Radiation emergencies are likely to be caused either by a release from a nuclear powerplant, or from a nuclear weapon.
Both produce large amounts of RAI, and both can threaten people located from tens to hundreds of miles downwind. We know this because it has already happened.
There are nearly 100 operating nuclear power reactors in the US producing about a quarter of the country’s electric energy. The plants are vital for the country’s energy needs, but they are not without risk.
The US Nuclear Regulatory Commission (NRC) reports that in a serious powerplant accident, “much of the radioactive plume will be deposited on the ground within about 50 miles” of the release.13 This is what took place at Chernobyl, with the NRC reporting “the vast majority of the thyroid cancers were diagnosed among those living more than 50 km (31 miles) from the accident site.”14 In fact, as this report shows, 17% of the cancers took place more than 200 miles downwind.
Obviously, a similar accident in the US would threaten millions of people, and all will want KI.