ML16342B621

Peach Bottom Atomic Power Station, Unit 2 - Results of Visual Inspections of Replacement Steam Dryer

ML16342B621
Person / Time
Site:	Peach Bottom
Issue date:	12/07/2016
From:	Massaro M J Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML16342B621 (7)

Text

Exelon Generation. December 7, 2016 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington DC 20555-0001 Peach Bottom Atomic Power Station, Unit 2 Renewed Facility Operating License No. DPR-44 NRC Docket No. 50-277 DPR-44 Operating License 2.C(15)(g)

Subject:

Results of Visual Inspections of Unit 2 Replacement Steam Dryer

References:

1. WCAP-17635-P, Rev. 3, Peach Bottom Atomic Power Station Unit 2 and Unit 3 Replacement Steam Dryer Comprehensive Vibration Assessment program (CVAP), April 2014 2. PBAPS Extended Power Uprate License Amendment Request -Supplement 24 -Response to Request for Additional Information, dated April 11, 2014 3. NRC -Issuance of Amendments -PBAPS Units 2 and 3 Extended Power Uprate, License Amendments 293/296 (including NRC Safety Evaluation Report), dated August 25, 2014 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 {P2R21 }. The inspections are required to be performed following the guidelines of WCAP-17635-P in accordance with Operating License Section 2.C{15)(f). This first report is being submitted pursuant to Operating License Condition 2.C{15}{g) which requires that the results of the inspection be submitted in a report within 90 days following startup from each of the first two respective refueling outages. The inspection was performed in accordance with WCAP-17635, Rev. 3 (Reference 1} which was submitted to the NRC in the Reference 2 letter and referenced by the NRC in the NRC Safety Evaluation Report for Extended Power Uprate (Reference 3). If you have any questions concerning this letter, please contact Sandra Kame at (717) 456-3022. Michael J. Massaro Site Vice President Peach Bottom Atomic Power Station CCN: 16-101 Attachment -Unit 2 License Condition 2.C(15}{g} Replacement Steam Dryer Inspection Results cc: Regional Administrator, Region I, USNRC USNRC Senior Resident Inspector, PBAPS R. R. Janati, Pennsylvania Bureau of Radiation Protection S. T. Gray, State of Maryland Attachment -Results of Visual Inspection for PBAPS Unit 2 Replacement Steam Dryer Page 1 of6 ATTACHMENT Unit 2 License Condition 2.C(15)(g) Replacement Steam Dryer Inspection Results Attachment -Results of Visual Inspection for PBAPS Unit 2 Replacement Steam Dryer Page2of6 Peach Bottom Unit 2 Steam Dryer Inspection Results from the First Refueling Outage Following Installation of Steam Dryer and Implementation of Extended Power Uprate Purpose: This report provides the results of the visual inspections of the Replacement Steam Dryer (RSD) as required by the Peach Bottom Unit 2 Renewed Facility Operating License No DPR-44, License Condition 2.C(15)(g). This license condition requires that the results of the inspection be submitted in a report within 90 days following startup from each of the first two respective refueling outages. Summary: The Unit 2 Replacement Steam Dryer was inspected during the fall 2016 refueling outage, P2R21, from October 26th through November 4th, 2016. This was the first refueling outage following installation of the RSD in November 2014 and operation at Extended Power Uprate (EPU) conditions since May 2015. The inspections were performed in accordance with the requirements of the WCAP-17635-P and recommendations from the manufacturer, Westinghouse. The inspection scope was defined based upon Operating Experience (OE) for the Westinghouse steam dryer design from previous installations, high cyclical stress locations determined from the dryer acoustic analysis, similarities to BWRVIP-139-A inspection locations and finally, by higher stress locations where solution annealing of structural welds had not been performed. The guidelines for the dryer inspection are defined in WCAP-17635-P Section 5. Table 5-1 provides the inspection locations for the Unit 2 RSD following the first cycle of operation at EPU conditions. A general visual examination (VT-3) was performed on the entire RSD. The baseline inspection included the top of the RSD (including the outside of the skirt), underside of the RSD, lifting rods, hold down rods, support ring, outer ring top cage, W and U channel guides, support ring, vertical drain channels, outer, middle and inner hoods. All observations were acceptable for the structural components and welds inspected. There were indications on four welds that required further evaluation. These welds are non-structural and were not explicitly modeled or analyzed as part of the structural qualification of the steam dryer. The summary results of the inspections can be found in the table below. NRI = No Relevant Indication RI= Relevant Indication Inspection Location Method Inspection Condition Report Disposition Result (if RI) General Inspection of Top of the Replacement VT-3 NRI Steam Dryer (to include outside of skirt) General Inspection on Underside of VT-3 NRI Replacement Steam Dryer Hold Down Rods (HDRs) (and welded VT-3, NRI attachments to the top plate of the dryer) VT-1 Lifting Rods Top Ends (and welded attachments VT-3, NRI to the top plate of the dryer) VT-1 Hold Down Rods (and welded attachments to the VT-3, RI support ring) VT-1 2734507 Use-as-is Lifting Rods Top Ends (and welded attachments VT-3, NRI to the support ring) VT-1 Attachment -Results of Visual Inspection for PBAPS Unit 2 Replacement Steam Dryer Page 3of6 Inspection Location Method Inspection Condition Report Disposition Result (if RI) Support Ring VT-3 NRI Outer, middle, inner hoods VT-3 NRI Outer Ring Top Cage VT-3 NRI Vertical Drain Channels VT-3 NRI Skirt (Outside) VT-3 NRI Skirt (Inside) VT-3 NRI Visual examinations (VT-1) were performed on welds associated with the RSD. As described in WCAP-17635-P, the steam dryer is octagonal (high symmetry) and VT-1 inspections were performed on a section of the octagon. If any flaws were identified, the comparable locations on the other sections of the dryer were examined in the same outage. The results of the VT-1 inspections can be found in the table below: Inspection Condition Weld Designation Description Report Disposition Result (if RI) AA 335740 W1 0 W channel to ring NRI AA 335740 W2 90 U channel to ring NRI AA 335740 W3 112.5 Vertical drain channel to ring NRI AA 335740 W4 135 Upper Dryer to lower dryer NRI circumferential weld AA 335740 W5 112.5 Site Drain Channel Piece Welds NRI AA 335740 W6 LR 142.25 Lifting rod bracket to top of dryer NRI AA 335740 W6 HOR Hold down rod bracket to top of NRI 142.25 drver AA 3357 40 W7 LR 142.25 Lifting rod bracket to ring NRI connection AA 335740 W7 HOR Hold down rod bracket to ring RI 37.75 connection 2734507 Use-as-is AA 335740 W7 HOR Hold down rod bracket to ring RI 142.25 connection 2734507 Use-as-is AA 335740 W7 HOR Hold down rod bracket to ring RI 217.75 connection 2734507 Use-as-is AA 335740 W7 HOR Hold down rod bracket to ring RI 322.25 connection 2734507 Use-as-is AA 335740 wa LR Lifting rod bracket to rod NRI 142.25 AA 335740 wa HOR Hold down rod bracket to rod NRI 142.25 AA 335740 W9 LR 138.5 Lifting rod top to rod NRI AA 335740 W10 HOR Hold down rod top to rod NRI 146 AA 335740 W14 90 Horizontal shims to block NRI Weld Designation AA 335741 W3 112.5 AA 335741 W5112.5 AA 335741 W9 112.5 AA 335741 W11112.5 AA 335741 W13 90 AA 335741 W15112.5 AA 335741 W18 112.5 AA 335741 W20 112.5 AA 335741 W21 112.5 AA 335741 W2290 AA 335741 W2390 AA 335741 W24 112.5 AA 335741 W2690 AA 335741 W2790 AA 335741 W28 112.5 AA 335741 W29 112.5 Inner AA 335741 W29 112.5 Middle AA 335741 W29 112.5 Outer AA 335741 W3090 AA 335741 W3290 AA 335741 W35112.5 AA 335741 W36 112.5 AA 335741 W37 112.5 AA 335741 W38 112.5 AA 335741 W39 112.5 AA 335741 W41 157.5 Inner AA 335741 W41 157.5 Outer AA 362220 W 1 55 Attachment -Results of Visual Inspection for PBAPS Unit 2 Replacement Steam Dryer Page 4 of6 Inspection Condition Description Report Disposition Result (if RI) Inner panel to inner inner corner NRI Inner panel to inner outer corner NRI Middle panel to middle inner NRI corner Middle panel to middle outer NRI corner Toplnnerhoodtoinnerpanel NRI lnnerhoodtoinnerhood NRI Outer panel to outer inner corner NRI Outer panel to outer outer corner NRI Outer corner top cap all around+ NRI Top middle hood to middle panel NRI Bottom middle hood to outer NRI oanel Middle hood to Middle hood NRI Top outer hood to outer panel NRI Bottom outer hood to support ring NRI Outer hood to Outer hood NRI Top ring girder to panel and NRI corner and corner cap Top ring girder to panel and NRI corner and corner cao Top ring girder to panel and NRI corner and corner cao Seismic Block (Outer Welds) NRI Shims NRI Inner corner to top inner hood NRI Middle corner to top middle hood NRI Outer corner to top outer hood NRI Middle corner to bottom hood NRI Outer corner to bottom hood NRI Instrumentation mast bracket NRI Instrumentation mast bracket NRI Two halves of main ring NRI Weld Designation AA 335756 W5W8W18 90 AA 335757 W5W8W18 90 AA 335758 W5W8W18 90 AA 335758 W 13 90 AA335762 W2 112.5 AA 335742 W1 0 AA 335742 W2 90 AA335742 W3 135 AA335742 W4 112.5 AA 335742 W5 0 AA335742 W6 90 AA335742 W7 135 AA 335742 W8 90 AA 3357 42 W9 112.5 AA 335742 W10 112.5 AA 335743 W8 112.5 AA335757 W10 90 AA 362066 W1 0 AA 362066 W2 90 AA 362066 W3 135 AA362066 W4 90 AA 362066 W5 112.5 AA 362066 W6 112.5 AA 362222 W1 45 AA 362221 W1 45 Inspection Results: Attachment -Results of Visual Inspection for PBAPS Unit 2 Replacement Steam Dryer Page 5 of6 Inspection Condition Description Report Disposition Result (if RI) Inner top channel to top strip NRI Middle top channel to top strip NRI Outer top channel to top strip NRI Outer perf plate to top strip NRI Girders to center ring NRI Middle ring to lower W channel NRI Middle ring to lower U channel NRI Middle ring to lower part outer NRI walls Middle ring to lower part vert drain NRI channels Middle ring to upper W channel NRI Middle ring to upper U channel NRI Middle ring to upper outer walls NRI W and U channels to upper outer NRI walls Middle ring to upper vert drain NRI channels Vert drain channels to upper outer NRI walls Outer Trough to Spoke NRI Trough Plate to Side plate NRI W channel to lower ring NRI U channel to lower ring NRI Lower ring to walls above NRI W and U channels to walls NRI Drain channels to walls NRI Lower ring to drain channels NRI Welds Lower Ring Together NRI Middle ring welded together NRI Indications were identified in weld AA335740 W7 fillet weld at the hold down rod interface to the support ring for all four (4) hold down rod locations at 37.75, 142.25, 217.75 and 322.25 degree azimuths (Ref. IR 2734507). Indications have been dispositioned as use-as-is. The indications do not adversely affect the Attachment -Results of Visual Inspection for PBAPS Unit 2 Replacement Steam Dryer Page 6 of6 steam dryer's structural integrity. These welds are non-structural and were not explicitly modeled or analyzed as part of the structural qualification of the steam dryer. All hold down rod weld locations are scheduled for re-inspection during the Unit 2 P2R22 in 2018 to determine if any changes have occurred. No other recordable indications were identified during the inspection process. Disposition of Indications: During P2R21, cracks were observed at the AA335740 W7 fillet weld at the hold down rod interface to the support ring for all four (4) hold down rod locations at 37.75, 142.25, 217.75 and 322.25 degree azimuths. The non-structural fillet welds (AA335740 W7) of the hold down rod are for positioning and anti-rotation during construction. In that function, as construction welds, they do not carry primary load. The hold down rod function does not depend on the non-structural AA335740 W7 fillet weld. During plant operation, the positioning at the bottom of the hold down rod is guaranteed by the threaded bottom part; and the rotation is maintained on top by the top bracket and its structural hold down rod top to rod AA335740 W10 weld. The AA 335740 W7 non-structural welds are not credited to show ASME Ill Code compliance for the hold down function. The purpose for including this weld in the inspection plan was primarily due to its inclusion in BWRVIP-139-A, which requires inspection of similar locations on GE steam dryer based on previous operating experience. Based on review of the purpose of the fillet weld, the critical aspect of the inspection for the hold down rod attachment to the ring is the integrity of the threaded connection at the ring attachment location. The inspection has confirmed no crack extension into the rod and no crack extension into the rod is anticipated. The top bracket with its structural welds AA335740 W10 maintains position, prevents rotation and assures thread engagement, thus eliminating any risk for loose parts. The design stress margins for the top bracket remain unchanged by the cracking of the construction fillet welds at the bottom support ring location. No repair is required to the non-structural welds at the bottom of the hold down rods. The AA335740 W7 locations will be re-inspected during P2R22 to confirm no crack extension into the hold down rod at the ring attachment location or crack initiation at the upper bracket welds. These conditions do not impact the HDRs ability to perform their function of preventing uncontrolled lift off after stream line break in faulted condition. No linear indications (fatigue or IGSCC cracks) were identified on any of the lifting rods or at the top of the hold down rod assemblies. As such, there is no degradation mechanism present that could impact the integrity of the attachment weld to the top of the HOR bracket, or the integrity of the HOR itself.

Conclusion:

A complete baseline inspection of the Peach Bottom Unit 2 Steam Dryer was performed during the fall 2016 refueling outage 21. The baseline inspection included successful visual inspection of all of the inspection locations required by the Facility Operating License Condition 2.C(15)(f) for inspection of the Replacement Steam Dryer. All observations were acceptable for the structural components and welds inspected. There were four non-structural welds found with cracks that were dispositioned acceptable is. These welds were not explicitly modeled or analyzed as part of the structural qualification of the dryer. The subsequent inspection scope of the steam dryer will be performed during the Unit 2 P2R22 in 2018 and the results will be provided at that time consistent with the Peach Bottom Operating License.