The claim that external exposure to radiation does not make you radioactive is true in most cases. However, Chernobyl is not most cases. First, I'm not sure yo

The claim that external exposure to radiation does not make you radioactive is true in most cases. However, Chernobyl is not most cases. First, I'm not sure you can claim that people working during the disaster would only suffer external exposure. There was a reactor core on fire, there was probably plenty of isotopes in the air that would have been breathed in and possibly taken up by the body. Second, neither alpha, beta nor gamma reaction will induce any significant amount of radioactive in materials that are exposed to them. And under normal circumstances, that is all you would be exposed to. But this was, again, an exposed reactor core. There might very well have been a significant amount of neutron radiation present, which does in fact induce radioactivity. So the claims of the article are way too strong for this very, very exceptional situation.