Thermal Analyses Performed for the NRC Package Performance Study (PPS) Test Protocols

In a study being performed at Sandia National Laboratories called the Package Performance Study (PPS), the US Nuclear Regulatory Commission (NRC) is examining the response of transportation casks to extreme transportation accident conditions. This study proposes to conduct analyses and tests of full-scale rail and full-scale truck casks including a high-speed impact with an unyielding surface followed by an extreme fire. This paper summarizes the thermal analyses that were performed for the test protocols that were published for public review. A series of preliminary three-dimensional coupled finite element (FEA) and computational fluid dynamics (CFD) analyses were conducted with a reference rail cask and a reference truck cask. Three cases were investigated for the rail cask to better understand the effect of the vapor dome on heat transfer from the fire to the cask and to estimate the height above the fuel pool surface at which the package should be placed so that it is outside of the vapor dome and receives a nearly uniform heat flux from the fire envelope. The heights of the rail cask above the fuel pool surface were 0.3m, 1.3m, and 3.3m. For the truck cask, only a 1.0m above-the-pool simulation was performed. In each case, the casks were fully engulfed by a simulated fire. In each simulation, the fire engulfed the package for one hour and quiescent (no wind) conditions were assumed for the duration of the simulation. The FEA code MSC PATRAN/Thermal was used to capture the heat transfer response of the casks and it was coupled with the Container Analysis Fire Environment (CAFE) CFD fire code, which simulates fires in a realistic manner. Peak temperatures and heat fluxes for the two reference casks and fire configurations are compared and discussed.