1) If humans are trying to bootstrap they are going to spend time investigating lots of sites from our society. That’s going to include the ones that had radioactive material. People run into this problem even today when they should know better.
2) While most of the radioactivity today is being released by things like the residual radioactive material in coal, that’s partially due to a lack of catastrophic events. We’re doing a pretty good job keeping most of the severely radioactive material contained for now. But if there were little or no maintenance, it wouldn’t take much (a few earthquakes or fires) to let loose a lot of radioactive material. Look at what happened at Chernobyl and then keep in mind that only a small fraction of the total radioactive material was released and that almost all that material existed prior to the accident itself. There are around 400 nuclear power plants in the world right now. It doesn’t take many of those to have worse than Chernobyl results to make things unpleasant.
1) If humans are trying to bootstrap they are going to spend time investigating lots of sites from our society. That’s going to include the ones that had radioactive material. People run into this problem even today when they should know better.
2) While most of the radioactivity today is being released by things like the residual radioactive material in coal, that’s partially due to a lack of catastrophic events. We’re doing a pretty good job keeping most of the severely radioactive material contained for now. But if there were little or no maintenance, it wouldn’t take much (a few earthquakes or fires) to let loose a lot of radioactive material. Look at what happened at Chernobyl and then keep in mind that only a small fraction of the total radioactive material was released and that almost all that material existed prior to the accident itself. There are around 400 nuclear power plants in the world right now. It doesn’t take many of those to have worse than Chernobyl results to make things unpleasant.
I think we’d have to get down to brass tacks and look at real projections because I still seriously doubt it could be an existential threat.