Uranium is still there, it’s just sub-critical mass so the reaction isn’t happening. Uranium 235 (which would have powered the reaction) has a half life of ~700 million years. So there’s still probably a good bit of it there - the reaction is thought to have stopped about 1.7 billion years ago.
Well do I have news for you
https://en.m.wikipedia.org/wiki/Natural_nuclear_fission_reactor
Well but they’re not around anymore because the uranium inside them is all consumed by now, right?
Uranium is still there, it’s just sub-critical mass so the reaction isn’t happening. Uranium 235 (which would have powered the reaction) has a half life of ~700 million years. So there’s still probably a good bit of it there - the reaction is thought to have stopped about 1.7 billion years ago.
that makes sense, yeah