Fission gases and helium gas behavior in irradiated mixed oxide fuel pin

Sato, Isamu; Katsuyama, Kozo ; Arai, Yasuo

Release behavior of fission gases such as Kr and Xe from fuel pellets has been extensively investigated from the viewpoints of increase of internal pressure of fuel pins and swelling of fuel pellets. He also contributes to increase the internal pressure of fuel pins, especially in the case of minor actinide containing MOX fuel. In this work, the amounts of fission gases and He in a fuel pin irradiated in the experimental fast reactor, JOYO, to -50 GWd/t as a pin average burnup were quantitatively measured by pin puncture and pellet heating tests. As results, the release fractions of fission gases from fuel pellets were about 50%, but He was released by more than 70%. In addition, 20% of He may be derived from -decay of actinide species after irradiation. It was suggested that most of He generated during irradiation was released because of the high temperature like in fast reactor environment.