Climate risks: French nuclear output threatened

An unseasonably warm May has led to high water temperatures in several rivers throughout France, putting some nuclear plants’ output at risk during a period of historically high unavailability, according to analysis by Refinitiv Eikon.

Spring heat records have also been broken in France this year, with parts of the south already exceeding 33 Celsius and some models predicting temperatures will rise locally to 37 Celsius or even 39 Celsius by the end of the week, around 17 Celsius hotter than the seasonal average.

River water is often used for cooling reactors before being returned at a higher temperature, with regulations are in place that limit reactor production during times of high heat to prevent the process from damaging local wildlife.

However, the recent heatwave in France could test these regulations: most rivers with power plants have an upper limit between 26 and 30 degrees Celsius for cooling.

The possibly exposed nuclear plants are the 1.8 gigawatt (GW) Bugey plant, the 2.6 GW Saint-Alban plant and the 3.6 GW Tricastin plant on the Rhone river in the south east, as well as the 3.6 GW Blayais plant on the Gironde river in the south west.

“The latest forecasts indicates that temperatures at Bugey and Tricastin will be below warning levels later this week, while Blayais will stay above warning levels and risk needing to down-regulate, if at nominal power,” said Refinitiv analyst Stefan Soderberg.

The current warning levels at the Blayais plant indicate that it is still lower than the maximum allowed temperature but above the level where supply reduction is needed to comply with regulations, he added.

The Blayais plant is operating at limited capacity, data from nuclear provider EDF  showed.

French nuclear supply stood at a much reduced 50% of available capacity on Wednesday (25 May), with a slew of reactors having gone offline in recent months owing to issues with corrosion found in the welding of reactor safety circuits

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