ML020840728
| ML020840728 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 04/05/2002 |
| From: | Richard Laufer NRC/NRR/DLPM/LPD2 |
| To: | Gordon Peterson Duke Energy Corp |
| Patel C P, NRR/DLPM, 415-3025 | |
| References | |
| TAC MB3730 | |
| Download: ML020840728 (7) | |
Text
April 5, 2002 Mr. G. R. Peterson Site Vice President Catawba Nuclear Station Duke Energy Corporation 4800 Concord Road York, South Carolina 29745-9635
SUBJECT:
CATAWBA NUCLEAR STATION, UNIT 1 RE: EVALUATION OF INSERVICE INSPECTION RELIEF REQUEST NO.01-001, REVISION 1, FOR THE SECOND 10-YEAR INSPECTION INTERVAL (TAC NO. MB3730)
Dear Mr. Peterson:
By letter dated November 28, 2001, you submitted Relief Request No.01-001, Revision 1 for the second 10-year inservice inspection (ISI) interval of Catawba Unit 1. The request pertains to relief from the volumetric examination of essentially 100 percent (greater than 90 percent in accordance with Code Case N-460) of the volume as required by the American Society of Mechanical Engineers Code,Section XI, for some Class 1 and 2 welds and nozzle inside radii identified in the relief request. The Code required volumetric examination was deemed impractical due to component configuration which allowed only limited coverage of nozzle inside radii.
The staff has reviewed Relief Request No.01-001, Revision 1, as documented in the enclosed Safety Evaluation. The staff has determined that compliance with the Code requirements for full volumetric examination of the subject welds is impractical and would result in a significant burden. The staff finds that the examination coverage of the accessible weld volumes provides reasonable assurance of structural integrity of the subject welds. Therefore, relief is granted pursuant to 10 CFR 50.55a(g)(6)(i) for the Catawba Nuclear Station, Unit 1, second 10-year ISI interval.
Sincerely,
/RA/
Richard J. Laufer, Acting Chief, Section 1 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-413
Enclosure:
As stated cc w/encl: See next page
Mr. G. R. Peterson April 5, 2002 Site Vice President Catawba Nuclear Station Duke Energy Corporation 4800 Concord Road York, South Carolina 29745-9635
SUBJECT:
CATAWBA NUCLEAR STATION, UNIT 1 RE: EVALUATION OF INSERVICE INSPECTION RELIEF REQUEST NO.01-001, REVISION 1, FOR THE SECOND 10-YEAR INSPECTION INTERVAL (TAC NO. MB3730)
Dear Mr. Peterson:
By letter dated November 28, 2001, you submitted Relief Request No.01-001, Revision 1 for the second 10-year inservice inspection (ISI) interval of Catawba Unit 1. The request pertains to relief from the volumetric examination of essentially 100 percent (greater than 90 percent in accordance with Code Case N-460) of the volume as required by the American Society of Mechanical Engineers Code,Section XI, for some Class 1 and 2 welds and nozzle inside radii identified in the relief request. The Code required volumetric examination was deemed impractical due to component configuration which allowed only limited coverage of nozzle inside radii.
The staff has reviewed Relief Request No.01-001, Revision 1, as documented in the enclosed Safety Evaluation. The staff has determined that compliance with the Code requirements for full volumetric examination of the subject welds is impractical and would result in a significant burden. The staff finds that the examination coverage of the accessible weld volumes provides reasonable assurance of structural integrity of the subject welds. Therefore, relief is granted pursuant to 10 CFR 50.55a(g)(6)(i) for the Catawba Nuclear Station, Unit 1, second 10-year ISI interval.
Sincerely,
/RA/
Richard J. Laufer, Acting Chief, Section 1 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-413
Enclosure:
As stated cc w/encl: See next page DISTRIBUTION:
PUBLIC CPatel ACRS PDII-1 R/F CHawes SRosenberg HBerkow OGC RHaag, RII RLaufer GHill (4)
- See previous concurrence Accession Number: ML020840728
- No major changes to SE OFFICE PDII-1/PM PDII-1/LA OGC**
DE*
PDII-1/(A)SC NAME CPatel CHawes RHoefling TChan RLaufer DATE 4/5/02 4/5/02 4/3/02 2/6/02 4/5/02 OFFICIAL RECORD COPY
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SECOND 10-YEAR INTERVAL INSERVICE INSPECTION PROGRAM REQUEST FOR RELIEF NO.01-001, REVISION 1 DUKE ENERGY CORPORATION CATAWBA NUCLEAR STATION, UNIT 1 DOCKET NO. 50-413
1.0 INTRODUCTION
Inservice inspection (ISI) of the American Society of Mechanical Engineers (ASME) Code Class 1, 2 and 3 components is to be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable addenda as required by Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a(g), except where specific relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). 10 CFR 50.55a(a)(3) states in part that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed alternatives would provide an acceptable level of quality and safety or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2 and 3 components (including supports) shall meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first ten-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) twelve months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable ASME Section XI Code, for Catawba Unit 1 second 10-year ISI interval is the 1989 Edition. The components (including supports) may meet the requirements set forth in subsequent editions and addenda of the ASME Code incorporated by reference in 10 CFR 50.55a(b) subject to the limitations and modifications listed therein and subject to Commission approval.
Pursuant to 10 CFR 50.55a(g)(5), if the licensee determines that conformance with an examination requirement of Section XI of the ASME Code is not practical for its facility, information shall be submitted to the Commission in support of that determination and a request made for relief from the ASME Code requirement. After evaluation of the determination, pursuant to 10 CFR 50.55a(g)(6)(i), the Commission may grant relief and may impose alternative requirements that are determined to be authorized by law, will not endanger life, property, or the common defense and security, and are otherwise in the public interest, giving due consideration to the burden upon the licensee that could result if the requirements were imposed.
By letter dated November 28, 2001, Duke Energy Corporation (the licensee) submitted Relief Request No.01-001, Revision 1 for the second 10-year ISI interval of Catawba Unit 1. The request pertains to relief from the volumetric examination of essentially 100 percent (greater than 90 percent in accordance with Code Case N-460) of the volume as required by the ASME Code,Section XI, for the Class 1 and 2 welds identified in the relief request.
2.0 DISCUSSION System/Components for which Relief is Requested Component ID Number Item Number
- a. Steam Generator 1SGA-INLET B03.140.001 Steam Generator 1SGA-OUTLET B03.140.002
- b. Steam Generator inlet nozzle-to-safe end weld 1SGA-INLET-W5SE B05.070.001 Steam Generator outlet nozzle-to-safe end weld 1SGA-OUTLET-W6SE B05.070.002
- c. Containment Spray Pump 1A-to-Reducer weld C05.011.201 Containment Spray Reducer-to-Flange Weld C05.011.202 Containment Spray Valve 1NS018A-to-Pipe weld C05.011.203
- e. Seal Water Injection Filter 1B Shell-to-Head Weld C01.020.018 Code Requirement ASME Code,Section XI, 1989 Edition, in examination categories B-D (Full Penetration Welds of Nozzles in Vessels), B-F (Pressure Retaining Dissimilar Metal Welds), C-F-1 (Pressure Retaining Welds in Austenitic Stainless Steel or High Alloy Piping), and C-A (Pressure Retaining Welds in Pressure Vessels) require essentially 100 percent volumetric examination coverage of the welds and nozzle inside radii.
Code Case N-460 approved for use by NRC in Regulatory Guide 1.147, allows credit for full volume coverage of welds if it can be shown that greater than 90 percent of the required volume has been examined.
Code Case N-460 Requirement from which Relief is Requested Relief is requested from the requirement to examine greater than 90 percent of the required volume specified in the ASME Code,Section XI, 1989 Edition. Due to existing geometry, configuration and austenitic weld metal, obtaining greater than 90 percent coverage of the required volume as allowed under Code Case N-460, is impractical.
Licensees Basis for Relief Item 2a The ultrasonic examination coverage of the Steam Generator 1A Inlet and Outlet Nozzle inside radius sections was limited to 83.24 percent. The limitation is due to the ratio of the nozzle OD to the vessel thickness. When the nozzle OD is small in relation to the vessel thickness, more coverage can be obtained by scanning from the vessel side. The nozzle inner radius sections were ultrasonically examined to the maximum extent practical from the vessel wall.
Radiography is not practical because of the geometry of the component, which prevents placement of the film and the exposure source.
Item 2b The ultrasonic examination coverage of the Steam Generator 1A Inlet and Outlet Nozzle-to-Safe End butt welds was limited to 75 percent. The limitation is due to the geometry of the component resulting in single sided access for examination and subsequent attenuation of the sound beam in passing through the austenitic weld metal and the stainless buttering layer on the nozzle end. The examination sensitivity is degraded to such an extent that any examination using the second sound path is meaningless. Therefore, the two-beam path direction coverage is impractical. In order to obtain the required two-beam path direction coverage, the weld would have to be re-designed to allow scanning from both sides.
Item 2c The ultrasonic examination coverages of the Containment Spray Pump 1A-to-Reducer weld, Reducer-to-flange weld and the Containment Spray Valve 1NS018A-to-Pipe weld were limited to 60 percent, 59 percent and 58 percent respectively. Each of these welds were scanned from one side only due to geometry of the component and the far side of each weld has austenitic stainless weld metal which attenuates and distorts sound beam when shear waves generated as a result of mode conversion of the refracted longitudinal wave pass through the weld.
Therefore, Duke Energy Corporation does not take credit for coverage of the far side of austenitic stainless weld. In order to achieve code-required coverage, the welds would have to be re-designed to allow scanning from both sides.
Item 2d The ultrasonic examination coverage of the Feedwater Pipe-to-Valve 1CF042 weld was limited to 75 percent of the required examination volume. This is a dissimilar metal weld joining a stainless steel pipe to a carbon steel valve. Access is limited to the pipe side only because of the as-cast surface condition of the valve. The stainless buttering layer on the carbon steel valve and the austenitic weld metal provide highly attenuative barrier to shear wave ultrasound.
The examination sensitivity is degraded to such an extent that any examination using the second sound path is meaningless. Therefore, the two-beam path direction coverage is impractical. In order to obtain the required two-beam path direction coverage, the weld would have to be re-designed to allow scanning from both sides.
Item 2e The ultrasonic examination coverage of the Seal Water Injection Filter 1B Shell-to-Head weld was limited to 59.33 percent of the required examination volume because of limitations to scanning from the vessel head. Single sided access for this austenitic stainless steel weld was available from the shell side only. The austenitic weld metal attenuate and distort the sound beam when shear waves pass through the weld. The weld metal characteristics and the single sided access due to component geometry preclude two-beam path directional coverage of the examination volume. In order to obtain the code-required examination coverage, the weld would have to be re-designed to allow scanning from both sides of the weld over the required examination volume.
Alternate Examinations or Testing No additional examinations are planned for the subject welds during the current interval. The use of radiography as an alternate volumetric examination of the welds/components referenced in this request is not a viable option. Restrictions to performing radiography are primarily due to inability to access the inside of the components to place film or position a radiographic source.
3.0 EVALUATION The staff has evaluated the information provided by the licensee in support of the volumetric examinations of the subject welds performed during the second 10-year ISI interval of Catawba Unit 1. For the subject welds, ultrasonic scanning in the axial direction could be performed from only one side of the weld due to component configuration which prevented scanning from the tapered surface on the other side of the weld. Each weld has a stainless steel component on the far side which could not be scanned from the same side due to the taper on the examination surface. With stainless steel material, the sound beam is markedly attenuated on the far side to detect and size flaws. However, the licensees best-effort examination with single-sided access achieved volumetric coverages of welds ranging from 58 to 83 percent.
Code Case N-460 approved by NRC in Regulatory Guide 1.147 allows credit for full volume coverage if it can be shown that more than 90 percent of the required volume has been examined. The staff, however, has determined that the examination coverage was reduced due to component configuration which restricted scanning from the far side of the weld, allowing only single-sided access. Therefore, it is impractical to meet the Code requirements. In order to meet the Code requirements, the components would have to be redesigned, fabricated, and installed in the systems, which would impose significant burden on the licensee. The results of examination did not identify any rejectable indication. The staff further believes that, if there were any service-induced flaws existing in the welds and/or in the base metal adjacent to the welds, the examination of the accessible weld volume would have at least detected a portion of it with high degree of confidence. Therefore, the staff has determined that the licensees limited examination of the welds provides reasonable assurance of structural integrity of the subject welds.
4.0 CONCLUSION
The staff has reviewed the licensees submittal and has concluded that compliance with the Code requirements are impractical, for full volumetric examination of subject welds, due to limitations caused by the characteristics of austenitic weld metal in conjunction with component configuration. The staff has further determined that if the Code requirements were to be imposed on the licensee, the components must be redesigned which would impose a significant burden on the licensee. The staff finds that the examination coverage of the accessible weld volumes provides reasonable assurance of structural integrity of the subject welds. Therefore, relief is granted pursuant to 10 CFR 50.55a(g)(6)(i) for the second 10-year ISI interval of Catawba Unit 1. The grant of relief is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
Principal Contributor: P. Patnaik Date: April 5, 2002
Catawba Nuclear Station cc:
Mr. Gary Gilbert Regulatory Compliance Manager Duke Energy Corporation 4800 Concord Road York, South Carolina 29745 Ms. Lisa F. Vaughn Legal Department (PB05E)
Duke Energy Corporation 422 South Church Street Charlotte, North Carolina 28201-1006 Anne Cottingham, Esquire Winston and Strawn 1400 L Street, NW Washington, DC 20005 North Carolina Municipal Power Agency Number 1 1427 Meadowwood Boulevard P. O. Box 29513 Raleigh, North Carolina 27626 County Manager of York County York County Courthouse York, South Carolina 29745 Piedmont Municipal Power Agency 121 Village Drive Greer, South Carolina 29651 Ms. Karen E. Long Assistant Attorney General North Carolina Department of Justice P. O. Box 629 Raleigh, North Carolina 27602 Elaine Wathen, Lead REP Planner Division of Emergency Management 116 West Jones Street Raleigh, North Carolina 27603-1335 North Carolina Electric Membership Corporation P. O. Box 27306 Raleigh, North Carolina 27611 Senior Resident Inspector U.S. Nuclear Regulatory Commission 4830 Concord Road York, South Carolina 29745 Virgil R. Autry, Director Division of Radioactive Waste Management Bureau of Land and Waste Management Department of Health and Environmental Control 2600 Bull Street Columbia, South Carolina 29201-1708 Mr. C. Jeffrey Thomas Manager - Nuclear Regulatory Licensing Duke Energy Corporation 526 South Church Street Charlotte, North Carolina 28201-1006 Saluda River Electric P. O. Box 929 Laurens, South Carolina 29360 Mr. Peter R. Harden, IV VP-Customer Relations and Sales Westinghouse Electric Company 6000 Fairview Road 12th Floor Charlotte, North Carolina 28210
Catawba Nuclear Station cc:
Mr. T. Richard Puryear Owners Group (NCEMC)
Duke Energy Corporation 4800 Concord Road York, South Carolina 29745 Richard M. Fry, Director Division of Radiation Protection North Carolina Department of Environment, Health, and Natural Resources 3825 Barrett Drive Raleigh, North Carolina 27609-7721