Preliminary assessment of pump IST effectiveness

A preliminary review of Inservice Testing (IST) effectiveness for Code Class 1, 2, and 3 pumps at nuclear power plants was performed. IST requirements are specified by ASME Section XI, and the Operations and Maintenance Standard (OM Part 6). The INPO NPRDS database was used to provide failure reports for these components for 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 period, 2585 pump failures were reported. A review of these failures indicated that the majority (71.6%) were due to external leakage, and were excluded from this study since these events typically do not affect pump operability and are not detected by the measurement of IST parameters. Of the remaining 733 events, a review was performed to identify the primary failure causes, failure modes, and method of detection. Plant testing programs, consisting of IST, surveillance testing, and special testing, detected approximately 40% of these occurrences. Others were detected through operational abnormalities, routine and incidental observations, alarms, and while performing maintenance. This paper provides a discussion of the results of the study