Jammu Ravi

Feasibility of Using Di-Dodecyl-Di-Octyl Diglycolamide for Partitioning of Minor Actinides from Fast Reactor High-Level Liquid Waste

The unsymmetrical diglycolamide, di-dodecyl-di-octyl diglycolamide (D3DODGA) is a modifier-free extractant proposed for partitioning of trivalent actinides from nitric acid medium. D3DODGA has been evaluated for the feasibility of using it in the absence of a phase modifier, for the partitioning of minor actinides from fast reactor high-level liquid waste (FR-HLLW). The extraction behavior of various metal ions present in the simulated FR-HLLW was studied in a solution of 0.1 M D3DODGA/n-dodecane from nitric acid medium. The distribution ratio of about 20 metal ions was measured as a function of concentration of nitric acid and other interfering ion. The extraction was found to be strongly dependent on the oxidation state of the metal ion. The extraction of Am(III) from 3–4 M nitric acid medium was quantitative in a single contact. However, it was accompanied by the quantitative extraction of fission products such as trivalent lanthanides (Ln(III)), Y(III), and Zr(IV). The extraction of Sr(II), Pd(II), and Ru(III) in 0.1 M D3DODGA/n-dodecane was not insignificant, but quite low. The extraction of Ba(II), Ni(II), Mo(VI), and Fe(III) was marginal and the extraction of Co(II), Sb(III), Mn(II), and Cs(I) in 0.1 M D3DODGA/n-dodecane was negligible. Our results indicated that 0.1 M D3DODGA/n-dodecane is a promising candidate for the separation of trivalent actinides from fast reactor high-level liquid waste containing significant quantities of trivalent lanthanides and actinides.

New unsymmetrical digycolamide ligands for trivalent actinide separation

Abstract New unsymmetrical diglycolamides (UDGAs), N, N-di-butyl-N′, N′-di-dodecyl-3-oxapentane-1,5-diamide (C12-C4), N, N-di-dodecyl-N′, N′-di-hexyl-3-oxapentane-1,5-diamide (C12-C6), N, N-di-decyl-N′, N′-di-dodecyl-3-oxapentane-1,5-diamide (C12-C10) have been synthesized, and evaluated for the separation of americium(III) and europium(III) from nitric acid medium. The extraction behavior of Am(III), Eu(III), and Sr(II) in a solution of these UDGAs in n-dodecane was studied as a function of concentration of nitric acid in the aqueous phase. The distribution ratio of Am(III) and Eu(III) increased with increase in the concentration of nitric acid. The third phase formation behavior of nitric acid and neodymium(III) in 0.1 M UDGA/n-dodecane was studied. The third phase formation was not observed in all these UDGAs in n-dodecane (0.1 M), when the concentration of Nd(III) was ∼ 500 mM in 3–4 M nitric acid. The stoichiometry of Am(III)-UDGA was determined from the slope analysis of the extraction data, which indicated the formation of 1:3 complex in all cases. Our studies revealed that the UDGA ligands with dodecyl group attached to one amidic nitrogen atom is inevitable for preventing third phase formation and the alkyl group at the other amidic nitrogen can be varied from butyl to decyl group for obtaining efficient extraction of trivalent actinides from high-level nuclear waste.

Single-cycle method for partitioning of trivalent actinides usingcompletely incinerable reagents from nitric acid medium

Abstract A new approach, namely “Single-cycle method for partitioning of Minor Actinides using completely incinerable ReagenTs” (SMART), has been explored for the separation of Am(III) from Eu(III) present in nitric acid medium. The extraction behavior of Am(III) and Eu(III) in a solution of an unsymmetrical diglycolamide, N,N,-didodecyl-N′,N′-dioctyl-3-oxapentane-1,5-diamide (D3DODGA), and an acidic extractant, N, N-di-2-ethylhexyl diglycolamic acid (HDEHDGA), in n-dodecane was studied. The distribution ratio of both these metal ions in D3DODGA-HDEHDGA/n-dodecane initially decreased with increase in the concentration of nitric acid reached a minimum at 0.1 M nitric acid followed by increase. Synergic extraction of Am(III) and Eu(III) was observed at nitric acid concentrations above 0.1 M and antagonism at lower acidities. Contrasting behavior observed at different acidities was probed by the slope analysis of the extraction data. The study revealed the involvement of both D3DODGA and HDEHDGA during synergism and increased participation of HDEHDGA during antagonism. The stripping behavior of Am(III) and Eu(III) from the loaded organic phase was studied as a function of nitric acid, DTPA, and citric acid concentrations. The conditions needed for the mutual separation of Am(III) and Eu(III) from the loaded organic phase were optimized. Our studies revealed the possibility of separating trivalent actinides from HLLW using these completely incinerable reagents.

Solvent extraction behavior of trivalent metal ions in diglycolamides having same carbon to oxygen ratio

Abstract Various diglycolamides (DGAs), N,N,N’,N’-tetraoctyl diglycolamide (TODGA), N,N-di-2-ethylhexyl-N’,N’-di-octyl diglycolamide (DEHDODGA), N,N,N’,N’-tetra-2-ethylhexyl diglycolamide (TEHDGA), N,N-di-decyl-N’,N’-di-hexyl diglycolamide (D2DHDGA), N,N-di-butyl-N’,N’-di-dodecyl diglycolamide (DBD3DGA), N,N,N’,N’-tetra-hexyl diglycolamide (THDGA), and N,N,N’,N’-tetradecyl diglycolamide (TDDGA) have been synthesized and studied for the extraction of Am(III) and Eu(III) from nitric acid medium. An attempt was made to understand the extraction and third phase formation behavior of trivalent metal ions in these DGAs. Our results revealed that despite having the same carbon to oxygen ratio in these DGAs, the third phase formation behavior and extractions achieved in these DGAs are significantly different.

Radiolytic stability of di-2-ethylhexyl-dioctyl diglycolamide

Abstract The radiation stability of an unsymmetrical diglycolamide, di-2-ethylhexyl-di-octyl diglycolamide (DEHDODGA) has been evaluated under various process conditions. The influence of diluent (n-dodecane), phase modifier (N,N-dihexyl octanamide, DHOA), and nitric acid on the radiolysis of DEHDODGA was investigated. The distribution ratio (D) of Am(III), Eu(III), and Sr(II) in the irradiated solvent was determined as a function of absorbed dose of γ-radiation. The distribution ratios decreased with increase of absorbed dose, indicating the radiolytic degradation of DEHDODGA with increase of absorbed dose. The stripping behavior of Am(III) from the degraded organic phase was studied. Quantitative back extraction of trivalent metal ions from the irradiated organic phase was achieved in a single contact using the stripping formulation composed of dilute nitric acid and citric acid. Our studies indicated the robust nature of DEHDODGA with respect to radiolysis, and innocuous nature of degradation products.

Feasibility studies of using N,N-dihexyloctanamide (DHOA) for fast reactor fuel reprocessing applications

Abstract N,N-dihexyloctanamide (DHOA) is being considered as a promising extractant in the aqueous reprocessing of spent nuclear fuels. In view of rise in temperature of the solvent during reprocessing of fast reactor fuel, the present study aimed at evaluating the physical properties such as density, viscosity, and interfacial tension and Pu(IV) extraction behavior in 1.1 M DHOA/n-dodecane as a function of temperature and duration of heating. The influence of nitric acid in altering the physical properties with respect to temperature was evaluated. Physical properties and extraction behavior of the solvent changed to a remarkable extent with temperature. Quantitative amount of Pu(IV) could be back-extracted from loaded, solvent in three contacts at 313 K. FT-IR studies were carried out to evaluate the thermal stability of the solvent. Thus, the performance of the solvent, 1.1 M DHOA/n-dodecane is satisfactory at higher temperatures also.