NEXT GENERATION OF NOBLE METAL APPLICATION FOR BOILING WATER REACTORS

摘要

GE Hitachi Online NobleChem™ (OLNC) has beenimplemented at all but two operating US boiling waterreactors (BWRs) and several non-US BWRs. This processapplies platinum particles on the reactor vessel internalsand associated piping to catalyze the reaction ofhydrogen and oxidants at surfaces to mitigateintergranular stress corrosion cracking (IGSCC). Theoriginal injection process is labor intensive and costly,and many plants experience injection line plugging,attributed to low flow of catalyst solution as it approachesthe feedwater injection point resulting in less than optimalmixing into the feedwater flow. Available data indicatethat injecting a more dilute catalyst solution morefrequently has been beneficial in mitigating monitoredcrack growth rates.Drawing on laboratory, U.S, and European OLNCexperience, Exelon and Structural Integrity Associateshave successfully demonstrated the next generation ofnoble metal injection called CNMI (Continuous NobleMetal Injection) at an operating BWR. Results, includingresponse of a newly installed reactor recirculationelectrochemical corrosion potential (ECP) flange, arepresented. Future plans are discussed for this new passiveinjection method that requires minimal interaction withplant personnel and can inject the annual allocatedamount of noble metal in a single application overapproximately 10 days, smaller amounts more frequently,or a low rate continuously throughout the cycle. Injectingplatinum passively in smaller amounts more frequently orcontinuously would renew platinum particles on surfaces,ensuring catalytic activity is maintained throughout thecycle to mitigate cracking with reduced cost, lower workload and expected lower radiation fields.