It doesn't make sense for backfilling the last 20%. That last 20% isn't steady, it's highly intermittent demand, something that nuclear is terrible at addressing.
If we can work out a good storage technology (and I am optimistic about this), then I totally agree. If we can't, then nuclear with demand-following load might be the best available option.
Using nuclear for the last 20% makes no sense. Against wind/solar, you either use nuclear for everything, or you use it for nothing. There is no middle ground (well, except maybe in a tightly tuned scenario where solar could just be cheaper for daytime peak reduction, but even that is a bit iffy.)
