Relevantly, some nuclear plants are paired with hydro schemes, in order to make the flat output of nuclear plants economically match the bumpy daytime peak of consumer demand.
The reason why many nuclear plants are colocated with hydroelectric dams is that the dam is good source for cooling water in 3rd cooling loop and that it is good backup power source for black start of the nuclear plant. Ability of nuclear plant to scale its output power according to demand is usually significantly higher than of hydro.
