ML110950406
| ML110950406 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 04/19/2011 |
| From: | Justin Poole Watts Bar Special Projects Branch |
| To: | Bhatnagar A Tennessee Valley Authority |
| Poole Justin/DORL/ 301-415-2048 | |
| References | |
| TAC MD6726, GL-04-002 | |
| Download: ML110950406 (4) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 April 19, 2011 Mr. Ashok S. Bhatnagar Senior Vice President Nuclear Generation Development and Construction Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801
SUBJECT:
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)
Dear Mr. Bhatnagar:
By letter dated March 4, 2011 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML110680248), the Tennessee Valley Authority (TVA) submitted its response to Generic Letter 2004-02 "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors," for Watts Bar Nuclear Plant, Unit 2. This submittal supersedes a previous response letter dated September 10, 2010 (ADAMS Accession No. ML102580175).
The U.S. Nuclear Regulatory Commission staff has reviewed the information provided by TVA and finds that additional information is needed to complete its review. The specific questions are in the enclosed request for additional information.
A response is required within 15 days of receipt of this letter as agreed to by your staff. If you cannot provide your response within the required time, please provide a letter to the NRC staff with the reason and a new date for your response.
If you should have any questions, please contact me at 301-415-2048.
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c::::.-- Justin C. Poole, Project Manager Watts Bar Special Projects Branch Division of Operating Reactor licensing Office of Nuclear Reactor Regulation Docket No. 50-391
Enclosure:
Request for Additional Information cc w/encl: Distribution via Listserv
REQUEST FOR ADDITIONAL INFROMATION WATTS BAR NUCLEAR PLANT, UNIT 2 GENERIC LETTER 2004-02 TENNESSEE VALLEY AUTHORITY DOCKET NO. 50-391 EMCB RAI1 In response to Item 3.k.1 of the Watts Bar Nuclear Plant (WBN), Unit 2, supplemental Generic Letter (GL) 2004-02 response (Reference 1), four out of the six load combinations for which the strainers were structurally qualified include loads due to either an operating basis earthquake (OBE) or a safe shutdown earthquake (SSE). However, no information was provided regarding the structural damping values used in the seismic analyses of the strainers, including their individual components, as part of the structural qualification of these components. Please provide the OBE and SSE damping values used for the strainer structures in the aforementioned analyses.
EMCB RAI2 Note 3 accompanying the loading combinations in Reference 1, which were considered in the structural analyses of the WBN Unit 2 sump strainers, indicates that loads due to jet impingement and debris impact were not considered in the final strainer design. The response to Item 3.k.3 of the WBN Unit 2 supplemental GL 2004-02 response clearly articulates that loads due to jet impingement are not credible, due to the location of the sump strainers.
However, there is little justification for neglecting the postulated loads due to debris impact.
Please provide additional justification and/or explanation regarding the exclusion of debris impact loads from the applicable loading combinations considered in response to Item 3.k.1.
EMCB RAI3 Note 6 accompanying the aforementioned loading combinations considered in the structural analyses of the WBN Unit 2 sump strainers, indicates that loads due to hydrostatic or hydrodynamic effects were not considered in the final strainer design. There is no accompanying justification for the exclusion of the effects of these loads in the sump strainer structural analyses. Please provide additional justification regarding the exclusion of hydrostatic and hydrodynamic loads. This justification should include, but not be limited to, whether submergence, sump strainer construction, or the bounding of these effects by other loads account for the absence of hydrostatic and hydrodynamic loads in the current structural analyses.
Enclosure
- 2 Reference Letter from D. Stinson, Tennessee Valley Authority, to Nuclear Regulatory Commission Document Control Desk, "Watts Bar Nuclear Plant (WBN) Unit 2 - Response to Generic Letter (GL) 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors," dated March 4,2011 (ADAMS Accession No. ML110680248).
April 19, 2011 Mr. Ashok S. Bhatnagar Senior Vice President Nuclear Generation Development and Construction Tennessee Valley Authority 6A Lookout Place 11 01 Market Street Chattanooga, TN 37402-2801 SUB~IECT:
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)
Dear Mr. Bhatnagar:
By letter dated March 4, 2011 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML110680248), the Tennessee Valley Authority (TVA) submitted its response to Generic Letter 2004-02 "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors," for Watts Bar Nuclear Plant, Unit 2. This submittal supersedes a previous response letter dated September 10, 2010 (ADAMS Accession No. ML102580175).
The U.S. Nuclear Regulatory Commission staff has reviewed the information provided by TVA and finds that additional information is needed to complete its review. The specific questions are in the enclosed request for additional information.
A response is required within 15 days of receipt of this letter as agreed to by your staff. If you cannot provide your response within the required time, please provide a letter to the NRC staff with the reason and a new date for your response.
If you should have any questions, please contact me at 301-415-2048.
Sincerely, IRA!
Justin C. Poole, Project Manager Watts Bar Special Projects Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-391
Enclosure:
Request for Additional Information cc w/encl: Distribution via Listserv DISTRIBUTION:
RidsOgcRp Resource PUBLIC RidsNrrDorlLpwb Resource LPWB Reading File RidsNrrLABClayton Resource RidsAcrsAcnw_MailCTR Resource ADAMS Accession No ML110950406 RidsRgn2MailCenter Resource RidsNrrDeEmcb Resource RidsNrrPMWattsBar2 Resource WJessup, NRR OFFICE LPWB/PM LPWB/LA EMCB/BC OGC/NLO LPWB/BC NAME JPoole BClayton MKhanna DRoth SCampbeil DATE 4/12/11 4/12/11 4/13/11 4/19/11 4/19/11 OFFICIAL AGENCY RECORD