The Swedish internal recirculation pump BWRs are operated with normal water chemistry (NWC). Recent laboratory observations of increased stress corrosion crack growth rates (SSCGRs) of RPV low alloy steel (LAS) in oxygenated water at 3-5 ppb chloride led to renewed interest in SCC of LAS and e.g., revision of EPRI BWRVIP-233 and BWR water chemistry guidelines. Still, limited data have beenavailable at K above 50 MPa√m for LAS plate-material sulfur contents in the upper range of the low-sulfur regime.
A plate of ASTM A533, Gr. B Class 1 with 0.011 wt.% sulfur from the archive materials of Barsebäck RPV was retrieved for SCC testing in BWR NWC environment. SCCGR testing was conducted in a multi-CT autoclave with 8 actively loaded 1.5 TCT specimens. Specimens were tested at constant K of between 50-70 MPa√m as well as with periodic partial unloading (PPU). The water chemistry was varied between 500-2000 ppb of oxygen while keeping ECP of specimens no lower than +80 mV SHE. Testing was started in clean NWC followed by a sequence of chloride transients of 3-90 ppb. Results show that CGRs are in the expected regime, though initiating and sustaining crack growth is difficult, partly due to localized growth.