ML20203G610
| ML20203G610 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 02/20/1998 |
| From: | Gibson G SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9803030024 | |
| Download: ML20203G610 (6) | |
Text
.
, pts som,omou,ust d EDISON An/W B OV h TfR%4FIO bit N,pa, February 20,1998 U S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Gentlemen:
Subject:
Docket No. 50 30, Special Report: Inspection of Steam Generator Tubes San Onofre Nuclear Generating Station, Unit 2 -
Reference:
Letter from J. L. Rainederry (SCE) to Document Control Desk (USNRC),
" Steam Ge'1erator Run Time Analysis For Cycle 9, San Onofre Nuclear Generatin 13tation Unit 2", Docket Number 50-361, September 26,1997 On February 15,1998,-Southern Califorr, Edison (SCE) completed an inspectiori of steam generator tubes at San Onofre Nuclear Generating Station, Unit 2. Technical Specification 5.7.2 lequires SCE to submit the following Specia! Reports:
1.-
Within 15 days, the number of tubes plugged or sleeved in each SG. The number of tubes plugged is provided in Table 3 of the enclosed Special Report. No tubes were
- sleeved.
2.
Prior to resumption of plant operation, the results of SG tube inspections which fall into Categor) C-3 (defined in TS 5.5.2.11.c). This information is provided in the enclosed
- Special Report.
3.
Within 12 months, the complete results of the SG tube inservice inspection. This b,
-information wit; be provided prior to February 15,1999.
/J The initial assessment of the inspection results indicates that operation until the next refueling.
outage is appropriate. SCE will submit a final assessment of the enclosed inspection results within 90 days of the end of the Unit 2 Cycle 9 mid-cycle outage to update the previous run time analysis provided in the referenced letter.
9903030024 900220 PDR ADOCK 05000361 G
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55m Clemente. CA 926744128
._ = ___ _ ______
Document Control Desk 2-February 20,1998 If you require any additio,)alinformation, please so advise.
Sincerely.
G. T. Gibson Manager, Compliance Enclosure cc:
E. W. Merschoff, Regional Administrator, NRC Region IV K. E. Perkins, Jr., Director, Walnut Creek Field Office, NRC Region IV M. B. Fields, NRC Project Manager, San Onofre Units 2 & 3 J. A. Sloan, NRC Senior Resident, San Onofre Units 1,2 & 3 Institute of Nuclear Power Operations (INPO)
SPECIAL REPORT -INSERVICE INSPECTION OF STEAM GENERATOR TUBES ID8R#rJlon Progr.Am Planned Inspection Scope Table 1 summarizes the planned inspection program. In addition, the inspection program included inspection with the Plus-Point Probe of indications by the bobbin probe that were non-quantifiable or distorted.
Inspection Scope Expansion Table 2 summarizes significant inspection program scope expansion in response to inspection results. In addition:
a) all hot leg and cold leg eggcrate intersections that were identified by bobbin probe to have a quantifiable indication were examined with the 'ns-Point Probe to verify that the degradation mechanism was volumetric riiechanical wear. A 20% sample of the diagonal brace and vertical strap intersactions with quantifiable indications identified by bobbin probe were also examined with the Plus-Point Probe.
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.
Results inspection results indicate axial cracking at the intersections of tubing and eggcrate supports on the inlet (hot leg) side of the steam generator. TV cracking was observed at intersections experiencing denting, and at intersections witt onclusive indications of denting. (Denting is the plastic deformation of tubes resulting..am the growth / buildup of corrosion products [ magnetite) in the tube-to-tube support structure annuli.) Also, axial cracking was identified in areas between supports (commonly called "freespan") on the hot leg side of the steam generators.
In accordance with " DRAFT" Regulatory Guide 1.121 (Bases for Plugging Degraded PWR Steam Generator Tubes), Condition Monitoring and Operational Assessments of these indications will be conducted using " DRAFT" Regulatory Guide DG-1074, " Steam Generator Tube Integrity", September 5,1997. T he initial assessment of eddy current testing and in-situ pressure testing results indicate that operation for the remainder of this fuel cycle is appropriate. _ _ _ _ _ _ _ _ _ _ _
Removal of Tubes from Service (by Plugging)
Table 3 lists the number of tubes removed from service in each steam generator. Each tube is only counted once in this listing, although it may also have an eddy current indication of a type below the point in the listing where it appears.
In Situ Hydrostatic Testing of Tubing Table 4 provides a summary of in-situ hydrostatic testing of tubing.
I Causes And Corrective Actions No new damage mechanisms were detected during this mid-cycle examination. Portions of tubes were removed for laboratory examination to confirm damage mechanism morpho;ogy curing the 1997 refueling outage. The previously identified damage mechanisms are still present and considered active.
Actions have been taken to improve the secondary side chemistry environment for steam generator tubing. These actions have been reviewed by a panel of industry experts for application at SONGS The expert panel concurs with these measures. The actions include:
1.
Chemical cleaning of the entire tube bundle (full bundle) performed during the last refueling outage.
2.
Addition of an inhibitor (titanium dioxide) for IGA / SCC immediately after the chemical cleaning for maximum crevice penetration potential.
3.
Use of Ethanolamine (ETA) for pH control of the secondary fluids, and, 4.
Boric acid addition in the secondary side to help reduce denting of the tube supports and stress corrosion cracking of tubing.
In addition, SCE has initiated a plan to reduce the reactor coolant temperature at the steam generator inlet (T-hot) by about 13' F. SCE expects this will reduce stress corrosion cracking of the tubing initiating from the inside diameter of the tubing. The first phase of this plan, a reduction of about 4' F, was completed in January 1998.
2-
TABLE 1 - Summary of Planned Inspection Program Number of Tubes / Percentage of Tubes Steam Generator E 048 E 048 Full length of tube with the bobbin probe with the 8873/100%
8804 /100%
exception of the U bend region of Row 1 and 2 tub 9s where a more sensitive Pius Point Probe was use[
Tight radius U bend regions Row 1 and 2 with the 122/100%
128/100%
Plus-Point Probe Plus-Point Probe examination of all hot leg dented 1488 /100 %
1123/100%
eggcrate supports and dings 25 volts TABLE 2 - Summary of Significant Scope Expansion Number of Tubes / Percentage of Tubes Steam Generator E 048 E 048 Tight radius U-bend regions of Row 3 with the P.lus-Point Probe 66/100 %
63/100%
TABLE 3 - Number of Tubes Removed From Service Steam Generator Indication Orientation / Location E-o88 E-o89 Tubes with axially oriented ID indications at tube support locations 5
7 Tubes with axially oriented OD indications at tube support locations 32 24 Tubes with axially oriented OD indications not associated with a tube support (frecspan) 99 67 Tubes with r.xially oriented OD indications in the sludge pile region near the top-of-tubcsheet 2
2 Tubes with axially oriented indications below the inlet top-of-tubcsheet 0
3 Tubes with indications of wear at tube support locations 16 4
Tubes with circumferentially oriented indications at tight radius u-bend locr.tions 0
1 Tubes with pumetric indications at miscellaneous locations 3
1 Miscella..
- .eventative plugging 2
3 Td.il 159 112 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
l TABLE 4 - Summary of in-Situ Hydrostatic Testing of Tubing STEAM GENERATOR E-u.'l -
Region Tube number Loc.
GPM GPM GPM Maximum Test Row column Leakage Leakage Leakage Press at at MSLB at NOPD Post-MSL Eggerate OD 16-16 05H 0
0 0
4593 86-24 06H 0
0 0
4C93 135 79 06H 0
0 0
4593 E0gerate ID 27-111 Full Tube 0
0 0
4593 30 116 Full Tube 0
0 0
4593 16 120 Full Tube 0
0 0
4593 STEAM GENERATOR E-089 Region Tube number Loc.
GPM GPM GPM Maximum Test Row-column Leakage Leakage Leakage Press at at MSLB at NOPD Post MSL Eggerate OD 98-40 06H 0
0 0
4593 Egge. rate ID 71 17 04H 0
0 0
4593 91 25 04H 0
0 0
4593 91 37 07H 0
0 0
4593 104-40 05H 0
0 0
4593 57 107 07H 0
0 0
4593 U-Bend 2 172 Full Tube 0
0 0
4593
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Notes:
GPM = Gallons per Minute NOPD = Normal Operation Pressure Differential MSLB = Main Steam Line Break Pressure Differential N/A = Not Applicable OD = Degradation initiated on the outside diameter of the tubing ID = Degradation initiated on the inside diameter of the tubing The Test pressure that correlates to 3 times NOPD is 4593 psi for axial flaws. l
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