ML083240811

10/21/2008-Summary of Conference Call with Southern California Edison Representatives, Discussions on San Onofre Unit 3 Steam Generator Tube Inspections

ML083240811
Person / Time
Site:	San Onofre
Issue date:	12/03/2008
From:	Kalyanam N Plant Licensing Branch IV
To:	Ridenoure R T Southern California Edison Co
Kalyanam N, NRR/DLPM, 415-1480
References
TAC MD9460
Download: ML083240811 (21)

Text

UNITED NUCLEAR REGULATORY WASHINGTON, D.C. 20555-0001 December 3, 2008 Mr. Ross T. Ridenoure Senior Vice President and Chief Nuclear Officer Southern California Edison Company San Onofre Nuclear Generating Station P.O. Box 128 San Clemente, CA 92674-0128 SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 3 -

SUMMARY

OF OCTOBER 31,2008, DISCUSSIONS ON STEAM GENERATOR TUBE INSPECTIONS (TAC NO. MD9640)

Dear Mr. Ridenoure:

On October 31, 2008, the U.S. Nuclear Regulatory Commission (NRC) staff participated in a conference call with Southern California Edison (SCE) representatives, R. Coe, A. Matheny, and A. Brough, regarding the 2008 steam generator tube inspections at San Onofre Nuclear Generating Station, Unit 3. A summary of the October 31,2008, conference call is provided in the enclosure; the information supplied by SCE, in support of these discussions (handouts), is provided in an attachment to the enclosure.

The NRC staff did not identify any issues that would warrant preventing the plant from starting up following its 15th refueling outage. If you have any questions, please call me at (301) 415-1480.

Sincerely, N. Kalyanam, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-362

1) Summary of conference call 2) Handouts cc w/encl: Distribution via ListServ

SUMMARY

OF OCTOBER 31, 2008, CONFERENCE CALL WITH SOUTHERN CALIFORNIA EDISON REGARDING THE FALL 2008 STEAM GENERATOR TUBE INSPECTION AT SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 3 DOCKET NO. 50-362 On October 31,2008, the U.S. Nuclear Regulatory Commission (NRC) staff participated in a conference call with Southern California Edison (SCE, the licensee) representatives, R. Coe, A Matheny, and A. Brough, to discuss the ongoing steam generator (SG) tube inspections during their Cycle 15 refueling outage (3C15) at San Onofre Nuclear Generating Station, Unit 3 (SONGS 3). SONGS 3 has two Combustion Engineering Model 3410 SGs, designated SG 88 and SG 89, each with 9,350 tUbes made from mill annealed Alloy 600. The tubes have an outside diameter of 0.75 inches and a nominal wall thickness of 0.048 inches. The tubes are explosively expanded for the full depth of the tubesheet and are supported by carbon steel lattice grids (eggcrates).

The tubes are also supported by carbon steel vertical and diagonal bars in the U-bend section. This was the last scheduled inspection of the Unit 3 SGs, which are scheduled to be replaced in the fall of 2010, after the upcoming Cycle 16 operating cycle. Prior to the conference call, the licensee provided a written response to a set of discussion points from the NRC staff (Agencywide Documents Access and Management System (ADAMS) Accession No. ML08261 0458). The licensee's response, dated October 30,2008, (ADAMS Accession No. ML083240834) is included as an enclosure.

The abbreviations used by the licensee in the enclosure are: ALARA As Low As Reasonably Achievable CA Crack Angle CIRC Circumferential COL Column ECT Eddy Current Testing EFPY Effective Full Power Years Elev Elevation EPRI Electric Power Research Institute FLDA Flaw Length Degraded Area ID Inside Diameter Ind Indication PDA Percent Degraded Area PP Plus Point SAl Single Axial Indication SCA Single Circumferential Indication TSC tubesheet cold TSH tubesheet hot TW Through Wall Additional clarifying information and information not included in the attached document is summarized below. Enclosure 1

-2 In discussing the scope of the inspections, the licensee clarified that a 100 percent inspection of the cold leg top of the tubesheet (TTS) locations was performed during 3C14 (November 2006). The rotating probe inspections conducted at the cold-leg TTS during this refueling outage included all the periphery tubes. The licensee also explained that dents are defined as tube diameter distortions located at a support plate, while dings are defined as tube diameter distortions located in a freespan.

The noise levels in the eddy current data in the 2008 outage are comparable to what has been observed in other Combustion Engineering model SGs that have tubing manufactured by Sawhill Tubular. Other plants that had (or still have) similar SGs are Arkansas Nuclear One, Unit 2, Saint Lucie Plant, Unit 2, and Waterford Steam Electric Station, Unit 3. A visual exam was performed on the secondary side of the SGs using remote video camera equipment.

The inspection stated the entire periphery and the blow down lane. The licensee indicated that the one loose part found in SG 89 near the stay cylinder, on the cold-leg at the TTS was not detected during the +PointŽ exam, but was found visually during the foreign object search and retrieval (FOSAR). The neighboring tubes of this loose part were examined with the +PointŽ probe. Since this loose part could not be removed from the SG, four tubes surrounding this loose part will be plugged. These tubes will not be stabilized since the part is firmly lodged in place, and the SGs will only be operated for one more cycle. The licensee stated that potential loose parts (PLPs) found in the periphery are visually examined during FOSAR. Other PLPs that cannot be dispositioned by a visual exam are dis positioned by a historical eddy current review and by looking for trends and patterns in eddy current PLP signals. The licensee indicated that in SGs where the tubes are arranged in a triangular pattern, a true loose part would typically affect three tubes. The licensee stated that there were no upper steam drum or upper bundle in bundle inspections performed this outage. The licensee stated that flow accelerated corrosion was found in Unit 3 prior to a chemical cleaning performed in the 1990's during 3C9. The extent of corrosion was more severe in Unit 3 than Unit 2. The corrosion was a result of a change in flow patterns on the secondary side of the SG caused by the accumulation of deposits.

Visual inspections in several outages following chemical cleaning indicated no further degradation or changes in the position of the supports.

At the end of the call, the licensee was requested to inform the NRC staff if during the remainder of the inspections there were any unexpected results such as new degradation mechanisms.

SONGS Unit 3 Steam Generator Update with the October ENCLOSURE SONGS Unit 3 Background Two (2) Steam Generators

-Supplied by Combustion Engineering

-Designated SG 88 and 89 -SG88 -8617 tubes in Service (7.9% Plugged) -SG89 -8688 tubes in Service (7.1 % Plugged) -No sleeves are installed in SONGS Unit 3 Recent Exam Outages -' Current Refueling Outage (3C15) -19.6 EFPY Last scheduled inspection prior to replacement October 30, 2008 2 co o o C\I o (I') Q) .0 o Completion as of 1

• Bobbin ECT Inspection

.-Complete * +Point ECT Inspection

-Complete Foreign Object Search (FOSAR) -Complete Both SGs In-Situ Testing -No candidate tubes identified Final Review of Inspection Data and Repair List Preparation In Progress Plugging -To begin 10/31/2008 Note: Since exams are still in progress, all data and numbers in this presentation should be considered preliminary and subject to change. October 30, 2008 4 Discussion Points DP-1) Discuss any trends in the amount of primary-to-secondary leakage observed during the recently completed cycle. -SONGS Unit 3 has some reported extremely low-level secondary leakage. Discoverv was June 2,2006, and it has remained stable at approximately 2x1 gallons per day. Similar leakage was noted for SONGS Unit 2 starting on July 25, 2007. This leakage is well below the threshold of detection of normal monitoring instrumentation (the condenser air ejector radiation monitor at approximately 0.1 gallons/day, a capability that is typical in the industry).

This leakage was detected in the SONGS program for monitoring radioactive effluent paths of release to the environment which provides periodic monitoring (collection and measuring activity in a continuous charcoal filter sample on a weekly basis). This leakage detection is not typical in the industry because the SONGS condenser air ejector is a direct release path to the environment and is not diluted by other discharge streams. MonItoring will resume following SON GS Unit 3 restart. October 30,2008 5 Discussion Points DP-2) Discuss whether any secondary side pressure tests were performed during the outage and the associated results. -No secondary side pressure tests were performed.

DP-3) Discuss any exceptions taken to the industry guidelines.

-No exceptions to the industry guidelines were taken October 30, 2008 6 Discussion Points DP-4) Description of Inspections Performed Bobbin Exam or Rotating Exams (+Point) -Full Length Exam of In-Service Tubes (100%) Rotating Exams (+Point) -Hot Leg top-of-tubesheet locations (100%)

-Cold Leg top-of-tubesheet locations (28%)

-Rows 1-3 U-Bend Locations (100%-Rows 4-10 U-Bend Locations -Special I nterest Locations

-3600

-Non-quantifiable bobbin indications (I-Codes)

-139 locations

-Dents > 2 volts (100%) -744 locations

-Dings > 4 volts (100%) -937 locations

-Tube wear at supports (100%) -1770 locations October 30, 2008 7 DP-5) Inspection SG88 SG89 TSH eire, Axial 8 TSC Cire, Axial 0 Freespan Axial 0 Tube Support Axial 0 Tube Support Wear TW) 0 Tube Support Wear (Preventative) 4 Foreign Object (Preventative) 4 Misc. 0 Total Repairable Tubes 16 October 30, 2008 8 DP-5) Inspection Results (Last Previous Outage for Comparison SG88 SG89 TSH Circ, Axial 5 2 TSC Circ, Axial 0 0 Freespan Axial 0 0 Tube Support Axial 0 0 Tube Support Wear (2:44% TW) 0 0 Tube Support Wear (Preventative) 23 8 Tubes with Data Quality/ ALARA Complications 1 1 Total Repairable Tubes 29 11 October 30, 2008 9 DP-5) Top Indications by SG 88 Top 2 Indicsllons by Voltage pp Row Col Volts Ind Origin Elev Inch Length Depth PDA FLDA C A Leak Test Pressure Test 2 40 0.77 SAl 10 TSH -3.87 0.28 61 55.57 No No 38 112 0.71 SAl ID TSH -1.31 0.77 51 43.48 No No 22 34 0.69 SCI 10 TSH -0.11 68 3.48 26 No No 8 42 0.58 SCI lD TSH -2.84 54 2.71 _ ..

26 No No SG 89 Top 2 Indications by Voltage pp Row Col Volts lnd Origin Elev Inch Length Depth PDA FLDA C A Leak Test Pressure Test 10'\ 69 0.93 SCI 10 TSH -0. i 1 70 5.19 51 No No 113 99 0.78 SAl ID TSH -7.78 0.17 54 45.35 No No 103 69 0.69 SCI ID TSH -0.09 53 2.58 26 No No 103 69 0.68 SCI 10 TSH -0.07 53 4.25 30 No No October 30, 2008 10 .

Discussion Points DP-6) Repair/Plugging Plans

• Repair -All indications exceeding Technical Specification repair criteria (>440/0 through wall) -All crack-like Indications

-Quantified (Percent)

Wear Indications

• >25% At tube support locations Diagonal Bar Hot and Diagonal Bar Cold * >300;0 At all other support locations

-Circumferentially oriented indications will be October 30,2008 11 Discussion Points DP-7) In-situ Pressure Test and Tube Pull Plans Utilizing latest EPRI guidelines for candidate selection and testing All tubes meeting criteria will be tested No tubes have been selected to date this outage based on EPRI screening criteria No tube pulls are planned based on inspection results October 30, 2008 12 Discussion Points DP-8) Discuss Foreign Objects What Inspections are performed to detect foreign objects? -Secondary Side Visual Exam (FOSAR) -1 00% By Bobbin Probe or rotating +Point -1 000/0 TSH with rotating +Point -100% TSC periphery with rotating +Point -20% TSC of remaining tubes with rotating +Point A description of any foreign objects detected and their location within the SG -Found one foreign object on the top-of-tubesheet in the SG89 cold leg stay cylinder region. Appears to be approximately 1.25 inch diameter round washer between 2 tubes. October 30, 2008 13 Discussion Points (DP) DP-8) Discuss Foreign Objects

• If the loose parts were removed from the SG -No, removal efforts were unsuccessful.

Part is firmly rodged. Neighboring tubes will be removed from service. Indications of the tube damage associated with the foreign Source or nature of the loose parts, if known -Unknown October 30, 2008 14 Discussion Points (DP) DP-9) Secondary side inspection and maintenance activities

-Visual inspection for foreign objects (Both SGs) -No sludge lancing this outage -No other secondary side maintenance activities October 30, 2008 15 Discussion Points (DP) DP-10) New Inspection Findings -During the 3C15 inspection, no damage mechanisms that were new to SONGS-3 were detected -All mechanisms were previously detected and included in the degradation assessment and the operational assessment. -A planned eddy current follow-up on industry experience (diagonal bar tube support degradation) was successfully complete in both Unit 3 SGs. The diagonal bars that cross the stay cylinder region have been verified in 3C14 (2006) and 3C15 (2008), by bobbin probe eddy current, to be in their normal October 30, k:Meations.

16 Discussion Points DP-11) Schedule for SG Related Activities.

during Remainder of Current Outage

• 10/30/08:

Complete Eddy Current

• 10/31/08:

Complete In-Situ Testing, If Any

• 11/02/08:

Complete Repairs October 30,2008 17 December 3, 2008 Mr. Ross T. Ridenoure Senior Vice President and Chie'f Nuclear Officer Southern California Edison Company San Onofre Nuclear Generating Station P.O. Box 128 San Clemente, CA 92674-0128 SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 3 -

SUMMARY

OF OCTOBER 31,2008, DISCUSSIONS ON STEAM GENERATOR TUBE INSPECTIONS (TAC NO. MD9640)

Dear Mr. Ridenoure:

On October 31,2008, the U.S. Nuclear Regulatory Commission (NRC) staff participated in a conference call with Southern California Edison (SCE) representatives, R. Coe, A. Matheny, and A. Brough, regarding the 2008 steam generator tube inspections at San Onofre Nuclear Generating Station, Unit 3. A summary of the October 31,2008, conference call is provided in the enclosure; the information supplied by SCE, in support of these discussions (handouts), is provided in an attachment to the enclosure.

The NRC staff did not identify any issues that would warrant preventing the plant from starting up following its 15th refueling outage. If you have any questions, please call me at (301) 415-1480.

Sincerely, IRA! N. Kalyanam, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-362

Enclosure:

1) Summary of conference call 2) Handouts cc w/encl: Distribution via ListServ DISTRIBUTION:

PUBLIC LPLIV Reading RidsAcrsAcnw_MailCTR RidsNrrDorlLpl4 RidsN rrLAG Lappert RidsNrrPMSanOnofre RidsOgcRp RidsRgn4MailCenter KKarwoski, NRR/DCI/CSGB AJohnson, NRRIDCI/CSGB ADAMS Accession Nos. ML083240811, AHiser " DCI/CDSB/BC*

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