Simulation of xenon-induced oscillation in a 1400 MWe pressurized water reactor

Abstract

Xenon-135 is a strong neutron absorber in thermal reactors, and plays a key role in reactor spatial dynamics. This study investigates xenon-induced axial power oscillations during a small load-follow transient using a generic pressurized water reactor (GPWR) simulator. A 1.4% power reduction followed by 23 hours of evolution was analyzed to capture xenon–iodine feedback behavior. Results show that even minor perturbations can trigger significant xenon redistribution, leading to delayed axial offset oscillations due to time-lagged coupling between power, iodine decay, and xenon buildup. Initial control rod insertion shifts power toward the lower core, but evolving xenon effects gradually reverse this distribution, producing transient axial offset inversion. Although the system remains stable, localized power peaking and temperature redistribution occur. The study confirms that xenon dynamics strongly influence spatial power behavior and must be carefully managed during load-follow operation to maintain stability and thermal margins.