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RIC 2009 MELCOR Analyses to

Address Regulatory Issues: Evaluation of System Success Criteria

Hossein Esmaili

USNRC

March 12, 2009

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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)

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Design Certification

ESBWR

US APWRWestinghouse AP-1000

US EPR

• Severe accident response and source term • Containment response to design basis accident

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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

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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

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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

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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

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Acronyms • A/C Alternating Current• HHSI High-Head Safety Injection• HPCI High Pressure Coolant Injection• LHSI Low-Head Safety Injection• LOCA Loss-of-Coolant Accident• NPSH Net Positive Suction Head• PORV Power (or Pilot) Operated Relief Valve• RCIC Reactor Core Isolation Cooling• RWST Refueling Water Storage Tank• SGTR Steam Generator Tube Rupture• SPAR Standardized Plant Analysis Risk• SRV Safety Relief Valve• TD-AFW Turbine-Driven Auxiliary Feedwater