ML20196F686

Safety Evaluation Accepting Licensee Second 10-yr Interval ISI Program Plan Request for Alternative to ASME B&PV Code Section XI Requirements Re Actions to Be Taken Upon Detecting Leakage at Bolted Connection

ML20196F686
Person / Time
Site:	Three Mile Island
Issue date:	12/02/1998
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20196F680	List: ML20196F677 ML20196F686
References
NUDOCS 9812070107
Download: ML20196F686 (6)

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION OF THE SECOND 10-YEAR INTERVAL INSERVICE INSPECTION PLAN ALTERNATIVE EDE GPU NUCLEAR. INC.

THREE MILE ISLAND. UNIT 1 DOCKET NO. 50-289

1.0 INTRODUCTION

The Technical Specifications (TS) for Three Mile Island, Unit 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 (B&PV) 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)(i).

10 CFR 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 alternatives 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 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 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) l 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 ASME Code for the i

Three Mile Island, Unit 1, second 10-year inservice inspection (ISI) interval is the 1989 Edition, with the 1990 Addenda. Authorization to use this Edition / Addenda of the Code was obtained in NRC Safety Evaluation, dated October 8,1992.

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5 2.0 EVALUATION By letter dated June 3,1998, GPU Nuclear, Inc., (licensee) submitted the second 10-year interval inservice inspection program plan attemative to the Code for Three Mile Island, Unit 1.

The staff, with technical assistance from its contractor, the Idaho National Engineering and Environmental Laboratory (INEEL), has evaluated the information provided by the licensee in support of its second 10-year interval proposed alternative for Three Mile, Unit 1. Based on the results of the review, the staff adopts the contractor's conclusions and recommendations presented in the Technical Letter Report (TLR) attached.

Code Reouirement ASME Code,Section XI of the ASME Code, Subsection IWA-5250(a)(2) requires that if leakage occurs at a bolted connection, one of the bolts shall be removed, VT-3 visually examined, and evaluated in accordance with IWA-3100. The bolt selected shall be the one closest to the source of leakage. When this bolt has evidence of degradation, all remaining botting in the connection shall be removed, VT-3 visually examined, and evaluated in accordance with IWA-3100.

Proposed Attemative to IWA-5250(a)(2), Corrective Measures for Class 1,2, and 3 Bolted Connections:

The licensee proposed in accordance with 10 CFR 50.55a(a)(3)(i), an attemative to the requirements of IWA-5250(a)(2), to remove at least one bolt from leaking bo!ted connections.

The licensee stated:

"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 botting to corrosion and assess the potential for failure. The evaluation will, at a minimum, consider the following factors:

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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 connection (while connection is assembled) l 6.

Service age of bolting materials *

"When the pressure test is performed on a system that is in service or that Technical Specifications require to be operable, and the bolting is susceptible to corrosion, the evaluation shall address the connection's structural integrity until the next I

component / system outage of sufficient duration. If the evaluations conclude the system can perform its safety related function, removal of the bolt closest to the source of the 1

leakage and a Visual, VT-3 examination of the bolt will be performed when the system l

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' I or component is taken out of service for a sufficient duration (to accomplish other 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 component / system outage of sufficient duration, the bolt closest to the source of the leakage will be removed, and a Visual, VT-3 examination will be evaluated in l

accordance with IWA-3100(a).*

f Staff Evaluation l

l In accordance with IWA-5250(a)(2) of the 1990 Addenda, if leakage occurs at a bolted l

connection, one bolt closest to the leakage must 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 proposed evaluation will consider, as a minimum, bolting materials, the corrosive nature of the process fluid, the leakage location and history, the service age of the bolting materials, and visual j

evidence of corrosion at the assembled connection.

The staff has determined that the evaluation proposed by the licensee is a sound engineering approach and will provide assurance of the leak-tight integrity of bolting. In addition, if the initial evaluation indicates the need for a more detailed ana!ysis, the bolt closest to the source of leakage will be removed, VT-1 visually examined, and evaluated in accordance with IWA 3100(a). The VT-1 examination criteria are more stringent than the simple corrosion l

evaluation described in IWA-5250. The staff also concluded that pursuant to 10 CFR 50.55a(a)(3)(i), the licensee's proposed attemative for Class 1,2, and 3 bolted connections is authorized for the second ISI interval at TMI-1.

3.0 CONCLUSIOB The staff has concluded that the licensee's proposed attemative to the requirements of IWA-l 5250(a)(2) is a conservative and technically sound engineering approach that provides an i

acceptable level of quality and safety for the leaking bolted connections. Therefore, the staff l

concludes that the licensee's proposed alternative for Class 1,2 and 3 bolted connections is authorized pursuant to 10 CFR 50.55a(a)(3)(i) for the second 10-year ISI interval at TMI-1.

Principal Contributor: T. McLellan Date: December 2, 1998 i

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<n TECHNICAL ; ETTER REPORT ON THE SECOND 10-YEAR INTERVAL INSERVICE INSPECTION PROPOSED ALTERNATIVE ED.8 GPU NUCLEAR THREE MILE ISLAND. UNIT 1 DOCKET NO. 50-289

1.0 INTRODUCTION

By letter dated June 3,1998, the licensee, GPU Nuclear, proposed an attemative to the requirements of the ASME Code,Section XI, for Three Mile Island, Unit 1 (TMI-1). This proposed altemative is for the second 10-year inservice inspection (ISI) interval. The Idaho National Engineering and Environmental Laboratory (INEEL) staff's evaluation of the proposed attemative is in the following section.

2.0 EVALUATION The information provided by GPU Nuclear, in support of the proposed attemative to Code requirements has been evaluated and the basis for disposition is documented below. The Code of record for TMI-1's second 10-year ISI interval, which ends in April,2001, is the 1989 Edition, with the 1990 Addenda, of Section XI of the ASME Boiler and Pressure Vessel Code. Authorization to use this Edition / Addenda of the Code was obtained in an NRC Safety Evaluation Report dated October 8,1992.

Prooosed Attemative to IWA-5250(a)(2). Corrective Megigges for Class 1. 2. and 3 Bolted Connections Code Reauirement-Section XI of the ASME Code, Subsection IWA-5250(a)(2) requires that if leakage occurs at a bolted connection, one of the bolts shall be removed, VT-3 visually examined, and evaluated in accordance with IWA-3100. The bolt selected shall be the one closest to the source of leakage. When this bolt has evidence of degradation, all remaining bolting in the connection shall be removed, VT-3 visually examined, and evaluated in accordance with IWA-3100.

Licensee's Proposed Attemative-In accordance with 10 CFR 50.55a(a)(3)(l), the licensee proposed an altemative to the requirements of IWA-5250(a)(2), to remove at least one bolt from leaking bolted connections. The licensee stated:

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"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 botting 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 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 Specifications require to be operable, and the bolting is susceptible to corrosion, the evaluation sha!! address the connection's structural integrity until the next component / system outage of sufficient duration. If the evaluations conclude the system gad 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 d9 ration (to accomplish other system maintenance activities).

"For botting that is susceptible to corro. ion, and when the initial evaluation indicates that the connection 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 will be evaluated in accordance with IWA-3100(a)."

Licensee's Basis for Prooosed Attemative (as stated)-

" Removal of pressure retaining bolting at mechanical connections 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 botting. The Code requirement to remove, examine, and evaluate bolting in this situation does not allow the owner to consider other factors which may indicate the acceptability of mechanicaljoint botting.

"Other factors which should be considered when evaluating bolting acceptability when leakage has been identified at a mechanicaljoint include, but are not limited to: 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 process fluid.

" Performance of the pressure test while the system is in service may identify leakage at a bolted connection that, upon evaluation, may conclude the integrity and pressure retaining ability of the joint is not challenged. It would not be prudent to negatively impact the availability of a safety system by removing the system from service to address a leak that does not challenge the system's ability to perform its safety function.

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

3 "A situation frequently encountered at GPU Nuclear is the complete replacement of bolting materials (studs, bolts. nuts, washers, etc.) at mechanical joints during plant outages.

When the associated system piping is pressurized during plant start up, leakage may be identiSed at those joints. The root cause of this leakage is most often due to thermal expansion of the piping and bolting materials at the joint and subsequent fluid seepage at the joint gasket. Proper re-torquing of the joint bo! ting, in most cases, stops the leakage.

Removal of the joint bolting to evaluate for corrosion would be unwarranted in this situation due to the new condition of the bolting materials.

Justification for Granting Altemative:

"The purpose of the Code required corrective 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 attemative methods to ensure joint integrity of bolted connections. These attemative methods have been determined to provide an acceptable level of quasty and safety."

Evaluation-in accordance with IWA-5250(a)(2) of the 1990 Addenda, if leakage occurs at a bolted connection, one bolt closest to the leakage must 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 bolting to determine its susceptibility to corrosion. The proposed evaluation will consider, as si minimum, bolting materials., the corrosive nature of the process fluid, the leakage location nd history, the service age of the bolting materials, and visual evidence of corrosion at the assembled connection.

Based on the items included in the evaluation process, the INEEL staff believes that the evaluation proposed by the licensee is a sound engineering approach. In addition, if the initial evaluation indicates the need for a more detailed analysis, the bolt closest to the source of leakage will be removed, VT-1 visually examined, and evaluated in accordance with IWA-3100(a). The VT-1 examination criteria are more stringent than the simple corrosion evaluation described in IWA-5250. Therefore, pursuant to 10 CFR 50.55a(a)(3)(l), it is recommended that the licensee's proposed attemative be authorized for the second ISI interval at TMI-1.

3.0 CONCLUSION

The INEEL staff evaluated the licensee's submittal and concluded that the licensee's proposed attemative 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 the leaking bolted connections. Therefore, it is recommended that the use of the licensee's proposed altemative be authorized pursuant to 10 CFR 50.55a(a)(3)(l) for Class 1,2, and 3 bolted connections for the current ISI interval.