OPERATIONAL DECISION ALTERNATIVES IN FAILURE SITUATIONS OF STANDBY SAFETY SYSTEMS - DEVELOPMENT OF PROBABILISTIC APPROACH AND PC PROGRAM TERELCO

The TeReLCO software package provides advanced tools for the risk based evaluation of alternative test and repair arrangements and limiting conditions for operation in standby safety systems. The methodological key features include event sequence modeling by use of an Event Sequence Diagram incorporating imbedded state submodels, This enhances the modeling of operational dependences over phased missions, recovery paths and other types of time dependences. Several risk variables related to the operational alternatives and problem resolution are quantified: risk frequency, cumulative risk over predicted or given scenario, expected risk over given scenario or plant lifetime. These are graphically displayed to enhance comparisons and sensitivity considerations.