The request was filed on July 12 by the electricity producer at the request of RTE, the high-voltage network manager, in order to guarantee the operation of the infrastructures, while 29 out of 56 reactors are currently unavailable for various reasons.

The Nuclear Safety Authority (ASN) gave its agreement until July 24, and the Ministry of Energy Transition approved it on Friday, the two institutions said. A decree should appear on Saturday in the Official Journal.

Since 2006, each power plant has had its own regulatory water discharge temperature limits that must not be exceeded, so as not to overheat the surrounding waterways and to protect their fauna and flora. The power plants indeed pump water to cool the reactors, before rejecting it.

The regulations provide for possible temporary exemptions on certain sites, “if necessary for the proper functioning of the electricity network”, underlines EDF.

Against the backdrop of an intense heat wave, the request was made to ASN and the ministry for a period up to August 8, for the Golfech (Tarn-et-Garonne), Blayais (Gironde ) and Saint-Alban (Isère). The agreement was at this stage given until July 24th.

The ASN agreement aims to “allow the maintenance at a minimum level of power” of these three power stations, in order to “ensure the security of the electricity network”, explained the nuclear policeman on Friday.

The decision must “guarantee the proper functioning of the electricity network which requires the availability at all times of means of production capable of adjusting to the demand for electricity”, explains EDF.

On the other hand, “there is no risk concerning the electricity supply of the French”, assures RTE. And “it is not a question of safety. This exceptional device relates to the protection of the environment”, add the two organizations.

The derogation device has so far only been used once, in 2018 for the Golfech plant, for 36 hours.

“EDF’s proposals are acceptable in view of the feedback from environmental monitoring specifically carried out during previous heat waves as well as long-term monitoring of the ecosystems concerned”, estimated for its part the ASN. .

Its decision also prescribes “specific measures for enhanced monitoring of the aquatic environment, including fish life in particular”.

With early heat this year, EDF already had to reduce the power of a reactor for a few hours in May at Blayais. Ditto in June in Saint-Alban, on the banks of the Rhône.

The power plants most exposed to the risk of exceeding the thermal water discharge limits are Golfech, Le Blayais, and Bugey, Saint-Alban and Tricastin on the Rhône. Added to this is Chooz, in the Ardennes, due to a Franco-Belgian agreement on the flow of the Meuse, EDF had indicated in early July.

The group wants to put the consequences of these heat episodes on its nuclear production into perspective: since 2000, losses due to high temperature or low river flow have represented an average of 0.3% of the park’s annual production.

However, according to RTE, heat waves have already caused simultaneous unavailability of reactors reaching nearly 6 GW, or about 10% of installed capacity, and this problem is expected to increase in the coming years.