ML20195J687

Safety Evaluation Supporting Proposed Alternative Contained in RR-ENG-2-5.Proposed Alternative Authorized Per 10CFR50.55a(a)(3)(i) for 2nd ISI Interval

ML20195J687
Person / Time
Site:	South Texas
Issue date:	06/17/1999
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20195J680	List: ML20195J673 ML20195J687
References
NUDOCS 9906210082
Download: ML20195J687 (2)

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UNITED STATES i '

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NUCLEAR REGULATORY COMMISSION o

WASHINGTON, D.C. 20066 4 001

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE SECOND 10-YEAR INTERVAL INSERVICE INSPECTION PLAN 1

l fiEQUEST FOR RELIEF NO. RR-ENG-2-5

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STP NUCLEAR OPERATING COMPANY SOUTH TEXAS PROJECT. UNITS 1 AND 2 DOCKET NOS. 50-498 AND 50-499

1.0 INTRODUCTION

Insevice inspection (ISI) of the American Society of Mechanical Engineers (ASME) Code Class 1,2, and 3 components shall be performed in accordance with Section XI o? the ASME Boiler and Pressure Vessel Code (ASME Cede) and applicable addenda as required by 10 CFR 50.55a(g), except where specific relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). Section 50.55a(a)(3) of Title 10 of the Code of FederalRegulations states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed alternatives would provide an acceptable level of quality and safety j

or (ii) compliance with the specified requirements would result in hardship or unusual difficulty I

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 l

pre-service examination requirements, set forth in the ASME Code,Section XI, " Rules for

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Inservice inspection of Nuclear Power Plant Components," to the extent practical within the j

limitations of design, geometry, and materials of construction of the components. The j

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) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable edition of Section XI of the

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ASME Code for the South Teyas Project, Units 1 and 2, second 10-year ISI interval is the 1989 Edition.

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Pursuant to 10 CFR 50.55a(g)(4)(iv), inservice examination of components and system pressure tests may meet the requirements set forth in subsequent editions and addenda that are incorporated by reference in 10 CFR 50.55a(b), subject to the limitations and modifications listed in 10 CFR 50.55a(b), and subject to Commission approval. Portions of editions or j

addenda may be used provided that all related requirements of the respective editions or addenda are met.

l ENCLOSURE

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2 2.0 EVALUATION ASME Code,Section XI, Examination Category B-G-1, item B6.50 requires 100 percent VT-1 visual examination of all surfaces of reactor vessel pressure-retaining bushings.

In accordance with 10 CFR 50.55a(a)(3)(i), the licensee proposed to perform a straight beam ultrasonic examination of the reactor pressure vessel Roto-Lok vessel inserts (bushings) from the top end of the vesselinserts in lieu of the Code-required VT-1 visual examination. The Code requires that reactor vessel flange bushings be VT-1 visually examined (in place) when the connections are disassembled. The Roto-Lok flange inserts are designed with conventional threads on the outside surface and three rows of lugs on the inside surface. The insert threads mate with the vessel flange threads. The Code requires a volumetric examination of reactor vessel flange threaded ligaments.

-The licensee proposed as an alternative to perform a straight beam ultrasonic examination of the Roto-Lok insert from the top of the insert. This examination would be performed concurrently with that of the vessel flange threads to detect any potential radial-circur 'erential flaws. The ultrasonic technique will examine the entire length of the vessel insert and is expected to be s'Jperior to the VT-1 examination. In addition, the licensee stated that the straight becm ultrasonic examination procedure for the vessel inserts has been demonstrated to ensure examination adequacy.

The staff determined that this technique provides an acceptable level of quality and safety by providing assurance of structural integrity. Therefore, the licensee's proposed alternative is authorized pursuant to 10 CFR 50.55a(a)(3)(i) for the second ISI interval.

3.0 _QQNCLUSION The staff concludes that the licensee's proposed alternative contained in relief request RR-ENG-2 5 provides an acceptable level of quality and safety; therefore, the licensee's proposed alternative is authorized pursuant to 10 CFR 50.55a(a)(3)(i) for the second ISI interval.

PrincipalContributor: T. Alexion Date: ' June 17, 1999 I