Regulator Orders EDF To Shut Tricastin Reactors Over Flaws In Canal Dyke

29 Sep (NucNet): The French nuclear regulator, Autorité de Sûreté Nucléaire (ASN), has ordered state-controlled utility and nuclear operator EDF to temporarily shut down all four reactors at the Tricastin nuclear power station in the south of France following the discovery of flaws in a canal dyke bordering the facility. The request was made by ASN due to the Tricastin plant failing to pass certain safety tests involving above-average earthquakes for the region in the south of France. EDF said the shutdown will allow it to strengthen a small section of the dyke located to the north of the power plant bordering the Donzère-Mondragon canal. “As an operator that takes responsibility for the safety of its installations, EDF does not share the view that the four reactors need to be shut down for the duration of the work. EDF will nevertheless implement the ASN decision without undue delay,” said the company in a statement. According to EDF, geotechnical surveys carried out on the dyke in 2015 and 2016, supplementing those performed in 2013 and 2014, revealed that a small section of the dyke required reinforcement. However, EDF said it had demonstrated to ASN that the dyke is capable of withstanding an earthquake known as a “maximum historically probable earthquake”, or MHPE. This is an earthquake that is more severe than the historical earthquakes observed in the vicinity of the power plant, located in the most damaging position for the installations. EDF said that within one month, dyke strengthening work will be carried out to guarantee its resistance in a “safe shutdown earthquake” situation. Ahead of this strengthening work, additional protection is being installed on the existing peripheral protective wall and will be operational within a few days. This measure ensures that no water would reach the reactors in the event of a safe shutdown earthquake during the work period. EDF classified the incident as Level 1 on the International Atomic Energy Agency’s International Nuclear and Radiological Event Scale (INES). ASN later said it had reclassified the incident as a provisional Level 2. INES is an international scale used to classify the safety significance of nuclear and radiological events involving ionising radiation. Events are rated at seven levels, ranging from 1 (anomaly) to 7 (major accident). The Tricastin station has four pressurised water reactors that began commercial operation from 1980 to 1981.