France’s Autorité de Sûreté Nucléaire (ASN) said on 22 November that it has extended the deadline for checks to be carried out by Electricite de France (EDF) on unit 5 of the Bugey, and 880MWe pressurised water reactor. ASN said the deadline extension had no safety implications and the unit remains in cold shutdown. The checks include pressure and leak tests of the safety containment. The tests have been delayed because EDF detected a leak during an earlier test and needed to repair it before any further testing. EDF also needed to add equipment to prevent the containment from rupturing or breaking in the event of the failure of thermal insulation on a primary motor pump. Modifications need to be carried out on the containment’s passive equipment, valves and pipe supports, ASN said.

In December 2015, ASN asked EDF to submit details of work it planned to carry out to resolve defects in the inner, metallic liner of the Bugey-5 reactor containment building. ASN said EDF must provide the information before restarting the reactor. Significant leaks from the containment were seen during a pressure test carried out in 2011 during the unit’s third 10-yearly inspection. In December 2014, ASN said new tests of the containment should be carried out during the reactor’s next shutdown. EDF carried out these tests during a shutdown for preventive maintenance and fuel loading which began on 27 August 2015.

ASN said these showed further degradation of the containment inner liner   since the previous tests. Leaks were also found in the lower part of the reactor building. ASN said EDF submitted on 7 April 2016 a safety case detailing proposals on how to deal with the containment issue. The safety case is “technically complex” and is being reviewed by ASN and its technical support organisation, the Institute for Radiological Protection and Nuclear Safety. Bugey-5 began commercial operation in January 1980.