A research team in Japan has compared the stress corrosion cracking resistance of materials used for steam generator tubing within nuclear power plants in an effort to try to identify new materials for long-term reliability.
“Nuclear power is an important, effective, and affordable energy source”, says Koji Arioka, chief researcher for the Institute of Nuclear Safety System located in Fukui Prefecture. “It’s crucial to keep reactors operating efficiently and to ensure their safety and reliability beyond a 60-year lifespan, so the development of alternative materials with long-term reliability is essential but difficult.” To do this, the team explored the dependence of stress corrosion cracking growth on nickel and chromium in pressurised water reactor primary water—with the goal of gaining a basic understanding of stress corrosion cracking behaviour of steam generator tubing materials.
The researchers also focused on gaining a deeper understanding of whether accelerated testing at higher temperatures is appropriate for predicting stress corrosion cracking initiation and growth at lower temperatures. Among their key findings, the team found ‘excellent’ stress corrosion cracking growth resistance for 20% cold-worked Alloy 800NG (nuclear grade) at 320°C and 340°C. They observed a significant effect of nickel on inter-granular stress corrosion cracking resistance at 340°C and 360°C.