D. W. Mitchell

This report provides key results of a 30-month experimental research and development project to identify and quantify the effects of normal aging on the performance of nuclear safety-related resistance temperature detectors (RTDs). The limit for initial accuracy of RTD elements was established and the range of their response time was determined. Seventy-two representative nuclear-grade RTDs were tested for calibration drift at simulated reactor conditions and for shelf-life drift. This included a number of naturally aged RTDs received from nuclear power plants. The authors demonstrate that periodic calibration and response time testing performed once every fuel cycle is a reasonable approach for managing the aging of nuclear grade RTDs.

This report provides key results from a 30-month research and development project to study the effects of normal aging on the calibration and response time of nuclear plant pressure, level, and flow transmitters and to develop and validate new methods for testing the performance of the transmitters as installed in nuclear power plants. The project focused on aging tests of complete transmitter assemblies and critical transmitter components; testing the effects of sensing-line length, blockages, and voids on pressure sensor response time; investigating the oil loss phenomenon in Rosemount and other transmitters; validating new methods for on-line testing of pressure transmitter response time; investigating on-line detection of oil loss in Rosemount transmitters; and analyzing Licensee Event Report and Nuclear Plant Reliability Data System databases for pressure sensor failures in nuclear power plants. The authors demonstrated that the practice of response time testing and calibration once every 18 to 24 months is adequate for managing the normal aging of pressure transmitters.