A SIMPLE PASSIVE COLLECTOR FOR DIRECT MEASUREMENT OF RADON FLUX FROM SOIL

A simple technique for measurement of the soil-atmosphere radon flux h as been developed by fastening a charcoal canister inside a PVC cylind rical container. This device, which is deployed at the ground surface for approximately 16 hours, captures radon emanating from the soil by adsorption onto the charcoal surface. After recovery of the canister a nd measurement of the radon daughter activity on a NaI detector, the r adon flux may be calculated if the adsorption efficiency of radon onto the charcoal is known. This parameter was determined by exposure of c harcoal canisters to Ra-226-spiked barium palmitate filter sources for timed intervals. Since this compound is known to emanate 100% of the Rn-222, generated during radium decay, it forms a useful ''flux standa rd.'' The accuracy of our flux measurements was assessed by comparison to a more established technique, the enclosed-chamber or ''accumulato r'' method. Concentration measurements were made for the chamber over a less than 2-hour period while the canister flux measurements were ba sed on single overnight deployments. The experiment was repeated 5 tim es at two different sites and the two techniques generally agreed with in a 95% confidence interval.