Advanced Nondestructive Examination Technologies for Alloy 600 Components

Several pressurized water reactors have experienced primary coolant leaks as a result of degradation in the tubes and J-groove welds of reactor vessel head penetrations. Leakage has been attributed to primary water stress corrosion cracking (PWSCC) of the Alloy 600 nozzle material and Alloy 182/82 weld materials. More recently, other Alloy 600 components including reactor vessel bottom mounted instrumentation nozzles, dissimilar metal pipe welds, hot leg instrument penetrations, and pressurizer heater sleeves have exhibited degradation. Westinghouse has been actively involved in the development of a comprehensive Alloy 600 degradation management program including investigation of root cause, establishing a safety position, and developing inspection and repair/replacement strategies to address Alloy 600 degradation issues. Personnel from Germany, Sweden and the United States have cooperatively developed equipment and nondestructive examination technologies for identification and characterization of degradation that might exist in these Alloy 600 components and attachment welds. These developments represent significant enhancements to technologies and equipment previously available in the industry and are driven by the need to meet new inspection applications and industry requirements which have continued to evolve over the last several years. This paper describes the inspection capabilities available to support Alloy 600 degradation management programs, field experience with those inspection technologies, and the status of ongoing NDE development efforts to enhance future Alloy 600 inspection programs.