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| Film Badge |
Introduction
Radiation is energy travelling through space. There are two types of radiation which are ionizing radiation and non-ionizing radiation.Ionizing radiation is any type of particle or electromagnetic wave that carries enough energy to ionize or remove electrons from an atom. There are two types of electromagnetic waves that can ionize atoms: X-rays and gamma-rays, and sometimes they have the same energy. Gamma radiation is produced by interactions within the nucleus, while X-rays are produced outside of the nucleus by electrons. However, most people fear of ionizing radiation because it can cause damage to matter particularly living tissue. At high level, it is therefore dangerous, so it is necessary to control our exposure. Thus, the devices to monitor the radiation dose has widely been invented in order to check how much dose of radiation that has been exposed to us. A film badge is one of the radiation external monitoring that is widely used in profession which exposed to radiation everyday. An example of it are the radiographer and radiotherapist. It is a thin plastic container whch opens at a hinge .Inside, there is a piece of film behind some window.
The components of film badge & how it works
- Film are kept inside the badge to trace any radiation exposure
- Copper filter interprets high penetrating photons or deep dose
- Aluminium filter interprets low penetrating photons or shallow dose
The film is packaged in a light proof, vapor proof envelope preventing light, moisture or chemical vapors from affecting the film.
A special film is used which is coated with two different emulsions. One side is coated with a large grain, fast emulsion that is sensitive to low levels of exposure. The other side of the film is coated with a fine grain, slow emulsion that is less sensitive to exposure. If the radiation exposure causes the fast emulsion in the processed film to be darkened to a degree that it cannot be interpreted, the fast emulsion is removed and the dose is computed using the slow emulsion.
The film is contained inside a film holder or badge. The badge incorporates a series of filters to determine the quality of the radiation. Radiation of a given energy is attenuated to a different extent by various types of absorbers. Therefore, the same quantity of radiation incident on the badge will produce a different degree of darkening under each filter. By comparing these results, the energy of the radiation can be determined and the dose can be calculated knowing the film response for that energy. The badge holder also contains an open window to determine radiation exposure due to beta particles. Beta particles are effectively shielded by a thin amount of material.
Film Badge Characteristics.
- Limited range less than 10 mR will not be measured
- Energy dependent
- Must be changed monthly
- Popular for personal monitoring
- Must be worn with proper side to exposure
- Sensitive to heat, humidity and water
Usage
1. To measure and records radiation exposure due to gamma rays, X-rays and beta particle. Advantages
- .Provides a permanent legal record.
- Can differentiate between scatter and primary beam.
- Able to distinguish between different energies of photons.
- Can measure doses due to different types of radiation.
- Quite accurate for exposures greater than 100 millirem.
- Lightweight, durable, portable.
- Cost efficient.
- Can indicate the origin of the radiation
Disadvantages
- Must be developed and read by a processor, which is time consuming.
- Prolonged heat exposure and humidity can affect the film.
- Exposures of less than 20 millirem of gamma radiation cannot be accurately measured.
- The exposure can only recorded when it is worn.
- Sensitivity is decreased above and below 50 keV.
- Exposure cannot be determined immediately.
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