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France: Numerous containment valves found open

Nuclear Monitor Issue: 

(January 24, 1997) Containment isolation valves were found open in at least a dozen cases in French nuclear reactors last year. The French nuclear regulatory agency DSIN has asked Electricité de France to determine the cause of the incidents and to propose measures to prevent a recurrence.

(465.4619) WISE Amsterdam -The incidents were collectively classified at Level 1 on the International Nuclear Event Scale (INIS). According to DSIN, the situation could have compromised containment integrity and core cooling in a primary pipe break, since it might have prevented emergency cooling water from reaching the needed systems. DSIN claims the incidents were of diverse origin, connected mainly with human error during maintenance or confusion between different equipment.

The first open valve was found at reactor number 4 at Bugey, and after tips to other reactors, more and more anomalies were found: in October at two reactors; in November at eight sites, totalling 11 reactors; and in December at tworeactors open valves were discovered. The anomaly at St. Alban was found to have existed since 1988 for unit 2, and since 1989 for unit 1!

However, EDF sees the open-valve episode as proof that the utility's policy of encouraging the plant staff to detect and correct anomalies, and share their experiences with other reactor sites, is working. Carlier, EDF vice-president for generation and transmission, noted that people are not always "totally reliable" and "in some ways are also tempted to circumvent the rules if they have not fully understood their necessity".

Source: Nucleonics Week, 12 & 19 December 1996
Contact: WISE-Paris