Radon Exposures of Miners at Small Underground Construction Sites in Old Mining: Recommendations to Improve Radiation Protection Measures by the Saxon Radiation Protection Authority

The Ore Mountains (Erzgebirge) and Vogtland are low-mountain regions in the East German state of Saxony. Here, silver deposits were found in 1168. Mining began shortly after, continues at varying intensity to this day, and has left numerous galleries and shafts. Today, eight companies with about 250 miners carry out maintenance at more than 40 small and frequently changing underground construction sites throughout the year. Miners are protected against high radon exposure by radiation protection measures such as ventilations, stoppings made of wood, foil, and expanding foam, and staff rotations. However, some of them still show high annual exposure levels; for example, in 2015 up to 14.4 mSv measured by passive radon dosimeters. Reasons for this include the high radon potential in old mining and the natural density driven mine air current through the galleries. Mine air currents can change directions during the day depending on outdoor temperatures. This paper presents the experiences of the Saxon Radiation Protection Authority in monitoring miners in old mining. For this purpose, the paper looks at seven examples of miners’ critical exposures based on measurement curves of radon activity concentration and derives respective radiation protection measures. These encompass, for example, to activate mine fans, erect stoppings, extend ventilation pipes, and change the locations of mine fans. Conclusions are drawn for the operative and strategic radiation protection in old mining.