CISAC Findings

The general issue of the disposition of excess weapons plutonium has been thoroughly addressed by the National Academy of Sciences (NAS) Committee on International Security and Arms Control (CISAC) 3 and by its associated Panel on Reactor-Related Options for the Disposition of Excess Weapons Plutonium (the “Reactor Panel”).4 The disposition options explored by CISAC were “minimized accessibility” (i.e., the creation of physical, chemical, radiological, and isotopic barriers to reduce the material's accessibility for use in a weapon) and “elimination” (i.e., the removal of the material completely from human access, for example, by allowing the material to fission in a reactor until less than a critical mass remained). To compare options, CISAC introduced the concept of the “spent fuel standard.” This concept was not intended “to imply a specific combination of radiation barrier, isotopic mixture, and degree of dilution of plutonium” but rather to denote a “condition in which the WPu has become roughly as difficult to acquire, process, and use in nuclear weapons as it would to be to use plutonium in commercial spent fuel for this purpose. ”5 Since the ratio held in civilian relative to military stockpiles is believed to be about 3:1, the Reactor Panel concluded that “there would be very little security gain from special efforts to completely eliminate the WPu, or render it much less accessible even than the plutonium in spent fuel, unless society were prepared to take the same approach with the global stock of civilian plutonium.”

The Panel on Reactor-Related Options examined pyroprocessing as an alternative approach for plutonium disposition. At the time the evaluation was made, the panel cited several disadvantages that it felt effectively excluded the electrometallurgical technique as a viable option in the near term. The panel concluded that the “pyroprocessing approach is not competitive with either vitrification in borosilicate glass or the use of mixed uranium-plutonium oxide (MOX) in existing reactors, both of which would be likely to involve lower costs, lower technical uncertainties, and shorter delay.”6

In the period since CISAC and its Reactor Panel evaluated the pyroprocessing approach, ANL has modified its process (see Chapter 2, Figure 2) to capture the plutonium and other transuranic elements in a zeolite matrix along with most of the fission products. This approach contrasts with the originally proposed scheme that was considered by CISAC and its Reactor Panel, in which the plutonium, other transuranics, rare-earth fission products, and some uranium were to be reduced to metals at a molten cadmium cathode and finally cast as metal ingots. 7 In each of these schemes, the waste form would include both the plutonium and radioactive fission products, thereby providing the rationale for plutonium disposition in accord with the “spent fuel standard.” ANL has proposed using the electrometallurgical technique for disposition not only of weapons “pits” (the plutonium components of nuclear weapons, named by analogy with the pit of a fruit such as a peach), but also for the non-pit materials that include plutonium in any other shape or chemical form.

3  

Management and Disposition of Excess Weapons Plutonium, National Academy of Sciences Committee on International Security and Arms Control (CISAC), National Academy Press, Washington, D.C., 1994.

4  

Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options, Panel on Reactor-Related Options for the Disposition of Excess Weapons Plutonium, Committee on International Security and Arms Control (CISAC), National Academy Press, Washington, D.C., 1995.

5  

See the report cited in footnote 4, p. 73.

6  

See the report cited in footnote 4, p. 221.

7  

As noted in the report cited in footnote 4, p. 220 (footnote 3), the CISAC Reactor Panel analysis utilized the same IFR flow sheets that were considered in another NRC study (Nuclear Wastes: Technologies for Separation and Transmutations, National Research Council, National Academy Press, Washington, D.C., 1995).



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