During normal operation at 500 MWe power a blowhole in the flange connection of reactor coolant pump (RCP) and its auxiliary pipeline was discovered. Leak rate did not exceed 6 m3/h. According to operating procedure the unit was shut down using reactor scram button (AZ-5).
Breach of unit safe operation limits and conditions did not occur. Radiation situation in the reactor building and on site was within prescribed limits.
Water leakage was caused by defect in the flange connection between the auxiliary pipeline and the pump casing.
BASIS FOR RATING: Initiator - reactor coolant system leakage that would not prevent a controlled reactor shutdown and cooldown.
Event - real, expected.
Safety function availability - full, which corresponds to level 0/1 (A-1R) in Table 2 or level 0 in Table A2. Preliminary rating - level 0.
DIFFICULTIES IN RATING:
Event date: Thu, 21-02-1991