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1.
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.  相似文献   

2.
This work reports a novel method for determining 222Rn (radon) in air using a radon-218Po calibration curve constructed by an absorbable non-volatile liquid scintillator (NVLS). The ability of this method to detect low natural concentrations of radon was confirmed from linear extrapolation of the curve between 500 and 8000 Bq/m3. The calibration curve was created from data obtained from measurements performed in a radon calibration chamber at the National Institute of Radiological Science (NIRS) by using the least-squares method. The line had high precision and stability, and the required detection time was less than that of 214Po. An absorptive NVLS was used to collect radon and was found to be highly advantageous for α-spectrometry liquid scintillation measurements. Variations of the Ostwald coefficient due to changes in temperature and humidity, which affect radon absorption, were investigated and discussed.  相似文献   

3.
《Radiation measurements》2007,42(3):486-490
Measurements of radon concentration in soil gas have been carried out using a bubbling system in which the soil gas is drawn through an active pumping to bubble a liquid absorber (olive oil) for the deposition of the soil gas in it. After the bubbling process, the absorber is then taken for gamma-ray measurements. Gamma-ray photopeaks from the 214Pb and the 214Bi radon progeny are considered for the detection of the 222Rn gas to study the concentration levels for radon soil gas. Results for some field measurements were obtained and compared with results obtained using AlphaGuard radon gas monitor. The technique provides a possible approach for the measurements of radon soil gas with gamma-ray spectrometry.  相似文献   

4.
The size distribution of unattached radon progeny is an important parameter for an accurate estimation of the internal dose of radon exposure. In this study, a new measuring system was developed to evaluate the size distribution of unattached radon progeny in air. In the system, airborne radon progeny were collected with a newly designed graded screen array (GSA), the activity concentrations were measured by using the imaging plate technique, and the size distribution of unattached fraction was retrieved by using an iterative nonlinear algorithm. The simulation results indicated that the collection characteristics of the new GSA system were well agreed with other systems. Test experiments showed that the activity-weighted median diameters (AMD) for unattached 218Po, 214Pb and 214Bi were 0.89 ± 0.11 nm, 0.96 ± 0.13 nm and 1.01 ± 0.25 nm in a particle-free radon chamber, and the distribution changed with different concentrations of particles. As multiple measurements can be simultaneously carried out with a single IP, the new technique is considered as an optional and useful way to measure the size distribution measurement of unattached radon progeny.  相似文献   

5.
The measurement of the 214Po concentration in air with Makrofol-DE detectors is useful to estimate the long-term averaged equilibrium factors indoors. To differentiate α-particles emitted by 214Po from those emitted by 218Po and 222Rn, the detector must register only α-particles with energies between 6.2 and 7.5 MeV. The required energy response is obtained only if a removed layer of about 43 μm is achieved in a chemical etching of the detector. The methodology used to determine the etching conditions is described in this paper. The optimum conditions found are: a) chemical etching for 6 h at a temperature of 40°C, using 7.5 M KOH mixed with 50% ethanol as an etchant, and b) electrochemical etching for 1 h at a frequency of 3 kHz and an electric field strength of 34 kV cm−1. Several dosimeters have exposed during 2 months in dwellings located in the Barcelona area, Spain. A 214Po averaged concentration of (13.6 ± 8.6) Bq m−3 was obtained.  相似文献   

6.
A high-resolution gamma-ray spectrometer with a Ge(Li)-detector is described. The spectrometer is used as a single crystal spectrometer as well as a three crystal pair spectrometer with a Ge(Li) central detector and two NaJ-crystals for the detection of the annihilation quanta. Measurements were made of214Po. The sources were222Rn in small glass tubes. 66 gamma-rays, 10 of which hitherto unknown, were observed. An improved level scheme of214Po is given.  相似文献   

7.
In this study we describe the set-up of a new passive integrating system to measure simultaneously 222Rn, 222Rn progeny (218Po and 214Po) and 220Rn concentration indoors. It consists of four Makrofol-DE (polycarbonate) circular foils. Two are enclosed within two diffusion chambers—each one with a different filter membrane—to measure 222Rn and 222Rn+220Rn. The other two foils are kept in direct contact with air and are electrochemically etched at different conditions to obtain the 222Rn daughters. Theoretical sensitivities of each Makrofol-DE foil are calculated using Monte-Carlo technique. The calculations are performed taking into account: (1) the Bethe–Bloch's expression for the stopping power of heavy charged particles in a medium, (2) the properties and behaviour of 222Rn, 220Rn and their progeny in the open air and within the diffusion chamber and (3) the etching conditions used to visualise -particles tracks.  相似文献   

8.
222Rn activity in soil gas was measured across fault segments of the seismic active Ventaniella Fault and the seismic inactive Sabero-Gordón Fault in the Cantabrian Mountains, NW Spain, in order to investigate the variability of the 222Rn concentration. The sampling took place in summer and autumn 2010. During the autumn measurement program, an additional 222Rn soil gas mapping was carried out in the Sabero-Gordón research area. Zones of elevated 222Rn activity in the soil gas were identified by background 222Rn values of the geological formations used for mapping and local background values from 222Rn values outside the elevated 222Rn activity zones. Unexpectedly, the Sabero-Gordón Fault showed higher 222Rn activity, up to 441 kBqm?3, compared to the 222Rn activity of the Ventaniella Fault which had a maximum of 106 kBqm?3. Comparison of the results shows that the values measured in summer are about 5 times higher than the autumn values. This difference is not reflected in petrophysical soil parameters or meteorological conditions documented during the field measurements. Based on the results of our work we conclude that the magnitude of 222Rn concentration in soil gas is not an indicator of local seismic activity of the investigated faults. For the studied segment of the aseismic Sabero-Gordón Fault we suggest active genesis of pathways for gas migration driven by aseismic fault slip causing the elevated 222Rn activity in soil gas.  相似文献   

9.
Exhalation of radon and its carrier gases in SW Taiwan   总被引:3,自引:0,他引:3  
Gas compositions of mud volcanoes reveal multiple sources for gas exhalation in SW Taiwan. For comparison, two sites, Yan-chao (YC) and Chung-lun (CL), were chosen for measurements of soil Rn concentrations using a portable radon detector. The 222Rn concentrations at the YC site were ca. 5200 Bq/m3. However, the average 222Rn concentrations at the CL site exhibited higher value of ca. 16,800 Bq/m3. With the reference of the gas flux and compositions from the nearby mud pool, the soil 222Rn concentrations are largely controlled by the flux of carrier gases exhaled from deep reservoirs.  相似文献   

10.
A simple radiochemical procedure has been developed to determine 210Pb and 210Po in environmental samples from the same matrix. Sediment samples are decomposed by leaching with mineral acids or by microwave digestion, while water samples are pre-concentrated. One part of the resulting solution, spiked with 209Po, is used for 210Po determination by spontaneous deposition onto nickel disks (α-spectrometry). The other part is assayed for 210Pb, separating the Pb either by anion-exchange (sediment samples), or by solvent extraction (water samples). The 210Pb source is finally prepared by precipitation as oxalate and the chemical recovery determined by gravimetry. The 210Pb activity concentration is determined by liquid scintillation. A standard sediment sample supplied by IAEA and spiked water samples were analysed to check the procedure. The 210Pb and 210Po measurements agreed well with the certifications, deviations being less than 10%. The mean recoveries for Pb and Po were (70±12)% and (77±8%) for sediments, and (70±10)% and (81±7)% for waters, respectively.  相似文献   

11.
Ever since studies on uranium miners established the presence of a positive risk coefficient for the occurrence of lung cancer in miners exposed to elevated levels of 222Rn and its progeny, there was a great upsurge of interest in the measurement of 222Rn in the environment. Subsequently, considerable data is being generated on the levels of 222Rn in the environment across the worlds and is being periodically reported by UNSCEAR reports. In contrast to this, data pertaining to 220Rn in indoors and workplace environment is scaree due to the genral perception that its levels are negligible due to its shorter half life, and subsequently its contribution to the total inhalation dose is ignored, in the presence of other significant sources of natural radiation. This may not be true. Globally many locations have higher levels of natural background radiation due to elevated levels of primordial radio nuclides in the soil and their decay products like radon (222Rn), and thoron (220Rn) in the environment. Of late, technologically enhanced naturally occurring radioactive material has also contributed to the burden of background radiation. It is estimated that inhalation of 222Rn, 220Rn and their short lived progenies contribute more than 54% of the total natural background radiation dose received by the general population. 220Rn problem exists in industries which use thorium nitrate. Including India, lamps using thoriated gas mantles are still being used for indoor and outdoor lighting and by hawkers in rural as well as urban areas. Considering the fact that large amount of thorium nitrate is being handled by these industries, contribution to the inhalation dose of workers from 220Rn gas emanated and build up of the progeny in ambient air may also be quite significant. In this paper current status of 220Rn levels in the indoor environment and workplaces as well as in other industries where large amount of 232Th is being handled is being summarized. Methods of measurement and reported levels are also summarized.  相似文献   

12.
Solid State Nuclear Track Detector (SSNTD) based diffusion chambers have been widely used for residential radon measurements due to their cost effectiveness, portability and easy-to-use feature. In India, an LR-115 track detector based twin-cup dosimeter has been in use for about a decade for indoor 222Rn and 220Rn measurements. However, the estimation of the gas concentrations using this dosimeter was based on the assumption of the same entry rate of the gases into the two cups of the dosimeter, which may not be valid for dosimeters deployed in turbulent environmental conditions. To overcome this limitation, a new pin-hole based 222Rn/220Rn discriminating measurement device has been developed. The underlying discrimination technique has been established by modelling 222Rn and 220Rn diffusion into a pin-hole chamber and validating the same by carrying out experiments in a test chamber. The device has been calibrated at Bhabha Atomic Research Centre, Mumbai following the standard procedures to correlate the number of tracks registered in the LR-115 detector placed in the two chambers to the 222Rn and 220Rn concentration in the environment. Salient features of the device include (i) the pin-holes act as 222Rn/220Rn discriminator and eliminate the requirement of membrane filter used in the earlier twin cup design (ii) the single entrance design for gas transmission and (iii) use of multiple pin-holes of reasonably small radius minimises effect of turbulence on 222Rn/220Rn transmission factors so that the calibration factor is independent of indoor turbulence.  相似文献   

13.
通过研究大气颗粒物中222Rn子体活度比与颗粒物平均寿命之间的关系,建立了基于活度比估算大气颗粒物滞留时间(residence time of atmospheric aerosol,RTAA)的方法,并在相对理想条件下进行了实验验证.当氡室浓度稳定为1.816kBq/m3时,由214Bi/214Pb活度比计算出的RTAA为112.17min,与氡室的平均换气时间(104.17min)相当,表明大气颗粒物中同一衰变链上的放射性核素活度比(如214Bi/214Pb,210Bi/210Pb或210Po/210Pb)可以用于估算RTAA.  相似文献   

14.
In Ge gamma-ray spectrometry for the annual radiation dose determination in the luminescence dating of sediments, the picture of 226Ra enrichment or depletion (in the 238U decay series) obtained via measurement of its 214Pb and 214Bi daughters may be disturbed by the 222Rn-content of the sample being decreased due to manipulations such as drying and pulverizing. Therefore, it is common practice to start the measurement only about 1 month after encapsulating the material, after which the 226Ra(1600 a)- 222Rn(3.82 d) mother-daughter equilibrium is re-established. Evidently, this only holds on condition that no significant escape of Rn occurs out of the sediment after making it up for counting. In order to experimentally investigate this effect, in the present work measurements were carried out with various types of dried and pulverized sediments that were either encapsulated in screw-cap polystyrene vials or in sealed glass containers, or that were mixed with molten wax followed by solidification in a cylindrical geometry. From the results obtained, it could be concluded that preparation and counting of the sediment-wax mixture is the method of choice.  相似文献   

15.
The practical applications of the method for retrospective 222Rn measurements by home stored CDs/DVDs need a proper metrological assurance. The specific feature of this method, as compared to other methods for retrospective 222Rn measurements is the possibility for an individual a posteriori calibration of the used CD/DVD-detectors. This paper describes a procedure to ensure the traceability of this method to a reference STAR laboratory. A set of 7 groups of CDs/DVDs were exposed to 4 reference 222Rn exposure levels. After that they were treated in the etching laboratory as ”real” detectors and the 222Rn concentrations were determined by applying an individual a posteriori calibration, correction for high track density and correction for depth at which the alpha tracks were etched. The results from all 7 groups of exposed detectors demonstrated relative variation from the reference values in the interval 3.4–23.4%. The results provide evidence that the routine measurements by the CD/DVD method warrant measurements with a relative uncertainty better than 25% and therefore this method is acceptable for large-scale applications.  相似文献   

16.
222Rn concentrations in the air in Nerja cave (Spain) (3° 52′35′′W 36° 43′50′′N) were measured by continuous monitoring using Alpha-Guard, Genitron instrument equipment. The 222Rn measurements were carried out for a complete annual cycle in the different halls: Vestibule hall from July 2003 to June 2004, Ballet hall from July 2004 to June 2005 and Mirador hall from July 2005 to June 2006. Starting from the entrance of the cave we successively find the Vestibule hall, the Ballet hall and the Mirador hall. The range of 222Rn levels were of 8–627 Bq m−3 for the Vestibule hall, 28–575 Bq m−3 for the Ballet hall and 38–578 Bq m−3 for the Mirador. The aim of this study was to detect seasonal variation patterns of 222Rn concentrations. The seasonal variations of 222Rn concentrations are discussed in relation to various meteorological factors measured inside and outside the cave. The radiation exposure levels for workers and tourists with different equilibrium factors have been evaluated. The radiation exposure levels for workers and tourists only represent a low percentage of the exposure guides for the general population.  相似文献   

17.
18.
A system of image analysis is applied to the track analysis of a plastic detector (LR 115). Based on track characteristics the system permits the separation of tracks produced by 222Rn and 218Po from those produced by 214Po. LR 115 was used inside a thin film geometry monitor and irradiated under very low ventilation conditions, where secular radioactive equilibrium between radon and progeny is expected. The monitor is used intending to exclude the entrance of external radon progeny in the sensitive volume of the plastic detector. The radioactive (secular) equilibrium is rapidly attained inside the monitor and equal numbers of particles from 218Po, 214Po and 222Rn are expected to reach the plastic. In order to guarantee good detection efficiency in the restricted volume, and to discriminate alpha energies, the LR 115 piece inside the monitor is covered with an aluminum foil of suitable thickness. The separation of tracks produced by alpha particles of different energies is made through the use of two track parameters related to area and opacity of the tracks. The ratio of tracks produced by (218Po and 222Rn) and 214Po—expected as two—is used to test the separation method in a series of controlled irradiations. Results point to the experimental attainment of radioactive equilibrium inside the monitor supporting the determination of 214Po concentration alone, and points to an exclusive entrance of 222Rn inside the monitor, at low ventilation rates. This way, in situations where radioactive equilibrium inside the monitor may be considered, the exclusive measurement of radon concentration in the environment is possible.  相似文献   

19.
222Rn concentration time series at 10 m and at 100 m have been measured hourly for one year at the meteorological station, El Arenosillo, on the Spanish southwest coast. A 222Rn flux characterization was also done.A seasonal analysis of atmospheric 222Rn concentration was performed and results for each season present evidence associated with the origin of air masses reaching the El Arenosillo station. An increase in 222Rn concentration was observed when the wind came from Morocco, the Sierra Morena and the Guadalquivir valley areas. On the other hand, a net 222Rn concentration decrease was found when the wind came from the Atlantic Ocean and the South of Portugal.Low 222Rn flux of 4 Bq m?2 h?1 was measured. This result makes this station a useful site for studies related to remote 222Rn source contributions because of low local 222Rn background. The measured annual average concentration of 222Rn gas at the El Arenosillo station is 3.51 ± 0.05 Bq m?3 at 10 m and 2.61 ± 0.05 Bq m?3 at 100 m.  相似文献   

20.
It is known that tobacco leaves may contain 210Pb and 210Po in significant concentrations. The cumulative alpha-radiation dose due to the radioactive content of inhaled cigarette smoke and the increasing number of lung cancer cases explain the importance of the investigation. The present study investigated the activity concentrations of these two radionuclides in 29 Hungarian cigarette samples. The relation between 210Po/210Pb activity and nicotine/tar content of these cigarettes was also examined. 210Po was determined by alpha spectrometry using a PIPS detector after chemical leaching and spontaneous deposition of 210Po on a high nickel-content (25%) stainless steel disk. The 210Pb activity was calculated from the 210Po originated from the decay of 210Pb after a waiting period of eight months. The 210Po activity concentrations of the measured types of cigarettes ranged from 10.0 to 33.5 mBq/cigarette, and the activity of 210Pb varied from 9.6 to 32.5 mBq/cigarette. The average annual committed effective dose is estimated to be 185.6±70.6μSv/y and 58.7±22.7μSv/y due to cigarette smoking (20 cigarettes/day) for 210Po and 210Pb, respectively.  相似文献   

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