Two new ²²²Rn emanation sources – a comparison study

Abstract. More than 50 % of natural occurring radiation exposure of the general public is due to the noble gas radon (²²²Rn) and its progenies, causing considerable health risks. Therefore, the European Union has implemented council directive 2013/59/EURATOM to measure ²²²Rn activity concentrations and to identify Radon Priority Areas (RPAs) to specify areas where countermeasures are most needed. Although ²²²Rn measurements are far spread across Europe, traceability to the international system of units (SI) is still lacking. Consequently, measurement results cannot be reliably compared to each other. The EMPIR project 19ENV01 traceRadon aims to address this issue and has developed two new ²²²Rn emanation sources, intended to be used as calibration standards for reference instruments. The goal of this paper is to investigate and compare the two sources to ensure their quality by comparing the calibration factors estimated from both sources for the same reference instrument. This was done for three reference instruments in total at two experimental sites. Differences of calibration factors for one reference instrument of up to 0.07 were derived. Despite the small differences between the calibration factors, all uncertainties are well within the aspired target uncertainty of 10 % for k = 1.