High burnup fuel behavior under high temperature RIA conditions

Sugiyama, Tomoyuki 

A series of pulse-irradiation tests, simulating reactivity-initiated accidents (RIAs), was performed on high burnup PWR and BWR fuel rods at high temperature of 280 C in the NSRR. Influence of high temperature on the fuel behavior was assessed on the basis of the transient records in the pulse irradiation and the results from detailed examinations of the test fuel rods. As for the stress-relieve annealed cladding, fuel enthalpy at failure was correlated well with the cladding oxide thickness which represents the hydride rim thickness. Increase of failure limit at high temperature was evaluated as 20 cal/g from available data at the present. On the other hand, further data and investigation are needed to obtain the tendency of failure limit of the recrystallization annealed cladding.