Personal Monitoring of Radiation Professionals

All persons associated with commercial, diagnostic or therapeutic use of radioisotopes or radiochemicals, x-rays or other sources of radiation could be labeled as radiation professionals or radiation workers. Excessive exposure to radiation beyond the maximum permissible dose (MPD) for a person of a particular age may lead to serious healthy problems. The maximum permissible dose [MPD=(N-18)x5=?Rads; where N stands for the age in years] to the whole body, at any age is equal to 5 times of the number of years beyond 18 years. The MPD in consecutive three months should not exceed 3 rads. The accumulated MPD is also the MPD for the head and the trunk of a person associated with the handling and use of radiochemicals or radioisotopes or operating radiation equipments.

The dose received by any individual is ascertained by various types of monitoring procedures. The most commonly used are film badges and small ionization chambers. The film badges and small ionization chambers are supplied and monitored by many commercial firms.

Film Badges:

The film badge is a small packet of photographic film which is sensitive to radiation; or it may be containing two pieces of photographic films of different sensitivities. A part of these films is covered by one or more metal filters to resist the beta radiation and the other part is open to the beta radiation exposure. For x-rays a different type of film and filter is employed in the film badge. The film badge is worn by the person while handling the radiochemicals or operating radiation equipments. The darkening of the film of the film badge is related to the radiation dose received by a worker. Under the open window it gives the effect of beta radiation and under the filter the effect of gamma radiation or high energy x-rays.

Small Ionization Chambers:

The ionization chambers used for the personal monitoring are small instruments about the size and shape of a fountain pen. These are also called "pocket dosimeters". Before putting to use these are charged with electric pulse from a special charger. The charging transfers the electrical charge to the insulated wire inside the pocket dosimeter. The principle of the functioning of an ionization chamber or pocket dosimeter is that on exposure to the radiation the charge on the insulated wire inside it would decrease.