Modeling Water Chemistry, Electrochemical Corrosion Potential, and Crack Growth Rate in the Boiling Water Reactor Heat Transport Circuits — III: Effect of Reactor Power Level

The DAMAGE-PREDICTOR computer code, which has the capability of simultaneously estimating the concentrations of radiolysis species, the electrochemical corrosion potential (ECP), and the crack growth rate (CGR) of a reference crack in sensitized Type 304 stainless steel, is used to evaluate the responses of the Dresden-2 and Duane Arnold boiling water reactors (BWRs) to hydrogen water chemistry (HWC) at different power levels. The HWC simulations for these two BWRs are carried out for feedwater hydrogen concentration ([H2]fw) ranging from 0.0 to 2.0 parts per million and for power levels at 100, 90, 80, and 70%. Variations in the oxygen, hydrogen peroxide, and hydrogen concentrations; ECP; and CGR for four specific areas (the side of the core shroud head, the base of the core shroud, the recirculation system outlet, and the bottom of the lower plenum) as a function of the feedwater hydrogen concentration and power level are analyzed. It is found that lower power levels alleviate the amount of hydrogen injected into the feedwater that is required to protect the reactor components from intergranular stress corrosion cracking. HWC is particularly effective in protecting the base of the core shroud and the recirculation system outlet but is only moderately effective in protecting the bottom of the lower plenum. On the other hand, the ECP and the CGR at the side of the core shroud head seem to be indifferent to both the operating power level and the feedwater hydrogen concentration.