Neutron Activation Techniques in Environmental Studies

The development over time in applications of nuclear activation techniques in environmental studies is critically reviewed. A vast majority of the work has been based on activation analysis using thermal and sometimes epithermal neutrons from nuclear reactors (NAA). Whereas radiochemical methods were frequently used until about 1975, the work reported more recently has mainly been multi-element studies based on instrumental NAA. The by far most successful application has been the analysis of aerosol samples, but considerable work has also been done in other areas such as precipitation and surface waters, soils, vascular plants, moss and lichen biomonitors, and fossil fuels with by-products. Some interesting examples of speciation analysis, based on pre-irradiation separations, have also been reported. Rapid development in alternative multi-element techniques such as ICP-MS has shown these techniques to be superior in a number of cases where NAA earlier was the technique of choice. Areas where efforts should be concentrated in future NAA work are indicated.     

Multielement Analysis of Iliac Crest Bone by Neutron Activation

The k ₁-method for standardization in INAA specifically tackles the problem of the interpretation of gamma-ray spectra as obtained with highly efficient detectors, as opposed to the k ₀-method. In this paper, results obtained from three NIST reference materials, measured after neutron activation with a gold-lined well-type detector, are presented. It is concluded that the accuracy of the method is better than 1%.     

中子活化分析测定牛奶中的有机卤族化合物

1　引　　言由于有机卤族化合物污染的普遍性和突出的“三致”作用 (致癌、致突变、致畸形 ) ,有机卤族化合物的环境行为一直是环境化学的研究热点 ,也是世界各国重点控制的污染物。有机卤族化合物的分析测定一直由色谱完成 ,但由于该类化合物有成千上万种 ,色谱分析不可能对样品中的所有有机卤族化合物进行定性和定量分析。有研究表明 :色谱分析结果只占实际污染水平的 1%～ 2 6% ,并不能准确反映有机卤族化合物的总体污染水平。中子活化分析 (ＮＡＡ)是目前唯一一种能同时定量测定有机Ｃｌ、Ｂｒ和Ｉ的方法。本工作用中子活化分析测定了牛…     

14 MeV Fast Neutron Activation Analysis in the Year 2000

In recent years there is a decided upswing in interest in the application of fast neutron activation analysis methodologies to certain problems, i.e., detection of contraband substances, use of steady-state and pulsing instruments of body compositions etc. The value of a method which can characterize major and minor elements in large samples is again recognized.     

石英流体包裹体中液相成分的中子活化分析

研究了应用中子活化分析技术分析石英流休包裹体液相成分中痕量元素的方法，并在超净实验室内完成了样品的清洗，爆裂及提取，蒸干等前处理过程，所建立的方法仅取１５ｇ粒径为０．４～０．８ｍｍ的石英样品，以３％硝酸浸泡清洗后，由真空热爆法打开包裹体，以１％硝酸浸取其液相在分，并且将样品独立地分为两份，分别以１．２×１０＾１３ｎ／ｓ．ｃｍ＾２和３．７×１０＾１３ｎ／ｓ．ｃｍ＾２的中子注量率辐照样品５ｍｉｎ和２４     

Neutron Activation Analysis in the IAEA Projects on Air Pollution

The International Atomic Energy Agency (IAEA) has been promoting studies on air pollution since 1992. During the period 1992–1999 there have been six major co-ordinated research and regional technical co-operation projects in which 77 counterparts from 40 Member States actively participated. The studies supported by the IAEA have included ambient and workplace airborne particulate matter, the use of appropriate plant biomonitors and a series of laboratory intercomparison exercises in support to these projects. Recent and current IAEA projects in this field are reviewed in the light of the application of neutron activation analysis, which has been used as a major analytical technique by more than two thirds of the counterparts, and contributed also approximately two thirds of all analytical results for the intercomparison exercises.     

Evaluation of New Pharmaceuticals Using In Vivo Neutron Inelastic Scattering and Neutron Activation Analysis

Nutritional status of patients can be evaluated by monitoring changes in body composition, including depletion of protein and muscle, adipose tissue distribution and changes in hydration status, bone or cell mass. Fast neutron activation (for N and P) and neutron inelastic scattering (for C and O) are used to assess in vivo elements characteristic of specific body compartments. The fast neutrons are produced with a sealed deuterium-tritium (D-T) neutron generator. This method provides the most direct assessment of body composition. Non-bone phosphorus for muscle is measured by the ³¹P(n,)²⁸Al reaction, and nitrogen for protein via the (n,2n) fast neutron reaction. Inelastic neutron scattering is used for the measurement of total body carbon and oxygen. Carbon is used to derive body fat, after subtracting carbon contributions due to protein, bone and glycogen. Carbon-to-oxygen (C/O) ratio is used to measure distribution of fat and lean tissue in the body and to monitor small changes of lean mass and its quality. In addition to evaluating the efficacy of new treatments, the system is used to study the mechanisms of lean tissue depletion with aging and to investigate methods for preserving function and quality of life in the elderly.     

A PC-Program for the Calculation of Neutron Flux and Element Contents Using the ki-Method of Neutron Activation Analysis

A computer program is described, which calculates the induced activities of isotopes after irradiation in a known neutron field, thermal and epithermal neutron fluxes from the measured induced activities and from nuclear data of 2–4 monitor nuclides as well as the element concentrations in samples irradiated together with the monitors. The program was developed for operation in Windows 3.1 (or higher). The application of the program for neutron activation analysis allows to simplify the experimental procedure and to reduce the time. The program was tested by measuring different types of standard reference materials at the FRJ-2 (Research Centre, Jülich, Germany) and Triga (University Mainz, Germany) reactors. Comparison of neutron flux parameters calculated by this program with those calculated by a VAX program developed at the Research Centre, Jülich was done. The results of testing seem to be satisfactory.     

Neutron Activation Analysis of Bottom and Fly Oil Ash Leachates

Seven samples of oil fly and bottom ashes were leached with water using a Canadian standard test method for shake extraction of solid waste. The concentrations of 20 elements in the leachates were determined by the computerized systematic instrumental absolute neutron activation analysis. The ranges of concentrations (in ppm) found for the elements in the leachates were: Al (3–526), Ba (0.5–6), Ca (100–695), Cl (13–59), Co (1–6.3), Cr (0.2–6.6), Cs (0.03–0.4), Eu (0.003–0.01), Fe (28–690), K (42–464), La (0.3–49), Mg (214–3150), Mn (1.2–20), Na (88–4050), Sb (0.04–0.4), Sc (0.003–0.07), Sr (1.2–23), U (0.07–1), V (1.2–4540) and Zn (2.3–200). These findings were compared with the maximum concentrations allowed for these elements by Canadian regulations. The concentrations of Cr and U were found to be higher than their permissible limits on 7 occasions. The purpose of this study was to determine the background levels of different elements in oil ash leachates, in order to evaluate their potential impact on underground water.     

Radiochemical Neutron Activation Analysis of Rhenium and Ammonium Perrhenate Samples

A procedure for the radiochemical neutron activation analysis of rhenium and ammonium perrhenate samples was developed. The procedure provides the determination of about 30 impurity elements present in concentrations of n× 10^–4to n× 10^–8mass % with RSD of 20–30%. An AV-17 anion exchanger–nitric acid solution system was used, which allows the selective separation of rhenium from a wide variety of elements.     

Determination of Trace Elements in Tea and Coffee by Neutron Activation Analysis

Thermal neutron activation analysis, a high-resolution Ge(Li) gamma-ray spectrometer, and an IBM 360/67 digital computer were used to determine the concentration of Na, K, Sc, Cr, Mn, Fe, Co, Cu, Zn, Se, Br, Rb, Sb, Cs, and Hg in ground coffee and tea. This nondestructive multielement technique requires neither pre- nor postirradiation chemistry and eliminates problems of reagent contamination. The method is simple, precise and sensitive to 15 elements. Interferences from fast neutron (n, p) and (n, α) reactions are small and, if necessary, corrections may be applied easily. This technique can be applied to percolated tea and coffee.     

Overcoming Matrix Effects in the 14 MeV Fast Neutron Activation Analysis of Metals

Fast neutron activation analysis (FNAA) has proven to be a useful technique for the estimation of non-metallic inclusions in metals, and is currently being used in industry, especially for the determination of oxygen in magnesium alloys. However, high levels of radioactivity induced in large metallic samples by irradiation in a neutron field give rise to matrix interferences which are significant at low oxygen concentrations. These interferences are due to coincidental summations that fall into the energy window used for quantitation of oxygen. This report explains technical details of newly developed experimental procedures and alterations of existing software which correct for the errors, thereby enhancing the potential for use of the method.     

A Comparison of Thermal and Epitherral Neutron Activation for the Measurement of Selenium in Vegetation

Abstract

Selenium concentrations in vegetation measured by two methods of activation analysis are compared. Detection limits of 1 ppm and 20 ppb have been achieved from epithermal and thermal neutron activation, respectively.     

用中子活化分析法研究25种元素在人体肝脏亚细胞组分中的分布

采用差速离心分离技术与中子活化分析法（ＮＡＡ）相结合的方法分析了人肝２５５中元素,并用标准参考物保证结果的准确性。分析结果表明,大多数元素在各亚细胞组分中并非均匀分布。Ａｓ、Ａｕ、Ｃｏ、Ｉ、Ｍｇ、Ｓｂ、Ｓｅ在细胞核和线粒体浓度最高。Ａｌ、Ｓｓ、Ａｕ、Ｂａ、Ｆｅ、Ｉ、Ｍｇ、Ｍｏ、Ｓｂ、Ｓｃ在细胞核和线粒体浓度最高。Ａｌ、Ａｓ、Ａｕ、Ｂａ、Ｆｅ、Ｉ、Ｌａ、Ｍｇ、Ｍｎ、Ｓｂ、Ｓｅ在胞液中深度最低,生物体     

Instrumental Neutron Activation Analysis for Certification of Ion-Implanted Arsenic in Silicon

Standard reference material (SRM) 2134 Arsenic Implant in Silicon was produced at the National Institute of Standards and Technology (NIST) as a calibrant for secondary ion mass spectrometry. Instrumental neutron activation analysis was used as a primary method for certification of the arsenic implanted dose. A complete evaluation of all sources of uncertainty yielded an expanded relative uncertainty for the mean value of this SRM to be 0.38% at approximately the 95% level of confidence. No evidence indicating significant heterogeneity among samples was observed.     

The determination of molybdenum in geological samples by Neutron Activation Analysis

A metal-silicate extraction technique combined with neutron activation analysis has been developed to determine molybdenum in geological samples. The samples are equilibrated with Femetal powder at high temperatures. Molybdenum is completely extracted into the metal phase because of very reducing conditions in the furnace. The metal spherule is separated from the silicates, irradiated and dissolved in an acid solution. The molybdenum is precipitated as a sulfide and the precipitate is dissolved in aqua regia and counted on a Ge/Li/detector. The radiochemical yield is obtained by irradiation of the solution. The method avoids production of⁹⁹Mo from induced fission of²³⁵U by performing the metal-silicate separation before irradiation. The precipitation step may be necessary to remove the high background from the decay of⁵⁹Fe. Mo concentrations down to 15 ng/g have been obtained using this method.