You need a temperature difference, like a hot piece of radioactive material and cold water https://en.wikipedia.org/wiki/Second_law_of_thermodynamics

It’s always a problem of too much entropy.

Indeed, it's mentioned in the article: "The measure is an environmental protection requirement to avoid discharging too much hot water into rivers already warming from the heatwave."

France (and to a lesser extent large parts of europe) is currently suffering from an exceptional heat wave.

You kinda don’t want to kill the whole river ecosystem. We need a functioning environment

Correct, and they are discharging water because they cheapen out on not building cooling towers. So the issue is actually completely fixable, but it is a question if building cooling towers is cheaper than shutting down reactors for few weeks a year.

Their nuclear reactor goes away every night though.

I was sure this couldn't be true but I couldn't find anything about high temperatures shutting down solar plants.

But I did find something about a predicted grid overload during a sunny period requiring a solar plant to go offline:

https://www.theguardian.com/environment/2026/jul/12/solar-fa...

It does when it rains, or it's too cloudy, or it snows, or the panels are dirty. Or, y'know, nighttime.