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1.
Quantitative determination of uranium in (U, Pu)O 2 fuels is usually done by the DAVIES-GRAY method. High concentrations of phosphoric acid in the analytical waste generated by this method make the revocery of plutonium rather complex. Studies on the recovery of plutonium from nitric acid medium containing different concentrations of H 3PO 4 by conventional anion-exchange procedure reveal that more than 90% of the plutonium can be easily recovered when the phosphoric acid concentration is less than 0.5 M in the solution. A method was developed for the determination of uranium in the presence of plutonium, which involves the reduction of U(VI) to U(IV) by Fe(II) in a medium of 3.5M H 3PO 4 +4.5M H 2SO 4 instead of 10–11M H 3PO 4 so as to have the H 3PO 4 concentration 0.6M in the waste. A number of determinations of uranium in UO 2(NO 3) 2 working standard solutions and (U, Pu) synthetic solutions with uranium at the 3–7 mg level were carried out by this method. The precision obtained was better than ±0.2% and the accuracy was also within the precision limits. The resulting analytical waste generated was directly subjected to anion exchange separation for the recovery of plutonium which was found to be more than 90%. 相似文献
2.
Chemical characterization of rubidium uranium(IV) trisulfate, Rb 2U(SO 4) 3, a new chemical assay standard for uranium requires accurate analysis of rubidium. A gravimetric and an X-ray fluorescence method (XRF) for the determination of rubidium in this compound are described. In the gravimetric method, rubidium is determined as Rb 2Na[Co(NO 2) 6].H 2O without separating uranium with a precision of the order of ±0.5%. In the XRF method, the concentration ratio of rubidium to uranium, C Rb/C U, is determined in the solid samples by the binary ratio method using calibration between intensity ratios (I Rb/I U) and concentration ratios (C Rb/C U). The concentration of rubidium is derived using the uranium value which is known with a precision better than ±0.05%. The XRF method has a precision better than ±0.8% for rubidium determination. 相似文献
3.
A study of the factors which affect the gravimetric determination of uranium in uranyl nitrate is described. In the gravimetry of uranium, the U 3O 8 (weighing form) produced by ignition is usually assumed to deviate <0.02% from theoretical composition; and elemental impurities are assumed to form common oxides within the U 30 8 matrix. It is shown that these assumptions are incorrect. Ignition temperature and time affect U 3O 8 stoichiometry. Ignitions of uranyl nitrate for 1–3 h at 850° produce U 3O 8 that deviates as much as 0.15% from stoichiometric U 3O 8; deviations are negligible when uranyl nitrate is ignited at 1000° for 2 h. Elemental impurities, particularly calcium and phosphorus, affect the composition of U 3O 8 formed in the ignition of uranyl nitrate. A variety of impurity complexes such as uranates and phosphates are found within the U 3O 8 matrix. Formation of these impurity complexes depends on the elements present, their concentration, and ignition temperature. Therefore, in the gravimetric determination of uranium in uranyl nitrate, the effects of ignition parameters and nonvolatile impurities must be considered in order to obtain accurate uranium determinations. 相似文献
4.
A biamperometric methodology for the sequential determination of thorium (Th) and uranium (U) was developed. In the sample solution containing Th and U, Th was first determined by complexometric titration based on the electrochemical behaviour of EDTA maintaining a potential of ≥200 mV between the twin Pt electrodes. This was followed by the redox titrimetric determination of U employing biamperometry to detect the end point. Prior to the determination of U, EDTA was destroyed by fuming with concentrated HClO 4 to eliminate its interference in the U determination. The method was tested for the determination of Th and U in (Th, U) O 2 samples containing 4 mg of Th and 2–8 mg of U, with precision and accuracy of better than 0.3 %. 相似文献
5.
A method for quantitative determination of uranium in phosphoric acid and wet phosphoric acid has been developed. After reduction with Fe, uranium(IV) is extracted with a kerosene solution of octylphenylphosphoric acid. The uranium was stripped with 10M H 3PO 4, containing H 2O 2, and then determined spectrophotometrically with Arsenazo III and by direct uranium(IV)-phosphoric acid solution measurements. 相似文献
6.
A modified LED fluorimetry determination of uranium in Nb/Ta minerals has been developed. The mineral is brought into solution by fusion with mixed phosphate flux (NaH2PO4, H2O and Na2HPO4). Iron quenches uranium fluorescence when it is present above the ratio of (iron to uranium) 100. Uranium is separated in ethyl acetate by solvent extraction and then stripped back into pyrophosphate buffer (pH ~ 7) prior to its LED fluorimetry determination. This modified method has been applied for the determination of uranium in synthetic mixtures and Nb/Ta minerals including Certified Reference Materials (X1807) with high degree of accuracy and precision. 相似文献
7.
A new volumetric method has been proposed for the determination of beryllium in beryls and associated minerals. The method involves the direct precipitation of beryllium as BeNH 4PO 4.6H 2O in presence of complexone II, dissolving the precipitate in dilute perchloric acid and titrating the liberated phosphate with standard bismuthyl perchlorate. Results for samples agree within ± 0.2% of the standard values. 相似文献
8.
Results from tests aimed at optimizing an instrumental procedure for the direct and fast determination of uranium in solution
by laser fluorescence are presented. A comparison of sample fluorescence measured using different fluorescence enhancing reagents
was performed: sodium pyrophosphate, orthophosphoric acid, sulphuric acid and a commercially available fluorescence enhancer
were tested for the determination of uranium. From the experimental results, 0.01 M Na 4P 2O 7·10H 2O showed the best performance. Effects of reagent pH, different matrices, different concentrations of dissolved Th, and sample
volume were investigated. Applications of the improved procedure for the determination of uranium in samples arising from
UO 2-based high level nuclear waste dissolution studies are described. 相似文献
9.
This paper presents studies on direct non-destructive determination of uranium in sintered deeply depleted (DD) uranium oxide (UO2) pellets by wavelength dispersive X-ray fluorescence (WDXRF) spectrometry. A special collet was designed and fabricated for holding the sintered DDUO2 pellets for direct analysis, thus avoiding the sample preparation steps. The samples were analyzed using a calibration plot obtained from WDXRF spectra of matrix matched calibration standards. The WDXRF determined uranium values were found to be in very close agreement with titrimetric values and has reproducibility better than 0.05% (RSD, 1 s, n = 10) for the sintered DDUO2 pellets having U: 86.81–88.04 wt%. 相似文献
10.
Some gravimetric methods for determining cobalt have been examined in order to assess their value for the accurate determination of the metal. The electrolytic method was found to give high results (about 1.4%), and the anthranilate method slightly high results (0.2 – 0.3%). A modification of the phosphate method has been developed in which a former drawback, the solubility of CoNH 4PO 4·H 2O, has been overcome using a rapid spectrophotometric determination of residual cobalt. The final procedure developed has been found to give accurate results ( ±0.1 – 0.2%) and its use is recommended where this degree of accuracy is required. 相似文献
11.
A method is proposed for neutron activation determination of U via 239Np. This is separated by coprecipitation of ZrO(H 2PO 4) 2 and its 106 keV γ-peak measured. The sensitivity of the determination is 10 −9 g. The method is based on the well-known ability of Np(IV) to coprecipitate with zirconium phosphate, while Np(VI) does not
form insoluble phosphates or fluorides. This permits elimination of elements interfering, with the determination of 239Np via the 106 keV γ-peak: Sm, Nd, Yb, Lu, Pa (from Th) and Ta. The rare earths are eliminated by coprecipitation on LaF 3, and Pa and Ta as insoluble phosphates in an oxidizing medium. The method is suitable for phosphorus-containing samples:
phosphorites, apatites and their industrial treatment products. The results obtained for the uranium content with the proposed
method are in good agreement with the results of other methods and authors. 相似文献
12.
A fluorescence based method has been developed for the determination of trace amounts of uranium in thorium matrix using a mixture of phosphoric acid (H 3PO 4) and sulfuric acid (H 2SO 4), as fluorescence enhancing reagent for uranyl (UO 2 2+) ion fluorescence. Synthetic samples mimicking the composition of ThO 2 fuel were prepared and the concentration of U(VI) was estimated. Satisfactory results are obtained when uranium is present at a concentration of 10 ppm in solid thorium samples with good precision. 相似文献
13.
A potentiometric titration method was developed for the determination of plutonium and uranium in the same aliquot in nitric acid medium. Plutonium was first determined by oxidation to Pu/VI/ by fuming with conc. HClO 4. Pu/VI/ formed was reduced to Pu/IV/ with known excess of Fe/II/ and the excess Fe/II/ was titrated with standard K 2Cr 2O 7 to a potentiometric end point. Uranium in the same solution was determined by reduction to U/IV/ with Fe/II/ in conc. H 3PO 4 medium and titrating U/IV/ formed with standard K 2Cr 2O 7 using the potentiometric end point detection technique. For the quantity of plutonium and uranium each in the range of 3–5 mg per aliquot a precision of ±0.2% and ±0.4%, respectively, was obtained. 相似文献
14.
A method for the gravimetric determination of cerium as Ce 3(PO 4) 4 is described. Cerium can be separated from many metals in this form, as well as from permanganate and dichromate; the cerium separated can then be titrated with iron(II) solution. The method was verified for the determination of cerium in a rare earth concentrate. 相似文献
15.
The potentiometric determination of uranium is widely carried out in phosphoric acid medium to suppress the interferences of plutonium by complexation. Owing to the complexity of the recycling plutonium from the phosphate based waste involving manifold stages of separation, a method has been proposed in the present paper which does not use phosphoric acid. Uranium and plutonium are reduced to U/IV/ and Pu/III/ in 1M H 2SO 4 by Ti/III/, and NaNO 2 is chosen to selectively oxidize Pu/III/ and the excess of Ti/III/. The unreacted NaNO 2 is destroyed by sulphamic acid and excess Fe/III/ is added following dilution. The equivalent amount of Fe/II/ thus liberated is titrated against standard K 2Cr 2O 7. R.S.D. obtained for the determination of uranium /1–2 mg/ is 0.3% with plutonium being present upto 4.0 mg. 相似文献
16.
Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies on uranium doped calcium phosphate yielded mechanistic information on the observed glow peaks at 365, 410 and 450 K. TSL spectral studies of the glow peaks showed that UO 2
2+ acts as the luminescent center. Electron paramagnetic resonance studies on gamma-irradiated samples revealed that the predominant radiation induced centers are H 0, PO 4
2-, PO 3
2- and O - ion. Studies on the temperature dependence studies of the EPR spectra of samples annealed to different temperatures indicate the role of H 0 and PO 4
2- ions in the main glow peak at 410 K. 相似文献
17.
The uranium contents in phosphorites from North Africa, products of their processing (H 3PO 4, superphosphates, phosphogypsum), lignites from South Bulgaria and products of their burning, copper ores and concentrates have been determined by instrumental and radiochemical NAA. An evaluation of the contribution of the phosphoric fertilizers to the uranium content of soil, plants, breeding stock and man has been done. 相似文献
18.
A direct gravimetric method for the determination of titanium with a new reagent, 1-( o-carboxyphenyl)-3-hydroxy-3-phenyltriazene, is proposed. The titanium is precipitated at the pH range 2.0–5.0 and weighed as TiO(C 13H 10N 3O 3) 2 after drying at 115–120°. In the presence of EDTA, only niobium and tantalum interfere. 相似文献
19.
An extraction and spectrophotometric method for determination of trace amounts of uranium in phosphate fertilizers is described. It is based on the extraction of uranium with trioctylphosphine oxide in benzene and the spectrophotometric determination of uranium with Arsenazo III in buffer-alcoholic medium. The maximum absorbance occurs at 655 nm with a molar absorptivity of 1.2·10 4 l·mol –1·cm –1. Beer's law is obeyed over the range 0.6–15.0 g·ml –1 of uranium(VI). The proposed method has been applied successfully to the analysis of phosphate fertilizers with phosphate concentrations of 45% P 2O 5. 相似文献
20.
A new method using MCE with LIF detection was developed for the determination of hydrogen peroxide (H 2O 2). Bis(p‐methylbenzenesulfonyl)dichlorofluorescein, a new fluorogenic reagent synthesized by our laboratory was employed as a labeling reagent, the derivatization reaction was performed in 0.10 M HEPES buffer (pH 7.4) for 30 min at 37°C. The detection of H 2O 2 was accomplished in 55 s, using a 40 mM HEPES buffer, 20% mannitol, pH 7.4, on a glass microchip. The RSDs of migration time and peak area were 1.8 and 3.7%, respectively. Method validation showed the linear response ranging from 0.50 to 50 μM with an LOD ( S/ N=3) of 0.20 μM (19.1 amol). The proposed method was applied to determine H 2O 2 in phorbol myristate acetate‐stimulated RAW264.7 macrophages, the concentration of H 2O 2 was found to be 1.86±0.05 μM; recoveries for macrophage samples were from 96.7 to 97.8%, within‐days and between‐days accuracies were 4.5% ( n=5) and 6.8% ( n=5), respectively. 相似文献
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