But unused capacity in nuclear overspeeds the turbines, you can't allow that to happen -- generation and frequency are both controlled by the same steam valve. Unused capacity in solar just sits there basking in the sun. The frequency is controlled by software in an inverter.

To make solar demand-responsive, you just build more of it. It's really that simple.

Renewables look at nuclear's inability to deal with the fluctuations and respond "That's a 'you' problem, not a 'me' problem."

The issue is not primarily technical, it's economic. Operate a nuclear plant at lower capacity factor and the economics becomes even more hopeless.

The main issue is that the largest cost of a nuclear power plant is the capital investment to build it and staff to run it, which is fixed. In comparison fuel costs seem to hover at about 25%. Therefore you need to run your plant at about full power all day to have a chance to recoup the investment. With renewable, although intermittent, sources vastly undercutting nuclear energy on price many hours of the day this becomes an almost impossible calculation.

Based on this nuclear is an uniquely bad pairing together with renewables, and it will only get worse. Say you can make massive profits on average one hour per day, but that means all other methods of energy generation or storage can make the same, and still undercut you.

This isn't even factoring in that it is impossible to get insurance for a nuclear power plant.

A glass log at the ocean floor costs no one anything.

Let's be honest here--nuclear is not "ideal" for baseload, and it is indeed inflexible w.r.t. power output. What's actually ideal for baseload are fossil fuels. Unfortunately, those aren't going to be an option going forward, so we have to choose between a number of less-than-ideal options. I think it would be better to be realistic about the tradeoffs of those options than to try to argue that we actually aren't giving anything up.