Importance of modeling assumptions in understanding fuel/coolant interactions from in-pile autoclave experiments

EPIC code has been used to examine post-pin-failure motion of fuel into the sodium-filled coolant channel, quenching of the fuel, heating of the sodium, and piston motions generated by the pressures in the fuel-coolant interaction zone. The present study focuses on some of the uncertainties associated with extending EPIC modeling to calculate pressure wave propagation in autoclave geometry and discusses how these uncertainties complicate an understanding of the source pressurizations in the experiments. The specific geometry and test conditions of the PBE-5S experiment will be used for the example calculations. 9 refs