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 approachmore » 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.« less