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Mineo, Hideaki; Asakura, Toshihide; Hotoku, Shinobu; Ban, Yasutoshi; Morita, Yasuji
Proceedings of GLOBAL2003 Atoms for Prosperity; Updating Eisenhower's Global Vision for Nuclear Energy (CD-ROM), p.1250 - 1255, 2003/11
An advanced aqueous reprocessing process has been proposed for the next generation fuel cycle. Key technologies applied to the process are: removal of I-129, separation of Np and FP(Tc) separation by selective reduction of Np(VI) and high acid scrubbing of Tc within a single cycle process, MA separation by extraction chromatography and Cs/Sr separation. U separation just after dissolution was supposed to be effective to reduce the required capacity of the following extraction step. Among them Np reduction rate in TBP solution was measured, which was found to be lower than that in aqueous solution. Using an improved flow sheet spent fuel test, based on the Np reduction test, was carried out and about 90% of Np was separated before U and Pu partitioning step.
Kaneko, Masashi; Watanabe, Masayuki; Matsumura, Tatsuro
no journal, ,
In Japan Atomic Energy Agency, the extraction reagents for the inter- and intragroup separation of mainor-actinides from lanthanides have been developed in order to construct the partitioning and transmutation process. We aim to reveal the separation mechanism using various extraction materials at a molecular level and to design the novel extraction reagents. In this study, we apply density functional calculations to the separation behavior of Am(III) from Eu(III) by DGA and NTA ligands. All metal compounds were modeled by referring the literatures. As the result, DGA ligand selectively coordinates to Eu(III) than Am(III), on the other hand, NTA ligand preferably coordinates to Am(III) than Eu(III), being consistent with the experimental selectivity.
Kaneko, Masashi
no journal, ,
Density functional theory (DFT) calculations have been employed to understand the equilibrium structures, electronic states, and stabilities of minor-actinides (MA) and lanthanides (Ln) complexes. An previous application of DFT calculation to the MA/Ln separation has indicated that the Am/Eu selectivity can be explained by the stability in complexation reaction. However, the origin of Am/Eu selectivity remains unclear. This study aims to understand the origin by correlating the stability of their complexes with the covalency in metal-ligand coordination bonds by means of scalar-relativistic DFT calculations. After an optimization of DFT method using benchmark study with M
ssbauer spectroscopic parameters, we applied the DFT method to the separation of Am from Eu and analyzed the bonding states between metal and ligands in Eu and Am complexes. As a result, it was found that the wave functions of Eu ion with ligands have syn-phase overlap not depending on donor atoms, whereas those of Am ion have syn-phase overlap in the case of sulfur donors and anti-phase in the case of oxygen donors. This indicates that the difference in bonding states between metal and ligands is an origin in the Am/Eu selectivity.
Kaneko, Masashi; Watanabe, Masayuki; Matsumura, Tatsuro
no journal, ,
In Japan Atomic Energy Agency, the extraction reagents for the inter- and intragroup separation of mainor-actinides from lanthanides have been developed in order to construct the partitioning and transmutation process. We aim to reveal the separation mechanism using various extraction materials at a molecular level and to design the novel extraction reagents. In this study, we design a novel TPEN-type extraction reagent in which carbonyl donors are introduced and predict its separation performance of Am(III) from Eu(III) using density functional calculations. We modeled molecular complexes by referring single crystal structures and compared the stability between Eu(III) and Am(III) complexes. As a result, the relative stability of Am complex to Eu complex increased and its separation factor was improved by an order from five to twenty compared to the prediction value by non-substituent TPEN ligand.