Sensitivity Analysis of Fuel Cladding Temperature to Dry Cask Loading and Storage Conditions

Dry cask safety analyses and material degradation studies depend on reliable best- estimate thermal models. Gaps in design data and storage site conditions require analysts to frequently rely on bounding assumptions in thermal models that introduce bias to the results. Efforts to gather physical attributes of cask designs from vendors or experimental measurements can be costly and to determine all the uncertain parameters for a number of different cask designs is impractical. Measuring the sensitivity of peak cladding temperature to cask and fuel depletion modeling parameters was done to inform decision makers of which parameters that have the most impact on temperature predictions and should be further investigated. This study is applicable to vertical multi-purpose canister systems for long-term storage evaluations such as those done for an interim storage facility. The most sensitive cask parameters are those that affect convective heat transfer in the cask annulus and within the canister basket. These parameters are the ambient air temperature, canister pressure, and assembly decay heat profile with measured sensitivity coefficients of 0.50, -0.2841, and 0.0767, respectively. The sensitivity of peak cladding temperature to reactor cycle history was measured, and the most sensitive parameter was burnup, but other reactor operating history variations had little impact on temperature predictions.