Simulation of VVER-1000 startup physics tests using the MCU Monte Carlo code

The main objective of this work is to make the quality test and verification of a full-scale computer model of the VVER-1000 reactor with the detailed description of the geometry and material composition. Using the computer model and MCU Monte Carlo code, we simulated the experiments conducted at the stage of physical start-up of the third power unit of Rostov NPP (Russia) in December 2014. The following neutron-physical characteristics were calculated: effective neutron multiplication factor, critical boric acid concentration, efficiency of single control rod cluster, integral and differential efficiency of control rod group, scram system reactivity worth, and reactivity coefficients. The calculated neutron-physical characteristics were compared with the measured ones. The comparison shows agreement with the measured data over the range of the experimental error and statistical uncertainty of the calculation. To reduce the impact of statistical uncertainty on the calculated differential control rod reactivity worth and reactivity coefficients we applied a special approach for the estimation of these parameters.