How long does it takes a radioactive material to decay?

Answer 1

Nuclear explosions produce both immediate and delayed destructive effects. Immediate effects (blast, thermal radiation, prompt ionizing radiation) are produced and cause significant destruction within seconds or minutes of a nuclear detonation. The delayed effects (radioactive fallout and other possible environmental effects) inflict damage over an extended period ranging from hours to centuries, and can cause adverse effects in locations very distant from the site of the detonation.

Further reading:

http://nuclearweaponarchive.org/Nwfaq/Nfaq5.html

http://en.wikipedia.org/wiki/Nuclear_fallout

Answer 2

It depends on the radioactive material. All radioactive isotopes have a property called a "half-life". This is the time it takes for half the atoms in the sample to decay. This concept is a little confusing. "Half" refers to "half of whatever's left," so after one half-life, half of the radioactive material will still be there; after two half-lives, half the original material plus half of the other half will be gone and one quarter will remain; after three half-lives one eighth will remain, and so forth. Complicating this even further is that some materials decay into OTHER radioactive materials which have their OWN half-lives, and which may then decay into YET MORE radioactive materials... As you can see, the bookkeeping can get fairly involved, even without allowing for the fact that some materials have several decay options.

Answer 3

I'm going to go out on a limb here and say that the question you meant to ask was "how long does a radioactive substance stay radioactive." The answer is that it depends on what the radioactive substance is. Some things decay quickly and are intensely radioactive for a short time but then fall to more or less background levels; other things decay slowly and remain radioactive for a very long time.

Answer 4

The time it takes for a radioactive material to decay completely depends on the specific isotope. This time can range from a fraction of a second to billions of years. The rate of decay is measured using a half-life, which is the time it takes for half of the radioactive atoms in a sample to decay.