An Evaluation of the Electrometallurgical Approach for Treatment of Excess Weapons Plutonium (1996)

What should be done with plutonium, including how it can best be extracted, captured, and disposed of, is an issue of great importance, given that “[v]irtually any combination of plutonium isotopes … can be used to make a nuclear weapon.”¹ Currently, large quantities of plutonium are being stockpiled as a result of the dismantling of nuclear weapons in Russia and the United States, following the plans developed in the Strategic Arms Reduction Treaty negotiations. Although not as desirable but still quite usable for weapons, even larger quantities of plutonium exist in spent fuel stored worldwide. Finally, many tons of plutonium are contained in residues, wastes, and weapons production equipment, certainly in the United States and probably in Russia.

Not all of this plutonium is equally accessible and usable for weapons. Other recommendations for long-term plutonium disposition have specified that disposal processes should produce a form from which the plutonium would be at least as difficult to extract and use for weapons as is the plutonium contained in commercial spent fuel. This is the so-called “spent fuel standard.”² This committee believes that plutonium recovered in the electrometallurgical process would be required to meet this standard, a goal that could be achieved by allowing radioactive impurities to be discharged with the plutonium in the process itself. Alternatively, such radioactive impurities could be added to a relatively purer plutonium effluent stream.

Developing technology that effectively extracts the plutonium from mixtures could facilitate decommissioning of former weapons manufacturing facilities and mitigate some of the problems found at these facilities, such as corroding fuel. However, such efficient technology also raises concerns about proliferation; what the United States might use to assist in the cleanup of a contaminated facility such as Rocky Flats could be used by another country to obtain plutonium for a weapons program.

Another concern is the cost of an unproven technology. Given an approved end point, several approaches might be taken to meet it satisfactorily. For example, plutonium could be extracted from corroding fuel rods as a step toward disposal of the vitrified high-level waste. Alternatively, the fuel rods could be encased in a new metal container, with subsequent vitrification of the package. If both technologies were able to eliminate the problem of corroding fuel rods, the more costly would be justified only if the process had other, important advantages. For extraction of plutonium, there does not appear to be such a justification, since, once extracted, the plutonium must be disposed of extremely carefully.

Given the great concern about the fate of weapons plutonium, the CISAC reports³,⁴ recommended against approaches that would require significantly more time to develop, or would entail significantly greater uncertainty, than alternatives that could be available in a shorter time and with less uncertainty. That conclusion was based on an earlier version of the electrometallurgical approach.⁵ Although this committee

has not examined costs, the committee believes that the uncertainty and timeliness for the present proposed electrometallurgical technique would not alter the conclusion of the earlier report.

The ANL program for development of the electrometallurgical technique constitutes a demonstration of this technology for the treatment of certain DOE spent fuels. DOE has determined that the first such fuels to be processed are the elements withdrawn from the EBR-II reactor, which total about 48.4 metric tons of heavy metal (MTHM). Successful demonstration of this technology on a suitable scale on actual spent fuel is considered essential to proving its practicability. ⁶ Additionally, the demonstration will provide necessary data on remote operations and maintenance in an inert atmosphere and on the effects of high levels of radioactivity. If the electrometallurgical technique is to be considered for disposal of excess plutonium, the feasibility of this technique must be validated. The current ANL program for treatment of EBR-II fuel appears to be the most cost-effective and timely way to make that demonstration for several but not all elements of the electrometallurgical technique. One of the important factors in the ANL program is the timeliness of the demonstration to allow decisions to be made about the possible application of this technique to the treatment of other DOE spent fuels. In its previous report, ⁷ this committee endorsed certain schedule milestones and emphasized to DOE the importance of its maintaining an already tight schedule.

Were the electrometallurgical technique to be demonstrated successfully for treatment of DOE spent fuel and the issues relating to the waste forms resolved, the electrometallurgical technique could provide a potential method for handling excess plutonium at some later time. However, the committee recently has been made aware that some of the major milestones identified in its 1995 report have not been met: “[S]pent fuel treatment or processing activities using irradiated spent fuel are not authorized at this time pending completion of a further National Environmental Policy Act (NEPA) process.”8 In the absence of this necessary demonstration, the basis for evaluating the electrometallurgical approach as an option for plutonium disposition is unlikely to be available.