Summary of the pulse irradiation experiment TK and FK

Sasajima, Hideo 

RIA-simulating pulse-irradiation tests were performed with 38-61 GWd/t PWR and BWR fuels as the TK and FK series. By using fuels which had similar irradiation histories in each test series, systematic results were obtained on hydride-assisted PCMI failure and fission gas release as well as on the failure conditions. In the PWR fuel cladding, radial cracks were generated in the hydride rim at the early phase of pellet-cladding mechanical interaction. In the high burnup BWR fuel cladding, radially-oriented hydrides have the influence on crack initiation and propagation. Higher FGR and larger deformation were observed in the fuels which experienced DNB during the pulse irradiations. To understand on post-failure events, data on dynamic fission gas release during the transient is needed. The information obtained in the TK and FK test series is valuable for clarifying the failure mechanism of the high burnup fuel, evaluating the results of the ALPS program and planning the future tests.