Heatwave in France forces Golfech reactor shutdown and output cuts at other nuclear plants

Golfech shutdown

A major heatwave in France has forced EDF to shut reactor 2 at the Golfech nuclear plant after the Garonne river became too warm for normal cooling operations.

EDF said the shutdown is driven by environmental rules on river temperature, not by a nuclear safety problem. The company has said the unit is scheduled to stay offline until midnight on Tuesday, June 30, although the timing could change if weather forecasts shift.

Golfech reactor 1 has already been offline since May for routine maintenance and refueling, leaving the plant more exposed to the heatwave-driven restriction on reactor 2.

More plants affected

The disruption has not been limited to Golfech. Le Monde reported that output at reactor 2 at Nogent-sur-Seine was reduced from 1,300 megawatts to 400 megawatts starting June 23, and that reactor 3 at Bugey was scheduled to be cut from 900 megawatts to 180 megawatts starting June 24.

EDF also warned that Blayais and Saint-Alban could face reductions starting June 24 and June 25 respectively if river temperatures stay high.

Taken together, the affected cuts amount to about 4.6% of France’s installed nuclear capacity, according to Le Monde.

Grid outlook

RTE, France’s grid operator, has said the system has enough generation capacity to meet demand even if more facilities are curtailed in the coming days. It said peak demand reached 57 gigawatts on June 23, with nuclear and solar providing most of the electricity at that point.

That reassurance is central to the public-interest question around the story: whether climate-driven cooling limits at several plants could threaten supply reliability. For now, RTE says the answer is no.

Why the cuts matter

France’s nuclear fleet is unusually exposed to heat because several reactors depend on river water for cooling. When river temperatures rise, operators can be forced to reduce output or stop reactors to comply with environmental limits that protect waterways.

At Golfech, the relevant rule can require reactors to reduce output or shut down when the Garonne downstream of the plant exceeds 28 C on average daily temperature. Le Monde reported that EDF has not requested any exemption for 2026 so far.

The event underscores a growing tradeoff in extreme weather: keeping the power system stable while also limiting thermal stress on rivers and other ecosystems.

What comes next

The immediate questions are whether EDF extends the Golfech outage beyond June 30, whether the planned cuts at Blayais and Saint-Alban are actually implemented, and whether EDF seeks any special exemption from the regulator, ASN.

For now, the confirmed picture is one of a strained but functioning grid, with France’s heatwave forcing temporary nuclear output reductions rather than triggering a supply emergency.