[3E04-07] Irradiation behavior analysis

[3E05] Preliminary Study of Fission Gas Release Model for MOX Fuels with Treatment of Heterogeneous Microstructure

*Yudai Tasaki¹, Yutaka Udagawa¹, Masaki Amaya¹ (1. Japan Atomic Energy Agency)

Keywords:MOX fuel, FEMAXI-8, Pu spot, Fission gas release

Mixed Oxide (MOX) fuels are fabricated by mixing depleted UO₂ powder and PuO₂ powder, so the microstructure may be more or less heterogeneous with respect to Pu enrichment. A fuel performance modeling code:FEMAXI-8 supposes the microstructure to be homogeneous; it is difficult for FEMAXI-8 to directly handle several kinds of microstructures for evaluating fission gas behavior. This study develops fission gas release (FGR) model such that the analytical system represents Pu agglomerate region so called as Pu spot and matrix region. Upon analyzing two kinds of MOX fuels irradiated in IFA-626, The new model shows that the concentration of fission gas in the grain boundary of Pu spot early increases, which improves the reproducibility of the experimental data.