TESTING DEFICIENCIES IN AUXILIARY FEEDWATER SYSTEMS

The Phase I Auxiliary Feedwater System Aging Study, NUREG/CR-5404-V1, focused on how and to what extent the various auxiliary feedwater (AFW ) system component types fail, how the failures have been and can be d etected, and the value of current testing requirements and practices. This follow-on study, which will be provided in full in NUREG/CR-5404- V2, provides a closure to the Phase I Study. For each of the component types and for the various types of component failure identified in th e Phase I Study, the methods of failure detection were designated and tabulated, and the following findings became evident: Instrumentation and control (I&C) related failures dominated the group of failures tha t were detected during demand conditions. Many of the potential failur e sources not detectable by the current monitoring practices were rela ted to the I&C portion of the system. Some component failure modes are actually aggravated by conventional test methods. Several important s ystem functions did not undergo function verification test. The goal o f this follow-on study was to categorize and evaluate the deficiencies in testing identified by Phase I and to make specific recommendations for corrective action. In addition, this study presents discussions o f alternate, state-of-the-art test methods and provides a proposed AFW pump test at normal operating pressure, which should do much to verif y system operability while eliminating degradation.