Method of operating BWR type reactors

Purpose: To mitigate or prevent stress corrosion cracks resulted in primary coolant circuits. Method: Prior to the initial charging of nuclear fuels after installation or repair of a reactor, a source for pure water containing no dissolved impurity gases and a source for inert gases are connected to a recycling system pipeway and a heater is provisionally attached to a part of the recycling system pipeways. Thereafter, the inside of the pressure vessel and the primary coolant circuit communicated therewith are entirely evacuated by a vacuum pump and pure water and inert gas are introduced in the pressure vessel and the primary coolant circuit pipeway. After confirming the pressure-proofness of the system, the pure water is heated by the heater near an ordinary operation temperature and pressurized. Then, the pure water in the pressure vessel is recycled to clean up the system in the same flowing state as that in nuclear heating. This produces dynamic distortions as occur in the first time heating, whereby stress corrosion cracks which would otherwise be accelerated can be moderated and prevented. (Furukawa, Y.)