ML20197J934

Safety Evaluation Accepting Licensee Request for Relief from Performing Inservice Volmetric Exam of Inaccessible Portions of RPV Lower Shell to Lower Head Ring Weld During 10-yr ISI Interval of Plant,Unit 2

ML20197J934
Person / Time
Site:	Point Beach
Issue date:	12/12/1997
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20197J928	List: ML20197J924 ML20197J934
References
NUDOCS 9801050142
Download: ML20197J934 (4)

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p* U:o y t UNITED STATES s" j R

NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. enmaa anni

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ON THE THIRD 10-YEAR INSERVICE INSPECTION INTERVAL WISCONSIN ELECTRIC POWER COMPANY POINT BEACH NUCLEAR PLANT. UNIT NO._2 RELIEF REQUEST NO. RR-2-20 DOCKET NO. 50-301

1.0 INTRODUCTION

The Technical Specifications for Point Beach Nuclear P; ant (PBNP), Unit 2, state that the inservice inspection (ISI) 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 Boiler and Pressure Vessel Code and applicable 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)(;).10 CFR 50.55a(a)(3) states that attematives to the requkements 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 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, met 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 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 ctart of the 120-month interval, subject to the limitations and modi'ications listed therein. The applicable edition of Section XI of the ASME Code for Point Beach Unit 2, for the third ISI interval is the 1986 EdE3on. 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.

ENCLOSURE

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. 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, iaformation 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 attemative 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 imposed.

By letter dated January 27,1995, as supplemented on October 20,1997, Wisconsin Electric Power Company (the licensee) requested relief from compliance with the 1986 Edition of ASME Code,Section XI, Table IWB-2500-1, which requires a volumetric examination of essentially 100% of the weld length for the reactor vessel lower shell to lower head ring circumferential weld due to permanent obstructions that limit accessibility to perform the Code examination.

The staff has reviewed and evaluated the licensee's request and supporting information on the proposed attemative to the Code requirements for Point Beach Unit 2, pursuant to the provisions of 10 CFR 50.55a(g)(6)(i).

2.0 DISCUSSION Comnonent identificatiom Reactor Pressure Vessel Lower Shell to Lower Head Ring Weld Weld No. RPV.17-683 Code: ASME Code,Section XI, Examination Category: B-A, item No. B1.21 Code Reaulrament:

ASME Section XI,1986 Edition, Table IWB-2500-1, requires a volumetric examination of essentially 100% of the weld length.

Nternate.Reauirement:

PBNP proposes that the percentage requirement of essentially 100 percent of weld length be waived for weld RPV-17-683. RPV-17-683 will be examined to the extent practical taking into account known limitations.

Ramann_fotP.tonem During the second 10-year inspection interval for Unit 2, the reactor vessel examination performed in 1989 adopted the selection requirements of ASME Section XI 1989 Edition for Category B-A welds. PBNP performed examinations of all of the Category B-A welds during the 1989 reactor vessel examination even though this was not a mandated requirement at the

time. Essentially 100 percent of all welds were examined with the exception of weld RPV 683. Approximately 75 percent of the weld volume was examined due to limitations. Parallel and transverse examinations were limited above the weld by interference from the four core barrel antirotation lugs. Transverse examinations are limited because of search unit bridging on the shell to head transition.

To achieve the requirements of examining essentially 100 percent of weld length, the antirotation lugs would require removal and subsequent reinstall & tion. This is not practical and would be very detrimental to the reactor vessel.

Prior to the end of the second 10-year inspection interval, Federal RegisterVol. 57, No.152, dated August 6,1992, mandated the use of ASME Section XI 1989 Edition for Category B-A i welds. Based on the reactor vessel examination performed during 1989, PBNP met the requirements for the second 10-year interval.

During the reactor vessel examination scheduled for the third 10-year interval, the same physical kmitations will exist which will prevent essentially 100 percent of the weld volume from being examined. It is expected that approximately 75 percent of the weld will be examined.

3.0 EVALUATION Pursuant to 10 CFR 60.55a(g)(5), the licensee states that conformance with the requirements of the ASME Code,Section XI,1986 Edition, Table IWB-2500-1 in regard to volumetric examination coverage of essentially 100 percent of the lower shell to lower head ring weld in the Unit 2 reactor vessel, is impractical due to obstructions from permanent attachments inside the vessel. A best-effort examination of the above weld would achieve 75 percent volumetric coverages in lieu of greater than 90 percent coverage required by the Code. If the Code requirement is imposed on the licensee, the permanent attachments need to be removed from the vessel during the examination and replaced in the vessel following the examination which imposes a burden on the licensee.

Nevertheless, the subject weld is located beyond the vessel beltline region and, therefore, is not exposed to critical neutron fluence to adversely affect its fracture toughness. The staff has further determined that unacceptable flaws caused due to any degradatior, mechanism, if present, would be detected with reasonable confidence with volumetric examination coverages of 75 percent for the subject weld. Therefore, the licensee's proposed testing would provide reasonable assurance of structuralintegrity.

4.0 CONCLUSION

The staff has reviewed the licensee's submittal and concludes that compliance to the Code examination requirement is impractical for the lower shell to lower head ring weld because of obstructions from permanent attachments to the vessel. If the Code requirement were imposed, the reactor vessel has to be modified which irnposes a burden on the licensee. The proposed test, however, provides reasonable assurance of structural integrity and that service-induced degradation, if present, would be detected. Therefore, the licensee's request for relief from the applics ble ASME Code,Section XI, as stated in Relief Regost No. RR-2-20, is

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.- . 4 granted pursuant to 10 CFR 50.55a(g)(6)(l) for Point Beach Unit 2, durirg the third 10-year inspection interval. The relief granted is ruthorized by law and will not endanger life or property

- or the common defense and securl y and is otherwise in the public interest giving due consideration to the burden upon the licensee that would result if the requirement was imposed on the facility.

4 Principal Contributor: P. Patnaik Date: December 12, 1997 1

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