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.
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.
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%.
Authors:G. Relan, A. Dubey, A. Bhanu and S. Vaidyanathan
A derivative spectrophotometric method has been developed for the determination of uranium at mg level in presence of iron in 1M HNO3 medium. Its application was extended to the determination of uranium is magnesium diuranate (Yellow Cake), an input material to the Uranium Conversion Plant. The second derivative absorbance at 408.2 nm was used for its quantification since at this wavelength the absorbance due to iron is negligibly small and that due to uranium is significant. The uranium content was found to be directly porportional to the amplitude at 408.2 nm. It was demonstrated that the impurities present in yellow cake do not interfere. The method is simple, fast, needs no prior separation and enables direct measurement of yellow cake samples which is an important requirement from the point of view of nuclear materials accounting.
Authors:G. Relan, R. Sharma, U. Powar, P. Kalsi and S. Vaidyanathan
A cotrolled potential coulometric method has been developed in 1M HClO4 for the determination of uranium using an electrolysis cell and coulometer. A noteworthy feature of this method is its applicability even in the presence of large excess of calcium, barium and lead, situations where the commonly used coulometric method in 0.5M H2SO4 medium and the well known potentiometric method in H3PO4 medium are not applicable, Results of the determination of uranium in a number of aliquots of synthetic solutions of (U,Ca), (U, Ba) and (U, Pb) showed a precision of the order of 0.2% and the experimental values of uranium content agreed with the expected values within the precision limits. Similar results were obtained with samples of synthetic mixtures of U3O6 and CaF2 powder containing 1–5% U and 95–99% Ca. The method was then successfully used to determine the U-conten of some typical samples of CaF2 slag (containing 1–5% U) generated during the calciothermic reduction of UF4 to U-metal at conversion plants.