[en] The diffusion coefficients of neutral unattached RaA in aerosolfree air have been measured at various relative humidities. Over the range of relative humidities of 10 to 50%, the diffusion coefficients of neutral unattached ²¹⁸Po particles were almost the same, that is, the diffusivity seemed to be independent of the amount of water in air. Although the measured values of the diffusion coefficient (0.042-0.050 cm² sec^-1) were in agreement with those of some previous investigations, the relative humidity dependence, previously reported by some investigators, was not observed. The obtained results clearly show that unattached ²¹⁸Po particles are not a single particle, but rather somewhat massive ones. (orig.)

[en] Abstract only

[en] The results of the experimental investigations on quantitative evaluation of the ²¹⁸Po and ²¹⁴Bi washout efficiency by fog in an aerosol chamber are presented. The radioactivity has been measured by means of α-spectrometric method. Comparison of eXperimental and calculated data is made. The ²¹⁸Po and ²¹⁴Bi washout efficiency ratio is found to be dependent mainly on the aerosol concentration. The change of ²¹⁸Po concentration imitates the process of coagulation of free atoms of light ions, and that of ²¹⁴Bi - of aerosol particles by fog droplets

[en] The correlation between the surface area of aerosols and unattached fraction of ²¹⁸Po was studied and a simple relationship determined. A method is here proposed to measure small concentrations of aerosol particles, based on this correlation. This method offers an improvement in the uncertainties associated with detection of small aerosol concentrations because it relies on the detection of alpha particles, which can be done with low detection limits. (author)

[en] The prompt radon detection method in finding buried uranium ore bodies, ²¹⁸Po method, is presented. The author describes the working principles, features and exploration results of this method, and also explains the possibility of finding buried uranium ore bodies by means of ²¹⁸Po method. In the end, the author lays emphasis on the interpretation method for data obtained from ²¹⁸Po measurement. Through field testing, the author considers that the ²¹⁸Po method can be used not only in finding buried uranium ore bodies but also in predicting quantitatively the dimension and depth of buried ore bodies

[en] A simple method was developed for determining the unattached fraction of ²¹⁸Po in a radon chamber. The method requires only measurement of the total ²¹⁸Po concentration, from which the unattached fraction of ²¹⁸Po is determined by use of an equation. The method was tested by performing experiments in a radon chamber. In each of the experiments, the unattached fraction, determined independently by the wire screen method, agreed well with those calculated by the simple method based only on total ²¹⁸Po concentration. (author)

[en] Radon exhalation rate is crucial in the estimation of radiation risk from various materials. RAD7 only focus on the count of the ²¹⁸Po in sniff mode, and is well suited to measure radon exhalation rates. This paper presents a fast method for measuring radon exhalation from medium surface with a ventilation-type accumulation chamber by the RAD7 while making the effects of leakage and back diffusion negligible. The radon exhalation rate can be obtained from the measured values before radioactive equilibrium between Radon and progeny occurs. This method is based on the principle for tracing radon concentration changes by deriving ²²²Rn concentrations through ²¹⁸Po measurements. Several radon exhalation rate measurements of medium surface have been performed in the Radon Laboratory of the University of South China. The radon exhalation rates obtained by verification experiments are within the accepted values for the reference value. - Highlights: • We present a method for measurements of radon exhalation from the medium surface in open loop. • The real radon concentration of ventilation-type accumulation chamber can be obtained by correction algorithm. • The radon exhalation rate can be obtained by nonlinear or linear least squares fitting. • This method can be applied for develop the portable instrument

[en] Highlights: • Experimental and theoretical calibration of CR-39 and Makrofol detectors were done. • V function for Makrofol was presented. • Previously developed software was modified to enable Makrofol calibration. • Optimisation of chamber and detector dimensions was theoretically performed. This paper presents experimental and theoretical determination of CR-39 and Makrofol calibration coefficients in diffusion chambers for radon measurements. Experimental calibration was performed by irradiation of detectors in a calibration chamber; radon concentration in the chamber was continuosly measured by RAD7 device. Calculations were performed by the previously developed software for CR-39 detector. In addition the software was modified to enable calculation for Makrofol by implementing V function and other relevant data for this kind of detector. A good agreement was found between experimental and theoretical approaches. The comparison enabled selecting V function for CR-39 that gave the best agreement with the experimental results. Optimisation of chamber and detector dimensions was theoretically performed for different etching times. The dependence of calibration coefficient on ²¹⁸Po deposition fraction was also analysed.

[en] A number of investigators have reported the formation of the radiolytic ultrafine particles produced by the interaction of ionizing radiation with water vapor. Previous studies have suggested that a very high localized concentration of the OH radical produced by the radiolysis of water can react with trace gas like organic vapors and produce lower vapor pressure compounds that can then nucleate. In order to determine water vapor and trace gas dependence of the active, positive-charged, first radon daughter, an experiment was conducted using a radon chamber. The activity size distribution of the radon daughter in the range of 0.5 - 100 nm was measured using the stacked wire screens sampler. Measurements were taken for different relative humidity. The resultant activity size distributions were analyzed. The addition of water vapor to the radon carrier gases resulted in the formation of ultrafine particles by OH radicals formed radon radiolysis. It may be due to the neutralization of charged Po-218 ion with water vapor through the radiolysis

[en] In this paper, we have reported ionization rate calculated from the Radon and its progeny is closely representing the derived ionization rate from Ion-Aerosol Equilibrium equation. We derived the concentration of small ions from the ionization rate from radon and its progeny and results shows good agreement of the concentration of small ions from direct measurement from NAIS (Neutral Air ion Spectrometer). The ionization rate at this tropical station shows minima in the afternoon and maxima in the early morning. Also examined the variation of ionization rate with the meteorological parameter. At lower layers of the atmosphere, ionization is mainly due to the radiations emitted by radon and its decay products. Short-lived daughters of radon ("2"1"8Po, "2"1"4Pb, "2"1"4Bi and "2"1"4Po) are electrically charged and are chemically reactive. So we have calculated the conductivity of the atmosphere. The observed conductivity shows a maximum values in small ions. A mean ± Standard deviation value of Conductivity varies 2.90 ± 1.73, 4.77 ± 1.58, 2.93 ± 1.50, 8.54 ± 3.23, 6:19 ± 2.72 for small, big cluster, and intermediate, light large and heavy large ions respectively. The conductivity varies from 1.23 x 10"-"9 to 8.50 x 10"-"9 for small ions, 2.59 x 10"-"1"0 to 8.36 x 10"-"1"0 for big clusters ions, 1.46 x 10"-"1"0 to 7.52 x 10"-"1"0 for intermediate ions, 4.68 x 10"-"1"1 to 1.91 x 10"-"1"1 for light large ions, 6.20 x 10"-"1"1 to 1.36 x 10"-"1"0 per ohm per meter. (author)