A probabilistic assessment of PWR SNF pinching failure considering hydride-related cladding embrittlement

A probabilistic methodology to investigate pinching failure of pressurized water reactor (PWR) spent nuclear fuel (SNF) rod cladding is presented. The considered accident scenario is a 9-m SNF transportation cask drop after long-term SNF dry storage. The offset strain was used to evaluate cladding failure. A set of 3000 pinching scenarios was generated via Latin Hypercube Sampling (LHS) of geometrical, material, and loading parameters and finite element (FE) models were developed to simulate each scenario. The methodology considers hydride-related cladding embrittlement related to SNF dry storage cool-down. Regression and interpolation models were developed to estimate the cladding offset strain capacity as a function of cladding hydrogen content, peak vacuum drying cladding hoop stress, and cladding temperature at the moment of load application. The probabilistic results indicate a small likelihood of hydride-related pinching failure in the considered accident scenario, after 30 or 300 years of SNF dry storage.