Fission gas release in BWR fuel with a burnup of 56 GWd/t during simulated reactivity initiated accident (RIA) condition

Amaya, Masaki  ; Sugiyama, Tomoyuki ; Nagase, Fumihisa ; Fuketa, Toyoshi

Pulse irradiation simulating reactivity initiated accident (RIA) condition was conducted for the test rod prepared from the BWR fuel rod with a burnup of 56 GWd/t irradiated in a commercial reactor, and fission gas release during the pulse irradiation was investigated based on the result of rod-puncture test and electron-probe-microanalysis of fuel pellet. The local xenon concentration of pulse-irradiated pellet decreased compared with that of base-irradiated pellet in the relative radius of 0 to approximately 0.8. The decrease corresponds to a fractional fission gas release of approximately 11%, and this value was comparable with the rod-puncture test result. Considering the microstructural change in fuel pellet and the amount of retained gas in grain boundary, it is likely that the fission gas release during pulse irradiation was affected by the grain boundary separation which occurred in the mid-radius rather than the peripheral region of fuel pellet during pulse irradiation.