ML11136A092

OL - TVA Letter to NRC_04-21-11_X-750 Bolting_Withdrawl of Commitment

ML11136A092
Person / Time
Site:	Watts Bar
Issue date:	04/21/2011
From:	- No Known Affiliation
To:	Division of Operating Reactor Licensing
References
Download: ML11136A092 (5)

Text

WBN2Public Resource From: Boyd, Desiree L [dlboyd@tva.gov]

Sent: Thursday, April 21, 2011 9:11 AM To: Epperson, Dan; Poole, Justin; Raghavan, Rags; Milano, Patrick; Campbell, Stephen Cc: Crouch, William D; Hamill, Carol L; Boyd, Desiree L; Stockton, Rickey A

Subject:

TVA letter to NRC_04-21-11_X-750 bolting_Withdrawl of commitment Attachments: 04-21-11_X-750 bolting_Withdrawl of commitment_Final.pdf Please see attached TVA letter that was sent to the NRC today.

Thank You,

~*~*~*~*~*~*~*~*~*~*~*~*~*~*~

Désireé L. Boyd WBN 2 Licensing Support Sun Technical Services dlboyd@tva.gov 4233658764

~*~*~*~*~*~*~*~*~*~*~*~*~*~*~

1

Hearing Identifier: Watts_Bar_2_Operating_LA_Public Email Number: 356 Mail Envelope Properties (7AB41F650F76BD44B5BCAB7C0CCABFAF1DF52413)

Subject:

TVA letter to NRC_04-21-11_X-750 bolting_Withdrawl of commitment Sent Date: 4/21/2011 9:10:37 AM Received Date: 4/21/2011 9:11:16 AM From: Boyd, Desiree L Created By: dlboyd@tva.gov Recipients:

"Crouch, William D" <wdcrouch@tva.gov>

Tracking Status: None "Hamill, Carol L" <clhamill@tva.gov>

Tracking Status: None "Boyd, Desiree L" <dlboyd@tva.gov>

Tracking Status: None "Stockton, Rickey A" <rastockton@tva.gov>

Tracking Status: None "Epperson, Dan" <Dan.Epperson@nrc.gov>

Tracking Status: None "Poole, Justin" <Justin.Poole@nrc.gov>

Tracking Status: None "Raghavan, Rags" <Rags.Raghavan@nrc.gov>

Tracking Status: None "Milano, Patrick" <Patrick.Milano@nrc.gov>

Tracking Status: None "Campbell, Stephen" <Stephen.Campbell@nrc.gov>

Tracking Status: None Post Office: TVANUCXVS2.main.tva.gov Files Size Date & Time MESSAGE 341 4/21/2011 9:11:16 AM 04-21-11_X-750 bolting_Withdrawl of commitment_Final.pdf 84591 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received:

Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381-2000 April 21, 2011 10 CFR 50.34 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 2 NRC Docket No. 50-391

Subject:

WATTS BAR NUCLEAR PLANT (WBN) UNIT 2 - WITHDRAWAL OF A PREVIOUS COMMITMENT

Reference:

TVA letter dated June 28, 2010, Watts Bar Nuclear Plant (WBN) Unit 2 -

Request for Additional Information (RAI) Regarding Licensees Final Safety Analysis Report Amendment Related to Section 4.2.2, Reactor Vessel Internal Components (TAC No. ME2731)

The purpose of this letter is to withdraw a previous commitment made in the referenced letter.

In that letter, TVA committed to replace prior to Unit 2 operation the current Unit 2 clevis insert bolts to a design which uses X-750 alloy with a high temperature heat (HTH) treatment, rolled threads, and a larger radius on the undercut of the cap screw head. Upon further evaluation, TVA has determined that this replacement is unwarranted at this time.

The justification for this withdrawal stems from the fact that the bolting failure phenomenon has only known to have occurred at one unit in the industry. The phenomenon appears to be time based, and the breakage only occurs after many operating cycles. In discussions with personnel at the affected plant, TVA has learned that the cause is not yet known and that any change might be at best neutral to solving the problem. TVA has also confirmed via these discussions that bolting at the affected plants other unit does not have the same issue. In addition, WBN Unit 1 has operated with the same type bolting since 1995 with no failure of these bolts.

The initial NRC RAI cited the Staff Requirements Memorandum dated July 25, 2007 (ADAMS Accession No. ML093370274) directing TVA to look for opportunities to resolve issues where the unirradiated state of WBN Unit Bar 2 makes the issue easier to resolve. At this time, the root cause of the subject issue has not been determined, an industry resolution has not been established, the problem appears to be restricted to a single unit at another utility, and WBN

U.S. Nuclear Regulatory Commission Page 3 April 21, 2011 bcc: Stephen Campbell U.S. Nuclear Regulatory Commission MS 08H4A One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2738 Charles Casto, Deputy Regional Administrator for Construction U. S. Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, Georgia 30303-1257