Modeling Comparisons with an Aboveground Dry Cask Simulator

The performance of commercial nuclear spent fuel dry storage casks is evaluated throughdetailed analytical modeling of the system´s thermal performance. Therefore, a thermalmodeling subcommittee has been created in the Extended Storage Collaboration Programme(ESCP) which consists of different phases.The purpose of Phase I was to produce validation-quality data that can be used to test theaccuracy of the modeling presently used to determine cladding temperatures in modern verticaldry casks. To produce these data sets under well-controlled boundary conditions, the dry casksimulator (DCS) was built at Sandia National Laboratories to study the thermal-hydraulicresponse of a single boiling water reactor (BWR) fuel assembly under a variety of heat loads,internal vessel pressures, and external configurations.In this paper, the modeling results of ENUSA-UPM are compared to a select set of the DCS tests.A detailed model has been created using STAR-CCM+, a computational fluid dynamics (CFD)code, and representing fuel rods and water rods in the assembly in detail, which results in theadvantage of the cladding temperature for every rod being calculated discretely. To define thetest boundary conditions, the basic geometry, and material properties, a handbook with therequired information was provided by Sandia National Laboratories.The results for a selected number of cases (5 kW for 100 kPa and 800 kPa; 0.5kW for 100 kPa and 800 kPa) show goodagreement with the experimental data, with a maximum relative peak cladding temperature(PCT) error of 3%. Note that all pressures are absolute.Regarding the air mass flow rate results, a maximum relative error of 10% compared to the testmeasurements is obtained, except for the low pressure (100 kPa) and low power (0.5kW) cases,where the relative error is higher (20%). This increased error is likely related to the highsensitivity observed in setting the inlet boundary condition as a jump in air pressure.