Effectiveness of Hydrogen Additions for Mitigation of Stress Corrosion Cracking in BWR Environments

Abstract The intergranular stress corrosion cracking (IGSCC) propensities of typical boiling water reactor (BWR) piping materials as affected by the level of oxygen dissolved in the BWR water are discussed. Particular emphasis is placed on stress corrosion resistance of Type 304 stainless steel which is used for BWR piping in operating plants. It is demonstrated that, below a threshold dissolved oxygen level, IGSCC of sensitized Type 304 stainless steel does not occur. The effectiveness of using hydrogen for oxygen suppression is discussed. Laboratory tests demonstrated that hydrogen has a high probability of success in mitigating IGSCC in older operating BWR's where more IGSCC-resistant materials (such as Nuclear Grades Type 316 and Type 304 stainless) and improved processing techniques such as corrosion resistant cladding and heat sink welding cannot be readily implemented. In-reactor studies have indicated that hydrogen can be practically added to the BWR plant with minimum system impact.