Spent Fuel Waste Form Characteristics: Grain and Fragment Size Statistical Dependence for Dissolution Response

Stout, R. B.; Leider, H.; Weed, H.; Nguyen, S.; McKenzie, W.; Prussin, S.; Wilson, C. N.; Gray, W. J.; ,

Spent Fuel Waste Form Characteristics: Grain and Fragment Size Statistical Dependence for Dissolution Response

by R. B. Stout, Univ of California, Livermore, United States,
H. Leider, Univ of California, Livermore, United States,
H. Weed, Univ of California, Livermore, United States,
S. Nguyen, Univ of California, Livermore, United States,
W. McKenzie, Univ of California, Livermore, United States,
S. Prussin, Univ of California, Livermore, United States,
C. N. Wilson, Univ of California, Livermore, United States,
W. J. Gray, Univ of California, Livermore, United States,

Document Type: Proceeding Paper

Part of: High Level Radioactive Waste Management 1991

Abstract:

The Yucca Mountain Project of the U.S. Department of Energy is investigating the suitability of the unsaturated zone at Yucca Mountain, NV, for a high-level nuclear waste repository. All of the nuclear waste will be enclosed in a container package. Most of the nuclear waste will be in the form of fractured UO₂ spent fuel pellets in its Zircaloy-clad from electric power reactors. If failure of both the container and its enclosed clad rods occurs, then the fragments of the fractured UO₂ spent fuel will be exposed to their surroundings. Even though the surroundings are an unsaturated zone, a possibility of water transport exists, and consequently, UO₂ spent fuel dissolution may occur. A repository requirement imposes a limit on the nuclide release per year during a 10,000 year period; thus the short term dissolution response from fragmented fuel pellet surfaces in any given year must be understood. This requirement necessitates that both experimental and analytical activities be directed toward predicting the relatively short term dissolution response of UO₂ spent fuel. The short term dissolution response involves gap nuclides, grain boundary nuclides, and grain volume nuclides. Analytical expressions are developed that describe the combined geometrical influences of grain boundary nuclides and grain volume nuclides on the dissolution rate of spent fuel.

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