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Nuclear Safety Evolution Lessons from Experience New Challenging Environment

Nuclear Safety Evolution Lessons from Experience New Challenging Environment

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Nuclear Safety Evolution Lessons from Experience New Challenging Environment

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  1. Engineering 10 Nuclear Safety EvolutionLessons from Experience New Challenging Environment José Luis Casillas - 1973 BS ME UCD 39 Years GE Nuclear Energy Chabot College E10 Guest Lecture

  2. Nuclear Safety Evolution • Objective: • Illustrate outcome in nuclear plant safety and performance when requirements shift to experience and responsibility

  3. Agenda: • Personal Background • Safety Environment Before TMI • Lessons Adopted Post TMI • Plant Performance Effects • Fukushima Earthquake Challenges

  4. Personal Background • Born in Oklahoma when father worked for Phillips 66 Oil Co. • Lived in Mexico schooling years through HS • Graduated from Delta CC in 1969, focus on the engineering specialty • Graduated from UCD in 1973, focus on thermodynamics and computer applications • Joined Nuclear Industry when expanding

  5. Safety Environment Before TMI • Regulatory: Safety requirements based on conservative estimation of prescribed events and phenomena, and acceptance criteria based on strict letter compliance. • Design: Equipment capacity and performance tuned to maximize safety margin to satisfy criteria. • Operations: Training to mitigate and support prescribed safety events.

  6. Safety Environment Before TMIConsequences • Regulatory: Compliance emphasizes checklists and reports • Design: True safety margin traded for regulatory margin • Operations: Excessive reliance in automatic systems for accidents

  7. Lessons Adopted Post TMI • Regulatory: Operators responsible for maintaining equipment performance history and anticipating potential issues, audit conformance • Design: Application of best estimate models with appropriate uncertainties and probabilities, improved real margin • Operations: Continually increase performance indicators, training for any mitigation based on realistic events

  8. Lessons Adopted Post TMIRegulatory • Plant Indicators: Established targets for plant performance including equipment challenges, recurring events, self-identification culture, etc… • Risk Based Regulation: Significance of issues addressed accordingly and prioritized • Best Estimate Models: Realistic alternate criteria for safety margins, confident upgrades

  9. Lessons Adopted Post TMIDesign • Arbitrary conservatism distorts real margin leads to unbalanced design • Rigorous uncertainties allow for best mitigation designs and operator responses

  10. Lessons Adopted Post TMIOperations • Plant safety performance continually improves across the industry, struggling units get ‘help’ • Planning and training with mockups and simulators avoid surprises • Capacity increased from 60-70% in 1970s to 90-95% in 2000s, uprate 5-20%, extension 20yr • Operations behavior regards proper safety and production risk balance

  11. Plant Performance Effects • Regulatory: Not necessarily an adversarial relationship, recognition of unique plant attributes and flexible compliance methods • Design: Focused increasingly on plant performance, modernization, power uprate and longer life preservation • Operations: Aggressively identifying early trouble indicators, actively building redundant mitigations

  12. Fukushima Challenges • Regulatory: In-Depth Safety assessments, so-called stress tests • Design: Redundancy, Reliability and Simplicity • Operations: Increased monitoring and improvement, wide contingency training

  13. BWR Evolution to Simplicity Dresden 1 KRB Dresden 2 Oyster Creek ABWR ESBWR

  14. BWR Evolution to Safety PWR Complication PWR Complication PRA of Core Damage Frequency BWR Simplification Generation III Generation II Note: PRA of CDF is represented in at-Power internal events (per year) Note: NSSS diagrams are for visualization purposes only

  15. Key Advanced Plant features Automatic scram with backup shutdown capability shutdown • Reactor depressurization capability for multiple days due to battery and pneumatic backup • Seismic Qualified AC independent water injection into core (ACIWA) • Separate and passive containment venting to prevent hydrogen explosion (COPS) Containment heat removal Core cooling • Battery and diesel flood protection for SBO mitigation • Swing Diesel Generator (air-cooled) • Backup combustion turbine (air-cooled)

  16. Severe Accident Features • Advanced plant passive features which mitigate severe accidents: • Inerted Containment • Lower Drywell flood capability • Lower Drywell special concrete & sump protection • Suppression pool - fission products scrubbing & retention • Containment overpressure protection

  17. Fukushima Earthquake…redefining the nuclear industry

  18. Tohoku Earthquake Data From USGS, Port & Airport Research Institute, EMSC, • March 11, 2011 • East of Oshika Peninsula of Tohoku, Japan • Magnitude 9.0 (on the Moment Magnitude scale) • Duration 3 to 5 minutes • Largest recorded fault movement associated with an earthquake • Fault moved 95–130 feet covering 190 miles long at a depth of 8.4 miles • Tsunami greatest height 77.4 feet • Most powerful earthquake to hit Japan • 5th most powerful earthquake in the world (since records start in 1900) • Moved Honshu 7.9 feet closer to North America • Japan’s landmass is wider than before • Earth’s axis shifted 9.8 inches • 600 million times the energy of the Hiroshima bomb

  19. Some went to watch the Tsunami Water pulled out before

  20. Some went to watch the Tsunami 56 173 Wave coming in

  21. Plant view Redline below is 150’ or 46 Meters AGL Before After

  22. Plant view Before After

  23. Fish Hatchery Before After

  24. Fish Hatchery During Tsunami

  25. Fish Hatchery After

  26. Road Damage 56 173

  27. Road Damage 56 173

  28. Tomioka the next morning Roof of Tomioka Train Station

  29. Nuclear Safety Evolution • Even in highly regulated industry such as nuclear power, effective cooperation to achieve apparent conflicting goals can lead to success for both sides. • Questions? • Thanks