1 RIC 2009 MELCOR Analyses to Address Regulatory Issues: Evaluation of System Success Criteria Hossein Esmaili USNRC March 12, 2009

2 MELCOR Modeling Approach Auxiliary Building Safeguards Building Containment Reactor w/ RCS Generic Models (no “built-in” nodalization) Building block approach (more flexibility =>greater user responsibility)

3 Design Certification ESBWR US APWR Westinghouse AP-1000 US EPR Severe accident response and source term Containment response to design basis accident

4 Success Criteria Application Staff Identified Inconsistencies in Similar-Plant SPAR Model Success Criteria for Currently Operating Reactors Use MELCOR for Thermal-Hydraulic Analysis –Surry (PWR) and Peach Bottom (BWR) models from State-of-the- art Reactor Consequence Analysis (SOARCA) –Definition of core damage (e.g., 2200 F) –Code calculations for various scenarios to define success criteria Collaborative Effort –Project Management: Don Helton –Calculation Matrix: Don Dube, Rick Sherry, et al. –Systems Analysis Support: Don Marksberry –MELCOR Analysis: Hossein Esmaili –SPAR Model: Pete Appignani, INL

5 Surry Calculation Matrix Small LOCA dependency on sump recirculation –Effect of sprays on RWST depletion –Does the system depressurize (and how fast)? Feed & Bleed PORV success criteria –Combination of HHSI and PORVs Steam Generator Tube Rupture –Multiple tube ruptures –Impact of secondary cooling, HHSI, forced cooldown Station blackout –Investigating time available for A/C power recovery –Both small and large RCP leaks with and without TD-AFW Accumulator injection –Spectrum of LOCA sizes –Availability of HHSI/LHSI in conjunction with number of accumulators

6 Peach Bottom Calculation Matrix SRV/RCIC –Can RCIC maintain cooling until low pressure system injects? Station blackout (RCIC/HPCI availability) –Investigating time available for A/C power recovery –Suppression pool heatup and pump NPSH limit RCIC HPCI

7 Concluding Remarks Application of MELCOR to Obtain Consistent System Success Criteria for Representative PWR (Surry) and BWR (Peach Bottom) Plants Use the Thermal-hydraulic Results to Develop a More Extensive Technical Basis for the SPAR Models Possible Extension to Other Plants (e.g., ice condenser) as Input Models Become Available

8 Acronyms A/CAlternating Current HHSIHigh-Head Safety Injection HPCIHigh Pressure Coolant Injection LHSILow-Head Safety Injection LOCALoss-of-Coolant Accident NPSHNet Positive Suction Head PORVPower (or Pilot) Operated Relief Valve RCICReactor Core Isolation Cooling RWSTRefueling Water Storage Tank SGTRSteam Generator Tube Rupture SPARStandardized Plant Analysis Risk SRVSafety Relief Valve TD-AFWTurbine-Driven Auxiliary Feedwater