He didn't create a nuclear reactor, this is a common misconception. It even says this in the wikipedia article.
He basically got a bunch of radioactive stuff and put it together. He wasn't anywhere close to making a nuclear reactor let alone a nuclear weapon. For a weapon you need isotopes which he didn't have access to.
Of course. "tried to" being key words in the comment. If he had the help of Claude at the time, how much more dangerous would his bumbling have been?
A real nuclear engineer with the knowledge he needed would also have said "no, don't do that and I won't help you." We are programming the knowledge into the ai agent. Giving ai a little discretion makes sense too.
A bunch of radioactive stuff together is basically the definition of a nuclear reactor though. They even call it a natural nuclear reactor if uranium ore is in sufficient abundance in nature.
https://en.wikipedia.org/wiki/Natural_nuclear_fission_reacto...
I'm reminded of when my son, who was six at the time, came into the house and announced that he and the neighbor's boy, nine, were building a bomb, and that he needed to get some stuff from the pantry. When I investigated what exactly was going on, they were putting "hot" things like black pepper and Tabasco into a plastic bowl and were going to "set it off" with a match.
Thankfully, that complete failure seems to have been the end of either of their mad scientist careers, as they are now twenty and twenty-three, and both well-adjusted, peaceful members of the community.