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Reprocessing of high plutonium content spent nuclear fuel from fast reactors results in the generation of lean organic solution containing considerably high amount of di-butyl phosphoric acid. Use of sodium carbonate as wash reagent has constraints in the view point of process operation. In this context, an alternative method for the wash of radiolytically degraded 1.1 M TBP/n-dodecane was proposed. Studies indicated that that the use of 1.5 M of hydrazine carbonate was effective for the treatment of solvent degraded up to 300 kGy and the product obtained were comparable to the fresh solvent. [ABSTRACT FROM AUTHOR]

The diethylenetriamine (DETA) organic moiety was anchored covalently on the surface of silica gel to obtain a surface-modified adsorbent abbreviated as Si-DETA. The adsorbent was characterized by FT-IR, Raman spectroscopy, thermogravimetry, scanning electron microscopy, and energy dispersive X-ray analysis. The adsorption behavior of uranium on Si-DETA was studied as a function of pH of the aqueous phase, duration of contact time, and concentration of uranium in the aqueous phase. The kinetics of uranium adsorption on Si-DETA was fitted with pseudo-first order and pseudo-second order kinetic models. The adsorption isotherm obtained from uranium loading was fitted into popular models such as Langmuir, Freundlich, Temkin, and D-R adsorption isotherms. The statistics of fitting revealed that the Langmuir adsorption model obeyed the adsorption data. The performance of the adsorbent was also evaluated under dynamic conditions by passing feed solution containing uranium in a buffered solution and seawater into a fixed bed column containing Si-DETA. The results were compared with those obtained in a batch mode. The study showed the possibility of using Si-DETA for the separation and recovery of uranium from aqueous waste and seawater. [ABSTRACT FROM AUTHOR]

The radiolytic stability of aqueous solutions containing two different bis-1,2,4-triazines was studied under static gamma irradiation. Sulphophenyl derivatives of bis-1,2,4- triazinyl pyridine (SO3-Ph-BTP) and bis-1,2,4-triazinylbipyridine (SO3-Ph-BTBP) were dissolved in 0.1 M and 1 M HNO3 solutions and the impact of gamma irradiation was assessed by the measurement of distribution ratios of Am(III) and Eu(III) using irradiated samples. The results were compared for two different organic solvents containing N,N,N',N'-tetraoctyldiglycolamide (TODGA) or N,N-didodecyl-N',N'-dioctyldiglycolamide (D3DODGA). The separation efficiency of all the systems remained unchanged when the absorbed dose was 100 kGy, and gradually decreased at 200 kGy and 500 kGy. The radiolytic degradation was more apparent for SO3-Ph-BTBP in comparison to SO3-Ph-BTP at higher acidity. The degradation of sulphonate groups in the molecules was evidenced in ATR-FTIR spectral studies. [ABSTRACT FROM AUTHOR]

The selective partitioning of trivalent actinides (An(III)) from high-level liquid waste (HLLW) is considered as an essential step in the management of spent nuclear fuel. The i-SANEX process for the separation of An(III) from the co-existing lanthanides (Ln(III)) in 4 M nitric acid solution and simulated HLLW was studied using a couple of symmetrical diglycolamides (TODGA and TDDGA) and an unsymmetrical diglycolamide (D3DODGA) in n-dodecane as the extraction phase. The selective stripping of Am(III) from the loaded organic phase containing trivalent Ln(III) was investigated using aqueous soluble bis-1,2,4-triazine derivatives such as SO3-Ph-BTP, SO3-Ph-BTBP and SO3-Ph-BTPhen in dilute nitric acid solution. The results revealed that the SF of Eu(III) over Am(III) decreased with increase in the concentration of nitric acid in all cases and SF decreased in the order SO3-Ph-BTP > SO3-Ph-BTBP > SO3-Ph-BTPhen. The co-stripping of lighter lanthanides (La, Ce, Pr, Nd) was also observed during the recovery of Am(III). [ABSTRACT FROM AUTHOR]

The organic phase containing tetra(2-ethylhexy)diglycolamide (TEHDGA) and n-dodecane (n-DD) was irradiated to various absorbed dose levels in a 60Co gamma irradiation chamber. The organic phase subjected to irradiation was classified in to four different categories. The extraction behavior of Nd(III) from nitric acid was studied in the degraded solution of 0.2 M TEHDGA/n-DD and the reverse micellar aggregation behavior of the extracted phase was probed by dynamic light scattering technique and ATR-FTIR spectroscopy. The results revealed that the concentration of TEHDGA decreased upon irradiation and minimized the aggregation in organic phase. The presence of n-DD along with TEHDGA during irradiation enhanced the degradation of TEHDGA, due to sensitization effect. In contrast to the assumption of deteriorating effect of gamma radiation on organic phases, the study showed that the radiolytic degradation of TEHDGA/n-dodecane minimized the aggregation and threw the third phase formation limit of Nd(III) in aqueous phase to higher values. [ABSTRACT FROM AUTHOR]

To understand the role of pKa of the organophsophorus acidic extractant on the reverse micellar aggregation behavior of the binary solution containing tetra-(2-ethylhexyl)diglycolamide (TEHDGA) + acidic extractant in n-dodecane, the extraction behavior of nitric acid and Nd(III) in the binary solution was studied. The acidic extractants chosen were bis(2,4,4-trimethylpentyl)phosphinic acid (CYANEX-272), bis(2-ethylhexyl)phosphonic acid (PC88A) and bis(2-ethylhexyl)phosphoric acid (HDEHP). The results revealed that the acidic extractant with lower pKa produced aggregates of smaller size, and therefore, the binary solution containing TEHDGA and HDEHP in n-DD was identified as the promising solvent for the extraction of trivalent metal ions from nuclear waste. [ABSTRACT FROM AUTHOR]

A customized single-stage cylindrical combined air lift mixer-settler (C-CALMIX) device has been developed and its performance was evaluated by studying the extraction behavior of U(VI) in a solution of 1.1 M tri-n-butyl phosphate (TBP) in n–dodecane (n-DD) from 4 M nitric acid medium, at 298 K. The extraction of U(VI) was studied as a function of process parameters of the C-CALMIX such as flow-rate of organic and aqueous phases, ratio of organic to aqueous flow-rates, air flow-rate etc., that are amenable for variation. The distribution ratio of U(VI) obtained under dynamic conditions in a C-CALMIX was compared with those obtained in a batch equilibrium mode. The process parameters were optimized to obtain high distribution ratio of U(VI) in C-CALMIX, comparable to that obtained at batch equilibrium mode without compromising the throughput of C-CALMIX. The stripping behavior of U(VI) from the loaded organic phase was studied using 0.01 M nitric acid. The results are reported in this paper. [ABSTRACT FROM AUTHOR]

The thermophysical properties of a couple of acidic extractants, namely bis(2-ethylhexyl)phosphoric acid (D2EHPA) and bis(2-ethylhexyl)diglycolamic acid (HDEHDGA), dissolved in the room temperature ionic liquid diluent 1-butyl-3-methylimidazolium bis(trifluoromethanesulphonyl)imide ([C4mim][NTf2]) were investigated. The physical properties such as density, viscosity, and refractive index were measured as a function of various parameters such as temperature, concentration of extractant, and concentration of nitric acid. The viscosity of the gamma-ray irradiated solution composed of 0.06 M D2EHPA/[C4mim][NTf2] and 0.06 M HDEHDGA/[C4mim][NTf2] was compared with unirradiated solution. The phase separation time (PST) was determined for both irradiated and unirradiated samples after acid equilibration. Thermogravimetry analysis was carried out for the solvent system composed of D2EHPA, HDEHDGA, [C4mim][NTf2], and 0.06 M D2EHPA(or HDEHDGA)/[C4mim][NTf2] to understand the thermal stability of the ionic liquid system. [ABSTRACT FROM AUTHOR]

Long chain monoamide extractants, N,N-di-decyloctanamide(DDOA), N,N-di-hexyldecanamide(DHDA), N,N-di-2-ethylhexyloctanamide(D2EHOA) and N,N-dihexyl-2-ethylhexanamide(DH2EHA) were synthesized and studied for the recovery of U(VI), Pu(IV) and Zr(IV) from a simulated dissolver solution of un-irradiated U–Zr metallic fuel. The results were compared with the results of N,N-dihexyloctanamide(DHOA) and tri-n-butylphosphate(TBP) under similar conditions. Solvent extraction studies were carried out for comparing the extraction behavior of U(VI), Pu(IV) and Zr(IV) in monoamide extractants with TBP system. The influence of length and branching of alkyl chains on either side of the amidic group on the extraction efficiency, third phase behaviour and metal ion selectivity in long chain monoamides has been discussed based on the results of above studies. [ABSTRACT FROM AUTHOR]

The extraction behaviour of Am(III) and other metal ions present in the fast reactor simulated high- level liquid waste (FR-SHLLW) was studied using a modifier-free solvent phase composed of N,N-di-octyl-2-hydroxyacetamide (DOHyA) in n-dodecane. Quantitative extraction of Am(III) was achieved with the co-extraction of all lanthanides, Y(III) and Mo(VI) in the first five stages of a 20-stage mixer-settler. During the stripping run with 0.5 M HNO, Am(III), Ln(III) and Y(III) were quantitatively transferred to the aqueous product in three stages. The other extracted metal ions were retained in organic phase. The results showed that the extraction performance of DOHyA was superior to other amide extractant systems reported in the literature. [ABSTRACT FROM AUTHOR]

The trivalent actinide selective neutral extractants such as carbamoylmethylphosphine oxide (CMPO) and bis-(2-ethylhexyl)diglycolamide (TEHDGA) in conjunction with an acidic extractant bis-2-ethylhexylphosphoric acid (HDEHP) have been impregnated in Tulsion ADS 400, and the resultant solvent impregnated resin (SIR) has been evaluated for the radiolytic stability towards gamma radiation. The extraction behavior of Am(III) and the loading behavior of Eu(III) in the SIR was studied as a function of absorbed dose up to 550 kGy, at different nitric acid concentrations in aqueous phase. The extraction isotherm of Eu(III) in various SIRs have been fitted using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) adsorption models. The extraction results and modeling of extraction isotherms obtained at various absorbed dose levels have been reported in this paper. [ABSTRACT FROM AUTHOR]

The imidazolium bis(2-ethylhexyl) phosphate moiety was chemically attached on silica gel by chemical modification. The resulting product ([SG-Im] [DEHP]) was characterized by FT-IR spectroscopy, thermogravimetry and elemental analysis. The sorption behavior of Am(III) and Eu(III) on [SG-Im] [DEHP] was studied from dilute nitric acid medium for the separation of Am(III) and Eu(III) from aqueous waste. The effect of time, concentrations of nitric acid and europium in aqueous phase on the distribution coefficient ( K ) was studied. The study indicated the possibility of using modified silica for the separation of Eu(III) from Am(III) with high separation factors (>50 at 0.1 M HNO). [ABSTRACT FROM AUTHOR]

A strongly hydrophobic phosphonium ionic liquid, trihexyltet radecylphosphonium bis(trifluoromethanesulfonyl)imide ([P][NTf]) was employed as the diluent for the extraction behavior of Am(III) using N,N-dihexyl-2-hydroxyacetamide(DHHy) as extractant. The extractibility of americium(III) in [P][NTf] phase was measured as a function of various parameters such as aqueous phase acidity (0.1-8 M), extractant concentration (0.01-0.15 M), equilibration time (5-120 min) and temperature (298-333 K). The extraction performance observed in DHHy/[P][NTf] was compared with those observed in N,N-dihexyloctamide (DHOA) in [P][NTf] and DHHy in other diluents such as [Cmim][NTf] and n-dodecane. The effect of temperature on D in ionic liquid system and recovery of Am(III) from the loaded phase were ascertained in detail. [ABSTRACT FROM AUTHOR]

The radiation stability of N, N-di-alkyl-2-hydroxyacetamide derivatives having alkyl side chain varying from hexyl to decyl was studied as a function of absorbed dose of gamma irradiation up to 700 kGy. The samples were irradiated as neat, and as 0.2 M solutions in n-dodecane in the presence and absence of 4 M nitric acid. The radiolytic degradation of the compounds were assessed by the measurement of distribution ratio of Am(III) (D) and also by the measurement of hydrodynamic properties such as density, viscosity and phase disengagement time. [ABSTRACT FROM AUTHOR]

Extraction of europium(III) from nitric acid medium was studied in a solution of N,N,N′,N′-tetra- n-octyldiglycolamide (TODGA) dissolved in 1-methyl-3-octylimidazolium bis(trifluormethanesulfonyl)imide ([Cmim][NTf]) ionic liquid at higher Eu(III) loading conditions ranging from 1 to 100 g/L Eu(III) in aqueous phase. The extraction of Eu(III) was studied as a function of various parameters such as the concentration of nitric acid, Eu(III) ion in aqueous phase, TODGA, nature of the ionic liquid, nature of extractant, and phase modifiers etc. The results revealed that Eu(III) could be loaded to the extent of 1: 3 stoichiometry in ionic liquid phase without leading to undesirable third phase formation. [ABSTRACT FROM AUTHOR]

The extraction behavior of palladium in a solution of tri-n-octylmethylammonium nitrate (TOMAN) and 1,3-diisopropyl benzene (DIPB) in presence of tri-n-butyl phosphate as phase modifier was studied. The distribution ratio of palladium (D) increased with increase in the concentration of nitric acid, reached a maximum at 1 M in nitric acid, followed by decrease in D values. The cyclic voltammogram of the palladium in extracted organic phase (0.5 M TOMAN + 0.1 M TBP/DIPB) showed a surge in cathode current at −0.5 V was due to the palladium deposition. The results confirmed the feasibility of using the organic phase for electrodeposition of palladium directly from extracted phase. [ABSTRACT FROM AUTHOR]

The radiolytic degradation of N, N-di-dodecyl- N′, N′-di-2-ethylhexyl-3-oxapentane-1,5-diamide (DDEHDGA) was studied at various absorbed doses of γ-radiation. The degradation was assessed by measuring the variation in the extraction behavior of Am(III) in irradiated solvent systems composed of neat DDEHDGA or 0.1 M DDEHDGA/ n-dodecane in the presence and absence of nitric acid. The distribution ratio of americium ( D) decreased with increase of absorbed dose. The presence of n-dodecane and nitric acid enhanced the radiolytic degradation of the solvent. The third phase formation behavior of Nd(III) decreased with increase of absorbed dose and the third phase was not observed at absorbed doses above 100 kGy. The recovery of Am(III) from the irradiated system was near quantitative in five contacts. The study revealed that the extraction and stripping behavior of the irradiated solvent was quite satisfactory for partitioning of minor actinides from real wastes. [ABSTRACT FROM AUTHOR]

The radiation stability of N,N-di-dodecyl- N′, N′-di-octyl-3-oxapentane-1,5-diamide (DDODGA) was studied by γ-irradiation of the solvent up to a absorbed dose of 1,000 kGy. The effect of γ-irradiation on the radiolytic degradation of DDODGA was assessed by measuring the distribution ratio of Am(III) ( D) as well as the third phase formation in the irradiated DDODGA- n-dodecane solution. The D in the irradiated solution decreased with increase of absorbed dose. The critical aqueous concentration of Nd(III) above which the third phase forms, increased with increase of absorbed dose. However, the limiting organic concentration of Nd(III) remained at ~25 mM irrespective of the absorbed dose. Recovery of Am(III) from the radiolytically degraded organic phase showed that back extraction of Am(III) was quantitative in a few contacts using dilute nitric acid. Our studies clearly indicated that radiolytic degradation of DDODGA in n-dodecane is marginal even at the absorbed dose of 1,000 kGy, and therefore DDODGA is a potential candidate for minor actinide partitioning. [ABSTRACT FROM AUTHOR]

The unsymmetrical diglycolamides (DGAs) such as N, N-dihexyl- N′, N′-dioctyl-3-oxapentane-1,5-diamide (DHDODGA), N, N-didecyl- N′, N′-dioctyl-3-oxapentane-1,5-diamide (DDODGA), N, N-didodecyl- N′, N′-dioctyl-3-oxapentane-1,5-diamide (DDODGA), were synthesized, and characterized by IR, NMR, and mass spectroscopic techniques. The extraction behaviour of Am(III), Eu(III), and Sr(II) by the solutions of these unsymmetrical DGAs in n-dodecane was studied as a function of concentration of nitric acid and DGA. The distribution ratio of Am(III) and Eu(III) increased with increase in the concentration of nitric acid; whereas, the distribution ratio of Sr(II) reached a maximum at 4 M nitric acid followed by decrease at higher acidities. The extraction of Am(III) and Eu(III) in 0.1 M DGA/ n-dodecane decreased in the order DHDODGA > DDODGA > DDODGA. However, the order changed upon lowering the concentration of DGA. The third-phase formation behaviour of nitric acid and neodymium(III) in 0.1 M DGA/ n-dodecane was studied as a function of concentration of nitric acid. The limiting organic concentration of nitric acid and neodymium increased with increase in the chain length of alkyl group attached to amidic nitrogen. Near stoichiometric amount of neodymium(III) was loaded in 0.1 M DDODGA/ n-dodecane without the formation of third-phase from 3 to 4 M nitric acid medium. The study revealed that the unsymmetrical diglycolamides DDODGA and DDODGA are superior candidates for partitioning the minor actinides from high-level liquid waste. [ABSTRACT FROM AUTHOR]

Extraction of europium(III) from nitric acid medium by a solution of tri- n-butylphosphate (TBP) and n-octyl(phenyl)- N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in the room temperature ionic liquid, 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (amimNTf where a = butyl or hexyl or octyl), was studied. The distribution ratio of Eu(III) in TBP-CMPO/bmimNTf was measured as a function of various parameters such as the concentrations of nitric acid, CMPO and NaNO. Remarkably large distribution ratios were observed for the extraction of europium(III) when bmimNTf acted as diluent. The stoichiometry of metal-solvate in organic phase was determined by the slope analysis of extraction data. [ABSTRACT FROM AUTHOR]

Lithium assisted electrochemical reduction of UO in the room temperature ionic liquid (RTIL), N-methyl- N-propylpiperidinium bis(trifluoromethylsulfonyl)imide (MPPiNTf), was studied to explore the feasibility of using RTILs for direct electrochemical reduction of uranium oxide at near ambient temperature. The electrochemical behavior of Li in MPPiNTf at stainless steel electrode was investigated by cyclic voltammetry and chronoamperometry. The cyclic voltammogram of LiNTf in MPPiNTf at 373 K consisted of a surge in cathodic current occurring at a potential of −2.8 V (vs. Fc/Fc) due to the reduction of Li(I) to metallic form. The nucleation phenomenon observed in the voltammogram was investigated by chronoamperometry. Electrodeposition of metallic lithium on UO particles contained in a stainless steel (SS) basket was carried out to examine the feasibility of reducing UO to metallic form. The results are discussed in this paper. [ABSTRACT FROM AUTHOR]

High-level liquid waste from fast reactor fuel reprocessing stream contains significant quantities of lanthanides and trivalent minor actinides. The lanthanides and minor actinides (MA) have been separated from the fast reactor high-level liquid waste (FR-HLLW) using TRUEX solvent, which is a mixture of 0.2 M octyl(phenyl)- N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO)-1.2 M tri- n-butylphosphate (TBP) in n-dodecane. A new stripping composition, 0.1 M HNO and 0.1 M citric acid (CA), has been employed for back extraction of them from the TRUEX solvent. In order to separate lanthanides from actinides present in the strip solution, the extraction behavior of Am(III) and Eu(III) from CA–HNO medium by a solution of bis-2-ethylhexylphosphoric acid (HDEHP) in n-dodecane has been studied. Separation factors (SF = D/ D) has been reported as a function of various parameters such as pH, concentrations of HDEHP, diethylenetriamine- N, N, N′, N′′, N′′′-pentaaceticacid (DTPA), 1-octanol and TBP in this paper. [ABSTRACT FROM AUTHOR]

The electrochemical behavior of ruthenium(III) and rhodium(III) in nitric acid medium has been studied at platinum and stainless steel electrodes by cyclic voltammetry. The cyclic voltammograms consisted of surge in cathodic current occurring at potentials of −0.13 V (Vs. Pd) and −0.15 V (Vs. Pd), which culminates into peaks at −0.47 V and −0.5 V due to the reductions of Ru(III) and Rh(III) to their metallic forms, respectively. Electrodeposition was carried out at stainless steel electrode and unlike palladium, the recovery of ruthenium and rhodium was limited to ~4% and ~14%, respectively. However, a different scenario was observed in case of electrodeposition from a ternary solution containing all these platinum metals. Ruthenium and rhodium deposited underpotentially in the presence of palladium and the recovery of ~20% and ~5% was observed for ruthenium and rhodium, respectively. Evolution of RuO4 at the anode and deposition of RuO2 in the anodic side was observed in all cases during electrolysis of ruthenium(III) containing solutions. [ABSTRACT FROM AUTHOR]

Laboratory experiments were performed on the sorption of cesium on gamma-irradiated silica-titania gel. The detrimental effects of absorbed dose on the affinity of the sorbent towards cesium was discussed. Data obtained from sorption studies were fit into heterogeneity based Freundlich isotherm. The empirical parameters, thus obtained were used to arrive at the site distribution function. The potential of site distribution function in foreseeing, the reusability and long-term residence of radionuclides in the sorbent has been highlighted. [ABSTRACT FROM AUTHOR]

The amphoteric nature of hydrous silica-titania gel and its sorption behaviour towards cesium were studied. In NaNO3 solution, the point of zero change (pHpzc) of the gel was found to be 4.22 by pH-titration. The fraction of protonated, deprotonated and neutral surface hydroxyl groups as a function of pH have been computed. Sorption of cesium increased with the increase of pH, reached maximum at a pH of 7 followed by a plateau. Significant uptake of cesium was observed even when the pH was less than pHpzc. Nearly 70% sorption was observed at pHpzc. The free energy of specific adsorption was found to be −18.7 kJ·mol−1. [ABSTRACT FROM AUTHOR]

A silica-titania (Si−Ti) mixed hydroxide gel with Ti to Si mole ratio of 1∶1 was prepared. Studies on the sorption of radiostrontium from alkaline solutions having various concentrations of sodium were carried out with Si−Ti. The distribution coefficient ( Kd) of strontium decreased with increasing concentrations of sodium from 0.1 to 4.0 mol·dm−3. The plot of log Kd versus log [Na+] gave a slope of −0.55 as against the theoretical value of −2.0. This suggests that some other paths in addition to the simple stoichiometric ion exchange is also existing for sorption. From pH titrations the pHpzc of Si−Ti was found to be 4.22 coinciding nearly with the pH sorption edge. An attempt was made to correlate the sorption results with the surface characteristics of the sorbent. It was found that sorption is favored when the surface of the sorbent transforms into an anionic form. Sharp increase in the sorption of strontium was observed when the equilibrium pH was between 7 and 10. This behavior could be attributed to the abrupt increase in net negative charge on the surface of the sorbent. [ABSTRACT FROM AUTHOR]

The 0.1 M TODGA + 0.2 M DOHyA/n-DD phase was irradiated to various absorbed dose levels and the extraction behaviour of nitric acid and Nd(III) in the irradiated organic phases were studied. The organic phase was then subjected to dynamic light scattering studies to understand the aggregation behaviour in the organic phase. The results showed that the polar degradation products formed in the organic phase decreased the aggregation, while the higher homologue of n-DD enhanced aggregation. [ABSTRACT FROM AUTHOR]