The Basic Research on the Formation of the Neutron Irradiation Field for the Minor Actinides Transmutation

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This study is a basic research on transmutation of minor actinide. By measuring relative nuclear fission rate rations of the minor actinide to the uranium in the irradiation fields, which have different neutron spectrums, it is to find that of adequate neutron field for transmutation of the minor actinide.Experiments were performed using polyethylene moderated, highly-enriched uranium cores at a solid moderated core in the KUCA. In order to systematically vary the neutron spectrum of the neutron field, the H/<235>^U ratio of the core has been systematically varied. Three cores were employed in this study; those cores were designated as EEE1, E1 and E3-core respectively. The neutron spectrum was evaluated in both of calculation and experiment using activation foil method.The fission rate ratio measurements have been performed using track-etch detectors put in a special irradiation apparatus used for the alternative of the back-to-back type double fission chamber.The ratio of the number of the effective atom on the target also used the track-etch detectors too. This agrees with the previous report value on the ratio of <237>^ Np and ^<235>U number of atoms in 13 : 1. At the center of the E1 core, the measured value of <237>^Np/<235>^U fission rate ratio was 0.016 is smaller than the previous report value about 30%. Data analysis of other core is now being performed.