Identification of radical position of fission gas release in high-burnup fuel pellets under RIA conditions

Sasajima, Hideo ; Sugiyama, Tomoyuki ; Chuto, Toshinori; Nagase, Fumihisa ; Nakamura, Takehiko ; Fuketa, Toyoshi

Fission gas release positions in high burnup fuel pellets were examined after the pulse-irradiations which simulated reactivity initiated accident (RIA) conditions in the Nuclear Safety Research Reactor (NSRR). The ratio of xenon to krypton ((Xe/Kr) ratio) in the released gas showed that fission gas was released from the entire region of the pellets of the examined PWR fuels during the pulse-irradiations. On the other hand, most fission gas was released from the center and/or intermediate regions of the examined BWR fuel pellets. Consequently, it is likely that fission gas is not released selectively from the rim structure at the pellet periphery under RIA conditions.