ML042870314

Potential Foreseeable Bypass Notification

ML042870314
Person / Time
Site:	Sequoyah
Issue date:	10/05/2004
From:	Howard S Tennessee Valley Authority
To:	Davis P Office of Nuclear Reactor Regulation, State of TN, Dept of Environment & Conservation, Div of Solid Waste Mgmt
References
TN0026450
Download: ML042870314 (3)

Text

Tennessee Valley Authority, Post Office Box 2000, Soddy-Daisy, Tennessee 37379-2000 October 5, 2004 State of Tennessee Department of Environment and Conservation Division of Water Pollution Control Enforcement & Compliance Section 6th Floor, L&C Annex 401 Church Street Nashville, Tennessee 37243-1534 Attention: Mr. Paul E. Davis, Director

Dear Mr. Davis:

SEQUOYAH NUCLEAR PLANT - POTENTIAL FORESEEABLE BYPASS NOTIFICATION As required by Sequoyah (SQN) NPDES Permit No. TN0026450 Part II C.6., this is to notify the Division of Water Pollution Control of a potential foreseeable bypass. SQN believes that the three conditions stated in Part II C.6.b.i through Part 11 C.6.b.iii have been met.

On April 7, 2004, Sequoyah personnel performing routine NPDES compliance sampling noticed diversionary flow in the Tennessee River. It was later determined that the diversionary flow was caused by an unforeseeable breech of one of the diffuser pipe manholes (man ways). [Reference April 12, 2004 letter on Sequoyah Nuclear Plant - Diffuser Line Manhole Breach to Mr. Paul E.

Davis from Stephanie A. Howard]

In response to the discovery of the breach in the diffuser line to Outfall 101 at SQN NPDES Permit No. TN0026450, SQN will be performing maintenance on the nine man way covers of the two Diffuser Pond pipes. This work is scheduled for October 25-November 9, 2004. Each diffuser pipe has a 3 ft. by 3 ft. man way provided every 280 ft. apart. The 16 ft. diameter downstream diffuser pipe has four man ways and the 17 ft. diameter upstream diffuser pipe has five man ways. Each man way presently has a cover attached with two hinges and two heavy duty bolt type latches. This project will provide an alternate man way cover. The design function of the man way cover is to provide access to the diffuser pipe for initial installation and maintenance activities and to remain closed during operation to ensure discharge flow through the diffuser section of the pipe into the mixing zone. The alternate man way cover will be mounted to the inside of the pipe; therefore the water pressure inside the diffuser pipe will compress the

cover to the frame ensuring a tight seal. The alternate man way cover is designed to remain closed during operation.

Liquid effluent from SQN flows into the Tennessee River from the Diffuser Pond through a system of diffuser pipes located at Tennessee River Mile (TRM) 483.65. Two corrugated pipes (16 ft. diameter and 17 ft. diameter) comprise the diffuser system and extend under the Diffuser Pond dike into the river channel. The two pipes are set alongside each other (approx. 25 ft. apart) on the river bottom. Each diffuser pipe has a 350 ft. section through which flow is discharged into the river into the mixing zone. A sluice gate is provided which allows one diffuser pipe to be isolated if necessary. While each man way cover is being replaced, the corresponding diffuser pipe sluice gate will be closed.

The potential foreseeable bypass may occur while replacing the first two man way covers (four total) of each diffuser pipe since they are located outside of the mixing zone. Although SQN plans to close the sluice gate and therefore stop flow to the diffuser pipe man ways to be worked on, there is a small chance that the sluice gate would need to be opened prior to the completion of the man way repair. This would result in a breech similar to that which took place in April 2004.

Since Unit 1 will be in a refueling outage at the time of the repair, condenser circulating water (CCW) discharge flow will be approximately half of that in April 2004. It is not expected that the Diffuser Pond elevation will rise to a level that the sluice gate would need to be opened in order to drain the pond. If a breech does occur, SQN will contact the Chattanooga Environmental Assistance Center immediately.

Tennessee River at Sequoyah Nuclear Plant COl M

Please contact me at (423) 843-6700 if you have any questions or comments.

Sincerely, Stephanie A. Howard Principal Environmental Engineer Signatory Authority for J. Randy Douet Site Vice President Sequoyah Nuclear Plant cc: Chattanooga Environmental Assistance Center Division of Water Pollution Control State Office Building, Suite 550 540 McCallie Avenue Chattanooga, Tennessee 37402-2013 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555