Direct measurements of radon activity in water from various natural sources using nuclear track detectors

Radon activities measured in several types of natural waters from the Santos region in Brazil are presented. Makrofol E polycarbonate plastic detector was used. The detector foils were exposed to radon emanating from the water samples for 30 days in a system of two tightly coupled cups, one of which contained the detector foil and the other hosted the analyzed water sample. After irradiation and chemical etching of the plastic foils, the tracks produced by the particles emitted by radon and its progeny were counted with a system consisting of an optical microscope and a video camera. The measured radon radioactivities ranged from 0.95 to 36.00 Bq/l for ground waters, from 0.30 to 0.54 Bq/l for sea waters, from 0.39 to 0.47 Bq/l for tap waters, from 0.43 to 2.40 Bq/l for river waters, and amounted to 2.35 Bq/l for water from the Santos/São Vicente public water supply.     

Application of the can technique and radon gas analyzer for radon exhalation measurements

A passive “can technique” and an active radon gas analyzer with an emanation container were applied for radon exhalation rate measurements from different construction materials, viz. five marble seven ceramic and 100 granite tiles used in Saudi Arabia. The marble and ceramic tiles did not show detectable radon exhalation using the active radon gas analyzer system. However the granite tiles showed relatively high radon exhalations, indicating a relatively high uranium content. A comparison of the radon exhalation rates measured by the two techniques showed a linear correlation coefficient of 0.57. The radon exhalation rates from the granites varied from 0.02 to 6.58 Bq m⁻² h⁻¹ with an average of 1.35±1.40 Bq m⁻² h⁻¹. The geometric mean and the geometric standard deviation of the frequency distribution were found to be 0.80 and 3.1, respectively. The track density found on the nuclear track detectors in the can technique exposed to the granites, having high exhalation rates, varied linearly with exposure time with a linear correlation coefficient of 0.99. This experimental finding agrees with the theoretical prediction. The can technique showed sensitivity to low radon exhalation rates from ceramic, marble and some granite over a period of 2 months, which were not detectable by the active radon gas analyzer system. The reproducibility of data with both measuring techniques was found to be within a 7% deviation.     

222Rn-220Rn累积探测器参加日本组织的国际比对结果分析

目的 通过参加国际比对,提高²²²Rn和²²⁰Rn累积测量的水平,保证测量的质量。方法 将本实验室的LD-P型²²²Rn-²²⁰Rn探测器寄往日本放射线医学综合研究所(National Institute of Radiological Science,NIRS),参加²²²Rn-²²⁰Rn累积探测器的国际比对。²²²Rn比对在NIRS的标准²²²Rn室进行,按暴露量分低、中、高3个水平;²²⁰Rn比对在NIRS的²²⁰Rn室进行,也分低、中、高3个水平。暴露结束后将探测器寄回本实验室进行蚀刻、分析,然后把测量结果报给NIRS,最后NIRS将暴露的参考值反馈回本实验室。结果 LD-P探测器²²²Rn比对测量低、中、高3个暴露水平的测量值与参考值的相对偏差(RPD)分别为-13.8%、-14.4% 和-17.1%;²²⁰Rn比对测量低、中、高3个暴露水平的测量值与参考值的RPD分别为-14.4%、 8.9%和-3.2%。结论 本次比对LD-P探测器²²²Rn和²²⁰Rn的测量结果均在NIRS规定的RPD为20%的一级标准范围内。     

Implications for analysis of 226Ra in a low-level gamma spectrometry laboratory due to variations in radon background levels

The background spectrum of HPGe detectors is found to vary significantly as function of the radon concentration in the air surrounding it, especially with regard to the count rates of ²²²Rn daughter peaks. This effect is shown to potentially have a large impact on measured values of radon daughter activity concentration, as well as detection limits for low-level measurements. As these radionuclides are commonly used for estimating the activity of ²²⁶Ra, care needs to be taken to ensure that background levels are accurately determined.     

Natural radioactivity and radon exhalation rate of soil in southern Egypt

The level of natural radioactivity in soil of 30 mining samples collected from six locations in southern Egypt was measured. Concentrations of radionuclides in samples were determined by γ-ray spectrometer using HPGe detector with a specially designed shield. The obtained results of uranium and thorium series as well as potassium (K-40) are discussed. The present data were compared with data obtained from different areas in Egypt.

Also, a solid state nuclear track detector SSNTD (Cr-39) was used to measure the radon concentration as well as exhalation rate for these samples. The radon concentrations were found to vary from 1.54 to 5.37 Bq/kg. The exhalation rates were found to vary from 338.81 to 1426.47 Bq/m²d. The values of the radon exhalation rate are found to correspond with the uranium concentration values measured by the germanium detector in the corresponding soil samples.     

Quantification of the dependency of radon emanation power on soil temperature

A study on the quantification of the dependency of the radon emanation power on soil temperature has been made using the accumulation method. The emanation from dry soil was studied at temperatures between −20°C and 45°C. A formula to calculate the radon emanation power as a function of the temperatures has been developed. The formula would contribute to the modeling of radon transport in soils and building materials.     

A method for reducing background tracks in plastic detectors

The purpose of the present study was to reduce background tracks by removing a given surface layer of the 250 μm thick lexan polycarbonate foils before exposure to alpha particles. Ethylenediamine solution was used for taking layers from the surface of the foils.     

氡气暴露后对机体肺功能及金属元素含量的影响

目的 探索暴露于高浓度氡气后对机体肺功能的影响及金属元素水平的扰动。方法 按随机数表法将小鼠分为对照组、氡暴露30 WLM组、60 WLM组、120 WLM组,每组10只。达到累积剂量后,用无创肺功能检测仪检测小鼠肺功能,采集各组小鼠血样、肺、心脏、肝脏、肾脏、脾脏组织。HE染色观察染氡小鼠肺组织病理改变,用电感耦合等离子体质谱(ICP-MS)检测组织中金属元素含量,包括机体必需微量元素:铬(Cr)、钼(Mo)、钴(Co)、硒(Se)、铜(Cu)、锌(Zn)、锰(Mn)、镍(Ni),以及具有潜在毒性的元素:砷(As)、锡(Sn)、铅(Pb)、铝(Al)、汞(Hg)、镉(Cd)、银(Ag)的含量。结果 与对照组相比,染氡组小鼠肺通气功能降低,肺泡结构破坏,肺部金属元素Cr、Al、Pb、Sn(F=0.34、0.66、3.14、1.16,P＜0.05)以及血液中必需微量元素Mn、Cr、Zn、Mo(F=0.65、1.44、0.97、2.08,P＜0.05)含量降低,而肺部Cu、Mo、Se、As元素升高(F=1.31、1.26、0.81、2.04,P＜0.05),其余组织中元素含量也有波动。结论 吸入一定累积剂量的氡气会降低小鼠的肺通气功能,破坏肺泡结构,并使肺和血液中必需微量元素含量降低,体内金属元素含量出现波动。     

吸入氡致大鼠肺蛋白质组表达变化的分析

目的 从蛋白质组学角度分析氡染毒后大鼠肺组织蛋白质表达谱的变化。方法 雄性Wistar大鼠氡吸入染毒累积剂量分别达100、200、400工作水平月(WLM)后,取大鼠肺组织,裂解提取其总蛋白;双向电泳(2-DE)分离总蛋白,ImageMaster 2D Platinum软件分析差异表达蛋白,切取差异蛋白点,胶内酶解并进行质谱(MALDI-TOF-MS)鉴定。结果 正常对照组和氡染毒组大鼠肺组织的2-DE图谱有明显差异,差异表达点中与氡染毒呈剂量变化关系的点有14个表达上调,9个表达下调,质谱鉴定出其中的15个差异蛋白点。结论 氡染毒组大鼠肺组织的蛋白表达谱发生了一定的差异性,氡吸入致靶器官肺损伤可能与多种蛋白相关。     

电离室灵敏体积对调强放射治疗剂量学验证准确性的影响

目的研究电离室灵敏体积对调强放射治疗绝对剂量验证的影响。方法将调强治疗计划移植到重建的数字化体模上计算吸收剂量，对单个照射野和整个计划，分别在等中心点、最大剂量点以及剂量梯度大和剂量分布均匀的区域选取一些有代表意义的剂量点，用0．6、0．125和0．015cc电离室在固体水体模中分别测量各点的吸收剂量，并与TPS计算值进行比较。结果等中心和剂量分布均匀区域，各电离室测量值与计算值的相对误差均在5％范围内；最大剂量点和剂量梯度较大区域，0．6cc电离室误差达到8％和12％，小体积电离室误差较小。结论0．6和0．125cc电离室可用于剂量梯度较小处的绝对剂量验证，在最大剂量点和剂量梯度大的区域，误差较大，0．015cc电离室较适用于调强放射治疗剂量验证。     

Experience of using MOSFET detectors for dose verification measurements in an end-to-end 192Ir brachytherapy quality assurance system

PurposeEstablishment of an end-to-end system for the brachytherapy (BT) dosimetric chain could be valuable in clinical quality assurance. Here, the development of such a system using MOSFET (metal oxide semiconductor field effect transistor) detectors and experience gained during 2 years of use are reported with focus on the performance of the MOSFET detectors.Methods and MaterialsA bolus phantom was constructed with two implants, mimicking prostate and head & neck treatments, using steel needles and plastic catheters to guide the ¹⁹²Ir source and house the MOSFET detectors. The phantom was taken through the BT treatment chain from image acquisition to dose evaluation. During the 2-year evaluation-period, delivered doses were verified a total of 56 times using MOSFET detectors which had been calibrated in an external ⁶⁰Co beam. An initial experimental investigation on beam quality differences between ¹⁹²Ir and ⁶⁰Co is reported.ResultsThe standard deviation in repeated MOSFET measurements was below 3% in the six measurement points with dose levels above 2 Gy. MOSFET measurements overestimated treatment planning system doses by 2–7%. Distance-dependent experimental beam quality correction factors derived in a phantom of similar size as that used for end-to-end tests applied on a time-resolved measurement improved the agreement.ConclusionsMOSFET detectors provide values stable over time and function well for use as detectors for end-to-end quality assurance purposes in ¹⁹²Ir BT. Beam quality correction factors should address not only distance from source but also phantom dimensions.     

中国室内氡行动水平的研究

目的　通过研究我国各类房屋中氡浓度的水平和分布 ,探讨适合我国国情的室内氡浓度的行动水平。方法　应用累积测量技术进行室内氡浓度的测量。结果　我国 18个城市普通房屋 (n =2 117)中氡浓度的算术平均值为 44 1Bq·m- 3 ,其中超过 10 0Bq·m- 3 、2 0 0Bq·m- 3 和 40 0Bq·m- 3 的房屋分别占测量总数的 6 5%、1 0 %和 0 1%。煤渣砖建筑物、窑洞和地下建筑物分别有14 1%、16 7%、2 7 3 %和 2 3 %、3 0 %、4 0 %的房间中氡浓度超过 2 0 0Bq·m- 3 和 40 0Bq·m- 3 。我国2 0个省市实测的平衡因子均值为 0 49。结论　建议氡行动水平的单位由平衡等效浓度改为氡的实测浓度 ;取消新建住房和已有住房的划分 ;在未进行国家氡水平调查前 ,我国室内氡的行动水平可继续沿用GB T 1614 6 1995给出的已有住房 40 0Bq·m- 3 的控制水平     

Determination of dead-layer variation in HPGe detectors

The dead-layer uniformity of the top surface of two high purity germanium detectors has been studied using a novel automated scanning set-up that allows a fine-grained topography of a detector's top and lateral surfaces. Comparisons between measurements and Monte Carlo simulations allowed implementation of a dead-layer variation into the detector model, which reproduces the measurements results. The effect of the non-uniform dead-layer on activity determinations based on low-energy γ-rays (i.e. below ~100 keV) has been determined to be of the order of 10% or more.     

Health effects of radon: A review of the literature

Purpose:?Radon is natural radioactive noble gas that can be found in soil, water, outdoor and indoor air. Exposure to radon accounts for more that 50% of the annual effective dose of natural radioactivity. The purpose of the current review is to summarize recent literature and evaluate the weight of evidence on the adverse health effects of radon.

Conclusions:?Radon is an established human lung carcinogen based on human epidemiological data supported by experimental evidence of mutagenesis studies in cell culture and laboratory animals. Extrapolation from cohort studies on miners suggested that radon is the second leading cause of lung cancer death after tobacco smoke. The majority of studies on the relationship between radon and other types of cancers showed weak or no association. Low levels of radon can be found in drinking water; however, radon released during water usage adds small quantities to indoor radon concentration. Studies showed that the risk of stomach cancer and other gastrointestinal malignancies from radon in drinking water is small. Studies of the genetic and cytogenetic effects of indoor radon yielded equivocal results; while radon exposure in miners induces gene mutations and chromosomal aberrations. Numerous in vitro cytogenetic studies demonstrated that radon induces different types of genetic and cytogenetic damage that is likely to play a role in radon lung carcinogenesis.     

典型非铀矿山工人氡危险认知研究

目的 调查非铀矿山工人对氡所致健康危害的认知水平及影响因素。方法 采用当面填写调查表或询问方式调查了9个省区24个矿山的2836名矿工。结果 13.3%的矿工知晓氡,其中,29.0%的人知道氡的来源,8.5%的矿工对氡危害有一定认识,仅有1.8%的矿工对氡致健康危害有正确认知。在影响非铀矿山工人对氡致健康危害正确认知水平的因素中,受教育程度与氡认知水平正相关;正式职工对氡的认知水平优于临时雇用工人;性别、年龄、从事现工作的工龄等因素对氡认知水平没有明显影响;不同省区及矿山的氡认知水平不同。结论 我国非铀矿山矿工对氡危险认知水平较低,应进一步落实并规范《职业病防治法》规定的职业危害告知义务。     

Variation of radon exposure in Damascus dwellings

In the present work, activity concentrations of ²²²Rn in air and ²²²Rn and ²²⁶Ra in drinking water were measured in Damascus city covering its old and modern parts.It was found that the average air radon activity concentration in the old part was higher than in the modern part, and in drinking water, radon was found to be 60±3 Bq/l, and less than 0.13 Bq/l for radium, which were lower than the recommended levels set by WHO.     

氡暴露致小鼠骨髓细胞的DNA损伤

目的 研究氡暴露致小鼠骨髓细胞的DNA损伤。方法 采用雄性BALB/C小鼠24只,随机分为4组,每组6只,除对照组外,处理组小鼠整体暴露于多功能生态氡室,吸入氡及其子体的累积剂量分别为27(低剂量组)、52(中剂量组)和105(高剂量组)工作水平月(WLM)。采用单细胞凝胶电泳(SCGE)、微核(MN)实验、激光共聚焦显微镜(LSCM)检测小鼠骨髓细胞的DNA链断裂、微核细胞率及凋亡率,观察氡暴露致小鼠骨髓细胞的DNA损伤。结果 高剂量氡暴露可造成小鼠骨髓细胞DNA断裂,尾长和尾DNA百分含量与对照组相比,差异有统计学意义(F=201.9,40.78,P<0.05);微核率和凋亡率增加差异有统计学意义(F=16.28,41.62,P<0.05)。而中、低剂量组则无明显改变。结论 高剂量氡暴露引起DNA损伤,从而对小鼠骨髓细胞产生毒效应。     

Characterization of the Oum Er Rbia (Morocco) high basin karstic water sources by using solid state nuclear track detectors and radon as a natural tracer

Uranium and thorium contents as well as radon -activities per unit volume were evaluated inside different water samples by using a method based on calculating the CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs) detection efficiencies for the emitted -particles and measuring the resulting track density rates. The validity of the SSNTD technique utilized was checked by analysing uranyl nitrate (UO₂(NO₃)₂6H₂O) standard solutions. A relationship between water radon concentration and water transmission of different water sources belonging to two regions of the Middle Atlas (Morocco) water reservoir was found. The influence of the water flow rate as well as the permeability and fracture system of the host rocks of the sources studied was investigated.     

某市两座地下水处理厂氡浓度初步调查与分析

目的 通过对水和空气中氡浓度的测量,初步调查水氡释放对水厂空气氡的影响.方法 选取某市的两座地下水处理厂,采集水厂的水源水、出厂水和末梢水.利用连续测氡仪快速水氡测量方法,测量水中氡浓度;采用固体径迹探测器,累积测量水厂不同区域空气氡浓度.结果 两座水处理厂水源水、出厂水和末梢水中氡浓度分别为:(7.59±1.36)、(3.56±0.86)和(3.68±0.81)Bq/L与(12.19±0.57)、(7.87±1.12)和(9.50±1.12)Bq/L.水源水最高,出厂水与末梢水相近.跌水曝气和开放式过滤工艺能明显降低水中氡含量.曝气室和过滤车间氡浓度分别高达4 218和1 937 Bq/m³,明显高于我国工作场所氡浓度限值1 000 Bq/m³.结论 地下水处理厂曝气车间和开放式过滤车间氡浓度受到水氡释放的影响,我国地下水处理厂氡的问题应该引起重视.     

深圳新建住宅室内氡水平及分布特征

目的 初步调查深圳市新建住宅室内氡水平及分布特征。方法 选择深圳市低层、多层、中高层和高层结构住宅108户,采用固体径迹法累积测量室内氡浓度。结果 深圳市居室内氡浓度算数均值为64 Bq/m³,几何均值为58 Bq/m³,范围15~155 Bq/m³;宝安区室内氡浓度均值最低,为50 Bq/m³,坪山新区室内氡浓度均值最高,为87 Bq/m³。深圳室内氡浓度 > 100 Bq/m³的测量点有12个,占总数的11.1%。Shapiro-Wilk检验表明,深圳室内氡浓度频数分布呈对数正态分布（P > 0.05）。建筑年代为1990—2015年的房屋,室内氡浓度随建筑年代呈降低趋势。除10层及以上,室内氡浓度随楼层的升高呈降低趋势。结论 本次调查比以往调查深圳市室内氡浓度相比升高了35%。建议继续加强完善建材放射性标准,加强高层住宅的自然通风,降低室内氡的辐射危害。