共查询到20条相似文献,搜索用时 31 毫秒
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John K.C. Leung D. Jia Man-yin W. Tso 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1994,350(3):566-571
A fully automated radon exposure chamber is described. The chamber is made of stainless steel and has a volume of 1.46 m3. The chamber allows 222Rn, 220Rn or both to be injected from the bottom pipe-lines into the chamber in a 100% flow-through mode, 100% recirculate mode or flow-through/recirculate mode. Either atmospheric aerosol or monodisperse aerosol from aerosol generator can be injected into the chamber. The radon concentration; radon daughter concentration; unattached fraction of radon daughters; aerosol size distribution and activity size distribution of radon daughters in aerosols are continuously monitored by computers and feedback signals are used to maintain the specified condition. Though the chamber may be small when compared to walk-in type exposure room, it has the advantage of fast response to changes in the chamber condition and yet is large enough to preclude perturbations due to sampling or other activities. 相似文献
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Radon in soil gas--investigation and data standardisation at radon reference sites, Czech Republic 总被引:2,自引:0,他引:2
Radon risk mapping at building sites in the Czech Republic indicate an advisable level of protection of buildings against the penetration of radon from the geological basement. Various techniques and instruments are used for the measurement of radon in soil gas. A national radon chamber and three radon reference sites in Central Bohemia enable radon data standardisation. Tests of field radon measurements and the reported radon activity concentration in soil gas at the reference sites are based on comparisons with other organisations and with a database of reference site measurements. The radon reference sites have been used for various investigations of radon in soil gas during the period 2000-07. 相似文献
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The monitoring of radon exposure at workplaces is of great importance. Up to now passive measurement systems have been used for the registration of radon gas. Recently an electronic radon gas personal dosemeter came onto the market as an active measurement system for the registration of radon exposure (DOSEman; Sarad GmbH, Dresden, Germany). In this personal monitor, the radon gas diffuses through a membrane into a measurement chamber. A silicon detector system records spectroscopically the alpha decays of the radon gas and of the short-lived progeny 218Po and 214Po gathered onto the detector by an electrical field. In this work the calibration was tested and a proficiency test of this equipment was made. The diffusion behaviour of the radon gas into the measurement chamber, susceptibility to thoron, efficiency, influence of humidity, accuracy and the detection limit were checked. 相似文献
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With the availability of the National Institute of Standards and Technology (NIST) Radon Emanation Standard with a content of approximately 5000 Bq of 226Ra, it is possible to build a flow through a practical radon test chamber. A standard glove box with four gloves and a transfer port is used. Air is pumped through a flow integrator, water jar for humidification and NIST source holder, and into the glove box through a manifold. A derived theoretical expression provides the calculated radon concentration inside the chamber. The calculation includes a derived decay correction due to the large volume and low flow rate of the system. Several calibrated continuous radon monitors and passive integrating electret ion chambers tested in the chamber agreed fairly well with the calculated radon concentrations. The chamber is suitable for handling the calibration of several detectors at the same time. 相似文献
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Ishikawa T 《Radiation protection dosimetry》2004,108(4):327-330
A radon detector of pulse-ionization chamber (PIC) type could have some sensitivity for thoron. Thus, the presence of thoron could interfere with precise measurement of radon. In the present study, effects of thoron on the most common type of PIC detector (commercial name AlphaGUARD) were investigated using an exposure chamber. The AlphaGUARD was exposed to a mixture of radon and thoron, together with a radon/thoron discriminative monitor that employs a silicon solid-state detector. The thoron sensitivity of the PIC detector was estimated by comparing the two detectors. As a result, the thoron sensitivity was about 10% compared with the radon sensitivity. In other words, the radon concentration (Bq m(-3)) measured with the PIC detector was approximately the sum of the actual radon concentration (Bq m(-3)) and 10% of the thoron concentration (Bq m(-3)). The sensitivity to thoron should be considered in measurements in thoron-enhanced areas. 相似文献
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The continual soil-gas radon concentration measurements are absolutely crucial for a reliable assessment of radon entry characteristics into the indoor building environment. For this purpose, a new detection system (a continuous monitor RM-3) was developed and tested. The detection principle of the monitoring device is based on an airflow ionisation chamber operating in a current mode. A comprehensive series of testing and calibration experiments have been carried out in a laboratory environment. An output signal of the device caused by the radon concentration in a sensitive detection volume significantly depends on a detector ventilation rate, the gas flow rate through the ionisation chamber. A set of calibration experiments was accomplished with the artificial radon source application and close circuit experimental arrangements. The system detection properties including applied experimental conditions and key results of pilot in situ measurements are reported in detail. 相似文献
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Ishimori Y Mitsunobu F Yamaoka K Tanaka H Kataoka T Sakoda A 《Radiation protection dosimetry》2011,146(1-3):31-33
A radon test facility for small animals was developed in order to increase the statistical validity of differences of the biological response in various radon environments. This paper illustrates the performances of that facility, the first large-scale facility of its kind in Japan. The facility has a capability to conduct approximately 150 mouse-scale tests at the same time. The apparatus for exposing small animals to radon has six animal chamber groups with five independent cages each. Different radon concentrations in each animal chamber group are available. Because the first target of this study is to examine the in vivo behaviour of radon and its effects, the major functions to control radon and to eliminate thoron were examined experimentally. Additionally, radon progeny concentrations and their particle size distributions in the cages were also examined experimentally to be considered in future projects. 相似文献
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针对主流的商用测氡仪器在测量低浓度氡时精度低的问题,基于新型离子脉冲电离室输出信号特点,设计了一种基于集成运算放大器TL071的高灵敏前置放大电路.该前置放大器由电流电压转换、放大电路以及时间常数相同的CR-RC积分、微分滤波成形电路构成.使用Multisim10对其增益、幅频特性、失真度、信噪比以及输入阻抗等性能进行仿真与测试,结果表明:此前置放大器能将pA级的电流信号转换为电压信号并放大到V级,输入阻抗约为105 MΩ,电路失真度理论值可以达到O%,信噪比可达到100 dB. 相似文献
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The new RAMARN system for radon volume activity measurement was developed in 2003 and has been in use since then. RAMARN system consists of a plastic chamber that is conically cylindrical in shape and about 0.5 l in volume; a bare Kodak LR 115 is located on the bottom of this diffusion chamber. The size was chosen to avoid the influence of deposited decay products of radon. Kodak has a spectrometric character-the tracks are visualized only for alphas with energies between 1 and 3 MeV that touch the foil; thus the effective volume has a lens shape. The response therefore corresponds to diffused radon and half of (218)Po born by radon gas decay. The experiments described below were conducted as one part of a routine methodology control, focused on classifying worker irradiation from natural ionizing radiation sources in show caves and in caves used for speleotherapy. 相似文献
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The Authorized Metrological Centre (AMS) working by SUJCHBO (National Institute for Nuclear, Chemical and Biological Protection) ensures for the Czech Republic the metrological traceability for devices that measure the radon concentration and the energy equivalent radon concentration connected with the radon decay products (RnDP). The evaluation and the calibration of measuring devices for radon and RnDP require the stable conditions (first of all radon and the RnDP concentrations). The new AMS radon-aerosol chamber in Kamenná consists of the walk-in testing chamber with a volume of 10 m(3) and of the handling box with a volume of 0.3 m(3). The design of the chamber allows measurement and a control of environmental parameters such as the temperature, the pressure of air inside and outside of the chamber, the relative humidity of air, the concentration and the size distribution of aerosol particles and the air velocity. 相似文献
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Ramola RC 《Radiation protection dosimetry》2011,146(1-3):11-13
Measurements of radon, thoron and their progeny were carried out in some houses from Garhwal and Kumaun Himalayas of India using a LR-115 plastic track detector. The measurements were made in various residential houses of the area at a height of 2.5 m above the ground level using a twin chamber radon dosemeter, which can record the values of radon, thoron and their progeny separately. The concentrations of radon and thoron in these homes were found to vary from 11 to 191 and 1 to 156 Bq m(-3), respectively. The equilibrium factor between radon and progeny varies from 0.02 to 0.90, with an average of 0.26 for the region. The resulting dose rate due to radon, thoron and their decay products was found to vary from 0.02 to 0.84 μSv h(-1) with an arithmetic mean of 0.27 μSv h(-1). A detailed analysis of the distribution of radon, thoron and their decay products inside a house is also reported. The observed dose rates due to radon, thoron and progeny were found somewhat higher but well below the international recommendations. 相似文献
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通过对传统的累积法测量氡析出率模型实验验证,发现得到的氡析出率明显偏低。对测氡仪器的工作原理与集氡罩中氡的浓度变化规律进行分析,发现是由于被测介质表面析出的氡不断进入集氡罩,218Po与氡没有平衡,造成测量的氡浓度明显偏低。通过非平衡修正得到了修正后的氡析出率测量理论模型。利用修正后的该模型得到的介质表面氡析出率与参考值符合得较好,误差小于7%。此外比较优值函数的取值也可发现:修正后的理论模型优值函数的取值小于传统模型,这表明修正后的理论模型更符合实际,该理论模型可应用于氡析出率仪的研制与改进。 相似文献
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Butterweck G Schuler Ch Vezzù G Müller R Marsh JW Thrift S Birchall A 《Radiation protection dosimetry》2002,102(4):343-348
An exposure methodology was developed for the determination of the absorption rate of unattached radon progeny deposited in the human respiratory tract to blood. Twenty-one volunteers were exposed in a radon chamber during well-controlled aerosol and radon progeny conditions, with predominantly unattached radon daughters. Special efforts were made to restrict the dose to the volunteers to an absolute maximum of 0.08 mSv. Measurements of radon gas and radon progeny in blood samples of these volunteers indicated absorption half times of 20 min to 60 min. Former determinations, mainly performed with much larger aerosol particles of diameters between 100 nm and 1,000 nm, implied absorption half times around 10 h. This indicates that the absorption of radon decay products from ciliated airways into blood is dependent upon particle size and particle composition. 相似文献
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To subserve the institutional research and tasks coming out from the Czech National Radon Programme, a new QA programme to calibrate all the known types of devices that measure radon and its short-lived progeny was developed at the Department of Radon mobile group of the National Radiation Protection Institute (NRPI) at Prague. The programme also included calibration of instruments measuring a unique quantity of unattached and attached fractions of short- lived radon progeny Generally, NRPI declares estimation of radon concentration during all routine calibration measurements with an overall uncertainty <5% (one sigma) and of equilibrium-equivalent radon concentration with an overall uncertainty <10% (one sigma). The results of the comparative measurements of the unattached and attached fractions of each short-lived radon progeny carried out with a comparing continuous monitor Fritra 4 in the German reference radon chamber at PTB Braunschweig indicated an acceptable level of agreement, up to 10%. 相似文献
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Bogacz J Mazur J Swakoń J Budzanowski M Olko P 《Radiation protection dosimetry》2002,101(1-4):267-270
A method of measurement of radon concentration in air was developed, based on high-sensitivity LiF:Mg,Cu,P (MCP-N, TLD Poland) thermoluminescent detectors installed in charcoal canisters. The canisters were exposed typically for 72 h in a calibration chamber with a radon concentration ranging from 100 Bq x m(-3) to 87 kBq x m(-3). It was found that in these conditions the signal registered by the TL detectors was proportional to the 222Rn concentration and the lowest limit of detection (LLD) was at a level of 100 Bq x m(-3). The proposed method can be used in large-scale, multi-site surveys aimed at screening for high levels of indoor radon concentration or for measuring ground radon exhalation rates. 相似文献
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Radon risk assessment is carried out by means of accurate measurements with active or passive instrumentation. All radon detectors must be calibrated and tested using a radon chamber containing a known concentration of radon produced by specific sources of (226)Ra. Some chambers can also be used to test the response of detectors as a function of environmental conditions. In this case, a calibration curve can be inferred with respect to change in one of the considered parameters. For this aim, a new radon chamber was designed and realised to perform calibration and to study the detector response in a large range of variation of the environmental parameters (pressure, 700-1100 mbar; temperature, 5-50°C; humidity, 10-90 %). The first experiments conducted to study the influence of environmental parameters on the detector response have shown flexibility and ease of use of the chamber. 相似文献