Radiation protection, sometimes known as radiological protection, is the science of protecting people and the environment from the harmful effects of both particle radiation and ionizing radiation.
It includes occupational radiation protection, which is the protection of workpeople; 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 main 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.
In x-ray facilities, the plaster on the rooms with the x-ray generator contains barium sulfate and the operators stay behind a leaded glass screen and wear lead aprons.
Practical radiation protection tends to be a job of juggling the three factors to identify the most cost effective solution.
In some cases, just a bit of shielding can actually make situation worse, when the radiation interacts with the shielding material and creates secondary radiation that absorbs in the organisms more readily.
Different types of radiation behave in a different way, so different shielding techniques are being used.
Particulate radiation consists of a stream of charged or neutral particles, both charged ions and subatomic elementary particles. This includes solar wind, cosmic radiation, and neutron flux in nuclear reactors.
Alpha radiation is the easiest to shield from, because the alpha particles can be stopped even with a leaf of paper.
Beta radiation, a stream of electrons is more difficult, but still a relatively thin layer of aluminum can do the job. In case of Beta+ radiation, consisting of positrons, the gamma radiation from the annihilation reaction poses additional concern.
Neutron radiation is not as readily absorbed as charged particle radiation. Neutrons are absorbed by nuclei of atoms in a nuclear reaction (which often leads to emission of gamma photons, causing additional shielding concerns), but fast neutrons have first to be slowed down (moderated) to slower speeds, by inelastic collisions with heavy nuclei or by elastic collisions with light ones. Large mass of hydrogen-rich material, eg. water (or concrete, which contain a lot of chemically-bound water), polyethylene, or paraffin wax is commonly used. It can be further combined with boron for more efficient absorption of the thermal neutrons.
Cosmic radiation is not a common concern, as the Earth's atmosphere absorbs it and the magnetosphere acts as a shield, but it poses a problem for satellites and astronauts. While satellite electronics can be radiation hardened, astronauts can't, so they have to be shielded. Because weight is a premium on space technology, methods alternative to absorption are being proposed, eg. shielding using superconductor electromagnets.http://www.thespacereview.com/article/308/1http://www.futurepundit.com/archives/002704.html Aircrews and frequent flyers are at a slight risk too.
X-ray and gamma radiation are absorbed by atoms with heavy nuclei; the heavier the nucleus, the better the absorption. In some special applications, depleted uranium is used, but lead is much more common. Barium sulfate is used in some applications too. Against more intensive radiation sources, this shielding has to be thick, which brings technical problems.
Ultraviolet radiation is absorbed in organic molecules of certain structures, being the active ingredients of sunscreens. Anything that stops ordinary low-energetic radiation will do the job too. The ozone layer absorbs UV radiation, but its depletion considerably lowers its effectivity especially in northern and southern areas of the globe.Source:
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The Basics of Radiation Protection
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