Portable radiation detectors generally perform well enough to meet new consensus standards but provide inaccurate readings for certain types of radiation, according to recent tests by the National Institute of Standards and Technology (NIST).
The results, reported in the May issue of the journal Health Physics,* are based on NIST tests of 31 commercial detectors, including hand-held survey meters; electronic personal alarming detectors (similar to pagers); and radionuclide identifiers (specialized devices that can identify specific radioactive materials). A number of federal, state and local agencies are using such instruments as part of homeland security-related efforts to detect and identify radioactive materials.
Researchers compared the devices exposure rate readings to NIST measurements for different energy and intensity levels produced by NISTs calibrated gamma ray and X-ray beam lines. The responses of the majority of the detectors agreed with NIST-measured values, within acceptable uncertainties, for tests with gamma rays. This performance meets requirements established by new American National Standards Institute (ANSI) standards, adopted by the Department of Homeland Security (DHS) in 2004. However, there was a large discrepancy between most detectors readings and the NIST values for the lowest-energy X-rays. For instance, readings by 14 detectors were roughly 40 to 100 percent below the NIST value. The deviations were much larger than those stated in manufacturers specifications.
Laura Ost | EurekAlert!
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