ML16194A006

Pre-Application Meeting Presentation Regarding LaSalle County Station License Amendment Request for Revision of Suppression Pool Swell Design Analysis

ML16194A006
Person / Time
Site:	LaSalle
Issue date:	07/12/2016
From:	Simpson L Exelon Generation Co
To:	Bhalchandra Vaidya Plant Licensing Branch III
Vaidya B, NRR/DORL/LPL3-2, 415-3308
References
CAC MF8063, CAC MF8064
Download: ML16194A006 (12)

Text

LaSalle County Station Pre-Application Meeting License Amendment Request for Revision of Suppression Pool Swell Design Analysis July 15, 2016

Exelon Representatives

• Vikram Shah - LaSalle Deputy Engineering Director

• Matthew Chouinard - LaSalle Design Engineer

• James Patterson - LaSalle Design Engineer

• Guy Ford - LaSalle Regulatory Assurance Manager

• Lisa Simpson - Exelon Corporate Licensing Engineer 1 LaSalle Pre-Application Meeting - License Amendment Request to Revise Suppression Pool Swell Design Analysis

Agenda

• Meeting Objectives

• Background

• Issue Overview

• License Amendment Request Need for Amendment Technical Evaluation

- Summary

- Discussion 2 LaSalle Pre-Application Meeting - License Amendment Request to Revise Suppression Pool Swell Design Analysis

Meeting Objectives

• Present information to NRC describing a proposed License Amendment Request (LAR) to revise the suppression pool swell design analysis at the LaSalle County Station

• Engage the NRC in an open and transparent dialog regarding the proposed approach to identify technical and regulatory areas that warrant additional discussion such that they may be satisfactorily addressed in the LAR prior to submittal

• Answer questions and obtain feedback from the NRC on the proposed LAR approach and content 3 LaSalle Pre-Application Meeting - License Amendment Request to Revise Suppression Pool Swell Design Analysis

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Background===

• Suppression Pool Swell Phenomena Design Basis Accident Loss of Coolant Accident (DBA LOCA) occurs Air & Steam discharged to suppression pool through downcomers Large bubble forms at downcomer exit Expanding bubble causes suppression pool water to swell up

• Design Analysis

- Determines impact and drag loads on components located in suppression pool and suppression chamber

- Verifies components design margin 4 LaSalle Pre-Application Meeting - License Amendment Request to Revise Suppression Pool Swell Design Analysis

Issue Overview

• LaSalle suppression pool swell calculation contains non-conservative mass and energy release Analysis uses improper reactor water temperature

• Non-conforming condition is subject of Operability Evaluation OE 12-003

• Consequences of correcting the non-conservative mass and energy release Increases impact and drag loads associated with the suppression pool swell phenomena Increased loads affect systems, structures, and components (SSCs) in suppression chamber (e.g., piping and supports) 5 LaSalle Pre-Application Meeting - License Amendment Request to Revise Suppression Pool Swell Design Analysis

Issue Overview Previously NRC Mark II BWROG Full Scale Mark II Unknown Pool Mark II Requests Program Consists NRC Review JAERI Testing Pressure Hydrodynamic BWROG Mark II of Analytical Tasks Documented Performed Suppression Loads Established Owners for & Experimental NUREG 1980-1981 Containment (Including to Address Info Re: Tests. Results 0487 Design Suppression NRC Design Issued in 1978-1981 Developed Pool Swell) Concerns Adequacy NEDO-21061P NRC Eval 1958-1962 Discovered 1975 1975 1975-1981 Documented 1972-1974 NUREG 0808 1981 GE Determined S&L Analyzed Sub Cooling Concern with GE GE Revised Due to Concerns Re: New GE LaSalle LaSalle for Analysis Identified Containment Results Upon Swell Loads, Containment Suppression Analysis S&L Performed Analysis Response Pool Swell Addressing Removing Conservatism Mods Implemented including 3C7-1075-001 Concern 3C7-0781-001 To Accommodate Swell Loads Suppression 1975-1981 1977 (Suppression Pool Swell AOR)

Pool Swell

Conclusion:

Existing Suppression Pool Swell Analyses acceptable 1983 6 LaSalle Pre-Application Meeting - License Amendment Request to Revise Suppression Pool Swell Design Analysis

License Amendment Request - Need for Amendment

• Changes in methodology to be included in LAR submittal:

1) The analysis of record (AOR) conservatively uses downcomer vent flow consisting of air; the new analysis initially uses air flow and transitions to a realistic air/steam mixture

2) The new analysis uses the GEH TRACG computer code to determine break mass and energy release

3) The new analysis does not account for vent back pressure for drywell pressurization

4) Calculated suppression pool swell velocity profile modified to meet the NRC acceptance criteria for swell height 7 LaSalle Pre-Application Meeting - License Amendment Request to Revise Suppression Pool Swell Design Analysis

License Amendment Request - Technical Evaluation Composition of the Downcomer Vent Flow Effluent New analysis initially uses air only flow (until the air mass contained in the non-submerged portion of the downcomer vents is purged) and then uses a realistic air/steam mixture.

• Although the amount of air in the mixture decreases following the LOCA, the new analysis conservatively uses a constant drywell air/steam fraction following vent clearing

• Drywell air/steam fraction use is conservative to the values documented in NUREG-0487, Supplement 1

• The use of an air/steam mix better represents DBA LOCA conditions (i.e., more realistic) as shown by testing 8 LaSalle Pre-Application Meeting - License Amendment Request to Revise Suppression Pool Swell Design Analysis

License Amendment Request - Technical Evaluation

• The new analysis uses TRACG to determine break mass and energy release TRACG has been used for mass and energy release by other licensees and accepted by the NRC

• The new analysis does not account for vent back pressure for drywell pressurization

- Accepted approach referenced in NUREG-0487, Supplement 1

• Calculated suppression pool swell velocity profile modified to meet the NRC acceptance criteria for swell height The calculated swell height is less than the NRC acceptance criteria; therefore, the swell velocity profile is stretched 9 LaSalle Pre-Application Meeting - License Amendment Request to Revise Suppression Pool Swell Design Analysis

Summary

• NRC approval of the new Suppression Pool Swell Design Analysis will:

- Enable resolution of a non-conforming condition to full qualification

- Support closeout of open Operability Evaluation OE 12-003

• Exelon plans to submit the LAR to revise the LaSalle suppression pool swell design analysis in 4Q 2016 requesting NRC approval within one year 10 LaSalle Pre-Application Meeting - License Amendment Request to Revise Suppression Pool Swell Design Analysis

LaSalle Suppression Pool Swell LAR DISCUSSION 11 LaSalle Pre-Application Meeting - License Amendment Request to Revise Suppression Pool Swell Design Analysis