05000483/LER-2004-006, A Steam Generator Tube Inspection Results Classified as C-3
| ML041560005 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 05/25/2004 |
| From: | Witt W AmerenUE, Union Electric Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| ULNRC05011 LER 04-006-00 | |
| Download: ML041560005 (14) | |
| Event date: | |
|---|---|
| Report date: | |
| 4832004006R00 - NRC Website | |
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AmerenUE Callaway Plant PO Box 620 Fulton, MO 65251 May 25, 2004 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop P1-137 Washington, DC 20555-0001 ULNRC0501 1 UE Ladies and Gentlemen:
DOCKET NUMBER 50-483 CALLAWAY PLANT UNIT 1 UNION ELECTRIC CO.
FACILITY OPERATING LICENSE NPF-30 LICENSEE EVENT REPORT 2004-006-00 "A" Steam Generator tube inspection results classified as C-3 The enclosed licensee event report is submitted in accordance with Technical Specification 5.5.9 and 5.6.10(c) report the Refuel 13 Inservice Inspection Results for the "A" Steam Generator were classified as C-3 due to greater than one percent of the inspected tubes being defective. Included with this License Event Report is the Special Report and Attachment detailing the "A" Steam Generator tube inspection results.
This event was initially reported in Event Notification#40705 in which it stated that this report was required by an Administrative Technical Specification and that the "A" Steam Generator tubes do not meet the criteria for serious tube degradation and thus does not represent a degraded or unanalyzed condition.
This letter does not contain new commitments.
Sincerely, Warren A. Witt Manager, Callaway Plant Enclosure J6
a aubsidiaqy of Ameren Cotporation
W t, -,;
7 ULNRC05011 May 25, 2004 Page 2 Mr. Bruce S. Mallett Regional Administrator U.S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-4005 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. Jack N. Donohew (2 copies)
Licensing Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 7E1 Washington, DC 20555-2738 Missouri Public Service Commission Governor Office Building 200 Madison Street PO Box 360 Jefferson City, MO 65102-0360 Records Center Institute of Nuclear Power Operations 700 Galleria Parkway Atlanta, GA 30339
Abstract
At 1906 CDT, 4/26/04, in Event Notification 40705, Callaway reported the following:
"During Refueling Outage RF1 3, interim results of "A" Steam Generator (S/G) tube inspections indicate 59 tubes out of 5341 tubes (i.e., greater than 1 percent) have been determined to be defective. This S/G tube inspection result for the "A" S/G is classified as category C-3 in accordance with Technical Specification 5.5.9, Table 5.5.9-2. Per NUREG 1022, Section 3.2.4 Discussion (A)(3), the present C-3 classification of the "A" S/G tubes does not meet the listed criteria for serious S/G tube degradation and thus is not a degraded or unanalyzed condition. Since this report is required by Administrative Technical Specification 5.5.9, this notification is being listed as an "Other Unspecified Requirement".
All defective tubes will be removed from service before the S/G is returned to service. There were no adverse safety consequences or implications as a result of this event. This event did not adversely affect the safe operation of Callaway Plant or the health and safety of the public."
This LER is submitted in compliance with Technical Specification 5.5.9 and 5.6.1Oc requirements and not due to an actual serious S/G tube degradation. Final results from Steam Generator A examinations resulted in a total of 100 tubes being plugged.
NREC FOM 36 (7-2001)
I (If more space is required, use additional copies of NRC Formn 366A) (17)
I.
DESCRIPTION OF THE REPORTABLE EVENT
A. REPORTABLE EVENT CLASSIFICATION This condition is being submitted per Technical Specification 5.5.9 and 5.6.1Oc requirements and reported as an "Other Unspecified Requirement" because this does not represent an actual serious SIG tube degradation as discussed in NUREG 1022 Revision 2, Section 3.2.4.
B. PLANT OPERATING CONDITIONS PRIOR TO THE EVENT This condition was discovered during Refuel 13 while in Mode 6 with the core off loaded.
C. STATUS OF STRUCTURES, SYSTEMS OR COMPONENTS THAT WERE INOPERABLE AT THE START OF THE EVENT AND THAT CONTRIBUTED TO THE EVENT Callaway Plant was in Mode 6 with the core off loaded during Refuel 13.
D. NARRATIVE SUMMARY OF THE EVENT, INCLUDING DATES AND APPROXIMATE TIMES See attached "Special Report to the NRC - Steam Generator A (EBB01A) Categorized as C-3 Condition In Refuel 13" and Attachment 1 - Indications Identified in Steam Generator A During RF13".
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SPECIAL REPORT TO THE NRC STEAM GENERATOR A (EBBOIA) CATEGORIZED AS C-3 CONDITION IN REFUEL 13 At 1711 on 04/26/04, AmerenUE Callaway Plant determined that Steam Generator 'A' qualified as Category C-3 in accordance with the requirements of Technical Specification (TIS) 5.5.9, Table 5.5.9-2. At 1906 that same day, the required ENS notification#40705 was made to the NRC Operations Center per 10CFR50.72(b)(2).
Additionally, T/S 5.5.9 refers to T/S 5.6.10 for further reporting requirements. T/S 5.6.10(c) states, "Results of steam generator tube inspections, which fall into Category C-3, shall be reported to the Commission within 30 days and prior to resumption of plant operations. This report shall provide a description of investigations conducted to determine cause of the tube degradation and corrective measures taken to prevent recurrence."
This report is intended to satisfy that requirement.
Callaway Steam Generator History The Westinghouse Model F steam generators installed at Callaway consist of approximately 78% low temperature mill annealed (LTMA) Alloy 600 tubing and 22%
(innermost 10 rows) Alloy 600 thermally treated (TT) tubing.
Callaway Plant first identified primary and secondary side Stress Corrosion Cracking (SCC) of the steam generator tubes in 1995 (Refuel 7). Since that outage, all four steam generators have been inspected each refueling, with the result that an increasing number of tubes have been repaired due to corrosion of the tubes at the hot leg top-of-tube sheet as shown in Figure 1 and Table 1. Sample Rotating Pancake Coil (RPC) inspections are performed each outage at the support plates (dents), low row U-bends, and free span (dings) areas to provide early identification of any cracking that may occur in these locations. None have been identified to date.
The trend of top-of-tube sheet indications in all four steam generators is provided in Figure 1.
The extent of the tube degradation found in Refuel 13 was not unexpected. Past inspection results and tube degradation prediction models indicated that the degradation of the mill-annealed tubing would accelerate as the plant ages. This has generally been true of other plants with original Westinghouse steam generators fabricated with Alloy 600 LTMA tubing.
The tube degradation model for Callaway was updated prior to Refuel 12. Based on past experience, plant operating conditions, and experience at other plants, 163 tubes were predicted to be defective due to SCC (ID and OD) and Intergranular Attack / Stress Corrosion Cracking (IGA/SCC). The actual number identified was 150 in all four steam generators at the expansion transition or in the expanded portion of the tubing found using a Rotating Pancake Coil (RPC). Of the tubes found with tube sheet defects, 100 were found in steam generator A, as shown in Table 2 and Attachment 1. Since the number of defective tubes exceeded 1% of the inspected population for RPC inspection, the inspection results are classified as C-3.
ULNRC0501 1 May 25, 2004 Special Report As Figure 1 demonstrates, steam generator A has consistently had more SCC indications than any other steam generator. No service-induced degradation was identified in the 600 TT tubing.
120 -
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-- 0--S/GB 100 00 60-40 if Jun-94 Oct-95 Mar-97 Jul-98 Dec-99 Apr-01 Sep-2 Jan-04 DATE Figure 1 Top-of-Tube Sheet Cracks-Trending by Steam Generator Examination of Steam Generator A The original inspection scope for 'A' steam generator was as follows:
100% (5341 tubes) of the hot leg top-of-tubesheet with a +Point RPC probe 100% inspection of the full-length of all the tubes. All straight sections were inspected with a standard bobbin coil probe. 5100 U-bends were inspected with a standard bobbin coil probe, the remaining 241 U-bends were inspected with a
+Point RPC probe.
Upon completion of the original scope of inspection, a total of one hundred (100) tubes (as shown on Table 1) required repair due to stress-corrosion cracking or IGA indications at the expansion transition region or in the expanded portion of the tube.
C_'n/
May-05 2
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,z t ULNRC0501 1 May 25, 2004 Special Report No indications were discovered in the extended region added to the inspection scope in Refuels 12 and Refuel 13 using the new H-star requirements for the top-of-tube sheet inspections.
Investigation of Cause of Degradation Stress Corrosion Cracking (PWSCC/ODSCC) has been identified in the hot leg tube sheet expansion and transition regions in all Westinghouse designed steam generators (operating at 6070F or above) fabricated with LTMA tubing which were not peened prior to the start of plant operations.
Callaway Plant has determined that, based on the definition of an active damage mechanism provided in the EPRI PWR Steam Generator Examination Guidelines, hot leg expansion axial/circumferential PWSCC and hot leg top-of-tube sheet ODSCC/IGA are active damage mechanisms in Callaway's steam generators.
Stress Corrosion Cracking occurs in the high stress expansion transition located at or below the top of the tube sheet and can initiate from either the primary or secondary side. Stress Corrosion Cracking occurs due to the combination of the following:
High residual stresses in the expanded portion of the tubes and particularly at the expansion transition, Elevated temperature for an extended period of time, Susceptible material such as Alloy 600 LTMA tubing All indications identified at the top of the tube sheet are small in size as shown in Figures 2 and 3. None exceeded the condition monitoring limits for the specific type of degradation identified. No in-situ testing was performed based on screening criteria developed in the Plant's Degradation Assessment in accordance with the EPRI Steam Generator In-Situ Pressure Test Guidelines. The screening criterion are specified based on the type of degradation that exists or could potentially exist in the steam generators.
No indications in Steam Generator A exceeded these screening criterion.
There were no new forms of degradation found in Steam Generator A. All forms of degradation were anticipated and addressed in the Refuel 13 Degradation Assessment.
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ULNRC05011 May 25, 2004 Special Report
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IIi Length of Axial Indication Figure 2 Refuel 13 Steam Generator Axial Indications 180 160 140 120 100 80 40 2 0 -I I T I l l i l 1 1 1 1 1 1 1 1 1 0t~~~~~~N,q S
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Figure 3 Refuel 13 Steam Generator A Circumferential Indications 4
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ULNRC0501 1 May 25, 2004 Special Report Table I Steam Generator A Indications and Tubes Repaired Since Refuel 7 Indication RF07
- RFO8 RF09
- RF10 RFNI RF12 RF13 Axial ID 5
9 14 15 23 39 77 Circumferential ID 4
26 17 21 2
43 25 Axial OD 0
0 1
0 0
0 0
Axial unknown 1
3 0
0 0
0 0
Circumferential OD 2
1 0
3 1
0 0
Circumferential 0
6 0
0 0
0 0
unknown Volumetric 0
5 0
3 0
4 0
indications Mixed Mode ID 0
0 0
0 0
0 1
indications Total tubes with 11 47 32 41 26 84 100 TTS indications Tubes plugged for 0
0 0
0 0
3 0
AVB wear Tube plugged for 0
0 0
1 0
4 0
TSP wear l
Tube plugged for 0
0 0
0 0
0 0
loose parts I
Total tubes repaired 11 48 32 42 26 91 100
- 44 tubes sleeved with Westinghouse Laser Welded Sleeves at the top of the tube sheet.
- 31 tubes sleeved with Framatome Electrosleeves at the top of the tube sheet.
Refuel 7-1 tube has both axial and circumferential PWSCC Refuel 12 - 2 tubes have both axial and circumferential PWSCC Refuel 13-1 tube has both axial and circumferential PWSCC Table 2 Steam Generator A Tubes Plugged Inspection Period Steam Generator A Pre-service 8
Refuel 1 0
Spring '87 Refuel 2 3
Refuel 3 Refuel 4 6
Refuel 5 Refuel 6 19 Refuel 7 1 1 Refuel 8 4
Refuel 9 32 Refuel 10 11 Refuel 11 26 Refuel 12 91 Refuel 13 100 Total 311 Steam Generator A is 5.53% plugged Equivalent plugging due to sleeves is 5.57%
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ULNRC0501 1 May 25, 2004 Special Report 0
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06
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0 1 O-9 Dec-9 Apr Sep-0 J, r M
Jun-94 Oct-95 Mar-97 Ju1-98 Dec-99 Apr-01 Sep-02 Jan-04 May-05 Outages Figure 4 Steam Generator A Cumulative TTS Degradation 0
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z 80 70 Axial PWSCC
- - 4unknown circ 50
unknown axial 40 30 20 10-
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Jun-94 Oct-95 Mar-97 Jul-98 Dec-99 Apr-01 Sep-02 Jan-04 May-05 Outages Figure 5 Steam Generator A Cumulative TTS Degradation by Type C 62-6
ULNRC0501 1 May 25, 2004 Special Report Actions to Prevent Recurrence All tubes with detected degradation at the top of the tube sheet were plugged in Steam Generator A. Additionally, all tubes with circumferential crack indications were stabilized. Callaway Plant anticipates similar degradation will be present in the steam generators at the end of Cycle 14. This is based on industry operating experience with Alloy 600 LTMA tubing and plant specific inspection results for the last 7 inspections.
Callaway will replace all four steam generators in Refuel 14.
Callaway Plant will continue to follow the requirements of NEI 97-06 and the referenced EPRI guidelines for future cycles of operation. These guidelines include requirements for primary and secondary water chemistry, primary to secondary leakage monitoring, inspection scope and frequency, pressure testing of degraded tubes, and integrity assessments to ensure tube structural and leakage integrity.
Condition Monitoring and Operational Assessments were performed in accordance with the EPRI Integrity Assessment Guidelines to address the as-found condition of the steam generator tubing to justify operation through Cycle 14. The assessments are based on identified degradation and use conservative analysis to assure tube structural and leakage integrity for the entire cycle length.
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ATTACHMENT 1-INDICATIONS IDENTIFIED IN STEAM GENERATOR A DURING RF 13 ROW COL REPAIR REASON FOR IN-SERVICE REPAIR HOT LEG-COLD LEG 11 33 PLUGGED PLUGGED SAI @ TSH +0.05 NO 11 48 PLUGGED PLUGGED SAI @ TSH -0.35 NO a
PLUGGED PLUGGED SAI @ TSH +0.06 NO 11 53 PLUGGED PLUGGED SAI @ TSH +0.14 NO 11 54 PLUGGED PLUGGED SAI @TSH +0.10 NO 11 57 PLUGGED PLUGGED SAI @ TSH +0.11 NO 12 59 PLUGGED PLUGGED SAI @ TSH +0.08 NO 12 74 PLUGGED PLUGGED SAI @ TSH +0.12 NO 12 96 PLUGGED PLUGGED SAI @ TSH -0.00 NO 13 51 PLUGGED PLUGGED SAI@ TSH +0.00 NO 14 60 PLUGGED PLUGGED SAI @ TSH +0.10 NO 15 40 PLUGGED PLUGGED SAI @ TSH +0.04 NO 16 55 PLUGGED PLUGGED SAI. TSH -0.18 NO 16 57 PLUGGED PLUGGED SAI @ TSH +0.10 NO 16 65 PLUGGED-STABILIZED PLUGGED SCI @ TSH +0.18 NO 16 68 PLUGGED PLUGGED SAI @ TSH +0.10 NO 17 36 PLUGGED PLUGGED SAI @ TSH +0.06 NO 18 20 PLUGGED PLUGGED MAI
. TSH +0.06 NO 18 47 PLUGGED PLUGGED SAI @ TSH +0.06 NO 19 44 PLUGGED PLUGGED MAI @ TSH +0.03 NO 19 50 PLUGGED PLUGGED SAI @ TSH +0.05 NO 19 67 PLUGGED PLUGGED SAI @ TSH +0.15 NO 19 74 PLUGGED-STABILIZED PLUGGED SCI @ TSH +0.15 NO 19 86 PLUGGED PLUGGED SAI @ TSH +0.09 NO 19 97 PLUGGED PLUGGED SAI @ TSH +0.04 NO 19 100 PLUGGED PLUGGED SAI @ TSH -0.06 NO 20 52 PLUGGED-STABILIZED PLUGGED SCI @ TSH +0.08 NO 20 67 PLUGGED PLUGGED SAl @ TSH +0.12 NO 20 85 PLUGGED PLUGGED SAI @ TSH +0.10 NO 21 36 PLUGGED PLUGGED SAI @ TSH +0.09 NO 21 46 PLUGGED PLUGGED MAI a TSH +0.05 NO 21 52 PLUGGED PLUGGED MAI @ TSH +0.09 NO 21 85 PLUGGED-STABILIZED PLUGGED SCI @ TSH +0.13 NO 22 38 PLUGGED PLUGGED SAI @ TSH +0.15 NO 22 52 PLUGGED PLUGGED MAI @ TSH -0.09 NO 22 68 PLUGGED PLUGGED SAI @ TSH +0.04 NO 22 71 PLUGGED PLUGGED MAI @ TSH +0.07 NO 22 90 PLUGGED PLUGGED MAI @ TSH -0.03 NO 23 71 PLUGGED-STABILIZED PLUGGED SCI @ TSH -0.25 NO I
u PLUGGED-STABILIZED PLUGGED SAI @ TSH +0.14 NO 23 83 PLUGGED-STABILIZED PLUGGED SCI @ TSH +0.02 NO 23 88 PLUGGED PLUGGED SAl @ TSH -0.03 NO 23 94 PLUGGED PLUGGED MAI @ TSH +0.09 NO 24 101 PLUGGED PLUGGED MAI a TSH +0.08 NO 25 66 PLUGGED PLUGGED MAI @ TSH +0.10 NO Page 1 of 3
ATTACHMENT I - INDICATIONS II)ENTIFIED IN STEAM GENERATOR A DURING RF 13 26 43 PLUGGED PLUGGED SAI @ TSH +0.07 NO 26 52 PLUGGED PLUGGED SAI @ TSH +0.11 NO 26 56 PLUGGED PLUGGED SAI @ TSH +0.05 NO 26 72 PLUGGED PLUGGED SAI @ TSH +0.06 NO 27 73 PLUGGED PLUGGED SAI @ TSH -0.00 NO 27 75 PLUGGED PLUGGED SAI @ TSH +0.06 NO 27 85 PLUGGED PLUGGED SAI @ TSH +0.06 NO 27 88 PLUGGED PLUGGED SAI @ TSH +0.03 NO 30 45 PLUGGED PLUGGED SAI @ TSH -0.02 NO 30 61 PLUGGED-STABILIZED PLUGGED SCI @ TSH +0.10 NO 30 96 PLUGGED-STABILIZED PLUGGED MMI @ TSH +0.11 NO 31 53 PLUGGED PLUGGED MAI D TSH +0.11 NO 32 52 PLUGGED-STABILIZED PLUGGED SCI @ TSH +0.08 NO 32 61 PLUGGED-STABILIZED PLUGGED SCI @ TSH -0.17 NO 32 93 PLUGGED-STABILIZED PLUGGED SCI @ TSH +0.06 NO 33 69 PLUGGED-STABLIZED PLUGGED SCI @ TSH +0.05 NO 33 100 PLUGGED PLUGGED SAI TSH +0.03 NO 35 53 PLUGGED-STABILIZED PLUGGED MCI @ TSH +0.11 NO 35 63 PLUGGED PLUGGED SAI @ TSH +0.05 NO 35 94 PLUGGED-STABILIZED PLUGGED SCI @ TSH +0.12 NO 35 108 PLUGGED PLUGGED SAI @ TSH +0.05 NO 36 99 PLUGGED PLUGGED SAI TSH +0.10 NO 36 102 PLUGGED PLUGGED SAI @ TSH +0.10 NO 37 103 PLUGGED PLUGGED SAI @ TSH +0.05 NO 38 89 PLUGGED PLUGGED MAI @ TSH +0.11 NO 38 91 PLUGGED-STABILIZED PLUGGED SCI @ TSH +0.13 NO 38 97 PLUGGED PLUGGED SAI TSH +0.14 NO 39 84 PLUGGED-STABILIZED PLUGGED SCI @ TSH +0.10 NO 39 89 PLUGGED PLUGGED SAI@ TSH +0.04 NO 40 51 PLUGGED PLUGGED SAI @ TSH +0.09 NO 40 53 PLUGGED PLUGGED SAI @ TSH -0.01 NO 40 58 PLUGGED PLUGGED SAI TSH +0.03 NO 40 60 PLUGGED PLUGGED SAI @ TSH +0.08 NO 41 62 PLUGGED-STABILIZED PLUGGED MCI @ TSH +0.11 NO 41 85 PLUGGED PLUGGED SAI @ TSH +0.10 NO 41 86 PLUGGED PLUGGED SAI TSH +0.10 NO 42 54 PLUGGED PLUGGED SAI TSH +0.04 NO 42 57 PLUGGED PLUGGED SAI TSH +0.03 NO 43 57 PLUGGED-STABILIZED PLUGGED SCI @ TSH +0.05 NO 43 62 PLUGGED-STABILIZED PLUGGED SCI @ TSH -0.03 NO 44 50 PLUGGED-STABILIZED PLUGGED SCI @ TSH +0.04 NO 44 54 PLUGGED PLUGGED MAI @ TSH +0.06 NO 45 71 PLUGGED PLUGGED SAI @ TSH +0.01 NO 45 74 PLUGGED PLUGGED MAI @ TSH +0.08 NO 45 82 PLUGGED PLUGGED SAI @ TSH +0.05 NO 46 59 PLUGGED-STABILIZED PLUGGED MCI @ TSH +0.11 NO 46 74 PLUGGED-STABILIZED PLUGGED SC0 @ TSH +0.11 NO 47 73 PLUGGED-STABILIZED PLUGGED SCI @ TSH +0.04 NO 49 66 PLUGGED-STABILIZED PLUGGED SCI @ TSH -0.03 NO Page 2 of 3
ATTACHMENT I - INDICATIONS IDENTIFIED IN STEAM GENERATOR A DURING RF 13 50 61 PLUGGED PLUGGED MAI a TSH +0.06 NO 50 62 PLUGGED PLUGGED MAI @ TSH +0.05 NO 51 55 PLUGGED PLUGGED SAI @ TSH -0.06 NO 51 62 PLUGGED-STABILIZED PLUGGED MCI @ TSH +0.06 NO 51 80 PLUGGED-STABILIZED PLUGGED SCI @TSH -0.13 NO 54 61 PLUGGED PLUGGED SAI. TSH +0.11 NO 55 60 PLUGGED PLUGGED SAI @ TSH +0.17 NO 55 61 PLUGGED PLUGGED MAI @ TSH +0.14 NO SAI MAI SCI MCI MMI TSH Single Axial Indication Multiple Axial Indication Single Circumferential Indication Multiple Circumferential Indication Mixed Mode Indication Tube Sheet Hot Page 3 of 3