Since more exposure equals more risks, all exposures must be minimized. We can minimize our exposures through four main control measures: time, distance, shielding, and contamination control.
Time: When working with radiation sources, the more time personnel are exposed to the source, the more radiation exposure personnel will receive. The exposure effects maybe unnoticeable or negligible, but the overall dose is always considered cumulative. Therefore, careful steps must be taken to minimize exposure. Steps like rehearsing a radiation procedure, adjusting the source's power output to what is needed and careful management of on-times will prevent unnecessary retakes and reduce the time the source is used.
Distance: The most effective method of minimizing radiation exposures is to simply increase the distance between the source and the personnel exposed. The inverse square law applies to radiation emissions, in that the radiation intensities fall off very rapidly as the distance increases.
For example, if the distance is doubled, the radiation intensity is reduced by a factor of four. Obviously, a few feet may make a difference. Steps like keeping personnel as far away from the source as possible, establishing and maintaining controlled areas and directing beams away from potentially occupied areas are extremely important.
Shielding: Any material placed between the source of the radiation and the potentially occupied areas will absorb some of the radiation and thus reduce exposures. In general, the more material used or the denser the material, the more radiation will be absorbed.
Shielding is generally required when areas adjacent to the radiation source are potentially occupied. Good shielding begins with the proper design and installation of the shielding. Careful consideration must be followed for renovations to ensure the shielding is not compromised. Shielding, such as collimators, must be used to restrict the beam to just the area of interest.
Shielded facilities should be used whenever available, or strict control measures must be followed. Last, simple shielding, such as lead aprons, must be used when required by the operation.
Contamination Control: This mainly applies to the use of radioactive materials. When a radioactive source is suspected of being broken or potentially leaking, it should be isolated and the radiation safety officer (RSO) should be consulted immediately.
Proper hygiene is the easiest and most effective measure to prevent radioactive materials from getting on the skin and clothes, and to guard against accidental ingestion. If during an operation, you identify a potential problem, you must do the minimum. Cease operations and secure the area. Seek medical assistance if required. Contact your supervisor. Contact the base RSO.
For after duty hour emergencies, the RSO can usually be contacted through the command post, or through the after hours medical care phone line. Each individual must complete a statement of events including any and all operating parameters, distances, observations, times, and conditions.
All the required procedures for maximizing the effectiveness of time, distance, shielding and contamination control, should spelled out in a unit-specific radiation safety Operating Instruction.
This OI should be concise but cover shop-specific operations, training requirements, protective equipment required, engineering controls and procedures of what to do, if you suspect an over-exposure.