Radon Progeny Concentrations Research Articles

Analysis of outdoor radon progeny concentration measured at the Spanish radioactive aerosol automatic monitoring network

An analysis of 10-year radon progeny data, provided by the Spanish automatic radiological surveillance network, in relation to meteorology is presented. Results show great spatial variability depending mainly on the station location and thus, the surrounding radon exhalation rate. Hourly averages show the typical diurnal cycle with an early morning maximum and a minimum at noon, except for one mountain station, which shows an inverse behaviour. Monthly averaged values show lower concentrations during months with higher atmospheric instability.

Study of Radon Progeny Distribution and Radiation Dose Rate in the Atmosphere

The absorbed dose rate in air of airborne gamma-rays and the concentration of radon progeny in surface air have been observed continuously in Maizuru, Japan. When data observed on fine days were plotted, with dose rate as ordinate and concentration as abscissa, these points traced with a lapse of time illustrated an anticlockwise looping for each day. This result suggests that the variation of absorbed dose rate lags behind that of concentration of radon progeny; this is due to the delay time incurred as the concentration level gradually varies from ground surface to upper air. Radon progeny concentrations in precipitation and in surface air have been observed there in order to study the relationship between the two concentrations and the influence of precipitation patterns on the concentration in precipitation. Results obtained from analysis of the observed data suggest that radon progeny in precipitation originate mainly from scavenging within the cloud (rainout) and not from that below the cloud (washout).

Measurements of thoron and radon progeny concentrations in Beijing, China

It has been reported that thoron levels in China are above the world average and maytherefore make a significant contribution to the natural background radiation dose. Wetherefore conducted a pilot study of concentrations of both thoron and radon progeny duringthe spring of 2006 in the Beijing area, China. A new type of portable 24 h integratingmonitor with a CR-39 detector was used during the survey. Seventy dwellings and eightoutdoor sites were measured during the survey. For country houses built of red bricks andslurry, the average equilibrium equivalent concentrations (EEC) of thoron and radon were1.02 ± 0.48 and 16.41 ± 9.02 Bq m−3, respectively, whereas for city dwellings built of cement blocks and floor slabs, the results were0.48 ± 0.47 and 11.50 ± 6.99 Bq m−3 for thoron and radon, respectively. For outdoor air, concentrations of thoron and radon progeny were0.29 ± 0.28 and 7.05 ± 2.68 Bq m−3, respectively. Radiation exposures from thoron and radon progeny were alsoevaluated; the ratio of dose contribution from thoron progeny to that of radonprogeny was evaluated to be 28% and 17% in country houses and city dwellings,respectively.

Retrospective radon progeny measurements through measurements of 210Po activities on glass objects using stacked LR 115 detectors

A stacked LR 115 detector consisting of two active layers was proposed for determining 210Po activity in glass surfaces after deposition of short-lived radon progeny. The sensitivities of both active layers were calculated. Two glass samples were exposed in a chamber to determine the experimental calibration factors for the radon gas and progeny, which were then compared with the theoretical calibration factors from simulations. The experimental and the simulated calibration factors for radon progeny agreed well. The discrepancy between the calibration factors for radon gas was due to a much higher equilibrium factor used in the experimental calibration than the nominal value assumed in the simulation. A mini-survey of contemporary and retrospective radon progeny concentrations was carried out at 10 residential sites. A relationship between contemporary and retrospective radon progeny concentrations was not readily observable.

Radon daughters’ concentration in air and exposure of joggers at the university campus of Bangalore, India

The concentration of radon daughters in outdoor air was measured continuously from January 2006 to December 2006 near the Department of Physics, Bangalore University campus, Bangalore. The concentration was measured by collecting air samples at a height of 1 m above the ground level on a glass micro fibre filter paper with a known air flow rate. The results show that the radon progeny concentration exhibits distinct seasonal and diurnal variations that are predominantly caused by changes in the temperature gradient at the soil–atmosphere interface. The concentration was found to be high from 20.00 to 8.00 hrs, when the turbulence mixing was minimum and low during the rest of the time. In terms of the monthly concentration, January was found to be the highest with September/August being the lowest. The diurnal variations in the concentrations of radon progeny were found to exhibit positive correlation with the relative humidity and anti-correlation with the atmospheric temperature. From the measured concentration, an attempt was made to establish the annual effective dose to the general public of the region and was found to be 0.085 mSv/a. In addition, an attempt was also made for the first time to study the variation of inhalation dose with respect to the physical activity levels. Results show that in the light of both the effect of chemical pollutants and radiation dose due to inhalation of radon daughters, evening jogging is advisable.

Equilibrium factor determination using SSNTDs

The proxy equilibrium factor F p was recently proposed by Nikezic et al. [2004. Theoretical basis for long-term measurements of equilibrium factor using LR 115 detector. Appl. Radiat. Isot. 61, 1431–1435] and Yu et al. [2005. Long-term measurements of radon progeny concentrations with solid state nuclear track detectors. Radiat. Meas. 40, 560–568] for long-term passive monitoring of the equilibrium factor F for short-lived 222Rn progeny. In the present paper, we further look into the details for the F p method and study the potential factors affecting the measurements of F using this technique. These factors include (1) the removed active layer of the LR 115 detector, (2) the presence of 220Rn in the ambient environment, and (3) the deposition of dust particles on the LR 115 detector. The corresponding results are: (1) the removed active layer thickness of the LR 115 detector is a very critical parameter in determining F p and hence F ; (2) the presence of thoron in the ambient environment will affect the track densities on the bare LR 115 detector but can be corrected for using the partial sensitivities to thoron; and (3) deposition of dust particles on the bare LR 115 detectors normally will not have significant effects. In addition, a mini-survey of radon and thoron gas concentration and the radon equilibrium factor in different indoor environments has been carried out in different seasons. The conclusion is that the use of an assumed constant F value can result in inaccurate determinations of the effective dose; therefore, actual (long-term) measurements of the F values should be made.

Variation of indoor radon progeny concentration and its role in dose assessment

Instantaneous measurements of equilibrium equivalent concentration of radon (EEC Rn) were taken over a period of 1 year in 2004 in a typical house at Amritsar city, located in the northwest part of India. A method based on absolute beta counting subsequent to grab aerosol sampling was used. During that year, EEC Rn varied between 1.56 Bq m −3 and 22.77 Bq m −3 with average value of 8.76 Bq m −3. EEC Rn decreased with the transition from winter to summer and vice versa, having a negative correlation with outdoor temperature. The use of mechanical ventilation, under normal living conditions during summer, caused an extra decrease in the concentrations. The variations with temperature and mechanical ventilation are discussed. Some major issues related to the uncertainties in dose calculations caused by the lack of knowledge of equilibrium factor and ignoring the effect of life style on the radon and its progeny concentrations are discussed.

Assessment of nanoparticle surface area by measuring unattached fraction of radon progeny

A number of studies on the exposure of nanometer aerosols have indicated that health effects associated with low-solubility inhaled particles in the range of 1–100 nm may be more appropriately associated with particulate surface area than mass concentration. Such data on correlation between number, surface area and mass concentration are needed for exposure investigations, but the means for measuring aerosol surface area are not readily available. In this paper we propose a method for particle surface area assessment based on a new approach, deposition of the “unattached fraction of radon progeny” onto nanometer aerosols. The proposed approach represents a synthesis of: (1) Derived direct analytical correlation between the “unattached fraction” of radon progeny and surface area particle concentration in the range of 1–100 nm particle diameter; (2) Experimental data on correlation between the unattached fraction of radon progeny and particle surface area for particles with diameter in the range of 44 nm–2.1 μm.

Time-integrated monitoring of radon progeny around a closed uranium mine in Japan

The practical application study of a time-integrated radon progeny monitor developed by the authors was carried out in and around a closed uranium mine site during several years. The validity of the monitoring with the monitor was confirmed by good agreement with the other monitoring results and our previous investigations. Radon progeny concentrations were almost at same level outside the site and were within the range of those at controls. The fact shows directly the effect of the mine site on the effective dose to people in outside region is negligible. The F value outdoors in rural area around Ningyo-toge is approximately 0.4 on the whole, while the lower values were observed on the site or near the site, and the higher values, closer to 0.6 in UNSCEAR reports, were observed in the large population areas.

Modelling radon progeny concentration variations in thermal spas

Radon and its short-lived progenies (218Po, 214Pb, 214Bi and 214Po) are well known radioactive indoor pollutants identified as the major radiation burden component of the thermal spa users. Monitoring of short-lived progeny concentration is of great importance for short-term dose estimations both for bathers and working personnel. A prediction model of the short-lived progeny concentration variations was developed and applied on published data of the thermal spas of Lesvos Island. The physical procedures involved were modeled in a set of differential equations describing radon progeny concentration variations on the basis of radon measurements. Published daughter data were fitted on model predictions adjusting non-measured parameters, e.g. attachment and deposition rate constants for attached and unattached progenies. Attachment rate constants were estimated between 50 and 200 h-1 while the deposition rate constants between 0.25 and 5 h-1 for attached progenies and 0.5 and 170 h-1 for the unattached ones. In addition, unattached 218Po, 214Pb and 214Bi progenies were found to be shifted forward in respect to radon approximately 0.001 h, 0.05 h and 0.40 h respectively, while attached 218Po, 214Pb and 214Bi progenies 0.05 h, 0.45 h and 0.65 h respectively.

Micrometeorological influences and surface layer radon ion production: Consequences for the atmospheric electric field

Variation of surface electric field with special thrust to atmospheric inversion condition is studied for the tropical station Pune (18°32′N, 73°51′E, 550 m ASL) for the year 1993 considering average meteorological conditions. The study aims to understand the relative effect of space charge density variation modulated by vertical temperature gradient (lapse rate) Vs conductivity variations controlled by radionuclide concentration on modification of electric field close to surface. Electric field is predominantly controlled by lapse rate (space charge density variation) and radon progeny concentration (conductivity modification) in summer and winter respectively. An empirical relation developed elsewhere is evaluated for the present observations.

Analysis Of The Natural Radon ProgenyContribution To Radioactive Aerosol MonitoringIn The Automatic Spanish Surveillance Network

Continuous monitoring of radioactive pollutants in the air is provided by environmental radiological surveillance networks. In Spain, continuous and automatic control is carried out by the REA network, which comprises a set of 25 automatic stations. Most of these stations are run together with meteorological stations, belonging to the Spanish Meteorological Institute. The monitor for measuring the artificial radioactive aerosol concentration is the BAI 9850 from Berthold Company. An important contribution to the uncertainty of its measurements is due to natural air radioactivity, mainly from radon progeny. A statistical study using the data from the REA and the INM radiological and meteorological stations has been carried out in order to characterize the natural radioactivity at each station and to improve the quality of the artificial radioactivity air concentration measurements. This study shows that natural radioactivity concentration varies both daily and seasonally, and is significantly correlated to meteorological parameters and the geological properties of station surroundings. Radon progeny concentration commonly shows a daily cycle with a maximum in the early morning and a minimum in the afternoon, according to the behaviour of meteorological parameters. However, at a station situated at a higher altitude, the radon progeny pattern is completely different, due to the evolution of the planetary boundary layer above this complex terrain. Stations have been classified into coastal, inland and mountain according to the behaviour of the natural radioactivity at each location. A representative station from each category has been selected and a simulation study is being carried out using the MM5 code coupled with the atmospheric transport code FLEXPART.

Continuous monitoring of 222Rn and its progeny at a remote station for seismic hazard surveillance

An experimental station to monitor variations in radon and radon progeny concentrations in the gases from the thermal springs at Bakreswar, West Bengal, India has been installed. This is essentially a part of a continuous, automated, multi-parametric geochemical monitoring system (GMS) installed with a view to detect probable earthquake-related precursory changes in the spring gas emanations. The entire data acquisition system is computer driven and fully automated. Instrument readings acquired over a 24-h interval are transmitted through a tele-link facility from the field laboratory located at the thermal spring site situated about 250 km away, once a day, to a workstation at our Centre in Kolkata for analysis and storage. After the system was installed during mid-December, 2004, concurrent anomalous changes in concentration profiles of 222Rn, 218Po and 214Bi occurred beyond 2 σ level four times during the period of present observation duration up to February 04, 2005. The monitored anomalies may be attributed to precursory dilatation responses arising due to earthquakes that had occurred subsequently in Indonesia and the Andaman and Nicobar Islands. The observed variations reveal evidence of pre-seismic radioactive heterogeneities in escaping subsurface fluids from the monitored thermal spring gases.

INDOOR-ATMOSPHERIC RADON-RELATED RADIOACTIVITY AFFECTED BY A CHANGE OF VENTILATION STRATEGY

The present author has kept observation for concentrations of atmospheric radon, radon progeny and thoron progeny for several years at the campus of Fukushima Medical University. Accidentally, in the midst of an observation term, i.e., February 2005, the facility management group of the university changed a strategy for the manner of ventilation, probably because of a recession: (I) tidy everyday ventilation of 7:30-24:00 into (II) shortened weekday ventilation of 8: 00-21 : 00 with weekend halts. This change of ventilation manner brought a clear alteration for the concentrations of radon-related natural radioactivity in indoor air. The present paper concerns an investigation of the effect of the ventilation strategy on the indoor-atmospheric radon-related radioactivity.

An intercomparison between gross α counting and gross β counting for grab-sampling determination of airborne radon progeny and thoron progeny

The instantaneous values of the airborne activity concentrations of radon progeny and thoron progeny have been determined 34 times in a closed and windowless room in a cellar using two independent grab-sampling methods in order to compare the performance of the methods. The activity concentration of radon ( 222Rn) was also measured and it varied between 200 and 650 Bq m −3. Two samples of radon and thoron progeny were collected simultaneously from roughly the same air volume by filtering. For the first method, the isotopes were collected on membrane filter and gross α counting was applied over several successive time intervals. This method was a slightly improved version of the methods that are applied generally for this reason for decades. For the second method, the isotopes were collected on glass-fibre filter and gross β counts were registered over several time intervals. This other method was developed a few years ago and the above series of measurements was the first opportunity to make an intercomparison between it and another similar method based on α counting. Individual radon progeny and thoron progeny activity concentrations (for the isotopes 218Po, 214Pb, 214Bi and 212Pb) were evaluated by both methods. The detailed investigation of the results showed that the systematic deviation of the methods is small but significant and isotope-dependent. The weighted averages of the β/α activity concentration ratios for 218Po, 214Pb, 214Bi, EEDC 222 (Equilibrium-Equivalent Decay-product Concentration of radon progeny) and 212Pb were 0.99±0.03, 0.90±0.02, 1.03±0.02, 0.96±0.02 and 0.80±0.03, respectively. The source of the systematic deviation is probably the inaccurate knowledge of the counting efficiencies mainly in the case of the α-counting method. A significant random-type difference between the results obtained with the two methods has also been revealed. For example, the β/α ratio for EEDC 222 varied between 0.81±0.01 and 1.22±0.03, where the errors derive from the random errors of the independent β and α results. The detailed investigation of the results showed that the α method is responsible for the overwhelming part of this random deviation that was caused mainly by the lower accuracy, stability and reliability of this method. The performance of the β method proved to be better mainly because of its higher accuracy, stability and reliability.

Measurements of radon, thoron and their progeny in Gifu prefecture, Japan

Due to the rocky neighborhood, consisting of mostly granite with high radium content, an elevated radon concentration was found in a territory of Gifu prefecture situated in the middle of Japan. Radon concentrations in water were measured and were found to be considerably high. Since indoor radon and radon progeny concentrations might be relatively high, their concentrations were also analyzed. Besides the radon and radon progeny, thoron and thoron progeny concentrations were also investigated. Dose estimations for radon and thoron in indoor air are discussed.

Long-term measurements of radon progeny concentrations with solid-state nuclear track detectors

In this paper, we review existing methods for long-term measurements of radon decay products with solid-state nuclear track detectors. We then propose a method to determine the equilibrium factor using the bare LR 115 detector. The partial sensitivities p i of the LR 115 detector to Rn 222 and its α -emitting short-lived progeny, Po 218 and Po 214 , were investigated. We determined the distributions of lengths of major and minor axes of the perforated α -tracks in the LR 115 detector produced by Rn 222 , Po 218 and Po 214 through Monte Carlo simulations. The track parameters were first calculated using a track development model with a published V function, and by assuming a removed active layer of 6.54 μ m . The distributions determined for different α -emitters were found to be completely overlapping with one another. This implied equality of partial sensitivities for radon and its progeny. Equality of partial sensitivities makes convenient measurements of a proxy equilibrium factor F p possible which is defined in the present work as ( f 1 + f 3 ) and is equal to the ratio between the sum of concentrations of the two α -emitting radon progeny ( Po 218 + Po 214 ) to the concentration of radon gas ( Rn 222 ) . In particular, we have found F p = ( ρ / ρ i tC 0 ) - 1 , where ρ (track/m 2) is the total track density on the detector, ρ i = 0.288 × 10 - 2 m (for the V function mentioned above and for a removed active layer of 6.54 μ m ), t is the exposure time and C 0 (Bq/m 3) is the concentration of Rn 222 . If C 0 is known (e.g., from a separate measurement), we can obtain F p . The proxy equilibrium factor F p is also found to be well correlated with the equilibrium factor between radon gas and its progeny through the Jacobi room model. This leads to a novel method for long-term determination of the equilibrium factor. Experimental irradiation of LR 115 detectors to known Rn 222 concentrations as well as known equilibrium factors were carried out to verify the present method. The relationship between ρ i and the removed layer was then derived for the V function specifically determined for the LR 115 detectors we were using for the experiments. The actual removed layers for individual detectors after etching were measured accurately using surface profilometry. A curve showing the relationship between the removed layer and the track diameter of normally incident 3 MeV α -particles is also provided for other researchers, who do not have access to surface profilometry, to use the present technique conveniently.

Study on radon and radon progeny in some living rooms

In the first part of this work, the potential alpha energy concentration (PAEC) of radon progeny, the equilibrium factor (F), the activity concentration of 222Rn gas (Co) and the unattached fraction (fp), were determined in 15 living rooms at El-Minia City, Egypt. The activity size distribution of (214)Pb was measured by using a low pressure Berner impactor. Based on the parameters of that distribution the total effective dose through the human lung was evaluated by using a dosimetric model calculation of ICRP. An electrostatic precipitation method was used for the determination of 222Rn gas concentration. The mean activity concentration of 222Rn gas (Co) was found to be 123 +/- 22 Bq m(-3). A mean unattached fraction (fp) of 0.11 +/- 0.02 was obtained at a mean aerosol particle concentration (Z) of (3.0 +/- 0.21) x 10(3) cm(-3). The mean equilibrium factor (F) was determined to be 0.35 +/- 0.03. The mean PAEC was found to be 37 +/- 8.1 Bq m(-3). The activity size distribution of (214)Pb shows mean activity median diameter of 290 nm with mean geometric standard deviation (sigma) of 2.45. At a total deposition fraction of approximately 23% the total effective dose to the lung was determined to be approximately 1.2 mSv. The second part of this paper deals with a study of natural radionuclide contents of samples collected from the building materials of those rooms under investigation given in part one of this paper. Analyses were performed in Marinelli beakers with a gamma multichannel analyser provided with a NaI(Tl) detector. The samples have revealed the presence of the uranium-radium and thorium radioisotopes as well as (40)K. Nine gamma-lines of the natural radioisotopes that correspond to 212Pb, 214Pb, 214Bi, 228Ac, 40K and 208Tl were detected and measured. The activity concentrations of 226Ra, 232Th and 40K were determined with mean specific activities of 65 +/- 22, 35 +/- 12 and 150 +/- 60 Bq kg(-1), respectively. These activities amount to a radium equivalent (Ra(eq)) of 126 Bq kg(-1) and to a mean value of external hazard index of 0.34.

Temperature variation of indoor and outdoor radon progeny

Abstract The indoor and outdoor radon progeny concentrations were investigated at a semi-hilly area of Pathankot in Punjab using the method of beta particle counting of aerosol samples collected on a glass micro-fiber filter. A linear relation was found between indoor and outdoor equilibrium equivalent concentrations of radon-222 (EECRn) with correlation coefficient of R = 0.9 . The indoor and outdoor EECRn levels were also studied as a function of outdoor temperature. The variations with temperature in both cases showed negative correlation with correlation coefficient of R = - 0.66 and R = - 0.73 , respectively. The ratio of outdoor to indoor EECRn investigated as a function of absolute difference of indoor and outdoor temperatures (|Tin–Tout|) resulted in a correlation coefficient of R = 0.52 , which is positive. The indoor EECRn was also estimated from an empirical relation based on transport of inside and outside radon progeny through ventilation. The measured inside EECRn agrees well with the computed value.

A pilot survey on indoor radon and thoron progeny in Yangjiang, China

A pilot survey on indoor radon and thoron progeny concentration was carried out in five villages in HBRA of Yangjiang and one village in the controlled area(CA) in March 2004. Totally 26 adobe houses and 29 brick houses in HBRA were investigated. A portable 24-h integrating monitor with CR-39 detectors was adopted for progeny measurements, and the average equilibrium equivalent 222Rn and 220Rn concentrations (EEC Rn and EEC Tn) were obtained. Rather high levels of EEC Rn and EEC Tn with an average of 57.1±33.3 and 12.6±9.5 Bq·m −3, respectively, were observed in adobe houses. In addition, 222Rn/ 220Rn concentrations and exhalation rate were also measured by an Electrostatic-Radon-Sampler (ERS-2) monitor.