铀尾矿粒度对氡析出影响的蒙特卡罗模拟

基于核反冲理论建立了铀尾矿氡析出的数学模型和蒙特卡罗模拟方法,模拟了不同含水饱和度条件下铀尾矿颗粒粒度对氡析出的影响。结果表明,镭分布于颗粒表面时,4种含水饱和度（5%、20%、50%、75%）条件下的K均随颗粒尺寸的增大先增大后趋于稳定。镭分布在距颗粒表面34 nm和68 nm时,含水饱和度为5%或20%的条件下,K先增加后趋于稳定,而含水饱和度为50%或75%的条件下,K随颗粒尺寸的增大先稍有下降然后逐渐稳定。运用蒙特卡罗方法计算了各铀尾矿样品的氡析出率,计算的氡析出率与实测铀尾矿氡析出率符合较好,相对误差为3%～9%。     

Distribution and Characteristics of Radon Gas in Soil from a High-Background-Radiation City in China

A soil survey using a portable radon monitor employing semiconductor alpha spectroscopy has been performed on a large scale to determine the distribution of radon in soil in Zhuhai City, Guangdong Province. The survey with 469 samplesites covered an area of more than 100 km². The average soil radon concentrations at a depth of 0.6m were 55:94±58:54 kBqm^?3 in the Zhuhai Urban Area (ZUA) and 7:14±8:75, 37:64±25:92, and 151:25±196:23 kBqm^?3, respectively, in the Quaternary sediment, mixtures of sediment and weather grain of granite, and weathered granite in Doumen District. The areas with high radon potential were located within areas of biotitic granites and new developing industrial districts, as indicated by a strong correlation between the radioactivity level and geological lithology. The mean radon concentration in ZUA is about ten times higher than those in Guangzhou City, Quanzhou City, and Jinjiang City. The results show that the Zhuhai area has a higher radon potential, and protective measures against radon should be considered.     

土壤潜势氡浓度快速测量方法理论模型的建立与验证

与室内氡水平直接相关的是土壤潜势氡浓度（土壤中潜在的最大氡浓度）,其直接测量深度通常需数米,测量非常困难,需探索快速获得土壤潜势氡浓度的方法。本工作通过对土壤氡运移规律的深入研究,建立了一个由土壤浅层氡浓度和土壤表面氡析出率确定土壤潜势氡浓度（双源法）的理论模型,并加以实验验证。实验证明了该理论模型的可靠性。该理论模型的建立为土壤潜势氡浓度快速测量方法的进一步研究奠定了基础。     

Effect of Soil Moisture Content on Radon and Thoron Exhalation

In this study, the authors considered the effect of soil moisture in the emanation process of radon and thoron gases. Weathered granite soil was selected as the test soil and it was packed in a polypropylene container (275 × 210mm² and 100mm in height), up to 50mm in depth from the bottom. The container was covered with the exhalation rate measuring instrument adopting the accumulation method and γ-particles were counted at 30 s intervals for 30 min to estimate the exhalation rates. A sporadic increase in the radon and thoron exhalation rates was caused by the increase in the moisture content up to 8%. However, the exhalation rates showed a decreasing tendency with the increase in moisture content over 8%. Although the measured radon exhalation rate was about 25% of the calculated one, both measured and calculated radon exhalation rates had similar trends with an increase in the moisture content in the soil. The measured thoron exhalation rate agreed well with the calculated one. When the moisture content was in the range of 3.5–18%, it was considered that applying the correlation between the moisture content and the measured thoron exhalation rate is useful for estimating the thoron effective diffusion coefficient.     

Suppression of Radon Exhalation from Soil by Covering with Clay-mixed Soil

The effectiveness of bentonite-mixed soil as a barrier to radon exhalation from soil is investigated experimentally at a closed uranium mine in Japan. Continuous observations of radon flux from a clay-covered soil surface and a bare soil surface were conducted for a period of 80 days. The mean radon flux from the clay-covered plot was one fifth of that from the bare plot, demonstrating that the clay-mixed soil is effective as a boundary suppressing radon exhalation from the contaminated soil. Numerical analyses using a one-dimensional radon transport model for an unsaturated soil for the dry weather conditions confirmed the effectiveness of the clay-mixed soil cover under a range of weather conditions.     

加气混凝土砌块表面氡析出率影响因素研究

使用RAD7和建材氡析出率测试舱,对加气混凝土砌块表面氡析出率随其尺寸、样品数量及含水率的变化规律进行了实验研究。结果表明：在测试舱中放入样品的数量对被测样品的表面氡析出率几乎无影响;在同一测试舱中,当加气混凝土砌块的体积不变、表面积增加时,加气混凝土砌块的表面氡析出率减少,但加气混凝土砌块表面在单位时间内的氡析出总量不变;对于加气混凝土砌块,其表面氡析出率与其含水率的增加呈对数增长关系。     

含氡放射性水体氡析出规律的理论研究

利用氡扩散运移理论,建立了水体内氡迁移的一维微分方程,推导了水中氡浓度及水体表面氡析出率的计算公式;研究了水底射气介质氡析出率、氡传输速率、水中氡扩散系数以及水体深度等参数对水中氡浓度和水体表面氡析出率的影响。结果表明:在其他参数保持不变时,(1)同一深度处的水中氡浓度和水体表面氡析出率均随水底射气介质氡析出率的增大而增大;(2)同一深度处的水中氡浓度随氡传输速率的增大而减小,而水体表面氡析出率随氡传输速率的增大而增大,且当氡传输速率大于1×10-6m/s时,氡传输速率的变化对水体表面氡析出率的影响不明显;(3)同一深度处的水中氡浓度和水体表面氡析出率均随水中氡扩散系数的增大而增大;(4)水体表面处的水中氡浓度和水体表面氡析出率均随水体深度的增大而减小。     

Modeling Radon Flux Density from the Earth's Surface

In order to make the idealized model for predicting soil radon flux more practically and accurately, two central variables (radon emanation power and soil water content) controlling the amount of radon transportation in soil were formulated. The reformulated model for predicting radon flux density was verified by the field measurements carried out in 10 different sites. The result indicates that the reformulated model is useful for improving the prediction feasibility and accuracy of radon flux density from the earth's surface.     

水浸颗粒堆积型射气介质氡析出规律的理论研究

铀尾矿库和地表浸铀铀矿堆是一种颗粒堆积型射气介质,其水位的变化和覆水厚度对氡迁移与析出的影响不容忽视。为揭示这类介质表面氡析出的规律,本文基于菲克定律和气液两相界面氡的传输理论,建立了水浸颗粒堆积型射气介质氡的一维传输-扩散数学模型,并获得稳态条件下气液两相体系中氡浓度分布的解析解和氡析出率的计算公式。通过研究,获得以下结论：1）水位为0 m时,颗粒堆积型射气介质表面氡析出率随介质厚度的增大而增大,其增长率随厚度的增大而减小;2）介质表面氡析出率随水位的增大先增大后减小;3）当水体高度大于射气介质厚度时,覆水表面氡析出率随覆水厚度的增大而减小,随覆水氡扩散系数的增大而增大。     

厦门市土壤氡浓度水平及其分布规律调查

为获得厦门市的土壤氡浓度水平及其分布规律,使用FD-3017型RaA测氡仪,于2009年5月4日—5月12日对厦门市土壤氡浓度进行布点测量,对实测的100个数据进行统计分析并绘制土壤氡浓度等值线图。结果表明,厦门市土壤氡浓度范围为450～40 800 Bq/m3,平均值为7 538 Bq/m3;同安区的土壤氡浓度水平较高;不同类型土壤中氡浓度不同,粉质黏土土质和干硬性地表形态测量的土壤氡浓度较高。     

破碎射气介质内氡渗流运移和析出规律的实验研究

渗流是破碎介质内氡运移的主要方式之一,研究氡在破碎射气介质内的渗流运移和析出规律对氡的防护设计具有重要意义。为此,本文以粒径为4～5 mm的铀矿石为实验样品,利用自制的一维渗流实验装置研究了不同渗流速度下破碎射气介质内孔隙氡活度浓度和介质表面氡析出率的变化规律。实验结果表明,破碎射气介质的气体渗透率较大,氡的运移很容易由渗流主导。当破碎射气介质内氡主要以渗流方式运移时,可通过测量介质内同一位置不同渗流速度的孔隙氡活度浓度或同一渗流速度不同位置的孔隙氡活度浓度,运用氡在射气介质中的浓度分布解析式和非线性最小二乘法,估算出介质的可运移氡产生率。一定渗流速度范围内,同一高度的氡活度浓度随渗流速度的增大呈负指数减小,同一渗流速度的氡活度浓度随离介质渗流入口距离的增大近似呈线性增大。介质渗流出口表面氡析出率随渗流速度的增大呈指数增大,最终趋于稳定。     

Effect of spring water on the radon concentration in the air at Masutomi spa in Yamanashi Prefecture,Japan

The concentrations of ²²²Rn existing in air have been studied by using a convenient and highly sensitive Pico-rad detector system at Masutomi spa in Yamanashi Prefecture, Japan. The measurements in air were carried out indoors and outdoors during the winter of 2000 and the summers of 1999 and 2005. The concentrations of ²²²Rn in spring water in this region were measured by the liquid scintillation method. The concentrations of natural radionuclides contained in soils surrounding spa areas were also examined by means of the γ-ray energy spectrometry technique using a Ge diode detector to investigate the correlation between the radionuclides contents and ²²²Rn concentrations in air at each point of interest. The atmospheric ²²²Rn concentrations in these areas were high, ranging from 5 Bq/m³ to 2676 Bq/m³. The radon concentration at each hotel was high in the order of the bath room, the dressing room, the lobby, and the outdoor area near the hotel, with averages and standard deviations of the concentration of 441 ± 79 Bq/m³, 351 ± 283 Bq/m³, 121 ± 5 Bq/m³, and 23 ± 1 Bq/m³, respectively. The source of ²²²Rn in the air in the bath room is more likely to be the spring water than the soil. The spring water plays carries the radon to the atmosphere. Our measurements indicated that the ²²²Rn concentration in the air was affected by the ²²²Rn concentration in spring water rather than that in soil.     

不同土壤氡分布的数值模拟

通过考虑砂土等6种均匀土壤及典型层状土壤的情况,对土壤氡分布进行数值模拟,对扩散系数、孔隙度、降水等对土壤氡分布有影响的因素进行研究,并对因土壤中镭分布而致氡异常分布进行相应分析。分析发现,土壤中的氡浓度随土壤深度的增加而增大。     

花岗岩氡析出影响因素研究进展北大核心CSCD

随着对氡气危害认识的加深,花岗岩作为生产、生活上接触较多的天然辐射来源,其氡析出特征对人居环境的辐射影响得到广泛关注。本文从岩石的原生特性和次生变化两方面对花岗岩的氡析出进行文献综述,发现花岗岩氡析出与岩石化学成分、矿物成分和成因类型等原生特性以及次生风化和蚀变导致的放射性核素分布、矿物颗粒大小以及岩石微裂隙等因素密切相关。研究表明,铀镭活度与花岗岩氡析出表现出线性相关,但受铀赋存矿物类型的影响,矿物成分的具体影响还需进一步研究,可能与其构造背景或者物质来源有关。岩石次生变化对花岗岩氡析出的影响主要表现为风化和蚀变使得放射性核素迁移到颗粒表面和岩石裂隙等有利于氡析出的位置,而颗粒变小比表面积增大以及岩石内表面积和孔隙率增加使得铀镭发生富集和逃逸,从而最终促进岩石氡的析出。岩石原生特性和次生变化对花岗岩的氡析出起着重要的影响作用,铀镭活度可以作为花岗岩氡析出率潜力的预测指标,而对于矿物成分和岩石的次生变化则是研究花岗岩氡析出的重要潜在因素。故此,未来需要系统研究并定量描述岩石化学、矿物成分和次生变化,并据此建立合理有效的岩石氡析出模型,帮助更全面地掌握岩石中氡析出规律,为地下工程及人居环境的氡防护提供理论依据。     

便携式氡析出率自动测量仪研究

氡析出率的可靠测量是环境氡污染治理中的关键因素。活性炭吸附法和静电收集法是氡析出率测量的常用方法,活性炭吸附法适合于在温湿度相对稳定且氡析出率变化不太大的条件下使用,静电收集法能实现快速测量,但目前静电收集式测氡仪如RAD7需对测量的氡浓度进行数据修正才能得到氡析出率。为实现氡析出率的可靠测量,南华大学基于累积集氡和静电收集法测氡的方式研制了一种便携式氡析出率自动测量仪,该测量仪无需干燥管干燥取样的气体,减少了干燥剂对集氡罩内介质表面氡析出率的影响。在自然环境下,该测量仪能准确测量氡浓度,无需借助计算机进行线性拟合处理数据,由内置微处理器将线性拟合转化为代数运算后便能根据测量的氡浓度自动计算出氡析出率。实验表明,该氡析出率自动测量仪在氡析出率标准装置上的测量值与参考值的相对偏差在5%以内。测量完毕直接得出氡析出率,方便了现场氡析出率测量的需求。     

车江铜矿室外氡水平研究

原环保部2014年对湖南衡阳272尾矿库及周边进行了航测,意外发现在尾矿库西南方向、湘江上游附近有一辐射水平异常区域,后经调查该地区为车江铜矿地区。为了调查车江铜矿这一非铀矿山及其周边的氡活度浓度水平与氡的来源,采用了固体核径迹法与活性炭盒法对其氡活度浓度和氡析出率展开测量,并将氡析出率连续测量与活性炭盒法所测氡析出率结果进行对比分析。调查发现,该区域所有取样点位冬季和夏季氡活度浓度测量结果平均值分别为31.0 Bq·m^-3和22.9 Bq·m^-3;从区域分布上来看最高的均为农田区,其次为原采矿区。土壤氡析出率测量结果最高的同样为农田区,但是均远低于铀尾矿的氡析出率限值0.74 Bq·m^-2·s^-1。氡活度浓度日变化趋势与氡析出率的日变化趋势较为一致。上述结果表明车江铜矿地区的室外氡活度浓度较高与其土壤氡的析出有关。     

全国室内氡-土壤氡关联性研究课题启动

介绍了“全国部分城市室内氡．土壤氡关联性研究”课题的主要内容和相关技术要求。工作内容包括：室内氡浓度、土壤氡浓度、城市区域性土壤氡浓度调查；技术要求包括：室内氡调查布点要求、室内氡浓度连续测量要求、土壤氡测量方法、以及测量数据的处理。     

Radon Emanation Dependence on Grain Configuration

Very small pores called ‘nanopores’ play an important role in enhancement of radon emanation in grains. The concept of nanopores was originally proposed by Rama and Moore. The present paper has evolved this concept into more specific grain configurations to estimate radon emanation coefficients by theoretical calculations. These configurations cover combinations of nanopore geometry and radium distribution in grains. Radium is the parent nuclide of radon. Assuming isotropic emission of radon from its birthplace with recoil energy imparted by the decay of radium, the present calculation led to nearly the same high radon emanation coefficients as measured; these were as high as 0.18 under moist conditions. Therefore, it was theoretically verified that even small pores of nanometer size may contribute to high radon emanation.     

全国室内氡-土壤氡关联性研究课题启动

介绍了“全国部分城市室内氡-土壤氡关联性研究”课题的主要内容和相关技术要求。工作内容包括：室内氡浓度、土壤氡浓度、城市区域性土壤氡浓度调查；技术要求包括：室内氡调查布点要求、室内氡浓度连续测量要求、土壤氡测量方法、以及测量数据的处理。     

堆浸铀矿堆氡析出规律的实验研究

堆浸铀矿堆是铀矿山大气氡的主要来源之一。为了揭示堆浸过程中矿堆表面的氡析出规律,以我国南方某铀矿山新上堆的矿石为实验对象,利用自主设计并制造的改进型一维堆浸实验装置,采用局部静态法测定了不同喷淋状态下和排水过程中矿堆表面的氡析出率。结果表明:在布液和改变喷淋强度的瞬间,矿堆表面的氡析出率突然增大,之后随着喷淋的进行而逐渐减小并趋于稳定,且喷淋强度越大,稳定期间的氡析出率反而越小;在排水过程中,氡析出率先迅速减小,而后逐渐增大趋于稳定。