2. PSA Methodology- Level1 PSA overview - Procedure Initiating Events Quantification Event Trees CDF • Uncertainty analysis • Sensitivity analysis • Importance Factor ・Accident Sequences ・Success Criteria • Selection • Quantification Fault Trees • System Design • Technical Specifications • Operating Procedures • Human Reliability • Component Failure Data CDF: Core Damage Frequency
2. PSA Methodology- Level1 PSA overview (cont.) - Event Trees Initiating Events Fault Trees CDF Quantification average Failure Probability
2. PSA Methodology- Initiating Events - Categorized mainly into 2 groups ; LOCAs and transients - Small LOCA, - Medium LOCA - Large LOCA LOCAs - Turbine Trip - Other Transient Transients YES PCS Available YES - MSIV Closure - Loss of Condenser Vacuum - Loss of Feed Water Off Site Power Available NO YES RCS Integrity NO - Loss of Offsite Power NO - Spurious Open of SRV Initiating event frequency is evaluated based on operating experiences.
2. PSA Methodology- Event Tree Analysis - Example of Event Tree (Large LOCA) HPCF LPFL Scram Success Fail CD : Core Damage
2. PSA Methodology- Success Criteria - • Criteria for Core Damage: • Peak Cladding Temp. 1200C “Thermal-hydraulic Analysis” to confirm “minimum combination” of mitigation systems to satisfy the criteria Start to Core Cooling 1200℃ PCT Water Level Time Time