Experimental study of advanced fuel-pin failure phenomena

A direct-electrical-heating apparatus was used to perform fundamental fuel-motion experiments on unirradiated, clad and unclad UC pellets to investigate the response of the fuel to simulated in-reactor transient heating rates and power levels. The results show that the response of UC to applied power transients is significantly different than UO2 behavior in similar situations. Because of the large temperature interval between the boiling and melting points of UC and the high thermal conductivity of UC that results in relatively flat radial temperature gradients, two regimes of gross fuel motion can occur, depending upon the fuel centerline temperature