Nuclear production in France to be impacted by high Rhone river temperatures

High water temperatures are expected to affect electricity production on the Rhone river in eastern France from June 25, particularly at the 3.6 GW Bugey nuclear plant. The 3.6 GW Cruas and 2.6 GW Saint-Alban nuclear plants, located downstream, were not mentioned in the bulletin.

Electricité de France (EDF), France's state-owned utility, has announced that it may need to reduce nuclear output along the Rhone River due to the ongoing heat wave. The high temperatures are expected to impact the cooling systems of several nuclear plants, particularly the 3.6 GW Bugey plant, from June 25 onwards [1].

The heat wave, coupled with a lack of rainfall, is causing the Rhone River's water temperature to rise. This increase in temperature, combined with low water flows, poses a significant challenge to the cooling systems of nuclear reactors that discharge their water directly into the river. EDF has stated that it will review the situation on June 24 and provide a detailed update if production cuts are confirmed [2].

The Bugey plant, located in the Ain department, is particularly vulnerable due to its direct discharge into the Rhone. The plant's thermal limits are set at a maximum temperature of 26°C downstream and a maximum temperature difference of 5°C between upstream and downstream. If the grid operator RTE determines that the plant is necessary to maintain supply, these limits can be increased to 27°C with a 1°C temperature difference allowed [2].

The 3.6 GW Cruas and 2.6 GW Saint-Alban nuclear plants, located downstream from Bugey, are also potentially affected by the rising temperatures and low flows in the Rhone River. However, EDF has not yet mentioned specific production cuts for these plants [1].

EDF has the option to request waivers from regulators if France's security of supply is threatened. The utility is closely monitoring the situation and will provide updates as the forecast evolves [2].

References:
[1] https://www.bloomberg.com/news/articles/2025-06-19/edf-may-curb-french-nuclear-output-from-june-25-due-to-heat-wave
[2] https://www.argusmedia.com/zh/news-and-insights/latest-market-news/2701047-french-bugey-nuclear-cuts-likely-from-25-june-edf