Year
2016
Abstract
Sabotage of spent nuclear fuel casks remains a concern nearly forty years after attacks against shipment casks were first analyzed. A limited number of full-scale tests and supporting efforts using surrogate materials, typically depleted uranium dioxide (DUO2), have been conducted in the interim to more definitively determine the source term from these postulated events. Additional small scale studies have been conducted to characterize the aerosols generated from the high-energy disruption of fresh, irradiated, and surrogate fuel samples. These efforts presented respirable release fraction (RRF) data as a function of energy density. The respirable release fraction is one of the principal quantities that defines the source term and directly relates to the consequence of an event. A thorough understanding of the relevant RRF data is therefore required for best-estimate consequence analyses and statistical interpretations. Previous examinations of available fragmentation data involving spent nuclear fuel (SNF) and surrogates have been presented in two extensive handbooks, one published by the Nuclear Regulatory Commission (NRC) and the other by the Department of Energy (DOE). These handbooks present RRF data with little discussion of the underlying assumptions in their interpretations. The current analysis will reconstruct the existing handbook results from the source data and present alternative assumptions and interpretations, which are statistically defensible. The RRF presented in the NRC handbook gives values that are approximately 3 to 10 times higher than the best-estimate (least-squares) values derived directly from the original data over the energy densities of interest.