TRANSIENT-BEHAVIOR OF LOW ENRICHED URANIUM SILICIDE MINIPLATE FUEL UNDER A TRIPLET CONFIGURATION

This paper describes the results of a transient experiment using low e nriched (<20 wt% U-235) uranium silicide research reactor miniplate fu el. Three silicide miniplate fuel specimens assembled in a tripler con figuration with a water gap of 2.38 mm were pulsed in the Nuclear Safe ty Research Reactor (NSRR) with an energy deposition of 78 cal/g . fue l. The results obtained in this study are summarized as follows: (1) U nder a restricted condition of coolant cross flow, the mid-plate in th e triplet configuration (pulsed at 78 cal/g . fuel) showed an extremel y high peak cladding surface temperature (PCST), 475 degrees C, which was higher than that of the other two plates (173 and 192 degrees C). The temperature of coolant in the water gap increased rapidly to 140 d egrees C while that at the non-gap locations increased to about 50 deg rees C. Despite the poor cooling conditions, especially at the mid-pla te, the three silicide miniplate fuels did not fail mechanically. Owin g to the comparatively slow quenching rate from PCST and/or the small magnitude of the temperature drop during quenching, the fuels might no t be subjected to the local tensile stress necessary to cause through- plate cracking. (2) The bowing of the miniplate fuel caused the 2.38 m m water channel gap to be narrowed to 48% of its maximum. The uneven c oolant temperature profiles in the water gaps between the miniplates m ight be a cause for the bowing.