Defintion #
When a radioactive substance breaks down, it emits radiation and is transformed into another substance that is not radioactive [1].
In physics, half-life is the time that elapses before the amount of a radioactive substance is reduced by half. This means that after 1 half-life, half of the original radioactive substance will have been transformed. After 2 half-lives, it will be reduced to a quarter, and so on.
The half-life is a constant for each radioactive substance and can vary from seconds to millions of years, depending on the properties of the substance.
Half-life – Short and long #
People tend to be most concerned by isotopes that have longer half-lives and often confuse it with “dangerous radioactivity”. It is based on a fundamental misunderstanding that radioactive materials emit a constant amount of radiation during this half-life. Higher radioactivity equals a shorter half-life and vice versa.
Short half-lives imply energy is released quickly, and are the primary hazard.
Long half-lives imply the energy is released slowly over a long period of time and are less of a hazard. You can hold long half-life isotopes of natural uranium in your hand without accumulating a hazardous dose.
