An instrument for measuring the unattached fraction of radon progeny with etched track detectors

摘要

To measure the unattached fraction of radon progeny, a new type of portable, low cost, reusable integrating monitor with etched track detector (CR-39) was developed. This monitor simultaneously gives the average equilibriumequivalent concentrations of unattached ~(222)Rn progeny (EEC~u_(Rn)), attached ~(222)Rn progeny (EEC ~a_(Rn)) and also ~(220)Rn progeny (EEC_(Tn)). It was calculated, according to the detection efficiencies which were derived by the Monte Carlo method, that the lower detection limits for EEC ~u_(Rn), EEC~a_(Rn) and EEC~(Tn) are 0.03 Bq m~(-3), 0.12 Bq m~(-3) and 0.07 Bqm~(-3), respectively for 24 h integrating sampling at a flow rate of 2.92 l min ~(-1). The validity of the new monitor was confirmed through a series of intercomparison experiments.