The Impact of Core Flow Rate on the Hydrogen Water Chemistry Efficiency in Boiling Water Reactors

It is currently a common practice that a boiling water reactor (BWR) adopts hydrogen water chemistry (HWC) for mitigating corrosion in structural components in its primary coolant circuit (PCC). The optimal feedwater hydrogen concentration ([H₂]_FW) varies from plant to plant and is usually set at a constant value. When the core flow rate (CFR) in a BWR is changed, the coolant residence time in the PCC would be different. The concentrations of major redox species (i.e., hydrogen, oxygen, and hydrogen peroxide) in the coolant may accordingly vary because of different radiolysis durations in the core and other near-core regions. A theoretical code by the name of DEMACE was used in the current study to investigate the impact of various CFRs (from 100 to 80.6%) on the effectiveness of HWC in a domestic BWR. Our analyses indicated that the HWC effectiveness could be downgraded because of an increase in CFR at locations such as upper downcomer, recirculation system, and lower plenum. However, the HWC efficiency at the upper plenum area did not vary with either increasing or decreasing CFRs. The impact of CFR on the HWC effectiveness is therefore expected to vary from location to location in a BWR and eventually from plant to plant.