Features of valves used for nuclear power plants and points to which attention should be paid in their selection

At present, Japanese nuclear power generation is ranked at fourth in the world, and achieved the world highest capacity factor of more than 70 %, and the valves for fluid control have contributed to that largely. In this report, the difference of the valves for nuclear power from those for petroleum, petrochemical and chemical plants is generally discussed. When working fluid contains radioactive substances, the leak of the fluid directly causes human body exposure and environmental contamination, therefore, particularly strict quality control is required for the design, manufacture, construction, operation and maintenance of such system for the purpose of heightening the reliability. The technology of the Japanese valves for nuclear power has been established by the improvement of safety and reliability through the operation experience and the verifying test, the institution of laws, regulations and standards, the development of the techniques for home production and so on. In the valves for LWR plants, the desigh pressure and temperature conditions are lower than those of modern thermal power plants, but the longer service life of up to 40 years is aimed at, considering earthquake load. The applied laws, regulations and guides, the materials of pressure-withstanding parts and gaskets, the design, the construction, quality assurance and others are explained. (Kako, I.)