Abstract
Reduction of electrochemical corrosion potential (ECP) of Boiling Water Reactor (BWR) vessel and internals is essential for mitigating intergranular stress corrosion cracking (IGSCC). Hydrogen water chemistry in moderate concentrations (HWC-M) or at reduced injection rates with noble metals are IGSCC mitigation strategies employed by BWRs. In-vessel lower plenum ECP measurements have been obtained during operating conditions for BWRs utilizing normal water chemistry, HWC-M and first generation noble metals. ECP monitoring for BWRs with second generation has been limited to probes mounted in external piping and monitoring skids. The chemistry conditions and radiolysis effects at these locations are typically not as aggressive as in the lower vessel head region, where no direct in-vessel ECP measurements have been made during a full power noble metals injection.
Brunswick 1 has utilized HWC-M as a mitigation strategy for protection of IGSCC since 1989. In August 2014, the station transitioned to second generation noble metals. Prior to the transition, two platinum ECP electrodes and a pre-oxidized stainless steel billet were installed in a modified local power range monitor (LPRM) during the preceding refueling outage. This paper will present industry-first lower plenum in-vessel ECP measurements during the transition from HWC-M to second generation noble metals with HWC, applied will the plant is operation.
