ML21201A311

Replacement Steam Dryer Visual Inspection Results

ML21201A311
Person / Time
Site:	Browns Ferry
Issue date:	07/20/2021
From:	Rasmussen M Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML21201A311 (9)

Text

Post Office Box 2000, Decatur, Alabama 35609-2000 July 20, 2021 10 CFR 50.4 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Unit 2 Renewed Facility Operating License No. DPR-52 NRC Docket No. 50-260

Subject:

Unit 2 Replacement Steam Dryer Visual Inspection Results (U2R21)

Enclosed is a summary of the results of the visual inspections of the Unit 2 Replacement Steam Dryer that were performed during the recent refueling outage (U2R21). The inspections are required to be performed in accordance with Operating License Condition 2.C(18)(g) during the first two scheduled refueling outages after reaching full Extended Power Uprate conditions. This first report for Unit 2 is being submitted pursuant to Operating License Condition 2.C(18)(h) which requires that the results of the inspection be submitted in a report within 90 days following startup.

There are no new regulatory commitments in this letter. Should you have any questions concerning this submittal, please contact J. L. Paul, Site Licensing Manager, at (256) 729-2636.

Respectfully, Matthew Rasmussen Site Vice President

U.S. Nuclear Regulatory Commission Page 2 July 20, 2021

Enclosure:

Browns Ferry Unit 2 Replacement Steam Dryer (RSD) Inspection Results from the First Refueling Outage (U2R21) Following Installation of RSD and Implementation of Extended Power Uprate cc (w/ Enclosure):

NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant

ENCLOSURE BROWNS FERRY NUCLEAR PLANT UNIT 2 Browns Ferry Unit 2 Replacement Steam Dryer (RSD) Inspection Results from the First Refueling Outage (U2R21) Following Installation of RSD and Implementation of Extended Power Uprate See attached

Browns Ferry Unit 2 Replacement Steam Dryer (RSD) Inspection Results from the First Refueling Outage (U2R21) Following Installation of RSD and Implementation of Extended Power Uprate Purpose This report provides the results of visual inspections of the Replacement Steam Dryer (RSD) as required by the Browns Ferry Unit 2 Renewed Facility Operating License No. DPR-52, License Condition 2.C.(18).(h). This license condition requires that the results of the visual inspections of the RSD be submitted to the NRC within 90 days following startup from each of the first two respective refueling outages.

Summary The Unit 2 RSD was inspected from March 1 through 14, 2021, during the Spring 2021 refueling outage (Unit 2 Refueling Outage 21: U2R21). This was the first refueling outage following installation of the RSD in March 2019 during Unit 2 Refueling Outage 20 (U2R20) and operation at Extended Power Uprate (EPU) conditions since June 2019. The inspections were performed in accordance with GE Hitachi Nuclear Energy Report No. 003N5663, Revision 2 (Tennessee Valley Authority (TVA) Browns Ferry Nuclear Station (BFNS): Recommendations for Future Inspections - Replacement Steam Dryer). The RSD design and the materials and fabrication processes utilized are expected to result in significantly improved resistance to stress corrosion cracking. Therefore, the inspection recommendations in the GEH report focus primarily on the locations that may be susceptible to fatigue from flow-induced vibration. The locations identified are those indicated to have relatively significant cyclic loading during the dryers operation, as determined by detailed stress analyses.

Tables 1 (Frequency of Recommended Locations Based on Analysis and 2 (Description of Recommended Inspections Locations) of the GEH Report list locations that are considered the most susceptible for fatigue cracking based on BWR dryer experience and stress analysis. All accessible weld and weld heat-affected zone (HAZ) base metal surfaces of the RSD were visually inspected during U2R21, with a total scope of 646 points. The summary results of the inspections can be found in the table starting on the next page.

The following explanations apply to the table:

NRI: No Relevant Indication RI: Relevant Indication The parentheses after each Inspection Location refer to the number of points inspected for each.

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Browns Ferry Unit 2 Replacement Steam Dryer (RSD) Inspection Results from the First Refueling Outage (U2R21) Following Installation of RSD and Implementation of Extended Power Uprate Inspection Location Method Inspection Condition Disposition Result Report (if RI)

STEAM DRYER ID Divider Plate Welds & HAZs (32) VT-1-89 NRI Trough Side Plate to Base Plate Weld & VT-1-89 NRI HAZs (6)

Hood Vertical / Horizontal Welds & VT-1-89 NRI HAZs (12)

Perforated Plate to Trough Side Plate VT-1-89 NRI Weld & HAZs (22)

Trough Spacer Pin Weld & HAZs (6) VT-1-89 NRI Skirt to Support Beam Weld & HAZs (8) VT-1-89 NRI Guide Channel to Tee Weld & HAZs (4) VT-1-89 NRI Skirt to Tee Weld & HAZs (12) VT-1-89 NRI Drain Pipe to Trough Base Plate Weld & VT-1-89 NRI HAZs (12)

Drain Pipe to Elbow Weld & HAZs (21) VT-1-89 NRI Drain Elbow to Pipe Weld & HAZs (11) VT-1-89 NRI Drain Elbow to Skirt Weld & HAZs (12) VT-1-89 NRI Collar to Skirt Weld & HAZs (12) VT-1-89 NRI Cover Plate to Hood Weld & HAZs (2) VT-1-89 NRI Trough Base Plate to Hood Weld & VT-1-89 NRI HAZs (4)

Hood Support Stiffener Assembly, VT-1-89 NRI Stiffener to Hood Support Tee Weld &

HAZs, 360 degree weld (16)

Hood Support Stiffener Assembly, VT-1-89 NRI Stiffener to Trough Weld & HAZs, 360 degree weld (16)

Skirt to Lower Support Ring Weld plus 2 VT-1-89 NRI Splice Bars & HAZs (2)

Skirt to Lower Support Ring Weld & VT-1-89 NRI HAZs (6)

Splice Bar Attachment Weld and HAZs VT-1-89 NRI (4)

Trans Brace to Upper Support Ring VT-1-89 NRI Weld & HAZs (2)

Trans Brace Coupler Weld & HAZs (1) VT-1-89 NRI Trans Brace Plate Welds & HAZs (8) VT-1-89 NRI Trans Brace Support Welds & HAZs VT-1-89 NRI (12)

Base Plate to Upper Support Ring Weld VT-1-89 NRI

& HAZs (4)

Base Plate to Upper Support Ring/Latch VT-1-89 NRI Assembly Welds & HAZs (2)

Base Plate to Upper Support Ring/Lifting VT-1-89 NRI Assembly Welds & HAZs (2)

Cover Plate to Upper Support Ring Weld VT-1-89 NRI

& HAZs (2)

Splice Bar to Upper Support Ring and VT-1-89 NRI Trough Welds & HAZs (2)

USR Segment Weld & HAZs (4) VT-1-89 NRI 2

Browns Ferry Unit 2 Replacement Steam Dryer (RSD) Inspection Results from the First Refueling Outage (U2R21) Following Installation of RSD and Implementation of Extended Power Uprate Inspection Location Method Inspection Condition Disposition Result Report (if RI)

Skirt to Upper Support Ring Weld & VT-1-89 NRI HAZs (6)

STEAM DRYER OD 000 Degree Pad Welds & HAZs (1) VT-1-89 NRI Steam Dryer Outer Banks Access Panel VT-1-89 NRI Welds & HAZs 000 Side (6)

Steam Dryer Outer Banks Access Panel VT-1-89 NRI Welds & HAZs 180 Side (6)

Both Sides of the Bank to Divider Plate VT-1-89 NRI Weld & HAZs (16)

Both Sides of the Bank to Exhaust VT-1-89 NRI Plenum Plate Vertical Weld & HAZs (20)

Hood to Cover Plate Horizontal Weld & VT-1-89 NRI HAZs (2)

Hood to Top Cap Horizontal Weld & VT-1-89 NRI HAZs (6)

Perforated Plate to Bank Top Cap Weld VT-1-89 NRI

& HAZs (6)

Perforated Plate to Trough Side Plate VT-1-89 NRI Weld & HAZs (6)

Trough Side Plate to Base Plate Weld VT-1-89 NRI

& HAZs (6)

Both Sides of the Hood Support to VT-1-89 NRI Trough Weld & HAZs (16)

Perforated Plate to End Plate Weld & VT-1-89 NRI HAZs (4)

Perforated Plate to Perforated Plate VT-1-89 NRI Weld & HAZs (16)

Perforated Plate to End Plate Weld & VT-1-89 NRI HAZs from Trough Base Plate to Hood Cap (8)

Trough Spacer Pin Weld & HAZs (6) VT-1-89 NRI Bank Tie Rod Bolting Welds & HAZs for VT-1-89 NRI all 6 locations on the 000 Deg Side (6)

Bank Tie Rod Bolting Welds & HAZs for VT-1-89 NRI all 6 locations on the 180 Deg Side (6)

Hood to Trough Base Plate Horizontal VT-1-89 NRI Weld & HAZs (4)

Both Sides of the Divider Plate to Inner VT-1-89 NRI Plate Welds & HAZs (6)

Drain Channel to Upper Support Ring VT-1-89 NRI Horizontal Weld & HAZs (4)

Drain Channel to Support Beam Weld & VT-1-89 NRI HAZs (8)

Drain Channel to Support Ring Tab VT-1-89 NRI Welds & HAZs (20)

Guide Channel to Drain Channel Tee VT-1-89 NRI Vertical Weld & HAZs (4) 3

Browns Ferry Unit 2 Replacement Steam Dryer (RSD) Inspection Results from the First Refueling Outage (U2R21) Following Installation of RSD and Implementation of Extended Power Uprate Inspection Location Method Inspection Condition Disposition Result Report (if RI)

Drain Channel to Drain Channel Tee VT-1-89 NRI Vertical Weld & HAZs (8)

Skirt to Drain Channel Tee Vertical Weld VT-1-89 NRI

& HAZs (4)

Doubler Plate to Upper Support Ring & VT-1-89 NRI HAZs (8)

General Overview of the Side Surfaces VT-1-89 NRI (4)

General Overview of the Top Surfaces VT-1-89 NRI (1)

Hood to Inlet End Plate Vertical Weld & VT-1-89 NRI HAZs (18)

Both Hood to Hood Tee Vertical Welds VT-1-89 NRI

& HAZs (4)

Hood to Hood Tee Vertical Weld & VT-1-89 NRI HAZs (18)

Both Sides of the Hold Down Assembly VT-1-89 NRI to Exhaust Plenum Plate Vertical Weld

& HAZs (4)

Hold Down Assembly to Trough Base VT-1-89 NRI Plate Horizontal Weld & HAZs (2)

Lifting Assembly - Support Ring Anchor VT-1-89 NRI Weld & HAZs (4)

Lifting Assembly - Bolting (4) VT-1-89 RI 1676166 Repaired Lifting Assembly - Lower Bracket and VT-1-89 NRI Welds Plus HAZs (4)

Lifting Assembly - Middle Bracket and VT-1-89 NRI Welds Plus HAZs (4)

Lifting Assembly - Rod to Anchor Weld VT-1-89 NRI

& HAZs (4)

Lifting Assembly - Upper Bracket and VT-1-89 NRI Welds Plus HAZs (4)

Latch Box General Condition for VT-1-89 NRI Evidence of Handling Damage (2)

Lower Guide Channel General Condition VT-1-89 NRI for Evidence of Handling Damage (2)

Lower Support Ring to Guide Channel VT-1-89 NRI Horizontal Weld & HAZs (2)

Lower Support Ring to Skirt Horizontal VT-1-89 NRI Weld & HAZs (6)

Lower Support Ring Splice Bar General VT-1-89 NRI Condition for Evidence of Handling Damage (2)

Splice Bar Attachment Weld & HAZs (8) VT-1-89 NRI Seismic Lug General Condition for VT-1-89 NRI Evidence of Handling Damage, also Associated Bolting, Welds & HAZs (2)

Bank Tie Bar Welds & HAZs (34) VT-1-89 NRI Trough Base Plate Center Horizontal VT-1-89 NRI Weld & HAZs (1) 4

Browns Ferry Unit 2 Replacement Steam Dryer (RSD) Inspection Results from the First Refueling Outage (U2R21) Following Installation of RSD and Implementation of Extended Power Uprate Inspection Location Method Inspection Condition Disposition Result Report (if RI)

Top Flange to C-Channel to Hood VT-1-89 NRI Cover Weld & HAZs (2)

Upper Support Ring Horizontal Weld & VT-1-89 NRI HAZs (26)

Upper Support Ring Tapered Pin Seal VT-1-89 NRI Weld & HAZs (8)

Upper Support Ring to Splice Bar VT-1-89 NRI Vertical Weld & HAZs (4)

Upper Support Ring to Guide Channel VT-1-89 NRI Horizontal Weld & HAZs (2)

Upper Support Ring to Skirt Horizontal VT-1-89 NRI Weld & HAZs (2)

Inspection Results Relevant indications were noted at only one inspection location during inspections performed during U2R21. They are described as follows:

(1) BFN2-SD OD LA 220 Eye - Bolting and BFN2-SD OD LA 320 Eye - Bolting: The Steam Dryer Lifting Assembly Bolts at 220° and 320° were observed to have sheared at the shaft and the nut was no longer present. Both bolts were retrieved and a failure analysis was performed.

The analysis concluded that it appeared that the presence of small cyclic loads on the bolts combined with a mildly aggressive local environment containing chlorides let to the corrosion-assisted fatigue failure of the bolts (a possible source of the cyclic load is a vibration of the dryer unit locking pin assembly).

Disposition of Indications Condition Report (CR) 1676166 was initiated to disposition both relevant indications. The disposition is as follows:

(1) BFN2-SD OD LA 220 Eye - Bolting and BFN2-SD OD LA 320 Eye - Bolting: The sole function of the Steam Dryer Lifting Assembly Bolts at 220° and 320° is to prevent rotation of the lifting lug. Therefore, a repair was decided upon to tack weld the remaining bolt assembly as this would prevent rotation of the lifting lug and restore functionality. (NOTE: Per the recommendation of the inspection vendor, the repair was performed not only for the bolts that were sheared but also was performed preemptively for the intact bolts at 40° and 140° to eliminate any future concerns about loose parts in the reactor vessel.)

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Browns Ferry Unit 2 Replacement Steam Dryer (RSD) Inspection Results from the First Refueling Outage (U2R21) Following Installation of RSD and Implementation of Extended Power Uprate Conclusion A completed baseline inspection of the Browns Ferry Unit 2 Replacement Steam Dryer (RSD) was performed during the Spring 2021 Refueling Outage 21. This baseline inspection included successful visual inspection of all inspection locations required by the Facility Operating License Condition 2.C.(18).(h) for inspection of the RSD. All observations were acceptable for the locations inspected. There were two relevant indications that were adequately dispositioned.

The subsequent inspection scope of the RSD will be performed during Unit 2 Refueling Outage 22 (U2R22) in Spring 2023, and the results will be provided at that time consistent with the Browns Ferry Operating License.

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