French regulator approves Tricastin restart

06 December 2017

EDF has received permission from France's Autorité de Sûreté Nucléaire (ASN) to restart three reactors at the Tricastin power plant after carrying out repairs to a canal embankment. The regulator ordered the temporary shutdown of Tricastin's reactors on 27 September because of the risks of failure of a 400 metre long portion of the embankment of the Donzére-Mondragon canal in the event of an earthquake.

Tricastin (Image: ASN)

Failure of the embankment in the event of an earthquake would have resulted in flooding, ASN said. As well as potentially causing a fuel melt accident in the plant's four reactors, such flooding would also have made deployment of on-site and off-site emergency management resources particularly difficult, the regulator said.

EDF conducted geotechnical surveys of the embankment before carrying out work to strengthen the portion concerned. The ASN said an assessment of the strengthened embankment, performed by France's Institute for Radiological Protection and Nuclear Safety (IRSN) at its request, "confirms that there would be no failure in the event of a safe shutdown earthquake, which is the largest earthquake studied in the nuclear safety case."

The assessment showed that, in certain conditions, there is a risk of localised landslips which would not compromise the stability of the embankment, but would require repair work subsequent to an earthquake. "EDF has therefore pre-positioned equipment in the vicinity of the embankment, in order to be able to carry out these necessary works to repair any landslips observed following an earthquake," the ASN said.

EDF has undertaken to implement enhanced monitoring of the embankment and intends to further strengthen the embankment so that it can withstand the extreme earthquake defined in the stress tests performed following the Fukushima Daiichi accident, the ASN said.

The ASN has now given its consent for Tricastin 2, 3 and 4 to restart. Unit 1 will remain shut down as EDF intends to carry out maintenance work on it, the regulator said.

The ASN said it had also on 23 October authorised the restart of Areva's Comurhex I uranium conversion facility, also located at Tricastin, after steps taken to reinforce the means of controlling chemical release if the embankment were to fail after an earthquake. "This restart means that the hazardous substances can be removed from the site with a view to final shutdown of the facility scheduled for the end of December 2017," it said.

Researched and written
by World Nuclear News