ML20128E916
| ML20128E916 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 01/06/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20128E901 | List: |
| References | |
| NUDOCS 9302110143 | |
| Download: ML20128E916 (6) | |
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[go novDo UNITED STATES l' .o NUCLEAR REGULATORY COMMISSION
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e ENCLOSUE SAFETY EVALUATION BY THE OFFICE OF NVCLEAR REACTOR RE@MIlQN OF FIRST TEN-YEAR INSERVICE INSPECTION INTERVAL RE0 VESTS FOR RELIEF TENNESSEE VALLEY AUTHORITY E0V0YAH NOCLEAR PLANT. UNIT 1 DOCKET NUMBER 50-327 1.0 INTRODUCTIO.N Technical Specifications 4.0.5 for Sequoyah Nuclear Plant (SQN), Unit 1, states that inservice inspection and testing of the American Society of Mechanical Engineers (ASME) Code Class 1, 2, and 3 components shall be performed in arrordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicr. ole Addenda as required by 10 CFR 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(1). 10 CFR 50.55a(a)(3) states that alternatives to the requirements, of paragraph (g) may be used, when authorized by the NRC, if the proposed alternatives would provide an acceptable level of quality and(1) safety, or (ii) compliance with the specified requirements would result in hardship or unusual difficulties 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 each ten-year interval 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) on the date twelve months prior to the start of the 120-month inspection interval, subject to the limitations and modifications listed therein. 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.
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 9302110143 930106 DR ADOCK 0500 7
- 2-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)(1), the Comission may grant relief and may impose alternative requirements that are determined to be authorized by law, will not endanger life, property, or the comon defense and security, and are otherwise in tl1e public interest, giving due consideration to the burden upon the licensee that could result if the requirements were imposed. :
By letter dated June 15, 1992, the Tennessee Valley Authority (licensee) submitted to the NRC the First Ten-Year Interval Inservice Inspection (151) pro $ramPlan, Inc uded in the Revisions 17and16forSQN, licensee's submittal, Units 1and2respectivelyIleffrom were assor.iated requests for re the ASME Code Section XI requirements-that the licensee determined to be impractical to perform during the First Ten-Year ISI interval for Sequoyah Nuclear Power Plant, Units 1 and 2. The staff has reviewed and evaluated the requests for relief and supporting information for SQN, Unit 1. The latest revisions to the First Ten-Year Interval ISI Program Plans for Units 1 and 2, and the requests for relief for Unit 2 will be reviewed and evaluated in separate documents at a later date.
2.0 EVALUATION RR 151-15 Surface Examinations on Main Steam System Intearally Welded Succort Attachments Code Reauirement: Table IWC-2500-1 Examination Category C-C, item C3.40 requires surface examinations of piping integra11y' welded support attachments.
Licensee's Code Reouest: The licensee has requested relief from performing Code required surface examinations on weld attachments 1-MSH-303-IA, 1-MSH-343-IA, lHSH-383-IA, and IMSH-423-IA.
Licensee's Basis for Recuestina Relief: The licensee stated it will be impractical to surface examine certain integral attachment welds. Inspection .
of Main Steam System support attachments 1-MSH-303-IA, 1-MSH-343-IA, IMSH-383-IA, and IMSH-423-IA is prohibited for the following reasons:
(1) The. physical location of the supports is very close to the wall.
(2) Disassembly of the supports is prohibited without cutting the support.
(3) The integral attachment welds are obscured behind bars. Therefore, a surface examination is not possible and only a small percentage of the integral attachment weld is accessible for a visual examination.
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1 (4) SQN outage personnel worked five shifts attempting to remove the j support clamp for 1-MSH-303-IA without success. After' removal of '
the clamp bolting, there was not sufficient clearance to remove the brackets that clamp around the pipe due to the building structure and design configuration of the supports.
Licensee's Proposed Alternative Examinationt The Itcensee proposes as an alternative examination, to perform such visual examinations as practical of component supports 1-MSH-303-IA, 1-MSH-343-IA, IMSH-383-!A, and 1HSH-423-IA.
Staff Evaluation: The staff has determined that it would be impractical for the licensee to perform the Code required surface examinations on pining integrally welded support attachments, because the support attachments are inaccessible. Redesign and reconstruction of the supports would be necessary in order to For example, supports are near walls, perform the Code behind bars, required and su) examination.
ports that are disassembled, may have to be cut-up and then reinstalled. Tae licensee has proposed an alternative examination to visually examine as practical the component supports. The licensee's alternative examination will provide an acceptable level of quality and safety, and reasonable assurance that the structural integrity of the plant's systems, components, and supports will be maintained.
RR-ISI-16 Volumetric ExaminJLtion of Circumfer_catial Shell Welds for Residual Heat Removal Heat Exchanaer Code RtmdIrmtall Table IWC-2500-1, Examination Category C-A, item No. C1.10, requires 100% volumetric examinations of circumferential shell welds.
'Licenste's Code Reauest: The licensee has requested relief from performing 100% volumetric examinations of circumferential shell welds for Unit l's Residual Heat Exchangers (two per unit).
Licensee's B& sis for Reauestina Reliell The licensee stated that each heat exchanger consists of an inlet-outlet head chamber with one inlet and ons outlet nozzle, two integrally attached support brackets, and a circumferential vessel shell-to-flange weld. The design configuration of the nozzles and support brackets restricts examination of the vessel-to-flange weld. The vessel shell weld is 133 inches in length. The weld examinations are distributed in three segments. Segment RHRW-16-A-1 (37 inches) was ultrasonically examined in the first inspection period and the licensee achieved approximstely 81 percent examination coverage. Segment RHRW-16-A-2 (28 inches) was examined in the second period and the licensee achieved ;
approximately 71 percent examination volume coverage. Segment RHRW-16-A-3 (38 inches) is scheduled for examination for the third period and the licensee estimated that 82 percent examination volume of the weld could be performed.
The licensee concluded that, based on the examination performed and an 4 estimation of the remaining third period examination, approximately 78 percent examination volume coverage of the RHR heat exchanger circumferential weld will be achieved.
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Licensee's Proyosed Alternative Examination: The licensee proposed in addition, to t.1e visual examination performed during system leakage and hydrostatic pressure tests, a best-effort ultrasonic examination on one '
vessel-to-flange weld on one heat exchanger will be performed to achieve as much Code coverage as possible and achieve meaningful results.
31aff Evaluation: 1he staff determined that it would be impractical for the licensee to )erform the Code required volumetric examinations on the RHR llent Exchangers, )ecause the design of the nozzles and support brackets restricts the examination. The nozzles and brackets would have to be redesigned and reconstructed in order to perform the Code required examinations. The licensee also propoted as an alternative examination to perform a best-effort ultrasonic examin: tion on one vessel-to-flange weld on one heat exchanger and visual examinations during system leakage and hydrostatic pressure tests. The licensee's alternative examination will provide an acceptable level of quality and safety, and reasonable assurance that the structural integrity of the plant's systems, components, and supports will be maintained.
BR-ISI-17 Surface Examination (pLintearally Welded Suonort Attachments Code Reauirement: Table IWC-2500-1, Examination Category C-C, Item No. C3.40, requires surface examinations of piping integrity welded supports attachments.
Licensee's Buis for Reauestino Relief: The licensee stated that, due to the design vintage of SQN, it would be impractical to inspect all of the integrally welded attachments of certain component supports. The integrally welded support attachments may have access limitations as well as nonremovable hanger (pipe clamp) Interference, for example, access is limited to examine component FDR-204-IA of the Feedwater System because of a penetration in the valve room wall, and sup) ort design of snubber stiffener plate prohibits access to integral attac1ments for surface examination and allows only a best effort visual examination.
Licensee's Proposed Alternative Examination: The licensee proposes to perform visual examinations of the component supports as practical.
Staff Evaluation:- The staff determined that it would be impractical for the licensee to perform the Code required surface examinations on integrally welded support attachments, because the attachments have access limitsticr.s and nonremovable hanger (pipe clamp) interference, and would have to be redesigned and reconstructed. The licensee pro)osed as an alternative examination to perform visual examinations of tie component supp wts to the extent practical. The licensee's proposed alternative examination to visually examine the component supports to the extent practical )rovidos an acceptable level of quality and safety, and reasonable assurance t1at thu structural integrity of the plant's systems, components, and supports will be maintained.
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l RR 151-18 Volumetric Examination on Reactor Pressure Vessel Closure Head-tp_- l Ll.AMtAtl.d '
Code Reauirement; Table IWB-2500-1 Examination Category B-A, item No. Bl.40, Volumetric Examination of Reactor Pressure Vessel Closure Head-to-Flange Weld.
Licensee's Code Reougiti The licensee has requested relief from performing a 100 percent volumetric examination on the Reactor Pressure Vessel Closure Head-to-Flange Weld.
Licenet's Basis for Reauestina Relief: The Itcensee stated the Reactor Vessel [RPV) closure head-to-flange weld, WO8-09, is 45 feet in length and that the weld examinations are performed from the OD surface and distributed in three segments of 15 feet lengths each inspection period. The weld segments are identified as: WO8-09A (0" - 180") WOB-098 (180" - 360" and WO8-090 (360" - 540"). Due to the design configuration of the closure),
head, no examinations can be performed from the flange side. Only limited examinations from the ring side are possible due to the head lifting lugs.
WO8-09A was examined by ultrasonics (UT) in the first inspection period and the licensee achieved approximately 40 percent examination volume coverage.
WO8-09B was UT examined in the second inspection period and achieved 40 percent examination volume coverage. WO8-09C is scheduled for examination during the third )eriod with a estimated volume coverage of 40 percent. It should be noted t1at approximately 100 percent of the weld volume was examined from the OD surface from the closure head ring side. However, the required 1/2T base metal area was not completely examined on the flange side, because of the configuration of the reactor closure head. Due to the extreme limited scanning area the licensee will only be able to achieve approximately 40%
examination coverage of the RPV closure head-to-flange weld.
Licensee's proposed Alternative Examination: The licensee proposed as an alternative examination that, in addition to the visual examination performed during system leakage and hydrostatic pressure tests, the licensee will perform a best-effort ultrasonic examination to achieve as much Code coverage as possible and achieve meaningful results. In addition, the licensee will aerform a 100 percent surface examination (Magnetic Particle) of the closure lead-to-flange weld flex area, of all accessible areas, in the third inspection period.
Staff Evaluation: The staff determined from data provided that the Code required volumetric examination of the head-to-flange weld is obstructed by lifting lugs and tapered portion of the flange. The reactor vessel design, therefore, makes the volumetric examination of the welds impractical to perform to the extent required by the Code. In order to examine the velds in accordance with the requirement, the reactor vessel would require extensive design modifications and reconstruction. Imposition of this requirement on the licensee would cause a burden that would not be compensated significantly by an increase in safety above that provided by the limited examination.
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The licensee has stated that the volumetric examination will performed to the maximum extent practical, that a surface examination will be performed, and visual examinations will be performed during system leakage and hydrostatic pressure tests. Based on the design of the reactor pressure vessel, an acceptable percentage of the Code required volume will be examined. Thus, the limited Section XI volumetric examination, along with the surface examination and visual examination, will ptovide adequate assurance that inservice flaws have not developed in the subject reactor vessel welds or that they will be detected and removed or repaired prior to the return of the RPV to service.
3.0 CONCLUSION
Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee determined that conformance with certain Code requirements ss impractical for Unit I and submitted supporting information. The staff has reviewed the licensee's submittal and has concluded that there are cases where relief can be granted as requested.
Pursuant to 10 CfR 50.55a(g)(6)(1), the staff concluded that the requirements of the Code are impractical and relief may be granted for 151-15, 151-16, 151-17, and ISI-18 for Unit 1. Such relief is authorized by law and will not endanger life, property, or the common defense and security, and is otherwise-in the aublic interest. Relief has been granted giving due consideration do to the mrden upon the licensee that could result if the requirements were imposed on the facility, furthermore, the proposed alternative examinations should provide an acceptable level of quality and safety, and reasonable assurance that the structural integrity of the plant's systems, components, and supports will be maintained.
Principal Contributor: T. McLellan Date: January 6. 1993
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