What is a Radiation Dosimeter and What Does it Indicate?

A dosimeter or radiation plate is a device that detects and measures the radiation to which you have been exposed. It is used to measure the dose absorption of external ionizing radiation and records the radiation dose received. Modern electronic personal dosimeters can provide a continuous reading of the cumulative dose and the current dose rate, and can warn the user with an audible alarm when a specified dose rate or cumulative dose is exceeded. Other dosimeters, such as thermoluminescent or film types, require post-use processing to reveal the cumulative dose received, and cannot give a current dose indication while in use.

Dosimeters usually record a dose, the absorbed radiation energy measured in gray (Gy), or the equivalent dose measured in sieverts (Sv). A personal dosimeter is a dosimeter that the monitored person wears on the surface of the body and records the radiation dose received. Electronic dosimeters can be considered optional, being most important for new personnel or when introducing new procedures. They can also be used to check the readings of other dosimeters, such as PRDs or other gamma-ray dosimeters.

Thermoluminescent dosimeters were invented in 1954 by Professor Farrington Daniels of the University of Wisconsin-Madison. The dosimeter plays an important role within the international radiation protection system developed by the International Commission on Radiological Protection and the International Commission on Radiation Units and Measures. A thermoluminescent dosimeter measures exposure to ionizing radiation by measuring the intensity of light emitted by a crystal doped with Dy or B in the detector when heated. Dosimeters are generally used outside clothing, around the chest or torso to represent the “whole body” dose.

Commonly used routine dosimeters include poly (methyl methacrylate) (PMMA) or plexiglass, radiochromic, cellulose triacetate (CTA) films, cericcerous dosimeters, and ECB. This personal dosimeter is placed on the torso and displays the immediate dose and dose rate on the small monitor. Additional dosimeters can be used to assess the dose in the extremities or in radiation fields that vary considerably depending on the orientation of the body towards the source. For electron irradiation, the graphite calorimeter is the main or reference dosimeter, while the CTA film is widely used as a routine dosimeter.