7 Nuclear Warhead Dismantlement and Possible Reuse in Civil Nuclear Power Reactors

Transcription

1 7 Nuclear Warhead Dismantlement and Possible Reuse in Civil Nuclear Power Reactors Cesare Silvi INTRODUCTION The question of what to do with the nuclear warheads from missiles that may be dismantled, and with the nuclear materials they contain, has been gaining new attention in recent years. 1 But so far the agenda for the disarmament process, which at last appears to be taking off, has not included provisions for dismantling nuclear warheads. And if the Intermediate-range Nuclear Forces (INF) Treaty, signed on 8 December 1987, continues to be a model, the warheads would be removed from the missiles before they are destroyed, and each side would retain them to use on other missiles or to make other warheads. An alternative to the INF approach, which may or may not be considered at the negotiating table on Strategic Arms Reduction Talks (START), would require dismantlement of the warheads, and an agreement not to use the materials they contain to make new warheads. These materials could be reused for peaceful purposes or irretrievably disposed of. This chapter focuses mainly on issues related to the conversion of weapon-grade nuclear materials from dismantled nuclear warheads to fuel civil nuclear power reactors. The main technical aspects as well as the economic and political implications of dismantlement or conversion are examined. Attention is also given to the implications for the nuclear non-proliferation regime. For one central point of the Non-proliferation Treaty (NPT) is that, on the one hand, it promotes nuclear technology, and, on the other hand, it tries to prohibit its military use. Since the Treaty was ratified, however, these major goals have not been pursued as expected. For states possessing C. Schaerf et al. (eds.), Reducing Nuclear Arsenals Unione Scienziati per il Disarmo Convegno Internatzionale

2 98 Nuclear Warhead Dismantlement and Civilian Reuse nuclear weapons have failed to fulfil their obligation under Article VI to negotiate 'in good faith' to halt the nuclear arms race 'at an early date', and the nuclear powers have maintained their monopoly on nuclear technology. As the United States and the Soviet Union are pursuing a deescalation of tensions, an effort at international non-proliferation might receive further impetus were they to change their attitudes towards the disposal of nuclear warheads as well as towards the future development of nuclear power for civilian application. Such a development might be required in both the industrial and the developing countries over the next century on an even larger scale than is envisaged today, because of concerns about the assurance of energy supplies and the environment. Further strengthening of the nonproliferation regime might be required to make this acceptable and possible. THE DISMANTLEMENT OF NUCLEAR WARHEADS Dismantlement Options and Possible Political Implications To date the dismantlement or conversion of nuclear warheads to civilian purposes has never been associated with or facilitated by an arms control or arms reduction agreement. The INF Treaty specifically exempts nuclear warheads and associated guidance systems from dismantlement, and it is not clear what the START negotiations will provide. If provisions for the dismantlement of warheads are written into future arms control or reduction treaties, several options can be considered for the disposal or reuse of the fissile materials they contain, in order to make them unfit for military use. The uranium-235, plutonium and tritium could be stored indefinitely; or the plutonium could be contaminated to make it unfit for military use and then disposed of as a nuclear waste; or it could be disposed of into outer space or the environment in ways that would make it difficult to retrieve; or it could be used as a fuel for civil nuclear power plants. Including these options in future treaties could have several positive effects in promoting the goal of full nuclear disarmament. First, they would remove these materials from the military circuit and make them unavailable for weapons. Secondly, they would prove the

3 Cesare Silvi 99 superpowers' commitment to Article VI of the NPT, opening the way to its full application. Replacing 'vertical proliferation' with 'vertical reduction' of nuclear arsenals could thus not only increase confidence and mutual trust between the superpowers, but also strengthen the commitment of non-military nuclear states to continue to renounce nuclear weapons. In addition, nations which have not signed the NPT, and would like to possess nuclear weapons, would have less justification in proceeding with their aims and would be more subject to pressure by the international community to commit themselves not to develop nuclear technologies for military purposes. Finally, providing for nonmilitary reuse of dismantled nuclear warheads might strengthen support from non-nuclear weapons states in 1995, when extension of the NPT will be decided by international vote. These options would be only symbolic, however, if they were not paralleled by initiatives aimed at stopping the production of the materials for weapons. To be irreversible, the nuclear disarmament process should include not only those options, but also provisions for converting facilities for the production of nuclear weapons. It is a matter of record that such complexes, both in the United States and in the Soviet Union, have experienced several problems. Despite the progress on disarmament, plans exist in both countries to modernise them. In the United States the total cost would run to around US$80 billion. 2 Nuclear Warheads and their Fissile Materials The total number of the superpowers' nuclear warheads and the amount of weapon-grade fissile materials they contain provide a significant measure of the problems involved in dismantling and converting them. Estimates of current nuclear arsenals worldwide are shown in the Table 7.1. In particular, it shows the estimated amount of weapon-grade fissile materials contained in various forms in the nuclear arsenals of the two superpowers. With the signing of the INF, about 4000 warheads were to be made non-operational. Dismantling them would make about 40 tonnes of weapon-grade fissile materials available. Prospective 50 per cent cutbacks of strategic nuclear arsenals based on ballistic missiles would make an estimated amount of 200 tonnes of weapon-grade material available. These figures give a general idea of the scale of the problem in the short term. In the long run, larger figures might be envisaged, considering the

4 100 Nuclear Warhead Dismantlement and Civilian Reuse Table 7.1 The world's present nuclear warheads (estimate) The world's nuclear warheads United States Soviet Union United Kingdom France China Israel South Africa Pakistan India World total US and Soviet nuclear warheads Strategic Land-based missiles Submarine-launched missiles Bombs Sub-total Nonstrategic Aircraft bombs and missiles Land-based missiles Submarine-launched ballistic missiles Submarine-launched cruise missiles Antiballistic and surface-air missiles Artillery Antisubmarine Demolition (ADM) Sub-total ??? about us USSR ? Nuclear materials in US and Soviet nuclear warheads Material us USSR Total Plutonium ( tonnes) Highly enriched uranium (tonnes) Tritium {kg) ? 200? Source: T. B. Taylor, 'Verified Elimination of Nuclear Warheads', Science and Global Security, vol. I (1989).

5 Cesare Silvi 101 prospects for substantial reduction in the nuclear arsenals of the superpowers, and perhaps other nuclear powers as well, all the way down to a 'minimum deterrence' of, say, one per cent of the present strategic arsenals, or even, eventually, zero. 3 If all military nuclear materials were pooled for reconversion to peaceful uses, all the nuclear reactors in the world could feed exclusively on them for nearly seven years. The uranium-235 in the world's stockpiles of nuclear warheads is a potential energy resource worth more than US$30 billion. 4 THE USE OF FISSILE MATERIALS RECOVERED FROM WARHEADS TO FUEL CIVIL NUCLEAR POWER REACTORS Use in Current Nuclear Power Reactors Depending on their design, today's nuclear power reactors can be fuelled with normal uranium, low-enriched uranium (LEU), highlyenriched uranium (HEU) or plutonium. Since there are few peaceful uses for it today, tritium is not considered here. Enriched uranium from dismantled nuclear weapons could be diluted with normal or depleted uranium to produce LEU. Weapongrade uranium is highly-enriched (typically 90 or 93 per cent), while the uranium used in most thermal reactors requires enrichment in the range of 3 to 4 per cent. Dilution has the advantage of transforming weapons material into material that has no military applications. However, it wastes the money invested in full enrichment. If the cost of converting and diluting weapon-grade uranium is taken into account, the economic balance will still be positive, but small. Availability of extra quantities of reactor fuel may well create more problems than it solves: today there is an abundance of commercial enriched uranium, and overcapacity in enrichment plants is already creating economic problems. In principle, HEU can be used as an initial fuel for breeder reactors. Since the enrichment needed in this case is only 25 per cent, less dilution would be required than for standard thermal reactors, but still enough to make uranium unfit for military purposes. The option of using uranium rather than plutonium in breeder reactors was originally motivated by the fear that not enough plutonium would be available for accelerated start-up of a fast reactor

6 102 Nuclear Warhead Dismantlement and Civilian Reuse programme. This argument cannot reasonably be sustained today, given the prospects for slow development of breeder reactor programmes and availability of plutonium stocks. Finally, HEU can be used in research reactors, which generally use 20 or 90 per cent enriched uranium (20 per cent has been favoured lately as a protection against proliferation). However, the small demand for this fuel is currently dwindling as the number of research reactors in operation decreases. Plutonium is another possible supplementary nuclear fuel for conventional thermal reactors. Plutonium is used in this case in a proportion of about 3 to 4 per cent with natural or depleted uranium, in the form of mix oxides. This use would not facilitate the diffusion of nuclear energy, since, as we have seen, there is no scarcity of either natural uranium or enrichment capabilities at present or in the foreseable future. Furthermore, while using plutonium in thermal reactors would not appreciably affect their safety characteristics, it would create potential diversion or proliferation problems during transportation or storage. The use of plutonium in commercial thermal reactors is therefore possible but hardly convenient at present and at least for some time in the future. Plutonium might also be used to fuel breeder reactors. However, the use of military plutonium in breeder reactors (rather than recycled plutonium from commercial reactors) would be limited in its economic value, and the environmental and safety aspects, while positive, would be equally limited. The main obstacle is that no large-scale diffusion of breeder reactors can be expected in the next 20 or 30 years. Use in Innovative Nuclear Reactors Proposals for designing innovative nuclear power reactors - usually labelled 'passively safe', or sometimes 'inherently safe', and less technically known as 'walk-away' or 'forgiving' reactors - are under consideration in several countries. They are being studied in order to demonstrate their ability to meet more stringent safety requirements. Limitations on the radioactive sources and the efficiency of containment structures are expected to reduce their external impact to a level so low as not to require a contingent emergency plan. Present designs of innovative reactors envisage reactor fuels basically no different from those employed in existing thermal and breeder reactors. However, core and plant design of innovative

7 Cesare Silvi 103 reactors could change some of the characteristics of the out-of-pile cycle, because of the longer in-core residence time -larger than that used in current reactors - for the fuel sub-assembly and of the possibility to postpone the reprocessing of the irradiated fuel, even at the moment of reactor decommissioning if a limited storage capacity in the plant (two to three cores) is provided. As insurance policies for the further development of nuclear energy a high-efficiency process for separating fission products from the long-life transuranium nuclides in the irradiated fuel are also being explored, for example in France, as well as specific reactor systems to burn them (actinides burners, that is fast reactors that simultaneously transform plutonium and transplutonium isotopes into fission products as they produce energy). 5 All these developments might offer additional options, besides those already examined, for recycling fissile materials from dismantled warheads to peaceful uses. OBSTACLES AND OPPORTUNITIES IN CONVERTING WEAPON-GRADE NUCLEAR MATERIALS Verification and Safeguards Were arms control treaties to require the dismantlement of nuclear warheads and the conversion of the fissile materials they contain to peaceful uses, they would need to provide for two distinct aspects of controlling compliance: verification and safeguards. Verification must assure the signatories of disarmament treaties that commitments to dismantle nuclear weapons and to make their nuclear materials available for peaceful uses are actually fulfilled. Safeguards ensure the nuclear material thus recuperated is properly accounted for and is not diverted to military uses either by the nation where the material originates, or by any other nation or subnational group. These two types of controls could be carried out in succession, the first in what is essentially still a military environment, the second in a civilian environment. It is important to define the interface between the military and the civilian environment, and to attempt to foresee who would be in charge of controls, and what means would be used. Verification could be arranged through bilateral US-Soviet teams, safeguards by placing the materials under the aegis of the International Atomic Energy Agency (IAEA). The IAEA would seem to

8 104 Nuclear Warhead Dismantlement and Civilian Reuse provide the most reasonable solution for the civilian part of the controls (safeguards). It has the most experienced safeguards system, and has worked with essentially good results, especially when local authorities have been cooperative. On the other hand, it is unlikely that the IAEA can contribute to verification during the military stage of the conversion process. The signatories of the treaties, which are the parties directly concerned, would have to agree on bilateral procedures that give them enough confidence concerning respect for the agreements. Commercialisation: Problems and Opportunities Putting nuclear material from dismantled weapons on the civilian market is likely to meet difficulties and opposition, at least from those segments of this market that are based today on free competition, and to create problems in the use of government facilities in the other segments. The difficulties derive essentially from the fact that the civilian market for nuclear materials, when based on free competition, is currently a buyers' market, where offer exceeds demand, and production facilities run at only a fraction of their capacity. Putting more material on this market would further depress the conditions of the nuclear fuel cycle industry, which could therefore be expected to oppose it. As pointed out earlier, however, concerns about the assurance of energy supplies and the environment might require further expansion of nuclear energy over the next century, causing demand to grow again. But the future revival and expansion of nuclear energy seem possible only if a new generation of nuclear reactors is developed. To this end East-West cooperation might be envisaged and framed to also include prospects for conversion of nuclear weapon material to peaceful purposes. 6 Given the resurfacing of concerns about energy and environmental security, as well as the prospects for substantial cuts in nuclear arsenals, such an East-West cooperation programme could significantly contribute to making disarmament less potentially reversible and NPT obligations more likely to be met. CONCLUSION To be effective and credible, agreements on substantial reduction in nuclear arms must include provisions for conversion of their nuclear

9 Cesare Silvi 105 materials into a form that makes them unfit for further military use, and hopefully for their profitable civilian use; for the termination of the production of nuclear material for new weapons; and for the conversion of the relevant production and research facilities to peaceful uses. It is possible to use nuclear material for peaceful purposes. This could indeed have some positive economic aspects though it cannot be expected to change the prospects for nuclear energy significantly. Its main political value is political and symbolic, and lies in reducing the threat of global nuclear war. Highly enriched uranium is the most abundant weapons material; it is also the easiest to convert. Its dilution either to 20 to 25 per cent enrichment for possible special uses, or directly to 3 to 4 per cent for present commercial uses, would nullify its military value, after which it could enter the market on the normal terms of need and demand. Plutonium cannot, however, easily be denaturated so as to avoid improper uses. Although some solutions have been proposed, they are all incompatible with subsequent economic utilisation. It may be necessary therefore to store it safely as we wait for effective utilisations which today are theoretically possible but difficult to implement. Several other problems, not strictly technical, must be solved to make peaceful utilisation of nuclear weapon material possible and fruitful. They include finding effective and acceptable verification and safeguarding procedures; and identifying suitable ways of introducing such materials in the marketplace, probably by creating additional demand. In this respect it is worth exploring the possibility of creating ties between the development of future nuclear power and the disarmament process, such as East-West cooperation on the development of innovative reactors to be used over the next century. These ties would significantly contribute to making disarmament less potentially reversible and NPT obligations more likely to be met. 7 Notes 1. The two basic nuclear weapons materials are uranium-235 and plutonium (these are called 'fissile' materials). 'Weapon-grade uranium' means uranium enriched at or above 90 per cent in the isotope uranium-235. Natural uranium is composed of 99.3 per cent uranium-238 and about 0. 7 per cent uranium-235; the enrichment usually adopted in the most common commercial reactors, the Light Water Reactors (LWRs), ranges from 3 to 4 per cent uranium-235. According to the open literature, the minimum amount of uranium-235 needed for a warhead is about 10 kg, while that of plutonium is 3 to 7 kg. A few grams of tritium also is used in some warheads to boost their explosive yield. The problem of warhead dismantlement has

10 106 Nuclear Warhead Dismantlement and Civilian Reuse been addressed by several authors in recent years. See, for example, T. B. Taylor, 'Verified Elimination of Nuclear Warheads', Science and Global Security, vol. 1 (1989) pp. 1-23; W. H. Donnelly, 'Nuclear Arms Control: Disposal of Nuclear Warheads', Congressional Research Service Issue Brief, The Library of Congress, updated 24 May 1989; and E. Amaldi, U. Farinelli and C. Silvi, 'Conversion of Weapon-Grade Nuclear Materials to Civilian Purposes', paper presented to the Workshop on International Security and Disarmament: The Role of the Scientific Academies, Accademia Nazionale dei Lincei, Rome, 6-8 June President's Report to the Congress, 'United States Department of Energy Nuclear Weapons Complex Modernisation Report', Washington D. C., December Several recent studies suggest 'minimum deterrence' should consist of around 1000 nuclear warheads in the superpowers arsenals. See for example, M. Anjali Sastry, Joseph J. Romm, and Kosta Tsipis, 'Can the US Economy Survive a Few Nuclear Weapons?', Technology Review, April1989, pp Taylor, 'Verified Elimination of Nuclear Warheads'. 5. G. Cicognani, 'Research and Development Activities on Innovative Reactor Concepts in Italy of Potential Interest for a Long-Term Non Proliferation Policy', paper presented to the 55th Pugwash Symposium on Non-Proliferation and Non-Proliferation Treaty, Dublin, 5-7 May C. Silvi, 'Nuclear Power and East-West European Co-operation', paper presented to Conference on Technology-Based Confidence Building Energy and Environment, Los Alamos National Laboratory, New Mexico, 9-14 July The views expressed in this paper reflect only the opinions of the author. The paper is partly based on previous research carried out by the author together with Edoardo Amaldi and Ugo Farinelli.