No abstract

The computer code PARC was developed in Japan Atomic Energy Agency, in order to predict the behavior of uranium, plutonium, neptunium, and severalˆssion products in a reprocessing plant for spent nuclear fuel. This code has several useful calculation functions, i.e., PARC can deal with both mixer settlers and pulsed columns simultaneously, and new equations for chemical reaction, reaction constant, and distribution ratio can be easily inputted to PARC without the recompilation of the program. Therefore, it is expected to be widely used for basic solvent extraction study, separation process design, plant management, and safety analysis for future reprocessing. In the present paper, the outlines of an extractor model and several chemical reaction models used in PARC are introduced, and results of calculations for uranium and plutonium behaviors in the U/Pu separation process in PUREX are shown, which enable the elucidation of the eŠect of the increase in Pu concentration in the feed solution and the importance of the selection of Pu oxidation/ reduction reaction models.

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New reagent, N,N,N′,N′,N′′,N′′-hexaoctylnitrilotriacetamide (NTAamide(C8)), was synthesized and examined for actinoid and lanthanoid extractions. NTAamide(C8) has one N atom and three carbonyl oxygen atoms in the central frame, and may show hybrid bonds between hard O and soft N donors. It was found that NTAamide can extract Am(III) and Cm(III) from diluted HNO3 with small D(Ln). This result suggests that the N-donor makes stronger complexes with Am(III) and Cm(III) than Ln(III) at low HNO3.

Alkyl diamide amine (ADAAM), a new high-performance reagent with a simple structure, was examined for the mutual separation of Am(III) and Cm(III). The combination of ADAAM and N,N,N′,N′-tetraethyldiglycolamide (TEDGA) as a masking agent shows selectivity for Am(III) over Cm(III) in highly acidic media with separation factors of up to 41.