Answer to Question #1881 Submitted to "Ask the Experts"

Category: Instrumentation and Measurements — Instrument Calibration (IC)

The following question was answered by an expert in the appropriate field:

What requirements by regulation or recommendation are there for calibrating radiation detection (radiac) devices used for emergency response (by highway patrol, firemen, etc.) to transportation incidents involving radioactive materials? Simply put, why do I have to calibrate them?

For the most part, the Federal Emergency Management Agency dictates the calibration requirements for radiation detection (radiac) devices used for monitoring members of the public and their property in the event of a nuclear power plant accident. It is pretty proscriptive. Nevertheless, calibration is needed to ensure an instrument is functioning properly to an external gamma ray field, or if applicable, to alpha/beta/gamma activity on some contaminated surface.

One thing you might consider if you have a modern instrument(s) such as a Geiger counter with "pancake" probe, similar to what was done on the old CDV700 with a little uranium check source on the side of the electronics housing, is to get a small check source. A constancy check right after calibration, that can be checked again whenever the instrument is used, will provide a quick verification of function and that the response hasn't changed significantly since it was calibrated. (Watch the half-life of the check source, and decay if needed, for example, using ¹³⁷Cs.)

David J. Allard, CHP

Answer posted on May 7, 2002. The information and material posted on this Web site is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of materials and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Web site. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.