If weather gets hot, the temperature of the incoming cooling water gets warmer, too. And having to operate within the limits of the maximum allowed temperature for the outgoing cooling water, the plant may have to regulate its power output, or maybe entirely pause operation.
The temperature limit is mostly a legal one: There is concern about the environmental effects of releasing warmer water to the water bodies. From an engineering point of view, the plant would probably be able to operate, and just release warmer water.
This isn't a game of Top Trumps where you need to find any one stat that's higher than your opponents to declare victory.
Nuclear has to be better than wind and solar and hydro and batteries and everything else (demand response, better insulation, undersea grid connectors etc.) all working together across a wide range of metrics to find a place in a modern grid.
It is failing at this. The alternatives are cheaper, better, greener, safer, quicker to build.
Narrowly focusing on one tiny aspect does not change this big picture reality.
The problem with what you're saying is that to supply peak power at all times could require building capacity in each method to supply full power, in case the others all fall to zero power. And even then, you hope that they don't all fall to zero, I guess.
Curtailment of nuclear power due to periods of extreme heat has had the effect of reducing European nuclear power output by approx. 0.1% since the year 2000. For France specifically, which with its many inland river-sited plants has been the worst hit country, the corresponding figure is approximately 0.15%
https://www.usnews.com/news/national-news/articles/2019-07-0....
> Now, increasingly, more frequent heat waves and hotter average temperatures are making those waters so warm that engineers are concerned that it can't do the job. Analysts say climate change is to blame.
> In little-noticed but publicly available reports to regulators, nuclear plant owners revealed that unusually hot temperatures last year forced them to reduce the plants' electricity output more than 30 times – most often in the summer, when demand from nuclear plants is at its highest. In 2012, such incidents occurred at least 60 times. At one plant in Connecticut a reactor was taken offline for nearly two weeks when temperatures in the Long Island Sound surged past 75 degrees.
It's not like you can just change the legislation to say "allow hotter discharge water" though -- the plants' very engineering criteria is being impacted. Warmer water has lower absorptive capacity to cool the primary loop so things get dicey when temps increase outside the design specification.
[0] https://www.theguardian.com/world/2003/aug/12/france.nuclear
Do you have a source for this?