Behavior of PCI-resistant additive fuel for BWR under reactivity initiated accident conditions.

This report describes the results of reactivity initiated accident (RIA) experiments using UO2 fuel pellets containing additives which enhance the pellet-cladding interaction (PCI) resistance of BWR fuels. The results obtained were: (1) The failure thresholds of the PCI resistant fuels with additives were not less than 260 cal/g·UO2 (220 cal/g·UO2 in enthalpy) and no measurable differences in failure thresholds were observed between the fuels with additives and the conventional BWR (and NSRR standard) fuels. (2) No measurable difference in the threshold for mechanical energy release existed between the PCI resistant fuel with additives and the conventional BWR (and NSRR standard) fuels. The threshold was estimated to be approximately 335 cal/g·UO2 (285 cal/g·UO2 in enthalpy) for the fuels with additive. This is also the value previously established for the NSRR standard fuel rods.