Cesium is forever (or, it might as well be)

There is no such thing really as a "cleanup" of a nuclear accident the size of Chernobyl or Fukushima. Most of the radionuclides stay around for centuries because of their long half lives. You can remove them or bury them, but there is no way to neutralize them. According to an article in The Guardian, when a major forest fire eventually happens in the Chernobyl Exclusion Zone, it will release large amounts of cesium that are now stored in the trees, and the smoke could spread as widely as in the original disaster in 1986.

A firefighter from the area was quoted as saying: "I know when I am fighting a fire on radioactively contaminated ground – you get the heat just like an ordinary fire, but you get a tingling sensation too, like pins jumping all over your body. I don't know how bad it is for me, there's no medical testing afterwards, we just go and wash."