Radon-220 exhalation methodology and temporal variation in a HBRA, Fen complex

Radon and its progeny are major contributors to dose to the public. In high background radiation areas (HBRAs), the risk is increased. In the Fen igneous complex, Norway, significant outdoor levels of radon-220 (220Rn) have been observed and exhalation from the ground is a contributor. Such exhalation depends on many factors, including levels of radon-progenitors in the ground. Temporal variation in 220Rn exhalation rates is affected by weather parameters. We show large 220Rn exhalation rates at Fen complex and assess temporal variation, which is explained by weather parameters, especially by wind. Exhalation rates are calculated from measurement series in an exhalation container using different phases of accumulation. We find a bias depending on whether the linear phase of increase or the subsequent threshold phase is used, and show it is affected by whether air is sampled from the side or top valve of the container. However, in areas where progenitor levels in the ground are low, assessment of the linear phase may not be possible due to required period of measurement intervals.