The measurement of reaction rate distributions of the cores with spectrum shifter

Basic neutronics study for the spectrum-controlled neutron irradiation fields using various reflector materials were performed. The spectrum shifter regions were constructed at the upper reflector region of the solid moderated core (B-Core) of the Kyoto University Critical Assembly (KUCA). Beryllium, graphite, aluminum were selected as the loading material. Two cores with different moderator-to-fuel volume ratio (Vm-Vf) of 0.97 and 0.65 have been utilized. Axial reaction rate distributions of gold, nickel, indium and tungsten wires were measured. Comparison between measurement and calculation was performed. Reaction rate ratio distributions, which could be used as the spectrum index, were also measured and analyzed. (author)