I used to work at UC Berkeley, and one of the buildings on campus previously held a research nuclear reactor (https://en.wikipedia.org/wiki/Berkeley_Research_Reactor). There's a sign there now "Nuclear Free Zone"; (https://www.dailycal.org/archives/the-berkeley-nuclear-free-...).

Note that they did have to do extensive decontamination on Gilman Hall (https://en.wikipedia.org/wiki/Formerly_Utilized_Sites_Remedi...) where plutonium was first isolated.