A significant safety event concerning faults in equipment needed for the operation of standby diesels at several of state-owned utility EDF’s 1,300 MW reactors in France has been rated as level 2 on the International Nuclear and Radiological Events Scale (INES) scale, which goes up to a maximum of 7.

Standby diesels provide redundant power for certain safety systems in the event of a loss of external power supplies. Because of the faults the operation of emergency diesels at the nuclear plants could no longer be guaranteed in the event of an earthquake leading to a loss of external power, regulator ASN said.

The faults included poorly fitting elastomeric pipe fittings, corrosion of portions of pipes or their supports, and electrical connection faults.