ML20206A656

Safety Evaluation Authorizing Licensee Re Rev 9 to First 10-year ISI Interval Program Plan & Associated Requests for Relief (RR) 65 from ASME Boiler & Pressure Vessel Code

ML20206A656
Person / Time
Site:	Vogtle
Issue date:	04/21/1999
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20206A641	List: ML20206A637 ML20206A656
References
NUDOCS 9904280264
Download: ML20206A656 (4)

Text

e neg

~

ff k*

UNITED STATES

, .. .g NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30ess-ceM SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REVISION 9 - FIRST 10-YEAR INSERVICE INSPECTION INTERVAL PROGRAM PLAN ftELIEF REQUEST 65 SOUTHERN NUCLEAR OPERATING COMPANY. INC.. ET AL.

VOGTLE ELECTRIC GENERATING PLANT. UNIT 1 DOCKET NO. 50 424

~

1.0 INTRODUCTION

The Technical Specifications for Vogtle Electric Generating Plant, Unit 1 (VEGP-1), state that the inservice inspection 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 Boiler and Pressure Vessel Code and applicable addenda as required by Title 10 of the Code of Federal Reaulations (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). Seebon (10 CFR) 50.55a(a)(3) states that altomatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed altematives 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 (induding 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 prar.tical 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 applicable ASME Code,Section XI, for the VEGP-1, first 10 year inservice inspection (ISI) interval is the 1983 Edition including the Summer 1983 Addendum. 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.

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 I

9904290264 990421 PDR ADOCK 05000424 P- PDR g

]

l o 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 imposo alternative r6quirements 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 imposed.

By letter dated May 28,1998, Southem Nuclear Operating Company Inc. (the licensee),

submitted a request for relief from the Code-required volumetric examination coverage of the reactor pressure vessel (RPV) outlet nozzle-to-vessel welds for the first 10-year inspaction interval. For each of the four outlet nozzle-to-vessel welds, the ultrasonic scan of tne weld from the nozzle bore for reflectors parallel to the weld resulted in a volumetne coverag:: of essentially 100%. However, the scan of the same weld for reflectors transverse to the weld resulted in ,

approximately 40% volumetric coverage due to interference of t% nozzle protrusion with the l scanner. Therefore, a composite volumetric coverage of approximately 70% was obtained for each of these welds, as opposed to the Code-required volumetric coverage of over 90%. The licensee has determined that the Code-required volumetric examination of the subject welds is impractical. The staff has reviewed and evaluated the licensee's request for relief and the supporting information, pursuant to 10 CFR 50.55a(g)(6)(i) for VEGP-1.

2.0 DISCUSSION System / Component for which Relief is Requested RPV outlet nozzle to shell welds 11201-V6-001-W25, W28, W29 and W32.

Code Reauirement for which Relief is Reauested ASME Code,Section XI, Category B-D, item No. B3.90, requires a volumetric examination of RPV nozzle-to-vessel welds. The examination volume shown in Figure IWB-2500-7(a) includes  ;

100% of weld length. In addition, ASME Code,Section XI, Paragraph IWA-2232, requires that  !

ultrasonic examination of vessel welds greater than two inches in thickness be conducted in accordance with the ASME Code,Section V, Article 4, which requires two-directional coverage 1 wherever feasible. For reflectors parallel to the nozzle-to-vessel-weld, the ASME Code, l Section V, Article 4, Paragraph T-441.5.1 requires that search units be directed perpendicular to  !

the weld so that the angle beams pass through the entire volume of the weld metal. The adjacent base metal is required to be completely scanned by two angle beams; however, it is  ;

not necest.ary to scan from both directions. For reflectors transverse to the nozzle-to-vessel weld, Paragraph T-441.5.2 of this Code requires that search units be directed parallel to the axis of the weld s'ch that the angle beams pass through all of the examination volume. Scanning is required to be done in two airections,180 degrees to each other, except that, for those areas blocked by geometric conditions, scanning is required in at least one direction. Relief is requested from meeting the Code-required coverage for the subject welds during scanning for reflectors oriented transverse to the weld.

l Licensse's Basis for Relief "The required examination volume and associated weld configuration (barrel type nozzle with a protruding inner radius) for the outlet nozzles is shown in the ASME Section XI, Figure IWB-2500-7(a). Coverage and limitations for this configuration are listed below; (1) Reflectors Parallel to the Outlet Nozzle-to-Vessel Weld- Ultnuonic examinations will be performed from the nozzle bore using scans as allowed by T 441.4.2. Coverage from this diredion is 100%.

(2) Reflectors Transverse to the Outlet Nozzle-to-Vessel Weld- Ultrasonic examinations will be performed on the inside diameter (ID) of the vessel wall and accessible portions of the adjoining nozzle using scans, directed clockwise and counterclockwise. Tb protruding inner radius (nozzle boss) limits scanning of the nozzle due to interference with the scanner. Coverage from this direction is estimated to be approximately 40%.

Composite Coverage- Composite coverage is calculated to be 70% based on the average of the parallel and the transverse scans stated above."

Alternate Examination

" Ultrasonic examination of these welds will be performed to the maximum extent practical from the nozzle bore and from the RPV ID surface. No $;c 3xamination will be conducted."

l 3.0 EVALUATION ,

The staff has evaluated the information provided by the licensee in support of the volumetric )

examinations of the RPV nozzle-to-vessel welds performed during the first 10-year inservice i inspection interval. For the subject nozzle welds, the volumetric coverage during scanning for i parallel reflectors is 100%; whereas, the coverage for the transverse reflectors is 40%. The staff j has determined that the scanning for transverse reflectors is obstructed due to the nozzle '

protrusion in the case of each nozzle. Therefore, it is impractical to meet the Code 4 requirements. In order to meet the Code requirements, the nozzles would have to be redesigned, fabricated, and installed in the RPV. This process would impose significant burden on the licensee. The licensee's best-effort examination resulted in a composite volumetric coverage of 70%. The results of the examination did not identify any rejectable !ndication. The staff concludes that if there were any service-induced flaws existing in the welds the examination of the accessible weld volume would have detected it with high degree of confidence. Therefore, the staff has determined that the licensee's limited examination of the welds does provide a reasonable assurance of the structural integrity of the subject welds.

1

F s

4

4.0 CONCLUSION

The staff has reviewed the licensee's submittal and has concluded that it is impractical to corr. ply with the Code requirements due to interference of the nozzle protrusion. The staff has further determined that if the Code requirements were to be imposed on the licensee, the components must be redesigned, fabricated and installed, which would impose a significant burden on the licensee. The staff concludes that the examination coverage of the accessible weld volume provides a reasonable assurance of the structuralintegrity of the subject welds. Therefore, the relief is authorized pursuant to 10 CFR 50.55a(g)(6)(i) for the first 10-year inservice inspection interval of VEGP-1. The relief granted is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.

Principal Contributor: P. Patnaik Date: April 21,1999 1

l I

4 i

I i

l j