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High French river temperatures expected to limit nuclear power output next week

Published by Global Banking & Finance Review

Posted on June 18, 2026

3 min read

· Last updated: June 18, 2026

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High French river temperatures expected to limit nuclear power output next week

By Forrest Crellin and Tristan Veyet

French Nuclear Power Output at Risk Amid Rising River Temperatures

EDF Issues Production Warnings

PARIS, June 18 (Reuters) - French state-owned utility EDF warned on Thursday that three nuclear plants face production curbs next week because of high temperatures on the Rhone and Garonne rivers as France grapples with its second heatwave this spring.

Nuclear output in France has been relatively consistent this year as production has continued to recover from lows hit several years ago, but exceptional heatwaves at the end of the northern hemisphere spring have raised water temperatures to levels that put reactors at risk of output curtailment.

Production Limits and Plant Locations

EDF, operator of the country's nuclear fleet, sometimes limits production when temperatures are near a threshold that varies depending on the nuclear plant, with shallower, slower rivers more at risk of facing disruptions.

It issued production warnings for the Golfech and Blayais nuclear plants on the Garonne river in the southwest, as well as the Bugey on the Rhone in the east. It also updated a warning it initially issued last Thursday, saying the Saint Alban plant on the Rhone was likely to be affected from June 23.

Heatwave Intensifies and Broader Impact

Temperature Thresholds at Other Plants

HEAT EXPECTED TO INTENSIFY NEXT WEEK

LSEG data showed that temperatures at the Cruas, Tricastin, Chooz and Nogent nuclear plants are also expected to get close to river temperature thresholds.

Forecasts and Demand Implications

Temperatures are expected to rise further next week, close to 8 degrees Celsius (46.4 degrees Fahrenheit) above seasonal norms in the low 30s on Monday, likely boosting demand for cooling, said analysts at Engie's EnergyScan.

Thermal Restrictions and Output

However, summer thermal restrictions are usually small, accounting for a fraction of a percent of annual output.

Price Impact and Market Effects

Temperature-driven curbs could add up to about €5 per megawatt-hour to prices on the affected days, but should not cause a structural seasonal increase, said AlphaValue analyst Pierre-Alexandre Ramondenc.

If insufficient volumes lead to forced shutdowns, however, this could prompt price swings of several tens of euros per megawatt-hour on intraday peaks and day-ahead prices, he added.

Other Factors Affecting Power Prices

Hydro Availability and Renewable Output

Hydro availability is also limited this year due to a lack of rainfall and snow in autumn and winter, which has lifted forward power prices.

The French spot price has been high too for the season recently, as hot temperatures have combined with low renewable output to raise prices. Market concern about continuing heat is reflected in the French front-month contract, which rose above €60/MWh in recent weeks.

(Reporting by Forrest Crellin and Tristan Veyet; Editing by Philippa Fletcher and Emelia Sithole-Matarise)

Key Takeaways

  • EDF warned of possible production restrictions at Golfech, Blayais, Bugey, and Saint‑Alban nuclear plants due to elevated river temperatures, with alerts spanning from next week.
  • Analysts expect river temperatures to run up to 8 °C above seasonal norms, increasing demand for cooling and likely adding up to €5/MWh on affected days—but not driving a structural price hike.
  • Hydropower remains constrained by low rainfall and snow, while subdued renewables output has already lifted French spot and front‑month prices above €60/MWh recently.

Frequently Asked Questions

Why is French nuclear power output being limited next week?
High river temperatures from ongoing heatwaves are forcing EDF to consider production curbs to prevent exceeding safety thresholds at several nuclear plants.
Which nuclear plants in France are affected by the production curbs?
Golfech and Blayais (on the Garonne), and Bugey and Saint Alban (on the Rhone), among others, are facing possible output limits due to high water temperatures.
How do high river temperatures affect nuclear power production?
Nuclear plants use river water for cooling; higher river temperatures can require output reductions to comply with environmental and safety regulations.
Will the production curbs impact electricity prices in France?
Analysts expect minor price increases due to thermal restrictions, but significant forced shutdowns may cause larger price swings in intraday and day-ahead markets.
Is this a recurring issue for France’s nuclear plants during heatwaves?
Yes, summer heatwaves often lead to small thermal restrictions, though this year's repeated heat events and low renewable output have intensified the impact.

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