Validation study of the Monte Carlo code MVP for analysis of two-region TCA critical experiments with PWR-type MOX fuels

A series of critical experiments containing PWR-type MOX fuels conducted at the TCA facility of Japan Atomic Energy Research Institute have been analyzed. The cores were composed of a central 4.91 wt% plutonium enriched mixed-oxide (PuO2–UO2) 10 × 10 test lattice with water-to-fuel volume ratio of 2.40 or 2.96, surrounded by 2.6 wt% enriched UO2 driver lattice with water-to-fuel volume ratio of 1.50 with a water gap in-between. The fissile plutonium content was 91.4 wt%. The critical water level, the power distribution in the test region, and the neutron activation distribution of Au-wire were measured for six different cores of which two contain soluble boron of 309.4 and 554.0 ppm, one contains four equidistant water holes in the central test lattice and one contains cross water gap at the core center. Calculation of corresponding effective multiplication factor, the fission reaction-rate distribution in the test region, and the capture reaction-rate distribution of Au have been performed using a continuous-energy Monte Carlo code MVP with two nuclear data sets based on JENDL-3.2 and JENDL-3.3. The calculated results agreed to the measurements within a maximum difference of 0.27% for the effective multiplication factors, 3.0% for the power distributions, 5.9% for the thermal activation distributions throughout the whole region, and 4.3% for the epithermal activation distributions in the core region.