Behavior of LWR/MOX fuels under reactivity-initiated accident conditions

反応度事故条件下における軽水炉MOX燃料の挙動

更田 豊志; 杉山 智之 ; 梅田 幹 ; 笹島 栄夫 ; 永瀬 文久 

Fuketa, Toyoshi; Sugiyama, Tomoyuki; Umeda, Miki; Sasajima, Hideo; Nagase, Fumihisa

Behavior of LWR fuels during reactivity-initiated accident (RIA) is being studied with pulse-irradiation experiments in the Nuclear Safety Research Reactor (NSRR). The tests BZ-1 and BZ-2 were performed on PWR-MOX fuel rods irradiated in the Beznau NPP in Switzerland. The BZ-1 test fuel rod contained pellets produced with the Short Binderless Route (SBR) process. The local burnup was 48 GWd/t. On the other hand, the pellets of the BZ-2 test fuel rod were produced with the Micronized Master blend (MIMAS) process. The local burnup was 59 GWd/t. The two tests resulted in PCMI failure, a long axial clack was generated and fragmented pellets were found in the capsule water. Subsequently to the above-mentioned BZ-2 test, a sibling rod was subjected to the NSRR experiment at high temperature by using newly developed capsule. The result from this test BZ-3 is also described and discussed in the paper.