Bugey 5 containment repairs get regulatory approval

The French nuclear safety authority has approved EDF's suggested solution to repairing the containment of unit 5 of its Bugey nuclear power plant in eastern France. The containment was found not to be airtight owing to a corroded seal.

Tests conducted in 2011 during the third decennial inspection of the 880 MWe pressurized water reactor identified a high leakage rate from the inner liner of its containment. In December 2014, Autorité de Sûreté Nucléaire (ASN) ordered more tests to be carried out during the unit's next maintenance and refuelling outage.

That outage began in August 2015 and Bugey 5 has remained offline since. Further tests indicated a degradation of the sealing metal coating of the inner liner since the tests conducted in 2011. The latest tests also helped locate the leaks at the bottom of the containment liner.

EDF informed ASN in November 2015 that it planned to make repairs to the unit's containment with a view to restarting the reactor. In April 2016, the utility submitted details of its investigation into the cause of the leaks and how it proposed to remedy them - by applying a composite coating around the base seal of the containment vessel and use a fluid "protective" lime mortar.

ASN has now analysed EDF's proposals, in consultation with the France's Institute for Radiological Protection and Nuclear Safety. On 29 March the regulator informed EDF that it found its solution "appropriate" and said it will monitor EDF's implementation of the repairs. It has also requested the utility conduct another leak test once the repairs have been made to demonstrate the effectiveness of the containment has been restored.

EDF will then need permission from ASN to restart the reactor.

Researched and written
by World Nuclear News