Response Comparisons of Electret Ion Chambers, LiF TLD, and HPIC

Abstract

During each quarter of 1991 electret ion chambers, nat Lif, 6 LiF, and 7 LiF thermoluminescence dosemeters, all integrating ionising radiation monitors, were placed at a location in the grounds of the National Institute of Standards and Technology. One group was exposed to the total ambient field, while a second group was sealed for testing a method of protection against radon gas intrusion. A high-pressure ion chamber at the same location provided another measure of the field. Simultaneously with the environmental response test, other sealed and unsealed groups of electret ion chambers and thermoluminescence dosemeters were exposed during each quarter to discrete exposures from calibrated sources of 60 Co and 137 Cs. All responses were evaluated at the end of each quarter. The results indicated that the electret ion chamber gave results comparable to thermoluminescence dosemeters for routine environmental monitoring. No significant difference was found for any monitor type when sealed results were compared with unsealed results. The electret devices gave results that were, on the average, closer to the pressurised ion chamber results than did the thermoluminescence devices for both the sealed and unsealed sets for the ambient fields, and the electret devices also gave results closer to the delivered air kerma values than did the thermoluminescence devices in the deliberate exposure test. The electret ion chambers' responses showed a somewhat greater variability than did the thermoluminescence dosemeters' responses.