Unattached Fraction Of Radon Progeny Research Articles

Wire mesh capped DRPS based bronchial dosimeter for personal inhalation dosimetry due to radon progeny

A study has been carried out to experimentally determine the calibration factor (CF) of the passive bronchial dosimeter, which consists of a direct radon progeny sensor capped with a 100-wire mesh. First, the CF was determined in controlled environmental conditions simulated in a calibration chamber. With aerosol concentrations varying from 104 p cm−3 to 105 p cm−3 and relative humidity varying from 60% to 80% in the chamber, CF was observed to be nearly constant with an average value of (3.8 ± 0.5) × 10−3 mSv tracks−1 cm2. Then, the CF was determined in real indoor environments in which it was again observed to be almost constant and the mean value was found to be (5.6 ± 0.1) × 10−3 mSv tracks−1 cm2. Pooling all the data on CFs obtained under controlled conditions and in real indoor environments, a lognormal distribution of the CF was observed with a geometric mean and geometric standard deviation of 0.0052 mSv tracks−1 cm2 and 1.28 respectively. The experimentally determined value of CF was found to be in close agreement with the theoretically estimated value, taking into consideration the unattached fraction of radon progeny. This dosimeter is passive, cheap, lightweight and, moreover, the CF being stable against environmental variations, will be useful in monitoring inhalation doses due to radon progeny for occupational workers.

Monitoring of the unattached fraction of radon progeny by the Kodak LR-115 Type 2, nuclear track detector

The experimental Unattached Radon Progeny Fraction Monitor (URPFM) was developed for the parallel monitoring of all radon progeny and the fraction of radon progeny in air that is attached onto aerosols. The optimum monitor arrangement includes two radon progeny sampling columns with each column incorporating a 0.8μm membrane filter. The filter in the first sampling column collects all the ambient radon progeny that are measured by the Kodak LR-115 nuclear track detector. The second sampling column also includes a fine mesh that removes the unattached radon progeny from the sampled air and thus the track detector that is situated above the mesh measures the unattached radon progeny.Three, five to thirteen-day long radon progeny monitoring periods were conducted inside a sealed room of a residential house and outdoors at an open cut uranium mine. The average unattached fraction of radon progeny was measured to be between 0.09 and 0.14 for the residential house, and between 0.08 and 0.10 for the open cut uranium mine.

Exposure to Radon and Progeny in a Tourist Cavern.

The primary objective of this work was to characterize employee exposure to radon and progeny while performing guide/interpretation and concessions duties in a tourist cavern. Radon gas and progeny concentrations, fraction of unattached progeny, and other environmental parameters were evaluated in a popular tourist cavern in Southeastern New Mexico. Alpha-track detectors were used to measure radon gas in several cavern locations during a 9-mo period. Additionally, radon gas and attached and unattached fractions of radon progeny were measured at three primary cavern work locations during a 1-d period using a SARAD EQF 3220. Radon gas concentrations in the cavern were elevated due to extremely low air exchange rates with substantial seasonal variation. Mean measured radon concentrations ranged from 970 to 2,600 Bq m-3 in the main cavern and from 5,400 to 6,000 Bq m-3 in a smaller cave associated with the regional cave system. Measurements of unattached fractions (0.40-0.60) were higher than those commonly found in mines and other workplaces, leading to the potential for relatively high worker dose. Although radon gas concentrations were below the Occupational Safety and Health Administration Permissible Exposure Limit, employees working in the cavern have the potential to accrue ionizing radiation dose in excess of the annual effective dose limit recommended by the National Council on Radiation Protection and Measurements due to a high unattached fraction of radon progeny. There was a strong negative correlation between unattached fractions and equilibrium factors, but these parameters should be further evaluated for seasonal variation. Introduction of engineering controls such as ventilation could damage the cavern environment, so administrative controls, such as time management, are preferred to reduce employee dose.

Comparison measurement of unattached radon progeny concentration in three different environments

Accurate measurement of unattached radon progeny is important for dose evaluation of radon exposure. For quality control of field surveys, a series of comparison measurements were carried out using three commercial unattached radon progeny monitors in real environments as well as in a radon chamber. The results show that the radon equilibrium equivalent concentrations (EECs) of different monitors agree very well, mostly within ±3.0% where there is no thoron progeny interference in the radon chamber. However, the unattached fraction of radon progeny is not so consistent, and the relative difference is 3.3% ~ 39.5% in different environments. The unattached fraction of radon progeny is affected by aerosol concentration. Anomalously high unattached fraction was found in the environment with extremely high humidity and low aerosol concentration. For accurate measurement of unattached radon progeny, specific attention should be paid to the collection efficiency of unattached radon progeny and the interference of attached radon progeny on a wire screen.

Variation of the unattached fraction of radon progeny and its contribution to radon exposure

The unattached fraction of radon progeny is one of the most important factors for radon exposure evaluation through the dosimetric approach. To better understand its level and variation in the real environment, a series of field measurements were carried out indoors and outdoors, and radon equilibrium equivalent concentration was also measured. The dose contribution of unattached radon progeny was evaluated in addition.The results show that no clear variation trend of the unattached fraction of radon progeny is observed in an indoor or outdoor environment. The average unattached fraction of radon progeny for the indoors and outdoors are (8.7 ± 1.6)% and (9.7 ± 2.1)%, respectively. The dose contribution of unattached radon progeny to total radon exposure is some 38.8% in an indoor environment, suggesting the importance of the evaluation on unattached radon progeny.

Assessment of the unattached fraction of indoor radon progeny and its contribution to dose: a pilot study in China

The unattached fraction of radon progeny (fp) is one of the most important factors for accurate evaluation of the effective dose from a unit of radon exposure, and it may vary greatly in different environments. For precise evaluation of the indoor radon exposure dose and the influence of unattached radon progeny, a pilot survey of fp in different environments was carried out in China with a portable and integrating monitor. The dose conversion factors for radon progeny are calculated with LUDEP® code, and the dose contributions from the unattached and the attached radon progenies were simultaneously evaluated based on the results of field measurements. The results show that even though the concentrations of radon progeny vary significantly among different indoor environments, the variations of fp seem relatively small (9.3–16.9%). The dose contribution from unattached radon progeny is generally larger (30.2–46.2%) in an indoor environment.

An instrument for measuring the unattached fraction of radon progeny with etched trackdetectors

To measure the unattached fraction of radon progeny, a new type of portable, low cost,reusable integrating monitor with etched track detector (CR-39) was developed. This monitorsimultaneously gives the average equilibrium-equivalent concentrations of unattached 222Rn progeny (EECRnu), attached 222Rn progeny (EECRna) andalso 220Rn progeny (EECTn). It was calculated, according to the detection efficiencies which werederived by the Monte Carlo method, that the lower detection limits forEECRnu,EECRna andEECTn are 0.03 Bq m−3, 0.12 Bq m−3 and0.07 Bq m−3, respectively for 24 h integrating sampling at a flow rate of 2.92 l min−1. The validity of the new monitor was confirmed through a series of intercomparisonexperiments.

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.

Development of radon calibration chamber at KRISS

Radon calibration chamber has been constructed to test and calibrate radon and radon progeny detectors at various environmental conditions and to study the characteristic behavior of radon decay products. The size of main room in the chamber is 3.2 m×3.3 m×2.4 m (25.3 m 3) and the total volume of the chamber is 39.1 m 3. The maximum concentration of radon in the chamber can be maintained up to 250 kBq m −3 and temperature and humidity are controlled in the ranges of (10–40)°C and (30–80)%, respectively. The equilibrium factor and unattached fraction of radon progeny are determined at the radon concentration of 2 kBq m −3.

Radon Dose and Aerosols

The equilibrium factor value (F) was measured in the NRPB radon chamber and the corresponding track density ratio (r = D/D0) of bare (D) and diffusion (D0) LR-115 nuclear track detectors was determined, as well as the regression equation F(r). Experiments with LR-115 nuclear track detectors and aerosol sources (burning candle and cigarette) were carried out in the Osijek University radon chamber and afterwards an empirical relationship between the equilibrium factor and aerosol concentration was derived. For the purpose of radon dose equivalent assessment, procedures for determining the unattached fraction of radon progeny were introduced using two nuclear track detectors.

Measurement of equilibrium factor and unattached fraction of radon progeny in Kaohsiung, Taiwan

To reasonably estimate the population dose from radon, equilibrium factor, Fp, and unattached fraction, fp, of radon progeny are important parameters. A Lucas cell and a working level monitor was used for most Fp measurement. The unattached fraction was measured by SARAD EQF3020. A detached house was chosen to measure the Fp in different rooms. The Fp value depended mainly on the ventilation rate and surface to volume ratio of the rooms. Fp and fp were measured in bedrooms of 14 other dwellings. Two hospitals were also chosen for measurement of Fp in the working place using rooms located in the basement. The average Fp for dwellings was about 0.5 and the average unattached fraction was about 0.055. The radon levels in the hospitals were higher than those in the dwellings but the equilibrium factors in the hospital were very low (about 0.06). The low Fp was attributed to the use of a dehumidifier in the hospitals. Dehumidifiers are popular for reducing fungi problem induced by the high humidity in Taiwan.

A survey of radon properties in underground shopping centers in Hong Kong

A number of radon-related properties have been surveyed in underground shopping centers in Hong Kong. These parameters include the radon concentration, the total potential alpha energy concentration of radon progeny, the equilibrium factor and the unattached fraction of radon progeny. The mean values recorded for these were 29.2 ± 7.8 Bq/m 3, 3.60 ± 1.53 mWL, 0.46 ± 0.16 and 0.05 ± 0.03, respectively. Based on these figures, we have calculated the average radon dose received by employees in an underground shopping center in Hong Kong to be 0.22 mSv/yr, which represents an approximate increase of 8% over the total dose of about 2.7 mSv/yr received by the average person in Hong Kong.

Measurements of unattached fraction of radon progeny with two different methods

Measurements of unattached fraction of radon progeny with two different methods

Deposition of 214Pb and nuclear aberrations in the respiratory tract of rats after exposure to radon progeny under different aerosol conditions

The aim of this work was to relate 214Pb deposition within the respiratory tract of the rat to aerosol characteristics during exposure to radon and its progeny. Two different exposure conditions were studied: static, without air recirculation with a low unattached fraction of radon progeny ( fp≈10%); and dynamic, with continuous air recirculation ( fp>80%). Deposition was estimated by measuring 214Pb retention in nasopharynx and lungs at the end of a 3-h exposure using gamma spectrometry. The deposition of 214Pb in the pulmonary region was the same in the two exposure conditions. By contrast, nasopharynx deposition was 5 times higher under dynamic than under static exposure. The dose delivered to the deep lung was estimated by micronuclei scoring in alveolar macrophages extracted by pulmonary lavage. For a similar cumulative dose delivered under static or dynamic conditions, a similar micronuclei index was measured, 1.22% ± 0.26 and 1.47% ± 0.42, respectively, 8 d after exposure. These results suggest that the unattached fraction did not influence radon progeny deposition and the resulting delivered dose in the deep lung of the rat.

Unattached fraction and size distribution of aerosol-attached radon progeny in the open air

Unattached fractions of the radon progeny 218Po and 214Pb, size distributions for both unattached 218Po and 214Pb, and attached 214Pb and 214Bi, along with condensation nuclei (aerosol-particle concentrations), were measured in the open air of the city of El-Minia, Egypt. The measurements were performed with a wire-screen diffusion battery and a low-pressure Berner cascade impactor using standard methodologies. The results for parameters of derived distributions demonstrate that the distributions for the former (unattached 218Po and 214Pb) are nearly similar. The diffusion equivalent diameters ( d f) of 218Po and 214Pb were determined to be 1.4 and 1.55 nm with relative geometric standard deviations ( σ g) of 1.65 and 2.1, respectively. The latter distributions (attached 214Pb and 214Bi) are nearly identical. Most of the activities were associated with the aerosol particles of the accumulation mode. The mean activity median aerodynamic diameters (AMAD) of 214Pb and 214Bi have the same value of 380 nm but the relative geometric standard deviation of the log-normal distribution of 214Pb shows a broader activity distribution than 214Bi ( σ g = 2.2 for 214 Pb and σ g = 2.05 for 214 Bi ).

Equilibrium Factor and Unattached Fraction of Radon Progeny in Outdoor Air.

In a suburb of Tokyo, the concentrations of 222Rn, its progeny and aerosol particles in outdoor air were measured simultaneously from December 1993 to April 1995. Values of 0.69 and 0.024 were obtained for annual mean values of equilibrium factor, F, and unattached fraction of potential alpha energy, fp, respectively.The concentrations of 222Rn were found to be high in winter and low in summer and to be high from night to morning and low during daytime. On the other hand, no clear seasonal and diurnal variations were observed in F and fp. The variations of fp and unattached fraction of 218Po, fA, strongly depended on aerosol concentration. In cases where the aerosol concentrations were lower than 10000 cm-3, it was found that values of F were relatively low and values of fp and fA were fairly high. However, such cases were only about 3% of all data observed in 1994. From the relation between fA and aerosol concentration, the representative value of aerosol particle diameter was estimated to be 0.1-0.15 μm.

Equilibrium Factor and Unattached Fraction of Radon Progeny in Nuclear Power Plants

Equilibrium Factor and Unattached Fraction of Radon Progeny in Nuclear Power Plants

Experimental Evaluation of Wire Mesh Screen Counting Parameters for Measurements of the Unattached Fraction of Radon Progeny

Direct measurements (specifically the front-to-back ratio) of alpha radioactivity from radon progeny deposited on the front and back of a 400-wire mesh screen were performed under realistic aerosol conditions outdoors with two scintillation alpha detectors facing both sides of the screen simultaneously. Two flow regimes were tested: one which kept the flow Reynolds number (Ref) for the wire below one (200 L min-1) and a second with the flow Reynolds number for wire > 1 (400 L min-1). To estimate the radioactivity loss in the screen, parallel measurements of open and backup filters were also performed. The average front-to-back ratio expressed as a ratio of the potential alpha energy concentration as measured on the screen side facing the airflow to the other side of the screen for 200 L min-1 and 400 L min-1 was 3.42 +/- 0.32 (standard error) and 2.30 +/- 0.14 (standard error), respectively. The loss of radioactivity in the screen expressed as a ratio between the potential alpha energy concentration measured on an open filter minus backup filter to the sum of the potential alpha energy concentration measured on the front and back of the screen was 1.29 +/- 0.13 and 1.27 +/- 0.22 for 200 and 400 L min-1, respectively.