A rapid and accurate method to measure uranium was established using gamma spectroscopy with a high purity germanium detector. This can be done by measuring the gamma radiation intensity at 186 keV which corresponds to the concentration of 235U only since all the 226Ra which also shows a peak at this energy level, remains in the solid phosphogypsum. The method was proved to be accurate when compared with other methods. It has also the advantage of measuring uranium concentrations over a wide range suitable to the operation of the pilot plant for extraction of uranium from wet process phosphoric acid without the need to dilution or concentration. It can also measure the uranium in the different media such as acid, organic or alkaline media found in the pilot plant at different stages.
Authors:Giorgos Andreou, Maria Efstathiou, and Ioannis Pashalidis
A relatively rapid, economic and robust procedure is described for the radiometric analysis of uranium in phosphate rock and
phosphogypsum. The analysis is performed by alpha spectroscopy after pre-concentration and separation of uranium by liquid-extraction
using tributyl-phosphate (30% TBP in dodecan) and finally its electrodeposition on stainless steel discs. The method has been
successfully applied to 0.1 g samples of phosphate rock and phosphogypsum resulting in high-quality spectra for measurement
times ≥15 h. The main advantage of the procedure is the use of tracer solution (232U) that allows reliable measurements and evaluation of the separation procedure. The separation efficiency of the proposed
method has been estimated to be (75 ± 20)%.
In divalent tin halides, when the halogen is small and highly electronegative (F, Cl), the tin valence orbitals are hybridized, the tin(II) non-bonded electron pair is located on one of the hybrid orbitals, and the resulting large electric field gradient gives a large quadrupole splitting. The reaction of barium chloride and tin difluoride in aqueous solutions, for large BaCl2.2H2O/SnF2 ratios (>10) results in the precipitation of a white powdered material, which is identified by X-ray diffraction to be BaCIF. However, Tin-119 Mossbauer spectroscopy shows the material contains a fairly large amount of divalent tin in the Sn2+ ionic form, with unhybridized orbitals, like in SnCl2. Using X-ray diffraction, we have established that Sn2+ ions substitute 15% of the Ba2+ ions at random, and chemical analysis shows the material has the formula Ba5.66SnCl7.30F6.04 and thus is enriched in chlorine.
Authors:László Szentmiklósi, Tamás Belgya, Zsolt Révay, and Zoltán Kis
The Budapest Research Reactor’s Prompt Gamma Activation Analysis (PGAA) and Neutron-Induced Prompt gamma Spectroscopy (NIPS)
facilities were significantly upgraded during the last few years. The higher neutron flux, achieved by the partial replacement
and realignment of the neutron guides, made feasible the automation and specialization of the two experimental stations. A
new neutron flux monitor, computer-controlled beam shutters and a low-level counting chamber have been put into operation
to assist with in-beam activation experiments. An automatic sample changer has been installed at the PGAA station, while the
NIPS station was redesigned and upgraded with a Compton suppressor to use for the non-destructive analysis of bulky samples.
In the near future the latter setup will be completed with a neutron tomograph and a moving table, to turn it into a Neutron
Radiography/Tomography-driven PGAA equipment.
Authors:Astitva Anand, Mohinder Singh Dahiya, and Rakhi Agarwal
Benzene is an omnipresent liquid in industries. The occupational exposure to benzene leads to the urinary excretion of benzene metabolites, viz., phenol, pyrocatechol, hydroquinone, and trihydroxybenzene, due to its biotransformation. These metabolites are phenolic in nature and considered as immediate biomarkers of benzene exposure. The present work includes the separation and determination of urinary phenolic benzene metabolites by coupling two different techniques. Thin-layer chromatography (TLC) was used as the separation technique to get individually separated spots of all four metabolites, which were further quantified by ultraviolet (UV)–visible spectroscopy at 765 nm. For the development of the separated spots on TLC plate and determination of metabolites by UV–visible spectroscopic method, alkaline Folin‒Ciocalteau reagent was used. Folin‒Ciocalteau reagent is having wide applications for phenol determination and gives blue color with almost all types of phenols. The colored solutions were measured against the blank disk taken from the developed spots on plastic TLC plate. Based on the obtained results, a simple, rapid, and sensitive method for the quantitation of urinary phenolic benzene metabolites has been developed and validated according to the International Conference on Harmonization (ICH) guidelines. The validated method was efficaciously applied to cigarette smokers and petrol station workers, and it was found that the method has favorable application in the routine analysis of urine samples of benzene-exposed population.
Authors:Mahmoud El-Sharif, C. Chisholm, I. Brooke, E. Kuzmann, and A. Vértes
119Sn conversion electron Mössbauer spectroscopy, X-ray diffractometry and energy dispersive X-ray analysis (EDAX) were employed to investigate microstructure, composition and phases present in as-electroplated Sn-Cr and Sn-Cr-Zn alloys deposited on copper substrates. In the Sn-Cr deposits Cu, -Sn, Cr-Sn phases can be identified by X-ray diffractometry. The phase composition is significantly different between the samples prepared with relatively higher and lower current densities. In the diffractograms of Sn-Cr-Zn deposits Cu, -Sn, Zn phases can be well identified. A small intensity amorphous peak is also present, which can perhaps be associated with the presence of some amorphous Zn and Sn alloy. 119Sn Mössbauer spectra of Sn-Cr deposits exhibit an asymmetric broad main line centered near the isomer shift characteristic of -Sn as well as they contain a small component near the zero velocity which can be attributed to a SnO2 phase based upon its characteristic. 119Sn Mössbauer spectra of Sn-Cr-Zn deposits are roughly similar to those of Sn-Cr deposits although the Mössbauer parameters of the third phase are different and vary with the Zn content. The presence of SnO2 on the surface mainly in the Sn-Cr samples can be attributed to the corrosion process in the air.
Summary The reaction of a hydrated nitrate salt of lanthanide (Ln=Pr, Nd, Gd, Dy, Er) with the polyfunctional ligand salicylhydroxamic acid (H3sha), in the presence of base, afforded solid compounds, insoluble in common organic solvents and in water. The new complexes characterized by means of elemental analyses (C, H, N, Ln), magnetic moment determinations and spectroscopic data (IR, MS). It is proposed that they are neutral, with a possible polymeric structure of the general type: [Ln2(Hsha)2(H2sha)(DMF)x(CH3O)(H2O)]n×2H2O Their thermal decomposition was studied in nitrogen and/or oxygen atmosphere, between 25-1000°C by using simultaneous TG/DTG-DTA technique. The IR spectroscopy used to determine the intermediates and the final products. The intermediates at 180°C suggest the formation of N-hydroxylactam complex, which upon further heating gives a carbonaceous residue of Ln2O3 at 1000°C in nitrogen, while in oxygen the stable oxides are formed at 600°C.
Authors:N. Sergent, P. Gélin, L. Périer-Camby, H. Praliaud, and G. Thomas
The interactions of CO with a high specific surface area tin dioxide was investigated by FTIR spectroscopy and thermogravimetric
analysis. FTIR study of CO interactions have shown that CO can adsorb on cus (coordinatively unsaturated sites) Sn4+ cation sites (band at 2201 cm-1). In addition, CO reacts with surface oxygen atoms. This leads to the partial reduction of SnO2 surface and to the formation of ionised oxygen vacancies together with the release of free electrons, which are responsible
for the loss of transmission. Formed CO2 can chemisorb on specific surface sites: on basic sites to form carbonates species and on acidic sites (Sn4+-CO2 species) which is in competition with the formation of Sn4+-CO species. TG experiment have shown that the reduction of SnO2 by CO at 400°C occurs in two steps. First, the reduction of SnO2 surface, which is a quick phenomenon. This has allowed to evaluate that more than 12% of reducible surface oxygens can react
with CO, essentially because of the presence of a large amount of surface hydroxyl groups. The second step of the reduction
of SnO2 would be the progressive reduction of SnO2 bulk by the slow diffusion of oxygen atoms from the bulk to the surface.
Authors:Z. Homonnay, P. Szilágyi, E. Kuzmann, K. Varga, Z. Németh, A. Szabó, K. Radó, J. Schunk, P. Tilky, and G. Patek
57Fe-conversion electron Mössbauer spectroscopy (CEMS) — a sensitive tool to analyze the phase composition of corrosion products
on the surface of stainless steel — was applied to study real specimens from the Paks Nuclear Power Plant, Hungary. The primary
circuit side of the heat exchanger tubes was studied on selected samples cut out from the steam generators during regular
maintenance. Mostly Cr-and Ni-substituted magnetite, amorphous Fe-oxides/oxyhydroxides as well as the signal of bulk austenitic
steel of the tubes were detected. The level of Cr-and Ni-substitution in the magnetite phase could be estimated from the Mössbauer
spectra. It is suggested that Cr-Ni substitution occurs simultaneously so that the inverse spinel structure of magnetite is
preserved up to a certain limit which appears to be roughly at [Fe3+]tet[Fe2+1/4Ni2+3/4Fe3+1/4Cr3+3/4]octO4. Further decrease of the iron content of this phase results in the formation of nickel chromite of regular spinel structure,
with very low Fe content. This transformation may be responsible for the hybrid structure of the protective oxide layer, being
substantially accelerated by previously performed, factory developed and proposed AP-CITROX decontamination cycles.
Two complimentary spectroscopic techniques, X-ray absorption and fluorescence spectroscopy have been conducted at spatial
scales of 1 to 25 μm on uranium contaminated soil sediments collected from two former nuclear materials processing facilities
of the DOE: Fernald, OH and Savannah River Site, SC. A method of imbedding particles in a non-reactive Si polymer was developed
such that individual particles could be examined before and after extraction with a wide range of chemicals typically used
in sequential extraction techniques and others proposed forex situ chemical intervention technologies. Using both the micro-X-ray fluorescence (XRF) and micro-X-ray Absorption Near Edge Structure
(XANES) techniques, both elemental and oxidation state distribution maps were generated on individual particles before and
following chemical extraction. XANES can determine the relative proportion of U(VI) and U(IV) in phases comprising individual
particles before and after extraction and showed that greater than 85% of the uranium existed as hexavalent U(VI). Fluorescence
spectra of contaminated particles containing mainly U(VI) revealed populations of uranyl hydroxide phases and demonstrated
the relative efficacy and specificity of each extraction method. Correlation of XAS and fluorescence data at micron scales
provides information of U oxidation state as well as chemical form in heterogeneous samples.