Radiation Protection

We are exposed to radiation through several different means (external exposure, contamination, incorporation).

Radiation can be transported by wind or rain from the radiation source to our surrounding and enter our body through skin contact, breathing or the food chain.

We can reduce radiation doses from external exposure by shortening the time of exposure, increasing distance from a radiation source and shielding.

1. Shortening the time of exposure; it’s easy to minimize the time for external exposure (gamma and x-rays). However, if radioactive material gets inside our bodies, we can't move away from it. We have to wait until it decays or until our bodies can eliminate it. 

The amount of radiation an individual accumulates will depend on how long the individual stays in the radiation field, because:

Dose (mrem) = Dose Rate (mrem/hr) x Time (hr) Therefore, to limit a person’s dose, one can restrict the time spent in the area. How long a person can stay in an area without exceeding a prescribed limit is called the "stay time" and is calculated from the simple relationship:

 Stay Time = (Limit (mrem)) ÷ (DoseRate (mrem/hr))

2.     Increasing distance from a radiation source; Alpha and beta particles don't have enough energy to travel very far but gamma rays can travel long distances.

3.     Shielding; Shielding means having something that will absorb radiation between us and the source of the radiation such as lead, concrete or water to reduce radiation intensity.

Alpha particles are easily shielded. A thin piece of paper or several cm of air is usually sufficient to stop them. Thus, alpha particles present no external radiation hazard. Beta particles are more penetrating than alpha particles. Beta shields are usually made of aluminum, brass, plastic, or other materials of low atomic number to reduce the production of bremsstrahlung radiation.

Maximum Permissible Occupational Exposure to Adults or Restricted Area Exposure:

 1) The total effective dose equivalent must not exceed 5 rem (0.05 Sv) per year.

2) The sum of the deep dose equivalent and the committed dose equivalent to an individual organ or tissue other than the lens of the eye must not exceed 50 rem (0.5 Sv) per year.

 3) The dose equivalent to the lens of the eye must not exceed 15 rem (0.15 Sv) per year.

 4) The shallow dose equivalent to the skin or to any extremities must not exceed 50 rem (0.5 Sv) per year.

Finally;Occupational exposure to any individual who is under the age of 18 is permitted only if their exposure is limited to ten percent or less of the limits specified above for adult workers. For this reason, it is recommended that minors not be employed as full-time radiation workers.

 This diagram demonstrates the ability to penetrate matter of different kinds of ionizing radiation. Alpha particles are stopped by a sheet of paper whilst beta particles halt to an aluminium plate. Gamma radiation is dampened when it penetrates matter. (Photo credit: Wikipedia)