Fukishima was (maybe) unusual though in that the nuclear accident was in the context of a much larger disaster. The original Japanese advice to stay put and tu

Fukishima was (maybe) unusual though in that the nuclear accident was in the context of a much larger disaster. The original Japanese advice to stay put and turn off the HVAC was generally pretty good. Radiation from a nuclear reaction decays very rapidly once the reaction stops, and so the worst part of the exposure is going to be in the first days after the accident. Depending on the structure you're in, it's generally healthier to wait a few days before moving and exposing yourself to radiation in transit. For people in a hospital, that goes double, as long as the power is on, and it's possible to filter the air intake. Hospitals are generally big concrete buildings, so staying in one is pretty safe. In the case of Fukishima, the people being evacuated because of radiation were only a small portion of the casualties from the Tsunami, and so the emergency services were seriously stressed. I'd imagine that evacuating those people would have gone much more smoothly if it hadn't been for all of the other Tsunami damage.