You would think that a higher intake temperature would make the system run a little more efficiently. The intake water is turned into steam to run the turbines to generate electricity. It is going to become super-heated water anyway. I find it hard to believe that anything in the intake piping is going to get damaged when the water is several degrees warmer.
I can see how the river water might be too warm already to accept the outflow water.
A powerplant is a “heat engine”, and works due to the temperature difference between the reactor-generated steam and the condenser, which last is what the river water is cooling. Greater delta-T is “good”, so a higher condenser temperature means lower output/efficiency.
The water that is turned to steam is in a closed loop. The river intake water, used for cooling the condenser downstream of the steam turbine, is completely separate.
As Freedom Poster says, the river water is NEVER part of the heat generation cycle. The river/cooling water is part of a separate loop that carries the “no longer useful” (latent heat at discharge pressure) heat away so the working fluid can condense.
Apparently, the problem is mainly that the plant is not allowed to discharge water into the river at more than 90 degrees, even though the water the plant is drawing from the river is 92+ degrees.
Don’t you just LOVE bureaucrats