Complexometric determination of thorium in ThO2−PuO2

A method based on the complexometric titration of thorium using ethylene diaminetetra-acetic acid (EDTA) as complexant has been developed for the determination of thorium in thorium-plutonium solution without resorting to prior separation of plutonium. Plutonium in the form of Pu(VI) does not affect the thorium determination when present up to 10% in thorium—plutonium solution. For oxidation of plutonium to Pu(VI), HClO₄ or AgO was used. HClO₄ is preferred. The thorium values obtained without prior separation of plutonium are compared with those obtained after separating plutonium by anion exchange technique. A precision of ±0.5% has been obtained for 5–10 mg of thorium in the aliquot.     

A titrimetric method for the sequential determination of thorium and plutonium

A method for the sequential determination of thorium and plutonium has been developed. In the sample solution containing thorium and plutonium, thorium is first determined by complexometric titration with EDTA and then in the same solution plutonium is determined by redox titration employing potentiometry. Prior to the determination of plutonium, EDTA is destroyed by fuming with concentrated HClO₄. Thorium is determined at 10 mg level and plutonium at 1 mg level with precision and accuracy of better than ±0.5%.     

Redox determination of uranium in presence of plutonium in low phosphoric acid medium and the recovery of plutonium

Quantitative determination of uranium in (U, Pu)O₂ 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 H₃PO₄ 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 H₃PO₄ +4.5M H₂SO₄ instead of 10–11M H₃PO₄ so as to have the H₃PO₄ concentration 0.6M in the waste. A number of determinations of uranium in UO₂(NO₃)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%.     

Determination of uranium and plutonium in plutonium based fuels by sequential amperometric titration

A method is described for the sequential determination of uranium and plutonium in plutonium bearing fuel materials. Uranium and plutonium are reduced to U(IV) and Pu(III) with titanous chloride and then titrated with dichromate to two end points which are detected amperometrically using two polarized platinum electrodes. Uranium-plutonium solutions of known concentrations containing plutonium in the proportions of 4, 30, 50, and 70% were analyzed with precisions better than 0.3%, maintaining the amounts of plutonium per aliquot in the range of 2–10 mg. No significant bias could be detected. Several samples of (U, Pu)O₂ and (U, Pu)C were analyzed by this procedure. The effects of iron, fluoride, oxalic acid and mellitic acid on the method were also studied.     

An optical-fibre laser photometer for on-line measurements

An optical-fibre laser photometer is described for measuring on-line the concentration of the different oxidation states of uranium and plutonium. It is based on a dye laser with five exchangeable curvettes containing five different dyes. The dye laser is pumped by a nitrogen laser. To compensate for the influence of the concentration of nitrate on the absorbance of the different species, the conductivity of the solution is measured to give a correction factor. Fibre optics are used to connect the dye laser, the optical flow-through cell and the photometer. The deviation for the plutonium concentration for single-sample analysis is <1 g l^?1 for concentrations up to 50 g l^?1, and in the on-line mode is <0.14 g l^?1 for the same concentration range. For uranium, the deviation is <3.07 g l^?1 for a concentration range up to 77 g l^?1 in the on-line mode.     

A ratio derivative spectrophotometric method for the simultaneous determination of uranium and plutonium

A ratio derivative spectrophotometric method has been developed for the simultaneous determination of uranium and plutonium at mg levels in 1M HNO₃ medium. In this method the overlapping spectra of uranium and plutonium are well resolved by making use of the first derivative of the ratios of their direct absorption spectra. The derivative ratio absorbances of uranium and plutonium are measured at 411.2 and 473.8 nm, respectively for their quantification. The method is simple, fast and does not require separation of uranium and plutonium. Another salient feature of the method is that it does not lead to generation of analytical waste thereby minimising the efforts required for the recovery of plutonium. Uranium in the conc. range of 10–25 mg/g and plutonium in the conc. range of 0.5 to 2 mg/g (U/Pu ratio varying from about 10 to 25) were determined in the same aliquot with a precision and accuracy of about 0.5% and 1%, respectively.     

Simultaneous determination of uranium and plutonium at trace levels in process streams using Arsenazo III by derivative spectrophotometry

A derivative spectrophotometric method has been developed for the simultaneous determination of uranium and plutonium at trace levels in various process streams in 3M HNO₃ medium using Arsenazo III. The method was developed with the objective of measuring both uranium and plutonium in the same aliquot in fairly high burn-up fuels. The first derivative absorbances of the uranium and plutonium Arsenazo III complexes at 632 nm and 606.5 nm, respectively, were used for their quantification. Mixed aliquots of uranium (20–28 μg/ml) and plutonium (0.5–1.5 μg/ml) with U/Pu ratio varying from 25 to 40 were analysed using this technique. A relative error of about 5% was obtained for uranium and plutonium. The method is simple, fast and does not require separation of uranium and plutonium. The effect of presence of many fission products, corrosion products and complexing anions on determination of uranium and plutonium was also studied.     

Separation and Recovery of Uranium and Plutonium from Oxalate Supernatant

The separation of uranium and plutonium from oxalate supernatant, obtained after precipitating plutonium oxalate, containing ~10 g/l uranium and 30–100 mg/l plutonium in 3M HNO₃ and 0.10–0.18M oxalic acid solution has been carried out. In one extraction step with 30% TBP in dodecane: ~92% of uranium and ~7% of Pu is extracted. The raffinate containing the remaining U and Pu is extracted with 0.2M CMPO+1.2 M TBP in dodecane and near complete extraction of both the metal ions is achieved. The metal ions are back extracted from organic phases using suitable stripping agents. The recovery of both the metal ions separately is >99%. The uranium species extracted into the TBP phase from the HNO₃+oxalic acid medium was identified as UO₂(NO₃)₂·2TBP.     

Spectrographic determination of metallic impurities in PuO2

Summary An emission spectrographic method has been developed for the estimation of 22 metallic impurities in plutonium dioxide using carrier-distillation technique Silver chloride at 5% concentration in a charge of 100 mg has been used as the carrier. Mixed oxide standards containing 10% PuO₂ have been used for the analysis of matching composition of plutonium samples. Precision and accuracy determinations of the synthetic samples indicate 7–16% deviation for most of the elements. The work described includes analysis of reference samples and matrix effect studies. The method is suitable for the chemical quality control analysis of plutonium oxide to be used for Fast Breeder Test Reactor (FBTR) fuel.

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Spektralanalytische Bestimmung von metallischen Verunreinigungen in PuO₂

Zusammenfassung Mit dem Verfahren der Trägerdestillation können 22 Elemente in Plutoniumdioxid spektralanalytisch erfaßt werden. Als Träger dient 5% Silberchlorid in je 100 mg. Mischoxid-Standards mit 10% PuO₂ wurden verwendet. Bei der Untersuchung von Genauigkeit und Reproduzierbarkeit synthetischer Proben wurden für die meisten Elemente Abweichungen von 7–16% festgestellt. Matrixeinflüsse wurden ebenfalls untersucht sowie Analysenergebnisse für bestimmte Bezugsstandards mitgeteilt. Das Verfahren eignet sich für die Qualitätskontrolle von PuO₂-Brennstoffen für schnelle Brutreaktoren.

     

Extraction of uranium and plutonium from oxalate bearing solutions using phosphonic acid: Solvent extraction, extraction chromatography and infrared studies

Solvent extraction and extraction chromatography studies of uranium and plutonium from oxalate supernatant solutions were carried out using 2-ethyl hexyl-2-ethyl hexyl phosphonic acid (PC88A). Based on the distribution data, it was inferred that both the uranium and plutonium could be recovered satisfactorily from such a solution. These studies were found to be useful in optimising the appropriate concentration of PC88A, HNO₃, oxalic acid and temperature to recover more than 90% of plutonium from the large volumes of oxalate bearing waste solutions. Spectral characteristics of the extractant and its complexing behavior with U(VI) was also studied using IR & FTIR.     

Precipitation of plutonium oxalate from homogeneous solutions

A method for the precipitation of plutonium(IV) oxalate from homogeneous solutions using diethyl oxalate is reported. The precipitate obtained is crystalline and easily filterable with yields in the range of 92–98% for precipitations involving a few mg to g quantities of plutonium. Decontamination factors for common impurities such as U(VI), Am(III) and Fe(III) were determined. TGA and chemical analysis of the compound indicate its composition as Pu(C₂O₄)₂·6H₂O. Data are obtained on the solubility of the oxalate in nitric acid and in mixtures of nitric acid and oxalic acid of varying concentrations. Green PuO₂ obtained by calcination of the oxalate has specifications within the recommended values for trace foreign substances such as chlorine, fluorine, carbon and nitrogen.     

Spectrophotometric Determination of Nitrogen Dioxide <Nitrite>

Abstract

A highly sensitive spectrophotometric method has been developed for the determination of nitrogen dioxide (nitrite as NO_z ^?) by reacting manganese dioxide in 1:20 perchloric acid. An amount of manganese dioxide (MnO_z) equivalent to the concentration of nitrogen dioxide becomes soluble due to the reduction of Mn (IV) to Mn (II) by nitrite in acidic medium. The soluble Mn (II) ion is filtered to remove excess of MnO₂ and is oxidized to permanganate ion by periodic acid in presence of phosphoric acid. The violet colored solution shows maximum absorbance at 525 nm. The sensitivity of the method is 0.08 ppm based on 0.0044 absorbance, and Beer's law is obeyed in the concentration range of 0.2 to 10.0 μg/mL of NO₂ ^?. Molar absorbance is found to be 2442 at 525 nm.

In the present investigation NO₂ ^? was treated with excess of MnO₂ in 1:20 perchloric acid where NO₂ ^? reduces equivalent amount of Mn (IV) to Mn (II) and becomes soluble. The soluble Mn (II) was heated to boiling and 25 mg (approx.) periodic acid is added and cooled. The volume of each solution is made to 50 mL in volumetric flask. Reagent blank is prepared in similar way except sodium nitrite solution. The absorbance is measured at 525 nm against reagent blank.     

Extractive photometric determination of plutonium(IV) with Aliquat-336 and xylenol orange

A rapid extractive photometric method using Aliquat-336 and xylenol organe for the determination of plutonium(IV) at μg levels has been developed. Quantitative extraction is obtained from ∼4M aqueous HNO₃ medium, affording estimation in the presence of several commonly occurring impurities, viz. iron, uranium, fission products and cladding materials. Effects of acidity, reagent concentration and diverse ions on the estimation have also been invetigated. Unlike the well-known absorptiometric method for determining plutonium(IV) employing Arsenazo III, the procedure presented here tolerates manyfold excesses of uranium(VI) as well as chromium(III), iron(III) and zirconium(IV), which are some of the major contaminants of plutonium during reprocessing.     

Studies on the recovery of Pu(IV) from hydrochloric acid-oxalic acid solutions using an anion exchange method

Sorption of Pu(IV) from hydrochloric acid-oxalic acid solutions has been investigated using different anion exchangers, viz., Dowex-1X4, Amberlite XE-270 (MP) and Amberlyst A-26 (MP) for the recovery of plutonium from plutonium oxalate solutions. Distribution ratios of Pu(IV) for its sorption on these anion exchangers have been determined. The sorption of Pu(IV) from hydrochloric acid solutions decreases drastically in the presence of oxalic acid. However, addition of aluminium chloride enhances the sorption of plutonium in the presence of oxalic acid, indicating the feasibility of recovery of plutonium. Pu(IV) breakthrough capacities have been determined with a 10 ml resin bed of each of these anion exchangers at a flow rate of 60 ml per hour using a solution of Pu(IV) with the composition: 6M HCl+0.05M HNO₃+0.1M H₂C₂O₄+0.5M AlCl₃+100 mg.l^–1 Pu(IV). The 10% Pu(IV) breakthrough capacities for Dowex-1X4, Amberlite XE-270 (MP) and Amberlyst A-26 (MP) are 15.0, 8.9 and 6.2 g of Pu(IV) l^–1 of resin respectively.     

Determination of plutonium and uranium in the same aliquot by potentiometric titration

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. HClO₄. Pu/VI/ formed was reduced to Pu/IV/ with known excess of Fe/II/ and the excess Fe/II/ was titrated with standard K₂Cr₂O₇ to a potentiometric end point. Uranium in the same solution was determined by reduction to U/IV/ with Fe/II/ in conc. H₃PO₄ medium and titrating U/IV/ formed with standard K₂Cr₂O₇ 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.     

An improved method for the potentiometric determination of plutonium using cerium/IV/ as an oxidant

An improved method for the determination of plutonium in an aliquot using cerium/IV/ as an oxidant is reported. Plutonium is oxidized quantitatively to plutonium/VI/ in nitric acid medium by cerium/IV/, the excess of which is chemically destroyed in a single step by hydrochloric acid. Plutonium/VI/ is then reduced to plutonium/IV/ with a known amount of Fe/II/, the excess of which is back titrated potentiometrically with standard dichromate. Results of analysis of 3–5 mg amounts of plutonium in aliquots containing standard plutonium nitrate solution are reliable within 0.2%. Effect of the presence of some relevant foreign ions has been studied. The application of the method for the analysis of mixtures containing various amounts of uranium and plutonium has been examined.     

Effect of excess AgO and EDTA on the redox titration involved in potentiometric determination of plutonium

Attempts to carry out potentiometric determination of plutonium (by AgO-oxidation method) following the determination of thorium (by complexometric EDTA titration) gave positively biased irreproducible values of plutonium. In order to understand the factors leading to the erroneous values of plutonium, the effect of varying amounts of AgO and EDTA on redox [Fe(II)/K₂Cr₂O₇] titration in the medium consisting of 1M H₂SO₄ and 0,4M HNO₃ was studied. When AgO (up to 200 mg) was added in the titration medium and destroyed by sulfamic acid prior to the redox titration, the dichromate tittre value (amount of standard K₂Cr₂O₇ solution equivalent to 1 g of Fe(II) solution) showed negative bias. The bias was found to decrease with increase in time interval between AgO destruction and the redox titration. The presence of EDTA (up to 15 mg) gave positive bias in the titre value. Results on the titre values obtained under different conditions of the aqueous medium indicated the possibility of formation of unstable Ag(II)-sulfamic acid compled, which is probably responsible for the irreproducible values of plutonium.     

怀药中维生素C含量的测定

为建立怀药中维生素C含量直接测定新方法,以pH 2.5硫酸溶液为溶剂,采用紫外分光光度法测定了怀药中维生素C含量.结果表明,维生素C在0～15 μg/mL范围内与吸光度呈良好的线性关系,回归方程为:y=0.060 29 C+0.003 55,r=0.999 9,所选的怀药均含丰富的维生素C,其中怀菊花中高达 51.55...     

SPECTROPHOTOMETRIC DETERMINATION OF TRACE AMOUNTS OF FLUORIDE IN PLUTONIUM

Abstract

A simple and rapid spectrophotometric method for the determination of 10 to 70 μg of fluoride with Eriochrome Cyanine R in up to 10 mg of plutonium has been developed. In this method interference from the plutonium is eliminated by reduction of this element to the tripositive oxidation state with mercaptoacetic acid.