EFFECT OF VARYING UNATTACHED FRACTION OF RADON DAUGHTERS ON THE MEASUREMENT OF THE EQUILIBRIUM FACTOR USING NUCLEAR ETCHED TRACK DETECTORS

The equilibrittm factor is derived from the measured activity concentr ations of radon and its daughters on the basis of a balance equation f or the different components in air. For this approach, assumptions on the unattached fraction of radon daughters are needed. For Po-218 the numerical evaluation is frequently based on a fixed value of 0.1 for P o-218. Be actual unattached fraction of Po-218, however, can vary betw een 0.05 and 0.4. The uncertainty of the equilibrium factor is the tak ing into account this variation. For the determination of the equilibr ium factor two concepts of long-term measurement with nuclear etched t rack detectors are compared, namely the conventional difference method for estimating the total activity concentration of Po-218 and Po-214 from the readings of an open and filtered radon diffusion chamber as w ell as a new method based on the separate measurement of the activity concentration of Rn-222 and Po-214 only. Taking into account the uncer tainties of estimating the equilibrium factor conclusions are drawn on the suitability of both methods for practical use.