how long does it take for radiacion to go away?
- Anonymous1 decade agoFavorite Answer
Radiation covers a lot of things. The americium-241 in your smoke detector has a half-life of 432.2 years. That is, if you start out with 1 gram of americium at the end of 432.2 years you'll have 0.5 grams, and after 864.4 years you'll have 0.25 grams, 0.125 grams, then 0.0625 grams... on and on until you eventually have two atoms, then one, then none. After each four centuries and change the amount left is cut in half.
So at first it cools down "quickly" but there will be a little bit of lingering radiation for a very, very long time.
Some isotopes are worse. Uranium-235 has a half-life of 700 million years. Good luck waiting for the very last atom of that to go away.
This is why nuclear war is such a frightening prospect. The majority of the fallout will be short-lived isotopes that will fade appreciably after a few weeks or months, but some of it will be permanent. Earth will never be really human-friendly again.