Half-Life & Risk
- The half-life is the time it takes for the activity of a radioactive source to decrease to half of its original value
- Different radioactive isotopes can havevery different half-lives
- For example:
- Francium-218 has a half-life of only 1 millisecond (0.001 seconds)
- Polonium-210 has a half-life of about 140 days
- Uranium-235 has a half-life of about 700 million years
Short Half-Life Values
- If an isotope has a short half-life, the nucleiwill decay very quickly
- This means that the isotope will emit a lot of radiation in a short amount of time
- If only a small amount of the isotope is used, having a short half-life can be advantageous, as the material will quickly lose its radioactivity
- If a large amount is used, however, the levels of radiation emitted could make handling the isotopeextremely dangerous
Long Half-Life Values
- If an isotope has a long half-life then a sample of it will decay slowly
- Although it may not emit a lot of radiation, it willremain radioactive for a very long time
- Sources with long half-life values present a risk of contamination for a much longer time
- Radioactive waste with a long half-life is buried underground to prevent it from being released into the environment
Depending on the activity of radioactive waste, it is buried in different ways
