Answer to Question #1069 Submitted to "Ask the Experts"

The most common form of environmental monitoring for gamma radiation involves placing radiation monitoring devices at various locations around the site you are monitoring. For example, every nuclear power plant is continuously monitored by a bevy of dosimeters that are placed at different distances and on different sides of the plant. These dosimeters measure radiation dose from the plant or any radioactivity that is released by the plant. In most cases, it is difficult to differentiate between natural background radiation and that coming from the plant because power plant emissions are so low. You will also find radiation monitors around most Department of Energy (DOE) facilities, radioactive waste sites, and other places where people are concerned about the potential for radiation exposure to the public or the environment. You can contact the Nuclear Regulatory Commission (NRC), DOE, or individual nuclear power plants or DOE sites to ask for copies of their environmental monitoring reports, including the locations of their dosimeters and the monitoring results. These reports are generally well written and factual, containing a large amount of both data and the interpretation of those data.

In general, radiation levels around these types of facilities are so low that it doesn't make sense to measure them with a "real-time" monitoring device. Instead, dosimeters such as film badges or TLDs (thermoluminescent dosimeters) are set out and are read every few months. I have never worked on a project that produced high enough radiation levels to read with a hand-held monitor, but this doesn't mean that no such projects exist. In such cases, it would be best to use either an ion chamber or a "micro-R" meter, both of which are specifically designed to monitor radiation levels. Many people make the mistake of trying to use a Geiger counter, which is not always appropriate. Because of its design, a Geiger counter must be carefully calibrated to use for measuring radiation levels accurately, and this is not normally done.

You can find more information about environmental monitoring from many sources, including DOE and NRC. In addition, the National Council on Radiation Protection and Measurements has two reports that might be of interest:

NCRP Report #50—Environmental Radiation Measurements (1976)
NCRP Report #58—A Handbook of Radioactivity Measurements Procedures (1985)

Another source of information includes the Environmental Measurements Laboratory (EML), part of the Science and Technology (S&T) Directorate of the Department of Homeland Security (DHS). The EML Web page includes a place where you can download its laboratory procedures manual. However, these procedures describe laboratory procedures for measuring radioactive contamination and may not address your concerns.

Andrew Karam, CHP
University of Rochester