France’s Autorité de Sûreté Nucléaire (ASN) said on 3 April 2017 that solutions offered by EDF to resolve sealing issues at unit 5 of its Bugey NPP were appropriate and would remedy faults at the reactor. Because of leaks in the reactor containment building’s steel inner lining, the 880MWe pressurised water reactor has been in cold shutdown since August 2015 as EDF was unable to find the source of the sealing problems. However, EDF said in March that it was employing new techniques, hoping to restart Bugey 5, using a “sealing composite” and lime mortar. ASN said it had authorised EDF to apply the proposed solutions, which the agency will test. Restart of the reactor is subject to ASN’s final approval.

In November 2016 ASN extended the deadline for checks on Bugey 5. Significant leaks from the containment were first seen during a pressure test carried out in 2011 during the unit’s third 10-year inspection. In December 2014, ASN said new tests of the containment should be carried out during the reactor’s next shutdown, which was in August 2015. However, ASN said the tests showed there had been further degradation of the inner liner of the containment. Leaks were also found in the lower part of the reactor building. In April 2016 EDF submitted a safety case detailing proposals on how to deal with the issue. At the time ASN said the safety case was “technically complex” and was being reviewed by ASN and its technical support organisation, the Institute for Radiological Protection and Nuclear Safety (IRSN). Those reviews have now been completed. Bugey-5 began commercial operation in January 1980. The Bugey nuclear station has four commercial nuclear units.