STP725

    Significance of Radiation Effects in Solid Radioactive Waste

    Published: Jan 1981


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    Abstract

    Proposed Nuclear Regulatory Commission criteria for disposal of high-level nuclear waste require development of waste packages to contain radionuclides for at least 1000 years, and design of repositories to prevent radionuclide release at an annual rate greater than 1 part in 100 000 of the total activity. The high-level wastes that are now temporarily stored as aqueous salts, sludges, and calcines must be converted to high-integrity solid forms that resist deterioration from radiation and other effects of long-term storage. Spent fuel may be encapsulated for similar long-term storage.

    Besides the spent fuel elements themselves, candidate waste forms include borosilicate and related glasses, mineral-like crystalline ceramics, concrete formulations, and metal-matrix glass or ceramic composites. These waste forms will sustain damage produced by beta-gamma radiation up to 1012 rads, by alpha radiation greater than 1019 particles/g, by internal helium generation greater than about 0.1 atom percent, and by the atom transmutations accompanying radioactive decay. Current data indicate that under these conditions the glass forms suffer only minor volume changes, stored energy deposition, and leachability effects. The crystalline ceramics appear susceptible to the potentially more severe alterations accompanying metamictization, and natural analogs of candidate materials are being examined to establish their suitability as waste forms. Helium concentrations in the waste forms are generally below thresholds for severe damage in either glass or crystalline ceramics at low temperatures, but microstructural effects are not well characterized. Transmutation effects remain to be established.

    Keywords:

    radiation effects, radioactive waste, nuclear waste, geologic repository, waste forms, borosilicate glass, crystalline ceramics, leachability, metamictization, helium generation, transmutation, fission products, actinides


    Author Information:

    Permar, PH
    Research staff engineer and research associate, Savannah River Laboratory, E. I. du Pont de Nemours & Co., Aiken, S.C.

    McDonell, WR
    Research staff engineer and research associate, Savannah River Laboratory, E. I. du Pont de Nemours & Co., Aiken, S.C.


    Paper ID: STP28210S

    Committee/Subcommittee: E10.07

    DOI: 10.1520/STP28210S


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