ML081430004
| ML081430004 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 05/19/2008 |
| From: | Bajestani M Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| GL-04-002, TAC MD6726 | |
| Download: ML081430004 (5) | |
Text
Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381-2000 May 19, 2008 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Stop: OWFN P1-35 Washington, D.C. 20555-0001 Gentlemen:
In the Matter of
)
Tennessee Valley Authority
)
Docket No. 50-391 WATTS BAR NUCLEAR PLANT (WBN) - UNIT 2 - REQUEST FOR ADDITIONAL INFORMATION REGARDING RESPONSE TO GENERIC LETTER 2004-02, POTENTIAL IMPACT OF DEBRIS BLOCKAGE ON EMERGENCY RECIRCULATION DURING DESIGN BASIS ACCIDENTS AT PRESSURIZED WATER REACTORS (TAC NO. MD6726)
References:
1.
NRC letter dated March 31, 2008, "Watts Bar Nuclear Plant, Unit 2 -
Request for Additional Information Regarding Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors (TAC NO. MD6726)"
- 2. TVA letter dated September 7, 2007, 'Watts Bar Nuclear Plant (WBN) -
Unit 2 - Initial Responses to Bulletins and Generic Letters" The purpose of this letter is to respond to an NRC request for additional information (Reference 1) regarding the WBN Unit 2 steam generator coating. TVA's original response to the Generic Letter was submitted on September 7, 2007 (Reference 2).
The WBN Unit 2 steam generators are Westinghouse Model D3 generators. They are of the same design as the original WBN Unit 1 steam generators that were in service from May 1996 until September 2006. The WBN Unit 2 steam generators have never been in service. provides the NRC request and TVA's response. Enclosure 2 provides the listing of open actions required for licensing made in Enclosure 1.
U.S. Nuclear Regulatory Commission Page 2 May 19, 2008 I declare under penalty of perjury that the foregoing is true and correct. Executed on the 1 9 th day of May, 2008.
If you have any questions, please contact me at (423) 365-2351.
Sincerely, Masoud j'estani Watts B* nit 2 Vice President Enclosures cc (Enclosures):
Lakshminarasimh Raghavan U.S. Nuclear Regulatory Commission MS 08H4A One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2738 Patrick Milano, Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2738 Loren R. Plisco, Deputy Regional Administrator for Construction U. S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center, Suite 23T85 61 Forsyth Street, SW, Atlanta, Georgia 30303-8931 U. S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, Georgia 30303-8931 NRC Resident Inspector Unit 2 Watts Bar Nuclear Plant 1260 Nuclear Plant Road Spring City, Tennessee 37381 Response to NRC Request for Additional Information Regarding Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized Water Reactors NRC Question: In its response for GL 2004-02, TVA indicates that the WBN 2 steam generators (SGs) are coated. Describe the coating material on the SGs, and state whether the coating material is qualified for design-basis accident conditions. Also, does TVA intend to leave the coating on the SGs?
TVA Answer: The SGs are coated with Carboline T
M 4674. In the final WBN Unit 2 configuration, the Carboline T
M 4674 coating is underneath Reflective Metal Insulation (RMI). This coating is recommended for the protection of the exterior of equipment with elevated temperature steel surfaces. CarbolineTM 4674 is a high temperature silicone that is not design basis accident qualified and is assumed to fail if the RMI that encapsulates it fails.
For WBN Unit 1, TVA performed an analysis to predict the type, quantity, and size distribution of debris that would be generated should a high energy line break requiring recirculation through the emergency sump ever occur at Watts Bar Unit 1. The analysis was submitted as part of the WBN Unit 1 closure for Generic Letter 2004-02 (Reference 1). The configuration analyzed in the TVA's Watts Bar Reactor Building GSI-191 Debris Generation Calculation (ALION-CAL-TVA-2739-03) for WBN Unit 1 is the same as WBN Unit 2 (RMI with Carboline TM 4674 coating underneath). In this calculation, four cases were postulated for breaks in the crossover leg piping at the base of each of the SGs. These breaks are considered to be bounding for all loss of coolant accidents that could be postulated for WBN.
In Reference 2, TVA committed to install new sump strainers on WBN Unit 2 identical to those installed on WBN Unit 1. TVA's commitment in Reference 2 will ensure that the debris generation analysis discussed above is applicable to WBN Unit 2. As part of the WBN Unit 2 modification, TVA will perform the necessary containment walkdowns and analysis to confirm that the debris generation study, debris transport analysis, chemical effects analysis, and downstream effects analysis apply to the WBN Unit 2 conditions.
As the CarbolineTM 4674 coating is a relatively small source of debris, TVA intends to leave the Carboline TM 4674 coating on the WBN Unit 2 SGs.
TVA will provide a closure document similar to Reference 1 for WBN Unit 2 prior to fuel load.
References:
- 1. TVA letter dated March 31, 2008, "Watts Bar Nuclear Plant (WBN) Unit 1 -
Supplemental Response to Nuclear Regulatory Commission (NRC)
Generic Letter (GL) 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors (PWR) - Notice of Completion (TAC NO. MC4730)"
- 2. TVA letter dated September 7, 2007, "Watts Bar Nuclear Plant (WBN) -
Unit 2'- Initial Responses to Bulletins and Generic Letters" Open Actions Required for Licensing
- 1. TVA will provide a closure document similar to Reference 1 for WBN Unit 2 GL 2004-02 prior to.fuel load.