View source for RBG-44011, Forwards Supporting Info for Requesting Approval of Proposed Alternative to 10CFR50.55a(g)(6)(ii)(A) Requirements Re Augmented Exam of Reactor Vessel

{{Adams
| number = ML20198G843
| issue date = 01/07/1998
| title = Forwards Supporting Info for Requesting Approval of Proposed Alternative to 10CFR50.55a(g)(6)(ii)(A) Requirements Re Augmented Exam of Reactor Vessel
| author name = King R
| author affiliation = ENTERGY OPERATIONS, INC.
| addressee name = 
| addressee affiliation = NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
| docket = 05000458
| license number = 
| contact person = 
| document report number = RBF1-98-0001, RBF1-98-1, RBG-44011, NUDOCS 9801130129
| document type = CORRESPONDENCE-LETTERS, INCOMING CORRESPONDENCE
| page count = 8
| project = 
| stage = Request
}}

=Text=
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u=w-ras f>04 635 f;068 Rick J. King t     a saw S Nyawy Moss January 7,1998 U. S. Nuclear Regulatory Commission Document Control Desk, OPl 17 Washington,DC 20555

==Subject:==
River Bend Station -
Docket No. 50-458 Proposed Alternative to 10 CFR 50.55a(gX6Xil)(A) Requirements.
Augmented Examination of Reactor Vessel File No.: G9.5 RBF198-0001 RBO-440ll Ladies and Ocmlemen:
Section 50.55a," Codes and Standards," of Title 10 of the Code offederal Regulations (10 CFR) specifies the requirements of the American Society of Mechanical Engineers Boller and Pressure Vessel Code (the " Code") applicable to nuclear power plants, as w:ll as specifying the augmented examination requiremems deemed necessary for ensuring structural reliability (see Section 50.55a(gX6XiiXA) for augmented requirements). Section XI of the Code prescribes the requirements for inservice inspection of Code Class 1,2, and 3 components.
Section 50.55a(gX6XilXAX2) requires that, for the augmented reactor vessel shell weld examination, essentially 100% of each weld shall be examined. Section 50.55a (gX6XiiXAX2) states that " essentially 100% as used in Table IWB 25001 means more than 90 percent of the examination volume of each weld, where the reduction in coverage is due to interference by another component, or part geometry." Ri,vr Bend Station (RBS) comrieted its first inservice inspection interval and used the " essentially 100 %" reactor shell weld examination required by Section XI for the first interval to satisfy th augmented examination of the reactor vessel.
I RBS has determined that the augmented examinations required by 10CFR50.55a                              )
(gX6XiiXAX2) cannot be completely performed (l.c., coverage ofless than 100% of each P                    0 58
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                 .,.         Proposed Altemative to 10 CFR 50.55a(gX6XilXA) Requirements,                                                                                             j
                          ' Augmented Examination of Reactor Vessel                                   -
January 7,1998                                                                                                                                           l
                           - RBF1-98 0001                                                                                                                                              i RBO-440lI .                                                                                                                                               [
Page 2 of 2                                                                                                                                          1
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                          - weld). Only 62% examination volume coverage could be applied to vessel shell weld AA, which connects the first shell ring to the bottom head due to configuration and geometry.
j
                          - The . weld coverage is limited by both component interference and part geometry.                                                                      ,l Pursuant to 10 CFR 50.55a(gX6Xil)(AX5), EOl submits inf.+rmation to the Commission to                                                                    !
support the determination that the shell weld examination requirements for weld AA cannot;                                                               l be completely satisfied. EOl proposes an attemative to the examination requirements that                                                                 !
will provide an acceptabic level of quality and safety. Contained in the attachment to this                                                             J submittal is the supporting information for requesting approval'of the identified alternative to the specified requirements.
l If you have any questions or require further information, please contact Rick McAdams at                                                                j (504)336-622/
Sincerely,                                                                                                                                               f; 6                       i                                                                                                                           f
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                          - RJK/PLC/kac                                                                                                                                                i attachment                                                                                                                                           "
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cc.          U.S. Nuclear Regulatory Commission (2 copies)
Region IV                                                                                                                                    .-
l 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011                                                                                                                          ,
i NRC Sr. Resident inspector                                                                                                                   [
f P.O. Box 1050 St. Francisville, LA 70775 Mr. David L. Wigginton .                                                                                                                     h
_U.S. Nuclear Regulatory Ccmmission -                                                                                                   3 M/S OWFN 13113 -                                                                                                                             f
                                        - Washington, DC 20555 -                                                                                                                       ,
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          . Attachment I to RBO-440ll I
    .       Proposed Alternative to 10 CFR 50.55a(g)(6)(ii)(A) Requirements, Augmented Examination of Reactor Vessel Page1of5 Proposed Alternative to 10 CFR 50.55a(g)(6)(ii)(A) Requirements, Augmented Examination of Reactor Vessel 1
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  ,     Attachment 1 to RBO-440ll Proposed Alternative to 10 CFR 50.55a(g)(6)(ii)(A) Requirements, Augmented Examination of Reactor Vessel Page 2 0f 5
: 1.      Required Examinations The examination requirements of 10CFR50.55a (g)(6)(ii)(A) are that cil licensees augment their reactor pressure vessel (RPV) examinations for ASME Code, Section XI.
Examination Category B A, item Nu aber Bl.10, by implementing once, as part of the inservice inspection interval in effect on September 8,1992, the examination requirements for the reactor vessel shcIl welds specified in item Bl.10 of Examination Category B A of the 1989 Edition of ASME Section XI. These requirements specify that essentially 100% of die wcld volume for each weld be examined. The regulations define
        " essentially 100%" as more than 90% of the examination volume of each weld (see 10CFR50.55a(g)(6)(ii)(A)(2)).
EO: determined that one of the item Number Bl.10 welds could not be examincJ to the full ASME Code, Section XI, coverage required by 10CFR50.55a (g)(6)(ii)(A).
Specifically, weld AA coverage was limited to 62% examination volume. The total weld volume coverage for all item Bl.10 welds exceeds 90%. Ilowever, the regulations specify that " essentially 100%" applies to each weld. EOI considers that the examinations performed during the first inspection interval may be credited as the augmented examinations pursuant to 10CFR50.55a (g)(6)(ii)(A)(4). Additionally, pursuant to 10CFR50.55a (g)(6)(ii)(A)(5), EOl requests NRC approval of the examination of 62% of weld AA as an alternative to " essentially 100%" based on the acceptable level of quality and safety alTorded by the 62% coverage as discussed below.
: 2.      Basis for Requesting Altemative Examinations i
RBS has a Mark 111 containment with approximately 3 feet of clearance between the biological shield wall and the RPV. Examination of the RPV shell welds were perfonned with manual and automated equipment from the external surface of the RPV in this limited space.
i Weld AA connects the first shell ring of the RPV to the bottom head. The inspection of weld AA was limited. The weld is located at the edge of a transition in vessel diameter.
The geometry is such that it could only be examined from the outside diameter of the weld (the weld cannot be inspected from the vessel interior as it is located below the Shroud Support shelf and is not accessible). " Weld volume" as discussed herein is defined as the area requiring examination per ASME Section XI,1989 Edition, Figure IWB 2500-1.

.
* Attachment I to RIlO 44011 Proposed Alternative to 10 CFR 50.55a(g)(6)(ii)(A) Requirements, Augmented Examination of Reactor Vessel Page 3 of 5 RilS was in the first inspection interval when the augmented examinations became effective (September 8,1992) and was scheduled to perform examinations on essentially 100% of the item 111.10 relds volume per the requirements of Section XI 1980 Edition with Addenda through Winter 1981. The examination requirements for the first inspection interval, based on the 1980 Edition with Addenda through Winter 1981, are the same as those required by the 1989 Edition, which is referenced in 10CFR50.55a for the augmented RPV examinations.
Section 50.55a (g)(6)(ii)(A)(4) states that "[t]he requirement for augmented examination of the reactor vessel may be satisfied by an examination of essentially 100% of the reactor vessel sh-ll welds specified in (Section) 50.55a (g)(6)(ii)(A)(2) that has been completed, or is scheduled for implementation with a written c.,mmitment, or is required by [Section) 50.55a(g)(4)(i), during the inservice inspection interval in effect on September 8,1992." In the accompanying Statement of Considerctions for the rule change that added the augmented RPV weld examination requirements, the NRC said that a licensee hat has either completed or scheduled an inspection of essentially 100% of the length of all examination category ll-A shell welds in the interval in effect when the rule became effective does not have to implement the " augmented examination" of the reactor vessel shell welds, and that "the technical objective of the aun,mented examination will be accomplished under these conditions." 57 Fed. Reg. 34,670 (Aug. 6,1992).
Rils considers the weld inspections in full compliance with the augmented RPV weld examination requirements for the first inservice inspection interval, with the exception of weld AA. Essentially 100% of all the RPV shell welds have been examined. The examination limitation for weld AA is Joe to geometry. As noted above, weld AA is located at the edge of a transition in vessel diameter (see Attachment 1) and cannot be accessed from the interior of the RPV, Accordingly, additional examination coverage of weld AA is not feasible with available examination techniques.
The NRC previously reviewed and approved Relief Request RR0012D, which identified the examination restrictions for weld AA, pursuant to Section 50.55a (g)(6)(i).' Ilecause the rule change fbr augmented RpV examination revoked all previously approved relief requests (see Paragraph (g)(6)(ii)(A)(2)), the alternative requested herein is necessary for the RllS first interval inservice inspection Plan to document the limitations in accordance with the augmented RPV examination requirements.
The reactor vessel shell weld examinations for the second interval will use the same techniques as the first interval inspection. That is, the examinations will be performed
          ' RR0012D for wcid AA was originally approved in NRC's Safety Evaluation dated August 1,1989. Later revisions of the R13S First Interval inservice inspection Program, w hich contained RR0012D, w cre reviewed and discussed la NRC Safety Evah.ations dated as late as June 22,1992. prior to the revocation in the rule efTective September 8,1992.

                                                                                                                               . _.q I
                         , - Attachment I to RBO-44011                                    ..
j
               ,             Proposed Alternative to 10 CFR 50.55a(gX6XiiXA) Requirements, Augmented Examination of Reactor Vessel i       Page 4 of 5                                                                                              :
                                              .                             .                                                         i using a combination of automated and manual examination techniques from the external                     }
surface of the RPV. Even with these techniques, however, coverage of weld AA will be .                   l limited to approximately 62% of the weld volume.                                                         :
                           - 3.       Ju.tification for Using Alternate Examinations :                                                l I
Augmented RPV examinations mandated by 10CFR50.55a (gX6XiiXA) stemmed from-                           L NRC concems with RPV degradation from embrittlement as indicated by irradiation                          !
surveillance material test results, stress corrosion cracking, and service induced cracking.          1 Early Editions of Section XI of the ASME Code, including the Edition for the RBS first                _l
: Inspection interval, required essentially 100% examination of the number of RPV shell                    i welds for the first interval, but only a small percentage aller the first inspection interval.           j
                             'Thus, the rule change for Section 50.55a (gX6XilXA) did not add examinations of shell                   !
welds to the inspection scope for the RBS first inspection inte val. - Section XI,1980 Edition with Addenda through _ Winter 1981, required that RBS perform inspections on                     !
                           ' essentially 100% of the item Number Bl.10 RPV shell welds. These inspections were completed, with limited coverage on only one weld, as discussed above, i
The Boiling Water Reactor Vessel and Intemal Project (BWRVIP) EPRI report, "BWR                          !
Reactor Pressure Vessel Shell Weld Inspection Recommendations," BWRVIP-05, was                           j f
issued in September 1995. This report reviewed BWR fabrication practices, inservice inspection data, operational issues, degradation mechanisms, non-destructive examination                 :
capabliities, r.nd probabilistic fract'are mechanics analysis. The report concludes that, for            !
1                         the item Number Bl.10 welds,50% of the longitudinal shell welds (Category B A, item                      l No. Bl.12) should be examined and that circumferential shell welds (Category B-A, item L                            No. Bl.11) should be climinated from the examination requirements. The BWRVIP -                       j performed a probcbilistic fracture mechanics analysis to quantify its recommendations                    y and concluded that the probability of vessel failure was extremely low and well within NRC safety goals, even with the proposed reduction in the level ofinservice inspection.                  !
                                                                                                                                      )
L                            4.       Conclusion                                                                                      i Preservice ultrasonic inspection of the RBS RPV was performed prior to plant startup.                    i g                         . No' indications that exceeded ASME Section XI acceptance criteria were found during the                  l
.                          i first inservice inspection interval. All item Number Bl.10 welds were examined for                       ;
                            . Inservice inspection, with only one weld (weld AA) examined with less than essentially               j L100% coverage (f.c.,62% coverage of weld AA). Inside diameter tooling cannot be used                     }
to increase the coverage of weld AA.'                                                                 'l 1
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               -     Attachment I to R110 440ll Proposed Alternative to 10 CFR 50.55a(g)(6)(li)(A) Requirements, A,ugmented Examination of Reactor Vessel Page 5 of 5 RilS, still in its first inspection interval when the augmented requirements were issued, was required by Section XI of the ASME Code to perfonn examinations on essentially 100% of Category Il A, Jtem Number 111.10, shell welds. Therefore, pursuant to Section 50.55a, Paragraphs (g)(6)(ii)(A)(4) and (g)(6)(ii)(A)(5), based on essentially 100%
coverage of the welds being examined, except for the limitations on weld AA, the examinations performed for the first inservice inspection interval provide an acceptable level of quality and safety for meeting the augmented examination requirements of Paragraph (g)(6)(ii)(A). Accordingly, NRC approval is requested.

==References:==
: 1. RilS First Interval inservice inspection Plan.
: 2. IlWR Vessel and Internals Project, EPRI Report (llWRVIP-05),"13WR Reactor s'ressure Vessel Shell Weld Inspection Recommendations," dated September 1995,
: 3. NRC Information Notice 97 63: " Status of NRC Staffs Review ofilWRVIP-05,"
dated Augusi 7,1997.
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