Initiation of SCC in nickel base alloys in primary PWR environment: studies at Studsvik since mid 1980s

Abstract

AbstractInvestigations on initiation of primary water stress corrosion cracking (PWSCC) in alloys 600 and 690 in simulated primary pressurised water reactor (PWR) environments, carried out since 1985, are reviewed. A large number of tests, mostly on reverse U bend specimens, some from steam generator tubes from operating PWRs, have been conducted for periods up to 33 000 h (4 years). Most exposures were at 365 or 330°C in either high purity water with hydrogen addition or simulated primary water (representing beginning of cycle conditions). Parameters investigated include: material (composition, heat treatment (mill annealed or thermally treated), carbide distribution, yield strength, grain size, etc.), environmental (hydrogen content, boron–lithium–pH, zinc) and experimental environment control techniques. Although the PWSCC mechanism has yet to be fully explained, these studies provide an overview of important parameters for crack initiation. The present review aims to survey the evidence for PWSCC init...