ML20248D510

Requests Authorization of Alternative Exam for RPV Shell Welds,Per Provisions of 10CFR50.55(g)(6)(ii)(A)(5).Info & Justification Re Request,Encl

ML20248D510
Person / Time
Site:	Vogtle
Issue date:	05/21/1998
From:	Woodard J SOUTHERN NUCLEAR OPERATING CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LCV-1124-B, NUDOCS 9806030021
Download: ML20248D510 (7)

Text

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• J. D.Woodard Southern Nuclear t Executive Vice President Operating Company, lac.

40 inverness Center Parkway Post Office Box 1295 Birmingham. Alabama 35201 Tel 205992.5086 l

SOUTHERNkL COMPANY Energ to Servekr%rM" LCV-1124-B Docket No.: 50-424 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washingtor,LC 20555 Ladies and Gentlemen:

VOGTLE ELECTRIC GENERATING PLANT REQUEST FOR ALTERNATIVE TO 10 CFR 50.55a(g)(6)(ii)(A)

AUGMENTED EXAMINATION OF REACTOR PRESSURE VESSEL In accordance with the requirements of 10 CFR 50.55a(g)(6)(ii)(A), the reactor pressure vessel (RPV) shell welds on Vogtle Electric Generating Plant, Unit 1 (VEGP-1) were examined during the sixth maintenance / refueling outage (1R6)in Spring 1996. Physicallimitations prevented completing the examination of more than ninety percent (90%) of the examination volume of seven RPV welds.

Based on the information and justification provided in the enclosure, Southern Nuclear Operating Company requests NRC authorization of an alternative examination per the provisions of 10 CFR 50.55a(g)(6)(ii)(A)(5) for these welds.

Should there be any questions in this regard, please contact this office.

Sincerely,

< ; v .11 A

. Woodard JDW/JAE/DRC/dre

\t

Enclosure:

Request for Alternative to 10 CFR 50.55a(g)(6)(ii)(A) 9006030021 990521 A o ci f PDR ADOCK 05000424 P PM _

U. S. Nuclear Regulatory Commission

. LCV-1124-B Page Two xc: Southern Nuclear Operating Comnany -

Mr. J. B. Beasley, Jr. (w/o enclosure) _

Mr. W. L. Burmeister (w/o enclosure)

~ Mr. M. Sheibani (w/ enclosure)

SNC Document Management (w/ enclosure)

U. S. Nuclear Regiilatory Commission Mr. D.11. Jaffe, Senior Project Manager, NRR (w/ enclosure)

Mr. L.' A. Reyes, Regional Administrator (w/ enclosure)

Mr. J. Zeiler, Senior Resident Inspector, Vogtle (w/ enclosure) l l

. ENCLOSURE TO SOUTIIERN NUCLEAR OPERATING COMPANY LETTER LCV-1124-B VOGTLE ELECTRIC GENERATING PLANT REOUEST FOR ALTERNATIVE TO 10 CFR 50.55a(gV6)hiVA)

Soutisern Nuclear Operating Company (SNC) has determined that the augmented examinations of the Vogtle Electric Generating Plant, Unit 1 (VEGP-1) reactor pressure vessel (RPV) cannot be performed to the extent required by 10 CFR 50.55a(g)(6)(ii)(A) without undue hardship. In accordance with the provisions of 10 CFR 50.55a(g)(6)(ii)(A)(5), SNC requests NRC authorization of an alternative examinMion based on other pertinent examinations performed to date which provide an acceptable level of quality and safety.

REOUIRED EXAMINATIONS 10 CFR 50.55a(g)(6)(ii)(A) requires that all licensees augment their RPV examinations by implementing once, as part of the inservice inspection interval in effect on September 8,1992, the examination requirements for reactor vessel shell welds specified in Item No. Bl.10 of Examination Category B-A," Pressure Retaining Welds in Reactor Vessel", in Table IWB-2500-1 of Subsection IWB of the 1989 Edition of ASME Section XI, Division 1, of the ASME Boiler and Pressure Vessel Code. To meet the requirements of 10 CFR 50.55a(g)(6)(ii)(A), "more than 90% of the examination volume of each weld" shall be examined.

COMPLE1 ED EXAMINATIONS Southern Nuclear Operating Company contracted the Nuclear Steam System Supply (NSSS) vendor to perform the examinations of the VEGP-1 RPV. The ultrasonic examinations (UT) were performed using a remote reactor vessel inspection tool to satisfy the requirements of the 1983 Edition of ASME Section XI with Addenda through Summer 1983 and NRC Regulatory Guide 1.150. A total of three circumferential and nine longitudinal RPV shell welds were examined to satisfy the requirements of both the augmented RPV shell weld rule and ASME Code Section XI. The examination results for these welds revealed no recordable indications that exceeded the allowable standards of ASME Code,Section XI Paragraph IWB-3500. The coverage achieved for each weld is listed in Table 1.

ALTERNATE EXAMINATIONS I ower Shell To Bottom Head Weld (WO6) and Longitudinal Welds (W18. W19. & W20)

~ Six RPV core support lugs are located on the lower shell of the RPV adjacent to lower shell-to-E-1

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VOGTLE El.ECTRIC GENERATING PLANT REOUEST FOR ALTERNATIVE TO 10 CFR 50.55a(g)(6)(ii)(A) l I

(continued)

Lower Shell To llottom IIcad Weld (WO6) and Longitudinal Welds (W18. W19. & W20)

(continued) l I

bottom head weld 11201-V6-001-WO6. Three of these six lugs are welded directly onto intersecting longitudinal welds W18, W19, and W20.

These core support lugs obstructed movement of the mechanized examination equipment sled / transducer along the lower shell side (upper scan region) of circumferential weld WO6. As a result, examination coverage of this non-beltline weld from the inside diameter (ID) of the RPV was limited to approximately sixty-two percent (62%) of the weld length. This result is l comparable to the sixty-six percent (66%) coverage reported during preservice examinations (PSI).

Examination of the affected longitudinal welds underneath the core support lugs from the ID of the RPV is not physically possible; therefbre, the examination volume coverage was limited to approximately seventy-seven percent (77%) of the weld length fbr each of the longitudinal welds. This result is comparable to the seventy-one percent (71%) coverage reported during )'

preservice examinations.

Maximum, practical coverage was obtained fbr the subject longitudinal welds from the ID; however, performance of supplemental examinations from the RPV outside diameter (OD) was evaluated as a possible means ofincreasing coverage for these welds. These evaluations concluded that supplemental OD examinations could increase the total coverage to " greater than 90%"; however, such coverage was considered impractical due to the associated radiation exposure (estimated as approximately 9.625 Rem (R)). This conclusion was based on the fbliowing:

e General area dose rates at the bottom of the vessel (as measured Ibr VEGP-2 during its sixth maintenance / refueling outage (2R6)) are estimated to be approximately 200 millirem / hour (mr/hr) with contact dose rates at the insulation surface approximately 1 Rem / hour (R/hr).

• Nondestructive examination (NDE) personnel would need to perform thirteen UT scans fbr each area receiving the supplemental examinations. It is calculated that the dose to the NDE personnel in perfbrming these examinations would be approximately 5 R.

. Prior to performing examinations, personnel would need to erect any necessary scaffbiding, remove insulation, and perform any required weld preparation in the high radiation field.

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1 VOGTLE ELECTRIC GENERATING PLANT REOUEST FOR ALTERNATIVE TO 10 CFR 50.55a(g)(6)(ii)(A)

(continued)

Lower Shell To Bottom llead Weld (WO6) and Longitudinal Welds (W18. W19. & W20)

(continued)

This effort is further exacerbated by the fact that much of the RPV insulation used at VEGP l was designed using rivets and screws and does not lend itself to easy removal and replacement. After examinations were completed, any scaffolding would need to be removed and insulation would need to be replaced. The actual number of person-hours spent in the vicinity of the RPV would not be known until such an effort was completed; however, the dose is estimated to be approximately 4.75 R.

• NDE personnel would need to locate and mark the areas where the supplemental examinations need to be performed. When performing ID examinations, limitations are located in respect to the core support lugs and the RPV flange, using indexing provided by the automated inspection tool. Translating these locations to the OD with a high degree of confidence would be an extremely difficult task while working in a high radiation field.

Upper Shell Longitudinal Welds (W12. W13. W14)

Physical obstructions, e.g., surface scan interference due to nozzle center bore configuration, created by the RPV nozzles in the proximity of the subject RPV upper shell longitudinal welds prevented 100% volumetric examination of their entire weld length from the ID of the RPV. As I a result, the examination volume coverage was limited to approximately seventy-five percent I (75%), eighty percent (80%), and eighty-five percent (85%) of the weld length for welds 11201-V6-001-W12,11201-V6-001-W13, and 11201-V6-001-W14, respectively, during inservice inspection. Coverage reported during preservice examinations was reported as one hundred percent (100%). Immersion techniques were used during preservice examinations versus the contact techniques generally used today by automated NDE vendors; however, for this configuration, the difference is considered to be primarily in the method used to calculate coverage.

The maximum, practical coverage was obtained for these welds from the ID. Supplemental examinations from the OD of the RPV were evaluated but were considered to be impractical j because the welds are located behind the biological shield wall.

CONCLUSION 1

The areas not receiving ID examinations are not located in the beltline region; therefore, E-3

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VOGTLE ELECTRIC GENERATING PLANT

, REOUEST FOR ALTERNATIVE TO 10 CFR 50.55a(gV6ViiVA)

(continued) l CONCLUSION (continued) l concerns with radiation embrittlement is not a factor. These welds had a complete ultrasonic examination performed from the OD in the fabrication shop, as a conservative measure, to ensure there were no unacceptable flaws that would need to be evaluated during preservice examinations. A review of fabrication shop ID and OD data indicates that no indications were observed in the areas not receiving ID inservice coverage; therefore, there is little likelihood of a crack propagating from a fabrication defect in these areas.

The examination of RPV shell welds provides an acceptable level of quality and safety even though all could not be fully examined. The average examination coverage of all Category B-A, Jtem No. Bl.10 welds was greater than 85% and each weld (or portions of welds) located in the beltline region, i.e., welds WO5, W15, W16, and W17, received 100% coverage.

These completed examinations provide reasonable assurance that unacceptable service-induced flaws have not developed in these welds and that RPV shell weld integrity is maintained. The examinations were performed to the extent practical using state-of-the-art equipment and techniques within the limitations of design and access of the RPV. The evaluations and examinations performed meet the objectives of the augmented examinations defined in 10 CFR 50.55a(g)(6)(ii)(A), therefore, the proposed alternative should be authorized by the NRC. Based on the results of the examinations discussed above, SNC concludes that the public health and safety will not be endangered.

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VOGTLE ELECTRIC GENERATING PLANT REOUEST FOR ALTERNATIVE TO 10 CFR 50.55a(gV6ViiVA)

(continued)

TABLE 1 VEGP-1 RPV WELDS EXAMINATION COVERAGE

SUMMARY

(Category B-A / Item No. Bl.10)

- *E WSamm & &AABETAT8" a - saE*3E% 3 mms * - w eeni M S W WO4 B 1.11 MAIN LOOP NOZZLES 100 % 100 % >90%

WO5 B1.11 N/A 100 % 100 % 100 %

WO6 Bl.11 CORE SUPPORT LUGS 100 % 66 % 62 %

W12 Bl.12 MAIN LOOP NOZZLES 100 % 100 % 75 %

W13 B 1.12 MAIN LOOP NOZZLES 100 % 100 % 80 %

W14 Bl.12 MAIN LOOP NOZ7LES 100 % 100 % 85 %

W15 B l .12 N/A 100 % 100 % 100 %

W16 BE12 N/A 100 % 100 % 100 %

W17 Bl.12 N/A 100 % 100 % 100 %

W18 Bl.12 - CORE SUPPORT LUGS 100 % 71 % 77 %

W19 B l .12 CORE SUPPORT LUGS 100 % 71 % 77 %

W20 B l.12 CORE SUPPORT LUGS 100 % 71 % 77 %

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