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Radiological protection

Although everyone receives background radiation, not many people encounter man-made radioactive substances in the normal course of their work. Those who do - medical and research workers, for instance - have to learn how to handle these materials without risking either their own safety or that of other people.

Part of this handling process is knowing how to protect yourself and others from receiving unnecessary doses of radiation. This is called radiological protection.

Protection from external sources of radiation takes four main forms -

• distance
• time
• source strength
• shielding.

Do not:

• work any nearer to a source than you need to
• stay with it any longer than you need to
• use one any stronger than you need to
• use an incorrect level of shielding for the type of radiation you are handling.

In a work context, radioactive sources can be sealed or unsealed. Sealed sources are 'canned' in a strong container: Unsealed sources are open to the air. Both emit radiation, but the unsealed source has the additional hazard of internal body contamination if an intake occurs. Unsealed sources thus require some containment.

Radioactivity is readily monitored with fairly simple equipment. It can also be measured at very low levels. This makes radioactive substances much easier to detect than some other toxic materials that may pollute our environment.

The instruments that detect and measure radiation are called monitors. Monitors vary in size from small pin-on badges to large walk-through installations, but essentially they all perform the same job of detecting and measuring the amount and type of radiation present in the working environment.

Monitors that measure the dose to an individual are called personal radiation monitors or dosemeters. Doses resulting from external radiation such as gamma rays, X-rays and beta particles are measured using optically stimulated luminescence dosemeters (OSLDs) or thermoluminescent dosemeters (TLDs). These dosemeters are worn by the radiation worker for periods of one to 3 months.

Dosemeters themselves are complemented by other monitoring devices that measure general radiation and air contamination levels in the workforce. Many of these are portable, battery-operated instruments that can be placed wherever needed or used to conduct radiation or contamination surveys. Equipment like this can be used to detect natural background radioactivity in, say, rock samples. There is no difference in kind between natural and man-made sources.