On the modification in reactor facilities of Tsuruga Nuclear Power Station, Japan Atomic Power Co., Ltd

This is the report submitted by the chairman of Atomic Energy Commission of Japan to the prime minister, dated June 1, 1976, in which the application of permission on the subject is approved to be in conformity with the criteria for permission in the related laws. The modification to be investigated is the new installation of a steam generator for turbine shaft sealing in which the steam produced by heating condensate tank water with the generator is used as low pressure, turbine shaft sealing steam (before the modification, the steam generated in the reactor is used). Its purpose is the reduction of radioactive substances in exhausted gas in normal operation, and the reactor safety is not impaired by the modification. Evaluation of exposure dose was performed in the circumference of the reactor facilities, due to the radioactive substance released in normal operating condition. The result showed that the released rate of rare gases and iodine was reduced to approximately 1/3.5 of the value so far. From this result, the maximum gamma exposure dose of a human whole body due to radioactive rare gases is estimated as 1.8 mrem a year in possible inhabitable locations, and the maximum thyroid gland exposure dose due to radioactive iodine is 1.6 mrem (infant). These are well below the objective values specified in the guide for the target values of dose in the facilities of light water reactors for power generation. (Wakatsuki, Y.)