ELECTROCHEMICAL MEASUREMENTS AND MODELING PREDICTIONS IN BOILING WATER-REACTORS UNDER VARIOUS OPERATING-CONDITIONS

One important issue for providing life extension to operating boiling water nuclear reactors (BWRs) is the control of stress corrosion cracking in all sections of the primary coolant circuit. This paper links experimental and theoretical methods that provide understanding and measurements of the critical parameter, the electrochemical potential (ECP), and its application to determining crack growth rates among and within the family of BWRs. Measurement of in-core ECP required the development of a new family of radiation-resistant sensors. With these sensors, ECPs were measured in the core and piping of two operating BWRs. Concurrent crack growth measurements were used to benchmark a crack growth prediction algorithm with measured ECPs. Future studies obtaining in situ crack growth measurements with measured and calculated ECPs are necessary to increase both capability and confidence in using the predictive approach. The modeling of the concentration of potential-determining species in various parts of the BWR coolant circuit has been accomplished. Theoretical and experimental investigations are underway to relate these local chemistries to ECP and subsequent crack growth.