2020 Volume 69 Issue 12 Pages 333-350
Authors report susceptibility of IG-crack in the simulated PWR primary water and discuss the mechanism of the IG-crack of Type-316 stainless steel. First, the authors compare the crack propagation rates of the stainless steels in chloride solution, simulated BWR and PWR primary water. By referring the Wagner lengths in three solutions, we also discuss whether the anodic current density can be compensated by the cathodic reaction rate when wet corrosion is associated in the IG-cracks in these three solutions.
Next we introduce stress relaxation of the Type-316 stainless steel at 340℃ and discuss the test methods required to reproduce the IG-crack in the simulated PWR primary water. In the third, we report IG-SCC test methods and test results performed by two our research laboratories and how the cold worked Type-316 stainless steel is highly resistant against the IG-crack in the simulated PWR primary water. We could not produce the IG-crack as long as we use notched specimens, however, the IG-crack propagated for the limited tests by the K-increase type loading of the specimens with fatigue induced pre-cracks. The authors propose a self-healing mechanism of the Type-316 stainless steel to explain how this steel is stable in the simulated PWR primary water.
