铀-2-(3,5-二溴-2-吡啶偶氮)-5-二乙氨基苯酚-Triton X-100析相体系的研究及应用

本文研究了铀-2-(3,5-二溴-2-吡啶偶氨)-5-二乙氨基苯酚(3,5-diBr-PADAP)-Triton X-100析相光度体系,建立了矿石中微量铀的测定方法,在pH 7.5三乙醇胺-盐酸介质中,将胶束溶液在 95±1℃加热 1h.络合物即被Triton X-100相完全富集.络合物最大吸收峰位于565nm.摩尔吸光系数为1.02×10～5L·mol～(-1)·cm～(-1),铀含量在0～12μg/5mL服从比耳定律.采用TBP萃淋树脂分离干扰离子,测定矿石中微量铀,结果满意.     

An extractive pellet fluorimetric determination of trace uranium in thorium rich samples

An extractive pellet fluorimetry determination of trace uranium in thorium rich samples has been developed. This is based upon a solvent extraction system which completely separates both the elements uranium and thorium from each other. Thorium as a neutral complex with 2,3-dihydroxynaphthalene at pH 4–6 is extracted into ethylacetate and then uranium-2,3-dihydroxynaphthalene anionic complex is extracted into another batch of ethylacetate at pH 11–12 under the influence of a counter cation, cetyltrimethylammonium ion. This method has been applied for the determination of trace uranium in synthetic nuclear grade thorium oxide and thorium rich mineralized rock with high degree of accuracy and precision.     

On the Nature of the Cherdyntsev–Chalov Effect

It is shown that the Cherdyntsev–Chalov effect, usually presented as the separation of even isotopes of uranium upon their transition from the solid to the liquid phase, can include initiated acceleration of the radioactive decay of uranium-238 nuclei during the formation of cracks in geologically (seismic and volcanically) active zones of the Earth’s crust. The fissuring of the solid-phase medium leads to an increase in mechanical tensile stress and the emergence of strong local electric fields, resulting in the injection of chemical-scale high-energy electrons into the aqueous phase of the cracks. Under these conditions, the e^? catalytic decay of uranium-238 nucleus studied earlier can occur during the formation of metastable protactinium-238 nuclei with locally distorted nucleon structure, which subequently undergo β^–decay with the formation of thorium-234 and helium-4 nuclei as products of the fission of the initial uranium-238 nucleus with a characteristic period of several years. The observed increased activity of uranium-234 nuclei that form during the subsequent β-decay of thorium and then protactinium is associated with the initiated fission of uranium-238. The possibility is discussed of developing thermal power by using existing wastes from uranium production that contain uranium-238 to activate this isotope through the mechanochemical processing of these wastes in aqueous media with the formation of ₉₁ ²³⁸ Pa _isu , the half-life of which is several years.     

The Influence of the Calcination and Water Washing Treatments on the Uranium Content in Sedimentary Phosphate Samples Using Solid State Nuclear Track Detectors and Gamma-Ray Spectrometry

The uranium and thorium contents were evaluated in the 100–400 µm granulometric fraction of different sedimentary phosphate samples by using a method based on determining the mean critical angles of etching of the CR-39 and LR-115 type II solid state nuclear track detectors (SSNTD) for detecting -particles emitted by the nuclei of the uranium-238 and thorium-232 series. Data obtained were compared with the results of -ray spectrometry measurements performed on the same samples. The influence of the calcination and water washing treatments as well as the lithology and stratigraphy on the uranium concentration of the phosphate samples was investigated.     

Determination of uranium by neutron activation analysis using substoichiometric separation

Three analytical methods for uranium by neutron activation are described. The methods are based on the substoichiometric separation of barium or lanthanum, which are the fission products of uranium-235 by neutron irradiation. Uranium contents in high purity materials were determined by the methods, which were found to be useful for the determination of a trace amounts of uranium.     

Distribution pattern of REE and other elements in the host rocks of the Gubrunde uranium occurrence,NE Nigeria

Prospecting for high grade uranium deposits in NE Nigeria has over the years among other reasons been handicapped by lack of adequate understanding of the elemental primary dispersion pattern associated with known occurrences in this region. Thirty six samples from a low grade uranium occurrence at Gubrunde consisting of disseminated ores and hostrocks were therefore analyzed for 38 elements by NAA, DNAA, EDXRF and flame AAS techniques. The analytical data were evaluated using multivariate statistical techniques. The results show three element groupings (associations). The first group consists of Pb, Ba, Ce, Sm (LREE), that are enriched with increasing uranium concentration in the mineralized zone and are therefore capable of serving as pathfinder elements for uranium. The second group comprising of MgO, K₂O, CaO, Na₂O and the HREE are depleted in the mineralized zone due to action of hydrothermal fluids and are indicative of altered/mineralized rocks. The third group consists of the rest bulk of elements which feature little or no significant enrichment with increasing uranium but associate with ferruginization (haematite) and possibly refractory minerals.     

Analytical methods for the environmental quantification of uranium isotopes: Method of validation and environmental application

The use of depleted uranium in military ordinance has led to an increasing need to determine isotope-specific uranium concentrations in environmental matrices. To this end, gamma-ray spectrometry, ICP-MS and INAA methods have been validated, in accordance with the ISO 17025 standard. Reporting limits of 0.21 (U-235) and 0.91 (U-238) ng/L were obtained by ICP-MS analysis of water. Higher reporting limits were obtained for INAA (U-238 only) validations of water and gamma-ray spectrometric validations of soil and water. Accredited methods have been used to determine uranium concentration and isotope ratio of samples obtained from the Defence Research and Development Canada Valcartier, Quebec.     

Use of chromatographic pre-concentration for routine uranium bioassay analysis by ICP-MS

Routine monitoring of urine is an effective way to detect occupational intake of radioactive material. Historically, determinations of uranium isotopic ratios have been performed by radiochemical separation followed by alpha spectrometry. With recent advancements in technology, inductively coupled plasma-mass spectrometry (ICP-MS) has become widely available for the determination of trace metals as well as radioactive nuclides with long half-lives, such as ²³⁸U in urine. Furthermore, ICP-MS measurements of ²³⁸U do not require radiochemical separation since the number of atoms in the sample is determined instead of the number of alpha particles emitted. However, this method does not provide good sensitivity for the determination of ²³⁵U due to its shorter half-life. An improved procedure using pre-concentration of uranium and determination by ICP-MS decreases the detection limit by a factor of ten or greater with only slight increase in total analysis time. The method also has the capability of accurately determining the isotopic ratio of the sample, which is very important in cases where enriched or depleted uranium is involved.     

Characterisation of Radioactive Particles by SIMS

 Secondary ion mass spectrometry (SIMS) was optimised for characterisation of uranium- and plutonium-containing particles in soils, swipes and forensic samples. This was done by analysing in-house produced spherical UO₂-particles. Screening techniques as α-autoradiography together with SIMS analysis were employed to detect UO₂-particles in a soil sample from Chernobyl. The use of SIMS was exploited for the identification of uranium- and plutonium-containing particles and for the determination of their isotopic composition. The particles collected on swipe samples were transferred to a special adhesive support for the analysis by SIMS. Particles containing highly enriched uranium with diameters up to 10 μm were also detected in a forensic sample. For the measurements of the isotopic ratios a mass resolution of 1000 was used. At this resolution flat-top peaks were obtained which greatly improve the accuracy of the measurement. The isotopic composition of the particles was measured with a typical accuracy and precision of 0.5%. Statistically meaningful results can be obtained, for instance, from a specimen containing as few as 10¹⁰ atoms/μm³ of uranium in particles of UO₂ weighing a few picograms.     

Laser-induced breakdown spectroscopy measurements of uranium and thorium powders and uranium ore

Laser-induced breakdown spectroscopy (LIBS) was used to analyze depleted uranium and thorium oxide powders and uranium ore as a potential rapid in situ analysis technique in nuclear production facilities, environmental sampling, and in-field forensic applications. Material such as pressed pellets and metals, has been extensively studied using LIBS due to the high density of the material and more stable laser-induced plasma formation. Powders, on the other hand, are difficult to analyze using LIBS since ejection and removal of the powder occur in the laser interaction region. The capability of analyzing powders is important in allowing for rapid analysis of suspicious materials, environmental samples, or trace contamination on surfaces since it most closely represents field samples (soil, small particles, debris etc.). The rapid, in situ analysis of samples, including nuclear materials, also reduces costs in sample collection, transportation, sample preparation, and analysis time. Here we demonstrate the detection of actinides in oxide powders and within a uranium ore sample as both pressed pellets and powders on carbon adhesive discs for spectral comparison. The acquired LIBS spectra for both forms of the samples differ in overall intensity but yield a similar distribution of atomic emission spectral lines.     

Uranium enrichment measurements using the intensity ratios of self-fluorescence X-rays to 92 keV gamma ray in UXKα spectral region

In this paper, the known multigroup γ-ray analysis method for uranium (MGAU) as one of the non-destructive γ-ray spectrometry methods has been applied to certified reference nuclear materials (depleted, natural and enriched uranium) containing ²³⁵U isotope in the range of 0.32-4.51% atom ²³⁵U. Its analysis gives incorrect results for the low component ²³⁵U in depleted and natural uranium samples where the build-up of the decay products begins to interfere with the analysis. The results reveal that the build-up of decay products seems to be significant and thus the algorithms for the presence of decay products should be improved to resulting in the correct enrichment value. For instance, for the case of ²³⁵U analysis in depleted uranium or natural ore samples, self-induced X-rays such as 94.6 keV and 98.4 keV lying in UXK_α spectral region used by MGAU can be excluded from the calculation. Because the significant increases have been observed in the intensities of uranium self-induced X-rays due to γ-ray emissions with above 100 keV energy arising from decay products of ²³⁸U and ²³⁵U and these parents. Instead, the use of calibration curve to be made between the intensity ratios of self-fluorescence X-rays to 92^* keV γ-ray and the certified ²³⁵U abundances is suggested for the determination of ²³⁵U when higher amounts of decay products are detected in the γ-ray spectrum acquired for the MGAU analysis.     

Chemical and radiochemical characterization of depleted uranium in contaminated soils

The main results of chemical and radiochemical characterization and fractionation of depleted uranium in soils contaminated during the Balkan conflict in 1999 are presented in the paper. Alpha-spectrometric analysis of used depleted uranium material has shown the presence of man-made radioisotopes ²³⁶U, ²³⁷Np, and ^{239, 240}Pu traces. The fractionation in different soil types was examined by the application of a modified Tessier’s five-step sequential chemical extraction procedure, specifically selective to certain physical/chemical associations. After ion-exchange-based radiochemical separation of uranium, depleted uranium is distinguished from naturally occurring uranium in extracts on the basis of the isotopic activity ratios ²³⁴U/²³⁸U and ²³⁵U/²³⁸U and particular substrates for recently present uranium material in soils are indicated. The text was submitted by the authors in English.     

A comparative study of some nuclear methods for235U/238U isotopic ratios determination

In the present work, a comparative study is made among nuclear methods for²³⁵U/²³⁸U ratios determination: activation analysis followed by high-resolution gamma-ray spectrometry, delayed neutron counting, passive gamma-ray and alpha spectrometry. Activation analysis followed by high-resolution gamma-ray spectrometry yielded a relative standard deviation down to 0.1% and a relative error of about 1% for standards of uranium enriched to 14%. Passive gamma-ray spectrometry using Ge(Li) detectors yielded a relative error down to 0.1% for enriched uranium and values even lower for the standard deviation. Passive gamma-ray spectrometry using Low Energy Photon Detector (LEPD) yielded a precision of 0.2% and a still better accuracy for enriched standards. In the case of alpha spectrometry, a relative error down to 0.5% and a precision of about 1% were obtained, also for enriched uranium standards. Delayed neutron counting allowed a relative standard deviation of about 7% and a relative error of about 2%, for standards of depleted uranium.     

Extractive scintillating polymer sensors for trace-level detection of uranium in contaminated ground water

This contribution describes the synthesis of robust extractive scintillating resin and its use in a flow-cell detector for the direct detection of uranium in environmental waters. The base poly[(4-methyl styrene)-co-(4-vinylbenzyl chloride)-co-(divinylbenzene)-co-(2-(1-napthyl)-4-vinyl-5-phenyloxazole)] resin contains covalently bound fluorophores. Uranium-binding functionality was added to the resin by an Arbuzov reaction followed by hydrolysis via strong acid or trimethylsilyl bromide (TMSBr)-mediated methanolysis. The resin was characterized by Fourier-transform infrared spectroscopy and spectrofluorometry. Fluorophore degradation was observed in the resin hydrolyzed by strong acid, while the resin hydrolyzed by TMSBr-mediated methanolysis maintained luminosity and showed hydrogen bonding-induced Stokes' shift of ∼100 nm. The flow cell detection efficiency for uranium of the TMSBr-mediated methanolysis resin was evaluated at pH 4, 5 and 6 in DI water containing 500 Bq L⁻¹ uranium-233 and demonstrated flow cell detection efficiencies of 23%, 16% and 7%. Experiments with pH 4, synthetic groundwater with 50 Bq L⁻¹ uranium-233 exhibited a flow cell detection efficiency of 17%. The groundwater measurements show that the resins can concentrate the uranyl cation from waters with high concentrations of competitor ions at near-neutral pH. Findings from this research will lay the groundwork for development of materials for real-time environmental sensing of alpha- and beta-emitting radionuclides.     

母岩高铀离子型稀土矿采区的放射性污染风险浅析

铀与稀土元素同属大离子亲石元素,尤其与钇组稀土关系更密切,因此南岭高铀花岗岩往往同时是铀和离子型重稀土矿床的成矿母岩。国内外研究资料表明,高铀花岗岩中的铀主要以原生铀的形式存在于晶质铀矿中,在强烈风化过程中大部分发生活化转移,而采矿活动对此有显著促进作用;国外众多含铀湿地的发现及其研究资料表明,山区湿地是铀的"高效过滤器"和"沉淀池",花岗岩风化转移到水体中的微量铀经长期累积,可在湿地富有机质土壤和沉积物中富集至(3000~4000)×10^-6,而采矿和农垦活动可将湿地经几千年累积富集起来的铀释放到居民的生活环境中,因而被视为是一种环境风险。因此建议加强母岩高铀离子型稀土矿区的湿地放射性调查和环境保护,以保障湿地对重金属的天然过滤功能,避免湿地束缚铀的释放,这对保护矿区水质和生态环境都具有重要意义。     

Application of neutron well coincidence counting for plutonium determination in mixed oxide fuel fabrication plant

Mixed oxide (MOX) fuel is an alternative to conventional enriched uranium oxide fuel in thermal reactors. Indian interest in plutonium recycle in thermal reactors is primarily due to the need to develop alternative indigenous fuel for two boiling water reactors (BWR) at Tarapur, which are designed to use imported light enriched uranium fuel. A few MOX assemblies have been fabricated and loaded into the reactors. Neutron well coincidence counting (NWCC) system has been successfully employed to check the enrichments of PuO₂ in MOX blends. NWCC has also been successfully applied in developing dry recycling process of clean rejected oxide (CRO) and dirty rejected oxide (DRO).     

Solvent Extraction and Spectrophotometric Determination of Uranium Using α-Benzoin Oxime as Chelating Agent

Solvent extraction of uranium by a chloroform solution of α-benzoin oxime was studied and the formation of uranium-α-benzoin oxime complex described. The uranium-α-benzoin oxime complex has two maximum absorbance at 350 nm and 427 nm. A constant absorbance was obtained for 1 × 10^?3 M uranium when the concentration of α-benzoin oxime was higher than 1.2 × 10^?2 M. Ions of Ag⁺, Fe³⁺, V⁵⁺, Cu²⁺, and W⁶⁺ were found to have interference. A solution containing 0.1–10 mg uranium at pH 1.6–6.8 was extracted with 1 × 10^?3 M ?2 × 10^?3 M α-benzoin oxime solution in chloroform. With single extraction, the maximum amount of uranium passing into organic layer was at least 98%. Under this condition the presence of diverse ions except V⁵⁺ does not significantly interfere the extraction of uranium.     

Validation of scanning electron microscope (SEM), energy dispersive X-ray (EDX) and gamma spectrometry to verify source nuclear material for safeguards purposes

Ten ore samples, two unpurified yellow cake samples and natural uranyl nitrate hexahydrate sample were analyzed by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX) method to verify source nuclear material. Samples represent source nuclear material as possible. All samples were scanned at ideal conditions; working distance = 10 mm, voltage = 30 kV, magnification value = × 100, spot size = 50 to screen samples for the presence of uranium and thorium, Also Hyper pure germanium (HPGe) gamma spectrometers were applied to estimate the uranium and thorium contents in Bq/kg (ppm). For the ore samples uranium-238 ranges from 1,049.23 Bq/kg (85.30 ppm) to 2,096.06 Bq/kg (170.41 ppm), uranium-235 ranges from 47.51 to 105.61 Bq/kg and thorium-232 ranges from 22.84 Bq/kg (5.65 ppm) to 41.78 Bq/kg (10.34 ppm). For the yellow cake samples and uranyl nitrate hexahydrate uranium-238 ranges from 42.99 Bq/kg (3.50 ppm) to 71,887.2 Bq/kg (5,844.49 ppm) and thorium-232 is 4.78 Bq/kg (1.83 ppm) and the other two samples are lower than the detection limit.     

A single-laboratory validated method for the generation of DNA barcodes for the identification of fish for regulatory compliance

The U.S. Food and Drug Administration is responsible for ensuring that the nation's food supply is safe and accurately labeled. This task is particularly challenging in the case of seafood where a large variety of species are marketed, most of this commodity is imported, and processed product is difficult to identify using traditional morphological methods. Reliable species identification is critical for both foodborne illness investigations and for prevention of deceptive practices, such as those where species are intentionally mislabeled to circumvent import restrictions or for resale as species of higher value. New methods that allow accurate and rapid species identifications are needed, but any new methods to be used for regulatory compliance must be both standardized and adequately validated. "DNA barcoding" is a process by which species discriminations are achieved through the use of short, standardized gene fragments. For animals, a fragment (655 base pairs starting near the 5' end) of the cytochrome c oxidase subunit 1 mitochondrial gene has been shown to provide reliable species level discrimination in most cases. We provide here a protocol with single-laboratory validation for the generation of DNA barcodes suitable for the identification of seafood products, specifically fish, in a manner that is suitable for FDA regulatory use.     

A Review: Studies on Uranium Removal Using Different Techniques. Overview

The presence of uranium in soil and underground water generate an important issue against public perception on the risk, which the contamination poses to the environmental and human health. Uranium is the dangerous element found in nature, it found in all rocks with different ratios. As nuclear science developed, nuclear waste containing uranium increased. Contamination reached to soil, underground water and in some cases drinking water which has increased public health concerns due to the chemical toxicity of depleted uranium at elevated dosages. For this reason this review concerned to develop methods for uranium removal from low-grade and contaminated sources. There are several stationary phases and solvents used in uranyl separation process as amines in different type (primary, secondary, tertiary, and quaternary amine), phosphates, acetates, alcohols, phenols and amidoxime resins. The article addresses the main features of the following techniques for uranium: found on soil, chemical processes for separation from contaminated soils and liquor by various suitable solvent, removal by chelating resins, impregnated, and imprinted ones.