痕量氡气测量仪器自动标定装置的研制

研究了空气中痕量氡的动态稳定技术和氡及其子体浓度的准确测量方法.研制了具有氡浓度自动控制、温湿度调控、气溶胶发生/采集等功能的标准氡室,并建立了主氡室标称体积达4 m3的氡测量仪器检定/校准装置和氡子体放射性气溶胶检测与实验研究平台.研究表明,本装置测氡浓度范围为370～20000 Bq/m3;检测精确度达3％;单点校...     

Experimental study of dependence on humidity and flow rate for a modified flowthrough radon source

Journal of Radioanalytical and Nuclear Chemistry - Flow-through radon sources were widely utilized in the calibration of radon equipment and radon studies. In this paper a broken 266Ra source which...     

Experimental study of radon and thoron diffusion through barriers

The radon chamber and radon calibration set have been modified for investigation of the diffusion coefficients of the barriers for reduction of radon exposure in the dwellings and for application as filters to separate radon and thoron. The volume radon activities have been measured by continuous monitors with scintillation cell or ionisation chamber. The theory on which the experimental determination of a barrier diffusion coefficient is based, is presented. The diffusion ability of radon has been studied for different materials and the results of the measurements are presented and discussed.     

The fluctuations of indoor radon measurements from the building materials in a real situation

In this study, we have investigated the fluctuations of radon levels in two experimental rooms constructed for secondary standard dosimetric calibration. The values over the short-term (the first two weeks) were in the range of 10–14 pCi/L of radon in air, while those of the long-term were between 6–14 pCi/L of radon. Even though the temperature and humidity was relatively constant during the second half of the rainy season, there was a trend towards lower radon values. It is concluded that ventilation is an important factor in indoor radon levels.     

A new method for studying the influence of pollution and soil nature on the radon emanation from water samples by using solid state nuclear track detectors

Radon emanation from surface water and groundwater samples has been studied by using CR-39 and LR-115 solid state nuclear track detectors (SSNTD). A calibration method for determining the thoron and radon concentrations of the water samples studied has been developed. The effect of pollution due to coal fly ashes, cement and granite dusts on the radon emanation from water samples has been investigated. The influence of the radon source on the radon emanation rates from water samples has been studied.     

A simple laboratory-based radon calibration system

Measurements of ²²²Rn (“radon”) in the environment are important in the geosciences and radiation-protection fields. We demonstrate here a simple laboratory-based calibration system to evaluate the efficiency of radon detectors with a reproducibility of about ±2%. The system uses a closed-loop air circulation design with ²²⁶Ra adsorbed onto MnO₂-impregnated fiber as a radon source. Two RAD7 radon detectors (Durridge Co., Inc.) that were precisely calibrated at Durridge’s in-house calibration facility are used as secondary standards. By parallel analysis of the radon-enriched air within the closed loop, the test RAD7s are assigned a calibration coefficient to be applied to future measurements. We also performed a side-by-side intercomparison with two RAD7s in a high-radon natural environmental setting (limestone cave in Florida) that produced comparable results.     

Indoor radon measurement methodology by solid state nuclear track detectors

The measurement of radon using solid state nuclear track detectors is presented. The importance of radon in environmental radiation and to human health is well known and thus the measurement and evaluation of indoor radon is important not only for dosimetry purposes but also for evaluation of public health impacts. In this work we discuss the detection and calibration systems and the etching method of solid state detectors. Some considerations regarding potential problems that can be encountered in measuring indoor radon in an underdeveloped country, and how can they be solved are discussed.     

The effect of humidity on the accuracy of measurement of an electret radon dosimeter

Test has been conducted for the response of electret radon dosimeters with varying levels of humidity. At a constant value of radon concentration, measured values have been found to increase linearly with increasing humidity, from 30% RH up to a value of 85% RH. On this basis we argue for the establishment of a humidity-dependent calibration factor.     

Study of the influence of the lithological and hydrogeological parameters of aquifers on the radon emanation from underground waters using solid state nuclear track detectors

Radon-to-thoron ratios as well as radon and thoron activity concentrations in different underground water samples belonging to different aquifers in the Moroccan Middle Atlas area have been evaluated by LR-115 and CR-39 solid state nuclear track detectors (SSNTD) using a new calibration method. The radon isotope (²²²Rn) was used as a tracer for studying the water exchange between different aquifers of the area studied. The influence of the lithological and hydrogeological parameters of the aquifers on radon emanation were investigated.     

Emanation studies of radium containing materials by a simple radon monitoring system

The applicability of a radon emanation system to radium determination in fine-grained solid samples has been investigated by means of a closed radon emanation system consisting of a radon monitor and an aluminium vessel. The system has been calibrated with radium-containing fine-grained samples (e.g. phosphogypsum, granite and pitchblende) and the evaluation of the calibration data included linearity, detection limits and analytical resolution of the method. The studied radon emanation system presents very good linear response (R ² = 0.99) to the radium content of the samples, the detection limit for radon is 25 Bq m^?3 and the analytical resolution 15 Bq m^?3. In addition, the relation between particle size of the materials and radon emanation has indicated that the applicability of the radon emanation system to radium determination is strongly depended not only on the mineral type but also on the particle size of the grained material.     

A new method for determining the radon emanation coefficients and radon production rates in different building materials using solid state nuclear track detectors

Radon α-activity concentrations have been measured inside and outside various building materials by combining a calculational method with the solid state nuclear track detector (SSNTD) technique. Radon emanation coefficients of the studied materials have been evaluated. A new calibration method for determining the radium (²²⁶Ra) and thorium (²³²Th) specific activities of the considered building materials has been developed. The radon production rates per unit volume of the studied materials have been evaluated. The influence of the material porosity on the radon emanation coefficient and radon production rate have been investigated.     

Study of Long-Term Radon Progeny in Humans for Retrospective Evaluation of Radon Exposure

An individual in vivo monitor using seven Germanium detectors with a total area of 24,000 mm² was prepared for ²¹⁰Pb skull measurements. System calibration with anthropomorphic head phantoms and a straightforward efficiency estimation yielded a minimum detectable activity (MDA) of 6.7 Bq and a lower limit of detection (LLD) of 14 Bq (CL: 95%). Two selected persons were measured for 1 h each to reconstruct their cumulative radon exposure. From the added pulse height spectrum a ²¹⁰Pb activity in the skull of 3.1±7.2 Bq (result with 95%-CL) was estimated, but clear conclusions on their radon exposure using a new metabolism model of lead in man could not be drawn. Further improvements in the selection of highly exposed persons as well as head calibration and Lackground reduction are necessary using this attempt for retrospective exposure reconstruction.     

Determination of the calibration factor for CR-39 based indoor radon detector

CR-39 based radon detectors are widely used in measuring indoor radon. In this regard, different groups have developed their own systems. However, before using any system for indoor radon measurements, it has, first, to be calibrated with a known source of radon. In the current study, CR-39 based NRPB type radon detector has been calibrated and presented. In this regard, about 200 holders for CR-39 were obtained from the Radiation Protection Division of the Health Protection Agency (former NRPB), UK and several thousand more similar detector holders, hereafter called NRPB type holders, were fabricated locally in Pakistan. Uranium ore samples of known grade were placed into the plastic containers of volume 5.4 × 10³ cm³ and CR-39 detectors were placed in the NRPB type holders and were then installed into the containers at a distance of 25 cm from the surface of the known grade ore samples. The containers were hermetically sealed and the detectors were allowed to expose to radon for 3 weeks. After 16 h etching in 25 % NaOH at 80 °C, the measured track densities were related to the radon concentration. The calibration factor of 2.563 tracks cm^?2 h^?1/kBq m^?3 was obtained.     

Calibration technique for a CR-39 detector for soil and water radon exhalation rate measurements

The calibration factor of 0.029 ± 0.0002 track cm^?2 per Bq d m^?3 for radon concentration measurements was determined using CR-39 and RAD7 detectors. The ²²²Rn concentration varied from 2,225 to 9,950 and 12 to 1,002 Bq m^?3 in soil and water, respectively. The highest radon exhalation and gamma dose rates were found in Acid and undifferentiated granitic rocks and Miscellaneous soils.     

Influence of pollution and building materials on domestic radioactivity in Marrakechi dwellings

Domestic radioactivity has been studied by using LR-115 and CR-39 solid state nuclear track detectors (SNTD) and a suitable beta- and gamma-gaseous counter. A new calibration method, based on measuring thoron (²²⁰Rn) to radon (²²²Rn) ratios, has been developed for determining the -activity originating from radon in different Marrakechi dwellings. The influence of building materials as well as pollution and airing factors, on domestic radioactivity has been investigated.     

Calibration coefficient of the SSNTD and equilibrium factor for radon

Disintegration, ventilation and deposition were considered as removal processes of the radon and its short-lived daughters in air and the respective concentration equations were applied. Calibration coefficient (K_F) of the solid state nuclear track detector (SSNTD) LR-115 for radon and the equilibrium factor (F) were related to track densities of the bare detector (D) and the filtered one (D_o). A useful relationship between K_F, F and detector sensitivity coefficient (k) was derived. Using the calibrated value k=3.29×10^–3 m, the exposed detectors gave the average values of the equilibrium factor, calibration coefficient and indoor radon concentration of a single house living room in Osijek 0.46, 142.3 m^–1 and 37.8 Bq m^–3, respectively.     

The efficiency calibration of radioxenon isotopes of inhomogeneous adsorption column for HPGe γ spectrometry

In this paper, a new efficiency calibration scheme is proposed for the inhomogeneous adsorption column, in which the segment efficiencies modeled by the Monte Carlo toolkit Geant4 are weighted according to the fraction distributions of the adsorbed radioxenon based on the equilibrium adsorption theory. In order to verify the scheme, an experiment of efficiency calibration of HPGe detector by employing radon daughters was performed, and as a result the relative errors between the measured value and simulated value was less than ±?2.3%. This method developed in this paper is useful for the development of rapid test device of radioactive gas.     

An accurate method for the determination of <Superscript>226</Superscript>Ra activity concentrations in soil

A quantitative method to determine the activity concentration of ²²⁶Ra in soil samples was established using high performance environmental gamma-ray spectrometry. In this method, a semi-empirical calibration procedure was developed for full energy peak efficiency calculation utilizing the elemental composition of the soil sample. Aatami software was used to deconvolute the ²³⁵U and ²²⁶Ra doublet at 185.7 keV and 186.2 keV, respectively, and to fit the baseline of the soil gamma-spectrum for the determination of ²²⁶Ra activity. The results indicated that the Aatami doublet deconvolution procedure provides a rapid and accurate analysis of a complicated spectrum in comparison with other cumbersome spectral interference correction methods. The study also compared the results with those obtained by radon progeny (²¹⁴Pb, or ²¹⁴Bi) measurements and found that the deconvolution method provided a more accurate ²²⁶Ra activity as it is independent of the error caused by radon diffusion. This error can be quite large since the amount of escaped radon gas through the sample container walls and sealing cannot be accurately quantified.     

Characterization of airborne radon released by domestic showering and the use of a washing machine

Water originated from groundwater systems can have relatively high concentration of radon. In many situations, radon is released from the water and mixes with the indoor air. In the present study, laboratory experiments were conducted to characterize the airborne radon released by showering and the use of a washing machine. The followings were discussed: (1) a comparison between the loss of waterborne radon and the increase of airborne radon, (2) time-related changes in airborne radon after the water use, (3) changes in the equilibrium factor, and (4) the relationship between radon concentration and the distance from the source of radon release.     

A new approach for radon monitoring in soil as an earthquake precursor using optical fiber

Temporal variations of radon concentration in soil before the earthquake are known as an earthquake precursor. For using of radon as an earthquake precursor, it is necessary to constantly monitor radon concentration variations in a relatively wide range in the vicinity of a fault which is virtually impossible for radon detectors that already exist. This paper proposes a new method for continuous measurement of radon concentration variations in a wide range, using optical fiber as radon detector. For this purpose, an experimental system consisting of radon source, optical-fiber holding chamber, radon gas detector, optical laser source, and optical power meter have been arranged to with the aim to create different concentrations of radon gas in the vicinity of the optical fiber; the attenuation which creates on optical fiber is subsequently measured. As a result, the average of the attenuation is 0.004 μw per each meter per Bq/l since the fault’s length is more than ten kilometers; sensitivity of the measurement can be improved many times over.