Uses and hazards of radiation · GCSE Physics

Contamination and irradiation

Radioactive contamination is the unwanted presence of materials containing radioactive atoms on or in other materials. The hazard comes from the decay of the contaminating atoms, and the type of radiation affects how dangerous it is.
Irradiation is exposing an object to nuclear radiation. An irradiated object does not become radioactive.
Precautions: shielding, handling sources with tongs, wearing gloves, keeping sources away from the body and minimising exposure time.
Research on the effects of radiation is published and shared with other scientists so it can be checked by peer review.

Outside the body, beta and gamma are the most dangerous because they can penetrate the skin. Alpha is stopped by skin.
Inside the body (if swallowed or breathed in), alpha is the most dangerous because it is so strongly ionising and all its energy is absorbed by nearby cells.
Ionising radiation can damage cells and DNA, causing mutations and cancer, or kill cells.

Background radiation is around us all the time. Natural sources include rocks (such as granite, which releases radon gas) and cosmic rays from space.
Man-made sources include fallout from nuclear weapons testing, nuclear accidents and medical X-rays.
The level of background radiation, and the radiation dose, depend on where you live and your job. Radiation dose is measured in sieverts (Sv), often millisieverts (mSv).

Medical tracers: a gamma emitter with a short half-life is injected or swallowed and detected outside the body to explore internal organs.
Radiotherapy: gamma rays, or radioactive implants, are used to control or destroy cancer cells. They are carefully aimed to limit damage to healthy tissue.
Gamma rays are also used to sterilise medical equipment and food. Smoke detectors use alpha sources.

Contamination: The unwanted presence of radioactive atoms on or in a material.
Irradiation: Exposing an object to nuclear radiation; it does not become radioactive.
Background radiation: Radiation that is around us all the time from natural and man-made sources.
Sievert: The unit of radiation dose (Sv).
Tracer: A radioactive isotope put into the body so its path can be followed.
Radiotherapy: Using radiation to destroy cancer cells.
Radon: A radioactive gas released from some rocks.