Spectral effects on defect production in the reactor pressure vessel of a pressurized heavy-water reactor

Embrittlement predictions of reactor pressure vessels of typical pressurize d water reactors are conventionally carried out using well established tren d curves developed in terms of fast fluence as the correlation parameter. H owever, such quantification of irradiation damage cannot be applied when la rge spectral differences appear. We describe an atypical irradiation enviro nment at a pressurized heavy-water reactor (PHWR), where the nature of the damage produced by low-energy neutrons is of importance. We show that at th e irradiation position below the core of the PHWR, spectral effects on the primary recoil distribution have a substantial influence on the resulting d isplacement damage represented in terms of the number of surviving defects. This study illustrates the implications that spectral differences may have when considering the life extension of nuclear power plants.