Crack Growth Rate in Irradiated Core Barrel Weld and Heat-Affected Zone in PWR Primary Water

Abstract

Fluence impact on stress corrosion cracking (SCC) of stainless steel welds and heat affected zone (HAZ) in pressurized water reactors (PWR) is an area where additional data are needed. Crack growth rate (CGR) testing was therefore performed on 0.5TCT specimens fabricated from a core barrel weld and HAZ (Type 304) at 1.5 dpa. Testing was conducted in simulated PWR primary water at 290, 320 and 340 °C and stress intensity factors (K) ranging from 15 to 30 MPa√m. The materials tested in this study were resistant to stress corrosion cracking in the environments investigated, as it was very difficult to sustain crack growth under constant K conditions. Similar CGRs were observed for the HAZ and weld metal, and all data fall well below the irradiation-assisted stress corrosion cracking (IASCC) CGR model curves, even though most of the data were obtained under loading conditions that involved partial periodic unloading (PPU) and a hold time at maximum load. At the low CGRs observed, the relative contribution from reload events to the total rate observed was large. Dependencies on K and temperature were observed, although the change in CGR with K was somewhat flatter and the activation energy was lower than reported in the literature. The paper discusses the effects of K, temperature, and PPU with hold time on the CGR.