Sensitivity of a Combined Charcoal and Etched Track Technique for 222Rn

Abstract

<jats:title>Abstract</jats:title> <jats:p>To describe the radon detection process of a new radon dosemeter, which is based on the simultaneous utilisation of activated charcoal and CR-39 etched track detector, a simple model was formulated. The dependence of the response of the dosemeter on exposure time, irradiation time of the detector foil, thickness of the charcoal layer, diffusion and the adsorption coefficients of radon in charcoal was calculated. The theoretical model was verified by experiments. It was found that for a short (one hour) exposure to a radon atmosphere the response can be as high as (900 tracks.cm-2.(kBq.m-3)-1.</jats:p>

Radon Monitoring Devices Based on Etched Track Detectors

“…To study the response of the charcoal collector sampler, a simple model of the detection process in the technique based on the utilization of etched track detectors and activated charcoal was developed (Sutej, 1994). Activated charcoal is a term used to describe mate rials that exhibit a high degree of porosity and extremely large surface area (Scarpitta and Harley, 1990).…”

“…During activation, or heating in the absence of oxygen, both macropores and micropores are created in the solid matrix of the starting material. Radon activity in air, diffusion coefficient for radon in charcoal, adsorption coefficient, and density of the charcoal are denoted by A ot D c , k, and p c respectively (adapted from Sutej, 1994). Equilibrium adsorption of radon by charcoal can be described by (Sutej, 1994) A c = kp c A 0 (2.2.18) where A c and A 0 are the activity concentrations of radon in the charcoal and in the air (Bq m~3), k is the adsorption coefficient (cm 3 g _1 ) and p c is the density of the charcoal (g cm" 3 ).…”

“…A one-dimensional approximation to the diffusion process governed by Fick's law and the decay law is (Cohen and Cohen, 1983;Sutej, 1994) dA c n d 2 A c ,…”

“…The approximate solution for t << A 0 _1 and x « JD C /X 0 is (Sutej, 1994) A c (x,t -> 0) = k Pe A" 1-er/lJ^j (2.2.20)…”