Plant Chemistry Response to On-Line NobleChem^TM

Noble metal chemical addition is widely and successfully used in boiling water reactors (BWRs) as a mitigation method for intergranular stress corrosion cracking (IGSCC). This technology is used to reduce the electrochemical corrosion potential (ECP) of reactor internals and associated piping while maintaining low hydrogen injection rates. Over the past six years, BWRs have started to transition away from applying noble metals during refueling outages to the application of noble metals while the reactor is operating at full power using the On-Line NobleChem^TM (OLNC) process. The ability to apply noble metals on-line allows for greater reapplication flexibility and eliminates the impact of an application on the duration of refueling outages. As more plants have begun to perform OLNC applications, the industry has started to accumulate a significant amount of reactor water chemistry and operating experience for periods both during and after injections. The intent of this paper is to summarize changes in chemistry parameters typically observed during and after an OLNC application, such as increases in reactor water conductivity and activated corrosion by product levels. These parameters can therefore be used during an OLNC injection as secondary indicators of application progress. This paper will also discuss methods of monitor an application, including direct ECP measurements and the use of secondary indicators. (authors)