Development of fission gas release model for MOX fuel pellets with treatment of heterogeneous microstructure

田崎 雄大; 宇田川 豊; 天谷 政樹

Journal of Nuclear Science and Technology, 59(3), p.382 - 394, 2022/03

https://doi.org/10.1080/00223131.2021.1973924

This study develops a new fission gas release (FGR) model for mixed oxide (MOX) fuels with a fundamentally heterogeneous microstructure. The model adopted in FEMAXI-8 was applied to irradiation Instrumented Fuel Assembly (IFA)-626 and 702 tests in which two types of MOX fuels had different heterogeneity in their microstructure, while the other spec were similar. Upon analyzing these fuels, the original FGR model predicted lower FGR from the fuel with a remarkably heterogeneous microstructure than the other MOX fuel. This estimation contradicts the experimental observation. However, the new FGR model improved the consistency because of the early release of fission gas from Pu agglomerate region, and showed issues for aiming further improvement. Therefore, the above results confirmed a certain validity of the developed model for studying heterogeneity effect.