ML20198J765

Safety Evaluation Accepting 10-yr Interval Insp Program Plan Alternatives for Listed Plants Units

ML20198J765
Person / Time
Site:	Oconee, Mcguire, Catawba, McGuire
Issue date:	10/15/1997
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML16141B241	List: ML20198J765
References
NUDOCS 9710220086
Download: ML20198J765 (9)

Text

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, 6,a usg k UNITED STATES g j 2

NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30666-0001

\...../

SAFETY EVAllJATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION 10-YEAR INTERVAL INSERVICE INSPECTION PROGRAM PLAN PROPOSED ALTERNATIVE E.OB DUKE ENERGY CORPORATION OCONEE NUCLEAR STATION. UNITS 1. 2. AND 3.

MCGUIRE NUCLEAR STATION. UNITS 1 AND 2.

AND CATAWBA NUCLEAR STATION. UNITS 1 AND 2 DOCKET NOS. 50-269.50 270.50-287. 50-369.

50-370. 50-413. AND 50-414

1.0 INTRODUCTION

The Technical Specifications (TS) for Oconee Nuclear Station, Units 1,2, and 3, McGuire Nuclear Station, Units 1 and 2, and Catawba Nuclear Station, Units 1 and 2, 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 (ASME Code) and applicable addenda as required by Title 10 of the Code of Federal Reoulations (10 CFR) Section 50.55a(g), except where specific written relief has besn granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). Section 50.55a(a)(3) states that attematives to the requirements 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 j supports) shall meet the requirements, except the design and access provisions and the pre-service examination requirements, set forth in the ASME Code,Section XI, " Rules for Inservice Inspection of Nuclear Power Plant Components," to the extent practical within the limitations of Enclosure 1 9710220006 971015 PDR ADOCK 05000269

o 7 j- year interval and subsequent intervals comply with the requirements in the litest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b)

- 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 22 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 ASME Code for the McGuire Nuclear Station, Unit 2, Catawba Nuclear Station, Units 1 and 2, second 10-year inservice inspection (ISI) inte: val and Oconee Nuclear Station, Units 1,2, and 3, third 10-year ISI interval is the 1989 Edition. The Code of record for McGuire Nuclear Station, Unit 1, second 10-year interval inservice inspection is the 1986 Edition.

Pursuant to 10 CFR 50.55a(g)(5), if the licensee determines that conformance with an examination requirement of Section XI of the ASME Cooe is not practical for its facility, . _

information 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 on the facility.

In a letter dated June 20,1997, Duke Energy Corporation (licensee) submitted a proposed attemative f 2 ASME Section XI requirements for Oconee Nuclear Station, Units 1,2, and 3, McGuire Nuclear Station, Units 1 and 2, and Catawba Nuclear Station, Units 1 and 2. As a resu!t of an August 6,1997, conference call, the licensee submitted a revised version of the proposed attemative in a letter dated August 7,1997.

2.0 EVALUATION The staff, with technical assistence from its contractor, the Idaho National Engineering and

- Environmental Laboratory (INEEL), has evaluated the information provided by the licensee in support of its 10-Year Inservice inspection Interval Program Plan Altematives for Oconee

Nuclear Station, Units 1,- 2, and 3, McGuire Nuclear Stauon, Units 1 and 2, and Catawba Nuclear Station, Units 1 and 2. On the basis of the information submitted, the staff adopts the contractor's conclusions and recommendations presented in the Technical Letter Report (TLR)

(Enclosure 2).

Proposed Alternative 97-GO-001, Revision 1, IWA-6260(a)(2), Corrective Measures for Bolted Connections: The 1989 Edition of Section XI IWA-5250(a)(2) requires that if leakage occurs at a bolted connection, the botting shall be removed, VT-3 visually examined for corrosion, and evaluated in accordance with IWA-3100.

I

3-Note: In the 1990 Addenda, IWA-5250(a)(2) requires that only one bolt closest to tb leakage be removed and VT-3 visually examined _ Duke Energy Corporation stated that it previously requested and received approval from the NRC staff to use the 1990 Addenda as an altemative to the requirements of paragraph IWA-5250(s)(2) of the Code of record.

Pursuant to 10 CFR 50.55a(a)(3)(i), the licensee has proposed an altemative to the requirements of the 1990 Addenda, IWA 5250(a)(2), to remove at least one bolt from leaky bolted owinoctions os stated by the licensee below:

When leakage is identified at boited connections by Visual, VT 2 examination during system pressure testing, an evaluation will be performed to determine the susceptibility of the botting to corrosion and assess the potential for failu o. The evaluation will, at a minimum, consider the following factors:

1. Bolting materhis

2. Corrosiveneu of process fluid leaking

3. Leakage location 4.- Leakage history at connection or other system components 5.

Visual evidence of corrosion at connection (while connection is assembled)

6. Service age of bolting materials When the pressure test is performed on a system that is in service or that Technical Specificatens require to be operable, and the botting is susceptible to corrosion, the evaluation shall address the connection's structural integrity until the next component / system outage of sufficient duration. If the evaluations conclude the system gan perform its safety related function, removal of the bolt closest to the source of the leakage and a Visual, VT-3' examination of the bolt will be performed when the system or component is taken out of service for a

{. sufficient duration (to accomplish other system maintenance activities).

For bolting that is susceptible to corrosion, and when the initial evaluation -

4 indicates that the connectioc, cannot conclusively perform its safety function until the next component / system outage of sufficient duration, the bolt closest to the source of the leakage will be removed, and a Visual,VT-3 examination wiil be evaluated in accordance with IWA 3100(a).

' The acceptance criteria for Visual, VT-1 will be used to assess the acceptability of the bolting.-

4 In accordance with the 1990 Addenda, if leakage occurs at a bolted connecilon, one bolt

- closest to the leakage shall be removed, VT 3 visually examined for corrosion, and evaluated in accordance with IWA-3100. _in lieu of this requirement, the licensee has proposed to evaluate

.. the botting to determine its susceptibility to corrosion. The staff has reviewed the licensee's

. submittal and believes that the evaluation process proposed by the licensee provides a sound engineering approach.

- This evaluation considers a number of parameters, including bolting materials, the potential for corrosion, and visual evidence of corrosion with the botting in place, if the evalqation cannot

- confirm the integrity of the joint, the licensee has proposed to remove one bolt nearest the leakage for VT-3 visual examination, and to use the V T-1 acceptance criteria.- The staff agrees with the licensee that the VT-1 acceptance criteria is more appropriate and provides a comprehensive assessment of the structuralintegrity of the bolt, As a result, significant pattoms of degradation will be detected, thus, the proposed attemative provides an acceptable

- level of quality and safety.

3.0 CONCLUSION

The staff has reviewed the licensee's submittal and concludes that the licensee's proposed attemative to the requirements of lWA 5250(a)(2) is a conservative and technically sound engineering approach and provides an acceptable level of quality and safety for leaking bolted connections. Therefore, the licensee's proposed altemative is authorited pursuant to 10 CFR 50.55a(a)(3)(l),

Principal Contributor: Thomas K. McLellan Date: October 15, 1997 4

4 b

i

( TECHNICAL LETTER REPORT ON PROPOSED ALTERNATIVE FOR DUKE ENERGY CORPORATIQN'S OCONEE NUCLEAR STATION. UNITS 1. 2. AND 3.

DaQKELNUMBERS_5126L5A:270. AND 50 287.

MCGUIRE.blUCLEAR STATION. UNITS 1 AND 2, DOCKET NUMBERS 50-369 AND 50-370. AND CATAWBA NUCLEAR STATION. UNITS 1 AND 2.

QQCEEINUMBERS_E0 413 AND 50-414

1.0 INTRODUCTION

By letter dated June 20,1997, the licensee, Dukc Energy Corporation, submitted a proposed attemative to ASME Section XI requirements for Oconee Nuclear Station, Units 1,2, and 3, McGuire Nuclear Station, Units 1 and P., and Catawt:a Nuclear Station, Units 1 and 2. As a result of an August 6,1997, conference call, the licensee submitted a revised version of the proposed alternative in a letter dated August 7,1997. The Idaho National Engineering and Environmental Laboratory (INEEL) staff has evaluated the information provided by the licensee in support of the proposed altemative in the following section.

2.0 EVALUATION The applicable edition of Section XI for the Oconee Unts 1,2, and 3, third 10-year inservice inspection (ISI) interval and the Catawba Units 1 and 2 and McGuire Unit 2 second 10-year ISI interval is the 1989 Edition. The Code of record for McGuire Unit 1 is the 1986 Edition. The proposed attemative has been evaluated and the basis for disposition documented below.

Prooosed Attemative 97-GO-001. Revision 1. IWA-5250(a)(2). Corrective Measures for Bolted Connections Code Reauirement: In the 1989 Edition of Section XI, IWA 5250(a)(2) requires that if leakage occurs at a bolted connection, the bolting shall be removed, VT-3 visually examined for corrosion, and evaluated in accordance with IWA-3100.

t Note: In the 1990 Addenda, IWA-5250(a)(2) requires that only one bolt closest to the leakage be removed and VT-3 visually examined. The licensee stated that Duke Power Corporation previously requested end received approval from the NRC staff to use the 1990 Addenda as an altemative to the requirements of paragraph IWA-5250(a)(2) of the Code 2f record.

Licensee's Prooosed Attemative: Pursuant to 10 CFR 50.55a(a)(3)(i), the licensee has proposed an attemative to the requirements of IWA-5250, f(2), to remove at least one bolt from leaky bolted connections. The licensee stated:

Enclosure 2

2-

• When leakage is identified at bolted connections by Visual, VT-2 examination during system pressure testing, an evaluation will be performed to determine the susceptibility of the bolting to corrosion and assess the potential for failure. The evaluation will, at a minimum, consider the following factors:

1.

• Bolting materials

2. " Corrosiveness of process fluid leaking

3. " Leakage location

4. " Leakage history at connection or other system components 5.

" Visual evidence of corrosion at connet tion (while connection is assembled)

6. " Service age of botting materials l

l "When the pressure test is performed on a system that is in service or that Technical l Specifications require to be operable, and the botting is susceptible to corrosion, the l

evaluation shall address the connection's structural integrity until the next component / system outage of sufficient duration. If the evaluations conclude the system I

sau perform its safety related function, removal of the bolt closest to the source of the leakage and a Visual, VT-38 examination of the bolt will be performed when the 3ystem or component is taken out of service for a sufficient duration (to accomplish other l system maintenance activities).

! *For botting that is susceptible to corrosion, and when the initial evaluation indicates that

! the connection cannot conclusively perform its safety function until the next I

component / system outage of sufficient duration, the bolt obsest to the source of the leakage will be removed, and a Visual, VT-3 examination will be evaluated in accordance with IWA-3100(a).*

JJcensee's Basis for Recuestino Relief (as stated):

' Removal of pressure retaining botting at mechanical conneetions for visual, VT 3 examination and subsequent evaluation, in locations where leakage has been identified, is not always the most disceming course of action to determine the acceptability of the bolting. The Code requirement to remove, examine, and evaluate bolting in this l situation does not allow the owner to consider other factors which may indicate the acceptability of mechenicaljoint botting.

• Other factors which should be considered when evaluating botting acceptability when leakage has been identified at a mechanicaljoint include, but are not limiteo . Joint bolting material, service age of joint bolting materials, location of leakage, history of leakage at the joint, evidence of corrosion with the joint assembled, and corrosiveness of prcoass fluid.

i 8 The acceptance criteria for Visual, VT-1 will be used to assess the acceptability of the bolting.

" Performance of the pressure test while the system is in service may identify leakage at a bolted connection that, upon evaluation, may conclud9 the integri'y and pressure retalning ability of a safety system by romoving tha system from service to address a leak that does not challenge the system's ability to perform its sarety function.

"A situation frequently encountered at Duke Energy Corporation is the compiele replacement of botting materials (studs, bolts, nuts, washers, etc.) at mechanical joints during plant outages. When the assmiated system piping is pressurized during plant start up, leakage is most o' ten due to thermal expansion of the piping and botting materials at the joint and subsequent fluid seepage at the joint gasket, Proper retorquing of the joint botting, in most cases, stops the leakage. Removal of tha joint bolting to evaluate for corrosion would be unwarranted in this situation due, to the new condition of the bolting materials.

Justification for Granting Alternative:

"The purpose of the Code required correc'ive action to remove bolts and visually examine them for degradation, as stated in IWA-5250(a)(2), is to ensure joint integrity, in addition to removing bolts and performing a Visual, VT-3 examination,Section V above [ licensee's basis) states alternative methods to ensure joint integrity of bolted connections. These attemative methods have been determined to provide an acceptable level of quality and safety.'

Evaluation: In accordance with the 1990 Addenda, if leakage occurs at a bolted connection, cne bolt closest to the leakage shall be removed, W3 visually examined for corrosion, and evaluated in accordance with IWA 3100. In lieu of this requ!rement, the licensee has proposed to evaluate the botting to determine its susceptibility to corrosion.

The INEEL staff has reviewed the licensee's submittal and believes that the evaluation pror ; proposed by the licensee provides a sound engineering approach. This evaluation considers a number of parameters, leluding botting r", terials, the potential for corrosion, and visual evidence of corrosion with the bolting in place. If the evaluation cannot confirm the integrity of the joint, the licensee has proposed to remove one bolt nearest the leakage for VT-3 visual examination, and to use the VT-1 acceptance criteria. The INEEL staff agrees with the licensee that the VT-1 acceptance enteria are more appropriate and provide a comprehensive assessment of the stn' alintegrity of the bolt. As a result, significant pattems of degradation will be detnes nd an acceptable level of quality and safety will be provided.

3.0 CONCLUSION

The INEEL staff has reviewed the licensee's submit'.al and conclu' des that the licensee's proposed alternative to the requirements of IWA-5250(a)(2) is a conservative and technically sound engineering approach and will provide an acceptable level of quality and safety for leaking bolted connections. Therefore, it is recommended that the use the licensee's proposed attemative be authorized pursuant to 10 CFR 50.55a(a)(3)(i).