ML11252A006

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Dominions Slides Earthquake Response and North Anna Restart Readiness Demonstration Plan
ML11252A006
Person / Time
Site: North Anna  Dominion icon.png
Issue date: 09/08/2011
From:
Dominion, Virginia Electric & Power Co (VEPCO)
To:
Plant Licensing Branch 1
Martin R
Shared Package
ML11252A005 List:
References
FOIA/PA-2011-0357, FOIA/PA-2011-0359
Download: ML11252A006 (59)
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Text

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Dominion' Overview of08/23/1-1 Earthquake Response and Restart Readiness Demonstration Plan North Anna Power Station Units 1 and 2

Dominion' Agenda

  • Overview of Event
  • Station
  • Seismic Results
  • Restart Readiness Demonstration Plan
  • Results to Date
  • Restart Schedule
  • Summary
  • Questions 3

Dominion' Overview ofEvent Fred Mladen Director, Station Nuclear Safety and Licensing

Dominion' Overview of Event Zeus tID

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Dominion' Sequence of Events 08/23/11 13:51 :00 13:51 :11 13:51:12 13:51 :20 Both units at 100% power; U1 Turbine Driven AFW pump removed from service for scheduled surveillance test Magnitude 5.8 earthquake with epicenter near Mineral, Va.

Reactor Trip Breakers open on negative flux rate trip (Both Units Mode 3)

Transformers 1-EP-MT-1A, 2-EP-MT-1A,lB, 1C, all RSSTs, 1-EP-SST-1C and Switchyard Transformer #2 tripped due to sudden pressure relay actuations (Loss of offsite power)

All four EDGs auto start and energize their respective emergency buses 6

Dominion' North Anna Electrical Distribution System Unit 1 Station Reserve Station Unit 2 Station To To Service Transformers Service Transformers Service Transformers 4160V 4160V 22 KVl4.16 KV 34.5 KVl4.16 KV 22 KV/4.16 KV E BUS D BUS A

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A I Isl NO OSL3 NO NO 25A1 NO NO 25B1 NO NO NC NC NC 15G10 Station 15C1 Blackout Diesel NO 25B10 Gr.pNc:s Mo:. KW1121H NO I INC NC NC 25H11 Diesel NC 15J12 Diesel STUB BUS STUB BUS STUB BUS NO D

Normally Open NC D

Normally Closed 15A1 NC 15H12 NC 25J2 25J12 STUB BUS 7

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Sequence ofEvents 14:03 ALERT declared Tab HA6.1, Shift Manager judgment 14:19 1-FW-P-2 available (flowing to "A" S/G) 14:40 2H EDG manually tripped on coolant leak 2H Emergency Bus de-energized 14:55 ALERT declared Tab SA1.1 U2 AC capability reduced to a single source (21 EDG) 15:18 2H Emergency Bus re-energized by the Station Blackout (SBO) Diesel 8

Dominion Sequence of Events 17:23 Energized C RSST and F transfer bus 17:40 2J emergency bus transferred to C RSST 17:48 1H energized from F transfer bus, securing 1H EDG 20:03 B RSST energized 20: 17 A RSST energized 22:58 Offsite power supplying Emergency Busses, 3 EDGs and SBO diesel in 'Auto' and available 9

Dominion" Sequence of Events 8/24111 08:51 Commenced Unit 1 cooldown 11: 16 Downgrade to NOUE under Tab HU1.1 13: 15 NOUE terminated 13:34 Unit 1 in Mode 4, Hot Shutdown 21:26 Unit 1 in Mode 5, Cold Shutdown 10

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Sequence ofEvents 8/25/11 01:08 11:37 16:22 8/26/11 14:05 16:23 20:38 NOUE declared under Tab HU1.1(aftershock)

Commenced Unit 2 cooldown Unit 2 in Mode 4, Hot Shutdown NRC notification EP criteria seismic activity >OBE met but not declared (EAL HA6.1 versus HA1.1)

NRC notification ofpotential unanalyzed condition (DBE above 5 Hz)

Unit 2 in Mode 5, Cold Shutdown 11

Dominion*

Sequence of Events 8/28/11 15:36 NOVE terminated 9/1/11 05:18 NOVE Declared, tab RU1.1 (aftershock) 12:23 NOVE terminated 12

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Unit 1 Containment Seal Table Donlinion' Room - Excavated Section 16

Dominion' Dry Cask Storage Pad No.1

  • Largest shift was 4.5" on TN-32.21
  • No alarms were received, alarm panel test sat
  • Radiological conditions were normal
  • 6 pairs of casks <16' center to center
  • Confirmed all cask heat loads <27.1 KW, therefore, minimum 16' spacing requirement not applicable
  • Evaluating possible cask movement following aftershocks 17

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Dominion" Dry Cask Storage Pad No.2

  • NUHOMS Horizontal Storage Module
  • Gaps noted
  • Limited concrete damage (non-structural)
  • HSMs were intact and capable of performing their intended function
  • Radiological conditions were normal 20

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Dominion' Plant Seismic Instrumentation

  • The station has two separate recording systems, an active system (provided by Kinemetrics Inc.) and a primarily passive system (provided by Engdahl)
  • Both systems provide input to the Main Control Room (MeR) via a common instrumentation panel MeR Seismic Instrumentation Panel 26

Dominion' Plant Seismic Instrumentation

  • Kinemetrics
  • Triaxial Seismic Trigger
  • Triaxial Seismic Switch
  • Triaxial Time History Accelerograph
  • Engdahl
  • Triaxial Response Spectrum Recorder
  • Triaxial Peak Accelerograph 27

Plant Seismic Instrumentation Dominion' (Kinemetrics - Active)

Triaxial Time History Accelerograph Triaxial Seismic Trigger Triaxial Seismic Switch Triaxial Time History Accelerograph Unit 1 Containment 216' Unit 1 Containment 216' Unit 1 Containment 216' Unit 1 Containment 291' U 1 Containment Mat U 1 Containment Mat U 1 Containment Mat U 1 Containment Operating Deck 28

Plant Seismic Instrumentation Dominion' (Engdahl - Passive)

Sensor Type Location/Elevation Unit 1 Containment 216' Triaxial Response Spectrum Recorder Unit 1 Containment 231 '

Triaxial Response Spectrum Recorder Triaxial Response Spectrum Recorder Aux Building 244' Triaxial Response Spectrum Recorder Aux Building 274' Triaxial Peak Accelerograph Unit 1 Containment 218'

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Triaxial Peak Accelerograph Unit 1 Containment 241' Triaxial Peak Accelerograph Aux Building 279' Equipment Mounting Unit 1 Containment Mat Unit 1 Residual Heat Removal (RHR) pump and heat exchanger area In between Unit 1 and Unit 2 Component Cooling (CC) pumps Near Unit 1 "A" CC heat exchanger On Unit 1 "C" Safety Injection Accumulator discharge piping On Unit 1 "B" RHR heat exchanger On Unit 1 "A" CC heat exchanger, 29

Dominion' Triaxial Response Spectrum Recorder Triaxial Response Spectrum Recorder Recorder Scratch Plates Styluses Recorder Scratch Plates 30

North Anna Design Basis Seismic Criteria Dominion' (Station and ISFSI)

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II II OBE 0.06 0.04 0.09 0.06 II DBE 0.12 0.08 0.18 0.12 31

Comparison of Kinemetrics Data Dominion' Horizontal Direction Kinemetrics Data for Containment Basemat - Horizontal Direction 0.800 0.700 I

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Comparison ofKinemetrics Data Dominion' Vertical Direction Kinemetrics Data for Containment Basemat - Verticalj Direction 0.5 0.45 0.4 0.35 0.3 5%OBE RCBase mat - Vert

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Dominion-Cumulative Absolute Velocity (CAV)

  • Concept used by EPRI to address OBE Exceedance in 1988 (EPRI NP-5930)
  • Indicator of damage based on analysis of 263 time-histories from 42 earthquakes
  • Criterion is conservative and has a minimum factor ofthree Revision 3 Rev. 234

DominicHr Plant Seismic Response Results East-West N orth-South Vertical I

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(g-sec)

Kinemetrics 0.137 0.175 0.118 SGH 0.118 0.169 0.105 Bechtel 0.134 0.181 0.113 Average 0.130 0.175 0.1 12 (CA V limit== 0.16 g-sec, per NRC RG 1.166) 35

Husid Function Plot - Representation of Dominion" Cumulative Energy 0.014 Cumulative Energy for Records Labeled "CW026" 0.012 0.010

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8 10 Time (sec) 12 CW026_CH2_V_corrected 14 16 18 CW026_CH3_T_corrected 20 Cumulative Energy (HUSID Plot) for the Containment Basemat Records Effective Strong Motion Duration for Records Labeled "CW026" Effective Strong Motion Time History Duration (sec)

CW026 CH1 L corrected 3.1 CW026_CH2_V_corrected 1.5 CW026_CH3_T_corrected 1.0 36

Dominion' Seismic Margin As part of response to GL 88-20 (IPEEE) and GL 87-02 (USI-A46 ),

the following actions were completed:

  • With few exceptions, components evaluated could withstand 0.3g or higher
  • Worst case capacity ofO.16g, which exceeds 0.12g DBE
  • Modifications provided additional seismic ruggedness
  • Comprehensive peer review walkdown of 20% sample Consequently, safe shutdown components are capable of surviving seismic accelerations in excess of the DBE design criteria 37
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' Domin.' Restart Readiness Demonstration Plan North Anna UFSAR - Section 3.7.4.6 Use ofData from Seismic Instrumentation - In accordance with paragraph Yea) ofAppendix A to 10 CFR 100, an orderly and sequential shutdown of the North Anna units will be carried out according to detailed written station procedures if a seismic event with vibratory ground motion equal to or exceeding that ofthe operational-basis earthquake occurs. Prior to resuming operations, it will be demonstrated to the NRC that no functional damage has occurred to those features necessary for continued operation without undue risk to the health and safety of the public, or that the necessary repairs to those features have been completed. [emphasis added}

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Dominion' Restart Readiness Demonstration Plan Based on exceeding the station OBE and DBE seismic criteria and the CAV limit, the station restart readiness assessment actions were based on the guidance contained in the following documents:

  • RG 1.166, Pre-earthquake Planning and Immediate Nuclear Power Plant Operator Post-earthquake Actions, dated March 1997
  • RG 1.167, Restart ofa Nuclear Power Plant Shut Down by a Seismic Event, dated March 1997
  • EPRI NP-6695, Guidelines for Nuclear Plant response to an Earthquake, dated December 1989 40

Dominion" EPRI NP-6695 Figure 3-1 No Yes Immediate Immediate Operator Operator Actions Actions Operator Evaluation of Operator Evaluation of Walkdown Ground Motion Walkdown Ground Motion Inspections Records Inspections Records Continue Post-Trip Operation Inspections Review Normal Restart Sshutdown Figure 3-1. Flow Diagram of Short-Term Actions 41

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EPRI NP-6695 Figure 3-2 Note; These actions are performed only if OBE is exceeded or damage found Figure 3-2. Flow Diagram of Post-Shutdown Inspections and Tests 42

Dominion" EPRI NP-6695 Figure 3-2 Note:

These actions are performed only if aBE is exceeded or damage found Figure 3-2. Flow Diagram of Post-Shutdown Inspections and Tests 43

Dominion EPRI NP~6695 Figure 3-2 Note:

These actions are performed only if OBe is exceeded or damage found Figure 3-2. Flow Diagram of Post-Shutdown Inspections and Tests 44

Dominion* Restart Readiness Demonstration Plan

  • Seismic Data Collection and Analysis
  • Damage Assessment and Evaluation
  • Restart Assessment
  • Long-Term Actions 45

Dominion' Restart Readiness Demonstration Plan Seismic Data Collection and Analysis

  • Perform data collection/analysis of earthquake seismic data to quantitatively define earthquake magnitude - Complete
  • Compare results with the station design basis OBE and DBE criteria to determine if they were exceeded - Complete
  • Obtain 3rd party peer reviews of analysis by industry experts 46

Dominion' Restart Readiness Demonstration Plan Damage Assessment and Evaluation

  • Perform post-earthquake walkdowns/inspections of plant structures, systems and components (SSCs) consistent with regulatory and industry guidance (includes North Anna Spillway dam and SG tube inspections)
  • Perform comprehensive surveillance testing to validate SSC operability/performance
  • Perform comprehensive inspections and evaluations of ISFSI pads and casks
  • Perform evaluations of reactor vessel internals and fuel in the core, Spent Fuel Pool and New Fuel Storage Area
  • Document assessments/evaluations in appropriate engineering technical evaluations 47

Dominion* Restart Readiness Demonstration Plan Restart Assessment

  • Complete inspections, evaluations, testing and repair, if necessary, of SSCs to ensure they are capable of performing their intended design functions
  • Finalize and obtain FSRC review and approval of Engineering technical documents demonstrating SSC restart readiness
  • Review and disposition open Condition Reports, as necessary, to ensure that no outstanding issues exist that would preclude restart 48

Dominion' Long -Term Actions

  • Installation of free-field seismic instrumentation
  • Permanently re-power Seismic Monitoring Panel in MCR from an Uninterruptible Power Supply
  • Coordinate update ofthe station seismic design and licensing bases with ongoing GI -199 resolution effort 49

Dominion' Results to Date Although evaluations are continuing, to date, SSCs inspections have only identified superficial damage and Surveillance Tests have not identified any safety-related SSC operability issues related to the seismic event

  • Inspector Training and Inspection Process
  • Inspection results indicate North Anna in the "0" category of the EPRI Damage Intensity Scale
  • Asof9/7/11
  • 82% of 134 system inspections completed
  • 97% of 141 structure inspections completed
  • 28% of 448 Surveillance Tests completed (Unit 1)
  • 20% of 50 High Confidence Low Probability of Failure (HCLPF) component SQUG inspections completed 51

Dominion' 09/07 09/16 09/18-20 09/22 NAPS VI Restart Timeline Facility Safety Review Committee (FSRC) approval of Safe Shutdown System Operability Determination Engineering Final Technical Evaluation review by FSRC Comprehensive ESF functional testing complete Comprehensive post-event testing and inspections complete Start-up Assessment by FSRC Containment close-out complete and unit ready to enter Mode 4 53

Dominion' 09/07 09/12 09/12-15 09/15-17 09/16 09/17-30 10/01-02 10/02-06 10/06-13 10/13 NAPS U2 Planned Refueling Restart Timeline FSRC approval ofthe Safe Shutdown System OD FSRC approval ofthe Mode 6 System OD Reactor Disassembly-Inspections Reactor Core Off-load to the SFP Secondary activities complete Engineering Final Technical Evaluation review by FSRC Defueled Primary Maintenance Reactor Core Reload Reactor Reassembly Comprehensive ESF functional testing complete Comprehensive post-event testing and inspections complete Containment close-out complete Start-up Assessment by FSRC Ready for Mode 4 54

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Dominion' Summary

  • OBE and DBE criteria were exceeded; however, CAV calculations indicate that significant damage would not be expected
  • Extensive actions are underway to inspect, evaluate, test and repair, if necessary, SSCs to ensure they are capable ofperforming their required design basis functions - Results are confirming the CA V expectations
  • To date, no safety related S SCs have been identified that require repair
  • IPEEE and USI-A46 results demonstrate that safe shutdown SSCs are capable ofwithstanding peak accelerations in excess ofDBE
  • Unit will be ready for restart when we establish confidence that SSCs will perform as designed
  • Long-term actions are planned to improve plant seismic monitoring capability and to re-evaluate plant OBE and DBE criteria in conjunction with resolution of GI -199 56

Dominion' List of Acronyms AC Alternating Current AFW Auxiliary F eedwater DBE Design Basis Earthquake EAL Emergency Action Level EDG Emergency Diesel Generator EP Electric Power or Emergency Plan EPRI Electric Power Research Institute ESF Engineered Safety Features FSRC Facility Safety Review Committee FW Feedwater GI Generic Issue HSM Horizontal Storage Module IPEEE Individual Plant Examination External Events KW Kilowatts MT Main Transformer NRC Nuclear Regulatory Commission NOVE Notification of Unusual Event NUHOMS Nuclear Horizontal Modular Storage System OBE Operating Basis Earthquake OD Operability Determination P

RSST SBO SGH SFP SSC SST TN Ul U2 USI Pump Reserve Station Service Transformer Station Blackout Simpson Gumpertz & Heger Spent Fuel Pool Systems, Structures and Components Station Service Transformer Transnuclear Unit 1 Unit 2 Unresolved Safety Issue 58

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