Fission gas release behavior of MOX fuels under simulated daily-load-follow operation condition; IFA-554/555 test evaluation with FASTGRASS code

Ikusawa, Yoshihisa   ; Ozawa, Takayuki   

IFA-554/555 load-follow tests were performed in HALDEN reactor to study the MOX fuel behavior under the daily-load-follow operation condition in the framework of ATR-MOX fuel development in JAEA. In this report, FP gas release behavior of MOX fuel rod was evaluated under the daily-load-follow operation condition with the examination data from IFA-554/555 by using the computation code FASTGRASS. As the computation results of FASTGRASS code, which could compute the FP gas release behavior under the transient condition, it could be concluded that FP gas would release due to the relaxation of fuel pellet inner stress, which were caused by the cyclic power change during the daily-load-follow operation. In addition, since the amount of released FP gas would decrease during the steady operation after the daily-load-follow, it could be mentioned that the total of FP gas release at the end of life with the daily-load-follow would not be so much different from that without the daily-load-follow.