S. K. Patil

CHEMISTRY OF NUCLEAR FUEL REPROCESSING: CURRENT STATUS

Current status on the chemical aspects of nuclear fuel reprocessing is presented with special emphasis on the Purex process which continues to be the process of choice for the last four decades. Better decontamination from fission products, new methods for uraniumplutonium partitioning and removal of actinides from high active waste are challenging areas in process chemistry. The development work on TRUEX and DIAMEX process for treating high active waste is briefly described. An overview of pyrochemical processes, which are important for Integral Fast Reactor Concept, is presented.

The effect of temperature on the extraction of plutonium(IV) from nitric acid by tri-n-butyl phosphate

Abstract The extraction of Pu(VI) from varying concentration of nitric acid into TBP in dodecane was studied at different temperatures in the range 20–60°C. From the distribution coefficient data, the enthalpy changes for the extraction of Pu(VI) under different conditions were determined. All the data obtained showed that the extraction of Pu(VI) from nitric acid into TBP is exothermic in nature. An attempt was made to evaluate the thermodynamic free energy and entropy changes.

The effect of temperature on the extraction of uranium(VI) from nitric acid by tri-n-butyl-phosphate

Abstract The extraction of Pu(VI) from varying concentration of nitric acid into TBP in dodecane was studied at different temperatures in the range 20–60°C. From the distribution coefficient data, the enthalpy changes for the extraction of Pu(VI) under different conditions were determined. All the data obtained showed that the extraction of Pu(VI) from nitric acid into TBP is exothermic in nature. An attempt was made to evaluate the thermodynamic free energy and entropy changes.

Complexing of tetravalent plutonium in aqueous solutions

Abstract Complex formation by tetravalent plutonium at I = 2 and [H + ] = 2 M, has been studied by solvent extraction methods using vanadium(V) to eliminate the possibility of a change in the oxidation state of Pu(IV) during the experiment or complexing of Pu(IV) by the holding oxidant itself. Sulphate complexing of Pu(IV) has been studied using three extractants, viz. thenoyltrifluoroacetone, dinoylnaphthalene sulphonic acid and tri- n -butylphosphate, and nitrate, chloride and fluoride complexing of Pu(IV) has been studied using the thenoyltrifluoroacetone extraction method.

Some studies on the TBP extraction of actinides

Abstract Distribution coefficient data for tetravalent Th, U, Np and Pu and hexavalent U, Np and Pu were obtained at different temperatures in the range 10°–60°C for 3·0M nitric acid and 30% TBP in xylene. From these data the enthalpy changes associated with the extraction of the ions were determined. An attempt was also made to estimate the corresponding free energy and entropy changes.

THE EFFECT OF TEMPERATURE ON THE EXTRACTION OF PLUTONIUM(IV) BY TRI‐N‐BUTYL PHOSPHATE

Abstract Distribution coefficient data for Pu(IV) were obtained at different temperatures in the range 10–60°C for varying concentrations of nitric acid and TBP in dodecane. From these data the enthalpy change for extraction of Pu(IV) was determined. An attempt was also made to calculate the free energy and entropy changes associated with the extraction of Pu(IV).

Studies on the HTTA extraction of tetravalent actinides

The data on the extraction of Np(IV) and Pu(IV) from aqueous perchloric and nitric acid into benzene solution of thenoyl-trifluoro-acetone (HTTA) have been obtained at different temperatures. From these data the equilibrium constant for their extraction and the values of enthalpy for the extraction of Np(IV) and Pu(IV) were calculated. The absorption spectra of HTTA extracts containing Th(IV), U(IV), Np(IV) and Pu(IV) have been recorded to explore their analytical applications.

The complexing of Np(V) by some inorganic ligands

Abstract The complexing of Np(V) with Cl − , F − , NO 3 − , NO 2 − , SO 4 −2 , SCN − and IO 3 − has been studied by the solvent extraction method using Dinonylnaphthalene sulphonic acid (DNNS) as the extractant. An attempt is made to establish existence of the complexes by solvent extraction and spectrophotometric studies.

Sulphate and fluoride complexing of U(VI), Np(VI) and Pu(VI)

Abstract The complex formation of U(VI), Np(VI) and Pu(VI) with sulphate and fluoride ions was studied in HClO4H2SO4 and HClO4HF solutions respectively at an ionic strength of 2·0 and [H+] = 2·0 M by the distribution method employing the liquid cation exchanger dinonyl naphthalene sulphonic acid as the extractant. An attempt was made to explain the order of the stability constant values obtained.

A spectrophotometric method for the determination of neptunium and plutonium in process solutions

A method is described for the determination of neptunium and plutonium in process solutions. This involves the separation of these elements followed by their spectrophotometric determination as Arsenazo III complexes. Neptunium(IV) and plutonium(IV) are separated using TTA extraction method and the separated Np(IV) and Pu(IV) are then determined as their Arzenazo III complexes in 5M HNO3. A few solutions obtained by dissolving irradiated fuels were analysed for plutonium and neptunium using this method and the results were compared with those obtained by other methods. An attempt was made to use Arsenazo III to determine uranium in the plant solutions.