ML20198S757

Safety Evaluation Accepting Licensee Request for Approval to Repair Flaws IAW GL-90-05 for ASME Code Class 3 Svc Water Piping

ML20198S757
Person / Time
Site:	North Anna
Issue date:	01/15/1998
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20198S737	List: ML20198S733 ML20198S757
References
GL-90-05, GL-90-5, NUDOCS 9801260277
Download: ML20198S757 (5)

Text

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[ t UdlTED STATES g g NUCLEAR REGULATORY COMMISSION

, F WASHINGTON, D.C. 30656 4 001 I k .... /

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR APPROVAL TO REPAIR FLAWS IN ACCORDANCE WITH GENERIC LETTER 90 E FOR ASME CODE CLASS 3 SERVICE WATER PIPING VIRGINIA ELECTRIC AND POWER COMPANY

!  !! ORTH ANNA POWER STATION. UNITS 1 AND 2

i. DOCVET NOS. 50 338 AND 50 339

1.0 INTRODUCTION

10 CFR 50.55a(g) requires nuclear power facility piping and components to meet the applicable requirements of Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (hereafter reitrred to as the Code).Section XI of the Code specifies Code-acceptable r.' pair methods for flaws that exceed Code acceptance limits in piping that is t

in-service. A Code repair is required to restore the structural integrity of flawed Code piping, independent of the operational mode of the plant wher. the

. law is detected. Those repairs not in compliance with Section XI of the Code are non-Code repairs. However, the implementation of required Code (weld) repairs to ASME Code Class 1, 2 or 3 systems is often impractical for nuclear licensees since the repairs normally require an isolation of the system requiring the repair, and often a shutdown of the nuclear power plant.

Alternatives to Code requirements may be used by nuclear licensees when authorized by the Director of the Office of Nuclear Reactor Regulation if the proposed alternatives to the requirements are such that they are shown to provide an acceptable level of quality and safety in lieu of the Code requirements [10 CFR 50.55a(a)(3)(i)), or if compliance with the Code requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety [10 CFR 50.55a(a)(3)(ii)).

A licensee may also submit recuests for relief from certain Code requirements when a licensee has deteritinec that conformance with certain Code requirements is im3ractical for its facility [10 CrR 50.55a(g)(5)(iii)). Pursuant to 10 CFR 50.55a(g)(6)(1), the Commission will evaluate determinations of impracticalityandmaygrantreliefandmayimposealternativerequirementsas it determines are autnorized by law.

Generic Letter (GL) 90 05 " Guidance for Performing Temporary Non Code Repair of ASME Code Class 1. 2 and 3 Piping," dated June 15, 1990, provides guidance for the staff in evaluating relief requests submitted by licensees for temporary non Code repairs of U 1e Class 3 piping. For the purposes of GL 90 05, impracticality is ned to exist if the flaw detected is in a ENCLOSURE p!O s o$ 5 00000!38 P PDR

2 section of Code Class 3 piping that cannot be isolated for completing a Code repair within the time period permitted in the limiting condition for operation of the affected system as specified in the plant Technical S>ecifications, and performance of a Code repair would require a plant slutdown.

2.0 BACKGROUND

On September 9.1997. at the North Anna Power Station. Unic 1. Virginia Electric and Power Company (hertafter referred to as the licensee) identified ten locations with evidence of possible >revious leakage, i.e., stains in sever. ASME Class 3 service water system (SWS) lines. a repair plan was developed and implemented for the affected lines. The four welds were repaired in accordance with the ASME Code requirements by September 25. 1997.

By letter datea October 13, 1997, pursuant to 10 CFR 50.55a(g)(6)(i), the licensee requested a relief from the ASME Code.Section X'. replacement requirements for the period of September 9.1997. through September 25, 1997.

The licensee based its request for relief on the results of a "through wall flaw" evaluation that was performed by the licensee in acccrdance with the guidelines and acceptance criteria contained in GL 90 05, 3.0 LICENSEE'S RELIEF REOUEST 3.1 Components for Which Relief is Reauested Weld # Line # Joint Tvoe 14W 2" WS-775 163 03 Socket Weld 53W 2"-WS-776 163 03 Socket Weld FW55 4"-WS-F65 163 03 Butt Weld FW67 4"-WS-47-163-03 Butt Weld FW83 3"-WS 75-163-03 Butt Weld FW65 4"-WS-56-163-03 Butt Weld FW61 4"-WS56-163 03 Butt Weld FW66 4"-WS 56-163-03 Butt Weld 8 4" WS H48-163 03 Butt Weld 11A 4"-WS H48-163 03 Butt Weld .

The above listed welds are ASME Code Class 3 moderate energy piping in the SWS. The 2" WS-775 163-03 is the cross connection between instrument air heat exchangers 2-IA E-1B and 2 1A E-10. The 2"-WS 776 163-03 is the cross-connection between instrument air heat exchangers 2-IA E-1A and 2-IA E-1B.

Line 4"-WS F65-163-03 is the return from Unit 1 air conditioning condenser.

Line 4" WS-47-163-03 provides cooling water to the Unit I charging aump lube oil coolers and ir.strument air heat exchangers. Line 3" WS 7516343 is the return line from the charging pump lube oil coolers. Line 4"-WS-56-163-03 is the return frcm the Unit 1 charging pump oil coolers and instrument air compressors. Line 4"-WS-H48-163-03 provides cooling water to the Unit 2 air conditioning condensers. The nominal operating pressure is 75 psig and operating temperature is 95'F.

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3.2 Section X1 Edition for North Anna 1 and 2 North Anna Unit 1 - 1983 Edition of the ASME Code.Section XI including Summer 1983 Addenda.

North Anna Unit 2 - 1986 Edition of the ASM Code,Section XI.

3.3 ASME Section XI Code Reauirement The ASME Code Section XI requires that repairs or replacements of ASME Code Class com>onents be performed in accordance with rules found in Articles IWA-4000 or 14A 7000, respectively. The intant of these rules serves to provide an acceptable _ means of restoring the str: :tural integrity of a degraded Code Class system back te the original design requirements, 3.4 Content of the Relief Reauest Relief is sought from performing a repair or replacement of the service water aiping per the requirements of Article IWA 4000 or IWA 7000, respectively.

Relief is being sought for the period of September 9,1997, through September 25, 1997, because performing a Code repair during that period was determined to be not practical. The licensee had accomplished permanent Code repairs for all welds by the end of that period.

3.5 Basis for Relief Request for relief has been submitted and alternatives to the Code requirements have been proposed by the licensee. The licensee has evaluated the flaws in accordance with the guidance provided in GL 90 05. Based upon the evaluation, it was established that the discovered flaws satisfy the criteria for non-Code repair as described in GL 90-05 and performing permanent repairs in accordance with the ASME Code during the period September 9,1997, through September 25, 1997, would have constituted an undue burden (create undue hardship) upon the licensee since the re) airs would have necessitated the unnecessary isolation of portions of SWS tlat are structurally sound and thus reduce the margin of safety-3.6 Licensee's Alternative proaram Duri9 the period of September 9,1997, through September 25, 1997, the SWS with the identified possible through wall fDiws was monitored by the licensee as follows,

1. Weekly visual monitoring of through wall flaws and leakage.

2. Radiographic examination of butt welds.

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4.0 STAFF EVALUATION AND CONCLUSIONS f i

4.1 Doerability Determination. Root Cause Analysis  !

and Structural Intearity Evaluation v The licensee determined that five locations on the SWS have a "through wall flaw" and analyzed them in accordance with the position stated in GL 90 05.  !

This system was constructed in accordance with the requirements of ASME Code. .;

Class 3. Based on the radiographic testing (RT) examination' data, the flaws  ;

were determined to be small voids surrounded by exfoliation, which is typical 3

-of microbiologically induced corrosion (MIC). No other type of-operationally i caused defects were identified by the RT. The licensee evaluated the  !

structural integrity of the welds based on the radiographic examination and  ;

determined the following: (1) Weld 8 on line 4" WS H48 163-03 and weld FW65 .

on line 4"-WS 56 163 03 did not meet the assessment requirements of GL 90 05. t Weld 8 was replaced on September 23. 1997. 2 days after the weld was I radiographed and removed from service. Weld FW65 was replaced on  !

S9ptember 16. 1997: (2) Radiography of socket welds 14W on line 2" WS-775-163 03 and 53W on line 2" WS 776 163 03 was not attempted since radiographs of socket welds do not yield meaningful results. The lines were removed from ,

service after theand the socket evidence weldswas of leakage were replaced 3) detected: by(September Weld FW67 on25. line1997, 4"-WS16 47-days 163 03 weld FW83 on line 3 -WS-75 163 03, weld FW61 on line 4" WS 56 163 03.

and weld FW66 on line 4"-WS56-163 03 showed evidence of acceptable MIC as determined by radiography and structural integrity analyses and the welds were replaced on September 16, 1997: and (4) Weld 11A on line 4" WS H48 163-03  ;

showed evidence of acceptable MIC as determined by radiography and structural integrity analyses. The weld was re) laced. however. on September 23, 1997.

Weld FW55 on line 4" WS F65 163 03 slowed no evidence of MIC on the radiogra However,phs and,was the weld therefore, replacedno on structural-integrity September 23, 1997.analysis was performed.

4.2 Auamented Insoection ,

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-To assers the overall degradation of the SWS, augmented radiogra) hic examination was performed on five additional locations on lines laving"the r same function. Three of the five welds. FW59. FW60 and FW73 on line 4 -WS- '

F65-163 03, did not show evidence of MIC on radiographs and were not replaced.

Weld F74 on line 4" WS F65 163 03 had evidence of MIC but showed no evidence of through wall leakage, i.e.. stains. Weld F74 was found structurally 1

- acceptable by radiography and structural integrity evaluation and was not replaced. Weld FW56 on line 4"-WS-F65163-03 was replaced for ease of construction, since it was on the same elbow as FW55. which was replaced.

4,3 Prooosed Temoorary Non-Code Reoair and Monitorina Provisions During the period September 9,1997, through September 25, 1997, the licensee-performed weekly 'visaal monitoring of all areas with possible evidence of ieakage. The areas met the criteria for flooding and spraying consequences

'for structural.inttgrity. 1

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5 4.4 StaffConclusions The staff has determined that the licensee's flaw evaluation has been consistent with the guidelines and acceptance criteria of GL 90 05. The '

staff therefore, finds the licensee's structural integrity and operability t assessments to be acceptable. During the period of September 9,1997, through >

September 25. 1997. the welds were monitored by plant personnel and the flaws '

were repaired by September 25, 1997.

Furthermore, the staff finds that performance of an immediate Code repair during the period September 9,1997. -through September 25. 1997, would have resulted in hardship without a compens6 ting increase in the level of quality and safety. An innediate repair would have necessitated the isolation of

. portions of the SWS that are otherwise structurally sound and capable of performing their intended safety function, and would not have been in the best  !

interest of lant safety.-given the small magnitude of-the flaw and the

• licensee'sa$ternativeprogram.

Accordingly, relief is authorized pursuant to 10 CFR 50.55a(a)(3)(11).

Principal Contributor: P. Patnaik >

1 Date: January 15. 1998 r

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