Worldwide BWR Chemistry Performance with Noble Metal Chemical Addition

Abstract Noble metal chemical addition (NMCA) is an industry-wide accepted approach for potential intergranular stress corrosion crack (IGSCC) mitigation of boiling water reactor (BWR) internals. NMCA has been successfully applied in 26 BWRs worldwide. Those BWRs that have applied NMCA and used low levels of feedwater hydrogen have achieved the HWC specification potential of -230 mV(SHE) without the long-term operating dose rate increases due to partitioning of N16 into the steam phase. NMCA is a simpler method of applying noble metal on to BWR internals surfaces using reactor water as the transport medium that causes the deposition of noble metal from the liquid phase onto wetted surfaces. The technology has been successfully used to improve the efficiency of hydrogen water chemistry (HWC) for potentially mitigating IGSCC of BWR internals. One BWR has completed 52 months of plant operation after NMCA that included a reapplication. Eight BWRs have completed at least one fuel cycle of operation following NMCA. The total cumulative operating experience with NMCA is 41 years to date. This paper describes the worldwide BWR performances with NMCA, with low ECPs at measured locations, no operating dose rate increases and low drywell dose rates.