Integrated radon mapping in the earth—Assessment of the 220Rn signal and its exclusion

Abstract

In many searches for uranium in the earth by mapping alpha decay activity from [Formula: see text], there is a background of [Formula: see text] activity due to thorium. Both sources of activity are measured, unless special measures are taken to exclude the alpha particles from [Formula: see text] decay. Laboratory experiments and field observations are used to demonstrate that the signal including [Formula: see text] activity is commonly about twice that from [Formula: see text] activity alone, but that the [Formula: see text] activity ratio can vary widely. Use of anti‐ [Formula: see text] membranes is, therefore, important in making meaningful surveys of [Formula: see text] activity. In some cases, anomalously high field readings arise from unusually high local radon emanation. These cases can be recognized by high [Formula: see text] activity measured in the laboratory using separate soil samples from each site used for a reading in the field.