6 Dec (NucNet): France’s nuclear regulator, Autorité de Sûreté Nucléaire (ASN), has approved the conditional restart of 10 nuclear reactors in France that have been offline while the safety case for the units has been under review.
ASN said in a statement on 5 December 2016 that together with its technical support organisation, the Institute for Radiological Protection and Nuclear Safety (IRSN), it had reviewed information provided by nuclear operator EDF concerning reactors whose lower heads on the primary side of steam generators were manufactured by Japan Casting and Forging Corporation (JCFC).
The reactors concerned are ten 900-MW and two 1,450-MW units. ASN said EDF can restart the ten 900-MW units once the safety case has been confirmed by a programme of further tests. Each reactor restart will still be subject to ASN’s agreement.
In 2015 ASN asked EDF to look for components in its operating reactors that could be affected by an abnormality in the carbon concentration of steel used in the units’ steam generators.
ASN also asked EDF to carry out similar checks on two 1,450-MW units, Civaux-1 and -2, southeast of Poitiers in central France. According to ASN, EDF is still to present its safety case for these units.
The ten units that can now be restarted are: Bugey-4, Dampierre-3, Fessenheim-1, Gravelines-2 and -4, Saint-Laurent B1, and Tricastin-1, -2, -3 and -4.
The issue first came to attention in April 2015 when ASN confirmed an anomaly in the composition of steel in some areas of the lid and the bottom of the reactor pressure vessel at the EPR under construction in Flamanville, northern France. ASN said this could affect the mechanical properties of the steel and jeopardise the safety of reactors.
The discovery led ASN to ask reactor manufacturer Areva and operator EDF to check other EDF reactor components for similar anomalies. EDF subsequently identified similar anomalies on the lower, primary side cap of a number of steam generators, including those at the 10 reactors that have now been cleared for restart.
Areva discovered separately that steel from its Le Creusot forge facility in France and JCFC might have had carbon concentrations that could lead to anomalies similar to the one at Flamanville-3