ML093360644
| ML093360644 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/10/2009 |
| From: | Siva Lingam Plant Licensing Branch II |
| To: | Swafford P Tennessee Valley Authority |
| Lingam, S NRR/DORL 415-1564 | |
| References | |
| TAC ME2354 | |
| Download: ML093360644 (14) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 December 10, 2009 Mr. Preston D. Swafford Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 3R Lookout Place 1101 Market Street Chattanooga, TN 37402-2801
SUBJECT:
SEOUOYAH NUCLEAR PLANT, UNIT 2 - FALL 2009 REFUELING OUTAGE STEAM GENERATOR TUBE INSERVICE INSPECTION CONFERENCE CALL
SUMMARY
Dear Mr. Swafford:
On November 10 and 18, 2009, the Nuclear Regulatory Commission staff participated in conference calls with Sequoyah Nuclear Plant, Unit 2 (SON) representatives regarding SON's fall 2009 refueling outage steam generator tube inspections. Enclosed is a summary of those conference calls.
If you have any questions regarding this summary, please contact me at 301-415-1564.
Sincerely,
~~i-X~
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:
Summary of Conference Calls cc w/encl: Distribution via Listserv
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 REVIEW OF THE 2008 REFUELING OUTAGE STEAM GENERATOR TUBE INSPECTION REPORTS TENNESSEE VALLEY AUTHORITY SEOUOYAH NUCLEAR PLANT, UNIT 2 DOCKET NO. 50-328 On November 10 and 18, 2009, the Nuclear Regulatory Commission (NRC) staff participated in conference calls with Tennessee Valley Authority (TVA, the licensee) representatives associated with the Sequoyah Nuclear Plant, Unit 2 (SON 2) fall 2009 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. Each tube is roll-expanded for approximately 2.75 inches from the bottom of the tubesheet, and is secured into the remaining portion of the tubesheet by the Westinghouse Explosive Tube Expansion (WEXTEX) process. The tubesheet is approximately 21 inches thick and each tube is expanded for essentially the full thickness of the tubesheet. Each steam generator contains seven carbon steel tube support plates with drilled holes, through which the tubes pass.
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.
At the time of the November 10, 2009, call, SG tube inspections were in progress.
Prior to the November 10, 2009 conference call, the licensee provided a written response to a set of discussion points from the NRC staff (Agencywide Documents Access and Management System Accession No. ML092810089). The written response from the licensee is attached to this enclosure as Attachment 1. Based on the discussions and feedback of the November 10, 2009 conference call, the licensee provided a second set of written responses to follow-on questions that were generated after the November 10, 2009, call. The licensee's response to the follow-on questions is attached to this enclosure as Attachment 2. Additional clarifying information, or information not included in the documents provided by the licensee, is summarized below:
Enclosure
-2 Abbreviations used by the licensee in the attached document include:
- +Pt - +Point'
- ARC - Alternate Repair Criteria
- AVB - Anti-vibration Bar
- BC - Bobbin Coil
- CIRC - Circumferential
- C or C/l or Cl - Cold leg
- Fl - Full length
- FOSAR - Foreign Object Search and Retrieval
- FS - Free Span
- H or H/l or Hl - Hot-leg
- HR - High Row
- Indies - Indications
- lR - low Row
- Mag - Magnetic
- MBM - Manufacturer's Burnish Mark
- MHI - Mitsubishi Heavy Industries "Intelligent Probe
- NOD - No Detectable Degradation
- 00 - Outside Diameter
- ODSCC - Outside Diameter Stress Corrosion Cracking
- PWSCC - Primary Water Stress Corrosion Cracking
- R- Row
- SG or S/G - Steam Generator
- TSP - Tube Support Plate
- TTS - Top of Tubesheet
- UB - U-Bend In Question 10 of Attachment 1, the 4.1 volt maximum predicted voltage for axial ODSCC at the TSPs, was a 99.7 percent upper bound value.
The indications listed in Question 3 of Attachment 2 were initially recorded by bobbin coil examination as distorted support plate indications (DSls). The indications were then examined with a +Pt' rotating probe and the tubes at Row 3 Column 15 and Row 35 Column 19 (in SG 1) were plugged as a result. There were no defects found in the remaining tubes. No circumferential cracking indications were found in dents or dings in any of the SGs.
Regarding the response to Question 5 of Attachment 2, the licensee stated they were evaluating the growth rates observed over the last cycle and would provide the results of the evaluation in the report submitted approximately 90 days after the outage.
Based on the information provided, the NRC staff did not identify any issues that warranted additional follow-up action.
STEAM GENERATOR TUBE INSPECTION DISCUSSION POINTS The following discussion points have been prepared to facilitate the conference call that will be arranged with the licensee to discuss the results of the steam generator tube inspections to be conducted during the upcoming fall 2009, Unit 2 refueling outage for Sequoyah Nuclear Plant. This conference call is scheduled to occur towards the end of the planned SG tube inspections, but before the unit completes the inspections and repairs.
The NRC staff plans to document a summary of the conference call as well as any material that is provided in support of the call.
- 1. Discuss any trends in the amount of primary-to-secondary leakage observed during the recently completed cycle.
On October 1,2009 an approximately 0.17 gpd primary to secondary leak was detected.
The leakage value was unchanged to the end of cycle. Presence of Argon-41 was detected in the condenser vacuum exhaust. Presently, SG 4 has an axial OOSCC indication (approximately 6.55 volts) at a tube support plate which is believed to be the leaking tube.
- 2. Discuss whether any secondary side pressure tests were performed during the outage and the associated results.
No secondary side pressure tests have been performed to date. Contingency plans are in place for a SG pressure test. The 6.55 volt indication will be In-Situ pressure tested to determine if leakage occurs. A SG pressure test will be performed, if needed, as described in the steam generator program.
- 3. Discuss any exceptions taken to the industry guidelines.
No exceptions have been taken.
- 4. For each steam generator, provide a description of the inspections performed including the areas examined and the probes used (e.g., dents/dings, sleeves, expansion-transition, U-bends with a rotating probe), the scope of the inspection (e.g., 100% of dents/dings greater than 5 volts and a 20% sample between 2 and 5 volts), and the expansion criteria.
The following provides number of tubes to be tested, probe types and expansion criteria per degradation mechanism.
BOBBIN FL: 100% of non-plugged tubes in all four generators will be tested full length using a mag-bias bobbin coil probe (Rows 1 through 4 U-bends were examined by Plus Point).
TTS HL: 100% of non-plugged tubes in all four generators will be tested using +Point examination at the hot leg tubesheet expansion transition region (+2/-8).
TTS CL: 100% of non-plugged tubes in all four generators will be tested using +Point examinations at the cold leg tubesheet expansion transition region
(+2/-10.5).
Attachment 1
-2 LR U-BEND: 100% of non-plugged tubes in rows 1 through row 4 in all four generators have been selected for mag-bias U-Bend +Point.
HR U-BEND: 100% of all tubes in rows 5 through row 10 in all four generators have been selected for MHI array probe (or mag-bias U-Bend +Point) inspection.
UB FS DING: 100% of non-plugged u-bend freespan dents (any voltage) found during U2C15 in all four generators have been selected for +Point examination (excluding those tubes in LR U-8end inspection scope).
AVB DING: 100% of non-plugged tubes at AVB locations with dents found during U2C15 in all four generators have been selected for +Point examination.
MBM DING: 100% of non-plugged tubes with both an MBM and DNT at same location found during U2C15 in all four generators have been selected for +Point examination.
HL FS DING: 100% of non-plugged tubes with freespan dents greater than or equal to 2 volts between HTS and H07 found during U2C 15 in all four generators have been selected for +Point examination.
HO 1 thru H07 DENT: 100% of non-plugged tubes with dents found during U2C 15 at each hot support plate in all four generators which were greater than or equal to 2 volts selected for +Point examination.
C07 DENT: 100% of non-plugged tubes with dents found during U2C15 at the seventh cold support plate in all four generators which were greater than or equal to 2 volts selected for +Point examination.
CL FS PAIR DING 100% of non-plugged tubes with cold straight leg freespan "paired dings" (dent calls within 0.75 inches of each other) found during U2C15 in all four generators which were greater than or equal to 2 volts selected for +Point examination.
Location Nomenclature for SON U2 Notation Description HTE Tube end - hot leg AV3 Second anti-vibration bar above C07 HTS Top of tubesheet - hot leg AV4 First anti-vibration bar above C07 H01 First support plate - hot leg C07 Seventh support plate - cold leg H02 Second support plate - hot leg C06 Sixth support plate - cold leg H03 Third support plate - hot leg C05 Fifth support plate - cold leg H04 Fourth support plate - hot leg C04 Fourth support plate - cold leg H05 Fifth support plate - hot leg C03 Third support plate - cold leg H06 Sixth support plate - hot leg C02 Second support plate - cold leg H07 Seventh support plate - hot leg C01 First support plate - cold leg AV1 First anti-vibration bar above H07 CTS Top of tubesheet - cold leg AV2 Second anti-vibration bar above H07 CTE Tube end - cold leg
-3 (Examinations)
DATASET EXTENT TECHNIQUE S/G*1 S/G*2 S/G*3 S/G*4 BOBBIN FL CTE-HTE BOBBIN 3296 3191 3226 3235 TTS HL HTS+2/-8 +Point (or 3296 3191 3226 3235 MHI)
TTS CL CTS+2/-10 IV1HI (or 3296 3191 3226 3235
.5 +Point)
LR U-BEND C07-H07 +Point 338 317 339 340 HR U-BEND C07-H07 MHI (or 546 512 535 511
+Point)
UB FS DING Various +Point 76 22 8 73 U-Bend FS AVB DING Various +Point 3 7 2 33 AVB+1/-1 MBM DING Various +Point -- -- 1 --
HL FS DING Various +Point 103 119 80 23 HTS+2" to H07-1" CL FS PAIR Various CL +Point 10 11 10 2 DING FS C07 DENT C07+1/-1 +Point 148 38 101 142 H01 DENT H01 +1/-1 +Point 22 25 39 3 H02 DENT H02+1/-1 +Point 2 3 3 --
H03 DENT H03+1/-1 +Point 7 16 1 1 H04 DENT H04+1/-1 +Point 3 6 -- 3 H05 DENT H05+1/-1 +Point 25 12 4 7 H06 DENT H06+1/-1 +Point 69 20 30 11 H07 DENT H07+1/-1 +Point 152 56 122 69
-4 EXPANSION CRITERIA PER DAMAGE MECHANISM Damage Location Initial S2C16 Expansion Criteria Mechanism Exam pwscc I ODSCC Axial HL TIS +Pt (+2/-8) 100% HTS HL-N/A no expansion due to 100% initial and Circ in all 4 SGs scope PWSCC I ODSCC Axial CL TIS +Pt (+2/-10.5) 20% CL- indication in initial sample results in 100%
and Circ CTS in all 4 SGs of that SG. 1 indication in expanded sample results in 100% of all S/Gs PWSCC I ODSCC Axial H/L Dings freespan +Pt 100% HTS-H07 in If crack-like indications are identified at and Circ all 4 SGs H06-H07, then 20% of C07-C06 dings in the effected SG PWSCC I ODSCC Axial Dented;:: 2 volts +Pt 100% TSPs If crack-like indications are identified at C07, and Circ TSPs H01-C07 Dented then 100% of C06 will be examined in the
~2Volts in all 4 SGs effected SG.
If circ indics in <2.0 volt dents, then 100% of all H/L dents? 1.0 volts will be examined.
If circ indics in 1.0 to 2.0 volt dented TSPs and structural integrity is challenged, then TVA will develop an expansion plan for less than 1.0 volt dented TSPs.
ODSCC Axial Non-Dented TSPs BC 100% Full Length N/A base scope includes all H/L and C/L in al14 SGs TSPs.
ODSCC Sludge Pile +Pt (+2/-8) or MHI If max sludge height? 2" then ensure 100% HTS in all 4 SGs complete sludqe heiqht is inspected.
ODSCC Freespan BC 100% FL in all 4 N/A 100% BC base scope, +Pt or MHI SGs indications for confirmation PWSCC I ODSCC Rows 1-10 U-bend 100% +Pt Rows1-4 in If> 0 Circ indics in R 9-10 then, 100% of R U-bends regions all SGs, 100% MHI or 11-20 in the effected SG.
+Pt Rows 5-10 in all If> 0 Circ indics in R 15-20 then 100% of all SGs. Bobbin in MHI rows in the effected SG.
U-bends. If >0 Axial indics in R 5-8, then 100% of R5-16, and 50% of R 17 in the effected SG.
If >0 Axial indics in R. 9-10, then 100% of R 11-25 in the effected SG.
AVB Wear U-bends BC100% F/L in al14 N/A 100% base scope, +Pt new indications SGs and those which have chanqed TIS Loose Parts Wear TIS +Pt (+2/-8) 100% HTS, All wear from loose parts and/or PLPs will be
+Pt (+2/-10.5) 20% bounded with +Point CTS, and BC 100%
F/L in all 4 SGs PWSCC/ODSCC MBM with +Pt 100% MBM with N/A 100% BC/+Pt base scope ding/dent dents or dings within 1 inch in all 4 SGs PWSCC/ODSCC AVBs with dents +Pt 100% AVBs with N/A 100% BC/+Pt base scope dents or dings in all 4 SGs PWSCC/ODSCC U-bend freespan +Pt 100% U-bend N/A 100% BC/+Pt base scope dings region freespan dings in all 4 SGs Cold Leg Thinning Cold Leg TSPs BC 100% FL in all 4 +Pt new indications and those which have SGs chanqed Cracked TSP TSPs BC 100% FL in all 4 +Pt inspection will be required in areas where SGs adiacent tubes have cracked TSP
-5
- 5. For each area examined (e.g., tube supports, dent/dings, sleeves, etc), provide a summary of the number of indications identified to-date for each degradation mode (e.g., number of circumferential primary water stress corrosion cracking indications at the expansion transition). For the most significant indications in each area, provide an estimate of the severity of the indication (e.g., provide the voltage, depth, and length of the indication). In particular, address whether tube integrity (structural and accident induced leakage integrity) was maintained during the previous operating cycle. In addition, discuss whether any location exhibited a degradation mode that had not previously been observed at this location at this unit (e.g.,
observed circumferential primary water stress corrosion cracking at the expansion transition for the first time at this unit).
The Steam Generator inspection activities are presently 80% complete SQN Unit 2 RFO 16 S'rEAM GENERATOR EDDY CURRENT TESTING 11/101200964353 AM STEAM GENERATOR 1 2 3 4 TOTAL DEGRADAnON ACTUAL ASSESSMENT TUBES TUBES TUBES TUBES TOBE TUBE REPAIR DAMAGE MECHANISMS NDICATIONS 10 PLUG 1li0ICATIONS TO PLUG INDICATIONS TO PLUG INGtCATIONS TO PLUG PLUGGED PROJECTIONS AV5 \'i:Il,R 14 0 42 0 19 0 17 a 0 2 CC_D LEG -\1iNNING ':SQN2 ONLY; 43 0 73 1 Eo! 2 38 2 5 4
':-REESPA!'II ODSCC 1 1 0 0 0 0 0 a I 5 FqEESPAN p'lisec 0 0 0 0 0 0 0 0 I) 0 LOOSE PA;qrs DAMAGE 0 0 0 0 0 0 0 a 0 0 SLUDGE P,LE CR.~C";,:NG 0 0 1 0 0 0 0 a 0 1 TSC< :'DSCC AXLA.l ("',Rel 657 1 720 3 893 5 1519 10 19 26 131= :::cscc CiR~ ICENTS: 0 0 0 0 0 0 0 0 I) 2 TTS ODSCC 4..\ AL. 0 0 0 0 1 1 2 2 3 6 TTS ODS:::C C~RC 0 0 1 1 1 1 3 3 5 26
- ..:~8END OD3C: AX!A'-. 0 0 0 0 0 0 0 0 0 0
...-*SEND oosec eIRe 0 0 0 0 0 0 0 0 0 0 T3;: P'/YSCC A.X,t,L 0 0 0 0 0 0 0 0 0 1 T.3= ;:;-W3-:',C C;::j:C~OEtFS'l 0 0 0 0 0 0 0 0 0 0 TT3 p',vscc AXI~L 0 0 0 0 2 1 1 1 2 4 TTS P'oOSCC eIRe; 0 0 0 0 1 1 0 0 I 1 i:I'{\:;,cc .ol..Xi;ol 0 0 0 0 0 1
- ~'.a::ND 0 0 C 0
- ,-'-SEND pwscc
- ::>RC 0 0 0 0 1 1 0 C I 4 PR;-HEATER '1iEAP. :\,\16~1 O"lL V:l 0 0 0 0 0 0 0 0 0 C CfTHERfiPREVEl\T!VE a 0 0 0 1 0 6 4 4 14 TOTALS INO/PLUG (Current) 715 2 837 5 970 12 1586 .2.2 41 97
- ~ ~
Totul Previously Plugged . 92 >' .....* > 197 162 153 604 PLUG TOTAlS 94 202
. 174 175 645 TOTAL SLEEVES (Current) 0 a 0 0 0 Tolal Previously Sleeved 0 0 0 0 0 SLEEVE TOTALS 0 0 0 0 0 TOTAL PERCENT PLUGGED 2.6% 6.0c)~ 5.1% 5.2% 4.8%
EQUIVALENT
-6
- 6. Describe repair/plugging plans.
Mechanical ribbed plugs are the method to be used for plugging. Stabilization will be considered in addition to the plugging.
- 7. Describe in-situ pressure test and tube pull plans and results (as applicable and if available).
In Situ equipment is on site and screening for in situ testing will be performed as degraded tubes are identified.
A preliminary list of candidate indications has been developed based on production voltage screening criteria. A final listing will be developed based on results of sizing analysis and In-Situ Guidelines. No tube pull is planned.
No tube pull is planned.
- 8. Discuss the following regarding loose parts:
- what inspections are performed to detect loose parts 100% bobbin coil in all four SGs and 100% Plus Point hot leg and cold leg top of tubesheet. Secondary side FOSAR of top of tubesheet in all four SGs and steam drum inspections in SGs 2, 3, and 4. SG 1 steam drum inspection was performed last outage.
- a description of any loose parts detected and their location within the SG (including the source or nature of the loose part, if known)
FOSAR is being performed in each steam generator. FOSAR has been completed for SGs 2 and 3.
One piece of flexitalic gasket was identified and removed from SG 3 during FOSAR. The following table is a list of eddy current Possible Loose Part (PLP) indications. PLPs identified during previous outages have been FOSAR inspected with no loose parts remaining in the SGs. FOSAR results indicate PLPs identified by eddy current are often the result of bridging and not loose parts.
-7 Eddy Current SG ROW COL LEG INDIC LOC PREVCYCLE 1 7 88 H PLP HTS+.22 PLP 1 8 88 H PLP HTS+.21 PLP 1 28 20 H PLP HTS+.10 PLP 1 33 37 H PLP HTS+.18 PLP 1 34 37 H PLP HTS+.18 PLP 3 8 3 H PLP HTS+1.61 NDD 3 16 35 C PLP HTS+1.35 PLP 3 30 58 H PLP HTS+.18 PLP 4 7 45 C PLP CTS+.29 NDD 4 12 47 C PLP CTS+.22 NDD 4 24 54 H PLP HTS+.14 NDD 4 24 55 H PLP HTS+.18 NDD 4 26 18 C PLP HTS+3.00 PLP 4 26 18 H PLP HTS+3.28 PLP 4 36 45 H PLP HTS+.28 NDD 4 39 36 H PLP HTS+46.55 PLP 4 39 37 C PLP HTS+46.55 PLP 4 44 41 H PLP HTS+.12 PLP 4 44 42 H PLP HTS+.14 NDD
- if the loose parts were removed from the SG The removal of the flexitalic gasket is complete in SG 3.
- indications of tube damage associated with the loose parts No indication of tube wall loss associated with loose parts has been identified.
- 9. Discuss the scope and results of any secondary side inspection and maintenance activities (e.g., in-bundle visual inspections, feedring inspections, sludge lancing, assessing deposit loading, etc).
SGs 2, 3, and 4 will receive upper internal inspections which includes feedwater tee thickness measurements. All four SGs will be sludge lanced and receive FOSAR. FOSAR includes one in bundle inspection per quadrant plus investigating all new PLPs.
- 10. Discuss any unexpected or unusual results.
Two axial indications have been detected in the cold leg tubesheet region of SG 4. These indications are several inches down into the tubesheet. In accordance with TVA's commitment, all four SG cold leg tubesheets are being 100% inspected.
The two indications of axial ODSCC at tube support plates are larger than the Operational Assessment predicted maximum voltage. The predicted maximum voltage was 4.1 volts.
SG 3 has one 4.17 volt and SG 4 has one 6.55 volt indication. The 6.55 volt indication grew
-8 from 0.36 volts. The Operational Assessment's projected probability of burst, leakage, and quantity of indications bounded the corresponding Condition Monitoring value.
- 11. Provide the schedule for steam generator-related activities during the remainder of the current outage.
All eddy current examinations are expected to be completed by late Thursday followed by plugging. 11/12/09 All secondary side maintenance is expected to be completed by Thursday. 11/12/09
- 1. Which row was the circ indication in the U-bend? Was it associated with a dent? If so, what was the dent voltage? Was it large?
The chart on page 5 titled "Steam Generator Eddy Current Testing" provided for the teleconference on November 10, 2009, was a preliminary list. The circ indication listed in the row of the chart for the damage mechanism "U-bend PWSCC circ" (third from the last row of damage mechanisms) had not been through final analysis review. The indication was reviewed, by our Lead analyst, and characterized as an indication not associated with degradation. This process also includes a comparison to prior cycle inspections for a determination of changes in the eddy current response. With the indication having no change and indicative of geometry, the signal was characterized as not being that of a degraded tube (Le., GEO) and will not be removed from service as a result of this indication.
- 2. What were the reasons for preventively plugging the tubes?
The chart on page 5 titled "Steam Generator Eddy Current Testing," in the row marked "other I preventative" (last row of damage mechanisms) shows that 4 tubes will be plugged. Sequoyah plugged tubes which are repeatedly difficult to inspect (e.g., probe stops rotating), tubes which exhibited characteristics that would result in large voltage growth if allowed to remain in service (indications at tube support plates that are allowed to remain in service in accordance with GL 95-05), and tubes that had permeability variations or other properties which impeded the eddy current evaluation of the tube (often require special probes to inspect, e.g. magnetically biased probes) Also, tubes are being plugged because of secondary side foreign object that can not be removed. Any secondary side foreign objects that are not removed are being evaluated by Westinghouse for the acceptability of remaining in the steam generator.
- 3. Were any indications found in dent/dings? If so, what were the voltages?
SG ROW COL VOLTS INDIC DNT_LOC 1 3 15 2.02 DNT H01-.18 1 28 46 2.52 DNT H06-.08 1 35 19 2.09 DNT H01-.35 2 42 66 2.38 DNT H06+.32 2 42 67 2.84 DNT H06+.38 2 42 67 2.3 DNT H06-.24 3 22 61 2.36 DNT H03+.32
- 4. Did they do a visual inspection of the new PLPs to confirm that no parts were present?
Yes, Sequoyah visually inspects all PLPs identified. FOSAR is given the eddy current PLP's identified prior to their inspection in each steam generator. Any confirmed PLP's are either removed or a disposition is conducted and documented. In one case a loose part was identified that could not be removed and the tubes around those that the loose part is lodged between have been plugged. Most of the PLPs were attributed to bridging or nothing visible.
Attachment 2
-2
- 5. Were rotating probe examinations performed at the locations with the 2 large OOSCC indications at the TSPs during the last outage?
SG3 R9 C5 (4.17 volts - bobbin coil voltage) was examined with a rotating probe the last two outages. Ouring the last outage (U2C 15) the bobbin coil voltage for the indication was 1.2 volts.
Since the distorted support indication (OSI) exceeded 1.0 volts (Le., the TVA criterion for utilizing the rotating probe), the indication was inspected using a rotating probe.
SG4 R23 C54 (6.5 volts - bobbin coil voltage) was not examined with a rotating probe last outage.
The U2C15 OSI (0.36 volts) in this tube did not meet the TVA screening criterion for utilizing the rotating probe.
If so, did they give any indication that these indications may grow faster than other locations?
No, SG3 R9 C5 did not show evidence of the potential for fast growth. The voltage on the rotating probe was 0.39 in Cycle 15 and 0.20 in Cycle 14. SG4 R23 C54 has no previous rotating probe data at the support plate in question.
What corrective actions are being taken to address these indications (e.g., additional rotating probe exams, applying an increasing growth rate factor and preventively plugging, plugging all RPC confirmed indications, etc.)?
These large growth indications have been reviewed in an attempt to provide additional information to prevent large growth. TVA evaluated the rotating pancake coil (RPC) indications and based on the established criteria will plug those RPC indications required to be plugged by the Steam Generator Program. TVA will continue to implement our alternate repair criteria for OOSCC at tube support plates. Evaluation of these indications is ongoing in an effort to garner additional information as to their large growth. The growth at SG4 R23 C54 will be a factor in our evaluation.
A corrective action document has been initiated to evaluate these large growth indications.
December 10, 2009 Mr. Preston D. Swafford Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 3R Lookout Place 1101 Market Street Chattanooga, TI'J 37402-2801 SUB~IECT: SEOUOYAH NUCLEAR PLANT, UNIT 2 - FALL 2009 REFUELING OUTAGE STEAM GENERATOR TUBE INSERVICE II'JSPECTION COI'JFERENCE CALL
SUMMARY
Dear Mr. Swafford:
On November 10 and 18, 2009, the Nuclear Regulatory Commission staff participated in conference calls with Sequoyah Nuclear Plant, Unit 2 (SON) representatives regarding SON's fall 2009 refueling outage steam generator tube inspections. Enclosed is a summary of those conference calls.
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:
Summary of Conference Calls cc w/encl: Distribution via Listserv Distribution:
PUBLIC LPL2-2 R/F RidsNrrDorlLpl2-2 Ridsl'JrrPMSequoyah RidsOgcRp RidsNrrLACSola (Hard Copy)
RidsAcrsAcnw_MailCTR RidsRgn2MailCenter RidsN rrDciCsgb Ridsl'JrrDorlDpr KKarwoski, NRR AJohnson, NRR ADAMS ACCESSION NO .. ML093360644 *b>y memo OFFICE LPL2-2/PM LPL2-2/LA :s,.;t-\,BC PL2-2/BC NAME SLingam CSoia RTaylor* TBoyce DATE 12/07/2009 12/07/2009 11/30/2009 12/10/2009 OFFICIAL RECORD