How Does a Film Badge Dosimeter Work?

By Benjamin Aries

Film badge dosimeters are used to monitor the level of radiation in an area, and are commonly worn by personnel who work around devices producing gamma and x-rays. At the core of a dosimeter badge is the film. This thin material reacts to radiation and is surrounded by a case that prevents light and moisture from damaging the film. When radiation is present, the film reacts and becomes dark. This thin film typically has two sides. One has a large-grain coating and reacts when low radiation levels are present. The other has a coating of finer grain, and is not as easily affected by rays. The large-grain side is used as an early indication of exposure, while the fine side can be examined to determine the exact level of radioactivity.

The Film

Film badge dosimeters are used to monitor the level of radiation in an area, and are commonly worn by personnel who work around devices producing gamma and x-rays. At the core of a dosimeter badge is the film. This thin material reacts to radiation and is surrounded by a case that prevents light and moisture from damaging the film. When radiation is present, the film reacts and becomes dark. This thin film typically has two sides. One has a large-grain coating and reacts when low radiation levels are present. The other has a coating of finer grain, and is not as easily affected by rays. The large-grain side is used as an early indication of exposure, while the fine side can be examined to determine the exact level of radioactivity.

The Badge

A badge protects the film during use. In addition to holding the film, this badge also features several filters which are used to judge the type of radiation. Radiation can be present at many different levels. The filters allow some energy types to pass, while blocking others. Safety professionals can check which filters are affected, and learn details about the level of radioactive energy present. Badges also feature a small opening that reacts to beta particles. These beta particles are often an early sign of radiation leakage. The opening allows workers to frequently check for any changes and take action if needed.

Detector Placement

Film badges cannot function properly unless they are positioned correctly. Incorrect placement can cause negative or inaccurate readings, which compromise safety. One of the most common placements is between the head and the waist. This position lets the badge detect radiation in the largest areas of the body. Other badges can be placed on the finger as a ring. This position is used to detect ionizing radiation, such as a narrow beam directed toward a work area. Multiple badges can be used to cover different areas, if radiation exposure is a high risk.

© Demand Media 2011