ML070650396
| ML070650396 | |
| Person / Time | |
|---|---|
| Site: | Surry  (DPR-032, DPR-037) |
| Issue date: | 03/08/2007 |
| From: | Siva Lingam NRC/NRR/ADRO/DORL/LPLII-1 |
| To: | Christian D Virginia Electric & Power Co (VEPCO) |
| Lingam, Siva NRR/DORL 415-1564 | |
| References | |
| TAC MA7480 | |
| Download: ML070650396 (9) | |
Text
March 8, 2007 Mr. David A. Christian Senior Vice President and Chief Nuclear Officer Virginia Electric and Power Company Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711
SUBJECT:
SURRY POWER STATION, UNIT 2, EXTENSION REQUEST OF COMPLETION DATE FOR CORRECTIVE ACTIONS REGARDING GENERIC LETTER 2004-02, POTENTIAL IMPACT OF DEBRIS BLOCKAGE ON EMERGENCY RECIRCULATION DURING DESIGN BASIS ACCIDENTS AT PRESSURIZED WATER REACTORS (TAC NO. MA7480)
Dear Mr. Christian:
In a letter dated January 11, 2007, Virginia Electric and Power Company (the licensee) requested an extension to the December 31, 2007, completion deadline for Generic Letter (GL) 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized Water Reactors, corrective actions for sump clogging issues at Surry Power Station, Unit 2 (Surry 2). The Nuclear Regulatory Commission (NRC) staff has determined that it is acceptable to extend the completion date for the installation of the replacement screens for Surry 2 until April 20, 2008. Enclosed with this letter are the results of the NRC staffs evaluation for granting this extension. Please note the suggested 30-day grace period on the Surry 2, April 20, 2008, outage commencement at the end of the enclosure.
If any substantive GL corrective action analytical results or technical details change in 2008 (e.g., during an outage in which GL corrective action modifications are completed), a GL supplemental response should be submitted by the licensee within 90 days of the change or outage completion.
Sincerely,
/RA/
Siva P. Lingam, Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-280 and 50-281
Enclosure:
Evaluation of Extension Request cc w/encl: See next page
March 8, 2007 Mr. David A. Christian Senior Vice President and Chief Nuclear Officer Virginia Electric and Power Company Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711
SUBJECT:
SURRY POWER STATION, UNIT NO. 2, EXTENSION REQUEST OF COMPLETION DATE FOR CORRECTIVE ACTIONS REGARDING GENERIC LETTER 2004-02, POTENTIAL IMPACT OF DEBRIS BLOCKAGE ON EMERGENCY RECIRCULATION DURING DESIGN BASIS ACCIDENTS AT PRESSURIZED WATER REACTORS (TAC NO. MA7480)
Dear Mr. Christian:
In a letter dated January 11, 2007, Virginia Electric and Power Company (the licensee) requested an extension to the December 31, 2007, completion deadline for Generic Letter (GL) 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized Water Reactors, corrective actions for sump clogging issues at Surry Power Station, Unit No. 2 (Surry 2). The Nuclear Regulatory Commission (NRC) staff has determined that it is acceptable to extend the completion date for the installation of the replacement screens for Surry 2 until April 20, 2008. Enclosed with this letter are the results of the NRC staffs evaluation for granting this extension. Please note the suggested 30-day grace period on the Surry 2, April 20, 2008, outage commencement at the end of the enclosure.
If any substantive GL corrective action analytical results or technical details change in 2008 (e.g., during an outage in which GL corrective action modifications are completed), a GL supplemental response should be submitted by the licensee within 90 days of the change or outage completion.
Sincerely,
/RA/
Siva P. Lingam, Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-280 and 50-281
Enclosure:
Evaluation of Extension Request cc w/encl: See next page DISTRIBUTION:
Public RidsAcrsAcnwMailCenter RidsOgcRp LPL2-1 R/F RidsNrrDssSsib(JGolla)
RidsRgn2MailCenter(EGuthrie)
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ADAMS Accession No. ML070650396
- transmitted by memo dated.
OFFICE NRR/LPL2-1/PM NRR/LPD2-1/LA NRR/SSIB/BC NRR/LPL2-1/BC NAME SLingam MOBrien MScott EMarinos DATE 3/8/07 3/8/07 2/27/07*
3/8/07 OFFICIAL RECORD COPY
Enclosure EVALUATION OF EXTENSION REQUEST GENERIC LETTER 2004-02 VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION, UNIT NO. 2 DOCKET NO. 50-281 In a January 11, 2007, letter, discussing corrective actions for Generic Letter (GL) 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized Water Reactors," dated September 13, 2004, Virginia Electric and Power Company (the licensee) requested that the GL 2004-02, December 31, 2007, corrective actions due date for Surry Power Station, Unit No. 2 (Surry 2) be extended to the Surry 2 spring 2008 refueling outage (designated S2-R-21), scheduled to start on April 20, 2008.
In Attachment 1 to its January 11, 2007, letter, the licensee stated that in 2006 during the Surry 2 fall refueling outage (RFO) it had already replaced the Surry 2 sump screen with a significantly larger one of new design having 3500 square feet surface area. This replaced the old strainer of 150 square feet. In addition to the work on the strainer, Surry 2 installed an incore sump room drain to reduce containment hold-up volume.
The licensee stated in its January 11, 2007, letter, that testing of the strainer has taken longer than expected. In addition, the licensee wants to assure that current uncertainties in the nuclear industry concerning the magnitude of chemical effects and the potential effect of fiber bypassing screens and blocking flow at the reactor core are addressed in the final design. The licensee desires to account for these remaining issues in the design prior to installing the final modification. Surry 1 and 2 strainer testing (excluding chemical effects) is scheduled to be completed in January 2007, and final strainer size adjustments will be made based on testing.
Although the final strainer size is not yet known, the licensee placed orders for replacement screens for Surry 2 sized at approximately 8400 square feet in surface area. However, the vendor for the strainers could not deliver all of the components to support full installation in the fall 2006 RFO. The licensee believes that the Surry 2 design for installation of the 8400 square feet strainer will provide adequate net positive suction head (NPSH) for the required pumps, and will structurally withstand impingement, missile loading, and differential pressure that occur during accident conditions. Adjustments to the current design may be required after testing is completed, and chemical and downstream effects are considered.
In its January 11, 2007, letter, the licensee described the following mitigative measures accomplished at Surry 2:
Recirculation spray (RS) actuation for suction source switchover from refueling water storage tank (RWST) to containment sump was changed from a timer to an RWST level switch, maximizing the volume of water in the sump prior to switch over; An incore sump room drain was added to reduce containment hold-up volume; and A 3500 square feet strainer was installed in place of the original 150 square feet strainer. This is a partial implementation of the final strainer of about 8400 square feet.
The licensee also cited the following conditions applicable to Surry 2 (as discussed in GL 2004-02):
The Surry 2 containment is compartmentalized, reducing debris transport; Surry 2 has about 30 minutes after the loss-of-coolant accident (LOCA) initiation for debris settling before switchover to the recirculation mode of operation; and The probabilities of LOCA initiating events (large and medium break LOCAs) are extremely low.
The licensee discussed qualitatively the risk impact of extending the time for completing the sump strainer modification at Surry 2 until its spring 2008 outage. The licensee stated that the GL 2004-02 assumptions regarding break probabilities, debris transport, and debris settling during an accident remain valid through the period of the extension. A specific probabilistic risk assessment for the extension was not performed.
The licensee stated that it had already implemented the following compensatory measures:
Several actions have been implemented to ensure containment cleanliness. These actions include provisions for cleanliness during containment close out following RFOs and for power entries into containment. The program incorporates the guidance of Nuclear Energy Institute (NEI) 02-01, Condition Assessment Guidelines: Debris Sources Inside [Pressurized Water Reactors] PWR Containments. The procedures require that no loose material that could migrate to the sump is left inside containment.
In support of the cleanliness program, walkdowns covering all areas of containment are required prior to RFO restart; Detailed sump inspections are performed during each refueling outage; and Operators are trained and provided guidance for continuous monitoring of RS and low head safety injection pump parameters including loss of NPSH. Training briefs on the issue are provided during operator requalification sessions to increase awareness of this potential issue.
The Nuclear Regulatory Commission (NRC) has confidence that the licensee has a plan that will result in the installation of modifications that provide acceptable strainer function with adequate margin for uncertainties. Further, the NRC has concluded that the licensee has put mitigation measures in place to adequately reduce the risk for the requested short extension period, and that it is therefore acceptable to extend the completion date for the corrective actions for the issues discussed in GL 2004-02 until the completion of the Surry 2 spring 2008 refueling outage, currently scheduled to begin on April 20, 2008. Should the licensee elect to begin the Surry 2 outage more than 30 days after April 20, 2008, the licensee will need to provide the NRC additional justification for further delay in completing corrective actions for GL 2004-02. A PWR licensee with an approved Generic Safety Issue (GSI)-191 extension into 2008 or beyond should send in an "as complete as possible" GL 2004-02 supplemental and/or request for additional information response by December 31, 2007.
Surry Power Station, Units 1 & 2 cc:
Mr. David A. Christian Senior Vice President and Chief Nuclear Officer Virginia Electrical and Power Company Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711 Ms. Lillian M. Cuoco, Esq.
Senior Counsel Dominion Resources Services, Inc.
Building 475, 5th Floor Rope Ferry Road Waterford, Connecticut 06385 Mr. Donald E. Jernigan Site Vice President Surry Power Station Virginia Electric and Power Company 5570 Hog Island Road Surry, Virginia 23883-0315 Senior Resident Inspector Surry Power Station U. S. Nuclear Regulatory Commission 5850 Hog Island Road Surry, Virginia 23883 Chairman Board of Supervisors of Surry County Surry County Courthouse Surry, Virginia 23683 Dr. W. T. Lough Virginia State Corporation Commission Division of Energy Regulation Post Office Box 1197 Richmond, Virginia 23218 Dr. Robert B. Stroube, MD, MPH State Health Commissioner Office of the Commissioner Virginia Department of Health Post Office Box 2448 Richmond, Virginia 23218 Office of the Attorney General Commonwealth of Virginia 900 East Main Street Richmond, Virginia 23219 Mr. Chris L. Funderburk, Director Nuclear Licensing & Operations Support Dominion Resources Services, Inc.
Innsbrook Technical Center 5000 Dominion Blvd.
Glen Allen, Virginia 23060-6711