ML071360480
| ML071360480 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 05/31/2007 |
| From: | Thomas Wengert NRC/NRR/ADRO/DORL/LPLIII-2 |
| To: | Bezilla M FirstEnergy Nuclear Operating Co |
| Wengert, Thomas NRR/DORL 415-4037 | |
| References | |
| GL-96-006, TAC M96803 | |
| Download: ML071360480 (6) | |
Text
May 31, 2007 Mark B. Bezilla Site Vice President FirstEnergy Nuclear Operating Company Davis-Besse Nuclear Power Station Mail Stop A-DB-3080 5501 N. State Route 2 Oak Harbor, OH 43449-9760
SUBJECT:
NRC RECEIPT OF DAVIS-BESSE NUCLEAR POWER STATION, UNIT NO. 1, RESPONSES TO GENERIC LETTER 96-06, ASSURANCE OF EQUIPMENT OPERABILITY AND CONTAINMENT INTEGRITY DURING DESIGN-BASIS ACCIDENT CONDITIONS (TAC NO. M96803)
Dear Mr. Bezilla:
On September 30, 1996, the U. S. Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 96-06, Assurance of Equipment Operability and Containment Integrity During Design-Basis Accident Conditions, (Agencywide Documents Access and Management System (ADAMS) Accession No. 9609250096). In GL 96-06, the NRC staff expressed concerns that cooling water systems serving the containment air coolers may (1) be exposed to the hydrodynamic effects of waterhammer during either a loss-of-coolant accident or a main steamline break, or (2) experience two-phase flow conditions during these postulated accidents.
The NRC staff also expressed concern that (3) thermally-induced overpressurization of isolated water-filled piping sections in containment could jeopardize the ability of accident mitigating systems to perform their safety functions and could also lead to a breach of containment integrity via bypass leakage. The NRC staff requested that the licensees assess these concerns, take certain actions as appropriate, and provide certain information to the NRC staff within specified times.
You provided responses to GL 96-06 for the Davis Besse Nuclear Power Station (DBNPS),
Unit No. 1 in letters dated January 28, 1997, (ADAMS Accession No. ML9702040224),
February 28, 1997 (ADAMS Accession No. ML9703100246), July 28, 1997 (ADAMS Accession No. ML9708050319), September 30, 1997 (ADAMS Accession No. ML9710070308), April 7, 1999 (ADAMS Accession No. ML9904130273), December 30, 2003 (ADAMS Accession No. ML040020052), April 15, 2005 (ADAMS Accession No. ML051100291), July 25, 2006 (ADAMS Accession No. ML062090103), and April 20, 2007 (ADAMS Accession No. ML071150077).
Waterhammer and Two-Phase Flow Subsequent to the issuance of GL 96-06, the Electric Power Research Institute (EPRI) developed an analytical methodology for evaluating the GL 96-06 waterhammer issue that was documented in EPRI Technical Reports 1003098 and 1006456 (previously known as EPRI Report TR-113594), and approved by the NRC staff in an evaluation dated April 3, 2002 (included as an Appendix to the EPRI Technical Reports). Section 3.3 of the NRC staffs safety evaluation (SE) requested that licensees who chose to use the EPRI methodology provide additional information to confirm that the EPRI methodology was properly applied and that
M. Bezilla 2 plant-specific risk considerations were consistent with the EPRI risk perspective; to justify any proposed exceptions to the EPRI methodology; and to provide any additional information that is required to address the GL 96-06 two-phase flow issue.
On August 14, 2003, while completing the GL 96-06 waterhammer evaluation, DBNPS experienced a loss of offsite power while shut down in Mode 5. This event caused a waterhammer to occur in the service water (SW) system that was more severe than expected based on the preliminary waterhammer analysis that had been completed, and consequently, you stated that a new waterhammer analysis as discussed in your letter dated July 25, 2006 was completed. The new waterhammer analysis used the EPRI rigid body analytical approach for evaluating the most limiting case, which you found to be bounded by a loss of power initiated column separation and closure waterhammer event. Using the EPRI approach, you stated that the modifications that were made in response to the August 2003 waterhammer event were adequate for resolving the waterhammer concerns that were discussed in GL 96-06.
These plant modifications included changing the containment air cooler (CAC) SW inlet and outlet valve control logic to ensure that voids in the CACs are filled slowly; installing inlet check valves and outlet vacuum breakers to minimize void formation in the event of a loss of offsite power concurrent with a loss of coolant accident; and, modifying piping supports to provide additional design margin for the GL 96-06 waterhammer events that are postulated to occur.
In a letter dated April 20, 2007, you provided the results of a risk assessment confirming that the plant-specific waterhammer risk is consistent with the EPRI risk perspective. Additionally, with respect to two-phase flow considerations, you determined that single phase flow will be restored at approximately the time the CACs are credited in the containment analysis and that any reduction in the initial effectiveness of the CACs will be inconsequential. Finally, you proposed no exceptions to the EPRI methodology.
Based on the information that was provided, the NRC staff is satisfied with your evaluation of the GL 96-06 waterhammer and two phase flow issues for the DBNPS. The waterhammer analysis is consistent with the approved EPRI methodology and you have adequately addressed the specific areas that are referred to in Section 3.3 of the NRC staffs safety evaluation as referenced above. Therefore, your resolution of the GL 96-06 waterhammer and two phase flow issues is acceptable.
While the NRC staff is satisfied with your resolution of the GL 96-06 waterhammer and two-phase flow issues, a detailed quantitative assessment of your waterhammer and two-phase flow analyses has not been performed, and your use and application of computer codes for performing these analyses has not been reviewed. Consequently, these areas could be the subject of future NRC inspection activities.
Thermal Overpressurization In a letter dated March 3, 2005 (ADAMS Accession No. ML050540613), the NRC staff notified you that your evaluation and proposed corrective actions provided an acceptable resolution for the issue of thermally-induced overpressurization of piping in containment. However, due to the recent piping modifications, affirmation of your responses was needed to verify that they were still valid. In your letter dated April 15, 2005, you stated that system changes that have already been completed do not appear to affect the previous response pertaining to thermally-induced
M. Bezilla 3 overpressurization of isolated water-filled piping sections in containment. You further stated that proposed future changes were to be completed during their fourteenth refueling outage (14RFO) and you committed to provide the requested response within 90 days following the completion of 14RFO. Following the completion of 14RFO, in a letter dated July 25, 2006, you stated that since the thermally-induced overpressurization issue was closed and not impacted by the recent changes, no updated response was necessary for that issue. Based on this information, the NRC staff has concluded that you have provided an acceptable resolution for the issue of thermally-induced overpressurization of piping in containment.
Based on the information discussed above, the NRC staff considers your responses to GL 96-06 to be complete subject to future NRC inspection activities as described above.
If you have questions regarding this letter, please contact me at (301) 415-4037.
Sincerely,
/RA/
Thomas J. Wengert, Project Manager Plant Licensing Branch III-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-346 cc: See next page
ML071360480 NRR-106 OFFICE LPL3-2/PM LPL3-2/LA PGCB/PM SBPB/BC EMCB/BC LPL3-2/BC NAME TWengert EWhitt JRobinson JSegala KManoly RGibbs DATE 5/24/07 5/24/07 5/24/07 5/25/07 5/29/07 5/31/07 Davis-Besse Nuclear Power Station, Unit 1 cc:
Manager, Site Regulatory Compliance Attorney General FirstEnergy Nuclear Operating Company Office of Attorney General Davis-Besse Nuclear Power Station 30 East Broad Street Mail Stop A-DB-3065 Columbus, OH 43216 5501 North State Route 2 Oak Harbor, OH 43449-9760 President, Board of County Commissioners of Ottawa County Director, Ohio Department of Commerce Port Clinton, OH 43252 Division of Industrial Compliance Bureau of Operations & Maintenance President, Board of County 6606 Tussing Road Commissioners of Lucas County P.O. Box 4009 One Government Center, Suite 800 Reynoldsburg, OH 43068-9009 Toledo, OH 43604-6506 Regional Administrator, Region III The Honorable Dennis J. Kucinich U.S. Nuclear Regulatory Commission United States House of Representatives Suite 210 Washington, D.C. 20515 2443 Warrenville Road Lisle, IL 60532-4352 The Honorable Dennis J. Kucinich United States House of Representatives Resident Inspector 14400 Detroit Avenue U.S. Nuclear Regulatory Commission Lakewood, OH 44107 5503 North State Route 2 Oak Harbor, OH 43449-9760 Joseph J. Hagan President and Chief Nuclear Officer Stephen Helmer FirstEnergy Nuclear Operating Company Supervisor, Technical Support Section Mail Stop A-GO-14 Bureau of Radiation Protection 76 South Main Street Ohio Department of Health Akron, OH 44308 35 East Chestnut Street, 7th Floor Columbus, OH 43215 David W. Jenkins, Attorney FirstEnergy Corporation Carol OClaire, Chief, Radiological Branch Mail Stop A-GO-15 Ohio Emergency Management Agency 76 South Main Street 2855 West Dublin Granville Road Akron, OH 44308 Columbus, OH 43235-2206 Danny L. Pace Zack A. Clayton Senior Vice President, Fleet Engineering DERR FirstEnergy Nuclear Operating Company Ohio Environmental Protection Agency Mail Stop A-GO-14 P.O. Box 1049 76 South Main Street Columbus, OH 43266-0149 Akron, OH 44308 State of Ohio Manager, Fleet Licensing Public Utilities Commission FirstEnergy Nuclear Operating Company 180 East Broad Street Mail Stop A-GO-2 Columbus, OH 43266-0573 76 South Main Street Akron, OH 44308
Davis-Besse Nuclear Power Station, Unit 1 cc:
Director, Fleet Regulatory Affairs FirstEnergy Nuclear Operating Company Mail Stop A-GO-2 76 South Main Street Akron, OH 44308 Jeannie M. Rinckel Vice President, Fleet Oversight FirstEnergy Nuclear Operating Company Mail Stop A-GO-14 76 South Main Street Akron, OH 44308 Richard Anderson Vice President, Nuclear Support FirstEnergy Nuclear Operating Company Mail Stop A-GO-14 76 South Main Street Akron, OH 44308 James H. Lash Senior Vice President of Operations and Chief Operating Officer FirstEnergy Nuclear Operating Company Mail Stop A-GO-14 76 South Main Street Akron, OH 44308