Preliminary assessment of pump IST effectiveness

A preliminary review of inservice testing (IST) effectiveness for Class 1, 2, and 3 pumps at nuclear power plants was performed. IST requirements are specified by the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section XI, and the Operations and Maintenance Standard (OM Part 6). The Institute of Nuclear Power Operations Nuclear Plant Reliability Data System was used to provide failure reports for these components from 1988 to 1992. This time frame coincides with the issuance of Generic Letter 89-04, which resulted in a more consistent application of the requirements by the licensees. For this time, 2,585 pump failures were reported. A review of these failures indicated that the majority (71.6%) resulted from external leakage. These events were excluded from the study because the typically do not affect pump operability and are not detected by the measurement of IST parameters. The remaining 733 events were reviewed to identify the primary failure causes, failure modes, and method of detection. Plant testing programs, consisting of IST, surveillance testing, detected approximately 40% of these occurrences. Others were detected through operational abnormalities, routine and incidental observations, alarms, and while performing maintenance. This paper discusses the results of the study