Masato Koshiishi
Nuclear Plant Service Dept., Hitachi-GE Nuclear Energy, Ltd.
Haruo Fujimori, Dr. Eng.
Nuclear Plant Service Dept., Hitachi-GE Nuclear Energy, Ltd.
Masaya Okada
Nuclear Equipment Manufacturing Dept., Hitachi-GE Nuclear Energy, Ltd.
Akihiko Hirano
Dept. of Materials Research for Power Plants, Material Research Lab., Hitachi Research Lab., Hitachi, Ltd.
Stainless steel and nickel-based alloys are used in key equipment in BWRs, including reactor internals. Examples of SCC have been experienced in both materials. Because measures for dealing with SCC are an important issue for coping with aging plants, Hitachi has for many years been working on techniques for preventing SCC initiation and applying these techniques in actual plants. Recent measures for dealing with SCC have included identifying the factors leading to non-sensitized SCC and confirming the effectiveness of countermeasures. Development is also proceeding on new materials that can minimize SCC, including work on evaluating SCC characteristics such as the collection of data on SCC crack growth rates, information which is required when evaluating the integrity of structural components in plant equipment. Along with confirming the effectiveness of techniques such as removing the cold-worked layer, grain-boundary-character-controlled materials which are expected to inhibit SCC are also being developed. Development is also underway on using laser welding to achieve high quality and high efficiency welding, and the technique's effectiveness at improving SCC performance is being tested.
Preventive Maintenance Engineering Section,
Nuclear Plant Service Department, Hitachi-GE Nuclear Energy, Ltd.
stress corrosion cracking, laser welding, WJP, grain boundary character control, cold worked layer
