Reactor discharge due to deterioration of quality of water in the secondary circuit (power reduction)
Tuesday, September 8, 1998
One June 4, 1998 the plant was under 160 MW electrical power operation. At 10.40 a.m. the shift supervisor received an information concerning high level of content of Na in the samples of blow-down lines of SG-16. In the SG3 and SG6 the content of Na exceeded the level established by L&C (2,3mg/kg and 2,1mg/kg instead of permissible 1,5mg/kg). Operational personnel discharged the reactor power down to 80 MWe. At 14.45 were detected and closed two sources of penetration of Na in the secondary circuit. After the reestablishing of the parameters of water the operational personnel increased the reactor power up to 160 MWe. The event caused neither on-site nor off-site radiation impact. Basic rating: Defense in depth criteria: Level 1- Anomaly beyond the authorized operating regime. Upgrading: Safety culture. Additional factor was taken into account according to chapter III-5.3 of the INES manual, namely, the repetition of the event indicated that the previous event lessons have not been learned. The final rating was selected as level 2.