what was the worst nuclear accident
So far, there has never been a section of the planet rendered useless for thousands of years due to a nuclear power plant accident except the area covered by the Chernobyl sarcophogus itself. And that was due to an epically bad decision by the Soviets. Except small areas, Chernobyl is habitable now. Fukushima will be ~100% habitable in about 50 years, even if they stopped cleaning up. If they used appropriate phyto-remdiation it would be closer to 15 years.