Study of Extraction of Palladium from Nitric Acid Solutions with Nitrogen-Containing Compounds,as Applied to Recovery of Fission Palladium from Spent Nuclear Fuel of Nuclear Power Plants: 1. Extraction and Backwashing Conditions

Extractive power of high-molecular-weight amines and quarternary ammonium bases (QABs) of various structures in various aliphatic and aromatic diluents is studied with respect to recovery of palladium nitrate complexes from nitric acid solutions. The effects of pH of the aqueous phase, the contact time, and temperature on the extraction parameters were studied with selected (optimal) extractants (tri-n-octylamine and tricaprylmethylammonium nitrate) in benzene. The composition of extracted complexes was determined to be a monosolvate in the case of the QAB and a disolvate for the tertiary amine. Palladium is efficiently backwashed with concentrated HNO₃ and aminoacetic acid at elevated temperature. The solubility of amines and QABs in aqueous solutions is briefly reviewed.     

Study of Extraction of Palladium from Nitric Acid Solutions with Nitrogen-Containing Compounds,as Applied to Recovery of Fission Palladium from Spent Nuclear Fuel of Nuclear Power Plants: 3. Optimization of Extraction Process for Palladium Recovery and Refining

An extraction process for recovery of fission Pd is proposed. The process parameters are optimized with simulated high-level liquid radioactive waste from nuclear power plants using tri-n-octylamine (TOA) and tricaprylmethylammonium nitrate (Aliquat 336 nitrate) as extractants. The degree of Pd decontamination from fission and corrosion products is estimated and the major interfering components are determined.     

Recovery of Pd from Spent Fuel: 1. Electrochemical Recovery of Palladium from Nitric Acid Solutions

The rate of cathodic deposition of palladium from nitrate solutions at a platinum electrode and the current efficiency of the process were studied as influenced by the concentrations of nitric acid, NaNO₃, U, and other admixtures. In the range of potential E from +0.5 to +0.25 V, the rate of Pd deposition from 1 M HNO₃ solution was 0.7–0.9 mg cm⁻² at current efficiency of about 70%. The degree of palladium recovery by cathodic deposition is more than 99% with the coefficient of separation from α- and β-emitting nuclides of 10²–10³.__________Translated from Radiokhimiya, Vol. 47, No. 4, 2005, pp. 334–338.Original Russian Text Copyright © 2005 by Kirshin, Pokhitonov.     

Recovery of Pd from Spent Fuel: 2. Sorption Recovery of Pd from Nitric Acid Solutions on Anion-Exchange Resins

Recovery of Pd from nitric acid solutions on various anion-exchange resins is studied. The effects of the HNO₃ concentration, temperature, and aminoacetic acid on the desorption of Pd are examined. Results of the experiments on Pd recovery from actual solutions from spent fuel reprocessing are reported.__________Translated from Radiokhimiya, Vol. 47, No. 4, 2005, pp. 339–342.Original Russian Text Copyright © 2005 by Korolev, Pokhitonov, Gelis, Milyutin.     

Recovery of Pd from Spent Fuel: 3. Recovery of Pd from Nitric Acid Solutions Using Carbamoyl Phosphine Oxides

Extraction and sorption recovery of Pd from nitric acid solutions with extractants containing carbamoyl phosphine oxides (CMPO) was studied. The Pd distribution coefficients under different extraction conditions were determined. The possibility of Pd recovery in the course of spent nuclear fuel processing was demonstrated. A number of solid extractants composed of carbamoyl phosphine oxides and inert matrices (styrene-divinylbenzene polymer and silica gel) were tested. The Pd distribution coefficients in the course of sorption and desorption under the static and dynamic conditions were measured.__________Translated from Radiokhimiya, Vol. 47, No. 4, 2005, pp. 343–346.Original Russian Text Copyright © 2005 by Zaitsev, Kvasnitskii, Korolev, Babain, Pokhitonov.     

Recovery of Pd from Spent Fuel: 4. Precipitation of Pd from Nitric Acid Solutions with Hydrazine and CO

Precipitation of palladium with hydrazine and CO from nitric acid solutions simulating process solutions formed in regeneration of spent nuclear fuel was studied. The influence of various factors on the degree of palladium recovery was studied. From 1.0–4.0 M HNO₃ solutions, 50–90 and 70–98% of Pd is precipitated with hydrazine and CO, respectively. Palladium recovery from simulated and real solutions formed in processing of spent nuclear fuel was studied. The decontamination factor of palladium with respect to most of elements including radionuclides was 10²–10³.__________Translated from Radiokhimiya, Vol. 47, No. 4, 2005, pp. 347–350.Original Russian Text Copyright © 2005 by Gevirts, Zelentsova, Kozlov, Kolobov, and Pokhitonov.     

Extraction of Rare-Earth Elements from Nitric Acid Solutions with Bidentate Phosphoryl-containing Compounds and Their Mixtures

Extraction of microamounts of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu from HNO₃ solutions with neutral bidentate phosphoryl-containing compounds was studied. Extraction with tetraphenylmethylenediphosphine dioxide increases in going from Lu to La, and extraction with methyleneoxyphenyldiphosphine dioxides increases in the opposite direction. The anomalous aryl strengthening effect varies in the same direction. Extraction with mixtures of diphosphine dioxides allows efficient concentration of the sum of rare-earth elements from nitric acid solutions.     

Radiation-Chemical Behavior of TBP in Hydrocarbon and Chlorohydrocarbon Diluents under Conditions of Reprocessing of Spent Fuel from Nuclear Power Plants

Experiments were performed for comparative assessment of the effect of ionizing radiation on the service characteristics of 30% TBP solutions in various diluents: hexachlorobutadiene (HCBD), mixtures of n-paraffins (RED diluent), and fraction of naphthenic hydrocarbons (RZh diluent). The following main parameters were chosen for comparative assessment of the quality of irradiated extractant solutions: composition and behavior of diluent radiolysis products, effect of diluents on the TBP radiolysis, and aggregative stability of emulsions in the main operations of the extraction cycle. The service life of the extraction mixtures was estimated from variation of the above parameters with the irradiation dose. Principles for choosing solvents with increased service life under irradiation were substantiated.     

Extraction of Am(III) and Eu(III) from Nitric Acid Solutions with Bidentate Neutral Organophosphorus Compounds

Extraction of HNO₃ and microamounts of Am and Eu from nitric acid solutions with solutions of bidentate butyl (phosphorylmethyl)phenylphosphinates R₂P(O)CH₂P(O)Ph(OBu) [R = octyl (I), phenyl (II), p-tolyl (III), p-anisyl (IV)] in 1,2-dichloroethane was studied. The stoichiometry of the extractable complexes was determined, and the apparent extraction constants were calculated. The extractive power of the reagents studied toward HNO₃ increases in the order II < III < IV < I, and toward Am(III), in the order I < II < III < IV.     

Effect of TBP on Extraction of REE and TPE from Nitric Acid Solutions with Dibutylphosphoric Acid and Its Zirconium Salt

Solvent effect on extraction of REE and TPE with dibutylphosphoric acid is studied. Over the HNO₃ concentration range 0.1-0.5 M, HDBP is a good extractant for REE and TPE, whereas addition of TBP suppresses the extraction. The effect of excess HDBP is similar to the previously observed effect of TBP on extraction of REE. Evidently, free HDBP, like TBP, can enter the solvation shell of a lanthanide with formation of fairly complex, probably polymeric species.     

Extraction of Scandium from Various Media with Triisoamyl Phosphate: 1. Extraction of Sc and Impurity Metals from Aqueous Nitric Acid Solutions

The main features of extraction of Sc from aqueous nitric acid solutions with triisoamyl phosphate (TIAP) were studied. It was shown that Sc passes into the organic phase in the form of Sc(NO₃)₃·3TIAP. The extraction isotherms of Sc from its aqueous HNO₃ solutions and from those containing salting-out agents (LiNO₃, NH₄NO₃) with TIAP in dodecane were obtained. The distribution factor of Sc was studied in relation to the concentrations of TIAP, salting-out agent, and HNO₃. The extraction of Sc and impurity metals (Zr, Th, REE) with TIAP was studied at widely varied HNO₃ concentration in the aqueous phase. The separation factors of Sc from impurity metals were determined.     

Separation of REE(III) and Am(III) by Extraction with Compounds of Zirconium and Dibutyl Phosphoric Acid from Solutions of Nitric and Hydrochloric Acids

Radiochemistry - The behavior of rare-earth elements (REE) and americium during their extraction with compounds of zirconium and dibutyl phosphoric acid (DBPA) in various solvents from solutions of...     

Radiation-Chemical Resistance of Anion Exchangers and Safety of Sorption Processes in Nitric Acid Solutions: II. Study of Gas Liberation in Systems Ion Exchanger-HNO3

Gas liberation in systems ion exchanger-nitric acid solution in open and closed vessels under the action of elevated temperature and ionizing radiation is studied. Preliminary data on the detonation properties of VP-1AP anion-exchange resin are given. No considerable gas liberation is observed in the system in the presence of the liquid phase, but explosive thermochemical degradation of the sorbent can occur as a result of drying of the sorbent phase. Elevated temperature and ionizing radiation increase the probability of this process.     

Synthesis of New Crystalline Pu(V) Compounds from Solutions: VII. Synthesis and Study of MPuO2C2O4 · nH2O with M = NH4 and Cs

Double monooxalates MPuO₂C₂O₄ · nH₂O with NH ₄ ⁺ and Cs⁺ ions in the outer sphere were isolated from weakly acidic aqueous solutions of Pu(V). The unit cell parameters of these compounds were determined. The ammonium salt is isostructural to its neptunyl(V) analog; its structure is characterized by the monodentate cation-cation interaction of plutonyl(V) ions. Cesium plutonyl(V) salt isolated from a solution is not isostructural to the neptunyl(V) compound and is easily dehydrated at room temperature to form tetrahydrate, which transforms to dihydrate at 110°C. The latter compound, according to the IR spectra, can have a network system of cation-cation bonds involving PuO ₂ ⁺ . __________ Translated from Radiokhimiya, Vol. 47, No. 5, 2005, pp. 427–430. Original Russian Text Copyright ? 2005 by Bessonov, Krot, Grigor'ev, Makarenkov.     

Synthesis of New Crystalline Pu(V) Compounds from Solutions: III. Synthesis and Study of NaPuO2C2O4·nH2O with n = 3, 1, and 0

NaPuO₂C₂O₄·3H₂O was isolated from a freshly prepared oxalate solution of Pu(VI) by reduction with a stoichiometric amount of hydrazine hydrate. Heating of the compound results in its stepwise dehydration with successive formation of the monohydrate and anhydrous salt. According to powder X-ray patterns, NaPuO₂C₂O₄·nH₂O (n = 3, 4) is isostructural to the corresponding analogs NaNpO₂C₂O₄·nH₂O. The unit cell parameters of NaNpO₂C₂O₄·H₂O and NaPuO₂C₂O₄·nH₂O (n = 3, 1) were determined. The results of the X-ray analysis and the electronic and IR spectra of the neptunyl(V) and plutonyl(V) crystalline compounds suggest the presence of cation-cation bonds in NaPuO₂C₂O₄·nH₂O (n = 1, 0). __________ Translated from Radiokhimiya, Vol. 47, No. 2, 2005, pp. 105–109. Original Russian Text Copyright ? 2005 by Krot, Bessonov, Grigor’ev, Charushnikova, Makarenkov.