Can we not solve this problem by storing energy in the longer term?
It's true some 'burst' capacity is important, but can you not get a lot closer to 'average load' than the baseline by using the energy?
Pumping water into a reservoir at night, and getting the power back with a small hydro plant during the day comes to mind. We smooth out an even worse problem with wind and solar, which is spiky AND out of sync with demand sometimes. I believe flywheels are used to store energy in the short term sometimes. You did mention 'really big batteries', implying that we would need too many, but we aren't limited to chemical forms of energy storage.
I think this is a solved problem, or at least a fairly solvable problem, and nuke plants can provide not only the 'baseline' but close to the bulk average needs for power. We can decouple the power generation and the need for "something adjustable" and benefit.
Electricity demand during the night is about half of what it is during the day. If you were to have nuclear baseline production that covers peak consumption, you would have to find a way to store about 100000MWh of energy that gets produced during the night and then distribute that during the following day, or you would just waste it, somewhere, somehow.
(Disclaimer: Back-of-the-envelope math, I'm assuming the scale on that graph is in MW, it's only for the UK, not the US)
Yes, it's not an impossible problem. Yes, you can even out the peaks by changing behaviour. Yes, you could perhaps figure out a way to store and release that much energy each day.
But my point still stands, replacing fossil-based electricity production with nuclear is not trivial, it's a lot more complicated than summing up the total output of all fossil-based plants and dividing it by the average output of a new nuclear plant as DanielBMarkham argues.
I'm also a big fan of nuclear. Many countries would probably benefit from having their baseline production completely covered by nuclear plants. But how to deal with peak demand of electricity without fossil-based production and in an economically viable way, that is not a solved problem yet.
One of the reasons demand is light at night is that we run our central heating systems on gas -- mostly imported from Norway or parts east, these days. Per kWh, gas heating is a lot cheaper for the consumer. But if we had a serious base load nuclear infrastructure, we could provide much cheaper off-peak electricity for domestic heating, which would smooth out the demand curve significantly.
It's true some 'burst' capacity is important, but can you not get a lot closer to 'average load' than the baseline by using the energy? Pumping water into a reservoir at night, and getting the power back with a small hydro plant during the day comes to mind. We smooth out an even worse problem with wind and solar, which is spiky AND out of sync with demand sometimes. I believe flywheels are used to store energy in the short term sometimes. You did mention 'really big batteries', implying that we would need too many, but we aren't limited to chemical forms of energy storage.
I think this is a solved problem, or at least a fairly solvable problem, and nuke plants can provide not only the 'baseline' but close to the bulk average needs for power. We can decouple the power generation and the need for "something adjustable" and benefit.