Nuclear powerOperations in French Nuclear Power Plant Suspended after Monday Tremor

Following a strong earthquake Monday in the Drôme and Ardèche regions in south-east France, EDF (Électricité de France), has ordered the suspension of power production at the Cruas-Meysse power station.

The magnitude 5.4 earthquake shook the area at 11:52 a.m. Monday. The French Central Seismological Office (BCSF) said the epicenter was about twelve miles from the outskirts of the town of Montélimar, located about 35 km from the nuclear power station.

Le Figaro reports that the tremor, highly unusual for the area of France, was felt as far as cities of Saint-Etienne and Lyon in east France, and Montpellier to the south.

Many houses in the town of Montelimar collapsed, and the old church of Saint-Etienne de Melas, built in the ninth century, was damaged, with the church’s steeple threatening to fall.

The epicenter of the earthquake was 23 kilometers from the Cruas-Meysse nuclear power station, located in the Ardèche region, and 26 kilometers from the Tricastin site, locate in the neighboring region of Drôme.

The Tricastin site includes a nuclear power plant. Nuclear fuel production and treatment factories are located in nearby Orano.

Figaro says that EDF on Monday decided to suspend all operations three of the four reactors of the Cruas-Meysse nuclear power plant for at least twenty-four hours, in order “to carry out complementary and preventive controls.” The fourth reactor on the site was already shut down for regular maintenance.

EDF noted that “The first checks did not show any apparent damage. However, vibrations have been recorded, which requires additional and preventive controls.”

France’s nuclear power regulator ASN (Autorité de sûreté nucléaire) reported that “no apparent damage” was noted, but that the intensity of tremor-related vibrations exceeded the thresholds which trigger automatic suspension and examination of the reactors.

Operations of the four reactors at the nuclear plant at Tricastin have not been stopped. Two years ago, the four reactors at the site were shut down for three months because of fears that a strong earthquake – defined as 5.2 magnitude or higher – would cause the collapse of the Canal du Rhône dam.

The dam has since been repaired and reinforced.

Figaro notes that Monday’s magnitude 5.4 earthquake was more powerful than the magnitude 5.2 level which was adopted by the ASN as a reference with required dam strength.

EDF said that “the seismic risk was taken into account from their design for all of our nuclear power plants, according to the history of earthquakes observed in the regions where our facilities are located.”

Experts note that of France’s nineteen active nuclear power plants, five plants, including four in the Rhone Valley, are located in seismically active zones. Among these plants are the two of the oldest plants in France — Fessenheim (Haut-Rhin) with two reactors, commissioned in 1977, and Bugey (Ain) with four reactors, commissioned 1978-1979). The other plants are: Tricastin (Drôme), four reactors (1980); Cruas-Meysse (Ardèche), four reactors (1984-1985); and Saint-Alban (Isère) with two reactors (1985-1986).