Research and Development on C-14 Isotope Separation.

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The present work deals with the carbon isotope separation to reduce C-14 contaminated waste generated at the decommissioning of the graphite type reactors. Since the simplest treatment of the graphite is burning, CO and CO_2 were selected as the working materials for the separation. The research activities are divided into following three sub-topics.(1) Theoretical study on carbon isotope effects by molecular orbital theoryThe most appropriate molecular structures and molecular vibrations of CO complexes with Cu (I) and Ag (I) ions and CO_2 complexes with 30 amines were determined by using the computational chemistry program of Gaussian 98 7A.By using computed vibrational frequencies, the reduced partition function ratios of the isotopic molecules were calculated and thus the separation factors (α) of CO and CO_2 complexes were calculated.(2) Experimental study on carbon isotope effects of CO complexesCO is known to form complexes with Ag (I) and Cu (I) ions. In the present work the isotope separation coefficients of CO complexes with Ag (I) in non aqueous solvents and Cu (I) ions in aqueous solutions and amine methanol solutions were determined for the stable isotope pair of ^<12>C and ^<13>C at different temperatures. The maximum value of α observed was 1.03 at-43℃. The results suggest that one can expect the value α=1.06 for the isotope pair ^<12>C and ^<14>C.(3) Study on ion exchange multi-stage enrichmentAs a basic study on the multi-stage isotope enrichment of CO_2 complex systems, chromatographic experiments of Cu (I) and Fe (III) chloride complex were performed using column packed with anion exchange resin. In these experiments, the isotope separations of copper and iron were successfully observed at the boundaries of Cu (I) and Fe(III) ion adsorption bands.