No that's never the problem, even 40°C intake is cool enough to cool a reactor, it's all just a question of returned water temperature that can be harmful to a river if too high (generally the limit in Europe is set to 30°C).
No that's never the problem, even 40°C intake is cool enough to cool a reactor, it's all just a question of returned water temperature that can be harmful to a river if too high (generally the limit in Europe is set to 30°C).
It can vary by the river too (e.g. I remember Switzerland pulling back a reactor around 25 intake), and iirc there’s an absolute limit on the outflow (you don’t want to boil alive the stuff just off of the plant) and a relative one a bit downstream (you can’t heat the river to 20 when it’s freezing).
These heatwaves reduce the margin from both directions, a hotter intake means you have less margin on the outflow, and the lower flow rate means there’s less water to dilute that outflow. And apparently for that specific plant there’s also the water level not even reaching the intake.
As long as it’s designed for those temperatures everything is fine, but efficiency still suffers.