我国非铀矿山222Rn、220Rn浓度季节变化研究

目的 研究非铀矿山中²²²Rn、²²⁰Rn浓度的季节变化规律。方法 选取云南、山东、新疆、黑龙江、湖南和贵州6个省份的铜、金、铝、锰、锑、钨、铜镍和煤矿共8类9个矿山,采用LD-P型²²²Rn-²²⁰Rn分辨探测器对井下不同季节²²²Rn和²²⁰Rn浓度进行了测量。结果 井下²²²Rn浓度存在明显的季节变化,夏季²²²Rn浓度为35.5~4841 Bq/m³,其中4个矿²²²Rn浓度均值超过1000 Bq/m³。冬季²²²Rn浓度均值为5~1917Bq/m³,只有1个矿超过1000Bq/m³。夏季与冬季的比值在2~12之间。各矿间²²²Rn浓度差异很大,通风是影响其变化的重要因素。²²⁰Rn浓度的季节变化略呈夏高冬低的趋势,由于受到布放位置的影响,其规律性有待进一步确认。结论 井下²²²Rn、²²⁰Rn浓度随季节而变化,在估算矿工受照剂量时应考虑季节变化的影响;在矿山氡测量中应避免采用瞬时测量方法;采用累积测量方法时,也应考虑季节变化的影响,合理的暴露时间应为半年,同时要注意季节的选择;对于季度性(3个月)的测量结果应该进行季节修正。     

我国非铀矿山222Rn和220Rn水平初步调查研究

目的 测量非铀矿山²²²Rn、²²⁰Rn水平,了解我国矿山氡超标比率和矿工受照剂量。方法 根据典型抽样方法选择12个省17类44座矿山,采用LD-P分辨型探测器测量²²²Rn、²²⁰Rn累积浓度。结果 ²²²Rn、²²⁰Rn浓度呈对数正态分布,金属矿(25座,147处)²²²Rn浓度算数均值(AM)和几何均值(GM)分别为(1211±2359)和(311±5.5) Bq m³;²²⁰Rn浓度AM和GM分别为(269±700)和(71±4.4) Bq m³。非金属矿(18座,118处)²²²Rn浓度AM和GM分别为(98±207)和(55±2.5) Bq m³;²²⁰Rn浓度AM和GM分别为(60±76)和(38±2.4) Bq m³。测量地下矿井40处,其中6处²²²Rn浓度均值超过1000 Bq m³ (工作场所氡浓度限值),占抽样率15.0%;约有7%测点²²²Rn超过浓度3700 Bq m³ (我国铀矿冶氡浓度限值),个别测点超过10 000 Bq m³。井下和地面工作区室内²²²Rn平衡因子分别为0.33±0.15和0.47±0.18。²²⁰Rn平衡因子的波动范围较大,为0.001～0.032。地下矿山矿工的年均受照剂量约为8.15mSv。结论 我国金属矿山特别是有色金属矿井下²²²Rn浓度偏高的问题依然严重,值得关注和进行跟踪研究。     

浙江部分地区室内222Rn和220Rn水平及剂量估算

目的 调查浙江省余杭区和三门县居室内²²²Rn、²²⁰Rn及其子体水平,明确其所致公众有效剂量。方法 采用固体径迹探测器测量余杭区和三门县两地居室中²²²Rn和²²⁰Rn浓度,探测器均放置于卧室或客厅,在不改变居民日常通风习惯情况下连续暴露6个月。结果 不同房屋类型室内²²²Rn和²²⁰Rn测定,均显示平房室内氡浓度最高。室内²²²Rn浓度与不同建筑年代无关(F =0.53, P >0.05),而室内²²⁰Rn浓度与不同建筑年代有相关性(F =3.56, P <0.05)。室内²²⁰Rn浓度未装修居室高于装修居室(t =2.33, P <0.05)。余杭区调查的居室内平均²²²Rn浓度为32.5 Bq/m³,²²⁰Rn为314.3 Bq/m³,所致有效剂量分别为0.88 和0.42 mSv;三门县调查的居室内平均²²²Rn浓度为26.8 Bq/m³,²²⁰Rn为399.5 Bq/m³,有效剂量分别为0.72 和0.53 mSv。结论 浙江余杭和三门室内²²²Rn浓度属正常天然本底水平,两地农村居室内²²⁰Rn浓度较高,²²⁰Rn及其子体的剂量贡献超过了²²²Rn及其子体引起的年有效剂量的50%。     

云南省部分地区大米和玉米放射性核素水平调查

目的 调查云南省部分地区大米和玉米放射性核素水平,充实云南地区食品放射性水平基线数据,评估其对居民产生的健康风险。方法 依据国家标准《生物样品中放射性核素的γ能谱分析方法》《高纯锗γ能谱分析通用方法》《食品中放射性物质检验总则》《土壤中放射性核素的γ能谱分析方法》,对云南省20个县（区）大米和玉米样品进行放射性核素检测,对检测结果进行处理与分析。结果 大米样品中²³⁸U、²³²Th、²²⁶Ra、⁴⁰K和¹³⁷Cs活度浓度均值分别为（0.416±0.403）、（0.045±0.034）、（0.030±0.013）、（28.4±18.8）和（0.014±0.019）Bq/kg,玉米样品中²³⁸U、²³²Th、²²⁶Ra、⁴⁰K活度浓度均值分别为（0.308±0.230）、（0.035±0.031）、（0.053±0.072）、（56.8±38.6）Bq/kg,¹³⁷Cs的活度浓度低于探测下限。结论 云南省20个县（区）大米和玉米中²³⁸U、²³²Th、²²⁶Ra、⁴⁰K和¹³⁷Cs的放射性水平均在国家标准正常范围内,食入后不会对居民的健康造成影响。     

2017—2018年北京地区土壤的放射性水平监测与分析

目的 调查北京地区19处土壤中放射性核素的含量,为准确评价北京地区环境放射性污染提供科学依据。方法 2017—2018年连续采集北京16个区的38份土壤样品,使用GEM-MX7080P4型高纯锗γ能谱仪对样品中放射性核素²²⁶Ra、²³²Th、⁴⁰K和¹³⁷Cs的比活度进行监测。结果 19处土壤样品中放射性核素²²⁶Ra、²³²Th、⁴⁰K的比活度平均值连续两年分别为23.9和24.1 Bq/kg、31.2和31.7 Bq/kg、600和578 Bq/kg;¹³⁷Cs的比活度平均值两年均为1.21 Bq/kg,最高值分别为5.48和6.18 Bq/kg,约为当年平均值的4.5和5.1倍。结论 北京地区19处土壤样品中²²⁶Ra、²³²Th、⁴⁰K和¹³⁷Cs的含量在本地区和国内环境本底范围内,土壤中¹³⁷Cs主要来源于既往的核活动或核事故。     

222Rn-220Rn分辨探测器参加国际比对结果分析

目的 提高²²²Rn与²²⁰Rn的累积测量水平,保证测量结果的准确性与可靠性。方法 采用中国疾病预防控制中心辐射防护与核安全医学所的氡课题组（以下简称本实验室）改进的LD-P型²²²Rn-²²⁰Rn分辨探测器参加日本放射线医学综合研究所（NIRS）组织的²²²Rn-²²⁰Rn累积探测器国际比对。将²²²Rn-²²⁰Rn分辨探测器寄往日本,在NIRS的²²²Rn室和²²⁰Rn室进行不同条件下的比对,暴露结束后再寄回本实验室进行蚀刻与分析,测量结果告知NIRS。最后NIRS将²²²Rn与²²⁰Rn暴露参考值回馈本实验室。结果 在高²²²Rn和低²²²Rn条件下,测量值与NIRS提供的参考值的相对百分偏差（RPD）分别为-12.0%、-11.8%;变异系数（COV）分别为3.0%、6.2%。在高²²⁰Rn和低²²⁰Rn条件下,测量值与NIRS提供的参考值的相对百分偏差（RPD）分别为-0.8%、-8.0%;变异系数（COV）分别为6.7%、4.5%。结论 本次比对LD-P型探测器²²²Rn与²²⁰Rn的测量结果均为NIRS规定的Ι级结果（PRD<10%）,比对结果较好。     

北京地区土壤中232Th、225Ra、40KTh浓度及其对天然γ辐射剂量的贡献

为调查北京地区外环境中来自地层的天然放射性核素的辐射剂量,在用现场辐射仪测量的同时,用φ75×75mm NaI (T1)-塑料反符合低本底γ谱仪,分析了北京地区143个土壤样品.结果表明,北京地区表层土壤中²³²Th、²²⁶Ra和⁴⁰K浓度随地点、地形、成土母质类型有很大变化,东南平原和西北山区,²³²Th和²²⁶Ra浓度差别不显著,而⁴⁰K浓度在α=0.001水平上有显著差异;按成土母质区分,岩浆岩和沉积岩⁴⁰K和²³²Th均有显著差异.     

云南某铀矿退役环境保护区周边食品放射性水平分析

目的 调查云南省某铀矿退役环境保护区周边食品放射性水平,及时发现和预警放射性物质的释放情况,为食品放射性水平监测积累基线数据。方法 监测铀矿退役环境保护区周边3 km范围内20个采样点的粮食、蔬菜和鲜茶叶的放射性水平。样品经现场预处理、实验室制备后,进行放射性核素γ能谱分析。结果 食品中的放射性核素主要包括天然放射性核素²³⁸U、²³²Th、²²⁶Ra、⁴⁰K和人工放射性核素¹³⁷Cs。²³⁸U、²³²Th、²²⁶Ra和⁴⁰K比活度平均值分别为（0.17±0.05）、（0.25±0.17）、（0.43±0.28）和（103.49±25.10）Bq/kg（鲜重）,鲜茶叶中的²³²Th、²²⁶Ra、⁴⁰K和¹³⁷Cs放射性水平均高于粮食和蔬菜。结论 铀矿退役环境保护区周边食品的放射性水平均低于国家标准限值。除微量¹³⁷Cs外,未检出其他人工放射性核素。     

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。     

湖北地区室内外空气中氡及氡衰变子体浓度的调查

用抓样调查法,在全省83个调查点,随机测定了380间房屋内的²²²Rn和1920间房屋内的²²²Rn子体潜能浓度。结果表明,它们的浓度频率分布近似对数正态分布；全省室内²²²Rn的几何均值为17.5Bq·m^-3222Rn子体潜能为2.1mWL; 90%以上被调查房间内的平衡等效²²²Rn浓度在16Bq·m^-3以下,超过46Bq·m^-3以上的房间只占1%,约半数房闻内的浓度在7.4mt·mq^-3以下。此外还测定了部分房屋内、外的。加的²²⁰Rn子俸潜能浓度。全省成人居民受室内、外²²²Rn和²²⁰Rn子体照射的人均年有效剂量当量为0.82mSv,集体年有效剂量当量约为4×10⁴人·Sv.     

Investigation of natural radioactivity levels in water around Kadugli, Sudan.

Surface water from Miri Lake and groundwater from around Kadugli (West-Central Sudan) obtained by means of hand-pumps was analysed for (238)U, (226)Ra, (222)Rn, and (232)Th activity concentrations. The surface water showed very low levels of radionuclide concentrations: <1.0-7.5, 8.5-16.5, <1.6, and <0.1-0.39mBqL(-1) for (238)U, (226)Ra, (222)Rn, and (232)Th, respectively. Groundwater revealed a significant amount of natural radioactivity (16.1-1720, 7.7-14.3, 3000-139,000, <0.1-39mBqL(-1)) respectively. The overall annual effective dose was below the WHO reference dose level of 0.1mSvyr(-1) except in one groundwater sample with an associated dose of 0.7mSvyr(-1).     

The natural radioactivity in Guarani aquifer groundwater, Brazil.

The measurements of gross alpha and gross beta radioactivity in groundwater samples from Guarani aquifer in Brazil are reported in this paper together with the activity concentration of the natural dissolved radionuclides (40)K, (238)U, (234)U, (226)Ra, (222)Rn, (210)Po, (210)Pb, (232)Th, (228Th), and (228)Ra. Most of the gross alpha radioactivity values were below the critical level of detection corresponding to 1mBq/L, however, the whole data set for the gross beta radioactivity and radionuclides (40)K, (238)U, (234)U, (226)Ra, (222)Rn, (210)Po, (210)Pb, and (228)Ra was submitted to a statistical treatment, considering class intervals arranged in geometric progression, because of the great variability of the activity. The analysis indicated lognormal distribution of the data, as usually observed in samples taken from the natural context. An inverse relationship between the gross alpha and gross beta activity has been identified and is related to an increase in the K content in the water. The mobility coefficient has been estimated for (238)U, (226)Ra, (232)Th and (228)Ra in Guarani aquifer and the results indicated that the radioelement solubility in the studied system varies according to the following order: radium>uranium>thorium. The implications of the data obtained in terms of standards established for defining the drinking water quality have also been discussed.     

Natural radioactivity and gamma dose from Sri Lankan clay bricks used in building construction.

The specific radioactivity concentrations of 226Ra, 232Th and 40K have been determined by gamma ray spectrometry with an HPGe detector in clay brick samples from kiln sites located in 17 towns. The average values of the measured activities are 35, 72, and 585 Bq kg(-1), respectively, for the above radionuclides. The average estimated radium equivalent concentration is 183 Bq kg(-1) and is comparable with reported values for many countries in the world. This value and the value obtained from the criteria formula suggest that the use of local clay bricks do not pose a radiological hazard. The calculated average absorbed dose rate in air within buildings was found to be 102 nGy h(-1) while the population weighted indoor annual effective dose was 0.20 mSv.     

Accounting for 222Rn loss during oven drying for the immediate laboratory gamma-ray spectroscopy of collected soil samples.

Drying soil samples in an oven to remove water alters the 222Rn emanation rate. Measurements of the oven drying 222Rn emanation rate from soil were made with a continuous radon monitor and the degree of 222Rn disequilibrium was quantified by laboratory gamma-ray spectroscopy. This paper presents a disequilibrium correction where the 226Ra activity in oven-dried soil samples is inferred from immediate laboratory gamma-ray spectroscopy of 214Bi before 222Rn and its decay progeny reach secular equilibrium.     

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.     

Automated measurement of 224Ra and 226Ra in water.

We present a new simple approach for automated, non-destructive measurement of the alpha-emitting radium isotopes ((223)Ra, (224)Ra, and (226)Ra) in water based on the emanation of their respective radon daughters ((219)Rn, (220)Rn, and (222)Rn). The method combines the high adsorption uptake of MnO(2) Resin for radium (K(d)=2.4 x 10(4)ml/g) over a wide pH range with the simplicity of the activity registration using a commercial radon-in-air analyzer (RAD7, DURRIDGE Company, Inc). Radium is first adsorbed onto the MnO(2) Resin by passing a water sample through the resin packed in a gas-tight glass cartridge. The same cartridge is then connected to the radon analyzer via a simple tubing system to circulate air through the resin and a drying system. The efficiency of the proposed system is determined by running standards prepared in the same manner. Our results indicate that the efficiency for (226)Ra is >22% if both (218)Po and (214)Po counts are collected. This is comparable with typical efficiencies for alpha spectrometry but with much less sample preparation. We estimate that an MDA of 0.8 pCi/L for (226)Ra may be obtained with this new approach using a 1L water sample and less than 4h of counting.     

Natural radioactivity in Algerian building materials.

Samples of natural and manufactured building materials collected from Algiers have been analysed for 226Ra, 232Th and 40K using a high-resolution HPGe gamma-spectrometry system. The specific concentrations for 226Ra, 232Th and 40K, from the selected building materials, ranged from (12-65 Bq kg(-1)), (7-51 B qkg(-1)) and (36-675 Bq kg(-1)), respectively. The measured activity concentrations for these natural radionuclides were compared with the reported data of other countries and with the world average activity of soil. Radium-equivalent activities were calculated for the measured samples to assess the radiation hazards arising from using those materials in the construction of dwellings. All building materials showed Ra(eq) activities lower than the limit set in the OECD report (370 Bq kg(-1)), equivalent to external gamma-dose of 1.5 mSv yr(-1).     

Activity measurements of radon from construction materials

This work presents the results of radon concentration measurements of construction materials used in the Brazilian industry, such as clay (red) bricks and concrete blocks. The measurements focused on the detection of indoor radon activity during different construction stages and the analysis of radionuclides present in the construction materials. For this purpose, sealed chambers with internal dimensions of approximately 60×60×60 cm3 were built within a protected and isolated laboratory environment, and stable air humidity and temperature levels were maintained. These chambers were also used for radon emanation reduction tests. The chambers were built in four major stages: (1) assembly of the walls using clay (red) bricks, concrete blocks, and mortar; (2) installation of plaster; (3) finishing of wall surface using lime; and (4) insulation of wall surface and finishing using paint. Radon measurements were performed using polycarbonate etched track detectors. By comparing the three layers applied to the masonry walls, it was concluded that only the last step (wall painting using acrylic varnish) reduced the radon emanation, by a factor of approximately 2. Samples of the construction materials (clay bricks and concrete blocks) were ground, homogenized, and subjected to gamma-ray spectrometry analysis to evaluate the activity concentrations of 226Ra, 232Th and 40K. The values for the index of the activity concentration (I), radium equivalent activity (Raeq), and external hazard index (Hext) showed that these construction materials could be used without restrictions or concern about the equivalent dose limit (1 mSv/year).