Dynamics of Radon Emission from the Adits of the Former Uranium Mine on the Mount Beshtau

Abstract

This article presents the results of monitoring measurements of radon concentration in the air, the gamma dose rate, as well as the velocity and direction of air movement at the adit mouths of the former Beshtaugorsky mine No.1 (Mount Beshtau). The data obtained indicate the very powerful seasonal radon anomalies at the adit mouths associated with the periodic release of mine air from the tunnels into the atmosphere. During mine air discharge, radon concentrations in the open atmosphere locally around the adit mouth reach 594,685 Bq/m3, averaging 50000 – 250000 Bk/m3. The equivalent equilibrium concentration of radon in the air ranges from 1600 to 80000 Bq/m3. The release of significant concentrations of radon and its progeny leads to significant increase in the dose rate of gamma radiation locally around the adit mouth to values of 1–18 mSv/h. This means that abandoned adit mouths are objects of increased radiation risk. Comparison of the results of measurements of radon concentration at the adit mouths and in the zone of a natural radon anomaly associated with a tectonic fault shows that radon emissions in both cases are caused by a single process – air circulation in permeable zones of the rock massif due to the temperature difference between the mountain range and the atmosphere.