Detecting and Measuring Radiation

•You cannot see, smell, taste, feel, or hear radiation, but we have very sensitive instrumentation to detect it at very low levels. Radiation monitoring instruments detect the presence of radiation. The radiation measured is usually expressed as exposure per unit time, using various units of measure, milliroentgen per hour (mR/hr) and counts per minute (CPM). Anything with “milli” in front of it is SMALL! The most commonly used instruments to detect the presence of radiation include:

•Geiger- Mueller Survey Meter. The Geiger-Mueller (GM) survey meter (also known as a Geiger counter) will detect low levels of gamma and most beta radiation. The instrument typically has the capability to distinguish between gamma and most beta radiation. This instrument is used to quickly determine if a person is contaminated. GM survey meters are very sensitive and other instruments may be needed to measure higher levels.

•Ionization Chamber Survey Meter. This device can accurately measure radiation exposure. These meters measure from low levels (mR/hr) to higher levels (many R/hr). To find the dose an individual is receiving, multiply the dose rate by the time that they are exposed.

•Personal Dosimeters. These devices measure the cumulative dose of radiation received by persons wearing them. Film and TLD badges must be analyzed by the company that supplies them and so the dose received is not typically known for several days. However, self reading dosimeters allow the wearer to immediately see the total dose they have received.