The MC-10 PWR spent fuel storage cask: Testing and analysis

Abstract

A Westinghouse MC-10 pressurized water reactor (PWR) spent fuel storage cask was performance-tested. The performance test consisted of loading the MC-10 cask with 24 PWR spent fuel assemblies from Virginia Power's Surry reactor. Cask surface and fuel assembly guide tube temperatures, as well as cask surface gamma and neutron dose rates, were measured. Testing was performed with vacuum, nitrogen, and helium backfill environments in both vertical and horizontal cask orientations. Limited spent fuel integrity data were also obtained. Results of the performance test indicate that, when dissipating 12.6 kW, the MC-10 cask exhibited exceptionally good heat transfer performance. Maximum measured assembly guide tube temperatures in vacuum, nitrogen, and helium backfills in a vertical cask orientation were 212, 172, and 134C, respectively. Significant convection heat transfer was present in the vertical nitrogen run, and a lesser effect was observed in the vertical helium test run, as indicated by peak temperatures occurring in the upper regions of the fuel assemblies. Pretest temperature predictions of the COBRA-SFS heat transfer computer code were in good agreement with test data, and post-test predictions agreed exceptionally well (30C) with data. Cask surface gamma and neutron dose rates were measured to be less than the design goalmore » of 68 mrem/h except on the bottom of the cask where dose rates as high as 85 mrem/h were measured. This dose rate could be reduced by adding more gamma shielding. Dose rates of 50 mrem/h were measured on the side of the cask. It was concluded that, with minor refinements, the MC-10 PWR storage cask can be satisfactorily implemented to safely store spent fuel from both heat transfer and shielding performance perspectives. 35 refs., 111 figs., 16 tabs.« less