Stress Corrosion of High-Chromium Nickel-Base Weld Metals and AISI 316 Nuclear Grade Stainless Steel in Simulated Boiling Water Reactor Environments

The stress corrosion cracking (SCC) susceptibility of AISI 316 NG (nuclear grade) stainless steel (SS), which had been welded with three high-chromium nickel-base weld metals (I-72, R-127, and R-135), was investigated by means of a series of slow strain rate tests (SSRTs) at a strain rate of 2×10⁻⁷s⁻¹⁠. Tests were conducted in simulated boiling water reactor (BWR) environments at 288 C, which simulated either the normal BWR primary coolant chemistry or the impure (SO₄²⁻) chemistry that results from the intrusion of resin from the demineralizer system. The results indicated that all of the materials were immune to SCC in the normal BWR environment. In the resin intrusion environment, both the I-72 and R-135 weld metals were immune to SCC, but the R-127 material exhibited intergranular stress corrosion cracking (IGSCC). The AISI 316 NG SS was susceptible to transgranular stress corrosion cracking (TGSCC) in the resin intrusion environment, except when welded with I-72, in which case it was immune to SCC.