ML20203B107
| ML20203B107 | |
| Person / Time | |
|---|---|
| Site: | McGuire  |
| Issue date: | 02/04/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20203B054 | List: |
| References | |
| NUDOCS 9802240207 | |
| Download: ML20203B107 (7) | |
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p-UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. seseMooi
- e.
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION OF THE SECOND 13-YEAR INTERVAL INSERVICE INSPECTION PLAN PROPOSED ALTERNATIVE TO REACTOR VESSEL AUGMENTED EXAMINATION DUKE ENERGY CORPORATION MCGUIRE NUCI FAR STATION. UNIT 1 3
DOCKET NO. 50-369 i-
1.0 INTRODUCTION
The Technical Specifications for McGuire Nuclear Station, Unit 1, state that the inservice inspection and testing of the American Society of Mechanical Engineers (ASME) Code Class 1,2, and 3 components shall be performed in accordance with Section XI of the ASME Boller and Pressure Vessel Code (ASME Code) and applicable addenda as required by Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g), except where specific wrlhen relief has i-been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). Section 50.55a(a)(3)
. states that attematives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed attematives would provide an acceptable level of quality and safety, or (ii) compliance with the specified requirements would result in hardship or unusual difficulty c
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 cnd access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, " Rules for t
-inservice Inspection of Nuclear Power Plant Components," to the extent practical within the
. limitations o' design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests j
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) on the date 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable edition of the 4
f ASME Code,Section XI, for McGuire Nuclear Station, Unit 1, during the second 10-year 4
inservice inspection (ISI) interval, is the 1986 Edition. The components (including supports) may med 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.
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Enclosure 9802240207 980204 PDR ADOCK 05000369
-C P
2-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 altomative 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 3
imposed on the facility.
Pursuant to 10 CFR 50.55a(g)(6)(li)(A), the Commission revoked all previous reliefs granted to r
licensees for the extent of volumetric examinations of reactor vessel shell welds, as specifed in Section XI, Division 1 of the ASME Code. The Commission further required that alllicensees augment their reactor vessel examination by implementing once, as part of the inservice -
inspection intervalin effeca en September 8,1992, the item B1.10 requirementa (examine essentially 100% of the volume of each shell weld) of the 1989 Edition of the ASME Code.
Under 10 CFR 50.55a(g)(6)(ii)(A)(4), licensees may satisfy the augmented requirements by performing the ASME Section XI reactor vessel shell weld examinations scheduled for implementation during inservice inspection intervals in effect on September 8,19D As a result, the licensee is required to submit both an attemative to 10 CFR 50,55a(g)(64)(A) and a f
request for relief in accordance with 10 CFR 50.55a(g)(5)(iii), or a proposed attemative in accordance with 10 CFR 50.55a(3), for the same welds when the licensee obtains less than the required coverage (essentially 100%) during the examinations.
Additionally, pursuant to 10 CFR 50.55a(g)(6)(ii)(A)(5), licensees that make a determination that 4
they are unable to completely satisfy the requirements for the augmented reactor vessel shell
- weld examination specified in 10 CFR 50.55a(g)(6)(ii)(A) shall submit information to the Commission to support the determination and shall propose an attemative to the examination requirements that would provide an acceptable level of quality and safety. The licensee may use the proposed attemative when authorized by the Director of the Office of Nuclear Reactor Regulation. '
l In a letter dated July 10,1997, Duke Energy Corporation, submitted to the NRC its attematives to the augmented examination of the reactor vessel shell welds conducted pursuant to 10 CFR 50.55a(g)(6)(ii)(A) fnr McGuire Unit 1 during the second 10-year interval, The licei,r,ee's proposed attemative to the examination of " essentially 100%" of seven welds in the reactor
- vessel is a best effort examination resulting in limited examination coverage of the welds that provide an acceptable level of quality and safety. The NRC staff has reviewed and evaluated the licensee's proposed alternative and the supporting information, pursuant to 10 CFR 50.55a(g)(6)(ii)(A)(5) for McGuire Unit 1.
. 2.0 DISCUSSION Component identification:
Code Class:
ASME Code,Section XI, Class 1
Reference:
Table IWB-2500-1 Examination Category:
B-A ltem Numbers:
B1,11 and B1.12
==
Description:==
Limited volumetric examination of the following reactor pressure vessel shellwelds Weld Numbers item Numbers 1RPV10-442 B01.011.003 1RPV1-442A B01.012.001 1RPV1-442B B01.012.002 1RPV1-442C B01.012.003 1RPV3-442A B01.012.007 1RPV3-442B B01.012.008 1RPV3-442C B01.012.009 Examination Recuirement:
Section 50.55a(g)(6)(ii)(A)(2) states that all licensees shall augment their reactor vessel examinations by implementing the examination requirements for reactor pressure vessel (RPV) shell welds specified in item B1.10 of Examination Category B-A, " Pressure Retaining Welds in Reactor Vessel,"in Table IWB 2500-1 of Subsection (WB of the 1989 Edition of Section XI, Division I, of the ASME Code, subject to the conditions specified in 10CFR 50.55a (g)(6)(li)(A)(3) and (4). For the purpose of this augmented examination, essentially 100% as used in Table IWB-2500-1 means more than 90% of the examination volume for each weld.
Additionally,10 CFR 50.55a(g)(6)(ii)(A)(5) requires licensees that are unable to completely satisfy the augmented RPV shell weld examination requirement to submit information to the Commission to support the determination, and propose an alternative to the examination requirements that would provide an acceptable level of quality and safety.
Licnosee's Basis for Reauestina Altemative: (As stated) (of the licensee's submittal] provides the calculations documenting the actual amount of Code required examination coverage obtained. A combinatien of multiple angles and ultrasonic techniques was used to obtain the maximum coverage possible. The use of an attemate transducer head provided increased coverage through optimum transducer arrangement for scanning close to obstructions. However, during the ultrasonic examination of the welds referenced below and listed in Attachment 1 of this alternative, the greater than 90% coverage required per 10 CFR 50.55a(g)(6)(ii)(A)(2) could not be obtained due to geometry and actual physical barriers.
4 EtEtor Vessel Lower Shell to Bottom Head _ Weld (1RPV10-442) (Item Number R01.011.003):
This examination was limited to 59.00% aggregste coverage of the required weld volume. The principal limitation for this weld is six core guide lugs welded to the vessel ID just above the weld on the lower shell section, whose presence restricts the scanning surface irnhat area and limits the examination coverage. These lugs are approximately 19 inches tall,27 inches wide and extend B inches radially toward the center of the vessel, the lugs are positioned 60 degrees around the vessel circumference. These dimensions include the attachment weld rr.dius which physically limited the contact transducer head 1
travel during examination.
Engior Vessel Uoner Shell Lona Stsim Wold at 60 Dearee (1RPV1-442A) (Item Number B01.012.001);
l This examination was limited to 90.00% aggregate coverage of the required weld volume. The principallimitation for this weld involves nozzle interference which divides the weld into two parts. The Reactor Vessel Nonle configuration prevents examination of the weld at the intersection of the weld and nonie. The specific limitations are idantified on drawing 1213926D.
i l
Reactor ye1331Uooer Shell Lona Seam Weld at 180 Dearee (1RPV1 442B) fltem Numbefj01.012.002):
This examination was limited to 31.00% aggregate coverage of the required weld volume. The principal limitation for this weld is the location of the long seam weld j
between the two outlet nonles. The close proximity of the long seam weld to the outlet nonles physically limits examination of the weld in the area between the nonles. The specific limitations are identified on drawing 1213926D.
Reactor Vessel Uooer Shell Lona Seam Weld at _300 Dearee (1RPV1-442C)
([ tem Number B01.012.003):
This examination was limited to 90.00S aggregate coverage of the required weld volume. The princ: pal limitation for this weld involves nonle interference which divides the weld into two parts. The Reactor Vessel inlet Nonle configuration prevents examination of the weld at the intersection of the weld and nonie. The specific limitations are identified on drawing 1213926D.
5 Reactor Vessel Lower Shell Long Seam Weld at 60 Degree (1RPV3-442A) (Item Number B01.012.007):
This examination was limited to 84.00% aggregate coverage of the required weld volume. The principallimitation for this weld is the presence of the core guide lugs welded to the vesselID ebove weld 10-442 on the lower shell section. These lugs are approximately 19 inches tall,27 Ir..hes wide, extend 8 inches radially towarri the center of the vessel, and are positioned every 60 degrees around the vesse!
l circumference. The dimensions include the attachment weld radius. Because of l
their location, the lugs interfered with the axial cnd circumferential weld scans.
Reactor Vessel Lower Shell Lona Seam Weld at 180 Dearee (1RPV3-442B) (Item Number B01.012.00E This examinction was limited to 84.00% aggregate coverage of the regulred weld l
volume. The principallimitation for this weld is the presence of the core guide lugs welded to the vesselID above weld 10-442 on the lower shell section. These lugs i
are approximately 19 inches tall,27 inches wide, and extend 8 inches radially toward the center of the vessel, end are positioned every 60 degrees around the l
vessel circumference. The dimensions include the attachment weld radius, because of their location these lugs interfered with the axial and circu nferent!al weld scans.
Regior Vessel Lower Shell Long Seam Weld at 300 Dearee (1RPV3-442C) (ltem Munber B01.012.009):
l This examination was limited to 84.00% eggregate coverage of the required weld volume. The principal limitation for this weld is the presence of the core guide lugs welded to the vessel ID above weld 3-442 on the lower shall section. These lugs are approximately 19 inches tall,27 inches wide, and extend 8 inches radially toward the center of the vessel, and are positioned every 60 degrees around the vessel circumference. The dimensions include the attachment weld radius, because of their location these lugs interfered with the axial and cir::umferential weld scans.
Licensee's Procosed Attemnlive: (As stated)
In addition to the volumetric examination that has been performed on the McGuire reactor vessel, Duke Energy has performed a visual examination of the internals and the inside of the reactor vessel as required by ASME Section XI, Table IWB 25001. This visual examination dia not identify any rejectable conditions per ASME Section XI acceptance standerds.
6 The use of radiography as an alternate volumetric examination method is not feasible due to component thickness and restrictions from physical barriers which prohibit access for the placement of source, image quality indicators, film, etc. In addition, the background radiation levels would not allow for a radiographic examination that would render meaningful results.
Performing the ultrasonic examination from the outsic -
se reactor vesselis not a viable option. The design of McGuire's reactor buildn; prohibits access for the equipment and personnel from outside the vessel.
Duke Energy Corporation will continue to perform ultrasonic examinations of all reactor vessel welds to the max! mum extent practical in accordance with the requirements of ASME Section V, Article 4,1989 Edition and Regulatory Guide 1.150, Revision 1, Appendix A. The application of Code Case N 400 will be utilized in all cases where less than 100% but greater than 90% wcid coverage is obtalned. In cases where w31d coverage of 90% or less is obtained, a request for relief from ACME Section XI Code requirements will be submitted.
Duke Energy Corporation proposes as an alternative to the greater than 90%
coverage requirement of 10 CFR 50.55a(g)(6)(li)(A), that it,o examination coverage obtained on the welds listed in Attachment 1 be considered to provide an acceptable level of quality and safety.
3.0 EVALUATION To comply with the augmented reactor vessel exam! nation requirements of 10 CFR 50.55a(g)(6)(ii)(A), licensees must volumetrically examine essentially 100% of each of the item 31.10 shell welds. In accordance with the reountions, essentially 100% is defined as greater than 90% of the examination volume of each weld As an attemative to the greater than 90% coverage requirement of the regulations, the licensee proposes that the examination coverage obtained be considered to provide an acceptable level of quality and safety for the RPV welds.
At McGuire Unit 1, the augmented coverage requirements cannot be met for the above referenced shell welds due to physical restrictions or nozzle geometric configura' ion that limit scan coverage. There are six core guide iugs in the lower shell of th J vessel that limits scanning of the lower shell to the bottom head nid to 59% and three longitudinal seams in the lower shell to 84% of the respective examination volume, in the upper shell of the vessel, due to the proximity of the nozzles to the longitudir al welds, one weld is restricted to 31% and two are restricted to 90% of their examination volunie. Ti,3 remaining longitudinal welds in the intermediate shell received the Code examination coverage. To achieve complete coverage for the subject 'Nelds, design modifications would be required to increase access from the inside surface (10).
[
7 As a result of the augmented volumetric examination rule, licensees must make a reasonable
{
effort to maximize examination coverage of their reactor vessels. In cases where examination I
coverage from the ID is inadequate, examination from the outside surface (OD) using manual inspection techniques is a potential option. However, at McGuire Unit 1, the design of the reactor building prevents access for equipment and personnel from the OD. The licensee han attempted to maximize coverage from the inside surface by optimizing transducer l
arrangements for scanning close to obstructions; therefore, it is concluded that the licensee has made a reasonable effort to maximize examination coverage.
With the exception of the lower shell to the bottom head weld and one longitudinal weld in the proximity of the nozzles, the licensee has scanned greater than 84% of weld volume for six welds in addition to the examination of greater that 90% of six other RPV shell welds.
Furthermore, the licensee has perfonaed visual examinations of the vesselinterior as required by the Code. This level of examination coverage is significent er d should have detected inservice degradation, if present. However, the examination did not reveal any unacceptable flaw. Therefore, the licensee's proposed attemative provides an acceptable level of quality and safety.
4.0 CONCLUSION
I The staff has reviewed the licensee's submittal and concludes that the licensee has maximized examination coverage for the reactor vessel welds and that service-induced degradstion, if present, would have been detected. There 'Nere no unacceptable flaws found as a result of the examination. Thus, it is concluded that the licensee's proposed attemative contained in Request for Alternat ve No. g7 002, provides an acceptable level of quality and safety.
Therefore, the licenseds proposed attemative is authorized pursuant to 10 CFR 50.55a(g)(6)(n)(A) for McGuire Unit 1, Principal Contributer. P. Patnaik Date:
February 4, 1998