Release and transport behaviors of non-gamma-emitting fission products and actinides in steam and hydrogen atmospheres

•The release behaviors of non-gamma-emitters from fuel were investigated.•Released fractions were calculated based on chemical analysis of deposits.•The release of strontium was significantly enhanced in hydrogen atmosphere.•The release of uranium was enhanced in steam atmosphere. In order to improve and enlarge the experimental database on the fission product (FP) and actinide release and transport behaviors under severe accident conditions, the release and transport of non-γ-emitting FPs and actinides in steam and hydrogen atmospheres were investigated based on the chemical analysis of their deposits on the components of VERCORS test loops. Released fractions of FPs and actinides were calculated by using elemental amounts obtained by chemical analysis. The effects of atmosphere on the release and transport behaviors were discussed for 13 non-γ-emitting FPs and actinides considering the stability of their compounds. It was seen that the release of Sr was significantly enhanced in hydrogen atmosphere and a portion of released Sr was transported towards the lower temperature region. The release of U was enhanced in steam atmosphere. Atmospheric dependences for other non-γ-emitting FPs and actinides were in accordance with previously obtained experimental data.