VIABILITY OF HYDROGEN WATER CHEMISTRY FOR PROTECTING IN-VESSEL COMPONENTS OF BOILING WATER-REACTORS

A mixed potential model (MPM) has been developed for calculating electrochemical potential (ECP) data for boiling water reactor (BWR) in-vessel components and recirculation piping using compositional data obtained from radiolysis water chemistry models. The calculated core component ECPs for the Duane-Arnold BWR are in good agreement with limited in-plant data. The calculated ECP data suggest that hydrogen water chemistry (HWC) will be effective in protecting the core inlet and the recirculation system of Duane-Arnold against intergranular stress corrosion cracking (IGSCC) but that it may not be effective for this purpose in Dresden-2 because of the higher concentrations of radiolysis products (notable O2 and H2O2) predicted to exist in this reactor. Furthermore, the MPM predicts that HWC will be ineffective in protecting various in-vessel components such as the upper plenum, fuel channels, core bypass structure, and the downcomer. Electrocatalysis of the redox reactions shows promise as a means of enhancing the effectiveness of HWC, and it is also predicted to be viable under NWC conditions provided that hydrogen oxidation alone can be catalyzed. However, in this case, the exchange current density for hydrogen oxidation must be enhanced by a factor in excess of 10(4) for protection to be achieved.