ML20140E596

Forwards Rept Re ISI of Steam Generator Tubes for Songs,Unit 3,refueling Outage 9

ML20140E596
Person / Time
Site:	San Onofre
Issue date:	06/06/1997
From:	Nunn D SOUTHERN CALIFORNIA EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9706120153
Download: ML20140E596 (9)

Text

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souintRN CAufORNIA 5

EDISON

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t-Vice President l

Ao Eb! SON INTERNATIONAL Company l

June 6,1997 i

l U. S. Nuclear Regulatory Commission l

Document Control Desk Washington, D.C. 20555 Gentlemen:

Subject:

Docket No. 50-362 i-Special Report: Inservice Inspection of Steam Generator Tubes San Onofre Nuclear Generating Station, Unit 3 l

On May 22,1997, Edison completed an inservice inspection of steam generator tubes at San l

Onofre Nuclear Generating Station, Unit 3. Section 5.7.2.c of the Unit 3 Technical Specifications (TS) requires the number of tubes plugged in each steam generator to be reported to the NRC. The enclosed report provides the number of tubes plugged, and the results of tube inspections.

Edison conducted full length eddy current inspection of 18,055 tubes (100% of in-service tubes in both steam generators); 99 tubes were mechanically plugged due to tube degradation. The extent of this inspection significantly exceeded the requirements of TS l

Section 5.5.2.11, " Steam Generator Tube Surveillance Program."

As required by TS Section 5.7.2.c, complete Unit 3 inspection results will be submitted to the NRC by May 22,1998.

l If you require any additional information, please so advise.

Sincerely, k

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k

Enclosure:

i A. T. Howell, Ill, Director, Division of Reactor Safety, NRC Region IV f$'d

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cc:

E. W. Merschoff, Regional Administrator, NRC Region IV K. E. Perkins, Jr., Director, Walnut Creek Field Office, NRC Region IV i

J. A. Sloan, NRC Senior Resident, San Onofre Units 1,2 & 3 M. B. Fields, NRC Project Manager, San Onofre Units 2 and 3 Institute of Nuclear Power Operations (INPO) 9706120153 970606 (lllllllllalllcll.lll-PDR ADOCK 05000362y G

PDR c,

P. O. Bex 128 San Clemente. CA 92614-0128 714 368-1480 fas 714-368-1490

ESPEdlAL REPORT -INSERVICE INSPECTION OF STEAM GENERATOR San Onofre Nuclear Generating Station, Unit 3, Refueling Outage 9 7

Inspection Proaram Planned inspection Scope Table 1 summarizes the planned inspection program, in addition, the inspection program included:

a)

Eddy current profilometry at the top of the tubesheet of all tubes adjacent to " tie rods" and v;sual inspection of all installed tube plugs.

b)

Inspection in both steam generators to include U-bend region of all tubes in Rows 1,2 and 3 with a Plus-Point Probe.

Inspection Scope Expansion a)

All hot leg eggerate intersections that were identified by bobbin probe to have a quantifiable indication, were examined with the Plus-Point Probe to verify that the degradation mechanism was volumetric mechanical wear.

b)

Tubes that were selected for plugging due to tube-to-support wear were examined with the Plus-Point Probe to verify that the degradation mechanism was volumetric mechanical wear, c)

Some dented tube support intersections were examined with an eddy current profilometry probe to confirm and improve Edison's understanding of the size and shape profile of these intersections.

Results Notable tubing degradation identified included the following:

a)

Tube wear at eggcrate supports and at vertical strap supports. [ Edison provided a complete discussion of eggcrate issues by letter dated June 5,1997.]

b)

Circumferential and axial cracking were identified in the tight radius bend regions of tubes in Rows 1 and 2. Note that this resulted in inspection with Plus-Point Probe of the U-bend region in all tubes in Rows 1 through 3.

Plugged due to Tube Degradation Table 2 illustrates the number of tubes plugged in each steam generator due to tube degradation. Each tube is only accounted for once in this listing, although it may have an Gddy current indication of a type below the point in the listing where it appears.

=-

In-Situ Hydrostatic Testing of Tubing Table 3 provides a summary of in-situ hydrostatic testing of tubing.

Investiaations into Causes and Corrective Measures An accumulation of corrosion products on secondary-side of the tubing surfaces had been previously identified. Data from various sources indicated that such deposits might contribute to tubing corrosion. Consequently, Edison convened a panel of expert industry personnel with extensive knowledge in steam generator corrosion and water chemistry control. The panel reviewed the pertinent information and recommended that Edison chemically clean the deposits from the steam generator tubes. The deposits were removed during this refueling outage.

FIGURE 1 -Steam Generator internal Location Reference Guide CE MODEL 3410 TUBE SUPPORT DRAWING VH2 VSM VC2 l

VH1 VH3 VC3 VC1 1

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INLET

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. FIGURE 1 cont'd CLARIFICATION OF TUBING / SUPPORT INTERFACES AB0VE THE 7TH FULL EGGCRATE SUPPORT R0WIS)

TUBING / SUPPORT INTERFACE.S.

120-147- 08H.09H.10H.DBH.VHl.VH2.VH3.VSM.VC3.VC2 VC1.DBC.10C.09C.08C 115-119 08H.09H DBH.VH1.VH2.VH3.VSM.VC3.VC2.VC1.DBC 09C.08C 84-114 08H.09H DBH VH2.VH3.VSM.VC3.VC2 DBC 09C.08C 83 08H DSH VH2.VH3.VSM.VC3.VC2 DBC 08C 51-82 08H DBH VH3 VSM.VC3.

DBC 08C 49-50 08H DBH VSM DBC 08C 19-48 DBH VSM DBC -

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COMBUSTION ENGINEERING MODEL 3410 STEAM GENERATOR TUBESHEET MAP i

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TOTAL TUBES

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~ TABLE 1 - Summary of Planned Inspection Program Steam Generator E-088 Stearn Generator E-089 Number of Tubes / Percentage of Tubes Full length of tube with the Bobbin Probe 9024/100 %

9031 /100 %

Tight radius U-bend regions with the 25/20%

23/20%

Plus-Point Probe (Rows 1 & 2)

Hot leg expansiori transition at the top-of-tubesheet with the 9024 /100 %

9031 /100 %

Plus-Point Probe Cold leg expansion transition at the

' top-of-tubesheet 684 /7 %

676 /7 %

l with the Plus-Point Probe Hot leg dents with l

the Plus-Point Probe 3/20%

5/20%

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TABLE 2 - Plugged due to Tube Degradation Indication Orientation / Location Steam Generator E-088 E-089 Axial indications below the inlet top-of-tubesheet 2

3 Both circumferential and axial oriented indications that do not intersect and are near the expansion transition at the hot leg top-1 0

of-tubesheet Circumferentially oriented indications near the expansion transition at the hot leg top-of-tubesheet 9

11 Circumferential indications in a tight radius U-bend (Rows 1 and 2) 2 0

Axially oriented indications in the lower bundle (typically below elevation 07H), and not associated with a tube support (freespan) 3 0

Axially oriented indications at a hot leg eggerate tube support location 1

0 Plugged due to lack of explosive expansion of the tubing within the hole drilled in the tubesheet 3

4 Axially oriented indications near the expansion transition at the hot leg top-of-tubesheet 1

0 Preventive plugging of tubes adjacent to a tie rod 3

0 Wear at an eggerete support (Exceeding Plugging Limits) 2 5

i Wear at an eggerate support (Preventive Plugging) 13 4

Wear at a vertical strap support (Preventive Plugging) 14 8

Volumetric indication at a miscellaneous location in a tube 3

3 Circumferential indications in a tight radius U-bend (Row 1) 0 2

Axial indication in a tight radius U-bend (Rows 1 and 2) 0 2

Total 57 42 l

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• i TABLE 3 - Summary of In-Situ Hydrostatic Testing of Tubing

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STEAM GENERATOR E-088 Region Row-Col Complete Leakrate Location Comments / Test Extent Eggerate 113-73 Yes None 09H Full Tube Axial l

U-Bend 1-47 Yes None Full Tube Circumferential 2 No Full Tube Freespan 29-33 Yes None 02H+4" Full Tube Axial 60-122 Yes None 02H+10" &11" FullTube 54-144 No 02H+12" Full Tube Freespan 45-129 Yes None 07H+24" Full Tube Volumetric 49-47 Yes None DBH +2.3" Full Tube Preservice 48-158 No 07C+5"&9" Full Tube Tubesheet 40-124 Yes None Hot Leg Local Circumferential I

STEAM GENERATOR E-089 l

l Region Row-Col Complete Leakrate Location Comments / Test Extent 1

U-Bend 1-121 No Full Tube Circumferential 1-135 No Full Tube U-Bend 1-17 No Full Tube Axial 2-10 No Full Tube l

Freespan 31-173 No 02H+32" Local Volumetric Tubesheet 30-42 No Hot Leg Local Circumferential 31-129 No Hot Leg Local Tubesheet 1-1 No Hot Leg Full Tube Volornetric 138-7,0 No Cold Leg + 3

Local l

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