An Assessment of Continued R & D into an Electrometallurgical Approach for Treating DOE Spent Nuclear Fuel (1995)

A Preliminary Assessment of the Promise of Continued R&D into an Electrometallurgical Approach for Treating DOE Spent Fuel *

In September 1994, the Department of Energy (DOE) requested that the National Research Council undertake an evaluation of the Argonne National Laboratory's (ANL's) proposed electrometallurgical processing techniques as a potential approach for treating DOE spent nuclear fuel. A succinct description of DOE's spent fuel holdings and ANL's rationale for proposing an electrometallurgical approach may be found on page 1 of the ANL proposal, which is included as Appendix 1.

The DOE's request led to the formation of the Committee on Electrometallurgical Techniques for DOE Spent Fuel Treatment, which was charged with carrying out a fast-track study of electrometallurgical techniques as potential technologies for the treatment of DOE spent fuel. Specifically, the charge consists of two tasks:

1. Hold a first meeting to receive briefings from representatives of the DOE and ANL, additional experts identified by the committee, and representatives of other relevant activities of the National Research Council and National Academy of Sciences, and then prepare an interim report to address the question, “Do electrometallurgical techniques represent a potentially viable technology for DOE spent fuel treatment that warrants further research and development?”

2. Study in more depth the advantages and disadvantages of continued research and development of electrometallurgical processing as a candidate technology for disposition of DOE spent fuel, specifically addressing the issues of technical feasibility, cost-effectiveness, suitability of the metallic waste form for long-term storage or geologic disposal, and nonproliferation implications, and write a report on the committee's assessments.

This interim report responds to the first task.

For the purposes of this interim report, the committee interpreted the phrase “potentially viable technology” in its limited sense, to refer to technology for which the basic science is reasonably understood, the laboratory work to date is generally promising, and the anticipated problems of scale-up and eventual maintenance do not appear to be technically insurmountable. For this interim report, the committee was charged with assessing the technical merit of the proposed R&D in the near term. This report does not

address the issue of adoption of this technology as a component of the national strategy for handling nuclear materials.

The committee met on January 9-11, 1995, at the National Research Council's facilities in Washington, D.C., to carry out its preliminary assessment of the ANL's R&D plan as described in Appendix 1. During this meeting the committee was briefed by DOE representatives and was provided with relevant technical information in the form of presentations from and discussions with technical experts, including representatives from the Argonne National Laboratory as well as scientists from Westinghouse Hanford Co., Westinghouse Savannah River Co., and Sandia National Laboratories. In addition, the committee received input from representatives of several interested public citizens groups on the subject. The agenda and list of attendees for the January 9-11 meeting are presented in Appendix 2 [not included as such in this reprinting but incorporated into Appendix B following].

Based on the technical presentations to the committee, discussions with the presenters, written materials reviewed by the committee, ¹ and the experience base of the committee members, the committee did not identify any “showstoppers” in the technical proposal that would suggest discontinuing the planned R&D. The committee concluded that electrometallurgical techniques represent a sufficiently promising technology for treating a variety of DOE spent fuels to warrant continued R&D in federal FY96. The committee did not evaluate the associated level of funding, which the DOE has estimated to be $12 million.² During the next 12 months the DOE should closely follow the progress of the proposed R&D program to determine whether it should be continued beyond FY96. Critical input from experts outside the program would be beneficial to the DOE in making that decision. An essential factor in this determination should be the progress and status of the upcoming demonstration of the process as applied to irradiated EBR-II fuel.

The committee's conclusion in favor of continued R&D through FY96, which should be interpreted as neither an endorsement nor a rejection of the overall ANL proposal in Appendix 1, is based on the following rationale.

First, the electrometallurgical technique is not a new technology. Progress made to this point in Argonne's &program indicates that the ANL group has understood and addressed a number of challenges in developing the electrometallurgical process.³ ANL personnel have already demonstrated, on an engineering scale, electrometallurgical separations with simulated metal fuel. They have also demonstrated, on a laboratory scale, the lithium reduction of simulated mixed oxide (MOX) fuel, which is suggestive of the applicability of that technique to treating DOE's nonmetallic spent fuels.

Second, the electrometallurgical technology has been developed sufficiently to be proposed for treating EBR-II spent fuels, and the DOE apparently has sufficient confidence in the process to have approved

this application. The electrometallurgical techniques need to be tested with actual spent fuel, which could provide data on issues of scale-up, remote operation and maintenance in an inert atmosphere, and effects of high radioactivity. The scheduled demonstration of EBR-II spent fuel treatment will enable a practical near-term evaluation of important components of ANL's proposed electrometallurgical treatment technology. The committee emphasizes that the DOE should follow this demonstration project closely, in order to evaluate the efficacy of the technology.

The committee's recommendation for continuation of the &through FY96 does not imply an endorsement of the incentives for electrometallurgical treatment of DOE spent fuel that are noted on p. 1-3 (Appendix 1). The rationale for carrying the proposed &through its current phase of development is independent of this particular collection of incentives, which pertain to a future policy choice among options for the treatment of DOE spent fuel. Continuation of the proposed &would not imply a commitment to any particular disposal option for any of the product streams, or to the other incentives mentioned.

The committee concluded that continued electrometallurgical technology &would not constitute an endorsement of the Integral Fast Reactor (IFR) program that has been terminated by the DOE. The committee recommends that such &should be conducted solely for the evaluation of this technology's effectiveness for treating DOE spent fuel, and that decisions about funding of electrometallurgical &for DOE spent fuel treatment should be independent of issues related to the IFR program.

The committee is aware of other spent fuel treatment technologies that also might have application for treatment of a variety of DOE spent fuels. However, the committee has not attempted to make a comparative evaluation of the electrometallurgical approach against other potentially applicable technologies. The committee did seek to determine where the electrometallurgical treatment technology would fit into the overall DOE scheme for disposal of its spent fuel. While no such overall scheme or “road map” was available to the committee, DOE representatives advised that a generic environmental impact statement was in preparation that would seek to address the anticipated options for DOE spent fuel disposition. The committee believes that prior to making a final decision about widespread implementation of the ANL electrometallurgical technology for treating DOE spent fuel, it is essential that the DOE determine how the electrometallurgical technology, and other treatment technologies, fit into its overall strategy for spent fuel disposal and the closely related strategy for the management of high-level and transuranic wastes.

Special Advisory Committee for the Integral Fast Reactor, 1994, “Pyrochemical Processing— Accomplishments and Applications,” letter report dated Dec. 20, 1994, from committee chair Max W. Carbon to Arthur M. Sussman, University of Chicago.

PROPOSAL FOR DEVELOPMENT OF ELECTROMETALLURGICAL TECHNOLOGY FOR TREATMENT OF DOE SPENT NUCLEAR FUEL

Argonne National Laboratory

January 1995

(DRAFT)

A total of approximately 2,700 metric tons of spent nuclear fuel has accumulated within the U.S. Department of Energy (DOE) complex. This government-owned fuel was used in a variety of nuclear reactors, including reactors for the production of national defense materials, experimental and research reactors, and commercial reactors. Although the quantity of spent fuel in the DOE inventory is much less than that in storage at U.S. commercial reactors (estimated to reach 40,000 tons by the end of the century), the DOE spent fuel presents special problems that demand prompt attention. The DOE spent nuclear fuel inventory differs in several ways from the commercial spent fuel inventory, in that the DOE spent fuel represents the arisings from over 40 years of the evolution of nuclear power and reflects a broad spectrum of fuel types, cladding materials, levels of enrichment in the fissile isotopes of the actinide elements, and degrees of chemical reactivity.

Over 150 different fuel designs are represented in the DOE inventory; these can be grouped into 53 different categories according to common design features such as composition, cladding material and enrichment level. There are six major categories of fuel composition (metal, oxide, graphite, cermet, hydride, and aluminum alloy) alone. Included in the DOE spent nuclear fuel inventory are fuels that (1) have seriously degraded during storage, (2) are highly enriched in fissile isotopes, (3) are chemically reactive or contain reactive materials, and (4) cannot be expected to retain their integrity or remain stable over an extended period of wet or dry storage.

The electrometallurgical treatment technique, developed by the Argonne National Laboratory, appears to have great potential for application in the treatment of the collection of DOE spent nuclear fuel types for ultimate disposal. This process is applicable in its current stage of development to over 90% of the DOE spent fuel inventory and offers the advantages of a simple, compact system that is both economical and technically sound.

Electrometallurgical treatment refers to the complete set of unit operations required to separate the actinide elements from fission products present in spent fuel and to place the waste products in stable forms suitable for disposal. In the case of most spent fuel types, these operations begin with the dismantling of the irradiated fuel assembly and the removal of individual fuel elements. These fuel elements are sent to a chopper, where they are chopped into pieces suitable for the next operation. If the fuel is metallic, regardless of the cladding type or any internal components such as hardware or heat transfer media, it is sent directly to the electrorefiner for electrotransport of the actinides to appropriate electrodes where they are collected for further processing. If the fuel is oxide, it is first sent to a reduction step where the oxide compounds of actinides and fission products are reduced to the metallic state by reduction with metallic lithium. The reduced metal product is then transferred to the electrorefiner for separation into the various product streams. If the fuel is of a type other than metal or oxide, it must first