α-Spectroscopy on CR-39 track detectors for the dosimetry of radon daughters

Abstract Long-term radon daughter concentration detection is of great interest in lung dose studies. An automatic image analysis system to carry out α-spectroscopy by tracks analysis on CR-39 (allyl diglycol carbonate) detectors was developed. Identification and separation of 222 Rn, 218 Po, and 214 Po contributions to the α-tracks in CR-39 exposed inside an open dosimeter were possible using the system. The calibration of the dosimeters with regard to 218 Po and 214 Po was performed through an exposure in the National Radiological Protection Board (U.K.) radon chamber. In four houses, long-term 218 Po and 214 Po concentrations were measured by means of open dosimeters; 222 Rn levels were simultaneously assessed with permeation dosimeters. Estimates of the equilibrium factor, F, were made using theoretical equations giving F values as a function of radon daughters to radon gas concentrations ratios. Based on the most sensitive of those relations, F values varying between 0.2 and 0.5 were obtained, in good agreement with data recorded by an active Equilibrium Equivalent Concentration (EEC) detection instrument used for comparison.