R. K. Rastogi

Stabilisation of tetravalent cerium in perchloric acid medium and measurement of the stability constants of its fluoride complexes using ion selective potentiometry

The stability constants of the fluoride complexes of cerium(IV) in 1 M (HClO(4), NaClO(4)) medium have been measured potentiometrically using a fluoride ion-selective electrode. Quantitative oxidation of cerium to its tetravalent state and its stabilisation in the perchlorate medium were accomplished by oxidation with AgO followed by quick addition of a known amount of fluoride ion. This procedure ensures stability of the oxidation state and prevents hydrolysis and polymerisation of Ce(IV). Logarithms of the average values of beta(1), beta(2), beta(3) and beta(4) were estimated to be 7.57+/-0.04, 14.50+/-0.03, 20.13+/-0.37 and 24.14+/-0.10 respectively.

Modified pyrohydrolysis apparatus for the separation of fluorine and chlorine trace impurities from nuclear fuel samples for quality control analysis

A quartz pyrohydrolysis apparatus designed for the safe handling of pyrophoric carbide nuclear fuel samples while separating C1 and F trace impurities for quality control analysis is described. It has several advantages over the commonly used pyrohydrolysis apparatus. Performance of the apparatus during routine analysis of a large number of nuclear fuel samples has been found to be quite satisfactory.

Determination of sulphur species in the presence of common anions with indirect measurement of sulphide by ion chromatography (IC)

ABSTRACT A two-step ion chromatographic method for the determination of sulphur containing anions with indirect measurement of sulphide in the presence of common anions in tannery wastewater has been developed. In the first step, species like , , and SCN− are separated isocratically on an anion exchange separator column using the mobile phase mixture solution and quantified by conductivity detection. The total sulphate equivalent of all these species is then calculated. In the second step, in another aliquot of the sample, all the sulphur species are converted into sulphate using ammoniacal hydrogen peroxide and quantified as sulphate. The amount of sulphide is then arrived at by subtracting the total sulphate equivalent obtained in the first stage from the total sulphate obtained in the second step. The detection limits for all the ions are less than 0.5 ppm with reproducibility of better than 10%.

Microdetermination of fluoride by spectrophotometry of arsenazo(III)-complex of Zr back-extracted from htta in benzene

A spectrophotometric method for the determination of trace amounts of fluoride in aqueous solution is developed. It is based on the back extraction of Zr(IV) from its thenoyltrifluoroacetonate complex in benzene by aqueous F− followed by the development of Zr-arsenazo(III) coloured complex and the measurement of the absorbance at 665 nm. Optimum conditions and effect of interfering ions are studied. The coefficients of variation obtained are 1.5% and 2.2% in 11 determination at the F− concentration level of 10.0 μg/ml and 1.6 μg/ml. An excess of Al(III) is used for decomplexing Zr-fluoride prior to the colour formation if the fluoride amount is high. The method is useful for the determination of trace impurities of fluoride in nuclear fuel after separating fluoride from fuel matrix by pyrohydrolysis.

Study on the extraction of U(IV) relevant to PUREX process

Extraction of U(IV) by an organic phase containing 30% tri-n-butyl phosphate (TBP) in dodecane from aqueous nitric acid solution containing large amount of U(VI), relevant to nuclear fuel reprocessing by PUREX process, was studied. While acquiring distribution data, an argon atmosphere was maintained. A potentiometric method was used for the determination of U(IV) in the two phases after equilibration. Hydrazine used as stabiliser of U(IV) in the stock solution was destroyed and sulphamic acid was added just before equilibration to avoid the interference due to hydrazine in the subsequent determination of U(IV). Uranium(IV) distribution data between 30% TBP in dodecane and aqueous solution of uranium(VI) and nitric acid of varying concentrations have been presented and compared with available literature data.

DETERMINATION OF FLUORIDE BY SPECTROPHOTOMETRY OF ARSENAZO(III) COMPLEX OF THE BACK-EXTRACTED Th(IV)

A method based on the back-extraction of Th(IV) from its TTA complex in benzene by aqueous F− followed by spectrophotometric measurement of Th(IV), for the determination of fluoride has been developed. The coefficients of variation obtained are 2.4% and 1.4% in 11 determinations at F− concentration levels of 1.0 μg ml−1, respectively.

Determination of fluoride by radiometric assay of181Hf back-extracted from HTTA in benzene

Determination of fluoride at trace level is important for the specification analysis of nuclear fuel samples. This is generally accomplished by pyrohydrolytic separation followed by ion selective electrode potentiometry. In the present work, a method has been developed for the determination of fluoride by radiometric assay of181Hf back-extracted from thenoyltrifluoracetone (HTTA) in benzene.181Hf back-extracted is proportional to the concentration of fluoride.

Separation of thorium from uranium product at the tail end of thorium fuel reprocessing using macroporous cation-exchange resin

Abstract The utility of macroporous cation-exchange resins for the separation of uranium from thorium (relevant to the final purification of the product uranium after reprocessing of the thorium breeder fuel) was examined. Two such cation-exchange resins were studied and compared with a previously used gel-type resin. Batch experiments and column experiments were performed to generate equilibrium data and to optimize the procedure for the separation of U from Th under process conditions. Recovery and purity of the final product were the same while loading and washing rates were much higher (120 mL/h) than those used for gel-type resins (40 mL/h). Much higher throughput was achieved without losing product quality when macroporous resins were used instead of the gel-type resin.

Anion exchange separation and determination of yttrium in uranium oxide — Yttrium oxide mixture

A procedure has been developed for quantitative separation of yttrium from uranium by anion exchange from nearly saturated NH4Cl solution in 0–2N HCl medium. Apparently no organic matter is leached out during the separation as yttrium could be determined by EDTA titration without resorting to fuming with perchloric acid before titration. The precision obtained in the analysis of yttrium in a mixture containing about 12 mg of yttrium and about 300 mg of uranium was ±0.3% (27 determinations).

ON THE USE OF HYDROGEN PEROXIDE AS A MASKING AGENT FOR THE DETERMINATION OF YTTRIUM IN URANIUM OXIDE - YTTRIUM OXIDE MIXTURE

Use of hydrogen peroxide as a masking agent for uranium during the EDTA titration of yttrium in an yttrium-uranium mixture containing large amounts of uranium has been investigated. High acetate ion concentration was necessary to keep the peroxy complex of uranium in solution during the titration. It has been observed that upto 500 mg of uranium could be tolerated in the determination of yttrium with 0.5 ml of 30% hydrogen peroxide in {lM acetate medium. The precision and accuracy of the method based on 16 determinations of yttrium at 6–16 mg level in presence of 300 mg uranium has been found to be ±0.2%.