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| number = ML11208C216
| number = ML11208C216
| issue date = 08/16/2011
| issue date = 08/16/2011
| title = 06/06/2011 Sequoyah Nuclear Plant, Unit 2 - Spring 2011 Refueling Outage Steam Generator Tube Inservice Inspection Conference Call Summary (TAC No. ME5977)
| title = Spring 2011 Refueling Outage Steam Generator Tube Inservice Inspection Conference Call Summary
| author name = Lingam S P
| author name = Lingam S
| author affiliation = NRC/NRR/DORL/LPLII-2
| author affiliation = NRC/NRR/DORL/LPLII-2
| addressee name = Krich R M
| addressee name = Krich R
| addressee affiliation = Tennessee Valley Authority
| addressee affiliation = Tennessee Valley Authority
| docket = 05000328
| docket = 05000328
| license number = DPR-079
| license number = DPR-079
| contact person = Lingam S P
| contact person = Lingam S
| case reference number = TAC ME5977
| case reference number = TAC ME5977
| document type = Letter, Meeting Summary
| document type = Letter, Meeting Summary
Line 18: Line 18:


=Text=
=Text=
{{#Wiki_filter:UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 August 16, 2011 Mr. Rodney M. Krich Vice President, Nuclear Licensing Tennessee Valley Authority 3R Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 SEOUOYAH NUCLEAR PLANT, UNIT 2 -SPRING 2011 REFUELING OUTAGE STEAM GENERATOR TUBE INSERVICE INSPECTION CONFERENCE CALL SUMMARY (TAC NO. ME5977)
{{#Wiki_filter:UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 August 16, 2011 Mr. Rodney M. Krich Vice President, Nuclear Licensing Tennessee Valley Authority 3R Lookout Place 1101 Market Street Chattanooga, TN 37402-2801


==Dear Mr. Krich On June 6,==
==SUBJECT:==
2011, the Nuclear Regulatory Commission staff participated in a conference call with Sequoyah Nuclear Plant, Unit 2 (SON) representatives regarding SON's spring 2011 refueling outage steam generator tube inspections. Enclosed is a summary of that conference call. If you have any questions regarding this summary, please contact me at 301-415-1564. Sincerely, Siva P. Lingam, Project Manager Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-328  
SEOUOYAH NUCLEAR PLANT, UNIT 2 - SPRING 2011 REFUELING OUTAGE STEAM GENERATOR TUBE INSERVICE INSPECTION CONFERENCE CALL
 
==SUMMARY==
(TAC NO. ME5977)
Dear Mr. Krich On June 6, 2011, the Nuclear Regulatory Commission staff participated in a conference call with Sequoyah Nuclear Plant, Unit 2 (SON) representatives regarding SON's spring 2011 refueling outage steam generator tube inspections. Enclosed is a summary of that conference call.
If you have any questions regarding this summary, please contact me at 301-415-1564.
Sincerely,
                                              ~~'~~
Siva P. Lingam, Project Manager Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-328


==Enclosure:==
==Enclosure:==
Conference Call Summary cc w/encl: Distribution via Listserv SUMMARY OF CONFERENCE CALL WITH SEOUOYAH NUCLEAR PLANT, UNIT 2 REGARDING SPRING 2011 STEAM GENERATOR TUBE INSPECTION RESULTS TENNESSEE VALLEY AUTHORITY DOCKET NO. 50-328 On June 6, 2011, the Nuclear Regulatory Commission (NRC) staff participated in conference call with Tennessee Valley Authority (TVA, the licensee) representatives associated with the Sequoyah Nuclear Plant, Unit 2 (SON 2) spring 2011 refueling outage steam generator (SG) tube inspections. The four SGs at SON 2 are Westinghouse model 51 SGs. Each SG contains 3,388 mill annealed Alloy 600 tubes. Each tube has a nominal outside diameter (00) of 0.875 inches and a nominal wall thickness of 0.050 inches. The tubes are supported by a number of carbon steel tube support plates and Alloy 600 anti-vibration bars. The tubes were explosively expanded into the tubesheet at both ends for the full length of the tubesheet. The U-bend region of the small radius tubes (i.e., rows 1 and 2) were in-situ stress relieved by heat treating following Cycle 6 (the row 1 tubes were plugged following Cycle 3 and were unplugged, inspected, and stress relieved following Cycle 6). In addition to a depth-based tube repair criteria, the licensee is authorized to apply the voltage-based tube repair criteria to predominantly axially-oriented outside diameter stress corrosion cracking (ODSCC) indications at the tube support plate elevations. The licensee is also authorized to leave flaws within the tubesheet region in service, provided they satisfy the W* repair criterion. Information provided by the licensee is summarized below: There was no detectable primary-to-secondary leakage during the operating cycle preceding the 2011 refueling outage. No secondary side pressure tests were performed. No exceptions were taken to the industry SG guidelines. A full length bobbin probe inspection was performed on 100 percent of non-plugged tubes, except for the U-bend region of the tubes in rows 1-10. A magnetically biased +Point probe will be used to inspect the U-bend region of the tubes in rows 1-4. An array probe will be used to inspect the U-bend region of the tubes in rows 5-10. In the U-bend region, if a circumferential indication is detected in rows 9 or 10, the U-bend region of 100 percent of the tubes in rows 11-20 will be inspected in the affected SG. If a Enclosure 
Conference Call Summary cc w/encl: Distribution via Listserv
-2 crack-like indication is detected in rows 15-20, then the U-bend region of 100 percent of the tubes will be inspected in the affected SG. If an axial crack-like indication is detected in rows 3-8, then the U-bend region of 100 percent of the tubes in rows 9-16,50 percent of the tubes in row 17, and 20 percent of the tubes in row 18 will be inspected in the affected SG. This latter sample may be expanded to include 100 percent of the tubes in rows 11-25 if additional crack-like indications are detected. At the time of the conference call, an axial crack-like indication had been detected in the U-bend region of a row 1 tube. This tube was being evaluated to determine if in-situ pressure testing was required. 100 percent of the dents in the U-bend will be inspected with a +Point probe. 100 percent of the dings at the anti-vibration bars will be inspected with a +Point probe. 100 percent of dings at manufacturing burnishing marks will be inspected with a +Point probe. All cold-leg and hot-leg tube support elevations were inspected with a bobbin probe. A +Point probe will be used to inspect all distorted support indication with a bobbin voltage amplitude of 1 volt or greater. A +Point probe will be used to inspect 100 percent of the tubes from 2 inches above to 8 inches below the top of the tubesheet on the hot-leg side of the SG. A +Point probe will be used to inspect 20 percent of the tubes from 2 inches above to 10.5 inches below the top of the tubesheet on the cold-leg side of the SG. If a craCk-like indication is detected in this sample, 100 percent of the tubes will be inspected from 2 inches above to 10.5 inches below the top of the tubesheet on the cold-leg side in the affected SG. If additional indications are found in this sample, 100 percent of the tubes in all SGs will be inspected from 2 inches above to 10.5 inches below the top of the tubesheet on the cold-leg side. No cracking had been detected on the cold-leg at the time of the conference call. Freespan dents greater than or equal to 2 volts on the hot-leg from the top of the tubesheet to the seventh hot-leg support will be inspected with a +Point probe. The guidance regarding rotating probe examinations in Generic Letter 95-05 will be used to inspect tube support plate intersections. 100 percent of the dents from the first hot-leg tube support plate to the sixth cold-leg tube support plate with bobbin voltage amplitudes greater than or equal to 2 volts will be inspected with a +Point probe. This sample will be expanded to include lower tube support plates on the cold-leg side if indications are detected at the next higher tube support plate. 
-3 100 percent of the dents from the first cold-leg tube support plate to the fifth cold-leg tube support plate with bobbin voltage amplitudes greater than or equal to 5 volts will be inspected with a +Point probe. If crack-like indications are detected in this sample, 100 percent of the dents from the fifth cold-leg tube support plate to the support plate below the support plate where the indication was detected with bobbin voltage amplitudes greater than or equal to 2 volts will be inspected with a +Point probe. 100 percent of the freespan paired dents/dings will be inspected with a +Point probe. Paired dents/dings are those that are within approximately % of an inch of each other along the length of the tube. At the time of the conference call, the licensee had reported the following number of indications in the table below. The inspections were approximately 95 percent complete. The following abbreviations are used in the table: AVB -anti-vibration bar Circ -circumferential TSP -tube support plate TTS -top of tubesheet PWSCC -Primary water stress corrosion cracking ODSCC -Outer diameter stress corrosion cracking Degradation Type SG 1 SG2 SG3 SG4 Notes AVBWear 13 39 19 17 None greater than 40% through wall Cold-Leg Thinning 44 99 48 47 3 of these indications will need to be plugged i Freespan ODSCC 0 2 0 0 The two indications are in one tube (see below bullet) Loose Parts Wear 0 0 0 0 Possible loose parts detected, but no wear. Cracking in Sludge Pile 0 1 0 0 Degradation Type SG 1 SG2 SG3 SG4 Notes AxialOOSCC at TSPs 613 550 782 1472 11 tubes will be plugged Volumetric indication with a circ component 0 0 1 0 Cellular intergranular attack AxialOOSCC atTTS 0 2 2 1 4 tubes will be plugged (2 indications in one tube) Circ OOSCC atTTS 0 4 0 6 9 tubes will be plugged (2 indications in one tube) and stabilized Circ OOSCC in U-bend 0 0 0 0 Axial PWSCC at TSPs 0 0 0 0 May be one indication Circ PWSCC at TSPs 0 0 0 0 Axial PWSCC atTTS 0 0 1 0 Will plug Circ PWSCC atTTS 0 1 0 0 Will plug Axial PWSCC in U-bend 0 1 0 0 Will plug CircPWSCC in U-bend 0 0 0 0 The freespan ODSCC indications were detected by the bobbin coil. The voltages associated with the indications were 0.43 and 0.53 volts. The indications extended from approximately 3 to 4 inches below the third cold-leg tube support up to the third cold-leg tube support. Minimum traces of scale were identified on the tubes and there was no ready explanation for why this tube cracked. No tubes are planned to be pulled this outage. For the detection of loose parts, both eddy current and visual inspections are performed. The inspection of the top of tubesheet region on the COld-leg was focused on peripheral tubes. Foreign object search and retrieval (FOSAR) had not yet been performed. Roughly 20 loose parts were previously identified during previous outages in the Unit 2 SGs.
Any possible loose part indications that are not visually inspected or any loose part that is not removed by FOSAR will be evaluated to ensure the loose parUpossible loose part may be left in service. All tubes with crack like indications will be plugged with mechanical plugs. Tubes with circumferential crack-like indications will be stabilized. Mechanical plugs will be used in all tubes that are plugged. No sludge lancing is scheduled to be performed this outage. There have been no unexpected results during the outage. The licensee stated that this outage is the last scheduled inspection of these SGs since they will be replaced during the next refueling outage. The NRC staff did not identify any issues that required follow-up action at this time; however, the NRC staff asked to be notified in the event that any unusual conditions were detected during the remainder of the outage or if a tube fails an in-situ pressure test.
August 16, 2011 Mr. Rodney M. Krich Vice President, Nuclear Licensing Tennessee Valley Authority 3R Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 SEOUOYAH NUCLEAR PLANT, UNIT 2 -SPRING 2011 REFUELING OUTAGE STEAM GENERATOR TUBE INSERVICE INSPECTION CONFERENCE CALL SUMMARY (TAC NO. ME5977)


==Dear Mr. Krich On June 6,==
==SUMMARY==
2011, the Nuclear Regulatory Commission staff participated in a conference call with Sequoyah Nuclear Plant, Unit 2 (SON) representatives regarding SON's spring 2011 refueling outage steam generator tube inspections. Enclosed is a summary of that conference call. If you have any questions regarding this summary, please contact me at 301-415-1564. Sincerely, IRA! Siva P. Lingam, Project Manager Plant Licensing Branch 11-2 Division of Operating Reactor licensing Office of Nuclear Reactor Regulation Docket No. 50-328  
OF CONFERENCE CALL WITH SEOUOYAH NUCLEAR PLANT, UNIT 2 REGARDING SPRING 2011 STEAM GENERATOR TUBE INSPECTION RESULTS TENNESSEE VALLEY AUTHORITY DOCKET NO. 50-328 On June 6, 2011, the Nuclear Regulatory Commission (NRC) staff participated in conference call with Tennessee Valley Authority (TVA, the licensee) representatives associated with the Sequoyah Nuclear Plant, Unit 2 (SON 2) spring 2011 refueling outage steam generator (SG) tube inspections.
The four SGs at SON 2 are Westinghouse model 51 SGs. Each SG contains 3,388 mill annealed Alloy 600 tubes. Each tube has a nominal outside diameter (00) of 0.875 inches and a nominal wall thickness of 0.050 inches. The tubes are supported by a number of carbon steel tube support plates and Alloy 600 anti-vibration bars. The tubes were explosively expanded into the tubesheet at both ends for the full length of the tubesheet. The U-bend region of the small radius tubes (i.e., rows 1 and 2) were in-situ stress relieved by heat treating following Cycle 6 (the row 1 tubes were plugged following Cycle 3 and were unplugged, inspected, and stress relieved following Cycle 6).
In addition to a depth-based tube repair criteria, the licensee is authorized to apply the voltage-based tube repair criteria to predominantly axially-oriented outside diameter stress corrosion cracking (ODSCC) indications at the tube support plate elevations. The licensee is also authorized to leave flaws within the tubesheet region in service, provided they satisfy the W* repair criterion.
Information provided by the licensee is summarized below:
* There was no detectable primary-to-secondary leakage during the operating cycle preceding the 2011 refueling outage.
* No secondary side pressure tests were performed.
* No exceptions were taken to the industry SG guidelines.
* A full length bobbin probe inspection was performed on 100 percent of non-plugged tubes, except for the U-bend region of the tubes in rows 1-10.
* A magnetically biased +Point probe will be used to inspect the U-bend region of the tubes in rows 1-4. An array probe will be used to inspect the U-bend region of the tubes in rows 5-10.
* In the U-bend region, if a circumferential indication is detected in rows 9 or 10, the U-bend region of 100 percent of the tubes in rows 11-20 will be inspected in the affected SG. If a Enclosure
 
                                              -2 crack-like indication is detected in rows 15-20, then the U-bend region of 100 percent of the tubes will be inspected in the affected SG.
* If an axial crack-like indication is detected in rows 3-8, then the U-bend region of 100 percent of the tubes in rows 9-16,50 percent of the tubes in row 17, and 20 percent of the tubes in row 18 will be inspected in the affected SG. This latter sample may be expanded to include 100 percent of the tubes in rows 11-25 if additional crack-like indications are detected.
* At the time of the conference call, an axial crack-like indication had been detected in the U-bend region of a row 1 tube. This tube was being evaluated to determine if in-situ pressure testing was required.
* 100 percent of the dents in the U-bend will be inspected with a +Point probe.
* 100 percent of the dings at the anti-vibration bars will be inspected with a +Point probe.
* 100 percent of dings at manufacturing burnishing marks will be inspected with a +Point probe.
* All cold-leg and hot-leg tube support elevations were inspected with a bobbin probe.
* A +Point probe will be used to inspect all distorted support indication with a bobbin voltage amplitude of 1 volt or greater.
* A +Point probe will be used to inspect 100 percent of the tubes from 2 inches above to 8 inches below the top of the tubesheet on the hot-leg side of the SG.
* A +Point probe will be used to inspect 20 percent of the tubes from 2 inches above to 10.5 inches below the top of the tubesheet on the cold-leg side of the SG. If a craCk-like indication is detected in this sample, 100 percent of the tubes will be inspected from 2 inches above to 10.5 inches below the top of the tubesheet on the cold-leg side in the affected SG. If additional indications are found in this sample, 100 percent of the tubes in all SGs will be inspected from 2 inches above to 10.5 inches below the top of the tubesheet on the cold-leg side. No cracking had been detected on the cold-leg at the time of the conference call.
* Freespan dents greater than or equal to 2 volts on the hot-leg from the top of the tubesheet to the seventh hot-leg support will be inspected with a +Point probe.
* The guidance regarding rotating probe examinations in Generic Letter 95-05 will be used to inspect tube support plate intersections.
* 100 percent of the dents from the first hot-leg tube support plate to the sixth cold-leg tube support plate with bobbin voltage amplitudes greater than or equal to 2 volts will be inspected with a +Point probe. This sample will be expanded to include lower tube support plates on the cold-leg side if indications are detected at the next higher tube support plate.
 
                                                    -3
* 100 percent of the dents from the first cold-leg tube support plate to the fifth cold-leg tube support plate with bobbin voltage amplitudes greater than or equal to 5 volts will be inspected with a +Point probe. If crack-like indications are detected in this sample, 100 percent of the dents from the fifth cold-leg tube support plate to the support plate below the support plate where the indication was detected with bobbin voltage amplitudes greater than or equal to 2 volts will be inspected with a +Point probe.
* 100 percent of the freespan paired dents/dings will be inspected with a +Point probe. Paired dents/dings are those that are within approximately % of an inch of each other along the length of the tube.
At the time of the conference call, the licensee had reported the following number of indications in the table below. The inspections were approximately 95 percent complete. The following abbreviations are used in the table:
* AVB - anti-vibration bar
* Circ - circumferential
* TSP - tube support plate
* TTS - top of tubesheet
* PWSCC - Primary water stress corrosion cracking
* ODSCC - Outer diameter stress corrosion cracking Degradation        SG 1            SG2              SG3            SG4                Notes Type AVBWear            13              39                19              17                None greater than 40%
through wall Cold-Leg          44              99                48            47                  3 of these Thinning                                                                                indications will need to be plugged i Freespan          0                2                0              0                  The two ODSCC                                                                                    indications are in one tube (see below bullet)
Loose Parts        0                0                0              0                  Possible Wear                                                                                    loose parts detected, but no wear.
Cracking in        0                1                0              0 Sludge Pile
 
                                                -4 Degradation      SG 1            SG2              SG3            SG4              Notes Type AxialOOSCC      613              550              782            1472            11 tubes will at TSPs                                                                              be plugged Volumetric      0                0                1              0                Cellular indication with                                                                      intergranular a circ                                                                              attack component AxialOOSCC      0                2                2              1                4 tubes will be atTTS                                                                                plugged (2 indications in one tube)
Circ OOSCC      0                4                0              6                9 tubes will be atTTS                                                                                plugged (2 indications in one tube) and stabilized Circ OOSCC      0                0                0              0 in U-bend Axial PWSCC      0                0                0              0                May be one at TSPs                                                                              indication Circ PWSCC      0                0                0              0 at TSPs Axial PWSCC      0                0                1              0                Will plug atTTS Circ PWSCC      0                1                0              0                Will plug atTTS Axial PWSCC      0                1                0              0                Will plug in U-bend CircPWSCC        0                0                0              0 in U-bend
* The freespan ODSCC indications were detected by the bobbin coil. The voltages associated with the indications were 0.43 and 0.53 volts. The indications extended from approximately 3 to 4 inches below the third cold-leg tube support up to the third cold-leg tube support. Minimum traces of scale were identified on the tubes and there was no ready explanation for why this tube cracked.
* No tubes are planned to be pulled this outage.
* For the detection of loose parts, both eddy current and visual inspections are performed.
The inspection of the top of tubesheet region on the COld-leg was focused on peripheral tubes. Foreign object search and retrieval (FOSAR) had not yet been performed. Roughly 20 loose parts were previously identified during previous outages in the Unit 2 SGs.
 
                                                -5
* Any possible loose part indications that are not visually inspected or any loose part that is not removed by FOSAR will be evaluated to ensure the loose parUpossible loose part may be left in service.
* All tubes with crack like indications will be plugged with mechanical plugs. Tubes with circumferential crack-like indications will be stabilized. Mechanical plugs will be used in all tubes that are plugged.
* No sludge lancing is scheduled to be performed this outage.
* There have been no unexpected results during the outage.
* The licensee stated that this outage is the last scheduled inspection of these SGs since they will be replaced during the next refueling outage.
The NRC staff did not identify any issues that required follow-up action at this time; however, the NRC staff asked to be notified in the event that any unusual conditions were detected during the remainder of the outage or if a tube fails an in-situ pressure test.
 
August 16, 2011 Mr. Rodney M. Krich Vice President, Nuclear Licensing Tennessee Valley Authority 3R Lookout Place 1101 Market Street Chattanooga, TN 37402-2801
 
==SUBJECT:==
SEOUOYAH NUCLEAR PLANT, UNIT 2 - SPRING 2011 REFUELING OUTAGE STEAM GENERATOR TUBE INSERVICE INSPECTION CONFERENCE CALL
 
==SUMMARY==
(TAC NO. ME5977)
Dear Mr. Krich On June 6,2011, the Nuclear Regulatory Commission staff participated in a conference call with Sequoyah Nuclear Plant, Unit 2 (SON) representatives regarding SON's spring 2011 refueling outage steam generator tube inspections. Enclosed is a summary of that conference call.
If you have any questions regarding this summary, please contact me at 301-415-1564.
Sincerely, IRA!
Siva P. Lingam, Project Manager Plant Licensing Branch 11-2 Division of Operating Reactor licensing Office of Nuclear Reactor Regulation Docket No. 50-328


==Enclosure:==
==Enclosure:==
Conference Call Summary cc w/encl: Distribution via Listserv Distribution: PUBLIC LPL2-2 R/F RidsNrrDorlLpl2-2 RidsNrrPMSequoyah RidsOgcRp RidsNrrLACSola (Hard Copy) RidsAcrsAcnw_MailCTR RidsRgn2MailCenter RidsNrrDciCsgb RidsNrrDorlDpr KKarwoski. NRR AObodoako. NRR ADAMS ACCESSION NO.: ML11208C216 *b memo FICE LPL2-2/PM LPL2-2/LA CSGB/BC SLingam CSoia RTaylor* 07128/11 07/28/11 07/18/2011 LPL2-2/BC DBroaddus 08/16/11 LPL2-2/PM SLingam 08/16/11 OFFICIAL AGENCY RECORD
Conference Call Summary cc w/encl: Distribution via Listserv Distribution:
}}
PUBLIC                           LPL2-2 R/F               RidsNrrDorlLpl2-2 RidsNrrPMSequoyah               RidsOgcRp                 RidsNrrLACSola (Hard Copy)
RidsAcrsAcnw_MailCTR             RidsRgn2MailCenter       RidsNrrDciCsgb RidsNrrDorlDpr                   KKarwoski. NRR           AObodoako. NRR ADAMS ACCESSION NO.: ML11208C216                                         *b memo FICE LPL2-2/PM           LPL2-2/LA         CSGB/BC           LPL2-2/BC          LPL2-2/PM SLingam         CSoia             RTaylor*           DBroaddus          SLingam 07128/11         07/28/11           07/18/2011         08/16/11           08/16/11 OFFICIAL AGENCY RECORD}}

Latest revision as of 03:45, 6 December 2019

Spring 2011 Refueling Outage Steam Generator Tube Inservice Inspection Conference Call Summary
ML11208C216
Person / Time
Site: Sequoyah Tennessee Valley Authority icon.png
Issue date: 08/16/2011
From: Siva Lingam
Plant Licensing Branch II
To: Krich R
Tennessee Valley Authority
Lingam S
References
TAC ME5977
Download: ML11208C216 (7)
v • d • e


Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 August 16, 2011 Mr. Rodney M. Krich Vice President, Nuclear Licensing Tennessee Valley Authority 3R Lookout Place 1101 Market Street Chattanooga, TN 37402-2801

SUBJECT:

SEOUOYAH NUCLEAR PLANT, UNIT 2 - SPRING 2011 REFUELING OUTAGE STEAM GENERATOR TUBE INSERVICE INSPECTION CONFERENCE CALL

SUMMARY

(TAC NO. ME5977)

Dear Mr. Krich On June 6, 2011, the Nuclear Regulatory Commission staff participated in a conference call with Sequoyah Nuclear Plant, Unit 2 (SON) representatives regarding SON's spring 2011 refueling outage steam generator tube inspections. Enclosed is a summary of that conference call.

If you have any questions regarding this summary, please contact me at 301-415-1564.

Sincerely,

~~'~~

Siva P. Lingam, Project Manager Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-328

Enclosure:

Conference Call Summary cc w/encl: Distribution via Listserv

SUMMARY

OF CONFERENCE CALL WITH SEOUOYAH NUCLEAR PLANT, UNIT 2 REGARDING SPRING 2011 STEAM GENERATOR TUBE INSPECTION RESULTS TENNESSEE VALLEY AUTHORITY DOCKET NO. 50-328 On June 6, 2011, the Nuclear Regulatory Commission (NRC) staff participated in conference call with Tennessee Valley Authority (TVA, the licensee) representatives associated with the Sequoyah Nuclear Plant, Unit 2 (SON 2) spring 2011 refueling outage steam generator (SG) tube inspections.

The four SGs at SON 2 are Westinghouse model 51 SGs. Each SG contains 3,388 mill annealed Alloy 600 tubes. Each tube has a nominal outside diameter (00) of 0.875 inches and a nominal wall thickness of 0.050 inches. The tubes are supported by a number of carbon steel tube support plates and Alloy 600 anti-vibration bars. The tubes were explosively expanded into the tubesheet at both ends for the full length of the tubesheet. The U-bend region of the small radius tubes (i.e., rows 1 and 2) were in-situ stress relieved by heat treating following Cycle 6 (the row 1 tubes were plugged following Cycle 3 and were unplugged, inspected, and stress relieved following Cycle 6).

In addition to a depth-based tube repair criteria, the licensee is authorized to apply the voltage-based tube repair criteria to predominantly axially-oriented outside diameter stress corrosion cracking (ODSCC) indications at the tube support plate elevations. The licensee is also authorized to leave flaws within the tubesheet region in service, provided they satisfy the W* repair criterion.

Information provided by the licensee is summarized below:

  • There was no detectable primary-to-secondary leakage during the operating cycle preceding the 2011 refueling outage.
  • No secondary side pressure tests were performed.
  • No exceptions were taken to the industry SG guidelines.
  • A full length bobbin probe inspection was performed on 100 percent of non-plugged tubes, except for the U-bend region of the tubes in rows 1-10.
  • A magnetically biased +Point probe will be used to inspect the U-bend region of the tubes in rows 1-4. An array probe will be used to inspect the U-bend region of the tubes in rows 5-10.
  • In the U-bend region, if a circumferential indication is detected in rows 9 or 10, the U-bend region of 100 percent of the tubes in rows 11-20 will be inspected in the affected SG. If a Enclosure

-2 crack-like indication is detected in rows 15-20, then the U-bend region of 100 percent of the tubes will be inspected in the affected SG.

  • If an axial crack-like indication is detected in rows 3-8, then the U-bend region of 100 percent of the tubes in rows 9-16,50 percent of the tubes in row 17, and 20 percent of the tubes in row 18 will be inspected in the affected SG. This latter sample may be expanded to include 100 percent of the tubes in rows 11-25 if additional crack-like indications are detected.
  • At the time of the conference call, an axial crack-like indication had been detected in the U-bend region of a row 1 tube. This tube was being evaluated to determine if in-situ pressure testing was required.
  • 100 percent of the dents in the U-bend will be inspected with a +Point probe.
  • 100 percent of the dings at the anti-vibration bars will be inspected with a +Point probe.
  • 100 percent of dings at manufacturing burnishing marks will be inspected with a +Point probe.
  • All cold-leg and hot-leg tube support elevations were inspected with a bobbin probe.
  • A +Point probe will be used to inspect all distorted support indication with a bobbin voltage amplitude of 1 volt or greater.
  • A +Point probe will be used to inspect 100 percent of the tubes from 2 inches above to 8 inches below the top of the tubesheet on the hot-leg side of the SG.
  • A +Point probe will be used to inspect 20 percent of the tubes from 2 inches above to 10.5 inches below the top of the tubesheet on the cold-leg side of the SG. If a craCk-like indication is detected in this sample, 100 percent of the tubes will be inspected from 2 inches above to 10.5 inches below the top of the tubesheet on the cold-leg side in the affected SG. If additional indications are found in this sample, 100 percent of the tubes in all SGs will be inspected from 2 inches above to 10.5 inches below the top of the tubesheet on the cold-leg side. No cracking had been detected on the cold-leg at the time of the conference call.
  • Freespan dents greater than or equal to 2 volts on the hot-leg from the top of the tubesheet to the seventh hot-leg support will be inspected with a +Point probe.
  • The guidance regarding rotating probe examinations in Generic Letter 95-05 will be used to inspect tube support plate intersections.
  • 100 percent of the dents from the first hot-leg tube support plate to the sixth cold-leg tube support plate with bobbin voltage amplitudes greater than or equal to 2 volts will be inspected with a +Point probe. This sample will be expanded to include lower tube support plates on the cold-leg side if indications are detected at the next higher tube support plate.

-3

  • 100 percent of the dents from the first cold-leg tube support plate to the fifth cold-leg tube support plate with bobbin voltage amplitudes greater than or equal to 5 volts will be inspected with a +Point probe. If crack-like indications are detected in this sample, 100 percent of the dents from the fifth cold-leg tube support plate to the support plate below the support plate where the indication was detected with bobbin voltage amplitudes greater than or equal to 2 volts will be inspected with a +Point probe.
  • 100 percent of the freespan paired dents/dings will be inspected with a +Point probe. Paired dents/dings are those that are within approximately % of an inch of each other along the length of the tube.

At the time of the conference call, the licensee had reported the following number of indications in the table below. The inspections were approximately 95 percent complete. The following abbreviations are used in the table:

  • AVB - anti-vibration bar
  • Circ - circumferential
  • TSP - tube support plate
  • TTS - top of tubesheet

through wall Cold-Leg 44 99 48 47 3 of these Thinning indications will need to be plugged i Freespan 0 2 0 0 The two ODSCC indications are in one tube (see below bullet)

Loose Parts 0 0 0 0 Possible Wear loose parts detected, but no wear.

Cracking in 0 1 0 0 Sludge Pile

-4 Degradation SG 1 SG2 SG3 SG4 Notes Type AxialOOSCC 613 550 782 1472 11 tubes will at TSPs be plugged Volumetric 0 0 1 0 Cellular indication with intergranular a circ attack component AxialOOSCC 0 2 2 1 4 tubes will be atTTS plugged (2 indications in one tube)

Circ OOSCC 0 4 0 6 9 tubes will be atTTS plugged (2 indications in one tube) and stabilized Circ OOSCC 0 0 0 0 in U-bend Axial PWSCC 0 0 0 0 May be one at TSPs indication Circ PWSCC 0 0 0 0 at TSPs Axial PWSCC 0 0 1 0 Will plug atTTS Circ PWSCC 0 1 0 0 Will plug atTTS Axial PWSCC 0 1 0 0 Will plug in U-bend CircPWSCC 0 0 0 0 in U-bend

  • The freespan ODSCC indications were detected by the bobbin coil. The voltages associated with the indications were 0.43 and 0.53 volts. The indications extended from approximately 3 to 4 inches below the third cold-leg tube support up to the third cold-leg tube support. Minimum traces of scale were identified on the tubes and there was no ready explanation for why this tube cracked.
  • No tubes are planned to be pulled this outage.
  • For the detection of loose parts, both eddy current and visual inspections are performed.

The inspection of the top of tubesheet region on the COld-leg was focused on peripheral tubes. Foreign object search and retrieval (FOSAR) had not yet been performed. Roughly 20 loose parts were previously identified during previous outages in the Unit 2 SGs.

-5

  • Any possible loose part indications that are not visually inspected or any loose part that is not removed by FOSAR will be evaluated to ensure the loose parUpossible loose part may be left in service.
  • All tubes with crack like indications will be plugged with mechanical plugs. Tubes with circumferential crack-like indications will be stabilized. Mechanical plugs will be used in all tubes that are plugged.
  • No sludge lancing is scheduled to be performed this outage.
  • There have been no unexpected results during the outage.
  • The licensee stated that this outage is the last scheduled inspection of these SGs since they will be replaced during the next refueling outage.

The NRC staff did not identify any issues that required follow-up action at this time; however, the NRC staff asked to be notified in the event that any unusual conditions were detected during the remainder of the outage or if a tube fails an in-situ pressure test.

August 16, 2011 Mr. Rodney M. Krich Vice President, Nuclear Licensing Tennessee Valley Authority 3R Lookout Place 1101 Market Street Chattanooga, TN 37402-2801

SUBJECT:

SEOUOYAH NUCLEAR PLANT, UNIT 2 - SPRING 2011 REFUELING OUTAGE STEAM GENERATOR TUBE INSERVICE INSPECTION CONFERENCE CALL

SUMMARY

(TAC NO. ME5977)

Dear Mr. Krich On June 6,2011, the Nuclear Regulatory Commission staff participated in a conference call with Sequoyah Nuclear Plant, Unit 2 (SON) representatives regarding SON's spring 2011 refueling outage steam generator tube inspections. Enclosed is a summary of that conference call.

If you have any questions regarding this summary, please contact me at 301-415-1564.

Sincerely, IRA!

Siva P. Lingam, Project Manager Plant Licensing Branch 11-2 Division of Operating Reactor licensing Office of Nuclear Reactor Regulation Docket No. 50-328

Enclosure:

Conference Call Summary cc w/encl: Distribution via Listserv Distribution:

PUBLIC LPL2-2 R/F RidsNrrDorlLpl2-2 RidsNrrPMSequoyah RidsOgcRp RidsNrrLACSola (Hard Copy)

RidsAcrsAcnw_MailCTR RidsRgn2MailCenter RidsNrrDciCsgb RidsNrrDorlDpr KKarwoski. NRR AObodoako. NRR ADAMS ACCESSION NO.: ML11208C216 *b memo FICE LPL2-2/PM LPL2-2/LA CSGB/BC LPL2-2/BC LPL2-2/PM SLingam CSoia RTaylor* DBroaddus SLingam 07128/11 07/28/11 07/18/2011 08/16/11 08/16/11 OFFICIAL AGENCY RECORD

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