Radon Exhalation from the Ground

Abstract

The Induction method is modified and applied to the measurement of radon exhalation from the ground. Equations for the build-up and decay of products on the collecting wire are derived, and these are accompanied by appropriate graphs. The decay of products is detected by a mesh cylindrical ion chamber incorporated about the collecting wire, together with a Lindemann electrometer. The system has an overall efficiency of 29% when considering radium A collection. Measurements were taken from June to August 1955. An attempt is made to correlate the results with meteorological data, and they are compared with those of previous investigators. The average, maximum and minimum values (x10⁻¹⁸ curies cm⁻² sec⁻¹) observed are: 1.1, 3.2, 0.38. A diurnal variation in exhalation rate and background ionisation was observed. The radon to thoron ratio was extremely high, being about 1.5. Atmospheric radon content values are included. The method used here is more suitable for large area sampling than is convenient with the methods of previous investigators. However, the absolute values are only approximate because of variations being superimposed on a long term build-up of activity.