ML18334A216

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Presentation Slides: Exelon BWR MSIV (Boiling-Water Reactor - Main Steam Isolation Valve) Leakage Optimization for NRC Pre-Submittal Meeting of December 6, 2018
ML18334A216
Person / Time
Site: Calvert Cliffs, Dresden, Peach Bottom, Nine Mile Point, Oyster Creek, Byron, Three Mile Island, Braidwood, Limerick, Ginna, Clinton, Quad Cities, FitzPatrick, LaSalle
Issue date: 11/30/2018
From:
Exelon Generation Co
To:
Division of Operating Reactor Licensing
Haskell, R., NRR/DORL/LPL3
References
Download: ML18334A216 (21)
v • d • e


Text

BWR MSIV Leakage Optimization NRC Pre-Submittal Meeting December 6, 2018

Agenda

  • Introductions
  • Meeting Objectives
  • Project Purpose / Background Information
  • Scope of Technical Specification Changes

- MSIV Leak Rate Changes (All)

- TSTF-551 (Quad Cities, Dresden)

- Bypass Leakage (Nine Mile Point 2)

- Leakage Collection System (FitzPatrick)

  • Detailed Review of Proposed LAR Submittals

- Quad Cities and Dresden

- Nine Mile Point Unit 2

- Fitzpatrick

  • Overview of Licensing Schedule and Outage Needs
  • Summary and Wrap-up 1

Introductions

Project Manager John Massari Project Technical Lead Shane Gardner Site Licensing Lead Technical Lead Quad Cities Rebecca Steinman Jason Hawman Chong Zhou (drawdown analysis)

Dresden Mitch Mathews Dan Lee Nine Mile Point 2 Ron Reynolds Tom McMahon FitzPatrick Christian Williams Katherine Leaveck 2

Meeting Objectives

  • Present information to NRC to enable a clear understanding of the overall project and proposed site-specific License Amendment Request (LAR) submittals

- QC/DRE - allowable main steam isolation valve (MSIV) leakage rate increase and partially adopt TSTF-551

- NMP2 - allowable MSIV leakage rate increase and provision for increased Core Average Exposure (CAVEX)

- JAF - Full Alternate Source Term (AST) implementation, allowable MSIV leakage rate increase, Main Steam Leakage Collection System (MSLCS) elimination, and provision for increased CAVEX

  • Obtain feedback from the NRC on the proposed LARs to ensure high quality submittals and minimize the need for future RAIs
  • Mutual understanding of the proposed schedule and corresponding outage need date in order to ensure adequate NRC resource availability 3

2017 Benchmark of U.S. Fleet 4

Project Purpose / Background Information Optimize AST LOCA analyses to increase MSIV local leak rate testing (LLRT) limits

- Revise fleet Control Room and Offsite dose analyses to incorporate revised methods and assumptions to create margin that allows for larger bypass leakage through the MSIVs

  • Reduce outage dose and increase safety due to reducing working in challenging conditions
  • Reduce number of reportable events from MSIV LLRTs due to crediting AST revised licensing basis
  • Provide outage cost savings due to having fewer MSIV LLRT failures and resulting rebuilds

- Plants already utilizing AST will continue to follow AST as specified in Regulatory Guide (RG) 1.183, as supplemented by Regulatory Issue Summary (RIS) 2006-04

- Fitzpatrick needs to incorporate a full implementation of RG 1.183, AST, as part of this project 5

Project Purpose / Background Information (contd)

- SR 3.6.4.1.3 revision in TSTF-551 already adopted at both sites

  • Elimination of MSLCS from the FitzPatrick Technical Specifications (TS) will reduce maintenance costs and simplify the design basis dose analysis by conservatively treating MSIV leakage as ground-level release
  • License Amendment Request is required for:

- TS changes

- Planned changes in analysis methodology 6

TS MSIV Leakage Limits Current MSIV TS Limits (scfh) Target MSIV TS Limits (scfh)

Plant Line/Valve Total Line/Valve Total Quad Cities 34 86 93.6 156 Dresden 34 86 93.6 156 Nine Mile Point 2 24 N/A 200 N/A FitzPatrick N/A 46 N/A 100 NOTE: The current and target MSIV leak rate limits shown in this table are at the TS specified test pressure, which differs from site to site.

7

Scope of Technical Specifications Changes MSIV Leak Rate Changes

  • Numerical value of MSIV leakage limits in SR
  • TS 5.5 leak rate testing and control room habitability descriptions, as needed, to address methodology changes or decoupling MSIV leakage from La
  • No changes to TS 5.5.2, but will update TS Bases to reflect analysis Bypass Leakage (Nine Mile Point 2)
  • TS 3.6.1.3.11 to eliminate delayed drywell leakage (conservative change)

Leakage Collection System (FitzPatrick)

  • TS 3.6.1.8 to eliminate the specification to align with dose analysis that no longer credits the system 8

Detailed Review of Proposed LAR Submittal -

Quad Cities & Dresden New SGTS Secondary Containment Drawdown Calculation

  • RG 1.183 requirements that lead to the four cases evaluated (summer, no wind; summer, with wind; winter, no wind; winter, with wind)

- Assume ground-level release anytime Secondary Containment does not meet TS defined criteria for negative pressure

- Evaluate high wind impact on ability to maintain negative pressure

- Conservative ambient temperature assumption

  • Conservative assumptions for heat transfer, initial temperatures, heat loads, etc. within the GOTHIC model 9

Detailed Review of Proposed LAR Submittal -

Quad Cities & Dresden Revise AST post-LOCA Dose Analysis (QDC-0000-N-1481 & DRE05-0048)

  • Methodology changes:

- Credit 50th percentile aerosol settling velocity in the main steam lines

- Credit drywell spray

- Remove credit for natural iodine and particulate deposition in containment

- Credit deposition in horizontal main steam lines upstream of inboard MSIVs

- Distribute leakage equally in all of the non-failed main steams lines

- Add time dependent elemental iodine removal coefficients in the steam lines

- Reduce MSIV and containment leakage by 50% at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />

  • Input changes:

- Increase combined MSIV leakage from 150 scfh to 250 scfh (at Pa)

- Reduce control room unfiltered inleakage from 400 cfm to 250 cfm

- Remove credit for reducing La based on MSIV leakage 10

Detailed Review of Proposed LAR Submittal -

Quad Cities & Dresden Related Analysis Updates (50.59 scope)

- Updating Quad Cities TSC analysis to use AST methodology similar to that used at Dresden (i.e., LOCA model adjusted for TSC parameters)

- Details not discussed in LAR because analysis not described in the UFSAR

  • Environmental Qualification (EQ) and Vital Area (VA) Access Analyses

- Preliminary evaluation is no impact

- Per original AST approval, the existing methods are retained as TID 11

Detailed Review of Proposed LAR Submittal -

Quad Cities & Dresden TSTF-551 Proposed Technical Specification Changes

  • Add note to SR 3.6.4.1.1 NOTE: Values in brackets are Quad Cities specific, the numerical value at Dresden is 0.25.

Existing SR 3.6.4.1.1 Proposed SR 3.6.4.1.1 SR 3.6.4.1.1 Verify secondary containment SR 3.6.4.1.1 ------------------NOTE----------------------

vacuum is [0.10] inch of Not required to be met for 4 vacuum water gauge. hours if analysis demonstrates one standby gas treatment (SGT) subsystem is capable of establishing the required secondary containment vacuum.

Verify secondary containment vacuum is [0.10] inch of vacuum water gauge.

Detailed Review of Proposed LAR Submittal -

Quad Cities & Dresden MSIV Leakage Proposed Technical Specification Changes

  • SR 3.6.1.3.10 and corresponding Bases change Existing SR 3.6.1.3.10 Proposed SR 3.6.1.3.10 SR 3.6.1.3.10 Verify the leakage rate through SR 3.6.1.3.10 Verify the leakage rate through each MSIV leakage path is each MSIV leakage path is 93.6 34 scfh when tested at scfh when tested at 25 psig, 25 psig, and the combined and the combined leakage rate leakage rate for all MSIV leakage for all MSIV leakage paths is paths is 86 scfh when tested at 156 scfh when tested at 25 psig. 25 psig.
  • TS 5.5.12 - currently evaluating if La changes needed based on decoupling MSIV leakage from La 13

Detailed Review of Proposed LAR Submittal -

Nine Mile Point 2 Revise AST post-LOCA Dose Analysis (H21C-106)

  • Increase combined MSIV leakage from 96 scfh to 400 scfh; 200 scfh modeled in 2 lines
  • Adjust credit for drywell spray (reduced the time credited) and include natural deposition
  • Add time dependent elemental iodine removal coefficients in the steam lines
  • Maintain a substantial margin to the dose limits Proposed Technical Specification Changes

Detailed Review of Proposed LAR Submittal -

Nine Mile Point 2 CAVEX

  • Core burnup increased to allow margin for future core design optimization
  • AST post-LOCA dose analysis is including a new core inventory for future usage
  • Core design controls will be held to current design bases until the CAVEX change is fully implemented (under 50.59)

Related Analysis Updates (50.59 scope)

  • TSC Dose Analysis
  • Control room and SGTS filter decay heat
  • Environmental Qualification (EQ) and Vital Area (VA) Access Analyses

- Per original AST approval, these methods are retained as TID

- A few analyses depend on MSIV leak rate, will be revised and all acceptance criteria addressed

  • CAVEX Only

- Non-LOCA AST Analyses (FHA, CRDA)

- Suppression pool pH 15

Detailed Review of Proposed LAR Submittal -

FitzPatrick New AST post-LOCA Dose Analysis (Full Implementation)

  • Increase combined MSIV leakage from 46 scfh to 100 scfh; 50 scfh max per line
  • Credits changes similar to ones proposed for Quad Cities and Nine Mile Point

- Does not involve alternate collection/treatment (no condenser credit)

  • New GOTHIC based drawdown analysis Proposed Technical Specification Changes
  • TS 3.6.1.8 - eliminate to align with dose analysis that no longer credits the system
  • TS 5.5.12 - address La changes based on decoupling MSIV leakage from La 16

Detailed Review of Proposed LAR Submittal -

FitzPatrick CAVEX

  • Core burnup increased to allow margin for future core design optimization
  • AST post-LOCA dose analysis is including a new core inventory for future usage
  • Core design controls will be held to current design bases until the CAVEX change is fully implemented (under 50.59)

Related Analysis Updates (50.59 scope)

  • TSC Dose Analysis
  • Environmental Qualification (EQ) and Vital Area (VA) Access Analyses

- Very minor impacts expected to MSIV and MSLCS changes

- Will be addressed under 50.59

  • CAVEX only

- FHA (currently AST) unaffected by MSIV and MSLCS changes

- CRDA, MSLB also unaffected by MSIV and MSLCS changes

- Analyses are conservative and do not require update per RG 1.183 Section 1.3.2 17

Overview of Licensing Schedule and Outage Needs

  • Goal is to implement at first outage opportunity for each site
  • Submit LARs according to schedule outlined below
  • Request NRC review and approval in 12 months Plant LAR Submittal NRC Approval First Opportunity Quad Cities February 2019 February 2020 March 2020 Unit 2 Nine Mile Point 2 January 2019 January 2020 March 2020 Dresden September 2019 September 2020 October 2020 Unit 3 Fitzpatrick June 2019* July 2020* September 2020
  • Fitzpatrick schedule is preliminary 18

Summary and Wrap-up Summary

  • NRC approval of the increased MSIV leakage limits will:

- Reduce outage dose and increase safety due to reducing working in challenging conditions

- Reduce number of reportable events from MSIV LLRTs due to crediting AST revised licensing basis

- Provide outage cost savings due to having fewer MSIV LLRT failures and resulting rebuilds

  • NRC approval of TSTF-551 for Quad Cities and Dresden will:

- Eliminate unnecessary reporting under 10 CFR 50.72 and 10 CFR 50.73 of brief periods when secondary containment SR pressure is not met, but the safety function is maintained

  • NRC approval of elimination of MSLCS from FitzPatrick TS will:

- Provide reduced operator burden, dose, and maintenance costs

- Simplify the design basis dose analysis by conservatively treating MSIV leakage as ground-level release Recap of Actions 19

BWR MSIV Leakage Optimization DISCUSSION 20

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