Ansaldo Nucleare at CPExpo 2013: Emergency electrical power supply to nuclear safety systems

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Emergency electrical power supply to nuclear safety systems, Design Basis and lesson-learned from Fukushima accident” …

Emergency electrical power supply to nuclear safety systems, Design Basis and lesson-learned from Fukushima accident”
Corrado Alessandroni - Ansaldo Nucleare

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  • 1. Emergency electrical power supply to nuclear safety systems: Design basis and lesson learned from the Fukushima accident Corrado Alessandroni Licensing and Safety Technical Advisor Ansaldo Nucleare Genova , 30 Ottobre 2013
  • 2. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: What’s occurred at Fukushima FUKUSHIMA DAI-ICHI March 11th, 2011 What’s occurred to the Electrical Power Supply Systems
  • 3. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: What’s occurred at Fukushima FUKUSHIMA DAI-ICHI March 11th, 2011  Hour 14.46: massive earthquake (magnitude 9.0) which induced onsite seismic accelerations above design values  Loss of normal electrical power supply caused by the earthquake  Reactor SCRAM in the three units in operation (of six located onsite)  Electrical power supplied by the emergency diesel generators (EDGs) that started as designed  Hour 15.30: an earthquake induced Tsunami struck the site: waves up to 14 ÷ 15 m height flooded the major buildings (tsunami barriers where designed for 6 m wave height protection).  Loss of 12 out of 13 EDGs located onsite – the survived EDG was servicing the Units 6  Massive damage of electrical panel boards
  • 4. CP EXPO 2013 Genova , 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: What’s occurred at Fukushima Path of inundation Ref. A One-year Review of Fukushima Daiichi Nuclear Power Station “Steps to Achieve Stabilization” March 2012
  • 5. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: What’s occurred at Fukushima FUKUSHIMA DAI-ICHI Ref. Special Report on the Nuclear Accident at the Fukushima Daiichi Nuclear Power Station – INPO 11-005 November 2011
  • 6. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: What’s occurred at Fukushima Ref. A One-year Review of Fukushima Daiichi Nuclear Power Station “Steps to Achieve Stabilization” March 2012
  • 7. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: What’s occurred at Fukushima Fukushima Daiichi Electrical Distribution Damage Ref. Special Report on the Nuclear Accident at the Fukushima Daiichi Nuclear Power Station – INPO 11-005 November 2011
  • 8. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: What’s occurred at Fukushima Ref. Fukushima Nuclear Accident Analysis Report (Interim Report) – Tokyo Electric Power Company, Inc. December, 02nd 2012
  • 9. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: What’s occurred at Fukushima Ref. A One-year Review of Fukushima Daiichi Nuclear Power Station “Steps to Achieve Stabilization” March 2012
  • 10. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: What’s occurred at Fukushima Post-accident recovery actions to restore the electrical power supply  No written emergency procedures to face the severe accident situation  Restoration of external power supply impossible due to the massive damage induced on transmission lines by the earthquake  Vehicles batteries instrumentation secured on-site were collected to power monitoring  about 6 hours after the initiating event, batteries were connected to power reactor water level indicator at Unit 1  Acquisition of power supply cars and further batteries from outside     power supply cars started to arrive onsite on 11th March evening-night; about 50 mobile electric-generators were onsite on 12th March morning; connection difficulties due to the massive damaged of the electrical panels; first connection was made ​in the afternoon of 12th March (15.30) about 25 hours after the earthquake and about 18 hours from the arrival of the first power supply car;  it was decided to use fire engines and motor driven pumps to cool reactors trough injection of sea water due to the impossibility to restore power to plant safety systems.
  • 11. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: What’s occurred at Fukushima Ref. Fukushima Nuclear Accident Analysis Report – Tokyo Electric Power Company, Inc. June, 20th 2012
  • 12. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: EPS Design Bases EMERCENCY POWER SYSTEM (EPS) Design Bases
  • 13. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: EPS Design Bases  System definition EPS includes: 1. Electric power supply sources: Electric Generators (typically DieselGenerator) and Batteries 2. Electric power distribution system  Functions Provide power supply to plant components assuring safety functions under all design basis conditions where the normal power supply is not available. The fundamental safety functions are: 1. 2. 3. Shutdown of the nuclear chain reaction Nuclear fuel cooling and decay heat removal Containment of radioactive releases
  • 14. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: EPS Design Bases  System Design Bases  Separation from the normal power supply system of the plant: Defense-in-Depth Principle  Component redundancy : Application of the Single Failure Criterion  Redundant components separation : protection against from common cause failure (fire, flooding, internal missiles etc.)  Environmental qualification: P,T, humidity and radiation associated also to accidental conditions  Protection / Qualification against design basis External Natural Phenomena (Earthquake, Flooding, Tornado etc.) and Man-made External Events (Aircraft Impact, Explosion etc...)  Component safety classification commensurate with the importance of the safety functions to be performed  Application of Codes and Standard for the design, fabrication, erection, testing and operation commensurate with the importance of the safety functions to be performed  Reliability requirements for emergency diesel generators (0,95-0,975 per demand for each EDG - US NRC Reg.Guide 1.155 «Station Blackout»)  Quality assurance  Inspection and Testing Program during operation – Program surveilled by the Safety Authority (Individual Plant Technical Specification)
  • 15. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: EPS Design Bases  REGULATIONS and STANDARDS  International (IAEA, IEC, ISO)  IAEA Safety Standard Series NS-G-1.8 Design of Emergency Power Systems for Nuclear Power Plants  National (Regulatory Guides,IEEE, RCC-E, KTA, …)  Generation III Light Water Reactors: Utilities Requirements  EUR Requirements Document (Europe)  EPRI Utility Requirements Document (USA and other countries)
  • 16. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: EPS Design Bases U.S. STANDARDS - IEEE Standards for Safety Systems and Components (IEEE Class 1E Items) Power, Instrumentation and Control Portion of Safety Systems IEEE Std 603 Criteria for Safety Systems for NPGSs -------------US NRC Reg. Guide 1.153 Power Systems Protection System IEEE Std 308 US NRC Reg.Guide 1.32 IEEE Std 279 US 10CFR50 and SRP Ch.7 • • • • • Post-Accident Monitoring System IEEE Std 497 US NRC Reg.Guide 1.97 System Design Basis System Design Criteria Sense and Command Features Requirements Execute Features Requirements Power Sources Requirements Digital Computer Systems ANSI/ANS IEEE Std 7-4.3.2 Single Failure Criterion Periodic Testing IEEE Std 379 US NRC Reg.Guide 1.53 IEEE Std 338 US NRC Reg. Guide 1.118 Independence and Separation Environmental and Seismic Qualification IEEE Std 384 US NRC Reg.Guide 1.75 IEEE Std 323 – IEEE Std 344 – IEEE Std 627 US NRC Reg Guide 1.89 and 1.100
  • 17. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: EPS Design Bases U.S. STANDARDS -IEEE Standards for Safety Systems and Components (IEEE Class 1E Items) Examples of Specific Standards for equipment-apparatus • • • • • System Design Basis System Design Criteria Sense and Command Features Requirements Execute Features Requirements Power Sources Requirements  IEEE Std. 387 – Criteria for Diesel-Generator Units Applied as Standby Power Supplies for Nuclear Power Generating Stations (US NRC Reg. Guide 1.9);  IEEE Std. 485 - Recommended Practice for Sizing of Lead-Acid Batteries for Stationary Applications (US NRC Reg. Guide 1.212);  IEEE Std. 572 - Qualification of Class 1E Connection Assemblies for Nuclear Power Generating Stations (US NRC Reg. Guide 1.156);  ……
  • 18. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: After Fukushima AFTER FUKUSHIMA
  • 19. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: After Fukushima INTERNATIONAL INITIATIVES  Stress Tests: European Union  EU Council of 24/25 March, 2011, requested that the safety of all EU nuclear plants should be reviewed  31st May 2011: ENSREG issued EU Stress Tests Specifications  June 2011: all the operators of nuclear power plants in the EU started safety reassessments on the basis of ENSREG Specifications    November 2011: NPP Operators Final Reports to National Safety Authorities December 2011: National Reports by Safety Authorities April 2012: Peer Review Report by the Task Force setup by ENSREG and EU Council with experts from all EU countries. August 2012: ENSREG Action Plan to follow-up the implementation of the peer review recommendations   Post-Fukushima Task Force and Action Plan: USA     July 2011 Document with Near-Term Task Force (NTTF) recommendations (SECY-11-0093): NTTF conducted a review of the NRC regulations and processes in light of the events at Fukushima determining additional improvements to be made September 2011 Selected recommendations to be taken without delay (US NRC SECY-11-0124) October 2011 NTTF Recommendations Prioritization and Action List (US NRC SECY-11-0137) March 2012 Approval of the first three orders to Plant Operators (SECY-12-0025)
  • 20. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: After Fukushima ACTIONS  Reassessment of the Design Basis External Events with updated methodologies and data  Definition of Beyond Design-Basis External Events Mitigation Strategies.  Scenario: loss of electrical power and ultimate heat sink affecting all units at a site simultaneously  Goal: prevent fuel damage in the reactor and spent fuel pool with simultaneous actions on all units at site
  • 21. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: After Fukushima Mitigation Strategies– Phased Approach (rif. NEI 12-06 Maggio 2012 – Diverse Flexible Coping Strategies –FLEX- Implementation Guide) Phase 1- Initial Phase: use of installed equipment and resources to maintain or restore nuclear safety functions  most of the existing NPPs are already equipped to manage a total loss of AC power (external grids + diesel generators) for few hours (typically 4-6 hours) - Station-Blackout scenario  disconnect not-vital electrical loads to extend power sources duration Phase 2-Transition Phase: provide sufficient, portable, onsite equipment and consumables to maintain or restore the nuclear safety functions until they can be accomplished with resources brought off site (for roughly 24 hours) Phase 3 - Final phase : obtain sufficient offsite resources to sustain those functions indefinitely
  • 22. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: After Fukushima Elements of the Mitigation Strategy  Portable equipment that provides means of obtaining power and water to maintain or restore key safety functions for all reactors at a site This could include equipment such as portable pumps, generators, batteries and battery chargers, compressors, hoses, etc.  Reasonable staging and protection of portable equipment and associated transportation routes The equipment used for mitigation would be staged and reasonably protected from applicable site-specific severe external events to provide reasonable assurance that N sets of equipment will remain deployable following such an event (N is the number of NPP Units on site).  Portable equipment connections qualified-protected to timely supply power to vital loads and provide water to cool down the nuclear fuel in reactors and spent fuel pools  Procedures and guidance to implement mitigations strategies to be integrated in the Plant Operating Procedures (AOP)  Personnel Training  Programmatic controls that assure the continued viability and reliability of the mitigation strategies. These controls would establish standards for quality, maintenance, testing of FLEX equipment, configuration management and periodic training of personnel..
  • 23. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: After Fukushima
  • 24. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: After Fukushima Post-Fukushima – ANN Service Products ELECTRICAL FLEXIBLE CONNECTIONS for off-site mobile equipment “Plug and Socket” to the Electrical Distribution System, at different voltage levels (medium up to 11 kV, low up to 400 V) FULLY QUALIFIED/PROTECTED 6KV SWITCHBOARDS Possible cross-links for safety electrical power loads 6 kV from any operable emergency diesel generator • • • • identification of emergency electrical loads; installation of circuit breakers allowing for fast load transfer, isolation of not emergency loads and connection of emergency power source; update of the existing distribution network, to respect all the duplication and segregation requirements ; electrical cabinet design and qualification process; DIVERSE AND PROTECTED STAND-BY DIESEL GENERATOR STATIONS Diverse and protected (external events) diesel generator stations to be installed at NPP site
  • 25. CP EXPO 2013 Genova, 30 Ottobre 2013 Emergency electrical power supply to nuclear safety systems: Design Basis and lessonlearned from Fukushima accident: After Fukushima Thanks for your attention