RADON AND THORON IN-AIR OCCUPATIONAL EXPOSURE STUDY WITHIN SELECTED WINE CELLARS OF THE WESTERN CAPE (SOUTH AFRICA) AND ASSOCIATED ANNUAL EFFECTIVE DOSES

摘要

This is the first known study of exposure of Rn-222 (radon) and secondarily Rn-220 (thoron) in-air activity concentrations assessed within nine selected wine cellars in four wine districts of the Western Cape (South Africa) and the associated annual occupational effective doses. E-PERM electret ion chambers (EIC) and RAD-7 alpha-detectors were used to perform these measurements. The radon in-air levels ranged from 12 +/- 4 Bq m(-3) to 770 +/- 40 Bq m(-3) within the nine selected wine cellars. Eight of the nine wine cellars (excluding results from cellar w-6) had a median radon in-air activity concentration of 48 +/- 8 Bq m(-3). Continuous thoron in-air activity concentration levels were also measured near an internal granite wall of the wine cellar w-6 (barrel room), where peak levels of up to 1,520 +/- 190 Bq m(-3) and an average of 680 +/- 30 Bq m(-3) were observed. The occupational annual effective dose due to radon and decay progeny exposure in-air within the selected wine cellars ranged from 0.08 +/- 0.03 mSv to 4.9 +/- 0.3 mSv with a median of 0.32 +/- 0.04 mSv (T-max = 2,000 h). The annual effective dose within the wine cellar (w-6) ranged up to a maximum of 2.5 +/- 0.4 mSv (T-max = 2000 h) due to exposure to thoron and decay progeny. In general, most of the wines cellars pose negligible associated health risk to personnel due to ionizing radiation exposure from the inhalation of radon and progeny. Under certain conditions (proximity and exposure time), caution should be exercised at wine cellar w-6 because of elevated thoron in-air levels.