V.K. Rao

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.

Interaction of humic acid with Plutonium/III/

The stability constants of the complex of Pu/III/ with a humic acid at pH 2.9 and 5.0 were measured using solvent-extraction technique. The organic extractant was dinonyl naphthalene sulphonic acid in sodium form /NaD/ in benzene while the humate aqueous phase had a constant ionic strength of 0.5M /NaClO4/. The total carboxylate capacity of the humic acid was determined by direct potentiometric titration to be 6.201 Meq g−1. The apparent pKa increased as the degree of ionization /α/ increased. The 1g β1 values of the complex of Pu/III/ with humic acid have been determined to be 2.8 and 3.11 at pH 2.9 and 5.0, respectively.

Studies on the adsorption of plutonium (IV) on alumina from phosphoric acid-nitric acid solution

Results of experiments on the adsorption of plutonium (IV) on alumina and their application to the recovery of plutonium from analytical waste solutions containing phosphoric-nitric acid are reported. Distribution ratios of plutonium (IV) between alumina and solutions containing varying concentrations of phosphoric acid and nitric acid are determined. The influence of various ions like UO22+, Fe3+, MoO42−, VO2+ and SO42− on the distribution ratio is evaluated. Saturation values of adsorption of plutonium (IV) on alumina and optimum conditions for loading and elution of plutonium on a column packed with alumina are described.

Hydrolysis and carboxylate complexation of trivalent americium

Abstract Hydrolysis and complcxation of trivalent americium in the presence of acetic acid and tartaric acid have been studied by solvent extraction. It has been found that in basic solutions (pH 8.0), while hydrolysis of the metal ion predominates in the presence of acetic acid, complexation by the chelating ligand suppresses hydrolysis to some extent. The stability constants for the formation of AmL 2+ (acetate) and AmL 1+ and AmL 2 1− (tartarate) have been determined and the data used for computing the first hydrolysis constant (K 1 *) of Am(III). Using experimentally determined β 1 and K 1 * values, the speciation diagrams for Am(III) in acidic (pH 4.0) and neutral solutions have been deduced.

Studies on the dissolution of carbide fuels

The dissolution of carbide fuels was tried with the aid of various oxidants like H2O2, NaBiO3, (NH4)2Ce(NO3)6, (NH4)2S2O8, and AgO in nitric acid medium. During the dissolution, the carbon dioxide liberated has been measured. Among the oxidants studied, H2O2 and NaBiO3 appeared to be more effective for dissolution of carbides. 200–300 mg of sintered uranium carbide sample dissolved within 15 minutes in the presence of oxidants H2O2 or NaBiO3. Mixed carbide sample (∼70%) was dissolved within 30 min, whereas plutonium carbide required more than one hour. From the resulting solutions uranium and plutonium could be determined by conventional redox methods. More than 97% of plutonium could be recovered and purified from the resulting carbide solutions by conventionally used anion exchange method.

Absolute yields of 99Mo and 111Ag in the reactor neutron induced fission of 238U

Abstract The absolute fission yields of 99Mo and 111Ag have been measured in the reactor neutron induced fission of depleted uranium employing a fission track-cum-radiochemical technique. The absolute disintegrations were determined from beta decay and Ge(Li) gamma spectrometry. The total number of fissions were measured by fission track registration on lexan solid state track detector immersed in fissile material solution. The yields for99Mo and 111Ag were found to be (6.27 ± 0.30)% and (0.046 ± 0.002)% respectively. The results are compared with the published data and the merits of the present method have been discussed.

A radiochemical investigation on the existence of polyneutron nuclei in the thermal neutron fission of 235U

Abstract A radiochemical search for polyneutron species X n has been made in the thermal neutron fission of 235 U in the core of the swimming pool reactor, APSARA at Trombay. The study has been made using two probes viz. Pb and Rb using nuclear reactions of the type ( X n , Y. n ) where X = 8–16. It is concluded that if bound polyneutrons exist, they are not emitted in the thermal neutron fission of 235 U with a yield of more than ∼10 −12 /fission.

Separation of heavier rare earths from neutron irradiated uranium targets

A radiochemical method is described for the separation of heavier rare earths from the fission of uranium. The method is particularly suitable for the separation of low yield (10−5%–10−7%), highly asymmetric rare earth fission products viz.179,177Lu,175Yb,173Tm,172,171Er,167Ho and161,160Tb in the neutron induced fission of natural and depleted uranium targets. Additional separation steps have been incorporated for decontamination from239Np (an activation product) and93-90Y (a high fission-yield product) which show similar chemical behaviour to rare earths. Separation of individual rare earths is achieved by a cation exchange method performed at 80°C by elution with α-hydroxyisobutyric acid (α-HIBA).

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.

A gamma-monitoring assembly for the analysis of fission products in reprocessing streams

Abstract The design, fabrication, and operational details of a gamma-monitoring assembly consisting of a movable shielded NaI(Tl) detector, a stainless-steel flow cell, a remotely operated aluminium disc with lead absorbers, and an electrical readout system is described. The system is useful for continuous monitoring of fuel-reprocessing streams for gross as well as individual fission-product activities. Gross activities in the range 5 mCi/l to 15 Ci/l can be monitored continuously with an accuracy of 10–20%. Mixtures of two or three of the major fission products 95Zr95Nb, 106Ru(106Rh), 137Cs(137m)Ba), 144Ce(144Pr), commonly encountered in long-cooled irradiated fuel, can also be analysed within an uncertainty of 15–20%.