 INES 2 |
TEMPERATURE TRANSIENT DURING START-UP |
During power raising the channel gas outlet temperature (CGO) on one channel exceeded the Operating Rule limit for a short period. At the outset of this period the need for corrective action was recognized and bulk rods were inserted at an increased but insufficient rate to terminate the temperature transient. The rate of insertion did, however, ensure that the temperature rise was controlled.
BASIS FOR RATING: 1) Real initiator: controlled power and temperature increase during start-up within the auto-reset rate of trip protection - frequency - expected.
2) Safety function challenged: Reactor Protection.
3) Relevant systems: a) Operator action based on indicated temperatures
b) fuel element temperature trip units.
4) Safety function availability: less than "within operational limits and conditions" but more than just adequate.
From Table A2 Box 1C INES rating is 2/3.
5) INES Level 2 chosen as the safety function availability was more than just adequate.
DIFFICULTIES IN RATING:
Event date: Sat, 15-06-1991
