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 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