ML110490251

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Presentation Slides for 2-21 Public Meeting W/Nrc & Exelon Re Peach Bottom Proposed Actions to Address Containment Accident Pressure (CAP) Credit
ML110490251
Person / Time
Site: Peach Bottom  Constellation icon.png
Issue date: 02/18/2011
From:
Exelon Nuclear
To:
Office of Nuclear Reactor Regulation
Hughey J, NRR/DORL, 301-415-3204
Shared Package
ML110490209 List:
References
TAC ME5267, TAC ME5268
Download: ML110490251 (21)
v • d • e


Text

NRC Public Meeting Peach Bottom Proposed Actions to Address Containment Accident Pressure (CAP) Credit 02/22/11

Exelon Confidential and Proprietary 2

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Agenda

Introductions

Meeting Purpose ECCS Pump NPSH:

Current Licensed CAP Credit

Preliminary Results / Impacts / Margins Proposed Modifications to Address CAP Next Steps

Exelon Confidential and Proprietary 3

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Meeting Purpose

Familiarize Staff with Proposed Approach for Addressing Containment Accident Pressure Credit in Support of EPU

  • Proposed Modifications that would eliminate the need to request additional CAP credit

Proposed Modifications impact on existing CAP Credit

  • Preliminary results, expected outcomes, and plant and operational impacts

Discuss Next Steps

Exelon Confidential and Proprietary 4

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ECCS Pump NPSH DBA-LOCA CLTP with CAP ECCS Pump Maximum SP Temperature (F)

Minimum Containment Pressure Available, MCPA (psig)

Containment Overpressure Required, COPR (psig)

NPSH Margin =

MCPA - COPR (feet)

CS - ST 149 7.0 0.0 16.2 RHR - ST 149 7.0 0.6 14.8 CS - LT 206 7.0 4.8 5.4 RHR - LT 206 7.0 6.1 2.1 No CAP with modifications (preliminary data - analyzed at 120% OLTP)

ECCS Pump Maximum SP Temperature (F)

NPSHA @ Max.

SP Temp. (feet)

NPSHR 3%

(feet)

NPSH Margin =

NPSHA - NPSHR3% (feet)

CS - ST 155 34.0 28.0 6.0 RHR - ST 155 32.1 26.8 5.3 CS - LT 185.3 26.0 21.3 4.7 RHR - LT 185.3 23.8 16.0 7.8

Exelon Confidential and Proprietary 5

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ECCS Pump NPSH Special Events (Non-Design-Basis)

CLTP with CAP Event - Pump Maximum SP Temperature NPSH Basis (F)

Containment Pressure, CP (psig)

COPR (psig)

NPSH Margin =

CP - COPR (feet)

SBO - RHR 190 4.6 2.1 6.0 ATWS - RHR 190 4.6 2.1 6.0 App. R - RHR 206 6.9 5.8 2.6 No CAP with modifications (preliminary data - analyzed at 120% OLTP)

Event - Pump Maximum SP Temperature (F)

NPSHA @ Maximum SP Temperature (feet)

NPSHR 3%

(feet)

NPSH Margin =

NPSHA - NPSHR3%

(feet)

SBO - RHR 196.0 19.5 16.0 3.5 ATWS - RHR 168.3 30.8 16.0 14.8 App. R - CS 196.4 21.9 21.3 0.6 App. R - RHR 204.3 16.5 16.0 0.5

Exelon Confidential and Proprietary 6

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Proposed Changes to Address CAP ECCS Pump NPSH - Events Proposed Changes DBA-LOCA Short-Term (first 10 minutes)

Reduce RHR runout flow rate by adding hydraulic resistance DBA-LOCA Long-Term (beyond 10 minutes)

RHR HX cross-tie modification

Increase RHR HX performance (reduce fouling)

Decrease RHR flow rate

NPSHR 3% curves Station Blackout (SBO)

Increase RHR HX performance (reduce fouling)

Decrease RHR flow rate

NPSHR 3% curves

Credit CST as suction source for RCIC pump ATWS (Peak Pool Temperature)

Increase SBLC Boron Enrichment

Increase RHR HX performance (reduce fouling)

Decrease RHR flow rate

NPSHR 3% curves Appendix R

Increase RHR HX performance (reduce fouling)

Decrease RHR flow rate

NPSHR 3% curves

Increase/Supplement CST Inventory

Exelon Confidential and Proprietary 7

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ECCS Pump NPSH Core Spray - no modifications

RHR Pump (LPCI) - Runout Flow Rate: Current analysis requires CAP (from 7.5 to 10 minutes)

  • Current:

12,000 gpm

  • Post Mod:

10,600 gpm (adjust limit stops to increase HX inlet MOV hydraulic resistance)

Margins at 10 minutes (maximum pool temperature = 155F):

  • RHR (LPCI) pumps at 10,600 gpm (runout): 5.3 feet (18.6F)
  • Core Spray pumps at 4,030 gpm (runout): 6.0 feet (20.5F)

DBA-LOCA Short-Term (1st 10 minutes)

Exelon Confidential and Proprietary 8

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ECCS Pump NPSH Core Spray - no modifications, no new operator actions

RHR Pump (LPCI) - Core and Containment Cooling Analysis Flow Rate:

  • Current:

10,000 gpm

  • Post Mod: 8,600 gpm (analysis value - operators maintain flow within 8,600 - 10,600 gpm range in accordance with EOP NPSH curves)

Margins at peak pool temperature, 185.3F:

  • RHR (LPCI) pumps at 8,600 gpm (throttled): 7.8 feet (15.6F)
  • Core Spray pumps at 3,125 gpm (throttled): 4.7 feet (9.9F)

DBA-LOCA Long-Term (beyond 10 minutes)

Exelon Confidential and Proprietary 9

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Results / Margins Peak Suppression Pool Temperatures Post Mod Current

(@120% OLTP)

DBA-LOCA Short-term 150F 155F Long-term 206F 185F PCT (2200F limit)

Small-break 1865F 1904F*

Large-break 1653F <1700F*

EDG electrical loading Remains within 2000 hour0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> rating EDG E2 0-10 minute loading - restored to within 2000 hour0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> rating

  • PBAPS remains small-break LOCA limited. Large break PCT is affected by LPCI flow rate reduction, but small-break LOCA remains limiting.

Exelon Confidential and Proprietary 10 10 10 RHR HX Cross-tie Modification Concept Suppression Pool 24" Pipe 24" Pipe RHR Pump A

RHR Pump C

20" Pipe 20" Pipe RHR HX C

RHR HX A

A C

B New pipe U2 HPSW Pumps 039A 034A To LPCI D

Div I Div II FE Proposed Additions M

New MOV 2344 M

M M

Existing Wall 00B062 To 3344 20A015 20B010 20B036 20A017 20B012 20B038 M

M M

154A 089C M

089A M

20X030 20X032 EDG E1 EDG E3 C

A From 20B011 Existing Wall U3 HPSW Pump Room 00B061 FE FE New MOV Remove Orifice

Exelon Confidential and Proprietary 11 11 11 RHR HX Cross-tie Modification Concept

Cross-tie RHR pump discharge lines in the same division:

  • 1 normally closed cross-tie MOV controlled from control room
  • 2 normally open manual isolation valves in cross-tie piping
  • 1 Throttling valve (MOV controlled from control room) in RHR supply line to each HX
  • Approx. 25 - 30 ft. pipe for cross-tie line
  • Flow elements with instruments - indicate RHR flow in control room (RG 1.97)

Containment cooling capability increased approximately 164% of existing capability

Exelon Confidential and Proprietary 12 12 12 RHR HX Cross-tie - Operations Impact

Impact to Operators - New Operator Actions

  • Start 1 additional HPSW pump within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />
  • Open MOV to establish HPSW flow through 2nd HX
  • Open new cross-tie MOV within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />
  • Split RHR flow equally to 2 HXs within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />

Exelon Confidential and Proprietary 13 13 13 RHR HX Cross-tie - Tech Spec and Bases

Spec 3.6.2.3 RHR Suppression Pool Cooling (Two Loops)

  • LCO requires 2 Operable subsystems. Each subsystem consisting of 1 RHR pump and associated HX
  • Currently 4 subsystems available to meet LCO
  • With modification, an Operable subsystem will require 1 RHR pump, the cross-tie, and both HXs
  • Post modification, 2 subsystems will be available meeting the LCO requirement.

Bases definition of subsystem Operability will be modified to reflect new configuration

Spec 3.7.1 High Pressure Service Water (Two Loops)

  • LCO requires 2 Operable subsystems. Each subsystem consisting of 1 HPSW pump and associated HX
  • Currently 4 subsystems available to meet LCO
  • With modification, an Operable subsystem will require 2 HPSW pumps and 2 HXs
  • Post modification, 2 subsystems will be available meeting the LCO requirement.

Bases definition of subsystem Operability will be modified to reflect new configuration

Spec 3.5.1 ECCS Surveillance

  • Cross-tie Hx MOVs increase hydraulic resistance and limit runout flow
  • SR to demonstrate adequate LPCI flow will be changed to reflect new analytical assumptions

Exelon Confidential and Proprietary 14 14 14 Proposed SBO Solution

Proposed Changes

  • Increase RHR HX performance (reduce fouling)
  • Decrease RHR pump flow rate (consistent with LOCA)
  • NPSHR 3% curves
  • Eliminates Operator Action of Swapping Suction Source to Pool

- modifications ensure CST remains available as RCIC suction source Results:

Maximum suppression pool temperature: 196F

RHR pump NPSH margin at maximum suppression pool temperature: 3.5 feet (6.2F)

Exelon Confidential and Proprietary 15 15 15 Proposed ATWS Solution

Proposed Changes

  • Increase SBLC Boron Enrichment

Achieves shutdown sooner thereby lowering pool temperature

  • Increase RHR HX performance (reduce fouling)
  • Decrease RHR pump flow rate (consistent with LOCA)
  • NPSHR 3% curves Results:

Maximum suppression pool temperature: 168.3F

RHR pump NPSH margin at maximum suppression pool temperature: 14.8 feet (33.9F)

Exelon Confidential and Proprietary 16 16 16 Proposed Appendix R Solution Appendix R - 4 Fire Safe Shutdown (FSSD) Methods All FSSD Methods end with RHR aligned in Alternate Shutdown Cooling (ASDC)

RHR aligned to RPV through LPCI injection valve or CS aligned to RPV through CS injection valve RPV water level above main steam lines ADS SRV open to provide flow path back to suppression pool Method Mitigating System(s)

A RCIC B

HPCI C

Low Pressure ECCS

Core Spray Available (CS (RPV inventory) and RHR in torus cooling )

Core Spray Not Available (only RHR credited)

D Shutdown from Outside the Control Room - HPCI

Exelon Confidential and Proprietary 17 17 17 Proposed Appendix R Solution Proposed Changes

  • Increase RHR HX performance (reduce fouling)
  • Decrease RHR pump flow rate (consistent with LOCA)
  • NPSHR 3% curves
  • Changed operator response time
  • Supplement CST inventory
  • Credit Refueling Water Tank volume
  • Modifications to ensure suction source (CST) remains available
  • Raise Torus high-level suction swap-over setpoint Results:

Maximum suppression pool temperature: 204.3F

RHR pump NPSH margin at maximum suppression pool temperature: 0.5 feet (0.7F)

Appendix R PCT remains below 1500F limit

Exelon Confidential and Proprietary 18 18 18 Summary - Addressing CAP

CAP Credit for DBA-LOCA and Special Events Can be Eliminated Through:

  • Modifications to

Increase RHR HX capacity

Reduce RHR flow rate

Increase SBLC enrichment

Credit additional CST inventory

  • Improved RHR Hx performance
  • Use of NPSHR 3% curves

Exelon Confidential and Proprietary 19 19 19 Next Steps

Conduct Follow-up Meeting

  • Further discussion and feedback regarding proposed solutions to CAP credit
  • Discuss need to address CAP solutions as part of EPU application

Exelon Confidential and Proprietary 20 20 20 Supplementary Information

Exelon Confidential and Proprietary 21 21 21 ECCS Pump NPSH CS & RHR NPSH Ratio vs. Time DBA-LOCA using RHR HX Cross-tie (1st 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) 0.70 0.80 0.90 1.00 1.10 1.20 1.30 1.40 1.50 1.60 1.70 1.80 1.90 2.00 2.10 2.20 2.30 2.40 2.50 0.00 5.00 10.00 15.00 20.00 25.00 Time (hours)

NPSH Ratio (NPSHA/NPSHR3%)

CS NPSH Ratio Based on NPSH3R%

RHR NPSH Ratio Based on NPSHR3%

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