Boron effects on fission product behavior under severe accident conditions

Miwa, Shuhei  ; Di Lemma, F. G.; Nakajima, Kunihisa  ; Osaka, Masahiko  

The basic studies have been performed for the evaluation of boron (B) release from the degraded BWR control rod material and its effect on cesium (Cs) and iodine (I) chemistry during a severe accident. The B effect on Cs and I chemistry was evaluated by thermal equilibrium calculation considering the change in B release behavior under the degradation of BWR control rod material. Results shows that The generation of gaseous iodine as well as CsBO could be suppressed under a steam-starvation atmosphere because of a lower B release fraction owing to the possible formation of stable iron Fe-B alloys. In response to this prediction result, the basic experiments and analyses are underway. The B release behavior from the boron carbide/stainless steel/Zircaloy reaction products, the thermochemical properties and phase states of complex Cs-B-O compounds are being studied. For the validation of all these evaluation results, reproductive test for FP release and transport will be performed.