Loose-parts monitoring: Present status of the technology, its implementation in U.S. reactors, and some recommendations for achieving improved performance

Abstract

At the request of the U.S. Nuclear Regulatory Commission (NRC), an assessment of the technical development status of loose-parts monitoring systems (LPMS) and their performance record to date in commercial light-water-cooled nuclear reactor plants was made during the spring of 1977, using an on-site personal interview and equipment demonstration approach. Our study revealed that while presently demonstrated LPMS technology does indeed provide a capability for detecting the presence of those relatively massive loose parts that would likely constitute a serious operational or safety hazard to the plant, it unfortunately affords little information useful to the determination of the parts' safety significance and has not yet attained the levels of sophistication and reliability ordinarily associated with safety systems. We also found a definite need for specification of the functional requirements for LPMS, in the form of a clear and comprehensive statement of NRC policy regarding the formulation and implementation of safety-oriented, yet operationally practicable, loose-parts monitoring programs for both existing and future nuclear generating stations so that overall objectives of both the utilities and the regulatory agency might be satisfied simultaneously. While it is our best technical judgment that loose-parts monitoring programs providing reliable detection (but not characterization) capabilities could be implemented with today's technology, the path on which the nuclear utility industry should proceed in order to meet NRC expectations is not completely clear. A Regulatory Guide entitled “Loose Part Detection Program for the Primary System of Light-Water-Cooled Reactors,” soon to be issued for public comment, constitutes a first step towards satisfying this need for guidance and goal establishment.