Flamanville reactor n°1: detection and stoppage of a leak on a reactor coolant system auxiliary line

On Thursday 25 October, ASN was informed by EDF that a leak had occurred on an auxiliary line of the reactor n°1 coolant system in the Flamanville NPP (Manche département) on 24 October 2012 at 23h15.

This reactor had been shut down for maintenance and refuelling since the end of July 2012 and was now entering the final restart phase: the reactor coolant system was operating at a pressure of more than 150 bar and a temperature of close to 300°C.

The leak occurred at re-pressurisation of the auxiliary line, as part of a maintenance operation.

The leak rate led the licensee to apply the reactor cold shutdown instructions, to ensure a rapid drop in water pressure and temperature.

The leak was contained in the reactor building for the entire duration of the event. It was stopped yesterday at 05h00 AM.

The EDF staff present during the operations evacuated the area and were not contaminated.

The event had no consequences for either the staff or the environment. The facility’s on-site emergency plan was not activated.

ASN’s Caen division carried out an inspection yesterday. For the time being, ASN is rating this event at level 1 on the INES scale.