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"The existence of this surplus material [plutonium and highly enriched uranium] constitutes a clear and present danger to national and international security. None of the options yet identified for managing this material can eliminate this danger; all they can do is to reduce the risks."
National Academy of Sciences' 1994 report on plutonium(2)
With the end of the Cold War, weapons-usable fissile materials have emerged as one of the most important security threats to the world. Surpluses of plutonium and highly enriched uranium have arisen from the dismantling of unwanted nuclear warheads. As the Soviet Union disintegrated in the early 1990s, and as the Cold War arrangements of influencing smaller countries in the world gave way to uncertainty, the possibility has increased that some of these surpluses (or even the nuclear warheads themselves) may be sold illegally, with unpredictable human, military, political, and environmental consequences. In a crisis, Russia or the U.S. could reuse some of these fissile materials from dismantled weapons to make new warheads. This would likely result in a similar response from the other side. Therefore, ready availability of weapons-usable fissile materials would make it easier and faster for one side to reignite the arms race. It also makes non-proliferation policy less effective, since non-nuclear-weapons states are less likely to believe that surplus plutonium and HEU will not again be used in weapons if these materials remain in weapons-usable forms.
Plutonium
Plutonium is made by the irradiation with neutrons of uranium-238 in military as well as civilian nuclear reactors.(3) In order to be used in weapons, plutonium must first be separated from un-used uranium and from fission products in the reactor fuel and target rods. This chemical separation process, known as reprocessing, is one of two key technologies in the production of nuclear-weapons-usable fissile materials. (The other technology is uranium enrichment -- see below.)
Plutonium from civilian reactors as well as that from military reactors can be used for making nuclear weapons. There are some important differences between the characteristics of plutonium produced in the most common civilian reactors (light water reactors), and military plutonium. The former, known as "reactor grade plutonium" has a larger proportion of plutonium isotopes other than plutonium-239, the one most suitable for weapons. These other isotopes, notably plutonium-240 and plutonium-241 (as well as americium-241, which is the decay product of plutonium-241), make it somewhat more complex to make a nuclear weapon of predictable yield from reactor grade plutonium, whose use also entails larger radiation doses to workers. Neither of these factors is an effective obstacle to the proliferation problems posed by separated plutonium of civilian origin.
Reactor-grade plutonium has 19 percent or more of plutonium-240, and typically contains 55 to 60 percent plutonium-239. Weapon-grade plutonium has 7 percent or less of plutonium-240, with almost all the rest being plutonium-239. Appendix B shows some important nuclear, physical, and chemical properties of plutonium.
Table 1 shows approximate estimates of the global stocks of plutonium, separated as well as unseparated from irradiated fuel rods, as of 1990.
Table 1
| Type of plutonium | Metric tons |
|---|---|
| Military plutonium | 248 |
| Civilian plutonium, separated | 122 |
| Plutonium in civilian spent fuel, unseparated | 532 |
Source: For U.S. military plutonium, Grumbly 1994; for all other data, Albright et al. 1993, p. 197. For this table Albright et al.'s estimate of U.S. military plutonium of 112.2 metric tons (pp. 34-35) was subtracted from their global total and replaced with the official DOE production figure of 103.5 metric tons.
Note: These estimates are being refined as more recent data are analyzed.
The global surplus of plutonium is being increased by separation of plutonium from civilian nuclear power reactor spent fuel. The global cumulative amount of such plutonium through the end of 1980 in all countries was estimated to be about 39 metric tons; it increased about three-fold to about 122 metric tons by the end of 1990. During the same period, a number of countries abandoned or drastically scaled down breeder reactor programs designed to use much of this plutonium, mainly because these programs could not be justified economically. Only about 50 metric tons of this separated plutonium had been used in reactors by 1990; some of that was sitting in the cores of shut-down breeder reactors, and hence was not actually being used. The surplus of civilian plutonium is projected to greatly increase if reprocessing is not drastically curtailed.(5)
It has also become clear in the last two decades that economically recoverable world resources of uranium are much larger than estimates made in the 1950s and 1960s, when plutonium separation was deemed by many to be essential to the future of nuclear energy. In the past few years a number of analyses in the United States have convincingly demonstrated that plutonium is not economical as an energy source and will not be for the foreseeable future because of the high costs of breeder reactors, of reprocessing, and of fabrication of fuel containing plutonium.
These analyses have examined the least expensive of the options for using plutonium for electricity production. This involves converting plutonium into plutonium dioxide, mixing it with uranium dioxide (the fuel form used in the most common nuclear power reactor design in the world today, the light water reactor) to obtain "mixed oxide" fuel (abbreviated as MOX fuel). The costs of plutonium processing are so high that even if the separated plutonium is considered free, a reasonable assumption for surplus plutonium from unwanted nuclear warheads, uranium is still cheaper as a nuclear power plant fuel. John H. Gibbons, President Clinton's Assistant for Science and Technology, summed it up succinctly in Congressional testimony in May 1994: "Contrary to some claims, there is no money in plutonium - except, perhaps on the nuclear black market."(6)
We will not repeat the analyses that have already been made in previous studies, notably the 1994 study on plutonium disposition by the National Academy of Sciences, (7) a 1993 analysis of fissile materials by the RAND Corporation, (8) and a 1992 study by Berkhout and his colleagues at the Center for Energy and Environmental Studies at Princeton University. (9) The basic conclusion regarding the economics of nuclear reactor fuel is very clear. The prevailing spot price of uranium oxide (yellowcake) is well below $10 per pound. (10) According to the RAND analysis , if the cost of reprocessing is taken to be equal to the charges for reprocessing of about $1,600 per kilogram of heavy metal (approximately equal to the combined uranium and plutonium content of the spent fuel) and the yellowcake price is assumed to be $10 per pound, MOX fuel would not be competitive until uranium oxide prices increased about 16-fold to $160 per pound. Further, according to the same analysis, even if the capital cost of the reprocessing plant is ignored, MOX fuel would not be competitive until uranium prices quintupled. (11) The RAND report's conclusions are similar to those in the earlier analysis by Berkhout et al. (12)
The prospects that plutonium will ever be an economical energy source are very slim. However, proponents of civilian plutonium use in countries such as Japan and France, which do not have large domestic supplies of fossil fuel resources, have argued that development of the technology for plutonium use is essential for the very long-term future; they claim that there are no viable alternatives to plutonium on the scale of energy supplies that they are likely to require. Such arguments are especially forceful in Japan which does not appear to have ample domestic uranium resources and where the land area for potential development of solar energy is very limited.
The modest theoretical merit of such arguments is overwhelmed by a number of realities. First, the danger of plutonium diversion is very real, especially in the context of continued economic, political and military instability and uncertainty in the former Soviet Union. Continued arguments that some countries need plutonium separation now for potential use in some distant future only encourages further plutonium separation and development of ancillary facilities in Russia.
The risk of diversion exists in all countries, though it is now most acute in Russia. The large-scale use of plutonium in the civilian sector will create new opportunities for diversion and for involvement of organized criminal elements in the traffic. Finally, the use of civilian plutonium in Western Europe and Japan creates obstacles to the stopping of reprocessing in Russia by depriving the United States of important leverage in dealing with Russia. The U.S. can hardly turn a blind eye to reprocessing in Western Europe and Japan while persuading Russia to stop.
Second, the security benefits of rapidly vitrifying separated plutonium are great and incalculable, while the costs of vitrifying plutonium, especially if it is done without mixing fission products in the glass, are relatively modest. The technology for re-extracting plutonium from glass is known, should plutonium ever become an economical fuel. There is therefore no need to continue to operate reprocessing plants to produce more plutonium that is uneconomical today and will remain so for decades, at least. The lead-time needed for construction of re-extraction facilities, should such facilities ever be necessary, is far shorter than any reasonable projected time in which plutonium may become economical as a fuel. The self-sufficiency argument therefore has essentially no merit in the near- and medium-term, since plutonium use cannot contribute to self-sufficiency in this time-frame. Japan will continue to be dependent on both imported oil and uranium. This reality has prompted a proposal that Japan should stockpile uranium, instead of plutonium, since uranium is plentifully available at low prices. (13)
More broadly, the self-sufficiency argument is rather weak. It received a strong impetus in many countries, including France and Japan, from the sudden increase in oil prices during 1973-1974 and from the embargo imposed by Arab oil exporting countries against the U.S. in late 1973. Many analysts incorrectly believed that exportable oil supplies could be monopolized by a few countries. Since oil was a vital commodity at risk of being cut-off, the argument went, self-sufficiency, or something near to it, was a security and economic imperative.
However, oil, like uranium, has turned out to be far more plentiful than presumed by the self-sufficiency analysis. Natural gas is also more abundant than once thought. There are far more oil exporting countries in 1994 than there were 20 years ago. The increases in the price of oil in the 1973-1980 period were not related to a physical dearth of supply, but to control of exportable supplies by a few countries, which could not be sustained.
If there is an argument for self-sufficiency in energy, it should apply with greater force to food, especially so far as Japan is concerned. Japan imports most of its food supply since domestic food production cannot provide for its present consumption level and pattern. Moreover, Japan has not experienced an oil cut-off, but it has seen one imposed on an essential foodgrain. In 1973, a few months before the Arab oil embargo against the U.S., President Nixon briefly banned all exports of soybeans as part of his program to curb the sudden price increases of commodities and to control inflation. Yet Japan did not set itself the goal of self-sufficiency in food, even though its closest military ally did not prove to be a fully reliable supplier of food grain. Rather, it diversified its sources of supply, largely by importing more soybeans from Brazil.
Japan could not sustain anything near its present level of use of resources without continuing to import many other essential commodities. High exports are the necessary counterpart to high imports. In the context of this economic reality, energy independence is an exaggerated and obsolete policy response. Whatever modest merit there might be in energy independence arguments made in Japan and France in support of plutonium separation is far outweighed by the negative security consequences of reprocessing, even if all adverse economic and environmental factors are ignored.
Russia has even less reason to stick with civilian plutonium production because it has huge reserves of various forms of energy, including fossil fuels and uranium. There is also immense room for improving energy efficiency in Russia. Further, Russia has been the scene of the worst civilian and military accidents of the nuclear era, namely the fire in one of the reactors at Chernobyl in 1986 and an explosion in a high-level radioactive waste tank at the Chelyabinsk-65 nuclear weapons plant in 1957. The frequency of accidents in recent years as well as the past record of despoliation of the environment are further reasons for Russia to reconsider its nuclear policies; many people in Russia are working toward that end. Britain also has plentiful fossil fuel reserves, and is an oil exporter. (14)
In contrast to a distant theoretical possibility that plutonium may one day be an economical energy source is the real evidence of a developing black market in fissile materials, including plutonium. The most serious confirmed incident involved and attempt to smuggle about 350 grams of plutonium in Germany; this is not enough plutonium for a nuclear warhead, but more than enough for a radiation dispersal weapon. It is possible that this sale of black market plutonium, originating to all appearances in the former Soviet Union, was in response to a demand created by German secret police to learn more about the potential supply situation. What has been learned is alarming. This incident has shown that plutonium availability depends on the demand for it and indicates that other countries or groups wanting to purchase plutonium could also similarly acquire it. Unlike the German government (which has a large stock of separated plutonium), groups or countries wanting to acquire plutonium for clandestinely building nuclear warheads or radiation dispersal weapons would hardly advertise their successes. In fact, there is no way for the world to know whether any plutonium and highly enriched uranium have already been sold, and if so, how much and to whom. There are still no adequate materials accounts of Soviet production of these materials. Nor are there any transparency and safeguards arrangements in place that would allow a determination of the quantities and flows of the materials. The progress on putting such measures into place has been very limited and far short of the need.
Finally, there is the potential that one or more of the many non-nuclear weapons states that are signatories to the Non-Proliferation Treaty (NPT) and that own separated plutonium could change their minds, and either openly or clandestinely make nuclear weapons. Indeed, the very fact of this potential is an incitement to proliferation, because it increases the level of suspicion between countries. The most notable example is the tension between North Korea and Japan regarding nuclear weapons. North Korea, pointing to Japan's imperialist past, claims that Japan may well make and use nuclear weapons, and that it possesses the technical capability and materials to do so. North Korea's failure to comply with inspection demands by the International Atomic Energy Agency (IAEA), has in turn, tentatively raised questions in Japan regarding a potential Japanese nuclear deterrent. These military and political tensions, arising partly from plutonium production in both North Korea and Japan, should be an additional powerful consideration against continued plutonium production and for creating and implementing a policy for disposition of already separated plutonium.
Highly Enriched Uranium (HEU)
As U.S. and Russian nuclear arsenals are reduced, large amounts of HEU, the other fissile material that can be used to make nuclear weapons, are also becoming surplus to weapons requirements, along with military plutonium. While both HEU and plutonium are weapons usable materials, there are some differences between them. HEU is generally not used in civilian power reactors. (15) Another contrast to plutonium is that HEU is not made in nuclear reactors.
HEU is a special mixture of isotopes of uranium that is made by increasing the uranium-235 content of natural uranium by a process called "enrichment." Natural uranium contains only 0.711 percent uranium-235, the fissile isotope of uranium. Almost all the rest is uranium-238, which is not fissile, though it is the raw material for the production of plutonium-239, which is fissile. (16) The process that is used to make enriched uranium also creates a waste stream of depleted uranium, so called because it contains less fissile uranium-235 than natural uranium.
Uranium must be enriched to high levels of uranium-235 content in order to be usable for making nuclear weapons. At levels of 3 and 5 percent enrichment, it is called low-enriched uranium (LEU), which cannot be used to make a nuclear weapon. It must be further enriched in order to make possible the assembly of the super-critical mass required for an explosion. However, LEU is the most common fuel used for the generation of electricity in nuclear power plants. (Some power plants, notably the heavy-water-moderated reactors of Canadian design, use natural uranium and do not require enrichment facilities.)
Weapon-grade enriched uranium typically contains over 90 percent uranium-235. The amount of weapon-grade uranium required for the manufacture of a bomb is about 15 to 20 kg. But weapons can be made with far lower enrichment levels. At 20% enrichment the material, it would take 250 kg to make an explosive device. (17) This may be considered a kind of practical lower limit to the enrichment required for making weapons. Appendix C provides additional information on the properties of uranium. There are about 2,300 metric tons of HEU in the world; almost all of this inventory is in the former Soviet Union and the United States (see Chapter 7).
The process of enrichment of natural uranium can reversed. To do this, HEU is blended with natural uranium, depleted uranium (which contains 0.2 to 0.3 percent uranium-235), or slightly enriched uranium (0.8 to 2 percent uranium-235), to make LEU for use as power reactor fuel. Leaving aside for the moment the desirability of pursuing such a course, reactor fuel made in this way could, in principle, be competitive with fuel made from uranium ore. Thus, given the existence of reactors that can use LEU fuel as well as of fuel fabrication facilities, HEU is not an economic liability in the same way that plutonium is.
However, we should bear in mind that LEU can be re-enriched to make HEU. The difficulty of detection of re-enrichment partly depends on the type of equipment used for enrichment. Gas centrifuge technology, which is used commercially to make LEU for power reactors in both Europe and Russia, could be used with relative ease to make quantities of HEU sufficient for one or more nuclear weapons. (18) A privately-owned gas centrifuge plant has been proposed to be built in Louisiana, United States. A license application is pending before the Nuclear Regulatory Commission.
The criteria for selecting disposition options for plutonium and for HEU are similar in that they both represent security threats, but they differ in that the economic and environmental issues associated with their disposition are somewhat different. We will consider plutonium is the next part of this report (Chapters 3 through 6), and then briefly consider issues related to HEU (Chapter 7).
3. Some reactors are dual-use reactors, which generate power for civilian use as well as plutonium for military purposes. Many military reactors have special target rods of depleted uranium which are irradiated to yield weapon-grade plutonium.
4. This estimate is based on the following assumptions: (i) there are, on average, under 4 kilograms of plutonium in each warhead and (ii) there are about 20 metric tons of plutonium in the military inventories of other nuclear weapons powers. To maintain an arsenal at a given size, an additional small inventory (relative to the plutonium in the weapons) is required in order to compensate for accidental or remanufacturing losses. David Wright of the Union of Concerned Scientists calculates that this would amount to less than one metric ton for the projected U.S. arsenal (Write as cited in IEER 1994, p.2). This amount is much smaller than the uncertainties in the above calculation and so can be ignored in the present context.
5. David Albright, Frans Berkhout, and William Walker, World Inventory of Plutonium and Highly Enriched Uranium 1992, Oxford University Press, 1993, pp. 204-207.
6. John H. Gibbons, Testimony before the Committee on Energy and Natural Resources, U.S. Senate, May 26, 1994, p.3.
7. NAS 1994
8. Brain G. Chow and Kenneth A. Solomon, Limiting the Spread of Weapon-Usable Fissile Materials, National Defense Research Institute, RAND, Santa Monica, CA, 1993.
9. Frans Berkhout, Anatoli Diakov, Harold Feiveson, Helen Hunt, Marvin Miller, and Frank von Hippel, "Disposition of separated plutonium." Center for Energy and Environmental Studies, PU/CEES Report Number 272, Princeton University, Princeton, NJ, September 1992.
10. Wall Street Journal, October 24, 1994. The price is rising toward $10 per pound, perhaps more. We assume, for the purposes of this report, a yellowcake price of $10 per pound. It is expected to be in the $7 to $15 range over the next few years.
11. Chow and Solomon 1993, pp. 35-39. there are various estimates of reprocessing costs. chow and Solomon state that the $1,600 per kilogram of heavy metal is the mid-point of the range of $1,400 to $1,800 in reprocessing charges actually paid to France and Britain by Japan and other customers, as of the time of the RAND study.
12. Berkhout et al. 1992, pp. 18-20.
13. Paul Leventhal and Steven Dolley, A Japanese Strategic Uranium Reserve: A Safe and Economic Alternative to Plutonium, Nuclear Control Institute, Washington, D.C., January 14, 1994.
14. This discussion addresses only security aspects of "energy independence"; we do not consider other aspects such as environmental problems and risks associated with various energy sources.
15. An exception to this is when HEU is loaded into breeder reactor cores as a substitute for plutonium. HEU is also used as a fuel in some naval propulsion reactors and in some research reactors.
16. While uranium-238 is not fissile and cannot sustain a chain reaction, it can be fissioned with fast neutrons to yield energy. This property of uranium-238 is used in advanced nuclear weapons to provide a significant portion of their yield.
17. Chow and Solomon 1993, p.5.
18. The quantity of HEU required for a nuclear weapon is about 3 to 4 times greater than that for weapon-grade plutonium. About 3 to 5 kilograms of weapon-grade plutonium are required for a fission weapon, though a recent report by the Natural Resources Defense Council states that a kiloton-range weapon can be made with as little as one kilogram. Weapon-grade plutonium contains about 93 percent of the fissile isotope plutonium-239.
Institute for Energy and Environmental Research
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Last Updated April 17, 1996