ML060100448
| ML060100448 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 01/20/2006 |
| From: | Marinos E Plant Licensing Branch III-2 |
| To: | Archie J South Carolina Electric & Gas Co |
| Martin R, DLPM, 301-415-1493 | |
| References | |
| RR-II-09, RR-II-10, RR-II-12, TAC MC5750 | |
| Download: ML060100448 (11) | |
Text
January 20, 2006 Mr. Jeffery B. Archie Vice President, Nuclear Operations South Carolina Electric & Gas Company Virgil C. Summer Nuclear Station Post Office Box 88 Jenkinsville, South Carolina 29065
SUBJECT:
VIRGIL C. SUMMER NUCLEAR STATION - SECOND 10-YEAR INSERVICE INSPECTION, REQUEST FOR RELIEF RR-II-9, RR-II-10, AND RR-II-12 (TAC NO. MC5750)
Dear Mr. Archie:
By a letter dated September 16, 2003, as supplemented October 23, 2003, June 22, 2003, and August 31, 2005, South Carolina Electric & Gas Company (the licensee) submitted Relief Request (RR)-II-9, RR-II-10, RR-II-11, and RR-II-12 for Virgil C. Summer Nuclear Station (VCSNS). By letter dated October 23, 2003, the licensee withdrew RR-II-11. The requests pertain to certain requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code for inservice inspection at the VCSNS. The request for relief is for the second 10-year inservice inspection interval which ends December 31, 2003. The enclosed safety evaluation includes the technical review for RR-II-9, RR-II-10, and RR-II-12.
The Nuclear Regulatory Commissions staff authorizes the proposed alternatives in RR-II-9, and RR-II-10 for the second 10-year inservice inspection interval of VCSNS, pursuant to Title 10, Code of Federal Regulations (10 CFR), Section, 50.55a(g)(6)(i) on the basis that performance would result in a significant burden and the proposed alternative would provide reasonable assurance of integrity. RR-II-12 is granted pursuant to 10 CFR 50.55a(a)(3)(i), on the basis that the alternatives provide an acceptable level of quality and safety.
Sincerely,
/RA/
Evangelos C. Marinos, Chief Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-395
Enclosure:
Safety Evaluation cc w/encl: See next page
ML060100448 NRR-028 OFFICE LPL2-1/PM LPL2-1/LA OGC LPL2-1/ BC NAME RMartin RSola JBonanno EMarinos DATE 1/17/06 1/17/06 1/19/06 1/20/06 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SECOND 10-YEAR INTERVAL INSERVICE INSPECTION REQUEST FOR RELIEF RR-II-9, RR-II-10, AND RR-II-12 VIRGIL C. SUMMER NUCLEAR STATION SOUTH CAROLINA ELECTRIC AND GAS COMPANY DOCKET NUMBER 50-395
1.0 INTRODUCTION
By letter dated September 16, 2003, as supplemented October 23, 2003, June 22, and August 31, 2005, South Carolina Electric & Gas Company, the licensee, submitted relief request Nos. RR-II-9 through RR-II-12 requesting relief from certain American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (Code) inservice inspection (ISI) requirements for the Virgil C. Summer Nuclear Station (VCSNS). Specifically, the licensee requested relief from selected weld inspection coverage requirements. By letter dated October 23, 2003, the licensee withdrew RR-ll-11. The second 10-year ISI interval began December 30, 1993, and ended December 31, 2003.
2.0 REGULATORY EVALUATION
The inservice inspection of the ASME Code Class 1, Class 2, and Class 3 components is to be performed in accordance with Section XI of the ASME Code, "Rules for Inservice Inspection (ISI) of Nuclear Power Plant Components," and applicable edition and addenda as required by Title 10 of the Code of Federal Regulations (10 CFR), Section 50.55a(g), except where specific written 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 Nuclear Regulatory Commission (NRC), if the licensee demonstrates that: (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, 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 10-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) 12 months prior to the start of the 120-month interval, subject
to the limitations and modifications listed therein. The Code of Record for VCSNS for the second 10-year ISI interval is the 1989 Edition of Section XI of the ASME Boiler and Pressure Vessel Code, with no addenda. 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.
3.0 TECHNICAL EVALUATION
OF REQUEST NO. RR-II-9 3.1 Components For Which Relief Is Requested The components affected by this request for relief are taken from the licensees letter dated September 16, 2003. The table below shows the component weld identification, examination categories, coverages, and limitations from examinations performed during Refueling Outage 14.
Weld Identification Category Item No. Coverage Material Limitations CGE-1-4100-29 B-J B9.11 83% Stainless Stl. 29" ID, Elbow to Taper Safe End CGE-1-4100-30 B-J B9.11 83% Stainless Stl. 31" ID, Elbow to Taper Safe End CGE-1-4100-31DM B-F B5.70 25% Ferritic to 29" ID, Nozzle Contour, Stainless Stl. Safe End Taper CGE-1-4100-32DM B-F B5.70 25% Ferritic to 31" ID, Nozzle Contour, Stainless Stl. Safe End Taper CGE-1-4102-7 B-J B9.11 50% Stainless Stl. 12" Pipe to Valve Contour, One Sided Exam.
CGE-1-4200-23BC B-J B9.31 81% Stainless Stl. 6" Branch Nozzle Contour CGE-1-4200-26 B-J B9.11 83% Stainless Stl. 29" ID, Elbow to Taper Safe End CGE-1-4200-27 B-J B9.11 83% Stainless Stl. 31" ID, Elbow to Taper Safe End CGE-1-4200-28DM B-F B5.70 25% Ferritic to 29" ID, Nozzle Contour, Stainless Stl. Safe End Taper CGE-1-4200-29DM B-F B5.70 25% Ferritic to 31" ID, Nozzle Contour, Stainless Stl. Safe End Taper CGE-1-4300-27 B-J B9.11 83% Stainless Stl. 29" ID, Elbow to Taper Safe End
Weld Identification Category Item No. Coverage Material Limitations CGE-1-4300-28 B-J B9.11 83% Stainless Stl. 31" ID, Elbow to Taper Safe End CGE-1-4300-29DM B-F B5.70 25% Ferritic to 29" ID, Nozzle Contour, Stainless Stl. Safe End Taper CGE-1-4300-30DM B-F B5.70 25% Ferritic to 31" ID, Nozzle Contour, Stainless Stl. Safe End Taper CGE-1-4502-13 B-J B9.11 50% Stainless Stl. 6" Pipe to Tee Contour, One Sided Exam.
CGE-1-4503-46DM B-F B5.40 90.4% Ferritic to 6" Pressurizer Nozzle Stainless Stl. Contour CGE-2-2554-5 C-F-1 C5.11 88% Stainless Stl. 10" Elbow to Pipe CGE-2-3010-15 C-F11 C5.21 82% Stainless Stl. Elbow to Valve, One Sided Examination CGE-2-3011-34 C-F-1 C5.21 81% Stainless Stl. Elbow to Tee, One Sided Examination The licensee performed the examinations in Table 1 with Section XI, Appendix VIII performance-based qualified procedures and personnel. The procedures are only qualified for examination from the near side of the weld. To achieve complete coverage, the licensee would have to examine the weld from both sides which is impractical because of the limitations. The coverage obtained using Appendix VIII qualified procedures is less than the coverage achieved during the first ISI interval. The coverage identified as a best effort is the volume interrogated on the far side of the weld. The sum of coverage plus best effort coverage is the same as the coverage achieved in the first ISI interval.
3.2 Code Requirements The 1989 Edition of Section XI of the ASME Code, Table IWB-2500-1 for Examination Categories B-F and B-J and IWC-2500-1 for Examination Categories C-F-1 and C-F-2 is applicable. Each weld is required to be inspected essentially 100 percent of the required volume. ASME Code Case N-460 permits a reduction in coverage of not less than 10 percent.
Pursuant to 10 CFR 50.55a(b)(2)(xv)(A)(1) and 10 CFR 50.55a(b)(2)(xv)(A)(2), piping must be examined in two axial directions, and when examination in the circumferential direction is required, the circumferential examination must be performed in two directions, provided access is available. Where examination from both sides is not possible on austenitic welds or dissimilar metal welds, full coverage credit from a single side may be claimed only after completing a successful single-sided Appendix VIII demonstration using flaws on the opposite side of the weld.
3.3 Proposed Alternative
The licensee proposed alternative is to examine the Code-required weld volume and base metal areas to the extent practical.
3.4 Licensee Basis For The Alternative The licensee is required to perform inspections of the components according to the 1989 Edition of Section XI of the ASME Code. The general design of the component surfaces may have ultrasonic testing (UT) interference caused by inherent manufacturing geometry or obstructions that preclude access to the weld area. Examples of these piping configurations are valve bodies, pipe fitting transitions, nozzle radius transitions, nozzle reinforcing pads and non-bolted obstructions. Each selected weld shall be examined to the maximum extent practical to include the use of multiple angles and beam paths.
3.5 Staff Evaluation The Code requires essentially 100 percent volumetric examination coverage of the length of the subject welds. Code Case N-460 recognizes examination coverage greater than 90 percent as being essentially 100 percent. For UT, the examination coverage is the mathematical sum of scanning directions and inspection volume. Title 10 CFR 50.55a(b)(2)(xv)(A) specifies that if access is available, the weld shall be scanned in each of the four directions (parallel and perpendicular to the weld on each side of the weld centerline). Coverage credit may be taken for single-side exams on austenitic piping if a procedure is qualified with flaws on the inaccessible side of the weld. This procedure must demonstrate single-side access examination equivalency to "two-sided" examinations.
As shown in Table 1, complete two-sided examinations are restricted by several factors, including the geometric configuration of the welds, nozzle and valve contour extending away from the welds, and weld surface roughness. The welds are accessible from at least one side.
Current technology is not capable of reliably detecting or sizing flaws on the inaccessible side of an austenitic weld for configurations common to U.S. nuclear applications. Instead of a full single-side qualification, Performance Demonstration Initiative (PDI) offers a best-effort approach, which demonstrates that the best available technology is applied. PDI Performance Demonstration Qualification Summary (PDQS) for austenitic piping lists the limitation that single side examination is performed on a best effort basis. The PDQS conditional statement requires the inaccessible side of the weld to be listed as an area of no coverage. The examination is performed to the maximum extent permitted by the restrictions.
In order to examine the subject welds according to Code requirements, the licensee would have to replace the subject valves, nozzles, flanges, pipe-tees, elbows, and branch connections.
Replacing all these components would create an unnecessary burden on the licensee.
From the information provided by the licensee, the NRC staff determined that the subject welds were examined using the best available techniques, equipment and personnel as qualified through the PDI for ASME Section XI, Appendix VIII. If significant degradation is present, degradation should be detected during an UT examination, providing reasonable assurance of the continued structural integrity of the subject welds.
3.6 Conclusion
Based on the above evaluation, the NRC staff concludes that the Code-required 100-percent volumetric examinations are impractical for the welds in Table 1. Pursuant to 10 CFR 50.55a(g)(6)(i), the NRC staff grants relief for the second 10-year ISI interval. The NRC staff has determined that the grant of relief for limited examination coverage for the welds identified in Table 1 is authorized by law and will not endanger life or property, or the common defense and security and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in this review remain applicable, including third party review by the Authorized Nuclear Inservice Inspector (ANII).
4.0 TECHNICAL EVALUATION
OF REQUEST NO. RR-II-10 4.1 Components For Which Relief Is Requested The components affected by this request for relief are taken from the licensees letter dated September 16, 2003. The table below shows the component weld identification, examination categories, coverages, and limitations from examinations performed during Refueling Outage 14.
Weld Identification Category Item Coverage Material Limitation Number CGE-2-1110-1B-1 C-A C1.10 83% Stainless Nozzle Reinforcing Pad Steel CGE-2-1110-1B-2 C-A C1.20 83% Stainless Nozzle Reinforcing Pad Steel 4.2 Code Requirements The 1989 Edition of Section XI of the ASME Code, Table IWC-2500-1 for Examination Category C-A is applicable. Each weld is required to be inspected essentially 100 percent of the required volume. ASME Code Case N-460 permits a reduction in coverage of not less than 10 percent.
4.3 Proposed Alternative The licensee proposed alternative is to examine the Code-required weld volume and base metal areas to the extent practical.
4.4 Licensee Basis For The Alternative The licensee is required to perform component inspection in accordance with the 1989 Edition of Section XI of the ASME Code. The general design of the component surfaces may result in ultrasonic scan interference caused by inherent manufacturing geometry or obstructions that preclude access to the weld area. Examples of these vessel configurations are nozzle reinforcing pad interferences, vessel head transitions, nozzle radius transitions, and non-bolted obstructions.
4.5 NRC Staff Evaluation The Code requires essentially 100 percent volumetric examination coverage of the accessible length of the subject welds. Code Case N-460 recognizes examination coverage greater than 90 percent as being essentially 100 percent. Limitations to volumetric coverage were caused by the proximity of reinforcing saddle plate welds on the surface of the vessel and the vessel welds requiring inspection. To achieve the Code-required coverage, the reinforcing saddle plates would have to be redesigned and installed further from the vessel welds which would create a significant burden on the licensee; therefore, the Code-required 100-percent volumetric examinations of the subject welds are impractical.
Drawings and descriptions included in the licensees submittal clearly show that examinations of the subject welds have been performed to the extent practical, with the licensee obtaining substantial volumetric (83 percent) coverages for the two weld in Table 2. The examinations were performed according to the 1989 Edition of Section XI, Appendix III. There were no recordable indications. Any significant patterns of degradation would have been detected by the examinations performed, thus providing reasonable assurance of continued structural integrity of the subject vessel welds.
4.6 Conclusion Based on the above evaluation, the NRC staff concludes that the Code-required 100-percent volumetric examinations are impractical for the welds in Table 2. Pursuant to 10 CFR 50.55a(g)(6)(i), the NRC staff grants relief for the second 10-year ISI interval. The NRC staff has determined that the grant of relief for limited examination coverage for the welds identified in Table 2 is authorized by law and will not endanger life or property, or the common defense and security and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in this review remain applicable, including third party review by the ANII.
5.0 TECHNICAL EVALUATION
OF REQUEST NO. RR-II-12 5.1 Components For Which Relief Is Requested ASME Code Class 1 bolting requiring examination.
5.2 Code Requirements The 1989 Edition of Section XI of the ASME Code, Table IWB-2500-1 for Examination Category B-G-1 requires ASME Class 1 bolting to be ultrasonic, surface and/or visually inspected each interval.
Table IWB-2500-1, Item B6.20, Reactor Vessel Closure Studs, in Place; Item B6.30, Reactor Vessel Closure Studs, when Removed; and Item B6.180, Pump Bolts and Studs, examination volume as defined by Figure IWB-2500-12 is applicable.
5.3 Proposed Alternative
The licensee proposed the application of ASME Code Case N-307-3 for the reduced examination volume and performance of a VT-1 examination in lieu of the surface examination.
5.4 Licensee Basis For The Alternative In Code Case N-307-3, the required surface examination of the Category B-G-1 bolting can be replaced by a VT-1 examination. The cleaning of the threaded surfaces is labor intensive and creates substantial radioactive waste materials. Performance of the alternative VT-1 examination will reduce the radioactive waste generated during the cleaning process without reducing the level of quality or safety of the component. Code Case N-307-3 also reduces the required inspection volume to the higher stressed areas of the bolting. The requirements of ASME Section XI, Appendix VIII, will be implemented through qualified personnel, procedures, and equipment systems via the PDI program.
5.5 NRC Staff Evaluation Code Case N-307-3 reduces the examination volume to that of a volumetric cylinder 1/4" deep from the root of the threads. The root of the threads are stress risers and preferred sites for crack initiation. Cracks at the root of the threads would be perpendicular to straight beam UT performed from the stud ends, and the cracks would create a corner trap for angle beam UT examinations performed from a center hole in the stud. The capabilities of a UT examination finding cracks in a stud is demonstrated through procedure and personnel qualifications. These are performance-based qualifications according to the requirements of Section XI, Appendix VIII, Supplement 8.
Code Case N-307-3 eliminates surface examination of the RPV closure stud when removed.
The function of UT examination is to find cracks in the stud volume. These cracks, if they exist, initiate from the surface. The function of the surface examination is to find cracks on the surface.
Performing both volumetric and surface examinations on a stud duplicates the intent of the examinations which is to find cracks. Of the two nondestructive examination methods, surface examinations are tedious and subjective, and performance-based UT provides demonstrated assurances for finding cracks. Therefore, elimination of the surface examination does not diminish the effectiveness in detecting cracks.
Code Case N-307-3 was developed through a consensus process. The NRC, through its normal participation in the ASME committee process, participated in this process through which it expressed the NRC staffs opinion and support. The NRC staff has reviewed Code Case N-307-3 and has approved it without conditions in Revision 14 of Regulatory Guide 1.147, Inservice Inspection Code Case Acceptability,Section XI, Division 1.
5.6 Conclusion Based on the above information, the NRC staff has concluded that the proposed alternative to apply Code Cast N-307-3 (RR-ll-12) to reduce the ultrasonic testing volume, and eliminate the
surface examination will provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the proposed alternative (RR-ll-12) is authorized for the second 10-year ISI interval.
All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in this review remain applicable, including third party review by the ANII.
Principal Contributor: Donald Naujock Date: January 20, 2006 Mr. Jeffrey B. Archie VIRGIL C. SUMMER NUCLEAR STATION South Carolina Electric & Gas Company cc:
Mr. R. J. White Nuclear Coordinator
S.C. Public Service Authority c/o Virgil C. Summer Nuclear Station Post Office Box 88, Mail Code 802 Jenkinsville, South Carolina 29065 Resident Inspector/Summer NPS c/o U.S. Nuclear Regulatory Commission 576 Stairway Road Jenkinsville, South Carolina 29065 Chairman, Fairfield County Council Drawer 60 Winnsboro, South Carolina 29180 Mr. Henry Porter, Assistant Director Division of Waste Management Bureau of Land & Waste Management Dept. of Health & Environmental Control 2600 Bull Street Columbia, South Carolina 29201 Mr. Thomas D. Gatlin, General Manager Nuclear Plant Operations South Carolina Electric & Gas Company Virgil C. Summer Nuclear Station Post Office Box 88, Mail Code 300 Jenkinsville, South Carolina 29065 Mr. Robert G. Sweet, Manager Nuclear Licensing South Carolina Electric & Gas Company Virgil C. Summer Nuclear Station Post Office Box 88, Mail Code 830 Jenkinsville, South Carolina 29065 Ms. Kathryn M. Sutton Morgan, Lewis & Bockius LLP 111 Pennsylvania Avenue, NW.
Washington, DC 20004