Response of CR-39 Polymer Radon-Sensors via Monte-Carlo Modelling and Measurements

Abstract

International studies of radon indoors and in workplaces have shown significant radiation dose burden of the general population due to inhalation of radon (222Rn) and its short-lived progeny (218Po,214Pb, 214Bi, 214Po). As far as atmospheric radon concerns, 222Rn, is not necessarily in equilibrium with its short-lived progeny. For this reason, radon’s equilibrium factor F was solved graphically as a function of the track density ratio R=TB/TR, namely of the ratio between the recordings of cup-type and bare CR-39 detectors. TB was computed through special Monte-Carlo codes which were implemented for the calculation of the efficiency of bare CR-39 polymers, regarding their ability in sensing the alpha particles emitted by the decay of radon and its short-lived progeny. For a realistic approach, Monte-Carlo inputs were adjusted according to actual experimental concentration measurements of radon, decay products and F of Greek apartment dwellings. Concentration measurements were further utilized for the calculation of the unattached fraction, fp, in terms of Potential Alpha Energy Concentration (PAEC, defined as the sum of the initial - per volume - energies of all alpha particles emitted due to the decay of radon and its short-lived progeny that are present within a certain amount of air). This was employed for the calculation of F in terms of ratio (A4/A0), where Ai represents the activity concentration of radon (i=0) and 214Po (i=4) respectively. Measured and calculated values of F were plotted versus R. The results were fitted and checked with model’s predictions.