Where are Radioactive Isotopes found?

[supernova1203]

Radioactive isotopes or radioisotopes are they only found in nuclear reactors? Or can they be found in the natural world as well?

 

[daveb]

They're all around us, which is why we get an average of about 360 mrem per year exposure (most of it from radon).

Princeton has a great site about radiation and radiation protection.
http://web.princeton.edu/sites/ehs/osradtraining/backgroundradiation/background.htm"

 

[NascentOxygen]

Geiger counters click sporadically anywhere, even when you just wave them around in the air. Though, admittedly, it's impossible to demonstrate that the GC is not sensing material that has leaked from reactors, if that is what OP is implying.

Marie Curie died of cancer attributed to radioactivity, that was well before our first nuclear power station. Her premature death is not surprising, in light of what we know today, for she had a pile of ore stacked outside her home from which she extracted the chemical she was investigating.