Field and laboratory methods used by the Geological Survey of Canada in geochemical surveys, No. 10. radon determination apparatus for geochemical prospecting for uranium

Abstract
A radon detection instrument was developed comprising a port­able nuclear scaler-timer, a photomultiplier, alpha- sensitive cells made with silver-activated zinc sulphide, and a simple vacuum system. The instrument is suitable for the absolute determination of radon in 30 to 40 water samples per day with a practical lower detection limit of 0. 25 pico­curies. Evacuated 130 ml cells are filled with air bubbled through 130 ml of sample and the alpha activity determined with the counter. Relative radon and/or thoron concentrations in soil emanations were measured on site with the same instrument using a slightly modified cell. These tests take about 3 to 5 minutes and are carried out by inserting a fritted tube into a hole punched in the ground, pumping air from the hole into the cell with a rubber bulb, and measuring the alpha activity of the air with the counter.

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