Look up SL-1 Reactor. It was a joint Army-Navy reactor that went prompt critical during maintenance. There was a steam explosion and a couple of guys died, and yes there was radiation leakage. When I went through the Navy's nuclear power school, we saw a movie about the reactor. At the time it was classified. I later (a few years ago) saw the same movie on some history type programing. They must have declassified the movie.