PWR Power Shape Monitoring System (PWR-PSMS): Volume 2, Benchmark report: Final report

The Power Shape Monitoring System (PSMS) is a computer system for on-line monitoring and prediction of reactor cores. It can be used for real-time monitoring of the core power distribution and the margin to the limiting value of the Departure from Nucleate Boiling Ratio (DNBR), load-following core performance analysis, and predictive analysis. The heart of the PSMS consists of a nodal code (NODEP-2/THERM-P) that computes the 3-D core power distribution. This code is coupled to a simplified nodal version of the COBRA-IIIC/MIT-2 thermal-hydraulic model to determine the DNBR. Activation of the calculations and review of the results is through user-friendly interactive software that can be tailored to the requirements and capabilities of the different categories of users through table-driven menus. The PSMS can be adapted to PWRs developed by any of the three PWR vendors in the US; however, from the technical point of view, the most difficult problem is associated with monitoring plants without fixed in-core neutron detectors. It has been demonstrated that adaptation of the nodal code to partially fit the available in-core detector readings, followed by a statistical characterization of the remaining errors, results in better accuracy and improved sensitivity for anomaly detection compared to an approach that is entirely dependent upon the detector readings. The approach has been carefully benchmarked to Movable In-Core Detector (MID) readings from two plants and also Fixed In-Core (FIC) readings from one plant. The computed power distribution at steady state, high power conditions normally has an uncertainty of about 3% for the nodal power and 2% for the bundle power