Extensive Damage Mitigation Guidelines (EDMG)

Transcription

1 Extensive Damage Mitigation Guidelines (EDMG) Roy Harter RLH Global Services Regional Workshop on Sharing Best Practices in Development and Implementation of Severe Accident Management Guidelines October 3-7, 2016

2 Terrorist Attacks Impact of attack on a Nuclear Plant?? 2

3 NRC Measures Following 9-11 NRC Order EA , Section B.5.b February 25, 2002: Develop specific guidance and strategies to maintain or restore core cooling, containment, and spent fuel pool cooling capabilities Using existing or readily available resources (equipment and personnel) Implemented under the circumstances associated with loss of large areas of the plant due to explosions or fire. 3

4 NRC Order EA Phase 1 - Operational enhancements: Response to large area fires Long-term availability of makeup sources, electrical power, pneumatics Fission product scrubbing Maintaining Ultimate Heat Sink Phase 2 - Spent Fuel Pool Evaluation Phase 3 - Reactor & Containment Evaluation 4

5 B5b Phase 2 SFP Evaluations NEI 05-09, Industry Spent Fuel Pool Mitigation Strategy Study Guideline Framework to identify strategies that will mitigate the postulated effects of large fires and explosions caused by external threats to the spent fuel pool Goal is to maximize the capability provided by existing systems and identify mitigation strategies or measures using existing or readily available resources to maintain spent fuel pool cooling 5

6 6 B5b Phase 2 SFP Evaluations SFP Scenario 1: Any accessible SFP walls, penetrations, or piping that could lead to drainage below the top of the spent fuel assumed to be structurally damaged with liner failure resulting in a breach. Leakage rate from the pool is to be assumed to be 500 gpm. Mitigation should address makeup capabilities in excess of 500 gpm, accessibility for deployment of mitigation measures, and means to reduce leakage rate (e.g., plug hole). SFP Scenario 2 Accessible SFP wall is assumed to have been breached such that water level cannot be restored and the pool will be drained. Mitigation measures to be considered focus on delaying fuel damage, providing external sprays and other actions that could be taken to delay and / or reduce release of fission products.

7 7 B5b Phase 2 SFP Evaluation Process

8 8 B5b Phase 2 SFP Evaluation Process

9 9 B5b Phase 2 SFP Evaluation Process

10 10 B5b Phase 2 SFP Evaluation Process

11 11 B5b Phase 3 Evaluations Consider spectrum of enhancements to: Prevent core damage; Delay core damage; Prevent containment failure; Delay containment failure; and, Mitigate releases from Containment Identify high confidence mitigation capabilities for each safety function, either using existing plant capability or via enhancements to plant capabilities Brainstorming (Operations, Engineering, EP, SMEs, NRC) Is there is an alternate means to accomplish this function/attribute? Would this strategy be effective in a lesser damage state that may be more likely? Is there a more reliable means? Is there a more cost effective means? Is there a more effective means to envelope the necessary capabilities, even if it cost more?

12 B5b Phase 3 Key Safety Functions PWRs RCS Inventory Control RCS Heat Removal Containment Integrity Control Containment Isolation Control Release Mitigation BWRs RPV Level Control Containment Integrity Control Containment Bypass Prevention Release Mitigation 12

13 B5b Phase 3 Evaluation of Safety Function Mitigation Capability Select Safety Function Identify Primary Means & Locations Identify Alternate Means & Locations Determine Spatial Orientation vs. Primary Means In Non-Adjacent Building? Yes Next Safety Function Stage 1 Map Key Safety Functions Next Alternative No In Adjacent Building? Yes No Identify Candidate EDMG Strategies Stage 3 Identify Plantspecific Enhancements Stage 2 Evaluate Spatial Dependencies Opposite Side & Different Elevation? No Yes Yes Identify Additional Candidate Strategies No At Least One High Confidence Alternative? Assess Confidence Yes Additional Alternatives? No Yes Same Bldg., Same Side or Elev. Additional Possible RAM? No Not Spatially Separated Spatially Separated 13

14 B5b Phase 3 Approach to Evaluating Safety Function Mitigation Capability Reactor Building Mapping Scheme STAIRS TO N.W. CORNER ROOM RB757-NW S.D. Panel (above) Access Control AIR LOCK 9168 RB757-NE STAIR TO N.E. CORNER ROOM 9170 CRD REPAIR ROOM Rx Bldg Exh Vent Turbine Building Airlock N NW SW NW SW NE SE NE SE 5 = RB Fifth Floor (855') Reactor Building 5 = Fifth Floor (855') 4 = Fourth Floor (833') 3 = Third Floor (812') 2 = Second Floor (786') 1 = First Floor (757') -1 = Torus Room, Corner Rooms, HPCI, RCIC (716') RHR VALVE ROOM NW SW NE SE 4 = RB Fourth Floor (833') STEAM TUNNEL DRYWELL 9176 TIP ROOM NW SW NE SE 3 = RB Third Floor (812') 9167 R.R. Airlock AIRLOCK ELEV. STAIRS TO S.W. CORNER ROOM RB757-SW 9169 HATCH RB757-SE STAIRS TO HPCI, RCIC AND S.E. CORNER ROOM Turbine Building Airlock NW SW NW SW NW SW NE SE NE SE NE SE 2 = RB Second Floor (786') 1 = RB First Floor (757') -1 = RB Torus Room (716') RCIC Room = SW HPCI Room = SE 14

15 Extensive Damage B5b Phase 3 introduced the term Extensive Damage Used to denote the potential for spatial impacts that are quite broad Not tied to any specific threat May not only affect equipment, but may affect the ability of plant operators to monitor plant conditions and gain access to equipment in portions of the plant In addition, due to the nature of some beyond design basis threats, it possible to envision combinations of failures which might be considered of negligible probability in traditional severe accident analysis 15

16 Extensive Damage Mitigation Guidelines Purpose is to pre-think the kinds of responses that may be appropriate Two types of EDMGs Initial response (prior to establishing TSC) Longer-term response (ERO procedures after TSC staffed) Focus of initial response is stabilization of the plant until additional resources are available Longer-term actions part of a toolkit for TSC Different than SAMGs in baseline assumptions about extent of physical damage and potential availability of power and instrumentation However, in some cases, SAMG strategies may be applicable with minor adaptation 16

17 B5b Phase 2 and 3 Closure NEI 06-12, B.5.b Phase 2 & 3 Submittal Guideline describes approach to addressing the mitigating strategies committed in the industry proposal for closing Phase 2 and Phase 3 of Section B.5.b of the 2002 ICM Four components were identified for implementation at all US plants to address B.5.b Phases 2 and 3: 1. Internal SFP Makeup Strategy 2. External SFP Makeup & Spray Strategy 3. Enhanced Response Strategies for Reactor Challenges (Reactor & Containment Challenges) 4. Enhanced Initial Command and Control for Reactor Challenges All US plants implemented B5b closure actions in

18 18 Internal SFP Makeup Strategy Objective: Establish a diverse means of SFP makeup with at least a concurrent makeup capability of 500 gpm beyond the normal SFP makeup capability. Performance Attributes: Concurrent SFP makeup capability of 500 gpm is the total flow rate of water that can be simultaneously supplied to the pool beyond the normal SFP makeup capability. Can be accomplished with multiple systems beyond the normal makeup system, but all must be diverse from the normal makeup system. Engineering basis that provides reasonable assurance that the intended makeup rate and capacities can be provided. Diverse means that the makeup source does not rely upon any of the same components or piping as the normal makeup source. This includes power supplies that are located in the same building as the SFP. Example of diverse makeup source is the fire water system headers in the vicinity of the spent fuel pool with a sufficient number of fire hoses as a means to provide SFP makeup.

19 Internal SFP Makeup Strategy Require 500 gpm internal makeup from diverse (independent) sources ESW Hose Well Water via ESW Hose Fire Hoses on RB 855, 833, 812, 786, and 757 Levels Condensate SW Hoses Demin Water Hoses Spool Piece RHR RHRSW ESW Fire Water Cond SW Well Water GSW Fuel Pool Gate Shield Blocks Condensate & Feedwater RHR Core Spray CRD RHRSW ESW Fire Water Condensate SW Well Water GSW SBLC Reactor Well Spent Fuel Pool Normal SFP Makeup Source Fuel Pool Cask Storage Alternate SFP Makeup Source Skimmer Surge Tanks Condensate Service Water To RHR Fuel Pool Cooling System Additional SFP Makeup Sources During Outages with Reactor Cavity Flooded 19

20 External SFP Makeup Strategy Objective: Establish a flexible means of SFP makeup of at least 500 gpm using a portable, power-independent pumping capability Performance Attributes: Portable pumping capability sufficient to supply pool makeup directly at a rate of at least 500 gpm for each SFP Can use on-site fire truck or external portable diesel driven pump External fire protection system ring header is an acceptable water source to supply the pump, provided damage to the header and distribution piping in the vicinity of the SFP structure can be isolated Sufficient fuel for the pumping source to operate for 12 hours Sufficient water sources are available to operate the system for at least 12 hours at the flow rate anticipated to be provided Deployed within 2 hours from the time plant personnel diagnose that external SFP makeup is required 20

21 Internal SFP Makeup Strategy Fire Hose Restraint Mounted on SFP Curb 21

22 External SFP Spray Strategy Objective: Establish a flexible means of providing at least 200 gpm per unit of spray to the spent fuel pool using a portable, powerindependent pumping capability Performance Attributes: Portable pumping capability sufficient to supply one or more monitor nozzles located to spray the SFP at a flow rate of at least 200 gpm per unit Can use on-site fire truck or external portable diesel driven pump Sufficient fuel for the pumping source to operate for 12 hours Sufficient water sources are available to operate the system for at least 12 hours Deployed within 2 hours from the time plant personnel diagnose that external SFP makeup is required or 5 hours if fuel is dispersed Sufficient portable spray monitor nozzles and associated hoses to provide a spray over the entire spent fuel pool (assuming freshly discharged fuel has been distributed), best accomplished with oscillating monitor nozzle(s) 22

23 External SFP Spray Strategy Performance Attributes: Spray flows to the SFP should be maximized in the event the damage occurs prior to the recently discharged fuel being distributed External strategy must include steps to assist the plant staff in determining whether use of the external strategy in makeup mode or spray mode Can use monitor nozzles on the spent fuel pool floor to spray into the pool for situations where the pool leakage rates and plant conditions permit Capability to lift/locate the monitor nozzle such that the spray can be externally directed into the spent fuel pool (e.g., from an adjacent building roof, fire truck extension ladder). The lifting capability (e.g., crane or fire truck with extension ladder) may be located off-site as long as the site has confidence (e.g., through an MOU) that it will be available for use on-site within the required timeframe (2 hours or 5 hours). 23

24 24 External SFP Makeup Strategy

25 SFP Makeup / Spray Strategy Indication of SFP damage resulting in a large leak 1 SFP area accessible 2? Yes SFP leakage Yes Local spray Yes excessive 3? possible? No No No Makeup using available injection systems that do not require SFP access (Refer to Emergency Management Guideline) If building damage permits external spray via Aerial Ladder Truck then perform PDFP External Spray Strategy (Attachment 3) If a refuel outage is in progress then maximize spray flow Makeup using available injection systems (Refer to Emergency Management Guideline) Makeup using PDFP External Makeup Strategy (Attachment 1) SFP level still dropping? Yes If building damage permits external spray via Aerial Ladder Truck then perform PDFP External Spray Strategy (Attachment 3) If a refuel outage is in progress then maximize spray flow Deploy PDFP Local Spray Strategy (Attachment 2) If a refuel outage is in progress then maximize spray flow Notes: No Refer to Leakage Control Strategies (Attachment 4) 1. A large leak is one that exceeds available normal makeup or in which the effectiveness of normal makeup cannot be determined. 2. Accessibility can be affected by damage conditions and local dose rates. Implement strategies to contain sprays/runoff (Attachment 5) 3. Excessive leakage is a SFP leak rate estimated to be greater than 500 gpm or high dose rates indicate excessive loss of inventory. 25

26 Reactor and Containment Strategies BWR Mitigation Strategies Manual Operation of RCIC or Isolation Condenser DC Power Supplies to Allow Depressurization of RPV & Injection with Portable Pump Utilize Feedwater and Condensate Makeup to Hotwell Makeup to CST Maximize CRD Procedure to Isolate RWCU Manually Open Containment Vent Lines Inject Water into the Drywell Portable Sprays PWR Mitigation Strategies Makeup to RWST Manually Depressurize Steam Generators to Reduce Inventory Loss Manual Operation of Turbine (or Diesel)-Driven AFW Pump Manually Depressurize Steam Generators and Use Portable Pump Makeup to CST Containment Flooding with Portable Pump Portable Sprays 26

27 27 Sample EDMG Procedure

28 Command & Control Enhancements Initial Response EDMG 28 Not a new type of EOP/SAMG Intended to be used when the normal command and control structure is disabled and use of EOPs/SAMGs is not feasible Provide a bridge between normal operational command and control and the command and control that is provided by the emergency response organization Development of Initial Response EDMG: Assessment of on-site and off-site communication in light of potential damage to normal methods available to the ERO Identify methods for notifications of the utility ERO/ERO activation to mobilize additional resources to the site in a timely manner Actions needed to stabilize the situation or delay event degradation, including key mitigation strategies to help manage critical safety functions in the near term Initial damage assessment to provide the ERO with information on plant damage conditions and status

29 Command & Control Enhancements What if Control Room Command Structure is lost? 29

30 Command & Control Enhancements Initial Response EDMG Flowchart On Shift Staff Muster & Establish C&C Initial Response EDMG (3.2) & Initial Security Response 1. Notify Utility ERO 3. Notify LLEA 2. Initial Operational Actions 4. Notify Fire Dept Long-term Emergency Response 3.3/3.4 ERO Arrives at Site Specific Location and Assumes Command & Control Event Mitigation Strategies* ED Classifies and Notifies ORO and NRC Secure Site 5. Initial Damage Assessment LLEA and FD Arrive at Incident Command Post Event Mitigation * Location of strategies TBD 30

31 Closing Thoughts 31 Operations engagement and ownership is critical Technical evaluations and formal calculations must be performed to validate capabilities Verification and Validation must be performed of procedures to ensure that guidance can be followed and time limits can be met Formal training classroom, field demonstrations, and testing Equipment must be staged, strictly controlled, and periodically inspected and tested The resources of the entire Emergency Response Organization are utilized to support implementation (on-site and/or offsite) Addresses the possible short-term loss of command & control Enhanced the understanding of the challenges facing a plant under beyond design bases scenarios While there is no assurance of success under all conditions, the accident mitigation strategies provide significant enhancement beyond a plant s current capabilities more options for response