ML082530371

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Vermont Yankee July 2008 Evidentiary Hearing - Applicant Exhibit E4-20-VY, INPO Report OE-15860 (Calvert Cliffs)
ML082530371
Person / Time
Site: Calvert Cliffs, Vermont Yankee  Entergy icon.png
Issue date: 03/31/2003
From: Tippett W
Institute of Nuclear Power Operations (INPO)
To:
NRC/SECY/RAS
SECY RAS
References
06-849-03-LR, 50-271-LR, Entergy-Applicant-E4-20-VY, RAS M-335
Download: ML082530371 (3)


Text

Subject:

OE15860 - Main Steam Piping Experienced Significant Wall Erosion Around the Drain Slots at the End of the Main Steam Flow Venturi Date: Mon, 31 Mar 2003 13:59:43 -0500 From: "Tippett, Wendy \(CCNPP\)" <tippettwl@inponn.org>

Reply-To: ThomfordPA@inponn.org Organization: INPO Newsgroups: inpo.planteventreports.operatingexperiencereports

  • T ED ýN **

Subject:

0E15860 - Main Steam Piping Experienced Significant Wall Erosion Around the Drain Slots at the End of the Main Steam Flow Venturi Abstract: During the current Unit 2 Steam Generator Replacement.

Outage, Calvert Cliffs discovered significant wall erosion around the drain slots at the end of the Main Steam flow venturi of the main steam piping system.

Reason for Message: This section of main steam would not have been examined by the Flow Accelerated Corrosion Program. Additionally, the nameplate was installed over the drain slot. This would have also prevented ultra-sonic thickness (UT) readings from finding this erosion.

Event Date: ............. 3/14/2003 Unit Name: .............. Calvert Cliffs Unit 2 NSSS/A-E:................ CE/Bechtel Turbine Manufacturer: ... Westinghouse Maintenance Rule Applicability: Yes Component Information (as applicable): N/A

Description:

Main Steam piping was removed for the steam generator replacement outage and the internal pipe was examined. NDE found two areas of excessive wall loss. The venturi did not have the proper fnlet clearance allowing excessive steam flow around the outside of the venturi. One area was measured at 0.450-inches deep, pipe nominal wall is 1.13-inches and the code minimum is 0.950-inches, the 'other area was measured at 0.911-inches.

Causes: The inlet to the flow venturi is not welded to the pipe and is supposed to have a clearance gap of about 0.065-inches. The measured clearance was excessive with an average of about 0.197-inches. This excessive gap allowed excess flow around the outside of the venturi and adce.rated the flow though the outlet drain slot. This in turn

,.led-to the erosion of the pipe wall.

Corrective Actions: The venturi was removed from the inside of the main Steam pipe. A weld repair was necessary to the non-welded end of the venturi to restore all clearances to design acceptable measurements. The two areas of excessive wall loss were r'epa~irh+/-'aaI'n'.d'-':

the venturi reassembled. The nameplates were relocated sothat .,

baseline and follow-up UT readings can be taken to verify týhi serosion o s ,ion issue is corrected. These components were added to the-Fl-ow

Accelerated Corrosion Program. ,

...... ........ .." 7,'

C-7o-

DOCKETED USNRC August 12, 2008 (11:00am)

OFFICE OF SECRETARY RULEMAKINGS AND ADJUDICATIONS STAFF U.S. WUGLEP RIEGWLTORY COMMNIIrSION Inthe aw.of ~ .4~ ~ ~~ LLL DockertNo. 5.2:171 Oficial Ex.hibit No. F-Y-Z~m-lYý OFFERED by L Intervenor_ ,_,

NRqC iff Otlher_______

IDENTIMED c* Witness/Panel W~c4.

A/bmlio Tagkpow.x REDECTED WITHDRAWN

Safety Significance: The potential existed for a non-isolatable through wall steam leak to develop had the erosion gone undetected.

Subject:

0E15860 - Main Steam Piping Experienced Significant Wall Erosion Around the Drain Slots at the End of the Main Steam Flow Venturi N IC OF I D I *NFIDE Please note that access to Nuclear Network is restricted to organizations authorized by INPO. The information exchanged via this network is confidential and for the sole use of the authorized organization. Confidentiality is important to ensure the open and frank exchange of information among authorized organizations.

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Information

Contact:

Mark Hunter 410-495-4003