Risk of recirculation system valves becoming jammed in emergency core cooling system and containment spray system in Belleville, Cattenom, Golfech, Nogent and Penly NPPs.
On 27 April 2001, the French Nuclear Safety Authority decided to re-rate at INES level 2 a generic event notified by EDF on 12 March 2001. This event consists of an anomaly which could lead to a risk of recirculation system valves becoming jammed in the 12 1300 Mwe reactors at Belleville, Cattenom, Golfech, Nogent and Penly NPPs. This event was provisionally rated at INES level 1. The recirculation system is necessary, in case of significant leakage from the primary system, to recover, after the initial water stock is empty, the water from the leak which has accumulated in the sump of the containment building, and send it back to emergency core cooling system (RIS) and containment spray system (EAS) so as to ensure that the reactor is cooled.
The design of these valves, contrary to those in other French nuclear power plants, shows an insufficient room for cool water in normal conditions, which would prevent thermal expansion and then risk of valve locking.
Event date: Mon, 12-03-2001