Effects of water chemistry on corrosion behavior of 316 stainless steel in PWRs

Abstract

The primary circuit of pressurized water reactors (PWRs) is maintained in high pressure and temperature water environments during the normal operation of nuclear power plants (NPPs). Especially, the austenitic 316 stainless steels used by structural materials and piping in primary side of PWRs were exposed to corrosive environments, and which causes various degradation mechanism due to the corrosion such as primary water stress corrosion cracking (PWSCC) and environmentally-assisted fatigue (EAF). Therefore, the addition of zinc to primary water chemistry and the optimization of concentration of dissolved hydrogen have been debated in worldwide for mitigation of these degradation mechanisms. In this thesis, the corrosion behavior of type 316 stainless steel depending on the zinc addition and concentration of dissolved hydrogen in primary water chemistry is presented by analyzing the oxide film formed in various environments. As the results, the difference in corrosion behavior is not significant in the change in concentration of dissolved hydrogen, however, the properties of oxide film and corrosion resistance are improved when zinc is injected.