Simulation and analysis of core barrel vibrational modes associated with neutron noise phenomena in WWER-type reactors

Abstract

This survey focuses on an approach to address various vibrational modes of the core barrel in a hexagonal-structured reactor core. The core barrel vibration is considered one of the main mechanical vibrations in a high-power nuclear reactor, initiating core component malfunctions and safety issues. Here, a well-reasoned method is proposed to handle the triple vibrational modes of such core barrels, whether individually or in combination with fuel assembly vibrations. The modeling of core barrel vibrations involves modifying the lattice water width for boundary fuel assemblies and correlating it with external reactivity in the time-dependent calculation. The radial and axial distributions of neutron noise amplitude, phase, and spectrum are further analyzed for several scenarios using the designed neutron noise simulation tool, DYNOSIM. The outcomes support using the suggested methodology to simulate neutron noise in hexagonal cores due to different modes of core barrel vibration.