The Cooling Water

Only one reactor is still running at Cattenom. The French nuclear plant just across the border from Luxembourg had its first production unit taken offline over the weekend, not because of a mechanical fault or a safety drill, but because the Moselle River is too low to cool it.[1]

EDF, the plant's operator, confirmed the shutdown was a precautionary measure. When river levels drop below a certain threshold, the water is no longer cold enough or abundant enough to absorb the heat generated by a reactor. Continuing to run would risk raising the river temperature downstream to levels that could harm aquatic life and violate environmental regulations. So the reactor goes dark.

This is not a Cattenom-specific problem. Two more reactors at the Chooz plant in northern France, on the Meuse River near the Belgian border, were also disconnected for the same reason. The same heatwave that has parched the Moselle has parched the Meuse. The rivers that cool France's nuclear fleet, which supplies roughly 70% of the country's electricity, are running low.[2]

At Cattenom, reactors 2 and 4 are already offline for scheduled maintenance. With reactor 1 now shut down due to low water, only reactor 3 remains operational. Three out of four units, idle. In a summer where air conditioning demand spikes during heatwaves, the grid loses capacity at the exact moment demand peaks.

The irony is structural. Nuclear power is often promoted as a climate solution because it produces electricity without carbon emissions. But nuclear plants are thermal plants. They boil water to make steam to spin turbines, and then they need cold water to condense that steam back. When the climate crisis heats the rivers, the cooling system that makes nuclear power possible becomes the first thing to fail.

This summer has been a catalogue of heat-related disruption across the Greater Region. On Monday evening, more than 150 firefighters were called to Landscheid in the Tandel municipality after lightning struck a field and set around 1'000 hay bales on fire. The blaze stretched over 250 metres. The farmer estimated losses between 40'000 and 50'000 euros, six weeks of work gone up in smoke. The bales were meant to last until next year.[3]

Meanwhile, a team of fifteen Luxembourg firefighters just returned from Gironde in southwestern France, where they had been deployed to help fight one of the most devastating wildfires in the region's history. Approximately 42'000 hectares of forest burned. Over 220'000 people were evacuated. The team's mission chief described the scale as something none of them had ever seen, and noted that even after the main flames were controlled, the peaty soil keeps smouldering, reigniting without warning.[4]

The connection between these stories is water. Too little of it in the Moselle and the Meuse to keep reactors running. Too little of it in Gironde's forests to prevent combustion. And when it finally arrives, as a lightning bolt over a dry field in Landscheid, it does not bring relief. It brings fire.

Wednesday's weather forecast for Luxembourg offers a brief reprieve: no alerts, sunshine and clouds, a maximum of 28 degrees. After weeks of heatwaves and thunderstorms, that counts as plain sailing.[5]

But the Moselle is still low. The peat in Gironde is still smouldering. And the hay bales in Landscheid are still burning. A single calm day does not reset a summer like this one. The cooling water will return when the rain returns. The question is what happens between now and then.