Influence of the water temperature on measurements of Rn-222 in water by liquid scintillation counting of polycarbonates

An approach for measurement of ²²²Rn in water has been recently proposed, in which polycarbonate specimens are exposed in the water and are afterwards measured by either gamma-spectrometry, gross beta-counting or liquid scintillation counting (LSC) or etched for alpha tracks. One of the advantages of this approach is that the specimens could be exposed directly in the water source. However, the signal is influenced by the temperature of the water. This work presents results that demonstrate this temperature influence for the case of LSC measurement of the exposed polycarbonates. In addition, results for the values of the partition coefficient K (quantifying the solubility of ²²²Rn from water to polycarbonate) and the diffusion length L_D of radon in polycarbonate at temperatures which are typical for natural water sources are presented. Based on experimental results, polynomial functions are given that allow to estimate the values of K and L_D for temperatures covering most of the range met in practice. These values could further be used to apply temperature corrections to the measurement signal for any of the above measurement techniques.