Investigation of the Mechanism of IGA/SCC of Alloy 600 in Corrosion Accelerating Heated Crevice Environments. Nuclear Energy Research Initiative (NERI) Program.

Lumsden, J.

Technical Information Center Oak Ridge Tennessee

关键词: Stress corrosion;    PWR type reactors;    Inconel 600;    Steam generators;    Crack propagation;   

RP-ID  :  DE2002762168

学科分类：工程和技术（综合）

美国|英语

来源: National Technical Reports Library

【 摘 要 】

This program focuses on understanding mechanisms causing corrosion damage to steam generator tubes in a pressurized water reactor (PWR). The crevice formed by the tube/tube support plate (T/TSP) intersection in a PWR steam generator is a concentration site for nonvolatile impurities (referred to as hideout) in the steam generator water. The restricted mass transport in the small crevice volume prevents the species, which concentrate during the generation of steam, from quickly dispersing into the bulk water. The concentrated solutions in crevices have been a contributing cause of several forms of corrosion of steam generator tubes including intergranular attack/stress corrosion cracking (IGA/SCC), pitting, and wastage. Damage to Alloy 600 steam generator tubes by IGA/SCC continues despite rigorous water chemistry controls during power operation. The continued degradation has resulted in operational leakage, extensive tube inspections and repair. Eventually, replacement of steam generators or plant decommissioning must be considered. Many remedial actions against IGA/SCC have been taken, which include: increases in secondary water purity, reductions in oxygen ingress, use of buffers such as boric acid, injecting of hydrazine to maintain reducing conditions, and control of molar ratios of cations and anions.