ML21019A569

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Pre-Submittal Teleconference for Proposed License Amendment Requests (Lars) for the WBN Unit 2 Replacement Steam Generator (RSG) Project
ML21019A569
Person / Time
Site: Watts Bar Tennessee Valley Authority icon.png
Issue date: 01/19/2021
From: Kimberly Green
Plant Licensing Branch II
To:
Tennessee Valley Authority
Green K
References
Download: ML21019A569 (79)
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Text

Watts Bar Nuclear Plant (WBN) Unit 2 Pre-Submittal Teleconference for Proposed License Amendment Requests (LARs) for the WBN Unit 2 Replacement Steam Generator (RSG) Project January 21, 2021

Agenda

  • Opening Remarks
  • Background
  • LAR Schedule Milestones
  • Closing Remarks l 2

Opening Remarks

  • The purpose of this meeting is to discuss the planned LARs for the WBN Unit 2 RSG Project.
  • The following LARs are needed to support the RSG project:

- WBN-TS-20 SG Tube Rupture (SGTR) Accident Dose Design Basis Change

- WBN-TS-20 SG Water Level Changes for RSGs

- WBN-TS-20 SG Program Changes

- WBN-TS-20 Change to Unit 1 TS 3.7.12 for Continuous Opening of the Auxiliary Building Secondary Containment Enclosure (ABSCE) as a One-Time Exception

  • Individual presentation for each LAR.

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Background

  • TVA initially planned to replace the WBN Unit 2 Alloy-600 steam generators with Alloy-690 RSGs during the WBN Unit 2 Fall 2023 refueling outage (U2R5).
  • TVA recently decided to move this activity to the Spring 2022 refueling outage (U2R4) scheduled to commence in March 2022.
  • The RSGs have been manufactured and delivered to the WBN, where the RSGs have been placed in protected storage until they are prepared for installation just prior to the RSG outage.
  • For the RSG components, the LARs are similar in nature to those done for the WBN Unit 1 SG replacement project.

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Schedule for Submittal

  • January 21, 2021 - Pre-submittal teleconference with NRC
  • March 1, 2021 - Submit LARs to NRC
  • Expedited NRC approval of the LARs by February 1, 2022 (Requested) with implementation by March 1, 2022 (scheduled start of WBN U2R4 outage to replace the Unit 2 steam generators) l 5

CLOSING REMARKS l 6

Watts Bar Nuclear Plant (WBN)

Proposed Modification to UFSAR Section 15.5 to Reflect Revised Steam Generator Tube Rupture (SGTR) Accident Dose Values Associated with Operation of the Unit 2 Replacement Steam Generators (RSGs)

January 21, 2021

Agenda

  • Opening Remarks
  • Background
  • Need for Change
  • Proposed Design Basis Changes for WBN dual-unit Updated Final Safety Analysis (UFSAR)
  • Precedent
  • Closing Remarks l 2

Opening Remarks

  • Purpose of the meeting is to discuss proposed changes to reflect the revised analysis of the radiological consequences of a Steam Generator Tube Rupture (SGTR) Accident associated with operation of Unit 2 Replacement Steam Generators (RSGs).
  • Per guidance in NEI 96-07 R1, the increase in the main control room (MCR) thyroid dose for the pre-accident case was a more than minimal increase in the radiological consequences of an accident previously evaluated in the UFSAR.

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Background

  • Installation of RSGs for WBN Unit 2 results in revised primary and secondary side mass releases reflected in UFSAR Table 15.5-18.
  • Primary side releases decrease

- Increase in primary coolant that flashes before control room isolation

  • Secondary side releases increase

- Identical to WBN Unit 1 values

  • All other input remains the same l 4

Need for Change

  • To enable installed operation of the Unit 2 RSGs, the affected WBN Design and Licensing Bases must be updated and demonstrated to meet Regulatory Requirements.
  • The increase in the MCR thyroid dose for the pre-accident case exceeded the NEI 96-07, Revision 1, threshold for requiring Nuclear Regulatory Commission (NRC) approval.

- The increase was greater than 10% of the difference between the current calculated dose value and the regulatory guideline value (10 CFR 50 Appendix A GDC 19).

- Increase is attributed to the increase in the amount of primary coolant that flashes during the time period before the MCR is isolated.

  • The tables on the next two slides show current SGTR Accident doses compared to those resulting from WBN Unit 2 operation with the RSGs installed.

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SGTR Accident Dose Comparison Table 1 l 6

SGTR Accident Dose Comparison Table 2 l 7

Proposed Design Basis Changes for WBN UFSAR (Table 15.5-18 markup) l 8

Proposed Design Basis Changes for WBN UFSAR (Table 15.5-19 markup) l 9

Proposed Design Basis Changes for WBN UFSAR (Table 15.5-18 final) l 10

Proposed Design Basis Changes for WBN UFSAR (Table 15.5-19 final) l 11

Precedent

  • In support of the replacement of the WBN Unit 1 SGs, changes to UFSAR Section 15.5 were proposed to reflect the increased doses for the SGTR accident resulting from installation of the WBN Unit 1 RSGs, as approved in Amendment 64 (ML062290485).

Among other impacts, this entailed approval of the resulting changes to the SGTR dose consequences (ML18347B330).

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CLOSING REMARKS l 13

Watts Bar Nuclear Plant (WBN)

Proposed Modifications to the Unit 2 Technical Specifications to Change the Required Narrow Range Steam Generator Water Level Value for Operation of the Unit 2 Replacement Steam Generators January 21, 2021

Agenda

  • Opening Remarks
  • Background
  • Need for Change
  • Proposed TS changes
  • Precedent
  • Closing Remarks l 2

Opening Remarks

  • Purpose of the meeting is to discuss proposed changes to the narrow range steam generator water level (SGWL) required value contained in WBN Unit 2 Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.4.7.b and Surveillance Requirements (SRs) 3.4.5.2, 3.4.6.3, and 3.4.7.2.
  • For these TS, the required narrow range SGWL value changes from 6%

with the Old (Existing) Steam Generators (OSGs) to 32% with the Replacement Steam Generators (RSGs).

  • Similar required narrow range SGWL value changes ( 6% to 32%) were made to the WBN Unit 1 TS resulting from replacement of the Unit 1 OSGs with same design RSGs.

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Background

  • Within each RSG, the secondary side water coverage of the tube bundle is achieved at a narrow range SGWL of 32% (WBN Unit 2 TS LCO 3.4.7.b and TS SRs 3.4.5.2, 3.4.6.3, and 3.4.7.2), as opposed to the 6% narrow range SGWL value that defines secondary side water coverage of the tube bundle in each OSG.
  • For Unit 2 TS LCO 3.4.7.b and SRs 3.4.5.2, 3.4.6.3, and 3.4.7.2, the condition achieved by tube bundle water coverage establishes the function of the steam generator to be used as a heat removal mechanism.
  • The Unit 2 and Unit 1 RSGs are the same design steam generators (Westinghouse Model 68AXP). Same analyses were used for Unit 1 and Unit 2 RSGs to derive the SGTR Accident doses. A detailed demonstrated accuracy calculation (DAC) establishes the 32% setpoint value, which considered instrument uncertainty, margin, narrow range tap location, RSG tube bundle height, and environmental conditions of the instrumentation.

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Need for Change In order to establish a SG capable to function as a heat removal mechanism, the SG tube bundle must be covered on the SG secondary (shell) side. The percentage of narrow range SGWL instrument span with the RSGs that demonstrates the point at which water coverage of the SG tube bundle has been achieved is 32%, as opposed to the 6% value utilized for the OSGs.

Unit 2 TS LCO 3.4.7.b, and SRs 3.4.5.2, 3.4.6.3, and 3.4.7.2 state the required narrow range SGWL value at which point secondary side water coverage of the SG tube bundle is achieved. As a result, with installation of the Unit 2 RSGs, the Unit 2 TS LCO 3.4.7.b, and SRs 3.4.5.2, 3.4.6.3, and 3.4.7.2 must be changed to incorporate the revised required narrow range SGWL value of greater than or equal to 32%.

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Proposed TS Changes

  • Revise WBN Unit 2 TS LCO 3.4.7.b and SRs 3.4.5.2, 3.4.6.3, and 3.4.7.2 to change the required narrow range SG water level value from 6% to 32%

following replacement of the Unit 2 SGs.

  • Associated changes are made to the Unit 2 TS Bases.

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Proposed TS Changes for WBN 2 (markup) l 7

Proposed TS Changes for WBN 2 (markup) l 8

Proposed TS Changes for WBN 2 (markup) l 9

Proposed TS Changes for WBN 2 (markup) l 10

Proposed TS Changes for WBN 2 (final typed) l 11

Proposed TS Changes for WBN 2 (final typed) l 12

Precedent

CLOSING REMARKS l 14

Watts Bar Nuclear Plant (WBN)

Proposed Modifications to the Unit 2 Technical Specifications Steam Generator Program Descriptions to Reflect Replacement of the Unit 2 Old (Existing) Steam Generators (OSGs) with Replacement Steam Generators (RSGs)

January 21, 2021

Agenda

  • Opening Remarks
  • Background
  • Need for Change
  • Proposed Technical Specification (TS)/Facility Operating License (FOL) Changes
  • Precedent
  • Closing Remarks l 2

Opening Remarks

  • Purpose of the meeting is to discuss proposed administrative changes to the Steam Generator (SG) Program descriptions contained in WBN Unit 2 TS 3.4.17, 5.7.2.12, and 5.9.9 to remove SG inspection and repair provisions that become invalid with the installation of the Unit 2 RSGs.
  • The SG material change from Alloy 600 Old (Existing) Steam Generators (OSGs) to Alloy 690 RSGs requires removal from the Unit 2 TS of inspection/repair provisions that are only applicable to the Alloy 600 OSGs.
  • In addition, the allowance to use PAD4TCD to establish core operating limits is proposed to be deleted from License Condition 2.C.(4) in the Unit 2 FOL, because PAD4TCD usage applies only to the OSGs.

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Background

  • Current WBN Unit 2 TS 3.4.17, 5.7.2.12, and 5.9.9 describe the following SG inspection/repair provisions that are only applicable to the Alloy 600 OSGs:

- F* SG Tube Inspection Method (NRC SE ML16203A365)

- Voltage-Based Alternate Repair Criteria (ARC) SG Tube Inspection Method (NRC SE ML19063B721)

- SG Tube Sleeving Repairs

  • License Condition 2.C.(4) of the current WBN Unit 2 FOL allows usage of PAD4TCD to establish core operating limits until the Unit 2 OSGs have been replaced (NRC SE ML19046A286) l 4

Need for Change

  • Administrative changes to the Unit 2 TS and the Unit 2 FOL are necessary to remove descriptions of the following SG inspection/repair provisions that with the installation of the RSGs will no longer be NRC-approved for use:

- F* SG Tube Inspection Method

- Voltage-Based Alternate Repair Criteria (ARC) SG Tube Inspection Method

- SG Tube Sleeving Repair

  • The allowance to use PAD4TCD to establish core operating limits, as described in the Unit 2 FOL, License Condition 2.C.(4), applies only until the Unit 2 SGs have been replaced. With the installation of the Unit 2 RSGs, it is necessary to administratively remove the License Condition 2.C.(4) statement allowing the use of PAD4TCD.

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Proposed TS/FOL Changes

  • Revise Unit 2 TS 3.4.17, 5.7.2.12, and 5.9.9 to remove the term repair, which applies to SG tube sleeving with the OSGs. With the RSGs, only SG tube plugging is permissible.
  • Remove descriptions associated with F*, Voltage-Based ARC, and SG Tube Sleeving from TS 5.7.2.12 and 5.9.9. Minor editing is also proposed to make these Unit 2 TS sections consistent with their counterparts in Unit 1 TS 5.7.2.12 and 5.9.9.
  • Revision to Unit 1 TS 5.7.2.12 also reflects TSTF-510, Revision 2, Revision to Steam Generator Program Inspection Frequencies and Tube Sample Selection, for Alloy 690 thermally treated tubing.
  • Revise Unit 2 FOL License Condition 2.C.(4) to remove reference to PAD4TCD.

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Proposed TS Changes for WBN 2 (markup) l 7

Proposed TS Changes for WBN 2 (markup) l 8

Proposed TS Changes for WBN 2 (markup)

ARC Tube Repair F*

ARC l 9

Proposed TS Changes for WBN 2 (markup)

ARC l 10

Proposed TS Changes for WBN 2 (markup)

ARC l 11

Proposed TS Changes for WBN 2 (markup)

F*

TSTF-510 l 12

Proposed TS Changes for WBN 2 (markup)

TSTF-510 l 13

Proposed TS Changes for WBN 2 (markup)

TSTF-510 ARC l 14

Proposed TS Changes for WBN 2 (markup)

ARC l 15

Proposed TS Changes for WBN 2 (markup)

Tube Repair l 16

Proposed TS Changes for WBN 2 (markup)

Tube Repair l 17

Proposed TS Changes for WBN 2 (markup)

Tube Repair l 18

Proposed TS Changes for Unit 2 FOL License Condition 2.C.(4)

(markup) l 19

Proposed TS Changes for WBN 2 (final) l 20

Proposed TS Changes for WBN 2 (final) l 21

Proposed TS Changes for WBN 2 (final) l 22

Proposed TS Changes for WBN 2 (final) l 23

Proposed TS Changes for WBN 2 (final) l 24

Proposed TS Changes for WBN 2 (final) l 25

Proposed TS Changes for Unit 2 FOL License Condition 2.C.(4) (final) l 26

CLOSING REMARKS l 27

Watts Bar Nuclear Plant (WBN)

Proposed Modifications to Unit 1 Technical Specification 3.7.12 for One-Time Exception to Permit Continuous Opening of the Auxiliary Building Secondary Containment Enclosure (ABSCE) as Needed to Support the Unit 2 Replacement Steam Generator (RSG) Outage January 21, 2021

Agenda

  • Opening Remarks
  • Background
  • Need for Change
  • Basis for Change
  • Proposed TS Changes
  • Precedent
  • Closing Remarks l 2

Opening Remarks

  • The activities of the RSG project are larger in scale than those of a typical refueling outage, leading to more movement of personnel and equipment.
  • The administrative controls to be employed are the same as those used currently for control of the intermittent openings of the ABSCE boundary presently allowed by Unit 1 TS 3.7.12. These controls achieve closure of all ABSCE boundary openings within two minutes following notification from the main control room (MCR) of an Auxiliary Building Isolation (ABI) alarm, thus ensuring closure of the ABSCE consistent with the safety analysis.

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Background

  • The ABGTS, and the ABSCE that provides the ventilation envelope supporting ABGTS operability, are shared between WBN Unit 1 and Unit 2.
  • When Unit 2 shuts down for the RSG Outage, it will exit the Unit 2 TS 3.7.12 operability requirements for ABGTS.
  • However, due to the shared ABGTS and ABSCE boundary, the operability requirements of WBN Unit 1 will still apply during the RSG Outage.

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Background

  • During the Unit 2 RSG Outage, temporary openings will be made in the Unit 2 shield building concrete dome and steel containment vessel to allow removal of the old (existing) SGs and installation of the RSGs.
  • Also during the RSG Outage (as with any Unit 2 outage), when the Unit 2 equipment hatch is opened, the Unit 2 containment becomes an extension of the ABSCE boundary.
  • The Note added to WBN Units 1 and 2 TS 3.7.12 in October 2017 (ML17236A057) allows intermittent opening of the ABSCE boundary under administrative controls that ensure the ABSCE can be closed consistent with the safety analysis.
  • In the TVA response to an RAI in 2017 (ML17205A322) TVA acknowledged that a separate LAR would be needed for the openings of the ABSCE to support the Unit 2 RSG project.

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Need for Change

  • During the Unit 2 RSG Outage, a large flow of personnel and equipment in and out of the Unit 2 Containment is planned. This flow will be in excess of what is experienced during a typical refueling outage.
  • Given that the ABSCE boundary will be required to be operable, the current wording of the Note in Unit 1 TS 3.7.12 would limit passage through this boundary to intermittent openings.

Coupled with the large flow of personnel and equipment, this would lead to excessive cycling of the ABSCE doors, which in turn could challenge the integrity of the doors over the course of the Unit 2 RSG Outage.

  • Thus, there is a need for continuous, versus intermittent, opening of the ABSCE boundary at controlled access points during the Unit 2 RSG Outage.

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Need for Change

  • The ABSCE access points proposed to be kept continuously open have been identified.
  • The following are summaries of each access point.

- Plant Door A157, Upper Containment Personnel Air Lock Access Door - to be used by workers accessing upper containment areas through the Upper Personnel Air Lock, as well as providing minor equipment access.

- Plant Door A77, Lower Containment Personnel Air Lock Access Door - to be used by workers accessing lower containment areas through the Lower Containment Personnel Air Lock, as well as providing minor equipment access.

- Plant Door A132/A133, Auxiliary Building General Supply Fan Room Access Door

- to be used by workers for general access to the Auxiliary Building.

- Unit 2 Equipment Hatch - to be used to transfer materials and equipment into and out of containment; secured by temporary ABSCE door (0-DOOR-410-R003).

  • Note that when these doors are secured, they provide part of the ABSCE boundary and thus the temporary openings in the shield building have no continued impact on the ABSCE.

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Need for Change

  • The ABSCE boundary controlled access points described on the previous slide are shown on these figures:

- WBN dual-unit Updated Final Safety Analysis Report UFSAR Figure 6.2.3-5

- WBN UFSAR Figure 6.2.3-6

- WBN UFSAR Figure 6.2.3-7 l 8

Basis for Change

  • In terms of ABSCE closure time capability, there is no difference between the control of intermittent ABSCE openings currently managed under Unit 1 TS 3.7.12 versus the control of continuous ABSCE openings proposed to be managed during the Unit 2 RSG Outage.
  • As required by existing TVA procedures, ABSCE openings will be continuously manned and in contact with the MCR, ready for closure within the time requirements of the safety analysis.
  • Based on similar experience with other TVA nuclear projects, there is confidence that the WBN RSG Project team can achieve closure of the continuously-open permanent plant doors A157, A132/A133, A77, and the temporary ABSCE door (0-DOOR-410-R003), as required during the WBN-2 RSG Outage consistent with the safety analysis.

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Proposed TS Changes

  • One-time new footnote 1 to the existing TS 3.7.12 Note that describes the intermittent opening of the ABSCE.
  • Associated changes are made to the Unit 1 TS Bases.

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Proposed TS Changes for WBN 1 (markup) l 11

Proposed TS Changes for WBN 1 (final) l 12

Precedent

  • NRC License Amendment for Watts Bar Nuclear Plant, Units 1 and 2, dated October 17, 2017 (ML17236A057)

- NRC approved a change to TS 3.7.12 to add a Note allowing intermittent opening of the ABSCE boundary under administrative controls that ensure the ABSCE can be closed consistent with the safety analysis.

  • There is no direct precedent for a change from intermittent opening to a one-time exception for continuous opening of the ABSCE.

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CLOSING REMARKS l 14

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