Nuclear energy

Radioactivity

Nuclear energy (also called atomic energy) is liberated by the disintegration of the nuclei of certain atoms, the unstable atoms. To gain stability, the unstable atoms are transformed into another type of atom, liberating energy in the form of radiation; this is the phenomenon known as radioactivity.

In nature most of the elements are stable, but some are unstable and to attain stability, they disintegrate gradually, emitting one or several particles, and thus energy in the form of radiation. That is what is called radioactivity.
This phenomenon happens naturally. We live – and have always lived – in an environment that is naturally radioactive. This is natural radioactivity.
In nature, all the matter in the universe and all living bodies are made up, in part, of radioactive atoms: our body is therefore radioactive. 68% (approximately 2/3) of the radioactivity to which we are exposed every year is of natural origin. This varies according to:

- The nature of the geological surroundings: radioactive material has been present on Earth since its formation. Granite regions have a naturally higher radioactivity;

- The altitude: the higher the altitude, the greater the exposure to cosmic radiation.

But radioactivity has many applications in our everyday life:

- To produce energy (in nuclear power stations);

- For medical ends, to treat people who are ill (radiotherapy) or to conduct medical examinations (it’s the principle of the IRM scanner);

- In archaeology, to date ruins;

- Or for industrial uses (measurement, food preservation …)

This is what is called artificial radioactivity. 28% of the artificial radioactivity to which we are exposed, comes from the medical sector (examinations and treatments).

As atoms disintegrate the radioactivity of an element diminishes: that is what is called radioactive decay.

The time over which the radioactivity decreases by a factor of one half is called the radioactive half-life. Each element has its own particular half-life, values varying from several fractions of a second to billions of years.

Some examples:
Oxygen 15: 2 minutes.
Iodine 131: 8 days.
Carbon 14: 5730 years.
Uranium 238: 4.5 billion years.