At least 15 nuclear reactors have been temporarily shut down or had their power output curtailed across Europe due to severe heatwaves and critically low river levels during June and July. While no plants have been directly closed by wildfires, the Sizewell B nuclear power station in the UK has been placed on “high alert” due to a major 100-acre wildfire burning just four miles away.
The vast majority of disruptions have occurred in France, where state-owned EDF is legally bound to close reactors or reduce power to prevent discharged cooling water from pushing river temperatures past environmental thresholds. Switzerland’s Beznau NPP has also been impacted. A record-breaking drought has caused the Danube River to drop to historic lows affecting NPPs in Hungary, Romania and Bulgaria resulting in the imminent full closure of the Paks NPP in Hungary and the possible closure of Romania’s Cernavodă NPP.
As of 3 August, there are six nuclear units closed across Europe and 17 units facing restrictions. In France, unit 3 at the Bugey NPP on the Rhône River closed on 9 July and unit 2 at the Golfech NPP was fully shut down on 30 July as Garonne river temperatures surged. Units facing restriction on output include Bugey 4&5, Saint-Alban 1&2 (Rhône River), Blayais 1&3 (Gironde Estuary), Nogent-sur-Seine 1&2 (Seine River), Chooz 2 (Meuse River), and all four units at Tricastin (Canal de Donzère-Mondragon/Rhône).
Output at Switzerland’s Beznau NPP on the Aare River (units 1&2) is also curtailed. Both reactors were taken completely off the grid on 26 June when the Aare River first spiked to the 25°C threshold and remained offline for several weeks. They are currently capped at roughly 50% of normal generation capacity to limit environmental thermal pollution.
The situation for NPPs on the Danube River is critical. In Hungary, three of the four units are now offline with the fourth expected to close shortly. Unit 3 closed on 29 July, unit, unit 1 was closed on 1 August and unit 4 on 2 August with the closure of unit 2 imminent. on throttled, and the entire 2 GWe plant’s overall output has fluctuated to near 10% capacity with a complete shutdown imminent because the Danube has dropped below intake pump levels. The river has collapsed to less than one-third of its normal seasonal flow.
Hungary’s mitigation efforts focus heavily on emergency energy rationing, massive electricity imports, and alternative transport rules to protect the grid from the near-total loss of the Paks NPP.
All heavy rail cargo transport across Hungary is strictly banned between 5:00 PM and 10:00 PM. Budapest has turned off decorative and architectural lighting for major landmarks. Citizens are under strict instructions to voluntarily limit the use of high-draw appliances like air conditioning and washing machines during peak hours. Nearly 300 major corporations have voluntarily slashed production to avoid forced power cuts. The government has established a rolling grid-disconnection protocol for heavy manufacturing factories if voluntary caps fail to stabilise the network.
State grid operator Mavir previously used temporary legal waivers allowing Paks to discharge hotter wastewater into the Danube. However, with the river physically too shallow for the suction nozzles, this mitigation is no longer effective. To decouple the national grid from the Danube River, the government announced a plan to use private capital and EU funding to fast-track 4 GWe of wind energy capacity by 2030.
In Romania, unit 1 at the Cernavodă NPP was closed on 28 July and unit 2 is fluctuating under critical, hour-by-hour output restrictions. Unit 2 is operating at restricted, approximate half-capacity. If emergency measures fail, authorities warn the entire plant must be completely shut down by 6 August at the latest.
The Romanian naval forces have deployed explosives in the Danube River near Izvoarele. By blasting apart massive rock formations and sandbars, they are successfully forcing a larger volume of water to divert toward the Cernavodă nuclear plant to keep its remaining active reactor cool. Romania is also building temporary dams and barriers in the riverbed to artificially raise water depth right at the plant’s suction nozzles. Romania’s government has declared a nationwide state of alert in the energy sector and is appealing to citizens to voluntarily limit electricity usage during peak evening hours.
Bulgaria is also on the verge of a severe grid emergency, with the government warning that it may be forced to initiate a complete shutdown of its entire nuclear sector within days. Bulgarian Energy Minister Iva Petrova warned on 29 July 2026 that the country may be forced to temporarily shut down both of its operational units – units 5&6 at the Kozloduy NPP.
To prevent Kozloduy’s cooling systems from failing, the Bulgarian Energy Minister established direct contact with the Serbian Ministry of Mining and Energy. They are actively coordinating with the Djerdap 1 (Iron Gates) hydropower complex located upstream. Serbia is strategically releasing water through its dam system to help maintain the Danube’s level just above the critical operating thresholds required by Kozloduy.
Bulgaria has classified the current crisis as a force majeure event, noting that the river is continuing to drop by up to 2 centimetres every day. In response, the Kozloduy plant has deployed emergency “special measures”, including riverbed dredging and the preparation of secondary pumps to try and keep the intake channels clear enough to avert an immediate blackout.
The energy minister established direct contact with the Serbian Ministry of Mining & Energy. They are coordinating with the Djerdap 1 (Iron Gates) hydropower complex located upstream. Serbia is strategically releasing water through its dam system to help maintain the Danube’s level just above the critical operating thresholds required by Kozloduy.
Unfortunately, significant river and hydrological relief is not expected anytime soon, with meteorologists and grid experts projecting that low river levels will continue to threaten European nuclear plant operations until at least mid-August. Longer-term weather models suggest that substantial rainfall may not arrive until late autumn.
