ML20217F063
| ML20217F063 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 04/22/1998 |
| From: | Terry C, Walker R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | Merschoff E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| TXX-98117, NUDOCS 9804280045 | |
| Download: ML20217F063 (22) | |
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Log # TXX-98117 h
nlELECTRIC FiE$101 Ref. # 10CFR50.55a c.s way s mar ne,rmsu Apri1 22, 1998 aprwp.ix es, ope,r r
Mr. E. W. Merschoff. Regional Administrator U. S. Nuclear Regulatory Commission. Region IV 611 Ryan Plaza Drive. Suite 400 Arlington. TX 76011
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION -UNIT 1 DOCKET NO. 50-445 UNIT 1 SIXTH REFUELING OUTAGE STEAM GENERATOR INSERVICE INSPECTION TUBE PLUGGING SPECIAL REPORT NO. 1-SR-98-002-00 to this letter provides the 15 day special report, submitted pursuant to CPSES Technical Specifications 4.0.6.5a. and 6.9.2.
a The results of the inspections resulted in steam generator 2 being placed in CPSES Technical Specifications 4.0.6.2 Category C-3. to this letter provides the special report pursuant to CPSES Unit 1 Technical Specifications 4.0.6.5c. and 6.9.2. provides the 12 month report pursuant to CPSES Technical Specification 4.0.6.5b and 6.9.2. Additionally, condition monitoring and operational assessment of the steam generator tube bundles has been j
performed and is being submitted as Enclosure 1 to this letter.
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9804280045 980422 PDR ADOCK 05000445
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COMANCHE PEAK STEAM FLECTRIC STATION P.O. Box 1002 Glen Rose. Texas 76043 1002 l
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'Page 2 of 2 If there are any questions. please contact Obaid Bhatty at (254) 897-5839 to coordinate this effort. This communication contains no new licensing basis commitments regarding CPSES Units 1 and 2.
l Sincerely.
0,b.
C. L. Terry _
v m b-By: ~ 'RoMr 0. Walker
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Regulatory Affairs Manager l-OB/ob.
Attachments Enclosure cc:
NRC Document Control Desk Mr. J. I. Tapia. Region IV Mr. T. J. Polich. NRR 6
Mr. G. Bynog. TDLR Resident Inspectors l
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. to TXX-9724S Page 1 of 1 TU ELECTRIC COMANCHE PEAK STEAM ELECTRIC STATION - UNIT 1 SPECIAL REPORT NO. 1 SR-98 002 00 UNIT 1. SIXTH REFUELING OUTAGE STEAM GENERATOR INSERVICE INSPECTION TUBE PLUGGING TECHNICAL SPECIFICATIONS 4.0.6.5a
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This attachment to the letter provides the Inservice Inspection (ISI) i l
Special Report on the steam generator tube ISI for Comanche Peak Steam Electric Station's sixth refueling outage (1RF06) on Unit 1.
This report l
I 1s being provided to you pursuant to CPSES Technical Specifications l
4.0.6.5a and 6.9.2.
Steam Generators 1. 2. 3 and 4 were inspected during 1RF06.
The examinations were complete on April 17, 1998. The number of tubes plugged during this outage in each steam generator is as follows:
CPSES Unit 1 Steam Generator No. 1: Zero (0) l CPSES Unit 1 Steam Generator No. 2: Sixty seven (67)
CPSES Unit 1 Steam Generator No. 3: Eight (8)
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I CPSES Unit 1 Steam Generator No. 4: Twenty seven (27)
Additional details on the plugged tubes and inspection effort pursuant to Technical Specification 4.0.6.5 are provided in Attachments 2 and 3 of the letter.
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,. Attachment 2 to TXX-98117 t
Page 1 of 2 TU ELECTRIC COMANCHE PEAK STEAM ELECTRIC STATION - UNIT 1 i
i SPECIAL REPORT NO. 1-SR-98-002 00 UNIT 1, SIXTH REFUELING OUTAGE STEAM GENERATOR INSERVICE INSPECTION TUBE PLUGGING 1
TECHNICAL SPECIFICATIONS 4.0.6.5c This attachment to the letter provides the Inservice Inspection (ISI)
Special Report on the steam generator tube ISI for Comanche Peak Steam Electric Station's sixth refueling outage (1RF06) on Unit 1.
The results of the inspections met the criteria of CPSES Technical Specification 4.0.6.2 Category C-3 for steam generator 2.
This report is being provided to you pursuant to CPSES Technical Specifications 4.0.6.5c and 6.9.2.
Planned Inspection Scope:
The initial scope of the inspection included 100 percent full length i
multi-frequency bobbin coil (except for row 1 and 2 U-bend region C11 to H11) and 100 percent hot leg top of tubesheet (HTS) Rotating Pancake Coil (RPC) (+ Point /0.115/0.080HF) on all four steam generators.
Additional scope for all four steam generators included 100 percent of row 1 and 2 U-bends (region C11 to H11) using RPC (+ point) and 20 percent of the expanded baffle plate B and D intersections in the cold leg preheater using RPC (+ Point /0.115/0.080HF).
Inspection Scope expansion:
The inspection scope was expanded to 20 percent cold leg top of tubesheet
+ point RPC. in steam generator 2.
No expansion was required by Technical Specification 4.0 6.2; nonetheless, a 20 percent expansion to the cold leg top of tubesheet region was conducted with Rotating Pancake Coil (RPC)
(+ Point /0.115/0.080HF) in accordance with the EPRI PWR Steam Generator ISI Guidelines.
- i Results
j Please refer to enclosure 1 to this letter, titled " Condition Monitoring and Operational Assessment Cycle 6 Inspection" Description of Investigation Conducted:
Please refer to enclosure 1 to this letter, titled " Condition Monitoring and Operational Assessment Cycle 6 Inspection".
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, to TXX-98117 Page 2 of 2 Cause of the Degradation:
TU Electric believes that the tube support plate (TSP) / top of tube support (TTS) outside diameter stress corrosion cracking (00 SCC) was caused by the temperature and the chemistry effects on the tubing material 4
(Inconel 600 MA). Additionally, the preheater wear is believed to be caused by flow induced vibration.
Corrective measures taken to prevent recurrence:
Chemical cleaning was performed during the CPSES Unit 1 fifth refueling outage (1RF05) to remove the chemical contaminants at the TTS and TSPs.
Prior to operation.140 tubes in each steam generator were expanded at the B and D baffle plate to reduce wear.
TV Electric has removed all known defective tubes from service.
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[- to TXX-98117 Page 1 of 8 TU ELECTRIC l
COMANCHE PEAK STEAM ELECTRIC STATION - UNIT 1 SPECIAL REPORT NO. 1 SR-98 002-00 UNIT 1 SIXTH REFUELING OUTAGE STEAM GENERATOR INSERVICE INSPECTION TUBE PLUGGING i-TECHNICAL SPECIFICATIONS 4.0.6.5b l
This attachment to the letter provides the 12 month Inservice Inspection (ISI) Special Report on the steam generator tube ISI for Comanche Peak This Steam Electric Station's sixth refueling outage (1RF06) on Unit 1.
report is being provided to you pursuant to CPSES Technical Specifications 4.0-6.5b and 6.9.2.
1)
Number and extent of tubes inspected:
TEST TYPE STEAM STEAM STEAM STEAM GENERATOR 1 GENERATOR 2 GENERATOR 3 GENERATOR 4 HL Bobbin 4566 4563 4570 4561 f
CL Expanded 50 50 50 50 Baf fles CL Bobbin 227 219 228 228 HL TTS RPC 4566 4563 4570 4561 U-bend RPC 227 219 228 228 CL TTs RPC N/A 916 N/A N/A l
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DEFINITIONS:
i HL-Hot Leg CL -
Cold Leg
[
RPC-Rotating Pancake Coil 1-TTS-Top of Tube Sheet l
e
. to TXX-98117 Page 2 of 8 2)
Location and percent of. wall-thickness penetration for each wear j
indication; 1
CPSES UNIT 1 STEAM GENERATOR 1 ROW COLUMN PERCENT LOCATION 48 79 3
C5 47 73 5
C3 48 79 5
C3 12 21 6
C6 12 22 6
C6 45 71 6
C3 48 73 6
C7 48 74 6
C7 48 77 7
C3 48 42 8
C3 48 75 8
C5 48 75 11 C2 48 73 17 C3 34 13 18 AV2 48 75 20 C3 4
48 73 22 C2 45 29 2R AV1 1
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. to TXX-98117 Page 3 of 8 2)
Location and percent.. (contd.):
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CPSES UNIT 1 STEAM GENERATOR 2 KUW LULUMN l'ERL EN I LUCA IIUN 47 40 2
C7 48 40 2
C8 48 38 3
C3 48 38 3
C3 47 39 3
C7 48 39 3
C5 48 39 3
C3 48 4.0 3
C3 19 43 3
C2 49 38 4
C7 48 39 4
C9 48 39 4
C7 48 40 4
C2 49 45 4
C7 42 62 4
C2 4'
68 4
C3 46 70 4
C3 48 39 5
C8 49 47 5
C7 45 48 5
C2 47 48 5
C2 45 60 5
C3 48 38 7
C7 48 38 7
C7 47 40 7
C2
.l 48 40 7
C7 46 45 7
C7
!.i 47 73 7
C3 47 45 8
C3 47 48 8
C3 47 49 8
C5 i
48 38 9
C2 I
48 38 9
C2 49 46 10 C7 47 49 10 C3 47 65 10 C3 46 67 11 C3 48 40 12 C5 47 67 27 C3 48 40 30 C3 l
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A.ttachment 3 to TXX-98117 5
Page 4 of 8 2) location and percent..
(contd.);
CPSES UNIT 1 STEAM GENERATOR 3 ROW COLUMN PERCENT LOCATION 47 37 3
C5 49 43 4
C7 43 48 4
C2 48 79 4
C5 48 81 4
C7 20 59 5
C3 21 59 5
C3 48 34 7
C7 46 41 7
C2 48 41 7
C2 l
48 42 7
C3 36 59 7
C3 45 62 7
C3 48 75 7
C5 27 56 8
C3 45 54 16 C3 43 59 22 AV2 41 59 23 AV3 47 49 30 C3 47 50 31 C3 43 59 31 AV3 i
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9 9 to TXX-98117 Page 5 of 8 2)
Location and percent.. (contd.):
CPSES UNIT 1 STEAM GENERATOR 4 ROW cot tlMN PERCENT t_OCATION 21 60 2
C3 47 36 4
C3 45 44 4
C2 35 56 4
C2 44 23 5
C2 33 59 5
C2 47 43 6
C5 47 48 6
C7 29 55 6
C2 t
4 46 66 6
C3 48 74 6
C2 48 32 7
C5 48 32 7
C3 48 34 7
C2 48 36 7
C2 45 44 7
C3 25 56 7
C2 30 59 7
C3 32 60 7
C3 46 63 7
C3 48 73 7
C2 16 87 7
C6 l
12 26 8
C6 45 24 9
C2 i
33 60 9
C3 47 66 9
C2 48 75 10 C2 j
48 34 11 C3 48 42 11 C5 I
'S C to TXX-98117 Page 6 of 8 2)
Location and percent... (contd.):
CPSES UNIT 1 STEAM GENERATOR 4 (Contd.)
ROW cot llMN PERCENT t OCATION 45 48 11 C3 47 48 11 C5 45 55 11 C3 33 59 11 C3 45 24 12 C2 48 39 12 C3 31 59 12 C3 29 56 13 C3 48 73 13 C3 48 74 16 C3 45 64 17 C3 48 75 17 C3 47 48 20 C3 45 53 20 C3 45 24 22 C3 48 74 25 C5 48 75 30 C5 47 88 47 C3 l
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e to TXX 98117 Page 7 of 8 3)
Idantification of tubes plugged:
CPSES UNIT 1 STEAM GENERATOR 1 NO TUBES WERE PLUGGED IN THE GENERATOR CPSES UNIT 1 STEAM GENERATOR 2 67 TUBES WERE PLUGGED IN THIS GENERATOR P=
n FROW COLUMN _ l R0W COLUMN ROW COLUMN R0W COLUMN 38 25 1
67 1
74 3
89 31 33 2
67 3
74 2
90 19 42 5
67 1
75 3
91 20 42 3
68 1
77 1
92 21 42 1
69 3
77 3
92 18 43 2
69 1
78 3
93 22 44 3
69 1
79 1
94 23 45 1
70 3
79 4
94 26 46 3
70 5
80 1
95 31 50 6
70 6
80 3
95 37 51 3
71 6
81 3
96 i
24 53 2
72 3
82 1
99 38 55 3
72 1
83 1
101 i
3 59 22 72 3
85 1-102 1
61 49 72 5
86 4
102 j
1 j
1 63 1
73 1
87 3
103 1
1 66 3
73 3
87 l
N/A N/A l
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,. to TXX-98117 Page 8 of 8 CPSES UNIT 1 STEAM GENERATOR 3 8 TUBES WERE PLUGGED IN THIS GENERATOR R0W COLUMN mm 3
29 3
30 29 63 10 109 11 109 10 108 9
109 10 110 l
CPSES UNIT 1 STEAM GENERATOR 4 27 TUBES WERE PLUGGED IN THIS GENERATOR l
R0W COLUMN R0W COLUMN mm mm 32 36 2
87 l
39 54 3
88 40 60 6
89 37 66 2
93 47 66 20 93 9
76 37 93 26 76 33 94 I
2 78 3
95 34 79 7
96 32 81 18 100 35 62 2'
101 2
'83 4
101 6
84 16 101 23 85 N/A N/A
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ENCLOSURE 1 TO TXX-97118 COMANCHE PEAK STEAM ELECTRIC STATION (CPSES) UNIT 1 CONDITION MONITORING AND OPERATIONAL ASSESSMENT l
CYCLE 6 INSPECTION:
MARCH-APRIL, 1998
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. to TXX-98117 Page 1 of 8 l
TABLE OF CONTENT
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Introduction and Background e
Summary and Conclusion e
Potential Degradation Mechanism and Inspection Method e
e Condition Monitoring: Tube Integrity Assessment e
Tubesheet Region 00 SCC Tube Support Plate ODSCC Volumetric Cycle 7 Operational Assessment e
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.. to TXX-98117 Page 2 of 8 CPSES UNIT 1 CONDITION MONITORING AND OPERATIONAL ASSESSMENT CYCLE 6 INSPECTION - MARCH - APRIL, 1998 INTRODUCTION AND BACKGROUND Condition Monitoring and Operational Assessment of the steam generator tube bundles has been performed to verify that the condition of the tubes, as reflected in the inspection results, is in compliance with t%
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plant licensing basis; defects detected have been evaluated to confim that the Regulatory Guide 1.121 margins against leakage and burst have not been exceeded at the end of the operating cycle (EOC).
The result?
l of the Condition Monitoring evaluation are used as the basis for an Operational Assessment, which demonstrates paospectively that the anticipated performance of the steam generattr tubes will not exceed the l-Regulatory Guide 1.121 margins against leakag 3nd tube burst during the I
ensuing operating interval.
CPSES Unit 1 has completed Cycle 6 (E0C) prior to this inspection. The Unit has 4 Westinghouse designed Model D4 Steam Generators each with 4578 mill annealed Inconel 600 U-bsnd tubes.
Each U-tube has a nominal i
diameter of 0.750 inches, a r.ominal tube wall of 0.043 inches, a straight l
length of 303.98 inches The tubesheet is 21 inches thick with a full depth hardrolled expansion. The inlet of the U-tubes is supported by i
seven (7) tube support plates (TSP) and a flow distribution baffle (FDB) plate near the tubesheet. The outlet is supported by five (5) TSPs, 5 I
pre-heater baffle plates (PBP) and the FDB.
The tube U-bends are l
supported by two (2) sets of Chrome plated Inconel anti-vibration bars.
The support plates, preheater baffle plates and flow distribution baffle i
are 0.75 inch thick and have round drilled holes.
All plates are manufactured from Grade 285 carbon steel.
During manufacture it was necessary to remove a number of tubes to allow for the instaliation and modification of a number of stay rods. The tubes were replaced and explosively expanded in the tubesheet by the WEXTEX process.
To reduce tube vibration, 140 tubes in cach steam generator were hydrauncally expanded at the B and D baffle plate in the preheater.
This expansion occurred before startup.
To reduce the susceptibility to Primary Stress Corrosion Cracking (PWSCC) all active tubes were shotpeened prior to startup.
Shotpeening was performed on both hot leg and cold legs in the tubesheet up to the Roll Transition Zone. The potential for U-Bend cracking was reduced by thermally stress relieving Row 1 and Row 2 U-Bands prior to startup.
Additionally, prior to power operation copper alloy from the secondary side of plant was removed.
The unit went critical in April 1990.
The Cycle 6 operating length was 479.6 EFPD (effective full power days).
Cycle 7 is planned for a length of 502 EFPD.
Summary and Conclusion
i l' to TXX-98117 Page.3 of 8 i
ODSCC associated with the hot leg rolled transition was found to be the l
predominant degradation mechanism seen during the CPSES 1RF06 inspection.
A total of ninety (90) tubes were plugged as a result of top of tubesheet ODSCC, four (4) tubes were plugged due to ODSCC at the tube-to-tube support plate intersection. three (3) tubes were plugged due to j
volumetric indication associated with wear. and an additional two (2) tubes were plugged as a result of addressing the information notice (IN) 88-02 analysis for U-bend fatigue.
Three additional tubes were administratively plugged. There was no instances of tube degradation identified in the cold leg hard rolled transition based upon the 20% Plus Point inspection performed for Steam Generator # 2.
None of the indications reported met the industry accepted threshold nondestructive ex3mination (NDE) screening criteria for leakage or structural integrity.
Growth rates based on consecutive inspection data associated with tubes exhibiting baffle plate and anti-vibration bar (AVB) wear were within expected progression. The condition of the tubes at the end of Cycle 6 meet all NRC accepted integrity levels.
The planned operating length for Cycle 7 is 502 EFPD compared to 479.6 EFPD (actual) for Cycle 6.
This 4.7% increase in operating length, with no planned changes in operating temperatures and steam pressure nor in the operating secondary side l
chemistry, is not expected to alter the performance of the steam-generator tubing during Cycle 7 operations. Therefore, the structural and leakage integrity condition of the CPSES Unit 1 steam generators. is expected to be bounded by the acceptable Cycle 6 performance.
POTENTIAL DEGRADATION MECHANISM AND INSPECTION METHOD L
Based on the assessment of prior inspection results, steam generator design features, and industry exper.ience with similar SGs the degradation mechanisms considered relevant at this point in time were as i
follows:
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l 1)
Tube wear at anti-vibration bar (AVB)1ocations. cold led peripheral l'
tubes which were expanded to reduce flow induced vibration (FIV),
and at locations accessible from the bundle periphery in conjunction with loose parts.
n 2)
CD pitting.
3)
PWSCC within the hot leg tubesheet associated within the hardroll transition.
U 4)
U-bend PWSCC associated with small radius U-bends.
5)
ODSCC at the top of the tubesheet and within tube-to-tube support
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plate crevices.
l 6)
Cold leg freespan cracking.
l 7)
In preparation for the IRF06 inspection, an assessment was made of the NDE techniques to provide assurance that appropriate detection and sizing pe.-farmance existed to support growth rates, repair criteria and structural limits for the above noted degradation mechanisms.
. to TXX-98117 Page 4 of 8 Degradation Degradation Location (s)
Probe Type IRf06
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Type Classification Inspection Plan ODSCC Active Hot Leg Top of Plus 100% all Hot Tubesheet Point Leg Tubes ODSCC/PWSCC Act1ve Tube Support Plate Bobbin 100% in all S/G's Intersections Free Span Plus Confirmation Point as required Tube Wear Act1ve AVB 60bbin 100% Full length Preheater Baffle Bobbin Plate 100% H/L Top Loose Parts Bobbin of tubesheet for loose Loose Parts Plus parts Point PWSCC Relevant Row 1 and Row 2 Plus 100% in all U-bends Point S/G's Active Hot Leg Roll Plus 100% in all Transition Point S/G's Relevant Expanded 20% in all Transition Baffle Plus S/G's Plate B and D Point 1
00 Pitting Relevant Top of Tubesheet BODb1n 100% in all a
S/G's Dent SCC Relevant All Hot Leg Tubes Plus As Required with Dents at H3 Point The EPRI guidelines identify forms of degradation as " active". " relevant" or " potential"
" Active degradation mechanisms" are those mechanical or corrosive processes reported as newly observed or progressing from prior inspections. The EPRI Guidelines define an " active degradation mechanism" as a combination of 10 or more new indications of degradation (> or - to 20% TW) and previous indications of degradation which display an average p
growth rate > or - to 25% of the repair limit per cycle in any one S/G.
Alternatively the existence of 1 or more new or previously identified indications of degradation, including cracks, which display a growth > or
- to the repair limit in one cycle of operation shall require designation of the degradation mode as an active degradation mechanisms.
" Relevant degradation mechanisms" are those mechanical or corrosive processes not found at Comanche Peak Unit 1 in prior inspection, but have been reported in other plants with steam generators of similar design and materials of construction.
" Potential degradation rr chanisms" are those mechanical and corrosive processes not found in imilar plants but judged to have a meaningful potential to occur based on historical and/or laboratory data.
- to TXX-98117 Page 5 of 8 As was detailed above the IRF06 inspection program involved 100% full j
length bobbin inspection (except for row 1 and 2 region C11 to Hil).100%
Plus Point inspection of all H/L tube expansion transition zones.
100%
Plus Point inspection of Row I and 2 U-bends (region C11 to Hil), and a 20% Plus Point inspection of the C/L baffle plates B and D tube expansion regions. All crack like indications were sized using slow speed Plus Point probes.
It should be noted that all crack like indications were plugged.
This data was used to screen for in situ testing. The guidelines for selection of indications for testing are based on indication burst and leakage characteristics consistent with current NRC and industry guidance. These guidelines provide threshold values for NDE parameters that must be exceeded to perform in situ testing. All indications were evaluated against the thr6 hold values relative to the need to demonstrate tube integrity by insitu leak and pressure testing.
CONDITION HONITORING: TUBE INTEGRITY ASSESSMENT The total number of tubes removed from service during 1RF06 is shown below:
Steam TT5 Circumferential TT5 Volumetric T5P Baffle Total Generator ODsCC Axial Axial Plate Tubes ODKCr OD9ec Wear Pluaand
- 1 0
0 0
0 0
0
- 2 63 2
2(a.b) 0 0
67
- 3 3
0 0
0 0
8(c)
)
I
- 4 22 0
0 4
1 27 (a)
R38C25 plugged oue to loose part wear (b)
R49C72 plugged due to indication at C2 and C3 baffle plate (c) 2 tubes plugged due to 88-02 related analysis, and 3 additional tubes 9
plugged to address difficulties encountered during dampener installation in R10C109 Tubesheet (TTS) Region Degradation h
ODSCC Circumferential Cracking 00 SCC at the hot leg expansion transition was the only " active i
degradation mechanism" identified during the IRF06 inspection. A total of 88 tubes (2 tubes were characterized as MMI - mixed mode -
i circumferential and axial) exhibited ODSCC at the hot leg too of i'
tubesheet.
Re-testing of these tubes during the Positive Identification program confirmed them to be ODSCC based on phase angle. Using the information provided by the Plus Point inspection.
all indications were screened against the threshold NDE parameters established by EPRI to assess tube integrity. A sequential screening process was performed.
For pressure testing. the sequential screening consisted of: 1) crack angle. 2) average voltage, and 3) Percent Degraded Area (PDA).
For leak testing. the sequential screening consisted of: 1) maximum voltage. 2) maximum depth, and 3) depth profile.
The screening threshold parameters were as follows:
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, to TXX-98117 Page 6 of 8 l
CAmt -
237' (Crack angle throughwall structural limit that l
satisfies 3 Delta P burst capability);
VHm =
1.25 volts (Maximum voltage threshold for significant probability of leak, based on 00 SCC);
i f
0.33 volts (Average voltage threshold value that AVm l
=
l satisfies 3 Delta P burst capability):
DMm -
75% (Depth threshold for throughwall penetration j
recognizing uncertainty in measuring crack depth);
i PDAn =
77% (Percent degraded area corresponding to the single uniform throughwall flaw model using conservative stiffness assumptions).
None of the indications met the EPRI guidelines for in situ testing.
l However, due to the array of circumferential indications, a tocal of ten (10) were selected for pressure and leN ' es i.i ng.
These indications represent the highest maximum and avr.a voltage t,ased on eddy current voltage integral analysis. The selested tubes were leak tested at 1441, 2500, and 2925 psi and proof pressure tested at 4315 psi.
No leakage or tube burst occurred.
TUBE ELEVATION INDICATION CRACK MAXIMUM MAXIMUM AVERAGE LOCATION ANGLE VOLTAGE DEPTH VOLTAGE j
INTFGRAL RICo:t MI5+0.12" SCI 296 0.43 694 0.10 RIC73 HTS-0.17" SCI 326 0.47 57%
0.18 RIC95 HTS 0.32" SCI 337 0.44 46%
0.20 R3C96 HTS-0.25" SCI 350 0.47 60%
0.15 R3C103 HTS-0.14" SCI 360 0.38 67%
C.17 l
R24C53 HTS-0.24" MMI N/A 0.31 N/A 0.11 RIC61 hts-0.21" SCI 223 0.37 60%
0.ls R3C71 His-0.02" SCI 326 0.34 67%
0.19 R3C74 HTS MCI 355 0.31 59%
0.19 R3C87 HTS-0 05" SCI 342 0.36 0 53%
0 16 I
All circumferential indications in the tubesheet expansion transitions i
satisfy condition monitoring pressure and leakage integrity requirements.
l No SLB leakage would be expected.
ODSCC Axial Indications Two (2) tubes were plugged due to axial 00 SCC at the tubesheet expansion transitions. These indications were screened against an in situ screening criteria developed by Westinghouse. The inspection data is shown below:
Tube Elevation Crack Maximum t cecth Vol t ace y ocatien R31-C50 HTS-0.05" 0.152" 0.29 oc.rc6 uTS n cA=
n 15?
n al The screening threshold parameters for straight leg axial indications were as follows:
. to TXX-98117 Page 7 of 8 1
Lm =
0.51 inch (Crack length structural limit that satisfies 3 Delta P burst capability).
HD,., =
70% (Maximum threshold flaw depth corresponding to 3 Delta P burst capability),
MD.
=
75%
(Maximum threshold flaw depth threshold for t
significant probability of leak).
VMm =
1.50 volts (Maximum voltage threshold for significant probability of leak),
Vcm =
2.50 inch (Threshold voltage for significant SLB leakage).
AD..no =
0.6"/67%, 0.7"/63%. 0.8"/61%, 0.9"/59%,1.0*/56%
(Average indication depth as a function of length for an assumed 1.5" long flaw).
Neither tube met the conditions for in situ testing.
Both tubes satisfied the requirements for operational leakage and structural burst.
Tube Support Plate (TSP) ODSCC A total of four (4) indications in Steam Generator #4 were plugged due to tube support plate 00 SCC degradation.
All indications were contained within the support plate and exhibited voltages as shown below.
All tubes satisfied the requirements for operational leakage and structural burst.
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um5E E MelMimauss0$$MuMdilEmai R32C36 H5 0.24 R39C54 H5 0.89 b
R26C76 H5 0.66 R32C81 H3 0.61 Volumetric Indications Three (3) tubes were plugged due to volumetric related degradation.
Location R47C66 in steam generator # 4 was plugged due to C3 baffle plate wear: R49C72 was plugged due to a volumetric indication within the C2 and C3 plates; R38C25 was stabili::ed and plugged due to wear associated with a potential loose part abovs the H5 support plate.
All tubes satisfied the re'*uirements for operational leakage and structural burst. In addition to the above noted indications. AVB and 1
preheater baffle plate wear was noted in a number of tubes which remained inservice with acceptable but progressive growth rate.
AVB Wear A total of four (4) tubes exhibiting five (5) AVB wear sites were identified.
Four (4) of the sites showed a slow progression of growth when compared to Cycle 5 results.
One (1) new tube location wat identified with AVB wear. The maximum wear depth of 31% was reported at AVB3 in S/G #3 at R43C59. This indication falls substantially below the structural limit for 0.5 inch uniform wall loss of 75% based on 3 times nortral operating delta P or 74% for 1.428 times steam line
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- to TXX-98117 Page 8 of 8 break. based on NUREG/CR-0718.
Even when applying an industry
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accepted uncertainty of 12.8% to the eddy current sizing, this indication nor any of those of lesser percent violate the Reg. Guide 1.121 margins for structural and leakage integrity.
Baffle Plate s
A total of ninety six (96) baffle plate wear sites sere noted.
Fifty-five (55) of.these wear sites could be traced back to the prior inspection, with the remaining being considered as new wear sites.
Based All wear indications were evaluated to verify tube integrity.
on bobbin data sizing. the largest oercent wear depth of 47% was noted at the C3 baffle plate for R47C66. This wear depth is substantially below the structural limit for 0.5 inch uniform wall loss of 75% based on 3 times normal operating delta P or 74% for 1.428 times SLB. based on NUREG/CR-0718.
Even when applying an industry accepted uncertainty of 12.8% to the eddy current sizing. this indication nor any of those of lesser percent violate the Regulatory Guide 1.121 margins for structural and leakage integrity.
CYCLE 7 OPERATIONAL ASSESSMENT ODSCC associated with the hot leg rolled transition was found to be the predominant degradation mechanism seen during the CPSES 1RF06 inspection.
None of the indications reported met the industry accepted threshold NDE screening criteria for leakage or structural integrity. All detected ODSCC indications were plugged following Cycle 6 operation. None of the reported degradation mechanisms challenge tube integrity. The structural and leakage integrity condition of the tubing during Cycle 7 is expected to be counded by acceptable Cycle 6 conditions as established by inspection of the tube bundle and the successful completion of in situ testing.
q Growth rates based on consecutive inspection data associated with tube exhibiting baffle plate and AVB wear were within expected progression The average growth rate for all AVB wear indications was found to be /%.
well within industry experience of 8-10% per cycle. Within the largest 4
AVB wear indication remaining in service at the beginning of Cycle 7 being 31%.
there is sufficient margin to assure that the structural limits for AVB wear will not be exceeded during Cycle 7.
The growth rate for all baffle plate wear indications was determined to be 5,47% during Cycle 6.
With the largest baffle plate wear indication remaining inservice at the begiening of Cycle 7 being 31%. there is sufficient margin to assure that the structural limit for baffle plate wear will not be exceeded daring Cycle 7.
As determined by the ConditiLa Monitoring assessment the condition of the tubes at the end of Cycle 6 meet all NRC accepted integrity levels. The planned operating length for Cycle 7 is 502 EFPD compared to 479.6 EFPD (actual) for Cycle 6.
This 4.7% increase in operating length, with no planned changes in operating temperatures and steam pressure nor in the operating secondary side chemistry. is not expected to alter the performance of the steam generator tubing during Cycle 7 operations.
l Therefore, the structural and leakage integrity condition of tne Comanche Peak Unit 1 steam generators. is expected to be bounded by the acceptable H
Cycle 6 performance.
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