IAEA-J4-TM TM for Evaluation of Design Safety

Transcription

1 Canadian Nuclear Utility Principles for Beyond Design Basis Accidents IAEA-J4-TM TM for Evaluation of Design Safety Mark R Knutson P Eng. Director of Fukushima Projects Ontario Power Generation

2 Overview of Presentation Canadian Nuclear Utility Principles for Beyond Design Basis Events 1 Objective 9 Principles Supporting actions planned or taken by the utilities Our Commitment Summary 2

3 Canadian Nuclear Utility Principles for Beyond Design Basis Events Developed and agreed to by the 3 Utilities Provide guidance for utility decision making to maintain consistency Intended to position Canadian utilities at the forefront of the Post Fukushima Response 3

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5 Objective of the Principles Practically eliminate the potential for societal disruption due to a nuclear incident by maintaining multiple and flexible barriers to severe event progression 5

6 Principle 1 Event Progression Defences Actions and defences will focus on stopping accident progression prior to a severe accident. Maintaining adequate fuel cooling prevents fuel failures. Severity of consequences escalates with event progression. Prevention should receive the majority of the actions and focus from the utilities. 6

7 Principle 1 - OPG Event Progression Defences Actions Robustness of OPG stations confirmed for beyond design basis (BDB) seismic events BDB wind analysis completed for Pickering 5-8 and Darlington Resulted in revisions to P5-8 Emergency Operating Procedures BDB wind analysis in-progress for Pickering 1-4 TCD Dec 31, 2013 BDB flooding analysis completed for Pickering and Darlington Installed flood barriers around essential systems at both sites 7

8 Principle 2 Multiple Barriers Multiple barriers to event progression and multiple means to supply water or electricity will be used to ensure adequate defence 8

9 Principle 2 - OPG Multiple Barriers Actions Procured diesel driven pumps and generators Sufficient number (N+1) of pumps and generators to supply all units at a site simultaneously Multiple different connection points Design in progress to simplify connections 9

10 CANDU 10

11 Principle 3 Early Fuel Cooling Methods and actions to initiate heat transport system (HTS) cool-down and maintain fuel cooling will be a primary and early priority Rapid cooldown is achieved by opening Steam Release Valves (SRVs) Increases margin to fuel failures (lower temperature). Allows for EME to inject additional water into a depressurized steam generators. Actions to open SRVs need to be simple and reliable. 11

12 Principle 3 - OPG Early Fuel Cooling Actions Design Seismic capacity of Class II battery banks Portable Uninterruptable Power Supplies (PUPS) Procedures Load shedding strategies Training Initiation of early cooldown of the HTS 12

13 Principle 4 Containment Integrity Actions to maintain Containment integrity will be utilized to minimize radioactive releases Control pressure Containment Cooling Containment Venting (Principle 5) Control hydrogen Minimize generation Effective removal Control water inventory to minimize flooding Water injection and recovery 13

14 Principle 4 - OPG Containment Integrity Actions Design Larger generators as part of Phase 2 EME to repower most Emergency Power System loads, including, Vault and boiler room air cooling units (condense steam) Post Accident Containment Filtered Venting System Emergency Water Systems to cool safety-critical loads Reactor water recovery and recirculation 14

15 Principle 4 - OPG Containment Integrity Actions Design (continued) Water make-up to moderator and shield tank to arrest accident Provide fuel cooling Minimize generation of hydrogen Shield tank integrity assessed for severe accidents Additional shield tank overpressure relief committed for Darlington Current overpressure relief confirmed adequate for Pickering Additional filtered venting system (beyond phase 2 EME) Committed as part of Darlington refurbishment Under evaluation for Pickering Passive Autocatalytic Recombiners for hydrogen removal 6 of 10 Units complete 15

16 Principle 4 - OPG Containment Integrity Actions Procedures Severe Accident Management Guidelines developed Training Improved through multiple iterations Classroom Practice deploying actual EME equipment SAMG Drills with EME deployment 2 one-day drills for each of PA and PB in two-day drill planned for Darlington (August 2013) 16

17 Principle 5 Filtered Venting Containment venting will be controlled through a filtered system With a functional containment, decisions can be made when to vent and for how long. Controlled filtered venting will minimize radioactive releases and their potential impact on the environment. The ability to delay when containment will be vented allows for short lived material to be reduced through decay. 17

18 Principle 5 OPG Filtered Venting Actions Both Pickering and Darlington have Post Accident Containment Filtered Venting Systems Repowered as part of Phase II EME Additional filtered venting capacity to be installed as part of Darlington Refurbishment. Pickering is under review, decision by end of Post accident procedures are available and trained 18

19 Principle 5 OPG Filtered Venting Actions Installed near boundary automated gamma monitoring at Pickering and Darlington Provide early indication of impact of venting 19

20 Principle 6 Equipment Integrity Necessary systems, structures and components will be confirmed to survive rare yet credible conditions for external hazards Review Level Conditions (RLCs) established for rare yet credible conditions. e.g., seismic Design Basis ~1,000 yr; RLC ~10,000 yr Provides assurance that the EME will meet its objectives for Beyond Design Basis Events 20

21 Principle 6 OPG Equipment Integrity Actions Seismic Margin Assessment completed: Passive water supply to Steam Generators (Dearator) Class II batteries and rack EME Quick connects designed to meet system requirement Analyzed impact of seismically induced fires and floods at Pickering and Darlington. No significant incremental impact on station risk. Instrumentation and Equipment Survivability Assessment is in progress for Pickering and Darlington Diversity and independence of EME connection points included in plan to address extreme external hazards. 21

22 Principle 7 Spent Fuel Cooling Irradiated Fuel Bay (IFB) water levels will be maintained sufficiently above the top of the fuel to mitigate high radiation fields, hydrogen production, and fuel damage The time required to respond to a loss of IFB cooling is typically quite long. The volume of water in the IFB should be maximized within normal water levels to the extent practicable. EME to supply water to account for leakage and steaming. 22

23 Principle 7 OPG Actions IFB time to boil > 72 hrs EME deployment time < 4 hours Procedures developed for EME deployment Seismic / Thermal Analysis confirmed leakage plus evaporation << EME water make-up capacity Design in progress for portable measurement of level and temperature 23

24 Principle 8 Readily Deployed Emergency Mitigating Equipment will be robust, readily available, easily deployable within required timeframes, and have adequate redundancy Stored at higher elevation, away from station, close enough for timely deployment and accessible following BDBE Pre-staging is an option for predictable events (e.g., severe weather) Deployable by diverse work groups, supported by procedures, training and practice and validated by drills More than one method for deployment (trucks, tractors, security vehicles) Reliability of EME supported by using proven technology, preventative maintenance and routine testing On-site fuel supplies adequate for > 72 hour run time, with provisions for refueling in place. 24

25 Principle 8 OPG Readily Deployed Actions 25

26 Principle 8 OPG Readily Deployed Actions 26

27 Principle 8 OPG Readily Deployed Actions 27

28 Principle 9 - Common Philosophy Canadian utilities will utilize a common philosophy for the prevention of a Beyond Design Basis Accident (BDBA) Interaction between utilities gives a larger perspective and experience base Encourages challenging and learning Improves capability to respond and to provide mutual assistance Provides credibility Facilitates regulatory concurrence. 28

29 Principle 9 - Common Philosophy Actions COG - Candu Industry Integration Team Bi-weekly domestic meetings Monthly CNO meetings Quarterly international meetings COG Severe Accident Joint Project Technical Reports Shutdown and Low Power Multi-unit Station Technical Basis Document and SAMG Update Containment Integrity In-Vessel Retention Instrument Survivability Habitability 29

30 Principle 9 OPG Common Philosophy Actions COG Emergency Preparedness Work Shop III June 3&4, Diverse participation including CNSC, Health Canada and provincial agencies. WANO SOER 13-2 corrective action plans Developed cooperatively WANO Peer Review at Pickering June Strength awarded for Fukushima response. Mutual Aid Agreement in effect Regional Emergency Response Support Centre Conceptual design report under review 30

31 Our Commitment We are committed to these principles in order to protect against Beyond Design Basis Events such as the one that occurred at Fukushima 31