A new calibration method for radon detector in seismic systems

Radon observation is an important measurement item of seismic precursor network observation.The radon detector calibration is a key technical link for ensuring radon observation accuracy.At present,the radon detector calibration in seismic systems in China is faced with a series of bottleneck problems,such as aging and scrap,acquisition difficulties,high supervision costs,and transportation limitations of radon sources.As a result,a large number of radon detectors cannot be accurately calibrated regularly,seriously affecting the accuracy and reliability of radon observation data in China.To solve this problem,a new calibration method for radon detectors was established.The advantage of this method is that the dangerous radioactive substance,i.e.,the radon source,can be avoided,but only“standard instruments”and water samples with certain dissolved radon concentrations can be used to realize radon detector calibration.This method avoids the risk of radioactive leakage and solves the current widespread difficulties and bottleneck of radon detector calibration in seismic systems in China.The comparison experiment with the traditional calibration method shows that the error of the calibration coefficient obtained by the new method is less than 5%compared with that by the traditional method,which meets the requirements of seismic observation systems,confirming the reliability of the new method.This new method can completely replace the traditional calibration method of using a radon source in seismic systems.

Measuring^(222)Rn in aquatic environment via Pulsed Ionization Chamber Radon Detector

Radon(Rn)is a naturally occurring radioactive inert gas in nature,and^(222)Rn has been routinely used as a powerful tracer in various aquatic environmental research on timescales of hours to days,such as submarine groundwater discharge.Here we developed a new approach to measure^(222)Rn in discrete water samples with a wide range of^(222)Rn concentrations using a Pulsed Ionization Chamber(PIC)Radon Detector.The sensitivity of the new PIC system is evaluated at 6.06 counts per minute for 1 Bq/L when a 500 mL water sample volume is used.A robust logarithmic correlation between sample volumes,ranging from 250 mL to 5000 mL,and system sensitivity obtained in this study strongly suggests that this approach is suitable for measuring radon concentration levels in various natural waters.Compared to the currently available methods for measuring radon in grab samples,the PIC system is cheaper,easier to operate and does not require extra accessories(e.g.,drying tubes etc.)to maintain stable measurements throughout the counting procedure.

Assessment of Indoor Radon Concentrations in Dwellings for Baghdad Governorate by Using RAD-7 Detector

In the present work, radon gas concentrations in different dwellings in Baghdad governorate are measured by using RAD-7 detector. The results have shown that, the radon gas concentrations ranged between (40.67 ± 3.1 Bq/m3) to (190.00 ± 2.7 Bq/m3) with an average value (113.66 ± 30.2 Bq/m3);in the first one we draw the map radiations for indoor radon gas concentrations in Baghdad governorate. We would like to mention that the present study is considered to be very important and vital because it is concerned with people health and safety in the first place.

Measurement of Radon Gas Concentrations in Tap Water Samples for Thi-Qar Governorate Using Nuclear Track Detector (CR-39)

In the present work, we have measured the radon gas concentrations in tap water samples are taken directly from drinking tap water in sites houses being carried in Thi-Qar governorate by using nuclear track detector (CR-39). The results of measurements have shown that the highest average radon concentration in water samples is found in AL-Refai region which is equal to (0.223 ± 0.03 Bq/L), while the lowest average radon gas concentration is found in AL-Fajr region which is equal to (0.108 ± 0.01 Bq/L), with an average value of (0.175 ± 0.03 Bq/L). The highest value of annual effective dose (AED) in tap water samples is found in AL-Refai region, which is equal to (0.814 μSv/y), while the lowest value of (AED) is found in AL-Fajr region which is equal to (0.394 μSv/y), with an average value of (0.640 ± 0.1 μSv/y). The present results have shown that radon gas concentrations in tap water samples are less than the recommended international value (11.1 Bq/L). There for tap water in all the studied sites in Thi-Qar governorate is safe as for as radon concentration being concerned.

Radon Concentration in Soil and Radon Exhalation Rate at Al-Dora Refinery and Surrounding Area in Baghdad

Radongas concentrations in soil samples were determined from depths (surface, 15, and 30) cm for nine locations in Al-Dora refinery and surrounding area using “sealed can technique” and CR-39 solid state nuclear track detectors. The radon concentration in surface samples ranged from 810.08 to 1380.08 Bq/m3 with an average 1137.71 Bq/m3. The radon concentration in soil at the depth 15 cm was ranged from 490.5 to 1197.52 Bq/m3 with an average 732.78 Bq/m3 and at the depth 30 cm was ranged from 362.07 to 889.53 Bq/m3 with an average 529.41 Bq/m3. The surface exhalation rate in surface soil samples ranged was 0.44, to 0.99 Bq·m-2·h-1 with average 0.61 Bq·m-2·h-1. The surface exhalation rate in soil samples at the depth 15 cm was ranged from 0.22 to 0.64 Bq·m-2·h-1 with average 0.39 Bq·m-2·h-1. The surface exhalation rate in soil samples at the depth 15 cm was ranged from 0.22 to 0.64 Bq·m-2·h-1 with average 0.39 Bq·m-2·h-1. The surface exhalation rate and the mass exhalation rate in soil samples at the depth 30 cm ranged from 0.19, to 0.48 Bq·m-2·h-1 with average 0.28 Bq·m-2·h-1. The mass exhalation rate in surface soil samples ranged from 0.09 to 0.21 Bq·kg-1·h-1 with average 0.12 Bq·kg-1·h-1. The mass exhalation rate in soil samples from depth 15 cm was ranged from 0.046 to 0.14 Bq·kg-1·h-1 with average 0.08 Bq·kg-1·h-1. The mass exhalation rate in soil samples at the depth 30 cm was ranged from 0.042 to 0.1 Bq·kg-1·h-1 with average 0.06 Bq·kg-1·h-1.

Neutron activation analysis of ceramic tiles and its component and radon exhalation rate

The concentrations of 20 trace elements in several ceramics tiles and ceramic composites used in Egypt were elementally analyzed by neutron activation analysis(NAA) technique. The samples and standard were irradiated with reactor for 4 h(in the Second Research Egyptian Reactor(Et-RR-2)) with thermal neutron flux 5.9×10 13 n/(cm 2·s).The gamma-ray spectra obtained were measured for several times by means of the hyper pure germanium detection system(HPGe). Also a solid state nuclear track detector(SSNTD) CR-39, was used to measure the emanation rate of radon for these samples. The radium concentrations were found to vary from 0.39—3.59 ppm and the emanation rates were found to vary from (0.728—5.688) × 10 -4 kg/(m 2· s).The elemental analysis of the ceramic tiles and ceramic composites have a great importance in assigning the physical properties and in turn the quality of the material.

Radon Concentration Measurements in Gattar Uranium Prospect, Northern Eastern Desert, Egypt

The concentration of Radon in mines varies tremendously according to the country rock, type of mineralization and area. Ventilation is also an important factor. The absence of ventilation in mines tends to allow a higher concentration of Radon to build up. This is very dangerous for the miners work inside. In this present work, the radon gas concentration is practically measured in closed uranium prospect mine located at Gabal (G.) Gattar. CR-39 solid state nuclear track detector technique is used. It is found that the radon concentration is around 80 kBq m-3 and an effective ventilation rates should be applied if there will be further works in the future.

Study of Radionuclides and Radon Exhalation Rate in Soil and Sand Samples from Tiba, Luxor, Governorate

In this study, the natural radionuclides in soil and sand have been measured by using high purity germanium (HPGe) detector. While, radon exhalation rate has been measured by Alpha GUARD. The data analysis is performed to determine 226Ra, 232Th, and 40K activity concentrations in addition to 222Rn exhalation rate. The values of radium equivalent activity (Raeq), external hazard index (Hex), internal hazard index (Hin), and absorbed dose rate were ranged from 46.46 to 124.16 Bq⋅kg−1, 0.07 to 0.33 Bq⋅kg−1, 0.09 to 0.42 Bq⋅kg−1, and 13.24 to 58.37 nGy⋅h−1 respectively in all samples. The area and mass exhalation rates were increased from 9.16 ±2.83 to 16.18 ±2.83 Bq⋅m−2⋅h−1 and 1.8 ±1.34 to 11.35 ±0.98 Bq⋅kg−1⋅h−1 respectively.

Radon Dosimetry in Erbil City Hospitals

The aim of the study was to compare radon concentrations and effective dose equivalent in state hospitals inside the Erbil city having different periods of building. Effective doses were estimated in different floors of the five selected hospitals by using the （CR-39） solid state nuclear track detectors with the guide of 1CRP Publication 66. The hanged dosimeters were left for about 60 days and after etching the radon concentration, annual effective dose and effective dose equivalents were calculated. Annual effective doses were estimated as 〈 1 mSv, so the results reveal the present concentrations to be below the standard values in the studied hospitals. Therefore, no healthy risks concerning the radon activities are existing in the hospital staff and patients in these hospitals.

The Radon Indoor Concentration Measurement in AI-Sader City, Baghdad

This paper presents the results of indoor radon concentrations measurements in homes in A1-Sader city/Baghdad, Iraq. Radon cup technique was used, which is a cylindrical chamber 5 cm in diameter and height of 7 cm, contains solid state nuclear track detector CR-39, were distributed in 30 houses for thirty days. Results of radon concentrations show that the radon concentration is below the limit recommended by ICRP. The annual effective dose is ranged from 1.1600 to 2.1632 mSv y-1 and it＇s within the limits permitted by the ICRP. Equilibrium Equivalent Concentration （EEC） values were calculated and ranged from 14.72960 Bq/m3 to 27.45344 Bq/m3. However, the results show that indoor 222Rn exposure for samples were ranged from 0.003978 to 0.007413 work level （WL）, then the values of working level month （WLM） were calculated, the minimum value was 0.004978WLM and the maximum value was 0.009277 WLM. The radon induced lung cancer risk and the percentage of induced lung cancer risk were ranged from 13.53723 to 25.23106 per million persons, with an average of about 18.58738 per million persons.

Radon,Lung Cancer Risk and Environmental Geology in Gejiu Area

The incidence of lung cancer in the Gejiu area of Yunnan Province ranks the first inthe world. The radon level (indoor, soil) was measured in the Gejiu area by the SSNTDmethod from 1990 to 1996. The result indicates an extensive high-level of indoor radon in thatarea though U and Th are lower in local limestones. The indoor radon level of houses located inthe geologic fault zone is 6 times high that 2 km far from the fau1t zone. The reason probably isthat the radon level of soil in the fault is 6-8 times high that 1 km far from the faults. Ourdata indicate that a lower range of rad0n levels, 0 - 100 Bq’ m- 3, exists in healthy families.However, a higher radon level, over 800 Bq’ m- 3, is often f0und corresponding to that of can-cer patients’ homes (the house-owners are suffering from either lung cancer or leukaemia or liv-er cancer). Obviously, an increase in lung cancer incidence follows an increase in indoor radonlevel. The risk of cancer induced by indoor radon is no longer an inference, but a fact.

高氡浓度地震监测泉在标准仪器校准方法中的应用研究

基于水氡浓度为20000~100000 Bq·m^(-3)的新09泉、新10泉和新15泉,利用国际刻度参考装置Alpha GUARD测氡仪及其水氡测量组件,开展标准仪器传递校准实验研究,校准K值相对误差分别为3.60%、-0.81%及2.09%。实验结果与氡气固体源校准结果对比表明,水氡浓度在20000 Bq·m^(-3)以上水样可以通过标准仪器校准新方法检验,且利用不同水氡浓度的泉水不会影响校准结果准确性。新疆地球物理观测中心可利用高氡浓度的日常监测泉,将Alpha GUARD测氡仪作为标准仪器对FD-125型氡钍分析仪进行校准,从而替代固体氡源校准。本研究为地震监测氡观测的校准新方法操作技术规程及推广试用提供了数据支撑。

某酸法地浸铀矿山氡释放特征研究

以某酸法地浸铀矿山为对象,开展了酸法地浸采铀源项氡浓度、氡释放量,以及环境氡迁移扩散趋势等释放特征研究。采用E-Perm驻极体探测器法、固体径迹探测器法、RAD7静电收集测氡法,对地浸铀矿山抽液孔、集液罐、水冶厂通风口、蒸发池源项及周边环境的氡浓度进行了监测。结果表明,该地浸铀矿山氡释放量约为1.75 TBq/a,水冶厂通风口和集液罐是重要的氡释放源项,其年氡释放量分别占地浸铀矿山年氡释放量的58%和39%;抽液孔和蒸发池的年氡释放量约占地浸铀矿山年氡释放量的3%;集液罐开口处氡浓度水平最高,其对环境影响范围不超过500 m;抽液孔氡浓度水平最低。该酸法地浸矿山归一化氡释放量远小于地下矿山排风井的归一化氡释放量。

基于平板扫描仪的氡测量方法研究

CR-39固体径迹探测器因其材料的稳定性、良好的实用性等特点被广泛应用于氡的测量领域。针对现有的商用固体径迹探测器自动测读系统价格昂贵、维护成本及环境要求高的问题,本研究利用平板扫描仪设备,开展固体径迹形态学研究,通过建立基于径迹形态学参数的氡径迹识别法则,实现氡的高效、低成本测量。测量结果表明氡暴露量在500 kBq·h/m^(3)以下时,径迹密度-暴露量曲线呈现良好的线性关系。研究表明,基于平板扫描仪的氡测量方法有望实现氡的高效测量且该测读方法兼顾高效、低成本、环境适应性强的特点。

基于空气中氮气闪烁测氡方法的实验验证研究

本文建立了基于空气中氮气闪烁进行测氡的方法,该方法通过测量α粒子激发空气中的氮气后退激产生的紫外光来实现实时测量氡浓度的目的。针对空气中氮气闪烁光产额极低带来的探测效率低和易受噪声干扰的问题,在二重符合与阈值判选信号的基础上通过模拟优化来进行实验设计,并通过实验验证方案的可行性。首先,基于Geant4建立了空气中氮气闪烁测氡探测器的模拟模型,考虑到PMT暗噪声以及宇宙射线等本底的影响,采用了设置阈值和二重符合的方法抑制噪声,并通过模拟和理论研究了降噪的效果,然后通过优化探测器尺寸以实现对α粒子最高的探测效率。最后,搭建了基于空气中氮气闪烁测氡的实验平台,测试结果表明,探测器净计数率与RAD7测量所得氡浓度呈明显的线性关系,证明了基于空气中氮气闪烁测量空气氡浓度的可行性,经实验拟合,此探测器的灵敏度为0.010 27次/min/(Bq/m3)。该方法可满足采矿业、铀矿勘探等地下工程领域中对氡浓度水平实时在线监测的需求外,还可为无须采样且实时在线测量空气α气溶胶提供测量手段。

杯法测氡原理及应用

本文分析了α测氡方法及应用的现状 ,针对目前存在的问题 ,通过实验研究 ,提出了α杯法测氡技术。文中详细论述了α杯法测氡原理、功能、特点、工作方法和应用情况。结果表明 :α杯法测氡的灵敏度高、操作简单、效率高、成本低、能够为寻找基岩地下水、探测隐伏地质构造、解决工程地质问题等提供了可靠依据 。

利用α测氡技术寻找地下水

ＣＤ—１α杯法测氡技术是近年研究发展的新一代核地球物理方法技术，目前在找寻地下水，探测断裂地质构造、解决工程地质问题等领域得到了较成功的应用。该方法较好地解决了静电α卡法及其它放射性测氡方法在使用中存在的不足之处，更为合理有效。

低功耗电离室α测氡仪的设计

从软硬件设计角度介绍了α杯测氡仪低功耗设计的若干关键技术。该仪器以微处理器为核心,来完成数据采集、处理,显示、存储、通信等功能。给出了仪器的实际应用和综合评价参数。

CR-39探测器对α粒子入射角度和能量响应的实验研究

为掌握固体径迹探测器CR-39对α粒子的入射角度和能量响应特性,通过建立1个可调节α粒子的入射角度和入射能量的241Am源照射系统,进行了不同入射角度和入射能量的α粒子照射CR-39探测器的实验研究,比较了不同照射条件下的径迹密度。实验结果表明,CR-39对α粒子的能量响应下限约为0.5 MeV,对入射角度响应的上限约为70°。本研究结果可为优化设计测氡的扩散杯(瓶)、提高其对氡的探测效率等提供科学的指导依据。

空气氡浓度α能谱测量及影响因素

针对空气氡浓度测量需灵敏度高、稳定性好、能区分氡钍等特点,设计了一种基于空气氡静态扩散静电累积原理的α能谱测量装置及讨论了主要影响因素,并提出初步解决办法和进行了相应的实验。经过标准氡室的刻度,得到测量装置的能量刻度曲线、能量分辨率和测量灵敏度等重要信息。实验数据表明该方案理论可行,性能符合相关国家标准规定的对空气氡浓度检测的要求。