SENTINEL{trademark} technical basis report for Limerick. Final report

PECO Energy in cooperation with the Electric Power Research Institute (EPRI) installed the SENTINEL{trademark} software at its Limerick Generating Station. This software incorporates models of the safety and support systems which are used to display the defense in depth present in the plant and a quantitative assessment of the plant risks during proposed on-line maintenance. During the past year, PECO Energy personnel have used this display to evaluate the safety of proposed on-line maintenance schedules. The report describes the motivation for and the development of the SENTINEL software. It describes the generation of Safety Function Assessment Trees and Plant Transient Assessment Trees and their use in evaluating the level of defense-in-depth of key plant safety functions and the susceptibility of the plant to critical transient events. Their results are displayed by color indicators ranging from green, through yellow and orange to red to show increasingly hazardous conditions. The report describes the use of the Limerick Probabilistic Safety Assessment within the SENTINEL code to calculate an instantaneous core damage frequency and the criteria by which this frequency is translated to a color indicator. Finally, the report describes the Performance Criteria Assessment which tracks and trends system/train unavailability to document conformance tomore » the requirements of the Maintenance Rule.« less