Evaluation of Uncertainty Analysis Techniques for On-Line Sensor Calibration Monitoring and System Diagnosis

摘要

In 1998, the Electric Power Research Institute (EPRI) submitted Topical Report TR-104965, "On-Line Monitoring of Instrument Channel Performance" for NRC review. This report describes a method for monitoring the performance of instrument channels and extending calibration intervals required by plant technical specifications (TS). It presented several advantages including a reduction of intrusive, unnecessary field calibrations, the continuous assessment of instrument performance, and early instrument performance degradation detection, resulting in reduced costs, radiation exposure and increased reliability. The U.S. Nuclear Regulatory Commission (NRC) issued a safety evaluation report (SER) that concluded the generic concept of online monitoring (OLM) for calibration interval extension is acceptable and listed 14 requirements that must be addressed in plant specific license amendments. The techniques use empirical models to estimate the parameter values which are compared to the instrument outputs. The model uncertainty must be quantified when used to monitor safety-critical signals. This fact is required and strongly stated in the NRC's SER.