A cycle-specific cross-section update for real-time simulation of VVER-1000 core

• A real-time version of the NEM three-dimensional kinetics code is developed.
• The version is implemented for VVER-1000 full-scope simulator applications.
• Cross-section update methodology provides cycle-specific simulation capability.
• Rated power and MSIV inadvertent closure transient examples are shown.

A two-group cross-section generation methodology, cycle-specific cross-section update procedure and VVER-1000 reactor core model are described. The HELIOS lattice physics code is used to calculate the cross-section data tables according to a customized version of the cycle-specific cross-section modelling methodology of the Pennsylvania State University (PSU). A real-time version of the NEM code from PSU is developed for VVER-1000 full-scope simulator applications. The cross-section update procedure is tailored to meet cycle-specific reactor core simulation fidelity requirements as well as particular customer needs and practices. Combined with an enhanced thermal-hydraulics and Instrumentation (I&C) models the scope of Kozloduy 6 full-scope replica control room simulator is expanded to the whole range of plant operation modes ranging from cold shutdown (depressurized) state to rated power, as well as deviations from normal operating modes and even beyond-design basis accidents. The fidelity and accuracy of simulation is illustrated through comparison with plant-specific data.