Evaluation of initial temperature effect on transient fuel behavior under simulated reactivity-initiated accident conditions

Sugiyama, Tomoyuki ; Udagawa, Yutaka  ; Fuketa, Toyoshi

To evaluate possible effect of initial temperature on the fuel behavior, such as cladding deformation and fission gas release, in a reactivity-initiated accident, two comparative tests were performed on identical high burnup PWR fuel rods at different temperatures in the NSRR. Two tests RH-1 and RH-2 were performed, respectively, at room temperature and 280 C which corresponds to the hot zero power of PWR. The test rods did not fail in the both tests against fuel enthalpy increases of 462 and 378 J/g, respectively. The results of the two tests were consistent to those of previous tests at room temperature, if data were plotted as a function of the peak fuel enthalpy, not of the maximum increase of enthalpy. Computer analysis with the RANNS code confirmed that the cladding residual strain in RH-2 was driven only by the pellet thermal expansion and that the gas-induced strain did not occur because the cladding temperature did not reach high enough to enhance creep deformation.