Stichting Laka

Event Report Forms (ERFs) are filed to the IAEA. Sometimes there are multiple event reports, updating the rating, the event description. Here you only see the latest event report

ERF send date: Wed, 22-01-1992
ERF description: The unit was operating at nominal power. Spurious activation of fire extinguishing system occurred in one of the plant rooms. The water from the affected room penetrated to the lower room onto the Engineered Safety Feature Actuation System panels of Safety System (SS) train 1. This resulted in the actuation of SS train 1. In the course of the load sequencing that followed the valves on the discharge from the spray pump to containment room opened. The spray pump was tripped by control key. Alarm indication showed the open SG-1 pilot valve (PORV). After unsuccessful attempt to close this valve using control key RCP-1 was tripped and the unit power was reduced to 67% Nnom. Due to water spilling onto the ESFAS cabinets the DG-1 tripped and essential bus was deenergized. The reactor was then brought to subcritical condition using the PZ-1 (emergency protection) button.

BASIS FOR RATING: Initiator - expected, real (reactor trip). Safety function availability - within limits and conditions. According to Table A2 - level 1/2 (B-1R). The event reveals safety culture deficiencies (untimely testing of two remaining SS trains). Level 2 has been chosen.
DIFFICULTIES IN RATING: A common mode failure occurred in the safety systems. Untimely testing of the two remaining SS trains constitutes, according to TRV-1000 procedure, a breach of limiting conditions of operation. Therefore safety function availability could have been qualified as inadequate. According to Table A2 level 3 would have been assigned (D-1P).
ERF rating date: 01-01-1992
ERF contact person: Mr. V.I. Andreev
ERF address: Kitaisky Proezd 7, 103074 Moscow, Ukraine
ERF affiliation: Min. of Nuclear Power and Industry, of the USSR, Dept. of Principle, Accident Dispatch

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