Monte Carlo calculation analysis of measurements of fission rate distributions in light-water-moderated cores loaded with mixed oxide and UO₂ fuels

To extend the information on the validation of the JENDL-4.0 nuclear data library, continuous-energy Monte Carlo calculation was applied to the analysis of the measured core radial fission rate distributions in the light-water-moderated cores loaded with mixed oxide (MOX) and UO₂ fuel rods. The measured results were taken from the reports of the critical experiments performed using the Tank-type Critical Assembly (TCA) of the Japan Atomic Energy Agency in the 1970s. The PuO₂ contents of the MOX fuel ranged from 1.14 wt% to 3.37 wt% and the enrichments of the UO₂ fuel from 1.180 wt% to 2.596 wt%. The lattice pitches were from 1.660 cm to 1.956 cm. A half number of cores in the analyzed 30 cores were mainly loaded with the MOX fuel rods and the others were the MOX-UO₂ mixed cores or the UO₂ cores. The calculated results generally well reproduced the measured fission rates of the MOX and UO₂ fuel rods in the test fuel assemblies and those in the x-direction and diagonal direction of the cores. (author)