You have fourth generation “micro” reactors as small as a few megawatts:
https://oklo.com/newsroom/news-details/2023/Oklo-Tentatively-Selected-to-Provide-Clean-and-Resilient-Power-to-Eielson-Air-Force-Base/default.aspx
Or you can build gigantic ones where you might only new one or a few per state or anything in between. There’s no scientific limit in that regard. Just a societal choice.