These derogation requests were filed when 29 French reactors out of 56 are currently unavailable for various reasons. They come from the electricity producer EDF at the request of RTE, the high-voltage network manager, in order to guarantee the operation of the infrastructures.
According to a decree published this Sunday in the Official Journal, a temporary derogation from environmental rules has been granted to a fourth nuclear power plant, that of Bugey, in Ain, to allow it to continue to operate “at a minimum level of power” during heat wave.
“New thermal discharge limits” set temporarily
The decision of the Nuclear Safety Authority (ASN) of July 15 “setting, temporarily, new thermal discharge limits applicable to the reactors of the Bugey nuclear power plant, is approved”, according to the Official Journal.
“The reactors of the Bugey nuclear power plant discharging effluents into the Rhône may, during the fixed period (…), continue to discharge these as long as the heating after mixing of the effluents into the Rhône (…) does not does not exceed 3°C in average daily value”, specifies the decree of this Sunday.
On Friday, a derogation had been granted to the nuclear power plants of Golfech (Tarn-et-Garonne), Blayais (Gironde) and Saint-Alban (Isère). For these three plants and that of Bugey, the authorization was granted until July 24th.
Only one request, in 2018
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 derogation device, which aims to guarantee the proper functioning of the electricity network, had so far only been used once, in 2018 for the Golfech plant, for 36 hours. With early heat this year, EDF has already had to reduce the power of a reactor for a few hours in May at Blayais, then in June at 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.