[sebazzz]

Why can't nuclear not be turned on and off at will? I understand you can't just fire up and down a reactor, but you can control the steam flow to the generator, and let that redirect directly to the cooling tower at will?

The real problem appears to be buffer capacity.

[tomatocracy]

Turning on and off quickly is difficult and/or expensive for all of CCGT/OCGT gas, coal and nuclear. Turning up/down is much less so however, and in reality that's often how it works.