ELECTRET ION-CHAMBER RADON MONITORS MEASURE DISSOLVED RN-222 IN WATER

This paper describes a simple and relatively inexpensive method of det ermining the concentration of dissolved Rn-222 in water. The method in volves a recently developed electret-passive environmental radon monit or, which uses an electret ion chamber. The procedure consists of seal ing a known volume of a carefully collected water sample with one of t hese monitors in an exposure container and determining the average equ ilibrium Rn-222 gas concentration in the air phase during the exposure time period. This average concentration can then be used to calculate the Rn-222 concentration in the original water sample. Identical samp les were analyzed both by this new method and by a standard liquid sci ntillation method, and the results were compared over a wide range of Rn-222 concentrations. There was good agreement except that the electr et ion chamber method gave results that were consistently lower by abo ut 15%. This bias in the results was attributed to both Rn-222 losses during sample handling and possibly to some errors in the assumptions made in the theoretical model. A correction factor is recommended to b ring the results of this technique into agreement with the standard me thod. The procedures are simple and economical and can be easily emplo yed by many primary Rn-222-measuring laboratories currently using thes e monitors for measuring indoor Rn-222.