ML082030616

TVA Presentation Slides for the July 10, 2008 Meeting on COP

ML082030616
Person / Time
Site:	Browns Ferry
Issue date:	07/10/2008
From:	Tennessee Valley Authority
To:	Office of Nuclear Reactor Regulation
Brown Eva, NRR/DORL, 415-2315
Shared Package
ML082030581	List: ML082030616 ML082070290
References
TAC MD5262, TAC MD5263, TAC MD5264
Download: ML082030616 (15)

Text

Imi TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT POWER UPRATE ACRS CONTAINMENT OVERPRESSURE (COP)

Rockville, Maryland July 10, 2008

Introduction

" COP Part of BFN Current Licensing Basis for Appendix R and LOCA

• EPU Results in Additional COP need in Licensing Basis Analysis

• ACRS Concerns from Unit 1 105% Review Magnitude and duration of Appendix R event Feasibility of protecting second RHR pump Consider external initiators when using risk-informed arguments for the Appendix R COP credit Realistic long-term LOCA analysis needs to be supported by more defensible sensitivity analyses James Emens 2

Introduction Actions Taken to Address ACRS Concerns on Appendix R COP

- July 2007 meeting with NRC Staff

- Fire area analysis undertaken to compare COP needs for, realistic fire versus Appendix R analysis Deterministic analysis to provide risk insight o Submitted November 15, 2007 Followed-up with NPSH analysis for limiting cases o Submitted June 12, 2008 James Emens 3

Alternate Fire Shutdown Analysis Appendix R Rule Based Fire

- Prescribed Appendix R fire damage o Loss of all equipment not meeting generic separation criteria o Fire damage not based on analysis

- Fire damage overly conservative for many areas of the plant J. D. Wolcott 4

Alternate Fire Shutdown Analysis Fire Hazards Analysis

- Supplement to Appendix R

- Fire damage by analysis versus prescribed fire damage

- Screen based on fire protection parameters o Combustible loading o Volume of fire area o Detection/Suppression o Ignition sources

- 22/39 fire areas screened out o Fire limited to ignition source o No wide spread fire damage

- 17 fire areas screen in o Evaluated for equipment availability J. D. Wolcott 5

Alternate Fire Shutdown Analysis Equipment Availability Analysis

- All equipment in fire area assumed lost in 17 fire areas

- Unaffected equipment used per EOIs

- Offsite power credited where unaffected o BOP systems available in many areas

- 15/17 areas do not need COP o Sufficient equipment available to limit pool temperature

- Only 2 fire areas need some COP o Electrical Board Rooms J. D. Wolcott 6

Alternate Fire Shutdown Analysis e NPSH Analysis - Limiting Fire Areas

- Minimum equipment o Emergency depressurization o Reactor water level maintained with BOP o One RHR pump for containment cooling

- Pool water volume increased during event o Peak pool temperature lower o Pool level/elevation head increase

- Relaxed NPSHr based on revised vendor report o Based on shorter operating time consideration

- Termination of drywell coolers not required J. D. Wolcott 7

Alternate Fire Shutdown Analysis NPSH RESULTS

- Significant reduction in COP required o01/2psi COP o 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> duration

- Significant COP margin o Minimum 8 psi Core cooling not dependent on COP o Core cooling by BOP Systems o Defense-In-Depth consideration J. D. Wolcott 8

COP Available and COP Required Alternate Fire Hazards Analysis 30 220 Suppression Pool Temnerature 200 25 180 Cotanment 2J I

20 160 140 Atmospheric Pressure 15 120 RHR Pump Containment Pressure Required 100 10 0 10 20 30 40 50 60 Time, Hours J. D. Wolcott 9

COP Available and COP Required IM Licensing Basis Appendix R 30 220 - SuppressionPo J Temperatr 200-25 180 16 0______ P umpC ontainment 20 10Containment Pressure Pesr Required 140-15 Atmospheric Pressure 120 100 10 0 10 20 30 40 50 60 Time (hours)

J. D. Wolcott 10

Specific ACRS Recommendations IM Feasibility of Second RHR Pump for Appendix R

- Extensive resources o Physical location of switchgear o Shared electrical system o Support equipment 13 Valves/controls 0 Diesel generator/controls o RHRSW pump/valves o Significant modifications o Significant program and licensing changes

- Minimal safety benefit o Demonstrated by fire hazards analysis J. D. Wolcott 11

Specific ACRS Recommendations IIVAI

-. "I

, Consideration of External Events in Fire Risk Evaluations Fire risk insights from deterministic fire hazards analysis o Not a PRA analysis

.o Bounding fire is assumed J. D. Wolcott 12

Appendix R Conclusions

" Licensing Basis Analysis Complies With Appendix R and Demonstrates a Success Path

" COP Magnitude and Duration for Appendix R Driven by Rule Based Assumptions

" Fire Hazards Analysis Shows Reduced or No Dependency on COP J. D. Wolcott 13

Additional ACRS Issue 11VA1

• Bias and Uncertainty in Realistic LOCA

- Realistic LOCA used to build PRA model for COP

- Use of 95% non-exceedance values

- Use of probability distributions

- Use of conservative licensing basis methods

- Realistic NPSH analyses biased conservatively J. D. Wolcott 14

Closing

• Concluding Remarks James Emens 15