Water chemistry of nuclear reactor systems. Current status and future scope of research and development

A special committee for water chemistry established under the Japan Atomic Energy Association has been studying the water chemistry of nuclear reactor cooling systems for the past four years. Some results of studies are outlined and problems remaining to be solved are described. The amount of accumulated radioactivity began to increase in some older BWRs several years after the start of their operation. To control this, various measures including water-chemical ones, were taken in each power plants. Prior to designing plans for exposure reduction, it is necessary to clarify the process of corrosion of materials for plant equipment and the behavior of corrosion products including migration and adsorption. Intergranular stress corrosion cracking of BWR primary piping is affected by the properties of material, stress and environmental corrosion. In Japan, this trouble is avoided by using improved materials and reducing the stress. For the PWR primary system, the concentrations of impurities as well as additives are controlled to reduce the risk of exposure. Various chemical and physical decontamination methods have also been introduced. (Nogami, K.)