Heatwave: EDF warns of possible reductions in electricity production in the nuclear fleet from Monday

EDF is getting ahead of the curve. The French electricity group has brought forward the start of possible production restrictions at its nuclear power plants, particularly at its Bugey power plant (Ain), to Monday instead of Wednesday , due to the possible impact of high temperatures on the Rhône River. "Due to forecast high temperatures on the Rhône River, production restrictions are likely to affect EDF's nuclear power plants from Monday, June 23, and particularly the Bugey site," EDF said in an information message on Saturday, June 21.

These forecasts will be refined "on day one," EDF said. The heatwave peaked in France on Saturday, hit by an early heatwave, which prompted Météo France to issue an orange alert starting Friday midday in 16 departments , mostly in the west of France. A very gradual return to cooler weather is expected in the west in the evening.

The operation of the power plants, which pump water from adjacent rivers (or from the sea, if necessary) to cool them before releasing it warmer, is regulated by temperature and flow thresholds for these waterways that must not be exceeded. These thresholds are specific to each power plant and are intended to protect flora and fauna. EDF warned Thursday that restrictions could be imposed starting Wednesday before bringing this date forward by two days.

For several years, in a context of global warming, droughts and heatwaves have led EDF, sometimes as early as June, to adjust its production to comply with these thermal discharge limits. Although losses are relatively low, the available power that can be mobilized can be significantly reduced during periods of extreme heat , according to a 2023 report by the Court of Auditors on the adaptation of the nuclear fleet to climate change.

According to the group, since 2000, nuclear production losses due to environmental causes (high temperatures and low river flow) have represented an average of 0.3% of the nuclear fleet's annual production. During the 2003 heatwave, production losses reached 1.43% of EDF's annual nuclear production. Simultaneous outages reached more than 6 GW, or nearly 10% of installed nuclear capacity, according to the Court of Auditors report.