Some observations of variations of the natural background radiation

Abstract

Since the middle of 1960 the ionizing radiation at some 25 pIaces in Sweden has been recorded by high pressure ionization chambers. Diagrams show how the ionization varied during October 1960. The variations (between 5 and 20% increase during 6 hours or more) are correlated to precipitation. Various factors influencing the natural radioactivity (Ra-226-series) of precipitation are discussed. From the measured additional dose contributions the average specific activity is calculated to 1.5–3·10–11 curie per gram of precipitation.