Commercial nuclear plants are designed to handle baseload, because the marginal cost to a nuclear power plant of producing power is near-zero, so this is where

Commercial nuclear plants are designed to handle baseload, because the marginal cost to a nuclear power plant of producing power is near-zero, so this is where they have the biggest comparative advantage—or the smallest disadvantage, depending. The technology certainly can be used for peaker plants. But at grid scale? That would be an entirely novel design. I don't think any such plants exist outside of warships.