Loose-part monitoring programs and recent operational experience in selected US and western European commercial nuclear power stations

Technical personnel at thirteen nuclear power stations (ten in the US and three in Western Europe) were interviewed during the summer of 1983 to ascertain their collective experience with acoustic-based loose-part monitoring systems (LPMSs). Subjects receiving special attention were the number and location of sensors (accelerometers) required to reliably detect and locate loose parts in both pressurized- and boiling-water reactors; detection sensitivity to loose objects in both primary and secondary coolant loops; false alarm experience; calibration procedures; day-to-day monitoring system operation; premature failure of in-containment components of the LPMS caused by hostile environments; and overall success to date in detecting the presence of potentially damaging loose parts and in assessing their operational and safety implications. The individual utilities' responses to questions addressing these and other issues are provided, along with the author's summary and interpretation of what the information gathered means in a collective sense, that is, a viewpoint of the present state of application of loose-part monitoring technology in this selected set of commercial nuclear plants. It is concluded that the technology of loose-part detection and assessment is moving slowly toward increased acceptance by the utility industry but, at the same time, the full potential benefits of loose-part monitoring systems are not presently being realized and, furthermore, probably will not be unless actions are taken in four recommended areas