Rock-like oxide fuel behavior under reactivity initiated accident conditions

Pulse irradiation tests of two types of rock-like oxide (ROX) fuel, i.e. yt tria stabilized zirconia (YSZ) and YSZ/Spinel composite, were conducted in the Nuclear Safety Research Reactor (NSRR) to investigate the fuel behavior under reactivity-initiated accident conditions. The ROX fuels failed with cladding burst at fuel volumetric enthalpies above 10 GJ m(-3), which was c omparable to that of UO2 fuel. The failure of the ROX fuels, however, occur red with considerable fuel melting and was quite different to that of UO2 f uel, which was caused by cladding melting and embrittlement due to heavy ox idation. Lower fuel melting temperature of the ROX fuels compared to that o f UO2 contributed to the different fuel failure modes. Certain amount of mo lten ROX fuel dispersed out at the failure. However, the mechanical energy generation due to the molten fuel/water interaction was negligible for the ROX fuels at peak fuel enthalpies below 12 GJ m(-3). (C) 2001 Elsevier Scie nce Ltd. All rights reserved.