ML20236M680

Submits Written Response to Augmented Insps Undertaken to Detect Leakage in EDG Lube Oil Piping & Provide Plan to Address long-term Operability Concerns for Piping

ML20236M680
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	07/07/1998
From:	Wanczyk R VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BVY-98-97, NUDOCS 9807140202
Download: ML20236M680 (2)

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VEltMONT YANKEE

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,, y NUCLEAR POWER CORPORATION 185 Old F*erry Road, Brattleboro, VT 05301 7002 (802) 257 5271 July 7,1998 BVY 98-97 U.S. Nuclear Regulatory Commission A'ITN: Document Control Desk Washington, DC 20555

Reference:

(a) letter, USNRC to VYNPC, Cracking of EDG Lube Oil Piping at Vermont Yankee, NVY 98-68, dated May 8,1998

Subject:

Venc9at Yankee Nuclear Power Station License No. DPR-28 (Docket No. 50-271)

Augmeated Inspection Measures and Assurance of Long-Term Opers.bility for Vermont Yankee EDG Lube Oil Piping

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. Reference (a) requested Vermont Yankee to provide written confirmation of the augiaented inspections undertaken to detect leakage in the subject piping, and to provide our plan to address long-term operability concerns for the piping. The following is our response to each of these 1

issues:

Anemented inmaction Maiences Current operating and surveillance procedures ensure that the Emergency Diesel Generator (EDG) piping is monitored for any possible leakage, both during normal standby conditions and while operating. The standing work control documents which provide for post-test visual inspection of the EDGs by Maintenance personnel have been revised to specify completion of the inspection within eighteen (18) hours following each scheduled diesel mn, vice the previously established thirty-six hour interval. ~ In addition, instructions have been placed in the Operadons Department Night Orders to re-emphasize the possibility of a leak occurring in the diesel generator lube oil piping, and to reaffirm management's expectations for monitoring of the diesels for any possible leakage due to the EDG piping concerns. These changes ensure that the presence of a leak will be promptly identified and dispositioned, and serve to enhance the inspeciion and surveillance activities already beirq performed.

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. A==nranca of Ione-Term Operability l

Vermont Yankee is closely monitoring the progress of the OEM's (Coltec/Fairbanks Morse Engine Division) Part 21 investigation through our participation in FM Diesel Generator Owners Group activities. We are in possession of Coltec's supplemental Part 21 notification letters

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h-- - ;ne, respectively, the results of burst testing and summary results of weld joint tensile o

testing performed on samples of the subject piping; in addition, metallurgical examinations were c(D i

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9907140202 990707 PDR ADOCK 05000271 G

PDR

I VERMONT YANKEE NUCLEAR POWER CORPORATION I

July 7,1998 o

Page 2 completed and are pending analysis.

Although definitive engineering analyses of the metallurgical results have not yet been completed, Coltec's preliminary conclusion is that the burst testing " proved that the welding of the joints, even though not full penetration, were (sic) adequate for the service intended and that no steps need to be taken to replace or rework piping runs in the field." The subsequent tensile testing was also cited as supporting an initial conclusion that the weld joints were of adequate strength for the application. - Previous independent load testing conducted by Vermont Yankee, which included both axial and bending loads, was corroborated by Coltec's flodings. Until the full scope of testing is evaluated and documented, Vermont Yankee has no compelling technical reasons to doubt the validity of this interim conclusion, especially since the most highly stressed portion of the piping has already been replaced. Consequently, we will reserve any decision regarding further remedial action until Coltec's final Part 21 report is available. We will review the final report upon receipt and take appropriate action. For the present, the status of the EDG lube oil piping remains a high priority issue within our corrective action program, and is subject to the provisions of a Basis for Maintaining Operation (BMO) reinforcing that position.

We also want to take this opportunity to clarify certain statements made in the Task Interface Agreement document attated to Reference (a). First, the statement that "The licensee has...

added some additional supports..." is not correct; no additional supports were added to the affected piping. Second, the code chosen for use in evaluation of the subject piping was the ANSI B31.1 Code. This code was chosen to maintain consistency with existing analyses of plant piping of similar safety classification (SC3). We believe that the reference on page 5 to ASME Section III, Subsection NB, is in error (as is the general reference dzele to the ASME Code). Given the safety classification of this piping and application of da ANSI B31.1 Code, the most appropriate cross-reference to the ASME Section III Code would be Subsection ND.

With this understanding, the appropriate Subsection ND code equations representing Sustained and Occasional load cases would be Equations 8 and 9. Note that tle reference to Equations 11 and 12 in the letter is compatible with the ANSI B31.1 terminology.

We trust that the information provided is acceptable; however, should you have any questions on this matter, please contact this office.

Sincerely, YERMoNT YANKEE NUCLEAR POWER Co?J' ORATION p[d%bb W

.Name Robert J. Wanczyk Director of Safety and Regulatory Affairs cc:

USNRC Region 1 Administrator j

USNRC Resident Inspector - VYNPS USNRC Project Manager - VYNPS VT Department of Public Service