Tungsten transmutation and resonance self-shielding in PPCS models for the study of sigma-phase formation
Transmutation reactions in plasma-facing tungsten produce rhenium and osmium at levels which may trigger the formation of brittle sigma phase in the W-Re-Os alloy. A study has been carried out, updating previous work, to analyse this issue in three fusion power plant models whose neutron transport behaviour is representative of a wide range of possible options. Self-shielding effects in giant tungsten resonances have now been accounted for. Results show the importance of this treatment and the significant influence of the overall neutron behaviour in the blanket, in particular the presence of strongly moderating materials such as water or beryllium. Analysis of the evolution of the Re/Os concentrations with time shows that in no case is sigma phase formation potential reached within the service lifetime of the components.