ML20216B894
| ML20216B894 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 03/10/1998 |
| From: | Rainsberry J SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9803130214 | |
| Download: ML20216B894 (9) | |
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EDISON Manager. Plant Licensing An W! SON INTLRNA HOML" Company March 10, 1998 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C.
20555 Gentlemen:
Subject:
Docket Nos. 50-361 and 50-362 Steam Generator Secondary Side Inspection (SSI)
San Onofre Nuclear Generating Station Unit 2 During the recent mid-cycle outage at San Onofre Nuclear Generating Station Unit 2, a visual inspection was performed on the secondary side of the steam generators.
This inspection was performed as a result of the degradation observed in the secondary side of the Unit 3 steam generators during the last refueling outage. A copy of the Engineering Guide for Steam Generator SSI prepared for this inspection is provided as Enclosure 1.
Although no flow accelerated corrosion degradation was noted during the limited visual inspection conducted after chemical cleaning during the last Unit 2 refueling
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outage, based on the degradation observed during the Unit 3 refueling outage,
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a survey of 20% (about 50 tubes) of the tubes on the hot leg periphery was
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concluded to be appropriate.
The actual inspections performed during the mid-cycle exceeded the scope in the inspection guide. The scope was to inspect 10 locations on the hot leg periphery of each steam generator.
In actuality,17 locations (75 tubes) were inspected in steam generator 88, and 18 locations (90 tubes) were inspected in steam generator 89.
In general, the secondary side was concluded to be in good to excellent condition. Minor isolated instances of thinning were
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observed, as expected, but overall the thinning was an order of magnitude less than that observed on Unit 3.
No repairs were required.
The tables in provide the results of the inspection using the grading criteria in the inspection guide. The observed minor areas of (eggcrate lattice bar)
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thinning do not affect the ability of the tubes or the supports to meet their design basis.
Further, the results of these inspections, in combination with the differences in steam generator cleaning results from the last outages, support the root cause results of the observed Unit 3 problem.
9803130214 9G0310
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PDR ADOCK 05000361 O
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- Vd San Onofre Nuclear Generating Station P. O. Box 128 San Clemente, CA 92674 0128 714-3647420
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Document Control Desk
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Inspections of the secondary side of the Unit 2 steam generators will continue to be performed during future refueling outages until it is established that further inspections are not required.
If you have any questions or would like further information on the inspections, please let us know.
Very tru'.y yours, J. L. Rainsberry Enclosures cc:
E. W. Merschoff, Regional Administrator, NRC Region IV K. E. Perkins, Jr., Director, Walnut Creek Field Office, NRC Region IV J. A. Sloan, NRC Senior Resident Inspector, San Onofre Units 2 & 3 M. B. Fields, NRC Project Manager, San Onofre Units 2 and 3 1
0 t
O 9
e ENCLOSUREI ENGINEERING GUIDE FOR STEAM GENERATOR SSI i
NUCLEAR ORGANIZATION WORK PROCEDURE S023-XXVI-14.801 NUCLEAR CONSTRUCTION REVISION O PAGE 22 0F 26 UNITS 2 AND 3 ATTACHMENT 6 ENGINEERING GUIDE FOR STEAM GENERATOR SSI
- 1. SCOPE A video survey of 40 to 50 tubes on the hot leg periphery (about 20%) will be conducted during the mid-cycle outage. The scope and location establish the general condit'47 of the vertical strips and batwing supports.
- 2. AREAS TO BE INSPECTED The inspection will characterize the general condition of the eggerate tube supports and utilize grading criteria. The acceptability of the batwings' and vertical strips' condition should also be confirmed by inspecting in four or five areas. Special areas of attention during the inspection will be where the partial eggerate tube support plates are attached to the ring support.
Twelve to fifteen camera drops are planned on the hot leg. This assumes that the surrounding 4 tubes at any drop location can be observed. The tubes will be examined from the 3rd to the 10th eggcrate regions. See Table 1. Target tubes have been selected as a guide, and do not specifically have to be viewed.
i ATTACHMENT 6 PAGE 1 0F 4
NUCLEAR ORGANIZATION WORK PROCEDURE S023-XXVI-14.801 NUCLEA.R CONSTRUCTION REVISION O PAGE 23 0F 26
' UNITS 2 AN9 3 ATTACHMENT 6 Table 1 - Inspections Zones ZONE TARGET TUBE NOTES (see figure 1) 1 49-7 view of 8th partial Eggcrate 2
83-17 view of 9th partial Eggcrate 3
98-24 4
112-32 5
124-42 view of 10th partial Eggcrate 6
133-53 7
145-75 8
146-86 Row 147, near apex 9
145-97 10 137-119 11 128-130 12 56-168 view of 8th partial Eggcrate 13 38-172 Tube Maps will be developed on these inspection areas for use in the evaluation analysis.
- 3. EVALUATION The results of the inspection will be mapped and assessed in accordance with Reference 2. Grade is assigned to each lattice bar as follows:
A = greater than 50% of nominal thickness remaining B = 10 to 50% of nominal thickness remaining C = less than 10% of nominal thickness remaining D = severed lattice bar X = unable to determine Should the assessment of the lattice bars indicate a scope expansion is necessary, an AR/NCR will be generated if appropr.iate, per existing site procedures.
ATTACHMENT 6 PAGE 2 0F 4
MUCLEAR ORGANIZATION WORK PROCEDURE S023-XXVI-14.801 HUCLEAft CONSTRUCTION REVISION O PAGE 24 0F 26 UNITS 2 AND 3 ATTACHMENT 6
- 4. SCOPE EXPANSION If no grade Cs or Ds are reported, the inspection will be documented and terminated. If degradation is found, the scope will likely be increased. Scope expansion would depend on the number of grade C or D calls.
Table 2 ScopeExpansionh EGGCRATE GRADES ACTION REQUIRED 1
ALL A's or B's No further inspection required 2
Isolated C's, No further inspection required -
Notify STS 3
Many C's, (more than 20%)
Increase inspection to 40% (See note 1) 4 Some grade D's, random Increase inspection to 40%
5 Consecutive C's consecutive Increase hot leg inspection to 100%
eggerate tube supports, vertical 6
Some grade D's, consecutive Increase hot leg inspection to 100%
eggcrate tube supports Inspect cold leg region near blowdown lane, minimum 4 drops.
7 Many grade D's, consecutive
- 1. Increase hot leg inspection by eggcrate tube supports 100%, include stay cylinder region.
- 2. Inspect cold leg region near blowdown lane, minimum 4 drops.
Table 2 Notes; 1.
An inspection increase means including an adjacent inspectica zone to those developed in Table 1. If 13 drops were conducted originally, then 13 additional drops should be conducted. The new inspection zones are adjacent to the original zones, generally mcving towards the apex, if possible. Otherwise, use the adjacent zone toward the blowdown lane.
2.
If the scope expansion to 40% fails to bound the area of eggerate thinning, then the scope becomes 100% with cold leg and stay cylinder inspections as indicated.
ATTACHMENT 6 PAGE 3 0F 4 l
NUCLEAR ORGANIZATION WORK PROCEDURE S023-XXVI-14.801 NUCLEAR CONSTRUCTION REVISION O PAGE 25 0F 26
' UNITS 2 AND 3 ATTACHMENT 6
- 5. TUBE PLUG CRITERIA Should an evaluation be required, it will be documented using the site AR process.
Generally, for each tube that has more than one (1) consecutive eggerate support considered uncredited, the tube will be plugged and stabilized.
PLUGGING EVALUATION AND PROCESS A) For a given eggerate evaluation, grade each lattice bar surrounding a given tube.
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- 1. If two or more lattice bars cannot be crecited (C or D) then the eggerate at that elevation may not be credited.
- 2. If three (3) or more lattice bars can be credited (A or B) then the eggerate location can be credited.
B) The grading of lattice bars for each tube at each eggcrate elevation will be repeated until completed.
C) Assess each tube for uncredited eggcrate tube supports. Tubes with two or more consecutive eggerate tube supports uncredited must be plugged End i
stabilized.
1 A plugging list will be generated, and the list will be independently verified by the same process.
ATTACHMENT 6 PAGE 4 0F 4
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ENCLOSURE 2 RESULTS OF STEAM GENERATOR SSI SAN ONOFRE UNIT 2 MIDCYCLE 9 4
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SAN ONOFRE NUCLEAR GENERATING STATION UNIT 2 S/G 88 HOT LEG UNIT 2 S/G 89 HOT LEG MIDCYCLE 9 MIDCYCLE 9 Total Drops Completed:
17 Total Drops Compiowd:
33 Total Tubes:
75 Total Tubes:
90 Egg Crate -
Egg Crate Number Grade A Grade B Grade C Grade D Number Grade A Grade B Grade C Grade D 10H 100.0 %
10H 97.2%
2.8%
9H 95.4 %
3.8%
0.8%
9H 86.6%
11.0%
2.3%
8H 96.0 %
4.0%
8H 92.3%
7.7%
7H 94.1 %
5.9%
7H 95.4 %
4.6%
6H 100.0%
SH 100.0 %
l 5H 99.5 %
0.5%
SH 99.2 %
0.4%
0.4%
4H 100.0 %
4H 100.0 %
3H
.100.0 %
3H 100.0 %
2H 100.0 %
2H 100.0 %
l Overall:
98.2%
1.7%
0.1%
0.0%
Overall:
97.0 %
2.7%
0.3%
0.0%
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