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The schematic diagram of the CR-39-based direct 222
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The deposition-based direct indoor 222Rn and 220Rn progeny measurement techniques are mostly affected by the indoor environmental conditions, such as the ventilation, concentration of condensation nuclei, and reactions with the structure and its furnishings. In this study, a theoretical model of a direct 222Rn and 220Rn progeny monitor based on all...
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... direct 222 Rn and 220 Rn progeny monitor is made up of a stainless steel plate, allyl diglycol carbonate (ADC or CR-39) nuclear track detector, and aluminium-vapourized Mylar film (Fig. 1). Three thicknesses of the fi lms, viz., 7.10 mgcm -2 , 5.05 mgcm -2 , and 3.25 mgcm -2 , are selected to allow for the responding alpha energy to be higher than that emitted by the progeny 212 Po, 214 Po, and 218 Po to form the tracks on CR-39, respectively. In the behaviour of 222 Rn and 220 Rn progenies, the relationship between ...
Citations
... Deposition velocities depends on a number of environmental parameters like ventilation rate, turbulence, unattached fraction, aerosol size distribution etc. [7,8]. These make the deposition sensors site specific i.e. for each location, the progeny deposition velocities have to be established before deployment. ...
... F calculated in the section (b) at different environmental conditions and deposition flux calculated theoretically using the deposition velocity estimates model by Mishra et al. [8], ...
... Particle concentration (cm -3 ) Fig. 2 Equilibrium factor of 222 Rn as a function of particle concentration at different ventilation rates [8], were plotted against the Dose coefficients calculated from Porstendorfer [10], in Fig. 3. It was observed that F showed a scattered pattern as a function of dose whereas deposition flux showed a linear behavior. ...
Deposition based direct radon and thoron progeny sensors give a more accurate estimate of the inhalation dose due to radon and thoron. The dependence of equilibrium factor on aerosol concentration and the ventilation rates has been studied. Deposited flux represents a better index of inhalation dose. Deposition based sensors are based on deposition velocity of the progeny atoms in the environment which show variability only in extremities like very low aerosol environment or very high ventilation rates, which has been presented in this work. Wire-mesh capped deposition sensor which is based on attached fraction deposition velocity, has been studied at different particle concentrations and it can be used for such occupational environments.
... Therefore, the direct measurement technique of 222 Rn and 220 Rn progeny is desirable and necessary for the evaluation of internal indoor 222 Rn and 220 Rn exposure. 2 of 13 In the recent 20 years, a direct 220 Rn progeny measurement technique based on CR-39 detector for EEC of 220 Rn was developed and used by Zhuo and Iida [7], Tokonami et al. [8], Zhuo and Tokonami [9], Tokonami [10], Sorimach et al. [11], and Hu et al. [12]. Mishra and Mayya [13] were the first to develop the direct 222 Rn and 220 Rn progeny measurement techniques using LR-115 detector. ...
An improved passive CR-39-based direct 222Rn/220Rn progeny detector with 3 detection channels was designed and tested in this study to measure and calculate equilibrium equivalent concentration (EEC) of both 222Rn and 220Rn without the equilibrium factor. A theoretical model was established to calculate the EEC with optimization. Subsequently, an exposure experiment was carried out to test the performance of this detector, and we compared the chamber experiment and the theoretical model by estimating and measuring various parameters. The deposition flux of progeny derived from the prediction agreed well with the value measured in the exposure chamber. The energy-weighted net track density (NTD) measured by this detector is much more reliable to reflect the linear relation between NTD and time-integrated EEC. Since the detector is sensitive to the exposure environmental condition, it is recommended to apply the detector to measure the EEC after its calibration in a typical indoor environment.
