TLD badges and film badges are used to detect radiation at levels that can be harmful to humans. They emit light in amounts proportional to the radiation received. Thermoluminescent dosimeters (TLDs) are made from one more fluoride chips that measure cumulative exposure to ionizing radiation. Like film badges, they are worn for periods of approximately three months and are then processed to determine the dosage of radiation detected. TLD and film badges are logged to maintain cumulative records of an individual’s exposure to radiation over an extended period of time.
TLD badges and film badges include several types of thermoluminescent dosimeters, devices that can measure doses as low as millirem. TLD badges are similar to film badges, but can measure smaller amounts of radiation. TLDs work by measuring the amount of visible light emitted from a crystal in the detector during exposure to ionizing radiation. The exposure of the crystal detector results in ionization, thus producing or trapping electrons in an excited state of the crystal. The dose of radiation exposure is proportional to the number of traps that are created. The TLD is then sent to a lab and heated to depopulate the trap, thus releasing light. With both TLD and film badges, the amount of light released measures the radiation dosage.
Film badges are-radiation sensitive films that are used to measure and record radiation exposure levels at higher levels. These plastic badges contain a small piece of photographic film to record exposure to gamma rays, X-rays, and beta particles. Film badges create permanent records that are able to distinguish between different energies of photons and dosages of different types of radiation. Although film badges are very accurate for exposures over one-hundred millirem, they can’t measure exposures of gamma rays less than 20 millirem with great accuracy. Other disadvantages of film badges are that they must be developed and read by a processor, which can be time consuming. In addition, heat exposure can affect the film.
Employees who handle radioactive wastes and other radioactive materials must learn how to use TLD badges and film badges. Although these products can provide important information about personal radiation exposure, they do not provide safety through radiation shielding. Radiation safety can be monitored by consistently wearing TLD and film badges, and in accordance with all manufacturer specifications.