ML101830359

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June 29, 2010 Meeting Handouts
ML101830359
Person / Time
Site: Browns Ferry  Tennessee Valley Authority icon.png
Issue date: 11/18/2010
From:
Tennessee Valley Authority
To: Stewart Bailey
Plant Licensing Branch II
Bailey S , NRR/DORL,415-1321
References
Download: ML101830359 (37)
v • d • e


Text

1m TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)

License Amendment Request to Extend the Completion Time for an Inoperable Diesel Generator from 7 Days to 14 Days Rockville, Maryland June 29, 2010 1

lim Agenda

  • Introduction Terry Cribbe
  • Revised Technical Specifications (TS) Dan Green and TS Bases Changes
  • BFN Electrical System Rick Sampson
  • Closing Remarks Terry Cribbe 2

~ Revised TS and TS Bases Changes TS 3.8.1} AC Sources - Operating

  • New Proposed Required Action B.1
  • New Proposed Condition C and Required Action C.1
  • Associated TS Bases Changes
  • Questions?

3

IE] Independent Offsite Power Sources

  • Robust Offsite Power Distribution System

- Seven SOOkV Lines

- Two 161kV Lines

- Six Unit Station Service Transformers (USSTs) (2 per Unit)

- Two Common Station Service Transformers (CSSTs)

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~ Alternate Power Alignment to 4kV Unit Boards

~ Normal Power Alignment to 4kV Shutdown Boards

  • Unit 1- 4kV Unit Board Via 4kV Shutdown Bus 1
  • Unit 2 - 4kV Unit Board Via 4kV Shutdown Bus 2
  • Unit 3 - 4kV Unit Board (Direct Feed) 7

[ml Alternate Power Alignment to 4kV Shutdown Boards

  • Unit 1 - 4kV Unit Board Via 4kV Shutdown Bus 2
  • Unit 2 - 4kV Unit Board Via 4kV Shutdown Bus 1
  • Unit 3 - 4kV Unit Board (Direct Feed) 8

~ Emergency Power Alignment to 4kV Shutdown boards

~----~----------

  • The 4kV Bus Tie Board Functions as a Tie Breaker to Provide Additional Functionality (Not Credited in Accident Analysis)
  • Not Qualified 9

lim 4kV System Supplies Entire Plant

  • Safety-Related Loads - USSTs 1B, 2B and 3B
  • Non-Safety (Balance of Plant) Loads - USSTs lA, 2A and 3A 10

[ml 4kV Standby Power (If Offsite Power is Lost)

  • Unit 1 and Unit 2 Share 4 Diesel Generators (DGs)
  • Unit 3 has 4 DGs
  • Unit 3 DGs Can Be Aligned (Direct Cross-Tie) to Supply Unit 1/2 4kV Shutdown Boards (Does Not Require the 4kV Bus Tie Board)
  • Unit 1/2 DGs Can Be Aligned (Direct Cross-Tie) to Supply Unit 3 4kV Shutdown Boards (Does Not Require the 4kV Bus Tie Board) 11

um Example Unit 1 Alignment - DG A Out of Service

  • Utilize DG 3EA as Alternate Supply for 4kV Shutdown Board A via the Tie Breakers on 4kV Shutdown Board A and 3EA
  • Utilize DG 3EA as Emergency Supply to 4kV Shutdown Board A via the 4kV Bus Tie Board (Only If Options 1 or 2 Were Not Available - This Option Is Not Qualified) 12

[rnl Example Unit 2 Alignment - DG C Out of Service

  • Utilize DG 3EC as Alternate Supply for 4kV Shutdown Board C via the Tie Breakers on 4kV Shutdown Board C and 3EC
  • Utilize DG 3EC as Emergency Supply to 4kV Shutdown Board C via the 4kV Bus Tie Board (Only If Options 1 or 2 Were Not Available - This Option Is Not Qualified) 13

1m Example Unit 3 Alignment - DG 3EA Out of Service

  • Utilize DG A as Alternate Supply for 4kV Shutdown Board 3EA via the Tie Breakers on 4kV Shutdown Board 3EA and A
  • Utilize DG 3EB as Emergency Supply for 4kV Shutdown Board 3EA via the 4kV Bus Tie Board (Only If Options 1 or 2 Were Not Available - This Option Is Not Qualified) 14

Iii DG Loading

  • Load Shedding Performed As Necessary to Utilize Alternate Feeds/Alignments
  • Loading Monitored In Accordance With Operating Instructions
  • Load Restrictions, Where Necessary, On Single Line Drawings As Operating Limit (OPL) Notes
  • OPL Notes Referenced in Operating Instructions is

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Ii!i! PRA Supporting DG 14 Day Completion Time

,~----------

  • Topics Of Interest

- BFN PRA Upgrade

- Risk Insights from DG Completion Time Studies 17

Ii!i] Introd uction

_ _ _.m *

  • _
  • Unit 1 BFN PRA RISKMAN Model Updated in 2006

- Significant Findings and Observations (F&Os) Found During Peer Review

- RISKMAN Software Requires More Resources to Understand, Develop and Apply

  • PRA Upgrade Began in 2007

- Model Converted from RISKMAN to CAFTA

- Every Element of Model Re-Examined

- Peer Review of Internal Events May 2009

- Peer Review of Internal Flooding August 2009 18

lim

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Programs/Tools Used for Conversion

        • ,,~_ m _

Software Package Version Description CAFTA 5.4 Computer Aided Fault Tree Analysis System PRAQuant 5.0a PRAQuant Accident Sequence Quantification FTREX 1.4 Fault Tree Reliability Evaluation eXpert HRA Calculator 4.0 Human Reliability Analysis Calculator MAAP 4.0.5 Modular Accident Analysis Program 19

U!4! General Aspects of Upgrade

  • New CAFTA Model Integrates All Three Units

- Allows Evaluation of Risk for All Units for Outage of Common Systems, Structures, and Components

- Allows Simultaneous Update for Data

  • New Calculations Issued for All PRA Elements
  • PRA Updates Follow Industry PRA Configuration and Control Practices 20

um Initiating Events (IE)

  • 101 New Initiators Added to 3-Unit Model

- 57 Flood Initiators Replaced 7 Previously Modeled

- 3 Initiators Added for Intake Structure Plugging (1 per Unit)

- 51 Initiators Added for Various Combinations of AC and DC Electrical Board Failures

  • Initiators That Could Affect More than 1 Unit Considered
  • Previous Peer Review Findings Resolved

- Bayesian Update of Industry IE with Plant Specific Data 21

[i!i! Accident Sequences

  • IEs Grouped and Evaluated Collectively
  • Event Trees Developed for Each Accident Class (e.g.} Large LOCA} General Transient} etc.)
  • Operations Personnel Interviewed to Reflect Plant Responses 22

1m Success Criteria

  • All Success Criteria Re-Evaluated for PRA Upgrade
  • Realistic Success Criteria Established

- Existing Safety Analyses Reviewed for Applicability

- Plant Specific Thermal Hydraulic (T-H) Calculations Performed

  • T-H analyses Based on MAAP 4.0.5 runs 23

1m Systems Analysis

  • All Systems in PRA Re-Evaluated
  • Includes All Systems that are

- Required for Accident Mitigation

- Systems Supporting Accident Mitigating Systems

  • Ensured Models are Consistent With As-Built As-Operated Plant

- System Engineers Reviewed Documentation 24

1m Data Analysis

  • Freeze Date for Data was January 2008

- Bayesian Updated with Plant Specific Data

  • Unavailability Data Based on

- Maintenance Rule Data

- System Engineer/Operations Staff Estimates

  • Data Will Be Updated Every 4 Years
  • Common Cause Failures Accounted for Within Systems 25

[m! Human Reliability Analysis (HRA)

  • HRA Calculator Used to

- Document and Quantify all Independent Human Error Probabilities

- Document and Quantify Human Error Probabilities for Dependent Actions

1m Internal Flooding

  • Several Walkdowns Performed to Assess the Impact of Flooding, Spray, and Impingement
  • Peer Reviewed in August 2009
  • All Findings Resolved 27

Ii!4! Large Early Release Frequency (LERF) Analysis

  • New Containment Event Trees Developed
  • New MAAP Analyses Performed to Define Realistic LERF Sequences 28

1m Quantification

  • Single Fault Tree (for each Unit) Quantified Using CAFTA and FTREX 1.4
  • Uncertainty Analysis Performed Quantitatively Using UNCERT
  • Sensitivity Studies Performed for Significant Modeling Uncertainties 29

1m Modeling for DG Completion Time

  • Additional Initiators Added to Evaluate Fires That Could Cause Loss of Offsite Power
  • Impact of Extended DG Completion Time On All Units Evaluated for each DG 30

Summary Of Risk Impact of EDG lim (I nternal Events)

Table 4. Effect on CDF and LERF of 14-Day DG AOT Unavailability DG Using Base PRA Unavailability Case Model 14-Day AOT Change 0/0 Change U1 CDF 6.57E-06 6.67E-06 9.49E-08 1.44%

U2CDF G.B8E-06 6.95E-06 7.74E-08 1.130/0 U3CDF 7.30E-06 7.53E-06 2.29E-07 3.13%

U1 LERF 2.13E-06 2.14E-06 6.80E-09 0.320/0 U2 LERF 2.70E-06 2.71 E-06 4.90E-09 0.180/0 U3 LERF 1.01E-06 1.02E-06 5.10E-09 0.500k 31

Summary Of Risk Impact of EDG

[lID (Fire-Induced LOOP Events)

Table 5. FIVE Scenarios with Plant Response Bounded bv Loss of Offsite Power Severe Fire Area / Fire Description Fire Major Fire New Initiator Zone FreQuencv Factor FreQuency Name*

16-3 (case 2B) Control Building - 617' 4.62E-05 0.049 2.26E-06 %xlOOPFRCB (Control Room) 24 4kV Bus Tie Board Room 1.92E-02 0.10 1.92E-03 %xLOOPFRBT 25-3 (case 38) Turbine Deck 1.34E-02 0.119 1.59E-03 %xlOOPFRTD Yard Area Yard Area 5.10E-03 0.25 1.28E-03 %xLOOPFRYD (case 2)

  • There are four new fire initiators per unit (x in the Init Name = unit number) 32

Summary Of Risk Impact of EDG lim (Fire-Induced LOOP Events)

Table 6. Effect on CDF and LERF of 14-Day DG AOT Unavailability for Fires Resulting in a LOOP DG Using Base PRA Unavailability Case Model 14-Day AOT Change °/0 Change U1 CDF 1.22E-06 1.35E-OS 1.28E-07 10.44°/0 U2CDF 9.92E-07 1.08E-06 8.97E-08 9.05°10 U3CDF 2.26E-OS 2.53E-06 2.74E-07 12.14°t'o U1 LERF 2.25E-07 2.33E-07 7.95E-09 3.54°t'o U2 LERF 2.03E-07 2.08E-07 4.49E-09 2.21%

U3 LERF 1.83E-07 1.8SE-07 3.38E-09 1.85%

33

Summary Of Risk Impact of EDG

[m (Total Including Internal and Fire)

Table 7. Total Effect on CDF and LERF of 14-Day DG AOT Unavailability DG Using Base PRA Unavailability Case Model 14-Day AOT Change % Change U1 CDF 7.79E-06 8.01E-06 2.23E-07 2.86%

U2CDF 7.87E-06 8.03E-06 1.67E-07 2.12%

U3CDF 9.56E-06 1.01E-05 5.02E-07 5.26%

U1 LERF 2.36E-06 2.37E-06 1.48E-08 0.63%

U2 LERF 2.90E-06 2.91E-06 9.39E-09 0.32%

U3 LERF 1.19E-06 1.20E-06 8.48E-09 0.71%

34

1m PRA Conclusions

  • BFN PRA Model Significantly Upgraded Since 2006

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