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: 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: 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.     

废Pd/C催化剂中钯的回收

研究了从废MC催化剂中得到高回收率粗钯的方法，研究了从粗钯回收高纯度钯的3种方法，提出了1种工艺简单、效果好、成本低、易操作的从废MC催化剂中回收钯的方法。试验表明，本方法适用于实际生产应用。     

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.     

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: 2. Effect of Radiation on Palladium Recovery and Condition of Extraction Systems

Extraction of palladium nitrate complexes from 1-3 M HNO₃ with tri-n-octylamine (TOA) and tricaprylmethylammonium nitrate (Aliquat 336 nitrate) in diethylbenzene under irradiation at a dose of up to 100 W h l^{- 1} is studied. In irradiated extraction systems, the acidity of the aqueous and organic phases decreases and HNO₂ is formed. With increasing radiation dose the degree of Pd recovery decreases by virtue of partial degradation of the organic phase. The radiation effects on the condition of extraction systems are discussed.     

Plutonium Recovery from Nitric Acid Regeneration Solutions Using AXIONIT VPA Vinylpyridinium Anion-Exchange Resins

Radiochemistry - Vinylpyridinium anion-exchange resins AXIONIT VPA-1 and AXIONIT VPA-2, synthesized by AO Axion—Rare and Noble Metals, were tested in plutonium recovery from nitric acid...     

Recovery of Pd from spent fuel: 5. Recovery of Pd from high-level PUREX raffinate

Laboratory experiments were carried out on sorption and electrochemical recovery of Pd from actual high-level PUREX raffinate. The initial solutions were high-level liquid wastes after extraction processing of WWER-1000 spent fuel with a burn-up of about 40 MW (kg U)^?1, cooled for 5–7 years. In sorption recovery with VP-1AP anion-exchange resin, the Pd yield into the eluent was about 90%. After additional refinement by precipitation, the activity of the resulting palladium black sample was no more than 0.8 mCi (g Pd)^?1, and the total decontamination factor was 1.9 × 10⁴.     

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.     

Extraction of Rare-Earth Elements from Nitric Acid Solutions with Ethylenediphosphine Dioxides

Extraction of microamounts of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu from HNO₃ aqueous solutions with ethylenediphosphine dioxides in organic diluents was studied. The effect of the dioxide structure on its extractive power and selectivity was considered. The stoichiometry of extractable solvates was determined.     

Oxidation of Urea with Nitrous Acid in Nitric Acid Solutions

The kinetics of the reaction between urea and HNO₂ in nitric acid solution was studied spectrophotometrically. It was found that, at a constant ionic strength of the solution μ = 2, in the range of the initial concentrations of urea from 0.01 to 0.1 M, HNO₂, from 0.003 to 0.012 M, and hydrogen ions, from 0.1 to 1.5 M, the rate constant of the reaction is described by the equation -d[HNO₂]/dt = k[HNO₂][CO(NH₂)₂][H⁺] · K([H⁺]K +1)⁻¹, where the rate constant k = 15.6±0.3 l mol⁻¹ min⁻¹ and the protonation constant of urea K = 1.38 l mol⁻¹ at 15°C. From the temperature dependence of the reaction rate in the range of 15–35°C, the activation energy was determined to be 61±5 kJ mol⁻¹. The reaction mechanism involving the reaction of nondissociated HNO₂ molecules and protonated urea species NH₂CONH ₃ ⁺ was suggested.__________Translated from Radiokhimiya, Vol. 47, No. 1, 2005, pp. 57–60.Original Russian Text Copyright © 2005 by Dvoeglazov, Marchenko.     

Palladium in Irradiated Fuel. Are There Any Prospects for Recovery and Application?

Published data on the speciation and behavior of Pd in different stages of reprocessing of irradiated fuel from NPPs were analyzed. Various methods for recovering Pd from solutions and solids of different compositions, arising in reprocessing, were described. The Pd sales volumes in the recent decades were reported, and possible industrial and technical applications of Pd were discussed. An opinion is expressed that it is of interest to recover “ reactor-grade” Pd to be used in reprocessing of the waste from radiochemical enterprises (e.g., immobilization of ¹²⁹I and/or TPEs), i.e., in processes where the presence of radioactive nuclide ¹⁰⁷Pd does not matter and exhaustive removal of other fission products is not required.__________Translated from Radiokhimiya, Vol. 47, No. 1, 2005, pp. 3–14.Original Russian Text Copyright © 2005 by Pokhitonov, Romanovskii.     

Recovery of Rare-Earth Elements from Nitric Acid Solutions with a Polymeric Sorbent Impregnated with Diphenyl(dialkylcarbamoylmethyl)phosphine Oxides

The distribution of lanthanides (Ln), including also Y, between aqueous HNO₃ and a microporous styrene-divinylbenzene copolymer impregnated with diphenyl(dialkylcarbamoylmethyl)phosphine oxides (CMPOs) and their -substituted derivatives was studied in relation to the aqueous phase acidity and extractant content in the solid phase. Rare-earth elements pass into the sorbent phase in the form of complexes with the Ln : CMPO ratio of 1 : 2. The Ln distribution factors grow as the HNO₃ concentration in the aqueous phase is increased from 0.1 to 7.0 M.     

Solubility of Radium Nitrate in Nitric Acid Solutions

Radiochemistry - The solubility of radium nitrate in concentrated HNO3 solutions was determined. The radium nitrate solubility decreases from ～1 × 10?3 to ～2 ×...     

Uranyl and Thorium(IV) Sorption from Dilute Nitric Acid Solutions with Dodecavanadic Acid

Sorption of uranyl on dodecavanadic acid proceeds by the ion-exchange mechanism at relatively low metal concentrations in the range (0.8-2.0) ×10^{- 3} M. Sorption of Th(IV) is practically pH-independent over the pH range 1.5-2.5, but depends significantly on the initial Th(IV) concentration. The maximal capacities of DDVA for uranyl and Th(IV) remarkably differ from each other (9 and 6.3 mg-equiv g^{- 1}, respectively). The uranyl compound formed on contacting DDVA with concentrated uranyl nitrate solution was identified by X-ray diffraction as UO₂(VO₃)₂·nH₂O.     

Thermal Stability of Nitric Acid Solutions of Hydrazine Nitrate

Radiochemistry - Thermal stability of hydrazine nitrate (HN) in solutions in 4–12 M HNO3 in the temperature interval 70–150°C was studied. Exothermic reactions accompanied by gas...     

Oxidation of Hydrazine during Evaporation of Nitric Acid Solutions

The processes of hydrazine oxidation with nitric acid on heating and at continuous evaporation were compared. The latter process was performed in a titanium vessel equipped with an external heating chamber and three removable sieve overflow plates. At evaporation, the yield of HN₃ and primarily NH₄NO₃ decreases with increase in the acidity of the bottoms and decrease in the concentration and feeding rate of hydrazine; the presence of plates in the evaporator and their spraying with the reflux decrease the yields of HN₃ and NH₄NO₃ to a still greater extent.     

Extraction of Rare-Earth Elements and Americium from Nitric Acid Solutions with Polyphosphine Oxides

Extraction of HNO₃ and microamounts of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Am from solutions of NH₄NO₃ and HNO₃ with solutions of polyphosphine oxides containing o-oxyphenylenemethylene fragments in dichloroethane was studied. The stoichiometry of the extractable complexes was determined, and the apparent extraction constants were calculated. As the number of phosphoryl groups in the extractant molecule is increased, the extraction of cerium-group lanthanides increases and that of yttrium-group lanthanides decreases.