Radiation protection

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File:Lead shielding.jpg
A lead castle built to shield a radioactive sample in a lab
File:Zone controlee.jpg
French sign: Zone contrôlée - Accès réglementé ("Controlled area, access subject to regulations")
File:Crocus-p1020480.jpg
Door of the biological shield of CROCUS. Note the operator on the left giving scale.

Radiation protection, sometimes known as radiological protection, is the science of protecting people and the environment from the harmful effects of ionizing radiation, which includes both particle radiation and high energy electromagnetic radiation.

It includes occupational radiation protection, which is the protection of workers; medical radiation protection, which is the protection of patients; and public radiation protection, which is about protection of individual members of the public, and of the population as a whole.

There are mainly three principles to radiation protection: those of time, distance and shielding. Radiation exposure can be managed by one or more of these:

  • Reducing the time of an exposure reduces the effective dose proportionally.
    • An example of reducing radiation doses by reducing the time of exposures might be improving operator training to reduce the time they take to handle a source.
  • Increasing distance reduces dose due to the inverse square law.
    • Distance can be as simple as handling a source with forceps rather than fingers.
  • Adding shielding can also reduce radiation doses.

Practical radiation protection tends to be a job of juggling the three factors to identify the most cost effective solution.

In some cases, improper shielding can actually make the situation worse, when the radiation interacts with the shielding material and creates secondary radiation that absorbs in the organisms more readily.

Different types of ionizing radiation behave in a different ways, so different shielding techniques are used.

One standard design practice is to measure the halving thickness of a material, the thickness that reduces gamma or x-ray radiation by half. When multiple thicknesses are built, the shielding multiplies. For example, a practical shield in a fallout shelter is ten halving-thicknesses of packed dirt. This reduces gamma rays by a factor of 1/1,024, which is 1/2 multiplied by itself ten times. This multiplies out to 90 cm (3 ft) of dirt. Shields that reduce gamma ray intensity by 50% (1/2) include (see Kearney, ref):

    • Ultraviolet radiation may or may not be ionizing, depending on the wavelength. It is not penetrating, so it can be shielded by any material which is opaque to it such as sunscreen. Anything that stops X-ray radiation will do the job as well. The ozone layer absorbs UV radiation, but its depletion considerably lowers its effectiveness, especially in extreme northern and southern areas of the globe.

See also

References

  • Oregon Institute of Science and Medicine This website offers the entire online version of Nuclear War Survival Skills with full graphics and web navigation, created with the permission of the author Cresson Kearny. This manual has proven technical info on expedient fallout shelters, radiation shielding for it, the nature of radiation, shelter habitation, and assorted shelter system needs that can be created from common household items. OISM also offers free downloads of other civil defense and shelter information as well.
  • Harvard University Radiation Protection Office Providing radiation guidance to Harvard University and affiliated institutions.

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