ML20203L815
| ML20203L815 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 02/27/1998 |
| From: | Stanley H COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-97-05, GL-97-5, NUDOCS 9803060249 | |
| Download: ML20203L815 (7) | |
Text
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Commonwealth Fdivin Company 1400 Opus 11.nc IMwners Grose, 11,60515 5-'01 February 27,1998 U.S. Nuclear Regulatory Commission Washington, DC 20555 Attention:
Document Control Desk
Subject:
Braidwood Station Units 1 and 2 Byron Station Units ' and 2 NRC Dockets Numbers 50-456 and 50-457 NRC Dockets Numbers: 50-454 and 50-455 Commonwealth Edison Company (Comed) Response to NRC Generic Letter 97-05, " Steam Generator Tube Inspection Techniques" dated December 17,1997
Reference:
NRC Generic Letter 97-05, " Steam Generator Tube Inspection Techniques" dated December 17,1997 The Referenced letter transmitted the Nuclear ':gulatory Commission (NRC) Generic Letter 97-05, " Steam Generator Tube Inspection Technique." This letter requested a 90 day response which addresses ! caving steam generator tube indications in set
.c based on sizing and the asrociated nondestructive examination method and justification. Attached is the Com nonwealth Edison Company's (Comed) response, if you have any questiou concerning this correspondence, please contact this office.
Sincerely, g
JV l Gene Stanley PWR Vice President i
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Byron Project Manager - NRR Braidwood Project Manager - NRR
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Senior Resident Inspector - Braidwood Senior Resident inspector - Byron Regional Administrator-RIII Office of Nuclear Safety-IDNS 9803060249 980227 hlhlhlk'afh~ llfll]ff PDR ADOCK 05000454 P
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References:
(1)
EPRI PWR Steam Generator Examination Guidelines, Revision 4, Volume 1, June 1996 (2)
EPRI PWR Steam Generator Examination Guidelines, Revision 5, Volume 1, September 1997 Introduction This response addresses the required information requested in the U.S. NRC Generic Letter 97-05," Steam Generator Tube Inspection Techniques," dated December 17,1997 for Comed's Byron and Braidwood Stations.
Byron Units 1 and 2 Originally, Byron Unit I contained four Westinghouse Model D-4 recirculating pre-heater steam generators (S/Gs). Each S/G contained 4,578 mill annealed Inconel-600 U-bend tubes. Byron Unit I has replaced the Model C-4 generators with Babcock & Wilcox International (BWI) replacement steam generators (RSGs) during the fall of 1997. Each BWI RSG contains 6,633 thermally treated Inconel-690 U-Bend tubes.
Byron Unit 2 contains four Westinghouse Model D-5 recirculating pre-heater S/Gs. Each S/G cor.tains 4,570 thermally treated Inconel-600 U-bend tubes.
Braidwood Units I and 2 Braidwood Unit I contains four Westinghouse Model D-4 recirculating pre-heater S/Gs-Each S/G contains 4,578 mill annealed Inconel-600 U-bend tubes. Braidwood Unit 1 is scheduled to replace the Model D-4 S/Gs with BWI RSGs in the Fall of 1998.
Braidwood Unit 2 contains four Westinghouse Model D-5 recirculating pre-heater S/Gs.
Each S/G contains 4,570 thermally treated Inconel-600 U-bend tubes.
Required Information item #(1)
Whether it is Comed's practice to leave steam generator tubes with indications in service based on sizing, K: generic \\gl\\9705
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Response
Comed's practice is to allow steam generator tubes with indications to remain in senice based on sizing which i:: qualified per Reference 1. Indications left in service based on si7ing result from: 1) wear and 2) Outside Diameter Stress Corrosion Cracking (ODSCC) at the tube support plates Tube support plate ODSCC indications are left in service by application of a voltage based Interim Plugging Criteria in accordance with the plant Technical Specifications and Generic Letter 95-05. No other tubes with indications of degradation are sized and left in service at Byron or Braidwood.
Required Information item #(2)
If the response to item (1)is amrmative, those licensees should submit a written report that includes, for each type ofindication, a description of the associated nondestructive examination method being used and the technical basis for the acceptability of the technique used.
Response
Comed's practice is to follow the requirements of the EPRI PWR Steam Generator Examination guidelines References (1) and (2). The guidelines provide guidance on the quahtication of S/G tubing examination technique and equipment to detect and size flaws.
These guidelines were transmitted to the Nuclear Regulatory Commission (NRC) by the Nuclear Energy Institute (NEI) Comed has been following the requirements for sizing degradation u-ing EPRI PWR Steam Generntor Examination Guidelines, Revision 4, Volume 1, June 1996 (Reference 1). During the Byron Unit 2 outage beginning in April 1998, Comed will implement the requirements of the EPRI PWR Steam Generator Examination Guidelines, Revision 5, Volume 1, September 1997 Reference 2.
As part of the EPRI Appendix H process, test samples are used to qualify detection and sizing capabilities. While pulled tube samples are preferred, fabricated samples may be used. If fabricated samples are used, the samples are verified to produce signals similar to those being observed in the field in terms of signal characteristics, signal amplitude, and signal-to-noise ratio. The procedures developed in accordance with Appendix H specify the essential variables for each procedure. These essential variables are associated with the individual instrument, probe, cable, or particular on-site equipment configurations.
The Comed, eddy current Level III reviews the Appendix H qualified techniques to assure the qualified techniques are applicable to site-specific conditions K: generic \\gl\\9705
Byron Units I and 2 Response:
The following are summaries of the information requested for the sizing techniques used for Byron Units 1 and 2. More detailed information is provided in References 1 and 2.
3 e Wear Wear indications are left in service based on amplitude depth sizing. Wear is found in all Model D-4 and D-5 S/Gs at Byron Units 1 and 2. Wear is defmed as the volumetric removal of material caused by the mechanical action of one material in contact with another.
The wear indications are located at the Anti-Vibration Bars (AVBs) and may occur at the Tube Support Plates (TSPs) in the pre-heater section.
Wear has the potential to occur in the BWI RSGs. The wear indications are expected to be found at the fan bars and lattice grid supports.
NDE Method The bobbin coil technique is used for the examination, detecuan and sizing of wear at the AVBs and the pre-heater regions of the D-4 and D-5 S/Gs.
This same technique will be used for the examination, detection and sizing at the fan bars and the lattice grid supports of the BW1 RSGs. For wear at the AVBs and TSPs in the pre-heater region, sizing is accomplished using the 300/130 kHz absolute mix. For potential wear at the fan bars and lattice grids, sizing will be accomplished using the 320/160 kHz absolute mix. A calibration curve for amplitude vertical maximum is determined based on the applicable standards replicating the damage mechanism type and quantity. Additional detailed information is contained in References I and 2.
Technical Basis for Acceptability The Reference I requirements were used for the detection and sizing of wear at the AVDs and Bafile Plates in the pre-heater region of the D-4 and D-5 S/Gs The EPRI Appendix il technique used for sizing wear can be found in the Examination Technique Specification Sheet (ETSS) ETSS
- 96004 Wear _b doc. The qualification us performed for tubing sizes of 0.625",0.750" and 0.875" outside diameter tubing by 0.037",0.043" and 0.049" wall thickness EPRI Appendix H techniques will be applied for detection and sizing of wear at the fan bars and lattice grids of the BW1 RSGs.
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The EPRI wear data set used for the qualification consists of fabricated samples. The technique performance results in the detection probability at 2 60% th. rough wall (TW) at a 90% confidence limit with a probability of 0.83. The root-mean-square error (RMSE) sizing is 3.8% TW, The sizing qualification is based on 64 sample data points. The samples ranged in depth from 4% to 78% through wall depth.
. ODSCC ODSCC indications are lefl in service based on application of voltage correlations rather than a classical depth based limit. The voltage correlations are in accordance with Comed's Technical Specification (TS) 3/4. 4.5, " Steam Generators " ODSCC is found in the original model D Unit 1 S/Gs. The ODSCC indications are confined within the tube support plates.
- NDE Method The bobbin coil technique is used for the examination and detection of ODSCC at the tube support plates of the D-4 S/Gs. For ODSCC at the TSPs, detection is accomplished using the 550/130 kHz differential mix.
Additional detailed information is contained in References I and 2.
Technical Basis for Acceptability The Reference 1 requirements were used for the detection of ODSCC at =
the TSPs in the D-4 S/Gs, The EPRI Appendix H technique used for ODSCC detection can be found in the Examination Technique Specification Sheet (ETSS) ETSS #96007 odscctsp. doc. The qualification was performed for tubing sizes of 0.750" and 0.875" outside diameter tubing by 0.043" and 0.049" wall thickness.
The EPRI ODSCC data set used for the qualification of detection consists of tube pulls and fabricated samples. The technique performanc results in tbc detection probability at 60% TW at a 90% confidence limit with a probability of 0.89.
The sizing technique for ODSCC has been specifically reviewed and approved by the NRC as found in Safety Evaluation Report Amendment No. 77 dated November 9,1995 for Byron Station Unit 1.
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Braidwood Units 1 and 2 Response:
The following are s. maries of the information reauested for the sizing techniques used for Braidwood Units 1 and 2. More detailed infornation is provided in Reference I and 2.
. Wear Wear indications are left in senice based on amplitude depth sizing. Wear is found in all Model D-4 and D-5 S/Gs at Braidwood Units 1 and 2. Wear is defmed as the volumetric removal of material caused by the mechanical action of one material in contact with another.
The wear indications are located at the Anti-Vibration Bars (AVBs) and may occur at the Tube Support Plates (TSPs) in the pre-heater section.
. NDE Method The Bobbin coil technique is used for the examination, detection and sizing of wear at the AVBs and the pre-heater regions of the D-4 and D-5 S/Gs.
For wear at the AVBs and TSPs in the pre-heater region, sizing is accomplished using the 300/130 kHz absolute mix. A calibration curve for amplitude vertical maximum is determined based on the applicable standards replicating the damage mechanism type and quantity. Additional detailed information is contained in References I and 2.
Technical Basis for Acceptability The Reference I requirements were used for the detection and sizing of wear at the AVBs and Baffle Plates in the per-heater region of the D-4 and D-5 S/Gs. The EPRI Appendix H technique used for sizing wear can be found in the Examination Technique Specification Sheet (ETSS) ETSS
- 96004 Wear _b doc. The qualification was performed for tubing sizes of 0.625",0.750" and 0.875" outside diameter tubing by 0.037",0.043" and 0.049" wall thickness.
The EPRI wear data set used for the qualification consists of fabricated samples. The technique performance results in the detection probability at 2 60% TW at a 90% confidence limit with a probability of 0.83. The root-mean-square error (RMSE) sizing is 3.8% TW.
The sizing qualification is based on 64 sample data points. The samples ranged in depth from 4% to 78% through wall depth.
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. ODSCC ODSCC indication., are lef1 in service based on application of voltage correlations rather than a classical depth based limit. The voltage correlations are in accordance with Comed's Technical Specification (TS) 3/4. 4.5," Steam Generatocs." ODSCC is found in the model D-4 Unit 1 3
S/Gs. The ODSCC indications are confined within the tube support plates-E e NDE Method l
The bobbin coil technique is used for the examination and detection of ODSCC at the tube support plates of the D-4 S/Gs. For ODSCC at the TSPs, detection is accomplished using the 550/130 kHz ditTerential mix. Additional detailed information is contained in References 1 and 2.
i I
Technical Basis for Acceptability e
The Reference i requirements were used for the detection of ODSCC at g
the TSPs in the D-4 S/Gs. The EPRI Appendix H technique used for
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ODSCC detection can be found in the Examination Technique Specification Sheet (ETSS) ETSS #96007 odscctsp doc. The qualification was performed for tubing sizes of 0.750" and 0.875" outside diameter tubing by 0.043 ' and 0.049" wall thickness.
The EPRI ODSCC data set used for the qualification of detection consists of tube pulls and fabricated samples. The technique performance results in the detection probability at 60% TW at a 90% confidence limit with a pr oability of 0.89.
The sizing technique for ODSCC has been specifically reviewed and approved by the NRC as found in Safety Evaluation Report Amendment No. 69 dated November 9,1995 for Braidwood Station Unit 1.
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