ML20181A308
ML20181A308 | |
Person / Time | |
---|---|
Site: | Surry |
Issue date: | 06/23/2020 |
From: | Mladen F Virginia Electric & Power Co (VEPCO) |
To: | Document Control Desk, Office of Nuclear Reactor Regulation |
References | |
20-240 | |
Download: ML20181A308 (11) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 JUN23,2020 United States Nuclear Regulatory Commission Serial No.: 20-240 Attention: Document Control Desk SPS LIC/MMT RO Washington, DC 20555-0001 Docket No.: 50-280 License No.: DPR-32 VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNIT 1 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION 2019 STEAM GENERATOR INSERVICE INSPECTION REPORT By letter dated March 11, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20087H009), Virginia Electric and Power Company (Dominion Energy Virginia) submitted information summarizing the results of steam generator (SG) tube inspections performed at Surry Power Station Unit 1 during the fall 2019 refueling outage. On June 4, 2020, the NRC requested additional information related to the SG inspections. The NRC's question and Dominion Energy Virginia's response are provided in the attachment to this letter.
If you have any questions or require additional information, please contact Mr. Michael True at (757) 365-2446.
Respectfully, Fred Mladen Site Vice President Surry Power Station Attachment - Response to NRC Request for Additional Information Regarding Fall 2019 Steam Generator Tube Inspection Report - Surry Power Station Unit 1 Commitments made in this letter: None
Serial No.: 20-240 Docket No.: 50-280 Page 2 of 2 cc: U.S. Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, Georgia 30303 Mr. Vaughn Thomas - Surry NRC Project Manager U.S. Nuclear Regulatory Commission One White Flint North Mail Stop 04 F-12 11555 Rockville Pike Rockville, Maryland 20852 Mr. G. Edward Miller - North Anna NRC Sr. Project Manager U.S. Nuclear Regulatory Commission One White Flint North Mail Stop 09 E-3 11555 Rockville Pike Rockville, Maryland 20852 NRC Senior Resident Inspector Surry Power Station Mr. R. A. Smith Authorized Nuclear Inspector Surry Power Station
Serial No.: 20-240 Docket No.: 50-280 ATTACHMENT Response to NRC Request for Additional Information Regarding Fall 2019 Steam Generator Tube Inspection Report Surry Power Station Unit 1 Virginia Electric and Power Company (Dominion Energy Virginia)
Serial No.: 20-240 Docket No.: 50-280 Attachment RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING SURRY UNIT 1 FALL 2019 STEAM GENERATOR TUBE INSPECTIONS NRC Comment By letter dated March 11, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20087H009), Virginia Electric and Power Company (the licensee) submitted information summarizing the results of the fall 2019 steam generator tube inspections performed at Surry Power Station (Surry), Unit 1. These inspections were performed during refueling outage (RFO) 29. Technical Specification (TS) 6.6.A.3 requires that a report be submitted within 180 days after Tavg exceeds 200°F following completion of an inspection of the SGs performed in accordance with TS 6.4. Q, "Steam Generator (SG) Program."
To complete its review of the inspection report, the U.S. Nuclear Regulatory Commission staff requests the following additional information:
- 1. Please clarify the sampling strategy for eddy current examination of features such as dents, dings, and bulges in the Surry Unit 1 SGs. Table 1, "Inspection Method for Applicable Degradation Modes," of the inspection report lists the methods used for inspections, but the report does not identify how inspection methods were applied to some special interest features (for example, the selection criteria for examination of dents and dings with specialized probes).
Response
An eddy current examination is performed on each steam generator at Surry Power Station every other refueling outage. The in-service tube base scope includes a 100%
bobbin probe exam, 100% array probe exam of the top-of-tubesheet on both the hot-leg and cold-leg (including all overexpansions within the tubesheet down to the H* distance),
100% full length array probe of all "Tier 1" tubes identified with potentially high residual stress, and a +Point' exam of all over rolls (4), bulges (3), and low row (row 1 and 2) U-bends.
In addition to the base scope, a preplanned special interest scope was developed, which includes a sample of previously identified dents, dings, manufacturing burnish marks, volumetric indications, and wear (excluding AVB wear). In total, 162 special interest locations were preplanned to be examined using specialized probes and diagnostic techniques.
The specific dent/ding scope included fifty percent of previously identified dents/dings >2 Volts located in hot-leg straight sections (TSH +0.00 to 07H+1.00"), plus any additional Page 1 of 8
Serial No.: 20-240 Docket No.: 50-280 Attachment indications required to ensure that the five largest voltage dents/dings in hot-leg straight sections are included in the sample. Also, the five largest voltage dents/dings located between the cold-leg tubesheet and the straight section of the hot-leg, (between TSC and 07H+1.01 ") are included in the preplanned scope.
There were 116 in-service tubes with 137 dent/ding indications measuring > 2 Volts on the hot-leg straight section in SG-B reported in 1R27. A 50% sample yields 69 indications for inspection. Fifty-seven (57) indications were not inspected in 1R27 and were preplanned for inspection with +Point' probe during the 1R29 outage. The five largest dents (by voltage) were also included in the sample for inspection. Additional indications from 1R27 were selected to maintain the 50% minimum sample requirement. A total of 70 dent indications in 65 tubes were scheduled for testing.
During the examination, indications are detected including permeability variations, deposits, possible loose parts signals, and ambiguous or anomalous indications, which require additional categorization with diagnostic techniques. These indications are examined with a +Point' probe. The total special interest scope in SG-B during 1R29 was 219 indications.
- 2. With respect to the secondary-side inspections, please clarify for each SG whether foreign objects or loose parts were removed, and the number and type of objects removed.
Response
Surry Power Station has recently escalated efforts to remove all foreign objects from the secondary side of the steam generators. Several foreign objects were removed from each of the three Surry steam generators during 1R29 via water lancing or foreign object search and retrieval activities. Some enhanced, localized in-bundle lancing was also performed to aid in these removal efforts. A description of the foreign objects removed from the Surry steam generators is contained in Table 1.
- 3. Table 3, "Surry 1 EOC29 Inspection Summary- Non-A VB Volumetric Degradation," of the inspection report, which lists non-antivibration bar volumetric degradation, includes an indication in tube Row 33 Column 17, which the staff did not find in previous inspection reports. Please clarify whether this is a legacy indication or a newly reported indication that may be a result of recent degradation. If there is evidence of recent degradation, please discuss if a loose part may still be present. The staff notes that nearby tubes have previously reported loose part indications but without evidence of a loose part remaining.
Page 2 of 8
Serial No.: 20-240 Docket No.: 50-280 Attachment
Response
The indication in Surry Unit 1 SG-B, tube R33 C17 at structure BPH has been reported by bobbin as a Distorted Support Signal (DSS) since 2010. DSS indications receive a special interest inspection with either or both Motorized Rotating Pancake Coil (MRPC) and Array at each inspection. The result of the special interest inspections has consistently been No Degradation Found (NDF), Indication Not Recordable (INR), or in one case, X-Probe Signal (XPS). In the 2019 inspection the Lead Level Ill chose to report the indication as wear (WAR) and estimated the depth at 15% TW using EPRI technique 27901.1. This was a conservative decision based on industry experience of fretting wear from foreign material on the secondary side, the indication's location relative to the structure and the signal's appearance, and response to the various inspection probes. The subject indication is very shallow resulting in varying degrees of detection over the past inspections and shows no change since the 2010 inspection. The area around this tube was thoroughly examined visually to confirm that no foreign object remains at this location.
Page 3 of 8
Serial No.: 20-240 Docket No.: 50-280 Attachment Table 1: Foreign Objects Removed During 1R29 SG-Item# Description Location Configuration ECT Results Estimated Size Fixity 2019 Disposition Legacy cluster of fine wire ECT not Removed Historical (1R24) cluster of Rl4-C49 Not Legacy cluster of fine wire was removed A-4 and sludge located at TSH performed during fine wire and sludge at TSH Rl4-C50 Determined during IR29 TTS lancing.
behind the center tie-rod during IR29 lancing Irregular shaped object ECTnot During I R29 object was both discovered (1R29) Irregular shaped R14-C4 0.75" X 0.38" X A-11 discovered at TSC during performed Retrieved and retrieved from the SG. SSI noted no object at TSC RI4-C5 0.38" post lance SSI during I R29* tube damage during retrieval process.
ECT not During 1R29 object was both discovered R27-CI4 Round object discovered at 0.63" X 0.44" X A-12 (1R29) Round object at TSH performed Retrieved and retrieved from the SG. SSI noted no R26-Cl4 TSH during post lance SSI 0.44" during 1R29 tube damage during removal process.
Irregular shaped object ECTnot During 1R29 object was both discovered
( I R29) Irregular shaped R40-C44 0.81" X 0.44" X A-14 discovered at TSH during performed Retrieved and retrieved from the SG. SSI noted no object at TSH R40-C45 0.38" post lance SSI during lR29 tube damage during retrieval process.
R42-C31 ECTnot During lR29 object was both discovered Flake discovered at TSC LO" x 0.38" x A-15 (1 R29) Flake at TSC R42-C30 performed Retrieved and retrieved from the SG. SSI noted no during post lance SSI 0.06" R43-C31 during 1R29 tube damage during retrieval process.
R44-C37 ECTnot During I R29 object was both discovered Piece of scale discovered at 0.50" X 0.38 X A-16 (1 R29) Scale at TSC R44-C36 performed Retrieved and retrieved from the SG. SSI noted no TSC during post lance SS! 0.06" R43-C36 during IR29 tube damage during retrieval process.
Irregular shaped object ECTnot During IR29 object was both discovered (IR29) Irregular shaped 0.50" X 0.31" X A-17 R44-C38 discovered at TSC during performed Retrieved and retrieved from the SG. SSI noted no object at TSC 0.06" post lance SSI during IR29 tube damage during retrieval process.
Irregular shaped object ECTnot During 1R29 object was both discovered
( l R29) Irregular shaped R45-C44 0.56" X 0.44" X A-18 discovered at TSC during performed Retrieved and retrieved from the SG. SSI noted no object at TSC R45-C45 0.06" post lance SSI during IR29 tube damage during retrieval process.
Irregular shaped object ECTnot During 1R29 object was both discovered
( I R29) Irregular shaped R46-C46 0.63" X 0.38" X A-19 discovered at TSC during performed Retrieved and retrieved from the SG. SSI noted no object at TSC R46-C45 0.06" post lance SSI during 1R29 tube damage during retrieval process.
ECTnot During lR29 object was both discovered (IR29) Round object R2-C93 Round object discovered at 0.50" X 0.44" X A-20 performed Retrieved and retrieved from the SG. SSI noted no atTSH R3-C93 TSH during post lance SSI 0.44" during lR29 tube damage during retrieval process.
R39-C65 Irregular shaped object ECTnot During 1R29 object was both discovered
( I R29) Irregular object at R38-C65 0.40"x0.40"x A-23 discovered at TSH during performed Retrieved and retrieved from the SG. SSI noted no TSH R38-C64 0.30" post lance SSI during IR29 tube damage during retrieval process.
R39-C64 Page 4 of 8
Serial No.: 20-240 Docket No.: 50-280 Attachment SG-Item# Description Location Configuration ECT Results Estimated Size Fixity 2019 Disposition Irregular shaped object ECT not During I R29 object was both discovered (I R29) Irregular object at R4-C83 0.75" X 0.38" X A-24 discovered at TSH during performed Retrieved and retrieved from the SG. SSI noted no TSH R4-C82 0.40
post lance SSI during IR29 tube damage during retrieval process.
Irregular shaped object ECT not No During l R29 object was both discovered (IR29) Irregular object at Rl-C74 A-25 discovered at TSH during performed measurement Retrieved and retrieved from the SG. SSI noted no TSH RI-C75 post lance SSI during IR29 taken tube damage during retrieval process.
During IR29, many objects were Parts captured in the lancing Various parts captured in the SG A lancing strainers.
A-27 (1R29) Lancing strainer parts TTS strainers during I R29 TIS NIA ranging from Removed Most are sludge related. There were also lancing - I/8" to -1/2" fragments of small diameter wire and flex gasket material.
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., ..... '.":*,"' "':::*.,:*;:/*:;<:*: ._ ....-.:**:; . *:., .. _,,.,,_.,._,,:., ;-,,; ,:; }";;,','::,; i',':i,:\(+ ..,:,.:::."*?:-':l./.'.'.:*,:,.- .**.*,******_.*:.* ..:/*.-*:;__ :<:-:-:' . ~-:-:*:*'./:\: ,..... :*.:. ~_:.-.*L:**: : _ .....,*-......... ,....
R31-Cl5 /
BPH +0.54 R31-Cl6 I IR29 wear not newly developed, rather Historical (IR21) BPH wear BPH+0.51 newly reported. Wear (R33-CI 7) was Historical foreign object Scale present IR23 and IR25. PLP (R33-Cl8) locations. R32-Cl5 I wear on the H/L side of the pulled due to loose scale adjacent to tube. Scale (JR29) PLP BPH+0.54 WAR B-1 baffle plate NIA back but pulled back but broke apart. No potential R33-CJ8 BPH+0.54 R32-Cl8 I PLP broke for wear growth going forward.
New PLP and WAR at (IR29) WAR BPH+0.55 apart Continue to monitor with ECT affected IR29 R33-Cl7 BPH+0.61 R33-Cl8 / and bounding tubes (bounding of BPH+0.66 plugged and in-service tubes with wear).
R35-C20 I BPH+l.13 Historical (IR27) Lodged R39-C26 During 1R29, object was retrieved prior round object at TSH was R39-C27 Foreign object was retrieved B-7 NOD 0.4" diameter Retrieved to ECT. Array results were INF and retrieved (IR29). Likely hard R40-C26 prior to performing ECT NOD for affected and bounding tube.
sludge. R40-C27 During IR29, object was retrieved prior (IR29) Irregular object at R43-C52 Foreign object was retrieved 0.5" X 0.5" X B-11 NOD Retrieved to ECT. Array results were NOD for TSH. Likely hard sludge. R43-C53 prior to performing ECT 0.15" affected and bounding tubes.
During IR29, many parts were captured Parts captured in the lancing Various parts in the SG B lancing strainers. Most were 8-14 (1R29) Lancing strainer parts TTS strainers during IR29 TIS NIA ranging from Removed sludge related. There were also lancing -118" to -1/2" fragments of flex gasket material.
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Serial No.: 20-240 Docket No.: 50-280 Attachment SG-Item# Description Location Configuration ECT Results I Estimated Size Fixity 2019 Disposition R25-C31 I TSC+2.23" Array PLPs (at TSC) PLP (Array) Small diameter wire was retrieved from (I R29) Array PLPs (three R26-C31 I Wire B-16 tubes) confirmed with +Point TSC+l.74" confirmed with +Point. PLP (+Point) 3.8" X 0.1" Retrieved I tube locations with PLP. No associated Confirmed as a wire. No wear wear. No future threat to tube integrity.
R27-C32 I TSC+l.17" I;'.'\i;> q::,F;',{, ii>::,, *,*.*: :,;;:'.:1:~:::... :. '* ***.
1 Referred to previously as I Historical (I R20) hard RI-C48 /
TSH "debris" but it is actually hard deposit material ECT not I via Removed I P"'1-l~<iag, the depositioa w~ ao slud e long_er present. _Tubes _have been C-2 performed NIA sludge I Rl-C47 /
TSH between the affected tubes.
The material was removed during 1R29 I . g 1ancmg routinely examined with no wear identified.
by sludge lancing R30-C48 C-28 I ( l R29) Ring shaped object at TSC I R30-C49 R31-C48 Ring shaped object resembling the skeleton of a ECTnot performed 0.8"x 0.25" Retrieved Object was retrieved during I R29 pre-lance inspection. No evidence of tube hex nut at TSC during 1R29 damage identified by SSL R3 I-C49 Sludge rock that Broke ECTnot Sludge rock disintegrated during pre-C-29 I ( 1R29) Soft sludge rock at R40-C47 disintegrated (C/L) during performed Disintegrated apart lance retrieval attempt. Poses no threat to TSC R40-C48 retrieval attempt. Debris during during IR29 tube integrity going forward.
remains in the SG retrieval (I R29) Small strip Objects resembles a small ECTnot Object was retrieved during 1R29. No R43-C54 0.3" X 0.2"X C-30 I resembling flex gasket piece of flex gasket covered performed 0 ?" Retrieved evidence of tube damage identified by R44-C54 covered in sludge at TSC in sludge at TSC during 1R29 SSL ECTnot Sludge was retrieved during 1R29. No Hard sludge found near the 0.3" X 0. 15" X C-31 I ( I R29) Hard sludge at TSC R44-C60 annulus at TSC performed 0.15" Retrieved evidence of tube damage identified by during 1R29 SSL ECT not Sludge was retrieval during IR29. No R42-C51 0.4" X 0.25" X C-32 I (I R29) Hard sludge at TSH I Hard sludge found at TSH performed Retrieved evidence of tube damage identified by R42-C52 0.15" during 1R29 SSL Scale retrieved from SG and ECT not Scale was retrieved and subsequently R42-C49 C-33 I (1 R29) Soft scale at TSH I R43-C49 broke apart, in hand, outside performed Broke apart Retrieved broke apart outside the SG. Poses no the SO during IR29 threat to tube integrity going forward.
C- 34 I (1R29) Hard sludge/ scale at TSH I R42-C46 R43-C46 Hard sludge found at TSH ECTnot performed 0.15"x0.15" Retrieved Sludge/scale was retrieved during IR29.
No evidence of tube damage identified during 1R29 - -
by SSL Page 6 of 8
Serial No.: 20-240 Docket No.: 50-280 Attachment SG-Item# Description Location Con figuration ECT Results Estimated Size Fixity 2019 Disposition ECT not Sludge/scale was retrieved during IR29.
( I R29) Hard sludge/ scale at R44-C36 Hard sludge / scale found at C-35 performed 0.55" X 0.25" Retrieved No evidence of tube damage identified TSC R44-C37 TSC during IR29 by SSL Round shaped object ECT not Object was retrieved during IR29. No RI-C6 0.55" X 0.45" X C-36 ( I R29) Round object at TSH resembling hard sludge at performed Retrieved evidence of tube damage identified by R2-C6 0.40" TSH during IR29 SSL During IR29, many objects were Parts captured in the lancing Various parts captured in the SG C lancing strainers.
C-39 (IR29) Lancing strainer parts TTS strainers during I R29 TTS NIA ranging from Removed Most are sludge related. There were also lancing -1/8" to -1/2" fragments of small diameter wire and flex gasket material.
(IR29) Semi-circular shaped Semi-circular shaped object ECT not Object was retrieved during IR29. No RI-C43 0.50" X 0.50" X C-40 object at TSH. Likely hard identified during post lance performed Retrieved evidence of tube damage identified by R2-C44 0.25" sludge. FOSAR. during IR29 SSL Small wire with one end ECTnot Object was retrieved during IR29. No C-44 (IR29) Small wire at TSH R6-C29 embedded in hard collars at performed 1.15" Retrieved evidence of tube damage identified by TSH during IR29 SSL ECTnot Sludge rock was retrieval during IR29.
(IR29) Hard sludge rock at R43-C45 Hard sludge rock found at 0.60" X 0.30" X C-45 performed Retrieved No evidence of tube damage identified TSH R44-C45 TSH. 0.30" during IR29 by SSL Page 7 of 8
Serial No.: 20-240 Docket No.: 50-280 Attachment ABBREVIATIONS AND ACRONYMS AILPC Accident Induced Leakage Performance Criteria LPS Loose Part Signal ARC Alternate Repair Criteria MAA Multiple Axial Anomaly AVB Anti-Vibration Bar MBM Manufacturing Burnish Mark BET Bottom of Expansion Transition NDF No Degradation Found BLG Bulge NOPD Normal Operating Pressure Differential BOC Beginning Of Cycle NTE No Tube Expansion BPC Baffle Plate Cold QA Operational Assessment BPH Baffle Plate Hot ODSCC Outer Diameter Stress Corrosion Cracking CDS Computer Data Screening OVR Over Roll CM Condition Monitoring Assessment OXP Over Expansion CMOA Condition Monitoring and Operational Assessment PARC Permanent Alternate Repair Criteria DA Degradation Assessment PDA Percent Degraded Area DDH Distorted Dent History PIT Pit DOI Distorted Dent w/lndication PLP Possible Loose Part DDS Distorted Dent Signal POD Probability Of Detection DMT Deposit Minimization Treatment PTE Partial Tube Expansion ONT Dent PVN Permeability Variation ECT Eddy Current Test PWSCC Primary Water Stress Corrosion Cracking EFPY Effective Full Power Years QDA Qualified Data Analyst EOC End Of Cycle REOC Replacement End Of Cycle ETSS Examination Technique Specification Sheet RPC Rotating Pancake Coil (generic term for all rotating probes)
FAC Flow Assisted Corrosion SAA Single Axial Anomaly FOB Flow Distribution Baffle SCC Stress Corrosion Cracking FK Foreign Object Tracking System Key SG Steam Generator FOSAR Foreign Object Search And Retrieval SIPC Structural Integrity Performance Criteria FOTS Foreign Object Tracking System SSI Secondary Side Inspection GPO Gallons Per Day TSC Tube Sheet Cold HRS High Residual Stress TSH Tube Sheet Hot INF Indication Not Found TSP Tube Support Plate INR Indication Not Reportable TTS Top of Tubesheet LGV Local Geometry Variation TW Through Wall LPM Loose Part Monitoring VOL Volumetric Page 8 of 8