Method of reactor operation

Purpose: To surely prevent stress corrosion cracks in equipments of a reactor by always maintaining the oxygen density in primary coolants below a predetermined value from the start-up to the usual operation of the reactor. Method: In the case of re-starting a reactor after the shutdown thereof, primary coolants are circulated prior to nuclear heating and gases in a condensator is discharged to reduce the pressure for a certain period, whereby the dissolved oxygen density in the reactor water is lowered to about 200 ppb. Then, hydrogen is directly injected into the primary coolants during the period from the start of the nuclear heating till the temperature for the reactor water reaches 2000C. The injection amount for the hydrogen at the start-up is set within a range 2 - 5 times of the hydrogen injection amount required for controlling the oxygen density in the primary coolants to a predetermined value, thereby preventing the increase of the oxygen density in the reactor water during the above period. (Horiuchi, T.)