Application of the UMAE Methodology for the Uncertainty Evaluation in Support to the EOP Background Analysis

Validation of EOPs (Emergency Operating Procedures) relies on the best-estimate analysis of the transient scenarios. In order to cover associated uncertainties, usually limited number of sensitivity studies is performed for the development of the EOPs in order to identify possible plant states and associated parameters relevant for operator actions. Recently, developed methodologies for the uncertainty evaluation made it possible to evaluate directly uncertainties with the respect to the scenarios analyzed. UMAE (Uncertainty Methodology based on Accuracy Extrapolation) uncertainty methodology has been applied for development of function restoration EOPs. More specifically, Inadequate Core Cooling (ICC) LOCA (Loss of Coolant Accident) scenario has been analyzed using best estimate transient analysis code RELAP5/SCDAPSIM code. Time window for successful operator action has been evaluated following 4.0^″ cold leg break near the Reactor Pressure Vessel (RPV) in a 2-loop PWR plant.