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Radiation is the process by which energy in the form of waves or particles is emitted from a source and spread through the surrounding medium or space.

Types of radiation
Some radiations such as light and sound are essential to some forms of life while others are harmful. Some radiations cause an alteration in the materials they pass through by disturbing the outer parts of atoms, causing an electrical charge. Atoms in this state are called ions: hence the name ionising radiation. The release of ionising radiation is called radioactivity.

Types of ionising radiation
Alpha radiation consists of helium atoms without their electrons.
Beta radiation consists of fast-moving electrons.
Gamma radiation is electromagnetic like light but of shorter wavelength.
Cosmic radiation consists of the nuclei of atoms and electrons, positrons and other sub-atomic particles.

Sources of radiation
The average dose of ionising radiation which people receive depends a lot on where they live and work. Typical figures for a member of the public might be:

50 -70%    from radon gas, which emits alpha particles
5 - 15%     from the ground and buildings
10 - 14%   from food and drink
12 - 14%  from cosmic radiation
A total dose of 2.2 millisieverts (2.2mSv) per year is average for a member of the public in the UK, and radiation doses from other sources may be compared to this amount of background radiation.

Medical uses
Diagnostic radiology (x-rays)

Nuclear medicine (radioactive substances introduced into the patient for diagnosis or treatment)

Radiotherapy (uses high power x-rays or radioactive sources to treat cancer.)

Damage due to radiation
The potential for damage to body tissue due to ionising radiation depends on the energy absorbed, the type of radiation and the energy associated with each type together with the type of tissue. Radiation is used medically when its advantage outweighs its potential for harm.

Uranium is the principal radioactive element used in the nuclear powered generation of electricity and in nuclear bombs.

The mining of uranium causes cancer in miners and some of the element finds its way into the surrounding land and water. The transportation of uranium involves the danger of theft or accident leading to its dispersal with a poisoning of the environment. The explosion of the power station at Chernobyl [link to be inserted] has made areas of Belarus uninhabitable. Some radioactive materials remain active for thousands of years and this makes difficult the safe disposal of nuclear waste.

Nuclear weapons
When a nuclear weapons explodes there is a release of ionising radiation which along with the blast and heat results in devastation many times greater than that caused by high explosive. If the explosion is at ground level quantities of irradiated material are drawn into the atmosphere eventually to fall to earth threatening the lives of people far away.

Ionising radiation is a naturally occurring phenomenon which, though it has useful medical applications, is damaging to health unless strictly controlled. To produce ionising radiation deliberately in the process of generating nuclear energy and its waste products is to increase the risk from ionising radiation in the environment not for decades or even centuries but for millennia. However, it may be argued that nuclear energy, by producing a source of energy without emitting greenhouse gases has benefits. It is much harder to argue the case for producing ionising radiation deliberately in the process of manufacturing nuclear weapons, since these weapons, if used, would have a catastrophic effect on the populations targeted and on the environment.

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