent fuel repositories could facilitate other diversion-resistance initiatives. For countries with strong anti-nuclear movements, their establishment would 'sweeten' no-reprocessing agreements by providing these countries with a way to dispose of their radioactive wastes. International centres would also have to be established at existing as well as planned uranium enrichment facilities. This would be a major concession by the countries that already have enrichment capability, but so doing would be a major step toward establishing a non-discriminatory non-proliferation regime.
Redirecting nuclear research and development N u c l e a r p o w e r c a n n o t be m a d e a c c e p t a b l y diversion-resistant without a fundamental redirection of nuclear research and development away from plutonium-breeder reactors and plutonium recycling and toward nuclear technologies that hold forth the promise of being simultaneously cost-competitive, safe and diversion-resistant. Although reprocessing and recycling, as now c o n c e i v e d , c a n n o t be diversion-resistant, there may be uranium-efficient fuel cycles and technologies which can be made so. Alvin Weinberg has suggested that the use of
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accelerator breeders or fission-fusion hybrid breeders as neutron sources for producing uranium-233 in thorium might help make practical the concept of having a few international centres serving a much larger number of national facilities. The thorium would be reprocessed at the centres, and, after denaturing with natural uranium (which is 99.3% uranium-238), the recovered uranium-233 would be exported to national reactors. But such technology is far less developed than the plutonium-breeder reactor. According to Weinberg: 11 Though enthusiasm for these schemes runs high among the involved technical community, one must regard them as being largely unproven, economically if not technically. The engineering of such devices is formidable. Until we acquire actual engineering experience with accelerator breeders or fission-fusion hybrids, it would seem to me that their possible use need not concern us further. On the other hand, I am prepared to admit that over the very long run - say, 50 or more years, both . . . may become technically and economically feasible. In view of their potential contribution to a proliferation-resistant regime, continued serious study . . . seems justified. Even if the international-centre concept could be made to work, it still would not satisfy our last criterion that the reactors under national control s h o u l d not p r o d u c e substantial q u a n t i t i e s of weapons-usable material, unless the reactors were of a type different from any of those currently deployed. It is unclear at this time how far practical designs can be pushed in this direction while simultaneously satisfying concerns about cost and safety. However, c a n d i d a t e technologies having some potential diversion-resistant qualities have been advanced. One such technology, the high-temperature gascooled reactor (HTGR), has attracted interest as a system that offers significant safety advantages at small unit sizes over the current LWR. A modular (135 MW) version of the H T G R has been designed to operate on 20% enriched uranium. An H T G R operating on a denatured uranium-thorium oncethrough fuel cycle would discharge in spent fuel just 30 kg/y of plutonium per G W of capacity, 12 compared to 200 kg for a conventional L W R - not meeting our criterion but suggestive of what might be possible. Another technology which has recently received attention is the integral fast reactor (IFR), under d e v e l o p m e n t principally at A r g o n n e National Laboratory and based on a liquid metal-cooled reactor developed concurrently by General Electric and Argonne. The IFR would offer an element of diversion-resistance by co-locating the reactor, fab-
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Diversion-resistance criteria for future nuclear power
rication plant and reprocessing centre, so that plutonium-bearing materials would not have to be transported outside the security boundaries of the site. But the fresh fuel of the reactor would be 25% plutonium, and this would imply a fresh fuel inventory of at least a few hundred kg of plutonium per GW of generating capacity. With the IFR a nation could acquire very large quantities of weapon-usable material, if it wished to do so. Therefore, the IFR would not satisfy our criteria for reactors under national control. The HTGR and IFR concepts have been advanced primarily because of safety concerns. A thorium-based LWR with a core designed explicitly to meet diversion-resistance critera has been proposed by Alvin Radkowsky, a nuclear engineer working in Israel. 13 The 'seed', which occupies about 15% of each core assembly, would be enriched to 20% or less U-235 and would consist of plates or rods of uranium oxide mixed with inert nonabsorbing oxides. The remainder of each core assembly, the fertile 'blanket', would consist of thorium-oxide rods, containing about 5% uranium oxide. The seed would be replaced about once a year, but the blanket would remain in for about 10 years. At discharge, the blanket would contain about 1% uranium-233 diluted with about four times as much uranium-238. The calculated plutonium production rate is less than 14 kg/y of plutonium per GW of capacity. Radkowsky estimates that his reactor concept would provide a gain of about 400% in uranium utilization efficiency over the current LWR.
Prospects for a diversion-resistant nuclear power regime Making future nuclear power systems diversionresistant would require unprecedented institutional changes. It would be much tougher to bring about the adoption of diversion-resistant criteria than it has been to get the nuclear industry interested in improving reactor safety, largely because of the global nature of the needed reforms and the fact that the price of diversion-resistance is some loss of national sovereignty and energy autarky. Fortunately, however, the growing energy supply competition to nuclear power as an energy strategy for coping with the greenhouse problem should lead many decision-leaders to recognize that nuclear power expansion does not have to be accepted at any cost. One important competitor to nuclear power is a new generation of high-efficiency, low unit capitalcost gas turbines. Fired with natural gas these tur-
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bines emit just two-fifths as much C O 2 a s coal-fired steam-electric plants per kWh of electricity generated. TM While natural gas supply constraints and the contribution of natural gas combustion to the atmospheric buildup of CO2 imply that natural gas-fired gas turbines should be viewed only as an interim energy strategy for the decades immediately ahead, gas turbines can also play a major long-term role if fired with biomass as fuel. 15 Advanced aeroderivative gas turbines offer relatively low unit capital costs and high thermodynamic efficiencies at the modest sizes (less than 100 MW) needed for biomass applications. The prospects are good for bringing to market in the early 1990s biomass-fired versions of such turbines that will be able to compete with both coal and nuclear power technologies in many circumstances, i6 It is very likely that solar photovoltaic (PV) technology will also begin to be used in power-generating applications, beginning in the 1990s, as rapid progress is being made in both high-efficiency, concentrating crystalline solar-cell and low-cost, thin-film technologies. The cost and performance outlook for thin-film solar-cell technology is so promising 17 that, as oil and gas supplies get tight, it will also make economic sense to consider using this technology to produce DC electricity and converting the electricity to hydrogen via electrolysis. If the cost and performance goals of thin-film solar cells set for the next decade by the PV industry are met, the produced hydrogen would probably be less costly than hydrogen produced from nuclear electricity, even if the nuclear industry's target capital costs for a resurgent nuclear power industry are realized, and would be roughly competitive with synthetic liquid fuels from coal. TM We are therefore likely to have alternatives to nuclear power in the post-fossil fuel era and can decide on our level of commitment to it on grounds of security, as well as cost, safety and environmental impact - ie nuclear power can now be judged by a higher standard than was thought possible a decade ago. Also, the nuclear industry must come to recognize that its long-term viability depends on being able to convince the public that it can offer a peaceful atom that is unambiguously distinct from the military atom. Unless this is accomplished, nuclear power is doomed as a major long-term energy option. While nuclear power might get a second chance, in light of greenhouse concerns, it would not be likely to get a third chance if there were a major diversion incident somewhere in the world that could be plausibly linked to nuclear power. The fundamental re-orientation of nuclear policy we are proposing cannot be accomplished overnight.
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Diversion-resistance criteria for future nuclear power
It is critical, however, that it be well underway before the 1995 Review Conference of the NonProliferation Treaty, when the international regime for nuclear power will be renegotiated. An earlier version of this article was published in the Bulletin of the Atomic Scientists, April 1990. The authors are grateful to Robert Socolow and Frank von Hippel for extensive comments on early drafts of this paper.
1A Report on the International Control of Atomic Energy, US Government Printing Office, Washington DC, USA, 16 March 1946. 2J.C. Mark, T. Taylor, E. Eyster, W. Maraman and J. Wechsler, 'Can terrorists build nuclear weapons?', paper prepared for the International Task Force on Prevention of Nuclear Terrorism, 24 May 1986. 3L. Scheinman, 'Multi-national alternatives and nuclear nonproliferation', in G. Quester, ed., Nuclear Proliferation: Breaking the Chain, University of Wisconsin Press, Madison WI, USA, 1981, pp 77-102. 4H.A. Feiveson, 'Proliferation-resistant nuclear fuel cycles', Annual Review of Energy, Vol 3, 1978, pp 357-394. 5Comptroller-General of the United States, Quick and Secret Construction of Plutonium Reprocessing Plants: A Way to Nuclear Weapons Proliferation? US General Accounting Office, Washington DC, USA, 1978. 6D. Albright and H. Feiveson, 'Why plutonium recycle?' Science, Vol 235, 27 March 1987, pp 1555-1556; D. Albright and H. Feiveson, 'Plutonium recycling and the problem of nuclear weapons proliferation', Annual Review of Energy, Vol 13, 1988, ~L p 239--265. .S. Spector, The New Nuclear Nations, Vintage, New York, USA, 1984. 8Office of Policy, Planning and Evaluation, United States Environmental Protection Agency, Policy Options for Stabilizing Global Climate, draft report to Congress, February 1989.
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9OECD, The Economics of the Nuclear Fuel Cycle, Paris, France, 1985; Plutonium Fuel: An Assessment, Paris, France, 1989. t°OECD, Nuclear Spent Fuel Management: Experience and Options, Paris, France, 1986. HA.M. Weinberg, 'Nuclear energy and proliferation: a longer perspective', in A. Weinberg, M. Alonso and J.N. Barkenbus, eds, The Nuclear Connection: A Reassessment of Nuclear Power and Nuclear Proliferation, Paragon House Publishers, New York, USA, 1985, pp 221-239. 12H.A. Feiveson, F. yon Hippel, and R.H. Williams, 'Fission power: an evolutionary strategy', Science, Vol 203, 26 January 1979, pp 330-337. 13A. Radkowsky, 'The nonproliferative light water thorium burner concept', Tel-Aviv University, undated manuscript received baYRthe authors in 1988. .H. Williams and E.D. Larson, 'Expanding roles for gas turbines in power generation', in T.B. Johansson, B. Bodlund and R.H. Williams, eds, Electricity: Efficient End-Use and New Generation Technologies, and Their Planning Implications, Lund University Press, Lund, Sweden, 1989, pp 503-553. 15If the biomass is produced renewably, its use results in no net buildup of CO2 in the atmosphere. In addition, if the biomass is grown in plantations on previously deforested or unforested land, the buildup of the biomass inventory will extract CO2 from the atmosphere, and the steady-state inventory will be a reservoir of sequestered carbon. t6R.H. Williams, 'Biomass gasifier/gas turbine power and the greenhouse warming', paper presented at the IEA/OECD Expert Seminar on Energy Technologies for Reducing Emissions of Greenhouse Gases, Paris, France, 12-14 April 1989; E.D. Larson and R.H. Williams, 'Biomass-fired steam-injected gas turbine cogeneration', Journal of Engineering for Gas Turbines and Power, Vol 112, No 2, April 1990, pp 157-163. 17D.E. Carlson, 'Low-cost power from thin-film photovoltaics', in T.B. Johansson et al, pp 595-626, op cit, Ref 14. 18j.M. Ogden and R.H. Williams, Solar Hydrogen: Moving Beyond Fossil Fuels, World Resources Institute, Washington DC, USA, 1989.
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In order for nuclear power to make a major contribution to global energy, it would have to be made not only safe and cost-effective but also highly diversion-resistant. For nuclear power developed on a large scale, the current system o f international safeguards is inadequate to this challenge. What would be required are a redesign o f nuclear technologies, to make them far less attractive sources o f nuclear weapons-usable materials than existing and planned technologies, and an internationalization of sensitive nuclear facilities, as proposed in the 1946 Acheson-Lilienthal Plan. The nuclear industry must come to recognize that its long-term viability depends on its being able to offer a peaceful atom that is unambigously distinct from the military atom. Keywords: Nuclear power; Plutonium; Proliferation
Concern about the global greenhouse warming is leading to reconsideration of the nuclear power option. Two problems that must be dealt with effectively in order to have a resurgent nuclear industry the risk of reactor accidents and high cost - are being given focussed attention. But another important issue - the nuclear weapons connection to nuclear power - has been given scant consideration to date in the policy discussions revisiting the nuclear option. Inherent in nuclear technology is the fact that the chain-reacting materials that produce energy inside a reactor can also be used for making nuclear explosives. One of these materials, plutonium, a byproduct of the production of nuclear energy, is particularly worrisome. A one gigawatt (GW) light-water reactor (LWR), the dominant type in most of the world, discharges approximately 200 kg of plutoThe authors are at the Center for Energy and Environmental Studies, Princeton University, Princeton, NJ 08544, USA.
0301-4215/90/060543-07 (~) 1990 Butterworth-Heinemann Ltd
nium annually in its spent fuel - enough for more than 20 nuclear weapons. For a resurgent nuclear industry large enough to contribute substantially to reducing the greenhouse problem, the potential for diversion would be daunting. Suppose that concern about the greenhouse problem were to lead to a level of nuclear power for electricity and fuel applications adequate to replace one quarter of the present global level of fossil-fuel use. Such an emphasis on nuclear power could require a ten-fold increase in global installed nuclear capacity to 3 000 GW. In current reactors, a nuclear capacity of this magnitude would produce over 500 000 kg of plutonium per year. This is bad enough. But concerns about uranium supply at such a high level of nuclear power development would lead to pressures for the development of nuclear power systems based on 'plutonium-breeder' reactors in which plutonium bred in the reactor is routinely separated from spent fuel in nuclear fuel reprocessing plants and recycled in fresh reactor fuel. A 3 000 GW nuclear system based on plutonium-breeder reactors would place into global nuclear commerce approximately 5 000 000 kg of separated plutonium per year. It is difficult to imagine human institutions capable of safeguarding these plutonium flows against occasional diversions of significant quantities to nuclear weapons. Because of the high diversion risk inherent in a 'plutonium economy', an alternative nuclear system that is diversion-resistant as well as safe and costeffective would have to be developed before nuclear power could play a major role in the energy future of the world.
Criteria for diversion resistance The current system of applying international safeguards (inspections) on otherwise nationally-owned and operated nuclear power facilities would not be adequate to the task of uncoupling nuclear power and nuclear weapons technologies with nuclear power developed on a large scale.This truth was recog543
Diversion-resistance criteria for future nuclear power
nized at the beginning of the nuclear era. According to the March 1946 Acheson-Lilienthal Report: 1 We have concluded unanimously that there is no prospect of security against atomic warfare in a system of international agreements to outlaw such weapons controlled only by a system which relies on inspection and similar policelike methods. The reasons supporting this conclusion are not merely technical but primarily the inseparable political, social, and organizational problems involved in enforcing agreements between nations, each free to develop atomic energy but only pledged not to use bombs. To make nuclear power acceptably diversionresistant it is necessary to virtually eliminate access to weapons-usable materials - plutonium and uranium enriched in uranium-235 or uranium-233 to levels above some 10-20% 2 (ie containing less than 80-90% uranium-238, the presence of which renders low-enriched uranium unusable for weapons purposes). This implies a significant level of international control over nuclear power technology 3 - the central recommendation set forth in the A c h e s o n Lilienthal Report. We take this recommendation as a point of departure in exploring the prospects for making nuclear power sufficiently diversion-resistant that it could play a major role in the global energy future. We consider a nuclear power system consisting of two segments: international centres containing all sensitive nuclear technologies and activities that are maintained under tight physical security by the International Atomic Energy Agency, and national facilities that are maintained under the existing system of safeguards. Depending on the characteristics of the nuclear technology, the mix of centres and national facilities could range from almost all significant activity under international control to a relatively small number of international centres serving a large number of national facilities. Within such a framework, the nuclear power system should be designed to satisfy the following criteria: •
•
•
•
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Restrictions on sensitive nuclear technologies and materials shall be non-discriminatory among nations. Fissionable weapons-usable material that is not contained in spent fuel and facilities to enrich uranium or to separate plutonium shall not exist outside international centres. As far as possible, fissionable weapons-usable material that is not contained in spent fuel shall not be produced even at the international centres. Spent fuel shall be stored and disposed of in international centres.
Reactors under national authority shall be designed to reduce to very low levels the production of weapons-usable materials in spent fuel (of the order of a critical mass or less per year per gigawatt of capacity). The first criterion arises from the consideration that an international regime in which sensitive nuclear technologies and materials are available to some countries deemed 'safe' or 'non-proliferating' but denied to other countries regarded as 'proliferationp r o n e ' is i n h e r e n t l y unstable. A stable nonproliferation regime can be achieved only if the rules regarding the availability of nuclear technologies are the same for all countries. The requirement of the second criterion - that weapons-usable material does not exist outside international centres - would be a major deterrent to criminal or terrorist diversions of weapons-usable material. The third criterion, to minimize the production of separated weapons-usable material even at international centres, would be a valuable additional safeguard against such diversions. Experience has shown that nominally tight security systems safeguarding a wide range of valuable materials can occasionally be breached by sufficiently determined and clever groups. Satisfying the second and third criteria would also deny nations quick access to nuclear weapons-usable materials and thus largely eliminate the risk of 'latent proliferation', whereby nations move inexorably toward a nuclear weapons capability whether or not they have deliberately chosen to acquire nuclear weapons. 4 If civilian nuclear power programmes provided easy access to weapons-usable material, governments could proceed, at little cost, to a point but one step away from the acquisition of nuclear weapons, without actually making the final decision to go nuclear and without making their intentions clear in advance. But if nuclear weapons-usable material is not readily available, it would be easier for those opposed to acquiring nuclear weapons to prevail in government decisions relating to nuclear weaponry. It would be difficult to secure a consensus within the government bureaucracies of most nonnuclear weapons states on the desirability of acquiring nuclear weapons, because it is possible only in exceptional cases to make a persuasive case that security would be enhanced by having nuclear weaponry. Moreover, the longer the time required to acquire nuclear weapons, the greater the risk of 'getting caught'. Even if the second and third criteria were satisfied, substantial quantities of plutonium, albeit un-
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separated might still be contained in the spent fuel. While the plutonium in spent fuel is 'protected' against diversion by the intense radioactivity of the nuclear fission products and is therefore much less accessible than separated plutonium, it is feasible for a country intent on acquiring nuclear weapons to build, in a period of several months, a crude ('quickand-dirty') reprocessing facility adequate to extract enough plutonium from spent fuel inventories to make a few nuclear weapons. 5 The temptation to do this could become great in certain crisis situations. Therefore, the fourth criterion calls for delivering spent fuel discharged from national reactors as quickly as practicable to international spent fuel repositories. An advance commitment to deliver spent fuel to these repositories should be made a condition for any country's acquisition of nuclear technology. Even with the requirement to send spent fuel to international repositories, there would be opportunities to divert some spent fuel during the 'coolingoff' storage period at the reactor site or during transport. The last criterion, therefore, requires nuclear engineers to design nuclear reactors for use outside international centres in such a way as to minimize the quantities of weapons-usable materials in their fuel inventories and in the spent fuel discharged from them. If this criterion were met, the time required to obtain weapons-usable materials from spent fuel in crude reprocessing facilities would be so lengthened and the risk of getting caught would be so significantly increased that the incentive to mine the spent fuel or reactor inventories for weapons-usable materials would be greatly diminished. Meeting this criterion would also greatly decrease the incentive to eventually mine the spent fuel for commercial purposes, with all the attendant risks of using separated weapons-usable materials for nuclear fuel. Satisfying the criteria set forth here would not make nuclear power diversion-proof- no technical or institutional fix can do that. Nor would it prevent nations determined to acquire nuclear weapons from doing so. But satisfying these criteria would make the nuclear power route an unattractive one for acquiring nuclear weapons. To reduce proliferation risks to truly low levels, effective measures would also have to be taken to reduce the incentives of non-nuclear countries to acquire nuclear weapons. This would require nuclear-weapons states to reduce their dependence on nuclear weapons and to sharply separate their weapons programmes from their civilian nuclear power programmes. Specifically, the nuclear
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weapons states would have to move to curtail or halt altogether the production of fissile material for weapons and reduce their stockpiles of weapons. Such moves are more plausible now than they have ever been, in part because of recent political developments in the Soviet Union and Eastern Europe and the dramatic improvement in East/West relations. Moreover, the USA and the USSR are working toward substantial reductions in strategic and tactical nuclear weapons; for this reason, and also because of safety and environmental problems at weapons production complexes, discussions of a cutoff in fissile material production for weapons have begun in both countries. The restructuring of civilian nuclear power that we call for here would be an effective complement to such actions by the nuclear weapons states. Both courses of action are necessary to the establishment of an effective nonproliferation regime.
Discouraging reprocessing and plutonium recycling For the present generation of nuclear power plants operating on a 'once-through' fuel cycle, the risks of proliferation and criminal or terrorist diversion of nuclear weapons-usable materials are limited by the fact that weapons-usable material is never isolated. The fresh uranium fuel is dilute in the fissile isotope, uranium-235 (about 3%), and the plutonium produced in the reactor is not separated from the spent fuel. As long as the plutonium remains locked in the spent fuel, it is partially protected against diversion to nuclear weapons use by the intensely radioactive products of nuclear fission. But when nuclear fuel is reprocessed to recover the plutonium for use in fresh fuel, either in breeder reactors or in reactors of the current type, diversion risks increase sharply. 6 Consideration of ongoing recycling activities, though modest in scale compared to such activities in a full-blown 'plutonium economy' based on breeder reactors, gives an indication of the nature of these risks. France, Great Britain and Japan already have operating or under construction commercial-size reprocessing plants to separate plutonium from spent fuel. Under current reprocessing schedules, based on already negotiated nuclear fuel-reprocessing contracts, over 20 000 kg of plutonium will be separated annually by the year 2000 in Europe and Japan. Japan and several European countries have initiated programmes to recycle the separated plutonium in current LWRs. Under these programmes, it is
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planned to fabricate the separated plutonium into plutonium-uranium (mixed-oxide) fuel rods and recycle these in scores of reactors. As the programmes come to fruition, much of the plutonium being separated will be placed into commerce within Europe and between Europe and Japan. This commerce will involve hundreds of shipments annually by trucks, trains, ships and planes. Spent fuel will be sent from more than 100 reactors to reprocessing plants; the separated plutonium will be sent to fuel-fabrication plants; and the mixed-oxide fuel fabricated at these facilities will then be sent to the reactors using the mixed-oxide fuels. About half of the separated plutonium will be transported across international boundaries, including from Europe to Japan. The security challenges of protecting such shipments are suggested by the arrangement surrounding the first large shipment of plutonium from France to Japan: 7 In 1984, 250 kilograms of plutonium oxide, separated in France from spent fuel from Japanese reactors, was returned to Japan by cargo ship. The ship carried only the plutonium; it made no intermediate stops; it was escorted partly by French and US warships; and it was continuously tracked by satellites by officials in Japan. Thus large-scale commerce in separated plutonium will present a safeguards challenge of colossal proportions and is completely inconsistent with our criteria for diversion-resistance. Indeed, the diversion risks are so glaring that it is an implicit premise of the countries undertaking plutonium recycling that neither the separated plutonium nor the recycling technologies will be made available to the developing countries. While the countries undertaking the recycling are not themselves likely proliferators, they are deceiving themselves if they think that they will be able routinely to recycle tens of thousands of kilograms of separated plutonium annually while the rest of the world accepts the dictum that separated plutonium is not for them. Moreover, it is in the developing countries where much of the nuclear capacity would have to be located in a resurgent nuclear future. A global energy scenario emphasizing a variety of energy sources that would help cope with the greenhouse problem was developed in a recent study by the US Environmental Protection Agency. In this scenario, the developing countries' share of worldwide nuclear power increases from 2% in 1985, to 5% in 2000, to 38% in 2025, to almost 60% in 2050. 8 In this context it would not be realistic to expect that recycling technology could be utilized in Europe and Japan but denied to the developing
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world in the long run. Reconstructing nuclear power therefore requires that commercial reprocessing and plutonium recycling be halted and deferred indefinitely, and that emphasis instead be given to nuclear technologies which do not involve these activities. How realistic is it to expect that this can happen? The USA, Sweden and Canada have already abandoned these activities, and the Soviet Union is not believed to be pursuing reprocessing on a commercial level. Although it will not be easy to persuade countries still engaged in reprocessing and plutonium recycling to abandon these activities, there should be no resistance based on economic incentives. Several studies have shown that, at today's uranium prices, reprocessing and recycling in LWRs or in breeders is simply not economic. 9 Even where reprocessing can be considered a sunk cost, it may not be economic to recycle plutonium. Although the recycling would save some expenditures on uranium and enrichment, these savings would be offset by the extra costs for security at reactor sites to guard the separated plutonium, for fabricating the mixedoxide fuels, and for storing and processing the separated plutonium before it is fabricated and recycled. Although France currently finds reprocessing profitable and Britain also expects to, this is because other countries - primarily Japan - have helped to finance their reprocessing operations through longterm reprocessing contracts. Were these contracts not to be renewed, reprocessing might look economically unattractive even to France. Non-renewal of the contracts is not out of the question. Japan, West Germany, Sweden and some other countries originally sent their spent fuel to France and to Britain for reprocessing largely because of laws that required their nuclear industries to demonstrate how they would deal with spent fuel before nuclear power was allowed to expand further. The problem is 'solved' by sending the fuel out of the country but only temporarily, because the high-level waste and plutonium are to be returned. Furthermore, spent mixed-oxide fuel will probably have to be disposed of without reprocessing because it is difficult to reprocess, and the contained plutonium cannot be used again in LWRs. Nor is reprocessing required for waste disposal. Spent fuel and high-level waste pose broadly similar problems in terms of repository design for final disposal. The fission product contents are essentially identical, and the heat outputs per tonne of original uranium are similar for the first hundred years. 10
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Establishing international centres While the once-through system satisfies most of our first three criteria and provides a powerful safeguard against criminal and terrorist diversion and latent proliferation, the protection offered by oncethrough fuel cycles is not complete. Nations could still build quick-and-dirty reprocessing plants to separate plutonium from spent fuel. And, as long as some countries have the enrichment capacity needed to produce low-enriched uranium fuel, it will be difficult to deny indefinitely enrichment technology to other countries that want it. Accordingly, initiatives to establish various international nuclear centres should be launched concurrently with initiatives to stop reprocessing and plutonium recycling. One set of such centres is needed for repositories to receive and store spent fuel under international authority. Finding sites for such repositories that are acceptable to the public will be a major challenge. For example, it is already proving to be extraordinarily difficult to identify and establish acceptable sites for spent fuel storage in the United States; it is not easy to imagine a US citizenry willing to accept spent fuel produced in foreign nuclear power plants as well. But if some such sites can be identified, the internationalization of spent fuel repositories could facilitate other diversion-resistance initiatives. For countries with strong anti-nuclear movements, their establishment would 'sweeten' no-reprocessing agreements by providing these countries with a way to dispose of their radioactive wastes. International centres would also have to be established at existing as well as planned uranium enrichment facilities. This would be a major concession by the countries that already have enrichment capability, but so doing would be a major step toward establishing a non-discriminatory non-proliferation regime.
Redirecting nuclear research and development N u c l e a r p o w e r c a n n o t be m a d e a c c e p t a b l y diversion-resistant without a fundamental redirection of nuclear research and development away from plutonium-breeder reactors and plutonium recycling and toward nuclear technologies that hold forth the promise of being simultaneously cost-competitive, safe and diversion-resistant. Although reprocessing and recycling, as now c o n c e i v e d , c a n n o t be diversion-resistant, there may be uranium-efficient fuel cycles and technologies which can be made so. Alvin Weinberg has suggested that the use of
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accelerator breeders or fission-fusion hybrid breeders as neutron sources for producing uranium-233 in thorium might help make practical the concept of having a few international centres serving a much larger number of national facilities. The thorium would be reprocessed at the centres, and, after denaturing with natural uranium (which is 99.3% uranium-238), the recovered uranium-233 would be exported to national reactors. But such technology is far less developed than the plutonium-breeder reactor. According to Weinberg: 11 Though enthusiasm for these schemes runs high among the involved technical community, one must regard them as being largely unproven, economically if not technically. The engineering of such devices is formidable. Until we acquire actual engineering experience with accelerator breeders or fission-fusion hybrids, it would seem to me that their possible use need not concern us further. On the other hand, I am prepared to admit that over the very long run - say, 50 or more years, both . . . may become technically and economically feasible. In view of their potential contribution to a proliferation-resistant regime, continued serious study . . . seems justified. Even if the international-centre concept could be made to work, it still would not satisfy our last criterion that the reactors under national control s h o u l d not p r o d u c e substantial q u a n t i t i e s of weapons-usable material, unless the reactors were of a type different from any of those currently deployed. It is unclear at this time how far practical designs can be pushed in this direction while simultaneously satisfying concerns about cost and safety. However, c a n d i d a t e technologies having some potential diversion-resistant qualities have been advanced. One such technology, the high-temperature gascooled reactor (HTGR), has attracted interest as a system that offers significant safety advantages at small unit sizes over the current LWR. A modular (135 MW) version of the H T G R has been designed to operate on 20% enriched uranium. An H T G R operating on a denatured uranium-thorium oncethrough fuel cycle would discharge in spent fuel just 30 kg/y of plutonium per G W of capacity, 12 compared to 200 kg for a conventional L W R - not meeting our criterion but suggestive of what might be possible. Another technology which has recently received attention is the integral fast reactor (IFR), under d e v e l o p m e n t principally at A r g o n n e National Laboratory and based on a liquid metal-cooled reactor developed concurrently by General Electric and Argonne. The IFR would offer an element of diversion-resistance by co-locating the reactor, fab-
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rication plant and reprocessing centre, so that plutonium-bearing materials would not have to be transported outside the security boundaries of the site. But the fresh fuel of the reactor would be 25% plutonium, and this would imply a fresh fuel inventory of at least a few hundred kg of plutonium per GW of generating capacity. With the IFR a nation could acquire very large quantities of weapon-usable material, if it wished to do so. Therefore, the IFR would not satisfy our criteria for reactors under national control. The HTGR and IFR concepts have been advanced primarily because of safety concerns. A thorium-based LWR with a core designed explicitly to meet diversion-resistance critera has been proposed by Alvin Radkowsky, a nuclear engineer working in Israel. 13 The 'seed', which occupies about 15% of each core assembly, would be enriched to 20% or less U-235 and would consist of plates or rods of uranium oxide mixed with inert nonabsorbing oxides. The remainder of each core assembly, the fertile 'blanket', would consist of thorium-oxide rods, containing about 5% uranium oxide. The seed would be replaced about once a year, but the blanket would remain in for about 10 years. At discharge, the blanket would contain about 1% uranium-233 diluted with about four times as much uranium-238. The calculated plutonium production rate is less than 14 kg/y of plutonium per GW of capacity. Radkowsky estimates that his reactor concept would provide a gain of about 400% in uranium utilization efficiency over the current LWR.
Prospects for a diversion-resistant nuclear power regime Making future nuclear power systems diversionresistant would require unprecedented institutional changes. It would be much tougher to bring about the adoption of diversion-resistant criteria than it has been to get the nuclear industry interested in improving reactor safety, largely because of the global nature of the needed reforms and the fact that the price of diversion-resistance is some loss of national sovereignty and energy autarky. Fortunately, however, the growing energy supply competition to nuclear power as an energy strategy for coping with the greenhouse problem should lead many decision-leaders to recognize that nuclear power expansion does not have to be accepted at any cost. One important competitor to nuclear power is a new generation of high-efficiency, low unit capitalcost gas turbines. Fired with natural gas these tur-
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bines emit just two-fifths as much C O 2 a s coal-fired steam-electric plants per kWh of electricity generated. TM While natural gas supply constraints and the contribution of natural gas combustion to the atmospheric buildup of CO2 imply that natural gas-fired gas turbines should be viewed only as an interim energy strategy for the decades immediately ahead, gas turbines can also play a major long-term role if fired with biomass as fuel. 15 Advanced aeroderivative gas turbines offer relatively low unit capital costs and high thermodynamic efficiencies at the modest sizes (less than 100 MW) needed for biomass applications. The prospects are good for bringing to market in the early 1990s biomass-fired versions of such turbines that will be able to compete with both coal and nuclear power technologies in many circumstances, i6 It is very likely that solar photovoltaic (PV) technology will also begin to be used in power-generating applications, beginning in the 1990s, as rapid progress is being made in both high-efficiency, concentrating crystalline solar-cell and low-cost, thin-film technologies. The cost and performance outlook for thin-film solar-cell technology is so promising 17 that, as oil and gas supplies get tight, it will also make economic sense to consider using this technology to produce DC electricity and converting the electricity to hydrogen via electrolysis. If the cost and performance goals of thin-film solar cells set for the next decade by the PV industry are met, the produced hydrogen would probably be less costly than hydrogen produced from nuclear electricity, even if the nuclear industry's target capital costs for a resurgent nuclear power industry are realized, and would be roughly competitive with synthetic liquid fuels from coal. TM We are therefore likely to have alternatives to nuclear power in the post-fossil fuel era and can decide on our level of commitment to it on grounds of security, as well as cost, safety and environmental impact - ie nuclear power can now be judged by a higher standard than was thought possible a decade ago. Also, the nuclear industry must come to recognize that its long-term viability depends on being able to convince the public that it can offer a peaceful atom that is unambiguously distinct from the military atom. Unless this is accomplished, nuclear power is doomed as a major long-term energy option. While nuclear power might get a second chance, in light of greenhouse concerns, it would not be likely to get a third chance if there were a major diversion incident somewhere in the world that could be plausibly linked to nuclear power. The fundamental re-orientation of nuclear policy we are proposing cannot be accomplished overnight.
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It is critical, however, that it be well underway before the 1995 Review Conference of the NonProliferation Treaty, when the international regime for nuclear power will be renegotiated. An earlier version of this article was published in the Bulletin of the Atomic Scientists, April 1990. The authors are grateful to Robert Socolow and Frank von Hippel for extensive comments on early drafts of this paper.
1A Report on the International Control of Atomic Energy, US Government Printing Office, Washington DC, USA, 16 March 1946. 2J.C. Mark, T. Taylor, E. Eyster, W. Maraman and J. Wechsler, 'Can terrorists build nuclear weapons?', paper prepared for the International Task Force on Prevention of Nuclear Terrorism, 24 May 1986. 3L. Scheinman, 'Multi-national alternatives and nuclear nonproliferation', in G. Quester, ed., Nuclear Proliferation: Breaking the Chain, University of Wisconsin Press, Madison WI, USA, 1981, pp 77-102. 4H.A. Feiveson, 'Proliferation-resistant nuclear fuel cycles', Annual Review of Energy, Vol 3, 1978, pp 357-394. 5Comptroller-General of the United States, Quick and Secret Construction of Plutonium Reprocessing Plants: A Way to Nuclear Weapons Proliferation? US General Accounting Office, Washington DC, USA, 1978. 6D. Albright and H. Feiveson, 'Why plutonium recycle?' Science, Vol 235, 27 March 1987, pp 1555-1556; D. Albright and H. Feiveson, 'Plutonium recycling and the problem of nuclear weapons proliferation', Annual Review of Energy, Vol 13, 1988, ~L p 239--265. .S. Spector, The New Nuclear Nations, Vintage, New York, USA, 1984. 8Office of Policy, Planning and Evaluation, United States Environmental Protection Agency, Policy Options for Stabilizing Global Climate, draft report to Congress, February 1989.
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9OECD, The Economics of the Nuclear Fuel Cycle, Paris, France, 1985; Plutonium Fuel: An Assessment, Paris, France, 1989. t°OECD, Nuclear Spent Fuel Management: Experience and Options, Paris, France, 1986. HA.M. Weinberg, 'Nuclear energy and proliferation: a longer perspective', in A. Weinberg, M. Alonso and J.N. Barkenbus, eds, The Nuclear Connection: A Reassessment of Nuclear Power and Nuclear Proliferation, Paragon House Publishers, New York, USA, 1985, pp 221-239. 12H.A. Feiveson, F. yon Hippel, and R.H. Williams, 'Fission power: an evolutionary strategy', Science, Vol 203, 26 January 1979, pp 330-337. 13A. Radkowsky, 'The nonproliferative light water thorium burner concept', Tel-Aviv University, undated manuscript received baYRthe authors in 1988. .H. Williams and E.D. Larson, 'Expanding roles for gas turbines in power generation', in T.B. Johansson, B. Bodlund and R.H. Williams, eds, Electricity: Efficient End-Use and New Generation Technologies, and Their Planning Implications, Lund University Press, Lund, Sweden, 1989, pp 503-553. 15If the biomass is produced renewably, its use results in no net buildup of CO2 in the atmosphere. In addition, if the biomass is grown in plantations on previously deforested or unforested land, the buildup of the biomass inventory will extract CO2 from the atmosphere, and the steady-state inventory will be a reservoir of sequestered carbon. t6R.H. Williams, 'Biomass gasifier/gas turbine power and the greenhouse warming', paper presented at the IEA/OECD Expert Seminar on Energy Technologies for Reducing Emissions of Greenhouse Gases, Paris, France, 12-14 April 1989; E.D. Larson and R.H. Williams, 'Biomass-fired steam-injected gas turbine cogeneration', Journal of Engineering for Gas Turbines and Power, Vol 112, No 2, April 1990, pp 157-163. 17D.E. Carlson, 'Low-cost power from thin-film photovoltaics', in T.B. Johansson et al, pp 595-626, op cit, Ref 14. 18j.M. Ogden and R.H. Williams, Solar Hydrogen: Moving Beyond Fossil Fuels, World Resources Institute, Washington DC, USA, 1989.
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