Pages in this chapter (8 of 14)
The basic ways of controlling exposure
Ionising radiation: time, distance and shielding
- Minimise time spent in areas with raised radiation levels. Less time means a smaller dose from the source.
- Maximise distance from the source. A worker's dose falls as distance from the source grows. For an approximately point source in suitable free-field conditions, doubling distance reduces dose rate to about a quarter. Extended sources, scattering and shielding can alter that relationship, so actual arrangements need specialist assessment.
- Use shielding. Place a suitable shield between the source and the worker. The material, thickness and arrangement must suit the radiation and source. Shielding reduces exposure but must not be assumed to remove every dose or contamination risk.
Non-ionising radiation
The best way to reduce the risk is to eliminate the source. If that cannot be done, use other controls set out in your exposure control plan. The time, distance and shielding principle applies here too. When choosing controls, work through the following steps in order of effectiveness.
Engineering controls. Physical changes to facilities, equipment and processes can reduce exposure. Examples:
- guards or barriers to restrict access to high-exposure areas
- raising antennas above the working level of a roof
- shields to protect nearby workers from exposure
Administrative controls. Changes to work practices and policies, together with awareness tools and training, can limit the risk. Examples:
- switch off equipment before working around it
- secure or restrict access to communication and data transmitting equipment
- post warning signs for high radiation areas
- limit the time workers spend near the antenna
- introduce a notification system to alert workers and contractors
- run a UV protection programme
Personal protective equipment. Use suitable protection for the remaining assessed risk, alongside higher-order measures where practicable. Selection is source-specific: ordinary PPE is not effective shielding against penetrating X-rays or gamma radiation. For optical radiation, examples include:
- suitable eyewear and protective clothing
- checks that the PPE works properly
- sunscreen
Basic radiation protection strategies
Identify every source of ionising and non-ionising radiation in the workplace and the risks it creates. Once the significant risks are known, they must be controlled. Try to cut exposure to ionising and UV radiation as far as possible. You may be able to use a safer alternative process or equipment, for example ultrasonic non-destructive testing instead of X-rays.
| Do | Do not |
|---|---|
| Know the potential sources of radiation in your workplace, particularly ionising radiation, UV light and high-power lasers | Override any interlock that prevents access to high-voltage electrical equipment, X-ray cabinets, laser enclosures or machinery containing lasers |
| Consider getting competent advice from a radiation protection adviser (RPA), which may be a legal requirement when working with ionising radiation | Use germicidal UV lamps, which can be harmful, as replacements in otherwise safe insect-killing devices or other fluorescent fittings. Fit the type the manufacturer specifies |
| Consider whether staff should have medical surveillance, with the RPA's help | |
| Include radon gas in the risk assessment, because it occurs naturally and may be present in your workplace even if you do no other work with radiation | |
| Use source-specific shielding and contamination controls for ionising radiation; select suitable skin and eye protection for optical hazards such as molten metal and welding | |
| Seek expert advice where lasers are used for displays, such as in bars and stage shows, and the public could be at risk |
Summary notes for Element 5 · Cheat sheet · Glossary. A study aid, not published or endorsed by NEBOSH.