by: Arjun Makhijani, Ph.D. and Annie Makhijani
January 1995
Second Edition
This study addresses the disposition of plutonium and highly enriched uranium (HEU) as it relates to putting these weapons-usable materials into non-weapons-usable forms in the short- and medium-term. This is a multi-faceted subject; we consider the following aspects of it:
For reasons explained in the introduction to this report, we take as a premise that plutonium is an economic, security, and environmental liability. This is surely not a universally accepted idea. The large financial investments that many countries have made in using plutonium as an energy source have created bureaucratic and institutional resistance to new economic and security realities. This inertia has been largely overcome in the United States due to farsighted policies that were initiated in 1976, at the end of the Ford administration, institutionalized by the Carter administration, and carried forward to the present. U.S. policy has therefore long recognized the fact that all plutonium, whether of civilian or military origin, can be used to make nuclear weapons. The use of reactor grade plutonium in a nuclear weapon was successfully demonstrated in a 1962 test conducted by the United States at the Nevada Test Site, and is a well established fact.
Since the United States has already given up civilian use of plutonium for non-proliferation as well as economic reasons, we believe that it is in an excellent position to exercise global leadership on this crucial issue. Its ability to translate that position into effective action will depend on whether the disposition options that it chooses for its own surplus plutonium take into account the international repercussions of its internal decisions.
As regards highly enriched uranium, most studies assume that it will be mixed with depleted uranium, slightly enriched uranium, or natural uranium in order to convert it into the 3 to 5 percent low enriched uranium (LEU) fuel suitable for use in light water reactors, the most common power reactor design in use today. This report does not examine the economics of this option relative to treating HEU as a waste. Rather, we have pointed out the necessity for examining further options for HEU because, for reasons explained in this report, the option of blending down may not be implemented with the speed necessary to meet growing security concerns.
Like other researchers, we have found that there is no good solution to the disposition of weapons-usable fissile materials; we must select from a menu of poor choices. There are no currently feasible solutions that will get rid of these materials for good. Those that have been proposed as possible options for the future present their own problems of potentially increasing proliferation threats, creating new environmental problems and/or aggravating old ones, and huge costs. Even the exploration of these methods is tied up with unresolved and contentious political questions regarding the future of nuclear arsenals and of nuclear power.
Fissile materials are, in general, necessary for building nuclear explosives. They are defined as materials whose nuclei release energy when split and which can be split with both slow and fast neutrons. Fissile materials in sufficient quantities, called critical masses, can sustain chain reactions and can therefore be used to fuel nuclear reactors. Certain fissile materials, such as natural uranium and low enriched uranium, cannot be used to make nuclear weapons since they cannot be assembled into supercritical masses in which the chain reaction grows so rapidly that there is a large and very sudden energy release -- that is, there is an explosion. Practically speaking, there are only three weapons-usable fissile materials, plutonium, highly enriched uranium (made from natural uranium), and uranium-233, which does not occur in nature, whose man-made stocks are very small relative to plutonium and HEU, and which has not been used in nuclear weapons, so far as public data indicate. We will not consider uranium-233 in this report.
The title of our report draws upon a passage in the Bible that recognizes the uncertainties that are inherent in the human condition whenever we try to peer into the future. Philosophers have generally assigned certitudes to the province of God. The biblical text (from the first Epistle of Paul the Apostle to the Corinthians) reads:
For we know in part, and we prophesy in part.But when that which is perfect is come, then that which is in part shall be done away.
When I was a child, I spake as a child, I understood as a child, I thought as a child: but when I became a man, I put away childish things.
For now we see through a glass, darkly; but then face to face: now I know in part; but then I shall I know even as also I am known.
The creation of vast quantities of fissile materials has accentuated all the incertitudes that we are heir to. The present global predicament with respect to weapons-usable fissile materials, whose half-lives are far greater than the longevity of human institutions, has arisen in large measure because governments and their nuclear establishments did not even consider the question of what future generations might do with these materials, if society did not want them. A failure now to recognize the threat to ourselves and to future generations and to deal with it urgently would compound tragically that historic mistake. We must attempt to minimize the risks for our children, even as we recognize the weaknesses of our solutions.
For the purposes of illustrating some of the calculations in this paper, we have taken a notional amount of plutonium (50 metric tons) to illustrate the time frames that would be involved in plutonium vitrification in the U.S. We have not attempted to deal with the problems of exactly how much plutonium may be declared a surplus, because, as noted above, this will depend on future arms reduction agreements and on the course and quantity of civilian reprocessing. The amount chosen here, 50 metric tons, is almost half of the U.S. military inventory, not including plutonium residues and plutonium in un-reprocessed spent fuel.
The portion of this report related to vitrification of plutonium is based partly on a 1992 draft report which IEER prepared for the Office of Technology Assessment of the U.S. Congress (Contract Number I3-4080.0) as a background paper for use in preparation of OTA's own 1993 report, Dismantling the Bomb and Managing the Materials (see reference list). However, the present report is IEER's alone, and OTA has no responsibility for its publication or its contents.
Annie Makhijani, co-author of this work and Project Scientist at IEER, researched and wrote most of the chapter on HEU disposition. She also researched many aspects of plutonium chemistry relevant to this report.
I would like to thank John Plodinec of the Westinghouse Savannah River Company for information regarding vitrification at the Savannah River Site and Ray Richards of Glasstech for information on stirred glass melters. Professor Marvin Miller of the Massachusetts Institute of Technology kindly provided a copy of a recently completed Master of Science thesis by Kory William Budlong Sylvester that contains analyses of important experimental work on and computer modeling of vitrification. Norton Haberman of the DOE and Norman Brandon of Nuclear Fuel Services provided invaluable information on blending down HEU. Charles Forsberg of Oak Ridge National Laboratory provided much information, including data on a new method of vitrifying plutonium that could be especially applicable to plutonium residues.
The National Academy of Sciences study on plutonium, published in 1994 has been invaluable in preparing this work, as the many footnotes referring to it will attest. In this work we have tried to narrow the options further, and to integrate disposition of military plutonium, civilian plutonium, plutonium residues, and HEU into a single overall policy.
A number of people provided very valuable review comments that have helped make this a better report. They are: Norman Brandon, Brian Costner of Energy Research Foundation, Charles Forsberg, Beverly Gattis of Serious Texans Against Nuclear Dumping, Ralph Hutchison of Oak Ridge Environmental Peace Alliance, Pete Johnson of the Office of Technology Assessment, J.M. McKibben of the Westinghouse Savannah River Company, Marvin Miller, John Plodinec, IEER's Outreach Coordinator Noah Sachs, and Kathleen Tucker of the Health and Energy Institute. Of course, only the authors of this report are responsible for any errors and omissions in it, and for its contents generally.
The first edition of this report was discussed at IEER's National Symposium on fissile materials disposition held on November 17 and 18, 1994 at the Carnegie Endowment for International Peace in Washington, D.C. The basic technical content of this edition, which is being issued as a book, is the same as that of the first edition, but we have drawn on the suggestions made during the symposium to improve the report and include some new material. Further, as a result of the discussion during the symposium of vulnerability of various forms of glass to theft, we have emphasized one option for the vitrification of plutonium as more desirable than others in this edition. We have added a discussion of how the vitrification program might be carried out rapidly and yet with effective public participation. The background material for this new discussion on contracting and public participation (see Chapter 8) was drafted by Brian Costner. Finally, we have made some editorial changes as a result of further review and the discussion of the work during the symposium. Janna Rolland prepared a summary of the symposium proceedings which was very helpful to the production of the second edition. Todd Perry provided an editorial review and many useful comments.
This report is part of IEER's outreach project on plutonium which is supported by grants from the W. Alton Jones Foundation, the John D. and Catherine T. MacArthur Foundation, and the C.S. Fund, as well as a general support grant from the Public Welfare Foundation.
Arjun Makhijani
Takoma Park, Maryland
January 1995
Despite the progress that has occurred between the United States and Russia on many nuclear-weapons-related issues, neither country has a coherent policy for disposition of nuclear materials. Russia is unlikely to act without U.S. leadership and reciprocity, especially given the rising nationalist sentiment that has accompanied economic decline in Russia in the last two to three years. There are already signs that such sentiment may take the form of Russian government policies favoring of preserving large stores of weapon-usable fissile materials and nuclear weapons, rather than reducing them.1 Thus, the U.S. must develop its disposition policy with an eye to its effects in Russia. Given the danger that a global black market in weapons-usable fissile materials originating in Russia may develop, it is imperative that the United States choose a disposition policy and persuade Russia to do the same.
Weapons-usable plutonium also arises from the reprocessing of civilian spent fuel and this must be included in overall disposition policy. The governments of five key countries -- Russia, France, Japan, Britain, and India -- regard plutonium as a valuable long-term energy resource. They continue to operate reprocessing plants to separate plutonium from civilian spent fuel, but their capacity to use plutonium has lagged far behind the rate of its production. As a result, surpluses of civilian plutonium continue to mount, including in Russia. The United States is the only leading country that has wisely rejected the use of civilian plutonium because of its proliferation dangers and its high costs. It is therefore the only country that is in a position to exercise the leadership to persuade other countries to forgo civilian plutonium production at least for the time being, and to put all separate plutonium into non-weapons-usable forms.
Low uranium prices and an abundant resource base mean that plutonium will not be an economically viable nuclear fuel for many decades (if ever) even for those who regard it as a valuable resource for the long-term. This could provide a basis for attempting to achieve an interim, but universal, halt to civilian and military reprocessing. U.S. disposition policy must be compatible with exercising the leadership to get to this goal. An interim halt to reprocessing would allow time for the energy and security issues associated with plutonium to be negotiated without continuing to separate plutonium in the meantime.
Most studies have advocated that the United States consider the option of turning plutonium into highly radioactive spent fuel by "burning" some of it nuclear reactors as plutonium-uranium mixed oxide (MOX) fuel. Despite some advantages of this approach, it would create an infrastructure for long-term use of plutonium as a fuel in civilian power plants. This is highly undesirable from a non-proliferation standpoint, and has no economic advantages whatsoever.
Appropriate institutional arrangements for managing nuclear-weapons-usable materials for the long-term are needed. The DOE has made great progress on openness at the national level; it created a new office for disposition of nuclear materials in January 1994. It has also boldly taken the lead in rejecting the Advanced Liquid Metal Reactor, which would legitimize plutonium-based fuels, for plutonium disposition, despite pork-barrel pressures to continue funding it. Yet, nuclear weapons spending continues to be very high. This is evidence that the hold of the nuclear weapons makers, which produced conflicts on interest regarding health and environmental issues in the past, continues to be strong, despite the end of the Cold War. It remains to be seen whether the gains of the past few years, and notably of the last two on openness at the national level can be generalized throughout the weapons complex and sustained. Accomplishing that consolidation is essential to successful implementation of disposition policy.
Our principal recommendations for plutonium disposition are as follows:
It does not appear at this stage that there are any serious technical hurdles to the implementation of this policy, which is based on combining already commercial technologies. If this policy is carried out from the beginning with due attention to environmental, health, and safety concerns of workers and the communities near proposed facilities, it should be possible to put all separated civilian and all excess military plutonium into non-weapons usable form in a decade or less once the political decision is made to do so.
Other Findings and Recommendations - Plutonium
Other Findings and Recommendations - HEU
"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 plutonium2
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).
No set of policies designed to deal with plutonium disposition will achieve all these objectives to the greatest possible degree simultaneously. For instance, achieving a high degree of difficulty in re-extraction or even transmuting all plutonium into fission products, could be in serious conflict with the objectives of putting plutonium into a form unusable for weapons as rapidly as possible.
Overview of Disposition Options for Plutonium
The 1994 National Academy of Sciences study on plutonium (referred to below simply as the NAS study or the 1994 NAS study) categorized the many options for dealing with plutonium into three groups: 19
Under the last two categories, the NAS considered whether the plutonium would be used in reactors or whether it would be disposed of without such use.
As is evident from the term, "indefinite storage" means that "the plutonium would continue to be stored in weapons-usable form indefinitely." 20 While temporary storage is a practical necessity in all cases until plutonium can be put into a more proliferation-resistant form, indefinite storage does not meet the minimum criteria for achieving security goals of preventing black market sales or reuse in weapons. We will not consider this option any further in this report.
The NAS report discusses a large number of options under the second category of "minimized accessibility." Specific criteria related to "accessibility" are needed in order to enable an evaluation and comparison of these options. Like most studies on this subject, the NAS study adopted the "spent fuel standard" as an approximate measure of how inaccessible the plutonium has been rendered to prevent its future use in weapons.
The "spent fuel standard" does not mean that the problem of plutonium is solved; only that it will be approximately as difficult to re-extract and use plutonium for making weapons as it would be to get it by reprocessing civilian spent fuel.
Such a "standard" suggests itself from a practical reality -- most plutonium today is not in nuclear weapons or stored pits, but is rather in spent fuel from nuclear power plants. Therefore, the problem of plutonium and proliferation is bound up with the existence of this larger stock of plutonium, and it makes little sense to subject plutonium from weapons to a more stringent non-proliferation standard than spent fuel.
The fact that plutonium in spent fuel is mixed with uranium and with fission products, many of which emit intense gamma radiation, has two consequences of importance to disposition. First, as a result of this external gamma radiation, spent fuel is extremely dangerous to handle -- in fact it must be heavily shielded or handled remotely. Any proximity to unshielded spent fuel would result in a lethal dose of radioactivity in minutes (or even less for fresh spent fuel). Second, for the plutonium in spent fuel to be used for nuclear weapons, the spent fuel would have to be reprocessed, a difficult and costly undertaking.
These two characteristics make spent fuel very proliferation-resistant both from the point of view of the potential for theft and the difficulty of re-extraction. However, it does not prevent countries that have spent fuel from deciding to extract the plutonium present in it. For this reason, the NAS also recommended some research on long-term means to get rid of plutonium altogether, using technologies that would fission all of it. However, the spent fuel standard has a serious practical political drawback in that it makes it more difficult to achieve a halt to civilian reprocessing and to put separated civilian plutonium into non-weapons-usable forms. We will discuss this issue further in Chapter 8 on policy.
Most options that would minimize accessibility of plutonium for use in nuclear warheads or radiation dispersal weapons fail on one or more of the criteria listed at the beginning of this chapter. We list them in the Table 2 and indicate the main reasons for doing so.
Table 2
| Disposition option | Principal reasons for rejection |
|---|---|
| New burner reactors - No reprocessing | Long-time frame; licensing uncertainties. |
| New thermal reactors with reprocessing | Encourages reprocessing and hence undermines non-proliferation goals; long time-frame. |
| Advanced Liquid Metal Reactor (ALMR) | ALMR can be used to breed plutonium; most proposals for its use also require a new reprocessing technology (pyroprocessing); long-time frame; undermines non-proliferation goals. |
| Pyroprocessing without ALMR | Promotes development of a new reprocessing technology under the guise of plutonium disposition; undermines non-proliferation goals. |
| Nuclear explosion in an underground cavity | Extensive and unacceptable environmental damage; undermines the non-proliferation goal of stopping nuclear explosions. |
| Sub-critical reactor with proton accelerator | Involves development of a reprocessing technology and hence undermines non-proliferation goals; long-time frame; high technical uncertainty. |
We refer the reader to the NAS study for further discussion of these options. In this report we will consider in more detail three options for minimized accessibility:
For several reasons we have placed the greatest emphasis on vitrification:
We will also discuss long-term plutonium disposition issues, since none of the options for minimizing accessibility actually get rid of all the plutonium.
The difficulties of disposition of surplus plutonium from dismantled nuclear weapons are compounded by continued reprocessing of civilian spent fuel in Russia, France, Japan, Britain, and India. The governments of these countries are wedded to civilian plutonium separation as an important long-term component of energy programs. They are very unlikely in the near-term to give up these programs unless their energy concerns are addressed. Yet, if reprocessing, whether military or civilian, continues, disposition decisions on U.S. surplus military plutonium alone will not fundamentally change the global security picture. The separation and circulation of civilian plutonium will, in the coming decades, far exceed the approximately 250 metric tons of military plutonium in the world. Moreover, reprocessing civilian spent fuel is continuing in Russia; until it is halted, the security concerns in relation to weapons-usable materials associated with the state of the economy and society there cannot be resolved. Therefore, policies directed at achieving a universal but interim halt to reprocessing are essential so that the plutonium problem is not being aggravated while long-term energy and security issues are sorted out.
No country now engaged in civilian plutonium production is likely to stop even on an interim basis without vigorous U.S. leadership. A clear and formal declaration by the U.S. government that plutonium is a security, environmental, and economic liability should be the starting point of such leadership. The text of a letter sent by 43 organizations and individuals to President Clinton on October 19, 1994 requesting such a declaration is attached as Appendix A to this report.
As we discussed in Chapter 3, the U.S., were it on its own, could more freely consider pursuing the MOX option for putting excess military plutonium in proliferation-resistant form. However, the main threat over the next many years does not come from excess U.S. military plutonium, but from the situation in the former Soviet Union. Thus, in our analysis, a MOX option should be ruled out for the U.S. so that it can play the leading role that is needed to stop civilian reprocessing as well as military plutonium production throughout the world.
The only other option that has a chance of accomplishing the immobilization of plutonium into proliferation-resistant form within a reasonable time-frame is vitrification. As discussed in Chapters 4 and 5, there are four broad technical options for plutonium vitrification:
Plutonium processed by the last three options would not meet the spent fuel standard, but, as we have discussed in Chapter 4, the third and fourth options could approximate it on most counts, depending on the material(s) chosen as additives. The last two options may be combined.
It has generally been assumed that the spent fuel standard should be adopted for plutonium disposition probably because it is the most attractive according to certain non-proliferation criteria, in particular, the difficulty of re-extraction of plutonium and the resistance to theft that unshielded spent fuel provides. It is also the strictest practical standard since civilian spent fuel has a large amount of plutonium in it. Processing excess military plutonium to a more stringent standard of re-extraction is therefore seen as a waste of money, given that plutonium could be extracted from civilian spent fuel. It is also generally assumed that mixing plutonium and fission products in the body of the glass is the way that the spent fuel standard should be achieved, if vitrification is the chosen disposition option.
These assumptions need to be refined for a number of reasons. First, gamma-emitting fission products, notably cesium-137, that give spent fuel its proliferation resistance have far shorter-half-lives than plutonium. (The half-life of cesium-137 is about 30 years compared to 24,000 years for plutonium-239.) Therefore, plutonium processed according to the spent fuel standard becomes less resistant to proliferation over time. In the course of a few hundred years, it will come to resemble vitrification of plutonium alone, which is the least strict of the vitrification options we have discussed in this book. Vitrification of plutonium with a non-radioactive chemical analog would provide a somewhat lower but much more durable level of proliferation resistance. The same is true of vitrification with uranium-238 or thorium-232, since both these isotopes have far longer half-lives than the plutonium isotopes in civilian or military plutonium.
Second. vitrifying plutonium mixed with fission products in the U.S. is likely to take long, since existing vitrification plants may be unsuitable for this purpose, as we have already discussed. Therefore, this option is unlikely to be accomplished as rapidly as would be desirable for non-proliferation reasons.
Finally, the spent fuel standard possesses a political defect if it is accomplished by mixing fission products into the glass. It is highly unlikely to be accepted by the countries that have spent and are spending large amounts of money for reprocessing civilian spent fuel. Even if the United States goes ahead and vitrifies its plutonium to this standard by mixing it with fission products, it is unlikely to persuade Russia, France, Japan, Britain, and India to do likewise. A lower level of re-extraction cost may be necessary to persuade these countries to halt reprocessing on an interim basis. Another way of stating this problem is that the spent fuel standard is irrelevant at the governmental level in countries that are now reprocessing. Putting some plutonium into spent fuel or vitrified glass would reduce proliferation threats only for a brief period if plutonium separation continues. The challenge therefore is to find a plutonium disposition option that will provide as high a resistance to theft as spent fuel for sub-national groups, and also pose great challenges for plutonium re-extraction for the same groups. So far as countries that now reprocess or that own separated plutonium, the main tasks are to persuade them to stop reprocessing and to ensure and verify that already separated plutonium is not used to make nuclear weapons.
These goals can be accomplished with the appropriate policies. Even countries such as Russia and Japan that are vigorous proponents of civilian reprocessing recognize four things, even if they do not often do so publicly:
Given this common ground, it may be advantageous to consider plutonium vitrification options where the level of effort of re-extraction is somewhat lower than the spent fuel standard for governments that are reprocessing today, both in terms of the expenditure and time, but still very high for sub-national groups. Evidently, this means that there is a corresponding decrease in the technical barrier to re-use by governments. This problem can be mitigated by safeguards and verification measures, which are in any case necessary for civilian and military separated plutonium. These measures should be buttressed by a multilateral agreement that plutonium, once declared surplus to national security, will never be used in weapons.
The barrier to theft of plutonium and hence to use by sub-national groups can be made high by making the canister containing the vitrified plutonium highly radioactive. In fact the level of resistance to theft provided by such canisters would be comparable to unshielded spent fuel ready for dry storage and far higher than that of spent fuel stored shielded casks such as those that are used for spent fuel transportation. Such casks are now under consideration in the United States for all spent fuel. The technical level of difficulty for re-extraction would be relatively high for sub-national groups, especially since remote handling would be required to remove the plutonium-containing glass from the highly radioactive canister. Beyond this step, vitrification with actinides or rare earths would provide an intermediate level of difficulty of re-extraction.
This complex of measures would allow governments that own plutonium today to recover it in the future, but make it very difficult for sub-national groups to do so even if diversion of the glass logs occurred. Thus, it would be less difficult to persuade governments that still see plutonium as a long-term energy asset that all excess plutonium, including civilian separated plutonium, should be vitrified now to reduce security risks, while keeping open the option of using it in the future should the need arise.
Our reasoning is similar to that which the NAS used in recommending further work on the deep borehole disposition option for excess military plutonium. The deep boreholes in which plutonium would be disposed of would be 2,000 to 4,000 meters deep. Plutonium emplaced at such depths would be far less accessible than that disposed of in geologic repositories, for which typical proposed depths are up to about 1,000 meters. The NAS study recommended further research on this option as a possible alternative to vitrification of plutonium and/or use of MOX fuel, even though it does not meet the spent fuel standard. This is because deep borehole is a disposition option that presents an intermediate level of difficulty of recovery of plutonium for governments but a high-level of difficulty for sub-national groups. According to the NAS, this potential for recovery may be an advantage with respect to governments, like Russia, that believe that plutonium may one day be a valuable and economical energy resource.
The same reasoning leads us to conclude that an intermediate level of difficulty of re-extraction could help put existing separated plutonium in non-weapons-usable form. It could also help convince at least some of the civilian plutonium separating countries to temporarily halt reprocessing until security issues surrounding plutonium can be resolved in a way that greatly reduces the immediate and short-term dangers on as universal a basis as can be achieved.
It may be necessary to offer all countries that own civilian plutonium, but especially Russia and India, a guarantee that grants for plutonium re-extraction would be available should the need arise for using plutonium as an energy source and should it become economical relative to uranium use. Measures to discourage such extraction would also be built into such financial arrangements by holding some of the LEU to be produced by blending down HEU from dismantled weapons as a reserve for use in reactors that would otherwise be fueled with plutonium or with MOX fuel. This LEU reserve could play a global role similar to the domestic role served by the U.S. Strategic Petroleum Reserve. The LEU reserve could be held in part nationally, in part bilaterally (U.S.-Russia), and in part multi-laterally.
We recognize that the proliferation resistance properties of plutonium vitrified with fission products are in some respects stronger than those of plutonium vitrified with actinides or rare earths. We are not advocating that the spent fuel standard be abandoned as an objective. Rather, its refinement so as to accommodate broader goals of putting all weapons-usable plutonium into non-weapons-usable forms is needed. To this end, we strongly urge that vitrification of plutonium with rare earths and actinides should be investigated and the pilot plants should be built.
Reducing the difficulty of re-extraction need not mean lowering the barriers to theft. The difficulty of theft depends on a number of factors, of which a high external gamma radiation field is one of the most important. There are a number of ways in which high external gamma radiation fields can be created to deter theft without mixing plutonium with fission products. One way would be to put plutonium vitrified with rare earths into cesium-137-laced radioactive containers that are manufactured separately. Alternatively, a small container with cesium-137 or a mix of calcined fission products in it could be placed in the canister at a time after plutonium-laden glass has been poured into it. There are some advantages to the former approach. First, the work with gamma emitting fission products can be done entirely separately from the vitrification plant. Second, the canister containing vitrified plutonium can be sealed shortly after the glass is poured. Third, the difficulty of re-extraction may be lower once the glass is removed from the canister. Therefore, this would be more attractive to plutonium-owning countries that regard plutonium as an energy asset, but resistance to theft would still be as high as with the spent fuel standard.
Combining the canister rather than the glass with one or more fission products means that hot-cell processing of gamma-emitting radioactive materials can be done more slowly or even separately from plutonium vitrification. Thereby achieving the spent fuel standard is made compatible with putting plutonium into a non-weapons-usable form as rapidly as possible. Further, the amount of fission products to achieve a specified gamma radiation field will be far lower, as we have discussed in chapter 4.
Vitrifying plutonium with a rare earth or actinide and putting gamma-emitting radioactive materials in the canister appears to be the option that best combines various disposition goals. We recommend that DOE commission a feasibility study and appropriate laboratory work on this option in parallel with the pilot plants mentioned above.
Highly Enriched Uranium Disposition Policy
There are about 2,300 metric tons of HEU in the world today, almost all of it in the United States and the former Soviet Union. As we have discussed, about 1,000 metric tons or more of this could become an official surplus as existing arms reduction agreements are implemented over the next decade. It would appear at first that the blending down of HEU to LEU for use in civilian reactors would be the most straightforward way to reduce the attendant security risks. However, as we have noted, the capacity for this blending down does not yet exist in the United States.
The U.S.-Russian agreement, signed in early 1993, will be implemented very slowly, even after blending down actually begins. In each of the first five years, only 10 metric tons of HEU of 90 percent enrichment or greater are required to be blended down, with the rate going up to 30 metric tons per year in the fifteen years after that. At these rates, only 200 metric tons of HEU would have been blended down a decade after the implementation begins. The entire amount will have been blended down in 20 years.
The security threats arising from potential black market sales of HEU may be greater than those arising from plutonium because HEU can be fashioned into weapons of both implosion and "gun-type" designs, while plutonium warheads must be made with an implosion design. Therefore, bilateral or multilateral control, verification of stocks, and adequate materials accounting are all needed.
The large delays in converting HEU into LEU could be mitigated by two policy responses, in addition to the storage and verification arrangements that are needed in any case. The first would be to build new capacity for blending down HEU as rapidly as compatible with environmental and health considerations. The second would be to vitrify a portion of the HEU. The objective of vitrification would be to quickly raise a barrier to proliferation while leaving open the possibility of recovering the HEU and blending it down into LEU for use as fuel. It may be possible to accomplish vitrification on a faster time-scale than blending down might allow. However, vitrification could make LEU derived from HEU uneconomical relative to LEU from newly mined uranium. This is an issue that needs to be addressed prior to a decision on a policy for vitrifying HEU.
Finally, it is relevant to note in this context that HEU does not entirely cease to be a security problem once it has been blended down into LEU. This conversion only raises a barrier to proliferation. Specifically, LEU can be re-enriched to HEU and used for nuclear weapons. If the enrichment process involves the use of gas centrifuge plants, which are in commercial use both in western Europe and in Russia. The detection of re-enrichment at these and any similar plants built in the future will be difficult without extensive new safeguards. It is therefore essential that verification of LEU stocks and more importantly of enrichment facilities not now under IAEA safeguards be established so as to make its re-enrichment very difficult. This adds to the need to examine vitrification of HEU as at least a partial disposition option.
In sum, while there is a theoretical solution to the problem of surplus HEU in blending it down to LEU, the practical situation is such that the security threat from HEU will persist, even if we restrict attention to the partial stocks that may be declared surplus over the next decade. Of course, the actual magnitude of the threat is larger, and covers the whole amount (as it does with plutonium).
The question of what should be done with the LEU blended down from HEU is also not as straightforward as might first appear. First, there are commercial pressures to keep the LEU in reserve so as to protect the financial interests of existing commercial producers of uranium as well providers of enrichment services.
Commercial considerations should not be a prime component of the decision to withhold the LEU from the market. However, they could be partly compatible with security criteria. As we have discussed, a portion the LEU produced from HEU could be used to build up a stock of nuclear power plant fuel as part of a guarantee to those countries that stop reprocessing spent fuel that they will not lack for fuel, should uranium prices escalate in a manner that is not now anticipated. The strategic stock of LEU could also be used as a modest lever to hold uranium prices to levels that would discourage commercial reprocessing. The first batches of LEU produced by blending down HEU could be devoted to creating such a strategic LEU stock. Any vitrified HEU would also, in effect, serve as a strategic stock. The issue of the size of the stock of LEU required for an effective strategic reserve needs to be studied.
Institutional Issues
It is now at least routinely acknowledged that operations in the nuclear weapons complex must be carried out in conformity with environmental , safety, and health laws and regulations, and with the full participation of the affected communities and other "stakeholders" such as workers. There have also been real and positive changes on a number of other fronts in the Department of Energy, notably at the national level. There are increased opportunities for public participation. Site Specific Advisory Boards are being created or have been created at most nuclear weapons plant sites. Secretary of Energy Hazel O'Leary has released large amounts of data and documents in an unprecedented openness initiative, despite some opposition from the Pentagon. The DOE has also taken the lead in ending funding of the ALMR, a reactor that could produce plutonium, and hence pose a problem from a proliferation standpoint.
This real progress has not yet gone far enough however. Field and contractor operations and decision-making are not carried out with the openness that is needed; nor is there a sufficient, routine concern for the protection of health and the environment. Spending on weapons continues to be very high, though no weapons are being made. Nuclear weapons testing is re-appearing in new, small-scale disguises. Old technologies that were designated for nuclear weapons production or nuclear power development suddenly appear as clean-up or disposition technologies or both. Most recently, pyroprocessing technology, detached from the now defunct Advanced Liquid Metal Reactor, has made an appearance on the plutonium disposition scene in a forceful manner. The DOE has recently "reprogrammed" money to increase funding of pyroprocessing. While this is ostensibly for examining this technology for plutonium disposition, it also sustains the crucial research aspects of pyroprocessing as a reprocessing complement to the ALMR, which is an advanced plutonium breeder reactor. This is counterproductive for non-proliferation goals. In short, the hold of nuclear weapons makers and contractors on government policy is still strong.
We have already noted an example of the violation of storage regulations for HEU at Oak Ridge. Incineration is still the basic method of handling mixed radioactive and non-radioactive hazardous wastes. The classification of radioactive waste is still based on a scheme that is not systematically related to the longevity and hazard of the waste. The DOE has yet to submit itself to independent regulation, despite some progress towards creating a framework to achieve this goal. The durability of the progress that has been made is also an open question. In sum, it is not clear that the DOE (the agency whose main mission it was to build bombs), is well-suited to dismantle them and manage the materials. That was the central thrust of the analysis of institutional problems made by the OTA in its 1993 report, which concluded that "U.S. dismantlement and materials management efforts have lacked focus, direction, and coordination." The OTA also concluded that a new office within the DOE or an entirely new agency of government might be needed to manage the problems of the post-Cold War era arising from nuclear weapons dismantlement and materials management.
A new Office of Fissile Materials Disposition was created in January 1994. It is dedicated to disposition issues; it is too early to tell whether this office will be able inspire the kind of work that its mission requires. Further, there is no agreement between the DOE and the Pentagon on crucial disposition issues, such as whether and how much plutonium should be declared a liability, and on how open the government should be with the people of the United States.
It is clear that the vital need to put weapons-usable nuclear materials into non-weapons-usable forms cannot be successfully met, much less with the speed that is desirable from a security standpoint, until these basic institutional issues are resolved. Continued pressure from the affected communities will be central to their resolution.
Public Participation
Successful implementation of plutonium and HEU disposition policy will need the full involvement of the affected communities, especially since speed of implementation is a basic security need. The poor record on health and environmental protection of the DOE and its predecessor agencies has engendered a profound public distrust that has only begun to be remedied by the openness initiatives of recent years. It is more than likely that any closed process will lead to delays and perhaps also to inappropriate choices of technology. The discussion below is specific to the process for building pilot plants for plutonium vitrification, but the spirit of the comments regarding openness and public participation applies equally well to HEU disposition.
A principal recommendation of this book is that three or four pilot plants for plutonium vitrification should be built. One reason for the emphasis on pilot plants is that the DOE needs to gain operational experience with the technology in order to prepare a sound environmental impact statement on vitrification that would result in the selection of the best way(s) to vitrify various forms of plutonium and the best way to achieve non-proliferation goals in a manner compatible with health and environmental protection.
The pilot plants for vitrifying plutonium should be small enough that they will allow operational experience to be accumulated without risk of severe accidents but large enough that full-scale plants could be built and operated with confidence based on that experience. In our view, plants meeting these criteria would be large enough that a very open process for setting them up is necessary. On the other hand, it should be possible to design them so that they are small enough to obviate the need for formal environmental impact statements or environmental assessments under the National Environmental Policy Act.
The DOE needs to open up the process for selecting vendors for vitrification technologies so as to include its own laboratories, U.S. corporations that have not been traditional DOE vendors, as well as foreign corporations that have relevant expertise and experience. Further, as we have noted, the DOE should seek to involve Russian institutions at the pilot plant stage so that full-scale plants can be rapidly built in Russia once there is agreement on a disposition method for Russian plutonium. Moreover, the Russian nuclear establishment has considerable operational experience with vitrification and this may help in designing and building the pilot plants.
A closed process of vendor selection would be highly undesirable. The DOE's record in successfully opening major new facilities has been very poor since its creation as a cabinet-level department in 1977. An open process for setting goals for the project, the criteria for vendor selection, and the selection of the vendors is necessary for the critical work of developing plutonium vitrification technology and implementing it in a manner than joins deliberate speed with measures for achieving the protection of health and the environment.
One approach to building plutonium vitrification pilot plants would be for the DOE to hold a competition seeking bids for designing, building, and operating them. The DOE would specify the goals of the project -- namely to test and assess for the environmental, safety, health, and economic standpoints of various ways to vitrify plutonium -- and the criteria by which these goals would be evaluated. Bids that include qualified Russian collaborators would be encouraged. The proposals would be required to include an environmental and health analysis of the impact of the pilot plants, the employment levels expected, the skills needed, and a summary of the bidders' health and environmental track record. All bids would be made public after the closing date and open discussions would be held at the proposed pilot plant sites on their relative merits. This would aid in the selection of the best proposals. Further, by involving the affected communities, the DOE can ensure their support for the full-scale plutonium vitrification when it is carried out. We suggest that the competition be started in early 1995 and that the selection process of the pilot plant vendors be completed by the end of 1995 or early 1996.
Long-term Policy Issues
Whether plutonium is vitrified or burned in reactors without reprocessing, a large amount of it will remain for tens of thousands of years. Further, there are large amounts of plutonium in civilian spent fuel as well as in separated plutonium from such spent fuel. These sources of plutonium will constitute a threat to the security of future generations that will endure for thousands of years. As we have discussed, the threat from spent fuel will increase, since the decay of intense gamma emitting isotopes, especially cesium-137, in a few hundred years will make it easier to recover plutonium from spent fuel or glass logs containing high-level waste.
It has generally been assumed that this threat will be greatly reduced by disposing of spent fuel and vitrified waste in a geologic repository. This would increase the costs of plutonium recovery so greatly that it would be more costly to recover spent fuel or vitrified waste from a repository and reprocess it than to derive plutonium from new reactors and reprocessing plants. That should, in fact, be one of the design objectives of a repository. 122
This theoretical scheme is flawed by one crucial reality. No country has as yet been able to successfully site a geologic repository, though several have been pursuing such a course for decades. There are many reasons for the delays and failures.123 One principal issue has been that the search for a repository has been bound up in a conflict of interest. The very institutions that have a financial and military interests in nuclear power and nuclear weapons (which together generate most of these wastes) are responsible for or intimately involved in repository selection. Further, we have no institutional experience and not enough scientific knowledge (by a long shot) to predict with confidence the environmental threats that such disposal will pose over hundreds of millennia. The public is rightly skeptical.
If separated plutonium is managed in the interim according to the spent fuel standard, the long-term issues for its disposal are essentially the same as those that arise for unreprocessed spent fuel from civilian power plants. We have already briefly discussed issues of plutonium disposition as they relate to possible repository disposal in the U.S. in Chapter 6.
Essentially complete elimination of plutonium can only be accomplished by two methods. One is to simply wait until the natural radioactive decay of its nuclei have converted it to uranium-235. Since the half-life of plutonium is over 24,000 years, this period of waiting is far longer than the longevity of any human institutions. The other approach is to transmute plutonium using some technique to bombard its nuclei and split them into fission products. Most of these fission products are radioactive; most have half-lives of a few decades or less, but some like technetium-99 and cesium-135 have half-lives that are very long.
So far, the approaches that have been considered for complete transmutation of plutonium in major recent studies have considered only reactor options with some associated reprocessing technology. The two most commonly considered technologies in this category are the Advanced Liquid Metal Reactor (ALMR), which can also be used to breed plutonium, and a proton accelerator combined with a sub-critical reactor and reprocessing, proposed by Los Alamos National Laboratory. Both these technologies must be rejected on proliferation grounds. The U.S. Congress, at DOE's request, has eliminated funding for the ALMR for 1995, though not for the reprocessing technology, called pyroprocessing, associated with it.
One approach that can be used for separated plutonium that does not involve the use of nuclear reactors or reprocessing, but may still result in the elimination of plutonium, is fission using gamma rays. Its feasibility for plutonium disposition has not yet been examined, so far as we have been able to determine. The method involves the fission of plutonium nuclei by the use of high energy gamma rays, which consist of high-energy electromagnetic radiation. The process is called "photofission" because the fission is induced by photons, which are quanta of electromagnetic energy. Other heavy nuclei can also be split by photofission.
A specific spectrum of gamma rays with photons in the energy range of 10 to 15 MeV has a particularly high chance of producing fission in heavy nuclei. This spectrum is called the "giant resonance region" for inducing photofission. Photons of these energies can be produced using an electron accelerator, which is a very well understood technology. The radiation from the stopping (or braking) of high energy electrons (called "bremstrahlung radiation") can be tailored to produce photons in approximately the required spectrum. The photons would induce fission in a plutonium target.
The heat from the braking of the electrons as well as from photofission would have to be carried away by a coolant. This creates the possibility that some of it could be recovered in order to generate electricity. Whether such heat recovery for electricity production is desirable is one of the many questions to be addressed by a feasibility study examining photofission as a long-term disposition option for already separated plutonium.
While the physics of such a scheme is understood, it would be an immensely difficult and complex engineering challenge. During the 1970s, the method was briefly considered for dealing with spent fuel. However, it was rejected because the energy needed to induce photofission to get rid of the long-lived heavy elements would be greater than the energy produced from the fuel in the nuclear reactor.124 Further, photofission would require that the elements to be fissioned be separated from spent fuel, that is, it would require reprocessing. Thus, the approach also is unacceptable for dealing with spent fuel on proliferation grounds.
However, if plutonium is not mixed with fission products, then it can, in principle, be made into targets that are suitable for photofission. The energy use as well as the capital and operating costs of fissioning plutonium completely in this way are likely to be very high. Since the plutonium would be fissioned, the problems of disposing of highly radioactive fission products would also exist with photofission as with all others that depend on fission for plutonium transmutation. The interaction of the photons with a mixture of fission products also needs to be investigated. Further, fission produces neutrons; these neutrons would produce activation products, rendering radioactive a portion of the structure of the devices needed for transmutation. Thus, photofission does not represent a solution to the plutonium disposition problem in the sense of promising something satisfactory without serious long-term financial and environmental costs.
Photofission, if feasible, may offer the potential for complete transmutation of already separated plutonium. But there are many technical unknowns. For instance, its technical feasibility without resorting to some form of reprocessing technology will likely depend on whether appropriate targets can be fabricated that would hold up to the intense radiation and heat until essentially all the plutonium has been fissioned. It is unclear at present whether this can be done in practice.
The only other approach that could get rid of separated plutonium without reprocessing is to shoot it into the sun. While at present both costs and dangers of this approach are immense, we believe this also deserves a more careful feasibility study.
Neither space disposal nor photofission can deal with the problem of plutonium in spent fuel, unless it is first reprocessed. Therefore, when examined from the perspective of the overall problem of plutonium elimination, they do not represent solutions. Whether such technologies would be worthwhile at all just for disposing of already separated plutonium is an open question. We believe that both approaches deserve serious feasibility studies so that we may have a basis to decide whether some research and development of one or both of them would be worthwhile.
The future of security and environmental issues arising from the creation of plutonium is bound up with nuclear power production, since essentially all nuclear power plants produce large quantities of plutonium as a normal part of their operation. The only exceptions to this are reactors that use HEU as fuel, but this fuel is itself a proliferation problem. Therefore, if we are to make an attempt to definitively deal with the threats arising from the existence of weapons-usable fissile materials, we must confront the central issue of what energy sources the world will rely on for the long-term. Our final recommendation is therefore that the use of nuclear power should be more carefully evaluated in light of the long-term proliferation problems posed by the very existence of large and increasing quantities of plutonium in spent fuel.
Institute for Energy and Environmental Research
Comments to Outreach Coordinator: ieer@ieer.org
Takoma Park, Maryland, USA
Last Updated April 17, 1996