ML20043H942

Forwards Proprietary WCAP-12351, North Anna Unit 1 Evaluation for Tube Vibration Induced Fatigue, Per Bulletin 89-001, Failure of Westinghouse Steam Generator Tube Mechanical Plugs. Rept Withheld (Ref 10CFR2.790)

ML20043H942
Person / Time
Site:	North Anna
Issue date:	06/21/1990
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML19298E182	List: ML20043H942 ML20043H943
References
90-274, IEB-89-001, IEB-89-1, NUDOCS 9006270111
Download: ML20043H942 (10)

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Vinoisir lu.urruir Asp Powan Coweruv Itic u n o x u, VIH OI M A UUUM June 21,1990 U.S. Nuclear Re0ulatory Commission Serial No.90-274 _

Attention: Document Control Desk NL&P/JYR Washington, D.C. 20555 Docket No. 50 338 -

License No. NPF 4 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY I NORTH ANNA POWER STATION UNIT 1 STEAM GENERATOR TUBE PLUG REPAIR AND L-SENTINELLY PLUGGED TUBE RECOVERY NRC Bulletin 89 01, dated May 15,1989, entitled " Failure of Westinghouse Steam Generator Tube Mechanical Plugs," required licensees to determine whether certain mechanical plugs supplied by Westinghouse were installed in steam generators and, g

if so, implement an action plan to ensure that these plugs would continue to provide -

adequate assurance of reactor coolant system (RCS) pressure boundary integrity i under normal operating, transient, and postulated accident conditions. NRC Bulletin -

89 01 identified the plug failure susceptibility as a result of the investigation into the -

North Anna Unit 1 1989 tube leak event. During the North Anna Unit 1 1989 refueling outage, extensive maintenance activities were completed to resolve the plug -

degradation issues and are described in detail in the North Anna Plug Top Release Event Report dated May 25,1989. The purpose of this letter is to inform you of our plans for the 1991 Unit 1 refueling and provide the technical basis for those plans.

Consistent with Bulletin 89-01 requirements, we intend to address the remaining sentinelly related, hot log plugs during our 1991 refueling outage. These tubes were preventively plugged as part of our remedial actions resulting from the July 15,1987 _

Steam Generator Tube Rupture. Current analysis methods have more definitively identified the tubes potentially susceptible to fatigue. As a result, we also intend to remove the cold leg plugs and return many of these tubes to service. Attachment 1 to this letter contains more detailed information on our specific plans and actions to date, while Attachment 2 contains the detailed technical basis that supports our plans. -

Also, Attachment 2 of this letter contains information proprietary to Westinghouse Electric Corporation, it is supported by an affidavit signed by W(stinghouse, the owner of the information. The affidavit sets forth the basis on which the information may be -

withheld from public disclosure by the Commission and addrest es with specificity the considerations hsted in paragraph (b) (4) of 10 CFR Section 2.790 of the Commission's regulations.

p)Y'lY m.a :.n > , mt ('/j' uke pg / Mjos 7 ~~ 13. ,P?,p l u sic 3 w MW  :

Accordingly, it is respectfully requested that the information which is proprietary to Westinghouse be withheld from public disclosure in accordance with 10 CFR Section .

2.790 of the Commission's regulations.

Correspondence with respect to the proprietary aspects of the Application for Withholding or the supporting Westinghouse Affidavit should reference CAW 90 029 and should be addressed to R. A. Wiesemann, Manager of Regulatory & Legislative Affairs, Westinghouse Electric Corporation, P.O. Box 355, Pittsburgh, Pennsylvania

! 15230 0355.

Should you have any other questions or desire to arrange a meeting to discuss this topic, please do not hesitate to contact us.

Very truly yours, 1x W. L. Stewart Senior Vice President Nuclear Attachments

1. Unit 1 Steam Generator Tube Outage Plans and Actions 4

2. Westinghouse authorization letter, CAW 90 029, Proprietary Information Notice, and accompanying Affidavit.

3. 3 copies of WCAP 12251 entitled " North Anna Unit 1 Evaluation For Tube Vibration Induced Fatigue" (Proprietary).

4. 3 copies of WCAP-12252 entitled

• North Anna Unit 1 Evaluation For Tube Vibration Induced Fatigue" (Non Proprietary).

1 cc: U.S. Nuclear Regulatory Commission Region 11 l 101 Marietta Street, N.W. .-

Suite 2900 Atlanta, Georgia 30323 Mr. M. S. Lesser NRC Senior Resident Inspector

• North Anna Power Station 5

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ATTACHMEN'i i UNIT 1 STEAM GENERATOR TUBE

~ OUTAGE PLANS AND ACTIONS NORTH ANNA POWER STATION UNIT 1 l

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I introduction NRC Bulletin 89 01, dated May 15, 1989, entitled "Fcitute of Westinghouse Steam Generator Tube Mechanical Plugs," required licensees to determine whether certain mechanical plugs supplied by Westinghouse were installed in steam generators and, if so, implement an action plan to ensure that these plugs would continue to provide adequate assurance of reactor coolant system (RCS) pressure boundary integrity under normal operating, transient, and postulated accident conditions. NRC Bulletin 89-01 identified the plug failure susceptibility as a result of the investigation into the North Anna Unit 1 1989 tube leak event. During the North Anna Unit 1 1989 refueling outage, extensive maintenance activities were completed to resolve the plug degradation issues. Activities performed at North Anna in response to Bulletin 89 01 were completed consistent with the North Anna Plug Top Release Event Report (Revision 1) dated May 25, 1989, with the exception of one tube. Subsequent to the date of the May report, a hot leg plug in plug device was inadvertently damaged. This damaged device and plug were removed and a welded plug acceptably installed in the tube end. During the 1991 refueling outage,Bulletin 89-01 required that we address the susceptible sentinelly related hot leg plugs.

Pluaaina Methodoloav and Plans .

During the North Anna Unit 1 1987 steam generator related forced outage, a total of 16? tubes across the three steam generators were sentinelly plugged as a oreventive measure, which would provide early warning of a potential similar fatigee failure during the subsequent operation of the unit. Each of these tubes was removed from service with mechanical plugs later determined to be susceptible to the degradation described in NRC Bulletin 89 01.

As part of the North Anna Unit 1 1989 refueling outage, extensive steam generator maintenance activities were performed. These activities included installation of plug-in-plug devices or removal and replacement of tube plugs with suspect or undetermined heat numbers insta' led in conventionally plugged tubes. Additionally, dampeners were installad in tubes determined to be potentially susceptible to U bend f atig ue, including one tube with a sentinel plug that was determined to be susceptble to fatigue. The remaining 161 susceptible hot leg plugs in sentinelly plugged tubes were evaluated and determined acceptable for continuec operation. Our technical justification for leaving these plugs installed and our action plan for final removal of the plugs were provided

• *e in the North Anna Plug Top Release Event Report (Revision 1) dated May 25, 1989.

Consister.1 'vith our action plan, we intend to address the remaining 161 sentineHy plugged tubes in the upcoming 1991 refueling outage. However, it is now our intent to remove both the susceptible hot leg plugs and their companion cold leg sentinel plugs on 149 of the 161 tubes, then return these tubes to service. Additionally, we intend to address the remaining twelve (12) susceptible hot leg plugs either through removal and replacement or through the installation of a " plug in plug" device. Each tube intended for return to service will be subjected to eddy current testing prior to return to service.

The total number of tubes planned for return-to service per steam generator is listed below:

Steam Generator Number of Tubes A 80 8 11 C 58 .

Table 1 contains a Row, Column listing of the tubes sentinelly plugged in 1987 and planned for plug removal and return to service. Table 2 contains a listing of tubes that were identified as potentially susceptible to fatigue, potentially susceptible to fatigue with T hot reduction, or preventively plugged due to their proximity to the Row 9, Column 51 failed tube in the "C" steam generator.

These planned. and previously performed actions are based on a reevaluation of the North Anna 1 U bend fatigue analysis and include the impact of the recently implemented T-hot reduction program. This reevaluation was begun in late 1988 using the most recent methods' for defining anti vibration bar (AVB) position uncertainties and utilized a larger flow peaking test data base. The technical basis for the actions planned or previously performed are contained in Westinghouse WCAP-12351, entitled " North Anna Unit 1 Evaluation for Tube Vibration Induced Fatigue," enclosed.

I Summarv Currently, Virginia Electric and Power Company plans to remove both the susceptible hot leg plugs and their companion cold leg sentinel plugs and return these tubes to service after appropriate testing. Additionally, we intend to address the remaining i susceptible hot leg plugs either through removal and replacement or through the installation of a " plug in plug" device with each tube subjected to testing prior to return-to service.

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', ** j TABLE 1 Tubes Planned for Return to Service I

STEAM GENERATOR A ftQif COLUMN flQ){ COLUMN flux COLUMN I 9 2 9 38 12 53 .

10 2 10 38 9 54 )

8 3 11 38 10 54 )

10 3 10 39 11 54 i 11 3 11 39 12 54 12 3 9 40 9 59 13 3 10 40 10 59 i 8 4 11 40 11 59 10 4 9 41 9 60 11 4 10 41 .11. 60 ,

10 5 11 41 9 61

! .11 5 9 42 10 61 10 7 9 43 11 61 i 11 7 lb 44 9 66 10 8 9 45 10 72 -

11 8 10 45 10 73 9 14 9 46 10 76 9 .24 10 46 10 77 9 32 11 46 10 78 .

10 32 9 47 11 78 10 33 10 47- 12 78 i 9 35 11 47 10 79 10 35 9 48 11 79 10 36 10 52 12 79 i 10 37 11 52 10 93 11 37 12 52 11 93 1 10 53 12 93  !

STEAM GENERATOR B ILQ){ COLVMN ftQ){ [.011M [

9 23 11 2 9 30 11 3 .

9 44 11 93 .

10- 2 12 3 10 93 12 93 13 3 ,

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TABLE I (Continued)

Tubes Planned for Return to Service STEAM GENERATOR C M COLUMN RQW COLUMN M COLUMN .

10 2 10 29 9 49 11 2 9 30 9 56 12 2 10 30 9 61 j 10 3 11 30 9 63 10 4 9 31 9 64 10 5 10 31 9 65 10 6 11 31 9 66- ,

9 15 10 32 9 67 9 17 11 32 9 68 10 18 9 37 9 75 9 19 9 42 10 93 10 19 9 44 11 93

10. 20 9 45 12 93 10 22 10 45 l 10 23 9 46 I 9 24 10 46 l 10 24 9 47 11 24 10 47 9 25 10 48 10 25 11 25 l 10 26 11 26 10 27 9 i'8 10 28 i=

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TABLE 2 1

Tubes Potentially Susceptible to Fatigue, Potentially Susceptible to Fatigue with T-Hot Reduction, or Remaining Preventively Plugged Due to Proximity to Failed Tube.

STEAM GENERATOR A M COLUMN COMMENTS 9 60 Tube was sentinelly plugged in 1987 and is susceptible to fatigue with T-hot reduction after ten years service. Due to expected short remaining life of steam generator, plan to return this tube to service.

STEAM GENERATOR B M [qlM COMMENTS 9 34 Tube was sentinelly plugged in 1987, in 1989 hot and cold leg plugs were removed, dampeners installed and tube replugged with sentinel plug in cold leg.

9 35 Tubes were left in service after 1987. In 1989, l 9 46 dampeners were installed and tubes plugged with sentinel plug in cold leg.

9 54 Tube is not plugged. Acceptable for.10 year service after implementation of T-hot reduction.

No action planned due to expected short remaining life of steam generators.

STEAM GENERATOR C M COLUMN COMMENTS 9 35 Tubes were left in service after 1987, in 1989, 9 60 dampeners were installed and tubes plugged with sentinel plug in cold leg.

8 50 These tubes were sentinelly plugged in 1987.

9 60 These tubes surround the failed tube R9, C51 and 10 50 tubes RIO and 11, CSI with eddy current 11 50 indications. The hot leg plugs will be addressed 12 50 during the 1991 refueling outage either thru plug 8 51 removal and replacement or insta.'lation of a 12 51 " plug-in-plug" device.

8 52-9 52 10 52 11 52 12 52

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ATTACHMENT 2 P

i WESTINGHOUSE PROPRIETARY INFORMATION NOTICE ,

and ACCOMPANYING AFFIDAVIT i.

NORTH ANNA POWER STATION UNIT 1 ,  ;

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