nuh-uh. https://en.wikipedia.org/wiki/Load-following_power_plant#Nuc...
Modern nuclear plants with light water reactors are designed to have maneuvering capabilities in the 30-100% range with 5%/minute slope, up to 140 MW/minute.[7] Nuclear power plants in France and in Germany operate in load-following mode and so participate in the primary and secondary frequency control.
A nuclear plant is capital expensive, and it requires to be used as much as possible to be cost competitive.
You have to take whatever you can get for the power, even if it doesn't cover operating cost, to pay down the capital you spent building. When it becomes clear that you cannot bring in enough to pay for operations and debt service, you have no choice but to declare bankruptcy.
Of course, all this is foreseeable. So, you don't get the capital to build at all, because who wants to loan money that will predictably be defaulted on?