Improving the Scientific Basis for Managing DOE's Excess Nuclear Materials and Spent Nuclear Fuel (2003) / Chapter Skim
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Executive Summary
Executive Summary
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About 50 metric tons of this isotope, a principal component in nuclear weapons, have been declared excess. DOE intends to convert most excess Pu-239 into mixed oxide fuel for use in commercial reactors.
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A residue from uranium enrichment operations, DOE's inventory includes over 700,000 metric tons of uranium hexafluoride (UF6) , which can produce toxic gases by reacting with moisture and air.
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was a principal objective of nuclear materials production in the United States from the 1940s through the late 1980s. Approximately 100 metric tons of Pu239 were obtained from the nuclear reactors and separations facilities at the Hanford, Washington, and the Savannah River, South Carolina, sites for use in nuclear weapons (see Chapter 3 and Appendix A)
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A key element in DOE's strategy for eventual disposal of its inventory is the conversion of as much of the excess Pu-239 as is technically and economically feasible into MOX fuel for commercial power reactors.4 The spent MOX fuel would be co-disposed with other spent nuclear fuels. However, approximately 17 metric tons of excess Pu-239 are in the form of scraps and residues, including very impure materials.
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The different characteristics affect the spent fuel's chemical stability and potential for gas generation, decay heat generation and potential for thermal damage under different storage and accident conditions, potential for inadvertent nuclear criticality, and attractiveness of the material for theft. The EMSP should support research to help ensure safe and secure storage and disposal of DOE SNF.
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Research to further develop reprocessing options where the spent fuel is dissolved in a molten salt or an aqueous solution and separate streams of well-characterized materials are created may help to address the specific issues of high enrichment and cladding stability. There are opportunities for collaboration with the new DOE Advanced Fuel Cycle Initiative to identify research that would make the reprocessing approach viable for some DOE spent fuels that would otherwise have difficulty meeting repository waste acceptance criteria.
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Research should lead to understanding potential failure mechanisms of the present capsuled ways to convert the isotopes to stable glass or ceramic forms and understanding longterm hazards of disposition options. There are opportunities for fundamental research to understand the chemical and physical alterations of CsCI and SrF2 under intense radiation, localized heating, and change of valence states accompanying radioactive decay.
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The most immediate risk posed by the DUF6 is its potential to react with moisture to form hydrogen fluoride, a highly corrosive and chem' cally toxic gas. DOE has recently taken a first step toward dispositioning its DUF6 by awarding an 8-year contract to Uranium Disposition Services to build and operate facilities at Paducah and at Portsmouth to convert it to the stable oxide U3O~.
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The Office of Science has an opportunity to lead other DOE offices and industrial partners in establishing a center of excellence to ensure that the United States has a continuing capability to handle and store large inventories of higher actinides for research, beneficial use, or as feedstock. EMSP-funded research directed at both fundamental science and new uses of the higher actinides can be an important step toward preserving the inventory.
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~ _` ~ ~ ~ ~ ~ . , , according to tne USA flu ~ ~ Standard, arresting the cladding degradation on some DOE spent fuels and preparing them for decades of storage before eventual disposal, and supporting DOE's plans to convert its DUF6 to a stable oxide.
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