Multivariate statistical analysis of radiological data of building materials used in Tiruvannamalai,Tamilnadu, India

Using γ spectrometry, the concentration of the naturally occurring radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K has been measured in soil, sand, cement, clay and bricks, which are used as building materials in Tiruvannamalai, Tamilnadu, India. The radium equivalent activity (Ra_eq), the criterion formula (CF), indoor gamma absorbed dose rate (D_R), annual effective dose (H_R), activity utilization index (AUI), alpha index (I_α), gamma index (I_γ), external radiation hazard index (H_ex), internal radiation hazard index (H_in), representative level index (RLI), excess lifetime cancer risk (ELCR) and annual gonadal dose equivalent (AGDE) associated with the natural radionuclides are calculated to assess the radiation hazard of the natural radioactivity in the building materials. From the analysis, it is found that these materials used for the construction of dwellings are safe for the inhabitants.The radiological data were processed using multivariate statistical methods to determine the similarities and correlation among the various samples. The frequency distributions for all radionuclides were analyzed. The data set consisted of 15 measured variables. The Pearson correlation coefficient reveals that the ²²⁶Ra distribution in building materials is controlled by the variation of the ⁴⁰K concentration. Principal component analysis (PCA) yields a two-component representation of the acquired data from the building materials in Tiruvannamalai, wherein 94.9% of the total variance is explained. The resulting dendrogram of hierarchical cluster analysis (HCA) classified the 30 building materials into four major groups using 15 variables.     

拉萨市天然石材放射性水平调查

目的 对拉萨市天然石材进行放射性水平调查研究,了解其放射性核素比活度范围及使用限制。方法 对拉萨市各天然石材矿区进行辐射监测和调查取样,对采集的样品进行放射性核素含量分析,根据分析结果计算内、外照射指数,并根据建筑材料放射性核素限量标准进行分类。结果 拉萨市天然石材样品中⁴⁰K、²²⁶Ra、²³²Th和²³⁸U比活度均值分别为912、59.0、77.1和64.4 Bq/kg,样品内、外照射指数均<1。结论 本次调查的拉萨市产天然石材放射性核素含量水平总体低于全国平均水平,可作为建筑主体材料及A类装饰装修材料。     

Effect of lower grain sized particles on natural radiation level of the Ponnaiyar river sediments

River sediment depositions on the bottom of rivers most frequently consist of sand and gravel particles with different grain sizes, which make them particularly valuable for the building construction. Knowledge of radioactivity present in building material enables one to assess any possible radiological hazard to mankind by the use of such materials. The natural radionuclide (²³⁸U, ²³²Th and ⁴⁰K) contents have been analyzed for the sediment samples of Ponnaiyar River with an aim of evaluating the radiation hazard nature. To know the radiological characteristics of the sediment, dose rate is calculated and are compared with recommended values. Mineral characteristics of the sediments have been analyzed through FTIR and XRD techniques. Extinction coefficient and Crystallinity index is calculated to know the relative distribution of major minerals and crystalline nature of quartz, respectively. Multivariate statistical analyses were carried to find the relationship between the radioactivity characteristics and minerals, the results obtained in the study suggest that the level of natural radioactivity of the present sediments mainly depends upon the amount of kaolinite (clay). Mineral characterization of various grain sized sediments show clay and magnetic minerals are rich in lower grain sized (≤120 μm) samples. The level of radioactivity has also been measured for >120 μm sediments and results show that both activity concentrations and dose rate are considerably lowered when compared with the respective values of the bulk samples. The removal of ≤120 μm particles from the sediments of the river make it safer to use these materials for building construction.     

Uptake of radioactivity by marine surface sediments collected in Ghazaouet, west coast of Algeria

Samples of surface marine sediments of different grain sizes collected in Ghazaouet, a small bay on the western coast of Algeria, have been examined to measure concentrations of natural and artificial gamma-emitting radionuclides. The aim of this study is to determine the level of radioactivity and its repartition in the sedimentary area. The samples analyzed by direct counting gamma spectrometry, showed relatively high activities for natural radioactivity and revealed measurable quantities of ¹³⁷Cs, ranging from 0.66–8.47 Bq kg⁻¹ dry weight. In addition, some of the samples of different nature were sieved in different grain-sizes, to study the uptake of radioactivity. It is found that the sediments of less than 100 μm grain-size have the highest level of uptake of radioactivity.     

Natural radioactivity in different types of bricks fabricated and used in the Cairo region

The specific radioactivity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K were measured in samples of different types of bricks (clay, cement, and sand) fabricated and used in urban buildings in the Cairo region in Egypt, using a γ-ray spectrometer with a HpGe-detector. The radiation hazard of the total natural radioactivity in the studied brick was estimated by different approaches. The concentrations of the natural radionuclides and the radium-equivalent activity in the studied Egyptian brick samples are compared with the corresponding results for bricks of the different countries and are found to be significantly lower in all cases.     

Assessment of natural radioactivity levels and radiation hazards due to cement industry

The cement industry is considered as one of the basic industries that plays an important role in the national economy of developing countries. Activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in Assiut cement and other local cement types from different Egyptian factories has been measured by using γ-ray spectrometry. From the measured γ-ray spectra, specific activities were determined. The measured activity concentrations for these natural radionuclides were compared with the reported data for other countries. The average values obtained for ²²⁶Ra, ²³²Th and ⁴⁰K activity concentration in different types of cement are lower than the corresponding global values reported in UNSCEAR publications. The obtained results show that the averages of radiation hazard parameters for Assiut cement factory are lower than the acceptable level of 370 Bq kg^?1 for radium equivalent Ra_eq, 1 for level index Iγr, the external hazard index Hex ≤1 and 59 (nGy h^?1) for absorbed dose rate. The manufacturing operation reduces the radiation hazard parameters. Cement does not pose a significant radiological hazard when used for construction of buildings.     

Gamma spectrometric measurements of depth-related radionuclide distribution in walls

The method for depth-related radionuclide distribution was evolved for approximate determination of the spatial lay-out of radionuclides in materials. The method is based on different attenuation coefficients for various energies of gamma radiation. For each material, the attenuation coefficient decreases with rising energy of radiation. It is therefore possible to assess the location of radionuclides in a material owing to attenuation on the track which a photon has to pass through the material. In this case, gamma lines with energies 609 and 1764 keV produced by nuclide ²¹⁴Bi were used for depth-related radionuclide distribution. This application should be suitable for locating radionuclides in the walls of buildings where high dose rates from gamma radiation occur. These doses are caused by natural radionuclides, mainly radium daughters. The presence of radionuclides in houses poses a high risk associated with inhalation of radon and its decay products. For suitable remediation, it is necessary to know the radionuclide depth distribution.     

Study on the environmental behavior of chernobyl-derived radionuclides in Kyushu Island,Japan

The environmental behavior of Chernobyl-derived radionuclides in Kyushu Island was investigated for one month after the accident. The radioactivity level in airborne dusts was two orders of magnitude lower than that observed in Western Europe. The distribution of ¹³¹I in airborne dusts shifted to a larger particle size compared with other radionuclides. The radionuclide concentration in seaweeds varied depending on the geographical situation where the sampling was done. The biological half-lives in red algae were calculated to be 17.4 d and 32.9 d for ¹³¹I and ¹⁰³Ru, respectively. The concentration factors in red algae were estimated to be 3 × 10³ and 5 × 10³ for ¹³¹I and ¹⁰³Ru, respectively. The cooking effect of ¹³¹I in seaweeds and the committed effective dose equivalent through ingestion of seaweed were also evaluated.     

Natural radioactivity of Indian building materials and by-products.

Conventional building materials and by-products from coal power plants which are being used or have the potential for use in buildings in India were analysed for natural radioactivity due to the presence of 226Ra, 232Th and 40K using gamma-ray spectroscopy. The materials examined in this work showed the radioactivity levels below the limit estimated from radium equivalent activity the criterion formula for gamma-activity suggested for acceptable radiation doses attributable to building materials in OECD countries.     

Natural and anthropogenic radionuclides in rocks and beach sands from Ezine region (Canakkale), Western Anatolia, Turkey.

This paper represents the first reports on the natural and anthropogenic radionuclides in Kestanbol granitic pluton and surrounding rocks, and coastal region of the Ezine town. To assess the radiological hazard of the natural radioactivity, the radium equivalent activity, the absorbed dose rate and the external hazard index were calculated, and in situ gamma dose rates were measured. The high-activity concentrations were measured in the pluton and sands, which was originated mainly from the pluton, due to the presence of zircon, allanite, monazite, thorite, uranothorite and apatite. The average activity concentrations of (238)U, (232)Th and (40)K are 174.78, 204.69 and 1171.95 Bq kg(-1) for pluton, and 290.36, 532.04 and 1160.75 Bq kg(-1) for sands, respectively. (137)Cs in Ezine region ranged from 0-6.57 Bq kg(-1). The average absorbed dose rate for the granitic and sand samples were calculated to be 251.6 and 527.92 nGy h(-1), respectively. The maximum contribution to the total absorbed gamma dose rate in air was due to the (232)Th (52.3% for pluton and 67.1% for sands). The Raeq activities of the pluton and sands are higher than the recommended maximum value of 370 Bq kg(-1) criterion limit of Raeq activity for building materials.     

Natural radioactivity measurement in pumice samples used raw materials in Turkey.

The activity concentrations of 232Th, 226Ra, and 40K in different pumice samples have been determined by high-resolution gamma-ray spectrometry using a 110% HpGe detector. The radium equivalent activities (Raeq), external hazard index (Hex), and internal hazard index (Hin) associated with the natural radionuclides and representative level index (Igamma r) are calculated to assess the radiation hazard of the natural radioactivity in the pumice samples. The mean values of the measured radioactivity concentrations of 232Th, 226Ra, and 40K for pumice samples from the region of lakes (ROL) are 232.4+/-8.0, 196.9+/-7.8, and 1325.8+/-20.4 Bqkg(-1) and for pumice samples from Cukurova region (CR) 16.3+/-4.0, 16.1+/-4.9, and 479.7+/-170.4 Bqkg(-1), respectively. The calculated Raeq values vary from 435.9+/-12.5 to 883.6+/-41.5 Bqkg(-1) with a mean of 630.9+/-20.2 Bqkg(-1) for the ROL samples and from 49.7+/-3.3 to 101.9+/-7.2 Bqkg(-1) with a mean of 76.3+/-23.7 Bqkg(-1) for the CR samples. For the ROL samples, Raeq are above the limit of 370 Bqkg(-1), equivalent to external gamma dose of 1.5 mSv yr(-1), recommended for the safe use of construction materials by NEA-OECD, while for the CR samples, Raeq values are lower than the limit.     

建筑材料样品中放射性核素γ能谱测量比对

目的 通过全国省级疾病预防控制中心γ能谱实验室对建筑材料中放射性核素的测量比对,检验其测量结果的精确度和准确度,提高其对放射性核素的分析水平。方法 依据IAEA 2002年放射性核素国际比对方法,于2007年组织了15个单位对我国建筑材料样品中放射性核素γ能谱测量比对。结果 各参加比对单位提供的测量值与参考值符和较好,其中有50%的参加单位相对偏差小于5%,相对偏差小于10%的单位超过80%。结论 γ能谱分析建筑材料样品中放射性核素含量的方法是准确可靠的,可以满足GB 6566-2001《建筑材料放射性核素限量》标准的要求。     

Standardization requirements for the in vivo counting techniques of gamma - and soft X-ray radionuclides

The techniques for the in vivo counting of the internal body burden of radionuclides for radiation protection purposes can be divided into two broad categories according to the energy of the measured radiation: (a) measurement of internal contamination due to radionuclides emitting gamma-rays with energies above 100 keV; (b) measurement of internal contamination due to radionuclides emitting soft gamma-or X-rays with energies below 100 keV. The subdivision into two categories is mainly dictated by the many different problems encountered in counting low levels of X-ray emitting radionuclides (such as plutonium isotopes) in man. A mandatory requirement to obtain a reasonable sensitivity of the counting systems for both categories requires a sensible reduction of the normal background due to cosmic rays and to the natural radioactivity present in the human environment (soil, building materials, air, etc).     

Crosstalk correction in radioluminography

Crosstalk often causes large measurement errors in the radioluminography of energetic radionuclides. We proposed here a new technique to overcome this problem. With the aid of computerized data processing, it is possible to analytically correct the interference radiation. The resulting accurate determination of activity makes it possible to measure numerous samples simultaneously using an imaging plate. This technique has been applied to ³²P samples in the wells of an assay-plate and is found to be highly practical.     

Transfer of 238U, 230Th, 226Ra,and 210Pb from soils to tree and shrub species in a Mediterranean area

The soil-to-plant transfer factors of natural uranium isotopes (²³⁸U and ²³⁴U), ²³⁰Th, ²²⁶Ra, and ²¹⁰Pb were studied in a disused uranium mine located in the Extremadura region in the south-west of Spain. The plant samples included trees (Quercus ilex, Quercus suber, and Eucalyptus cameldulensis) and one shrub (Cytisus multiflorus). All of them are characteristic of Mediterranean environments. The activity concentrations in leaves and fruit were determined for the tree species at different stages of growth. For the shrub, the total above-ground fraction was considered in three seasons. For old leaves and fruit, the highest activity concentrations were found in Eucalyptus cameldulensis for all the radionuclides studied, except in the case of ²³⁰Th that presented similar activity concentrations in all of the tree species studied. In every case, the transfer to fruit was less than the transfer to leaves. In the shrub, the results depended on the season of sampling, with the highest value obtained in spring and the lowest in autumn. Important correlations were obtained for ²³⁸U and ²²⁶Ra between the activity ratio in soils with that in leaves or fruit.     

秦山核电站运行对上海环境放射性影响评价

目的 了解秦山核电站运行17年后是否对上海地区环境和居民健康产生影响。 方法通过现场监测和采样分析方法对上海金山地区室外环境与饮用水、食品、土壤等环境介质中的放射性水平进行监测。 结果 室外天然辐射水平与环境介质中的放射性水平属正常本底范围,核电站运行前后金山地区环境放射性水平无明显变化,环境介质中的放射性水平低于国家标准限制浓度;居民受室外天然辐射外照射所致剂量为0.102 mSv,经由膳食摄入人工放射性核素Sr和Cs所致居民内照射剂量为0.488 μSv。 结论 秦山核电站运行17年所释放的放射性物质未对上海地区环境放射性水平和居民健康产生影响。     

食品中放射性水平测量技术及标准现况调查与分析

自上个世纪六十年代起,我国已开展对粮食和水源的放射性监测工作。至今,由于2次重大核电站事故,尤其是2011年日本福岛核事故中产生的放射性核素在海洋、大气和陆地上扩散并在食物链中积聚,放射性核素对人类健康的危害程度急需量化评估,因此,食品中放射性水平的测量至关重要。笔者概述了食品中放射性核素的常用测量方法,并对福岛核事故中造成公众健康危害的主要核素的具体测量技术和依据标准进行了分析,旨在为进一步完善测量食品中放射性核素的技术和标准提供理论支撑,为核辐射的应急管理和恢复策略提供数据支持,最终实现为公众的健康提供切实的保障。     

Radiological impact assessment to the environment due to waste from disposal of porcelain

The present study aimed to assess the radiological parameters from gamma rays due to the uncontrolled disposal of porcelain waste to the environment. Qualitative and quantitative identification of radionuclides in the investigated samples was carried out by means of a high-purity germanium (HPGe) detector. The average activity concentrations of the local porcelain samples were measured as 208.28?Bq/kg for ²²⁶Ra, 125.73?Bq/kg for ²³⁸U, 84.94?Bq/kg for ²³²Th and 1033.61?Bq/kg for ⁴⁰K, respectively. The imported samples had an average activity of 240.57?Bq/kg for ²²⁶Ra, 135.56?Bq/kg for ²³⁸U, 115.74?Bq/kg for ²³²Th and 1312.49?Bq/kg for ⁴⁰K, respectively. Radiological parameters and the radium equivalent Ra_eq for the investigated samples were calculated. The external and internal hazard indices, representative level index (I_γ), alpha index (I_α), and the exemption level (I_x), were estimated to be higher than the recommended value (unity), while the average activity concentrations for the studied samples were higher than recommended levels. In conclusion, we are concerned that disposal of porcelain in the environment might be a significant hazard.     

Evaluation of natural radionuclides at Um-Greifat area, eastern desert of Egypt.

Air borne radiometric maps and remote sensing techniques were used to explore for the occurrence of radioactive materials. The previous techniques recorded radioactive mineralization for the first time along the NW-SE trending fault zones within the Miocene clastic-carbonate sediments. In the present study, gamma-ray spectrometry was used to confirm the presence of this mineralization.Concentrations of radionuclides, associated within the iron ochre at Um-Greifat area, have been measured, using a hyper-pure germanium spectrometer. The variation in concentration of radionuclides for the area under investigation can be classified into A, B and C regions of high, medium and low natural radioactivity. In region A, average concentration in Bqkg(-1) has been observed to range from 1858 to 4062 for 238U, between 29 and 151 for 232Th, from 60 to 136 for 235U and between 46 and 409 Bqkg(-1) for 40K. Radium equivalent activities (Ra(eq)) in addition to external and internal hazard indices (H(ex), H(in)) have also been determined. Ra(eq) varies between 1901 and 4307Bqkg(-1), which exceeds the permitted value (370Bqkg(-1)) and H(ex) and H(in) are higher than 1. The high activity concentration within region A points to an environmental hazard, while regions B and C have less exposure effect on human beings.