FIELD-TEST OF ELECTRET ION CHAMBERS FOR ENVIRONMENTAL MONITORING

A field test of electret ion chambers was performed to evaluate their performance in making environmental exposure measurements at nuclear f acilities. The objectives of the study were to determine electret ion chamber variability and to perform comparisons with thermoluminescent dosimeter and high-pressure ion chamber measurements. Three electret i on chambers were placed at each of 40 monitoring locations in the vici nity of a commercial nuclear power station during four consecutive qua rters. The electret ion chamber measurements were compared to thermolu minescent dosimeter measurements made by the Nuclear Regulatory Commis sion and the South Carolina Department of Health and Environmental Con trol. Two types of comparisons were made with the high-pressure ion ch amber. One used yearly average electret ion chamber measurements and i nstantaneous high-pressure ion chamber measurements at 15 of the monit oring locations. The other involved the simultaneous exposure of five electret ion chambers and the high-pressure ion chamber for 15 d at a single location. The mean ratios of electret ion chamber measurements to thermoluminescent dosimeter measurements was 1.06. The mean ratio o f electret ion chamber measurements to instantaneous and simultaneous high-pressure ion chamber measurements were 1.06 and 1.07, respectivel y. Electret variability, defined here as the ratio of the standard dev iation to the mean, was determined for each set of three detectors. Th e average variability for the 160 sets of quarterly measurements was s imilar to 7%. Among the 450 individual electret measurements, there we re six outliers. Based on the results of this study, electret ion cham bers appear to yield accurate measurements of environmental exposure p rovided that measures are taken to either minimize or correct for rado n interferences and care is taken to prevent spurious discharges durin g handling.