Evaluation of power distribution calculation of the very high temperature reactor critical assembly (VHTRC) with Monte Carlo MVP3 code

Simanullang, I. L.* ; Nakagawa, Naoki*; Ho, H. Q.   ; Nagasumi, Satoru; Ishitsuka, Etsuo   ; Iigaki, Kazuhiko ; Fujimoto, Nozomu*

Power distribution plays a significant role in preventing the fuel temperature exceeds the safety limit of 1600C in high-temperature gas-cooled reactors. The experiment to measure the power distribution in the graphite-moderated system was carried out with the Very High Temperature Reactor Critical Assembly facility. In the previous study, the power distribution in the VHTRC was calculated using a nuclear design code system based on diffusion calculation. The results showed a maximum discrepancy of up to 20% between the experiment and calculated values in the axial direction. The large discrepancy occurred near the boundary of fuel and reflector regions. This study describes the evaluation results of pin-wise power distribution of the VHTRC with the Monte Carlo MVP3 code. The calculation results were in good agreement with the measured results. In the axial direction, the discrepancy was less than 1% around the boundary of fuel and reflector regions.