Behavior of high-burnup PWR fuels with low-tin Zircaloy-4 cladding under reactivity-initiated-accident conditions

Experimental programs on fuel behavior during simulated reactivity-initiate d-accident (RIA) conditions at the Nuclear Safety Research Reactor (NSRR) i n Japan and the CABRI test reactor in France appear to indicate that claddi ng failures may occur at enthalpy values lower than Would be expected. Resu lts from two experiments designated as HBO-1 in NSRR and REP Na-1 in CABRI indicate that the occurrence of fuel failure is strongly influenced by corr osion of cladding in the tested fuels. However, data had been limited to fu el rods with conventional (1.5% Sn) Zircaloy-4 cladding. Results are descri bed from newly conducted NSRR experiments, TK test series, for 38 to 50 MWd /kg U pressurized water reactor fuels with low-tin (1.3% Sn) Zircaloy-4 cla dding, and anticipated processes of fuel behavior during the transient are discussed.