INES-event
INES 1

Underdimensioned rupture disc installed in the FILTRA-system

System 361 (FILTRA) provides a filtered pressure relief for the reactor containment in the event of its failure (pressure increase). System 361 is activated via a rupture disc V1 which should rupture at a differential pressure of 5.08 - 5.4 bar across the disc. During the refuelling outage it is possible to replace the rupture disc. After replacement during the outage in 2001, the rupture disc was tested and failed at 3.36 bar instead of as expected at a pressure of at least 5.08 - 5.4 bar. The reason was found to be that the wrong rupture disc had been installed during the outage in 2000. This means that pressure relief of the reactor containment (barrier) would have occurred at a pressure lower than calculated in the event of failure. The safety consequences are judged in this case to be insignificant since the specified suction pressure margins (NPSH) for residual heating and emergency cooling pumps would have been maintained. There would not either have been any unacceptable pressure transients in the reactor containment. The possible impact on the environment is judged to be small.

Location: BARSEBECK-2
Event date: Thu, 19-07-2001
Nuclear event report
Legenda & explanation