IGSCC mitigation concept for BWRs by preventive water chemistry

With increase in operating years of BWR plants, the number of the incidents of intergranular stress corrosion cracking (IGSCC) has been increasing among the Japanese BWRs. It is widely known that IGSCC of structural materials occurs when three factors co-exist, i.e. material, stress and environment (water chemistry). These years the importance of water chemistry improvement from the viewpoint of IGSCC mitigation has been strongly recognized and as a result hydrogen water chemistry (HWC) has been adopted at some of Japanese BWRs. At certain sites, however, an ample injection of hydrogen to the plant has not been achieved due to N-16 radiation increase in turbine building. (author)