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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.
20. NAS 1994, p. 144.
21. Office of Technology Assessment, Staff paper on the Sub-seabed disposal of high-level waste, U.S. Government Printing Office, Washington, D.C., 1986; Chow and Solomon 1993; NAS 1994; Berkhout et al, 1992.
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Last Updated April 17, 1996