I. C. Pius

Removal of plutonium and americium from oxalate supernatants by co-precipitation with thorium oxalate

As a part of treatment of low level active waste, co-precipitation of plutonium (Pu) and americium (Am), with thorium oxalate, from oxalate supernatants generated during plutonium oxalate precipitation has been investigated. A simple method for the simultaneous removal of both Pu and Am from oxalate supernatants could be developed. This simple process achieves incorporation of these alpha active nuclides into small volumes of solid matrix from large volumes of aqueous waste.

Studies on sorption of plutonium on inorganic ion exchangers from sodium carbonate medium

Sorption of Pu(IV) from sodium carbonate medium has been investigated by using three inorganic ion exchangers, viz. alumina, silica gel and hydrous titanium oxide (HTO). Distribution ratios (D) of Pu(IV) for its sorption on these ion exchangers have been determined. The values are 700, 103 and 104 for alumina, silica gel and hydrous titanium oxide, respectively, from 0.1M sodium carbonate medium. The high distribution ratios indicate their suitability for the removal of Pu(IV) from sodium carbonate waste streams. Pu(IV) breakthrough capacities have been determined with 5 ml bed at a flow rate of 30 ml per hour. The 10% Pu(IV) breakthough capacities for alumina and silica gel are 3 g l−1 and 14 g l−1, respectively. The capacity of HTO is 60 g of Pu(IV) per liter of exchanger at 4% Pu(IV) breakthrough.

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.

The behaviour of plutonium in aqueous basic media

Behaviour of Pu(IV) and Pu(VI) in basic media has been investigated by studying their stabilities and quantitative determination by spectrophotometry. Beers law was found to be obeyed in the range of 1·10−3 to 5·10−3 M Pu(IV) at 485 nm peak with a molar absorption coefficient of 95M−1· cm−1 in sodium carbonate medium. In case of Pu(VI), in the same medium Beers law was obeyed in the concentration range of 2·10−3 to 1·10−2M at 550 nm with a molar absorption coefficient of 50M−1·cm−1. Distribution ratios of Pu(IV) and Pu(VI) for their sorption on Al2O3 and Amberlyst A-26 (MP) resin from bicarbonate and carbonate media have been determined. High distribution ratios obtained indicate the feasibility of decreasing the plutonium content of basic carbonate streams in reprocessing. 10% breakthrough capacities for Pu(IV) and Pu(VI) with these exchangers during column operations have also been determined.

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.

Studies on the sorption of Pu(IV) on alumina microspheres from nitric acid-oxalic acid solutions

Sorption of Pu(IV) on alumina microspheres prepared by the sol-gel procedure has been investigated for the recovery of plutonium from nitric acid-oxalic acid solutions. Distribution ratio for Pu(IV) between alumina microspheres and nitric acid-oxalic acid have been determined. The influence of the mode of preparation and heat treatment of these microspheres, on the sorption of Pu(IV) have been investigated. Pu(IV) breakthrough capacities have been determined using a 5 ml bed of alumina with solutions of Pu(IV) in 1M HNO3+0.05M H2C2O4 and 0.5M HNO3+0.05M H2C2O4. The elution behavior of Pu(IV) loaded on these microspheres were studied using nitric acid solutions containing different oxidising and reducing agents. Investigations were also carried out to fix the activity in the alumina matrix by heat treatment.

Studies on sorption of plutonium from carbonate medium on polyacrylhydroxamic acid resin

Polyacrylhydroxamic acid resin synthesized by functionalization of polyacrylamide with hydroxylamine has been investigated for the sorption of plutonium(IV) from carbonate medium, aiming at its application for the removal of plutonium from alkali wash effluent generated during purification of TBP in PUREX process. Batch experiments have been carried out to determine distribution coefficient of plutonium(IV) between this exchanger and various compositions of carbonate medium. Effect of the concentration of sodium carbonate, sodium bicarbonate and pH of the solution on the distribution coefficient have been studied to optimize the conditions for the uptake of Pu(IV) by this exchanger. Column experiments were carried out to determine the practical capacity of the exchanger for plutonium. Elution studies were also carried out to recover the loaded plutonium from the ion exchange column The exchanger displayed good exchange capacity for Pu(IV) from feed solution simulating the conditions of carbonate wash effluent generated in PUREX process. The exchanger also exhibited fast elution of Pu, suggesting the feasibility of using it for the recovery of Pu from carbonate based wash effluent.

Extraction of plutonium(IV) from oxalic acid-nitric acid solutions by Aliquat-336

The extraction of Pu(IV) from oxalic acid-nitric acid mixtures has been investigated using a liquid anion exchanger, Aliquat-336, in xylene. The presence of oxalic acid is known to have adverse effects on the extraction of Pu(IV) by Aliquat-336. The use of cations, Al(III), Fe(III) or Zr(IV) was explored to overcome the effect of oxalic acid on Pu(IV) extraction. The data obtained reveal that Pu(IV) is quantitatively extracted by Aliquat-336, even in the presence of oxalic acid, when Al(III), Fe(III) or Zr(IV) is added. The extracted Pu(IV) can be back-extracted using aqueous ammonium carbonate.

Recovery of plutonium from phosphate containing aqueous analytical waste solutions using macroporous anion exchange resin

Distribution ratios of Pu(IV) between 7.5M HNO3+0.75M H3PO4+0.3M H2SO4 media and a macroporous anion-exchange resin Amberlyst A-26 (MP) increased from 40 to 250 when 1M aluminium nitrate was added to the aqueous medium. When 1M ferric nitrate was used in place of aluminium nitrate the distribution ratio further increased to 850. The 10% Pu(IV) breakthrough capacities with a 5 ml bed resin column, using synthetic feed solutions containing 1M aluminium nitrate, were 1.4 g l−1, 3.2 g l−1 at flow rates of 30 ml per hour and 10 ml per hour, respectively. The corresponding 10% Pu(IV) breakthrough capacities in the presence of 1M ferric nitrate were 8.5 g l−1 and 12.8 g l−1. More than 97% of plutonium could be recovered from actual analytical phosphate waste solutions.

Sorption of Pu(IV) on Aliquat-336 impregnated silica-gel

A new ion exchange material prepared by impregnating Aliquat-336 on silica-gel has been investigated for the recovery of plutonium from nitric-oxalic acid solutions. The distribution ratio of Pu(IV) was studied at various concentrations of nitric and oxalic acids. The presence of Al(III) and Fe(III) in the solution, enhances the uptake of Pu(IV). Pu(IV) breakthrough capacities (btc) have been determined using 2.5 ml bed of the ion exchange material column in the absence and the presence of Al(III) and Fe(III) nitrate. The elution behavior of Pu(IV) was also studied using nitric acid solutions containing reducing agents. More than 90% of plutonium could be recovered from nitric-oxalic acid solutions.