That's why it's for baseline power. No one is claiming it handles spikes. We have solutions for that though. Solar and wind also obviously don't handle spikes. Many types of batteries do, and they don't care where the power came from.

Rotational energy is actually a pretty good battery, which has no conversion cost with nuclear, since rotational energy is what it produces with the turbine. You spin your flywheel up, and you drain power from it as you need it. Chemical batteries also work, with the conversation cost that all sources pay equally.