Measurement of radionuclides and absorbed dose rates in soil samples of Peshawar,Pakistan, using gamma ray spectrometry

The analysis of gamma-emitting radionuclides in nature, i.e. ²²⁶Ra, ²³²Th, ⁴⁰K and ¹³⁷Cs, has been carried out in soil samples collected from Peshawar University Campus and surrounding areas using a high purity germanium detector coupled with a computer-based high-resolution multichannel analyser. The activity concentrations in soil ranged from 30.20±0.65 to 61.90±0.95, 50.10±0.54 to 102.80±1.04, 373.60±4.56 to 1082±11.38 and 9.50±0.11 to 46.60±0.42 Bq kg^?1 for ²²⁶Ra, ²³²Th, ⁴⁰K and ¹³⁷Cs, with a mean value of 45±7.70, 67±12.50, 878±180 and 19±9.20 Bq kg^?1, respectively. The radium equivalent activity, internal and external hazard indices have mean values of 203.40±29.40 Bq kg^?1, 0.56 and 0.68, respectively. The mean values of outdoor and indoor absorbed dose rates in air and the annual effective dose equivalents were found to be 106.50 and 128 nGy h^?1 and 0.19 and 0.54 mSv y^?1, respectively. In the present study, ⁴⁰K was the major radionuclide present in soil samples. The presence of ¹³⁷Cs indicates that this area also received some fallout from the nuclear accident of the Chernobyl power plant in 1986. The activity concentrations of radionuclides found in soil samples during the current investigation were nominal. Therefore, they are not associated with any potential source of health hazard to the public.     

Studies of natural radionuclides and dose estimation from soil samples of Kumaun Himalaya, India

In the present study, the distribution of natural radionuclides in soil samples collected from different geological units of Kumaun Himalayas are assessed using gamma ray spectrometer with Nal(Tl) detector. The naturally occurring radioactivity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K were found to vary from 36.4 Bq/kg to 166.6 Bq/kg, 15.3 Bq/kg to 94.7 Bq/kg and 645.9 Bq/kg to 1378.9 Bq/kg, respectively. The total absorbed gamma dose rate was found to vary from 80 nGy/h to 179.6 nGy/h. The resulting dose due to the presence of these radionuclides was estimated from radiation protection point of view. The significance of this investigation is also discussed in details.     

Comparison of active and passive radon survey in cave atmosphere,and estimation of the radon exposed dose equivalents and gamma absorbed dose rates

Radon (²²²Rn) measurements were conducted in the Pileki Cave with Radim 3A Active Radon Monitor equipment. Measurements were also done with the passive sampling method with CR-39 nuclear track detectors by exposing them for three months in the cave. Radon concentrations obtained from the active and passive sampling methods showed that, firstly, the concentrations inside the cave measured by the latter method differed greatly due to high humidity levels up to 88%. The total inside radon exposure dose equivalent people were subjected to was estimated to be 19?µSv a^?1 for visitors and 24,065?µSv a^?1 for guides. The gamma absorbed dose rates were determined for inside and outside the cave. The dose rates were calculated by means of using the ²²⁶Ra, ²³²Th and ⁴⁰K activity concentrations and by means of real-time measurements. The gamma absorbed dose rates were found to be much higher than the value of 55?nGy?h^?1 given by UNSCEAR. In addition, the mineralogical compositions and elemental analyses of samples taken from the cave were determined by XRD and WD-XRF methods.     

Speciation of radionuclides of the Chernobyl origin in aerosol and soil samples

Speciation of^134,137Cs,⁹⁰Sr,²³⁴U,²³⁸U,²³⁸Pu,^239,240Pu and²⁴¹Am was investigated in aerosol samples collected after the Chernobyl accident and in the Chernobyl soil. Sequential extraction experiments have shown a wide range of association of radionuclides, depending on sources, transformation perculiarities and radionuclide nature. Changes in speciation of¹³⁷Cs and⁹⁰Sr at various temperatures in the Chernobyl soil were analyzed. It was found that at 200°C–700°C a transformation of speciation of¹³⁷Cs took place and more available physico-chemical forms of Cs were formed. After heating at 900°C, up to 94% of¹³⁷Cs was found in the residual form and was not extractable even with 7 M HNO₃. Heating of the soil to 450°C and 900° C resulted in the formation of less available forms of⁹⁰Sr.     

Measurement of uranium and its isotopes at trace levels in environmental samples using mass spectrometry

Actinides have widely entered the environment as a result of nuclear accidents and atmospheric weapon testing. These radionuclides, especially uranium, are outstanding radioactive pollutants, due to their high radiotoxicity and long half-lives. In addition to this, since depleted uranium (DU) has been used in the Balkan conflict in 1999, there has been a concern about the possible consequences of its use for the people and environment. Therefore, accurate, precise and simple determination methods are necessary in order to evaluate the human dose and the concentration and effects of these nuclides in the environment. The principal isotopes of uranium e.g. ²³⁵U and ²³⁸U are of primordial origin and ²³⁴U present in radioactive equilibrium with ²³⁸U. ²³⁶U occurs in nature at ultra trace concentrations with a ²³⁶U: ²³⁸U atom ratio of 10⁻¹⁴. Concentrations of uranium in soil samples were determined using inductively coupled plasma mass spectrometry (ICP-MS) and isotope ratios of uranium were measured using a thermal ionisation mass spectrometer. Radioactive dis-equilibrium of ²³⁴/²³⁸U, depletion of ²³⁵/²³⁸U and significant evidence of ²³⁶U/²³⁸U were noticed in soil samples.      

Microfluidic sample preparation for elemental analysis in liquid samples using micro X‐ray fluorescence spectrometry

The integration of microfluidic devices with micro X‐ray fluorescence (micro‐XRF) spectrometry offers a new approach for the direct characterization of liquid materials. A sample presentation method based on use of small volumes (<5 µl) of liquid contained in an XRF‐compatible device has been developed. In this feasibility study, a prototype chip was constructed, and its suitability for XRF analysis of liquids was evaluated, along with that of a commercially produced microfluidic device. Each of the chips had an analytical chamber which contained approximately 1 µl of sample when the device was filled using a pipette. The performance of the chips was assessed using micro‐XRF and high resolution monochromatic wavelength dispersive X‐ray fluorescence, a method that provides highly selective and sensitive detection of actinides. The intended application of the device developed in this study is for measurement of Pu in spent nuclear fuel. Aqueous solutions and a synthetic spent fuel matrix were used to evaluate the devices. Sr, which has its Kα line energy close to the Pu Lα line at 14.2 keV, was utilized as a surrogate for Pu because of reduced handling risks. Between and within chip repeatability were studied, along with linearity of response and accuracy. The limit of detection for Sr determination in the chip is estimated at 5 ng/µl (ppm). This work demonstrates the applicability of microfluidic sample preparation to liquid characterization by XRF, and provides a basis for further development of this approach for elemental analysis within a range of sample types. Copyright © 2014 John Wiley & Sons, Ltd.     

Direct multielement determination of Cd,Pb, Fe,and Mn in ground coffee samples using energy dispersive X‐ray fluorescence spectrometry

An analytical method was proposed for the quantification of Cd, Pb, Mn, and Fe in ground coffee samples using energy dispersive X‐ray fluorescence (EDXRF) spectrometry. External calibration was possible using the coffee matrix itself as standards with samples previously analyzed by inductively coupled plasma optical emission spectrometry (ICP OES). The ground coffee samples were analyzed in the form of pellets, which were placed in the center of the EDXRF measuring cell for the determination of the analytes. The limits of detection were 62, 55, 86, and 76 μg/kg for Cd, Pb, Fe, and Mn, respectively. Good linearities were obtained for the calibration curves with coefficients of correlation (R) of 0.9959 for Cd, 0.9939 for Pb, 0.9929 for Fe, and 0.9909 for Mn. Precision, evaluated as the relative standard deviation (RSD) of 10 independent measurements of different cataloged samples with an approximate concentration of 400 μg/kg for each analyte, was between 6 and 14% (n = 10), demonstrating that the preparation of the samples in form of pellets was sufficient to perform analyses by EDXRF. The proposed method was applied in the determination of Cd, Pb, Fe, and Mn in ground coffee samples collected in Salvador, Bahia, Brazil. In a parallel comparative procedure, coffee samples were also analyzed by ICP OES after sample pretreatment by acid digestion. A paired Student's t test was carried out (confidence level of 95%, n = 5) and no significant difference was observed between the concentrations obtained by the proposed and comparative methods.     

Sequential extraction procedure for determination of uranium, thorium, radium, lead and polonium radionuclides by alpha spectrometry in environmental samples

A sequential extraction technique was developed and tested for common naturally-occurring radionuclides. This technique allows the extraction and purification of uranium, thorium, radium, lead, and polonium radionuclides from the same sample. Environmental materials such as water, soil, and biological samples can be analyzed for those radionuclides without matrix interferences in the quality of radioelement purification and in the radiochemical yield. The use of isotopic tracers (²³²U, ²²⁹Th, ²²⁴Ra, ²⁰⁹Po, and stable lead carrier) added to the sample in the beginning of the chemical procedure, enables an accurate control of the radiochemical yield for each radioelement. The ion extraction procedure, applied after either complete dissolution of the solid sample with mineral acids or co-precipitation of dissolved radionuclide with MnO₂ for aqueous samples, includes the use of commercially available pre-packed columns from Eichrom® and ion exchange columns packed with Bio-Rad resins, in altogether three chromatography columns. All radioactive elements but one are purified and electroplated on stainless steel discs. Polonium is spontaneously plated on a silver disc. The discs are measured using high resolution silicon surface barrier detectors. ²¹⁰Pb, a beta emitter, can be measured either through the beta emission of ²¹⁰Bi, or stored for a few months and determined by alpha spectrometry through the in-growth of ²¹⁰Po. This sequential extraction chromatography technique was tested and validated with the analysis of certified reference materials from the IAEA. Reproducibility was tested through repeated analysis of the same homogeneous material (water sample).     

Measurement of background components in wavelength dispersive X‐ray fluorescence spectrometry

Three components of the background have been investigated: first, characteristic radiation of the lamellas of the collimator excited by secondary x‐ray beam; second, secondary x‐ray beam scattered by the lamellas of the collimator; third, diffusive and incoherent scattering of the secondary x‐ray beam by the focusing crystal. The relationships between chemical content of the specimen and the intensity of the first and the second components were determined by a wavelength‐dispersive x‐ray spectrometer that has an energy‐dispersive x‐ray detector. The intensity of the third component was very low. It was not found in this experiment. Copyright © 2006 John Wiley & Sons, Ltd.     

Dual-modality and dual-energy gamma ray densitometry of petroleum products using an artificial neural network

The prediction of volume fractions in order to measure the multiphase flow rate is a very important issue and is the key parameter of multi-phase flow meters (MPFMs). Currently, the gamma ray attenuation technique is known as one of the most precise methods for obtaining volume fractions. The gamma ray attenuation technique is based on the mass attenuation coefficient, which is sensitive to density changes; density is sensitive in turn to temperature and pressure fluctuations. Therefore, MPFM efficiency depends strongly on environmental conditions. The conventional solution to this problem is the periodical recalibration of MPFMs, which is a demanding task. In this study, a method based on dual-modality densitometry and artificial intelligence (AI) is presented, which offers the advantage of the measurement of the oil–gas–water volume fractions independent of density changes. For this purpose, several experiments were carried out and used to validate simulated dual modality densitometry results. The reference density point was established at a temperature of 20 °C and pressure of 1 bar. To cover the full range of likely density fluctuations, four additional density sets were defined (at changes of ±4% and ±8% from the reference point). An annular regime with different percentages of oil, gas and water at different densities was simulated. Four features were extracted from the transmission and scattered detectors and were applied to the artificial neural network (ANN) as inputs. The input parameters included the ²⁴¹Am full energy peak, ¹³⁷Cs Compton edge, ¹³⁷Cs full energy peak and total scattered count, and the outputs were the oil and air percentages. A multi-layer perceptron (MLP) neural network was used to predict the volume fraction independent of the oil and water density changes. The obtained results show that the proposed ANN model achieved good agreement with the real data, with an estimated root mean square error (RMSE) of less than 3.     

基于小尺度参考辐射的便携式伽玛射线剂量(率)仪校准方法及应用

针对现有伽玛射线剂量(率)测量仪器检定方法送检距离远、周期长、效率低的不足,中国工程物理研究院核物理与化学研究所采用基于样本仪表的机器预测方法,开展了基于小尺度参考辐射的便携式伽玛剂量(率)仪遂行校准技术研究工作。最终成功地研制了一套辐射防护用伽玛射线剂量(率)仪遂行校准装置,实现了测量标准不确定度不大于5%的良好结果。为伽玛空气比释动能量值的遂行定度提出了一条全新的技术思路,为便携式伽玛剂量(率)仪的现场和野外校准提供了一种全新的示范装备。     

Investigation of gamma ray transitions and lifetimes in35Cl

Fortyeight resonances of the³⁴S(p, γ)³⁵Cl reaction in the proton rangeE _p=1–2 MeV have been observed. Gamma decay of twentyeight of these was investigated by means of a 55 cm³ Ge(Li) detector, and the energies and branching ratios of several bound states have been determined. TheQ-value was found to be 6367.0 ± 1.5 keV. The lifetimes 150±20, 400±140, 19±4, 14±2, 145±50, 20±5, 20±4, 42±4 and 7±3 fs were determined with the DSA method for the states at 1219, 1763, 2694, 3003, 3944, 3967, 4059, 4178 and 4882 keV, respectively. The experimental transition strengths were found to be in agreement with those given by manyparticle shell-modell calculations.     

Decaying source model: Alternative approach to determination of true counting rates at X and gamma ray counting systems

The counting systems consisting of electronic devices are used for detection of radiation due to X or gamma rays. The dead time of the counting system is based on time limitations of these electronic devices. The dead time causes counting losses. Determination of counting rate losses in quantitative and qualitative analysis become a vital step for correction of analysis. Therefore, compensating for counting rate losses is of great importance. These counting rate losses are due to piled up reject time, paralyzable or non-paralyzable system dead time or a combination of these mechanisms. Paralyzable and non-paralyzable models are well-known and frequently used for correction of counting rate losses dependent on the system dead time. However, these two models do not provide enough correction at medium and high counting rates. Therefore, the new models for corrections of counting rate losses are needed. For this reason, both an alternative approach is proposed and a simulation program is coded for counting rate losses in this study. A good agreement is obtained between theoretical model and simulation program.     

Uranium, radium and radon exhalation studies in some soil samples using plastic track detectors

Radium concentration and radon exhalation rate have been measured in soil samples collected from some areas belonging to upper Siwaliks of Kala Amb, Nahan and Morni Hills of Haryana and Himachal Pradesh states, India using LR-115 type II plastic track detectors. Uranium concentration has also been determined in these soil samples using fission track registration technique. Radium concentration has been found to vary from 5.30 to 31.71 Bq.kg⁻¹, whereas uranium concentration varies from 33.21 to 76.26 Bq.kg⁻¹. The radon exhalation rate in these samples varies from 216.87 to 1298.00 mBq.m⁻²hr⁻¹ (6.15 to 36.80 mBq.kg⁻¹.hr⁻¹). Most of the samples have uranium concentration above the worldwide average concentration of 35 Bq.kg⁻¹. A good correlation (R ² = 0.76) has been observed between uranium concentration and radon exhalation rate in soil. The values of uranium, radium and radon exhalation rate in soil are compared with that from the adjoining areas of Punjab.     

Determination of uranium contents in rock samples from Kakul phosphate deposit, Abbotabad (Pakistan), using fission-track technique

Some times high uranium contents are present in the phosphate rocks used for the manufacturing of fertilizer. In view of the harmful effects on human health due to the processing and use of such fertilizers in agriculture, it is important to analyse phosphate rocks for uranium content determination. Ten representative rock samples from Kakul phosphate deposit exposed near Abbotabad, Pakistan which are used for the manufacturing of fertilizers were studied for uranium content determination with the help of fission track and neutron activation analysis techniques. Each sample was split into three parts. The first and second parts (solid slabs and pellets) were subjected to fission track analysis, while the third part was analysed using neutron activation analysis technique for comparison. On the average a uranium content of 37 ppm was found in the phosphate rocks. The results of uranium content determinations with the help of fission track and neutron activation analysis techniques show a remarked resemblance up to ±0.1%. This indicates that the fission track analysis technique of uranium content determination is a reliable method inspite of its simplicity. The uranium content in the Kakul deposits is within the permissible limit allowed for the mining and processing of the phosphate rocks for the manufacturing of fertilizers.     

土壤中铜元素的激光诱导击穿光谱测量分析

利用Nd:YAG脉冲激光器(1064nm)作为光源,以高分辨率、宽光谱段的中阶梯光栅光谱仪和ICCD为谱线分离与探测器件,测量并分析了土壤中铜元素激光诱导击穿光谱特性。以铜的327.396nm特征谱线作为分析线,在同一浓度下,固定探测器门宽,通过调节延迟时间,得到铜元素的衰变特性,确定了铜元素的最佳延迟时间为1.1μs。测定不同铜浓度下的特征谱线强度,表明在低浓度下,谱线强度随浓度的增加而增大。文章给出了铜元素的定标曲线,并计算得到铜元素的检测限为13.36μg·g-1。