I think I've played 3 different ones.

1. One I bought on steam in alpha, which was a generous way of describing "we've managed to get it to compile, now pls give money",

2. another was something online that I can't find anymore

3. and lastly there's the one I've actually spent some time with which was the low defunct nuclearpowersimulatorDOTcom. Luckily it's still playable on the waybackmachine https://web.archive.org/web/20200221074957/http://www.nuclearpowersimulator.com/