ML073520076

Approval of Extension Request for Corrective Actions GL 2004-02 Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized Water Reactors (TAC No. MC4719 & MC4720)

ML073520076
Person / Time
Site:	South Texas
Issue date:	12/19/2007
From:	Thadani M NRC/NRR/ADRO/DORL/LPLIV
To:	Sheppard J South Texas
Thadani, M C, NRR/DORL/LP4, 415-1476
References
TAC MC4719, TAC MC4720
Download: ML073520076 (8)

Text

December 19, 2007 Mr. James J. Sheppard President and Chief Executive Officer STP Nuclear Operating Company South Texas Project Electric Generating Station P. O. Box 330 Wadsworth, TX 77483

SUBJECT:

SOUTH TEXAS PROJECT, UNITS 1 AND 2 - APPROVAL OF EXTENSION REQUEST FOR CORRECTIVE ACTIONS RE: GENERIC LETTER 2004-02 "POTENTIAL IMPACT OF DEBRIS BLOCKAGE ON EMERGENCY RECIRCULATION DURING DESIGN BASIS ACCIDENTS AT PRESSURIZED WATER REACTORS," (TAC NOS. MC4719 AND MC4720)

Dear Mr. Sheppard:

By letter dated December 10, 2007, as supplemented by letter dated December 13, 2007, the STP Nuclear Operating Company (the licensee) submitted to the U.S. Nuclear Regulatory Commission (NRC) staff a request for extension of the South Texas Project (STP), Units 1 and 2, sump clogging corrective actions completion date of December 31, 2007, as required in Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized Water Reactors," to June 30, 2007.

The NRC staff has evaluated the licensees request. Based on its evaluation, the NRC staff concludes that the licensee has a reasonable plan for completion of corrective actions at STP, Units 1 and 2, that should result in acceptable strainer function with adequate margin for uncertainties. The NRC staff further concludes that the licensee has mitigation measures in place at STP, Units 1 and 2, to adequately reduce the risk for the requested extension period.

Therefore, the NRC staff finds that extension of the completion of corrective actions and modifications until June 30, 2008, is acceptable.

J. J. Sheppard The NRC staffs safety evaluation is enclosed. If you have any questions, please contact me at (301) 415-1476 or email mct@nrc.gov.

Sincerely,

/RA/

Mohan C. Thadani, Senior Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499

Enclosure:

Safety Evaluation cc w/encl: See next page

ML073520076 (*) SE input memo OFFICE DORL/LPL4/PM DORL/LPL4/LA DSS/SSIB/BC DORL/LPL4/BC NAME MThadani JBurkhardt MScott (*) THiltz DATE 12/19/07 12/19/07 12/14/07 12/19/07 South Texas Project, Units 1 and 2 12/5/2007 cc:

Senior Resident Inspector STP Nuclear Operating Company U.S. Nuclear Regulatory Commission P.O. Box 289, Mail Code: N5014 P.O. Box 289 Wadsworth, TX 77483 Wadsworth, TX 77483 C. T. Bowman, General Manager, Oversight C. M. Canady STP Nuclear Operating Company City of Austin P.O Box 289 Electric Utility Department Wadsworth, TX 77483 721 Barton Springs Road Austin, TX 78704 Ms. Marilyn Kistler Senior Staff Specialist, Licensing J. J. Nesrsta/R. K. Temple STP Nuclear Operating Company E. Alercon/Kevin Pollo P.O. Box 289, Mail Code 5014 CPS Energy Wadsworth, TX 77483 P.O. Box 1771 San Antonio, TX 78296 Environmental and Natural Resources Policy Director INPO P.O. Box 12428 Records Center Austin, TX 78711-3189 700 Galleria Parkway Atlanta, GA 30339-3064 Mr. Jon C. Wood Cox, Smith, & Matthews Regional Administrator, Region IV 112 East Pecan, Suite 1800 U.S. Nuclear Regulatory Commission San Antonio, TX 78205 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011 Director, Division of Compliance & Inspection Bureau of Radiation Control Steve Winn/Christie Jacobs Texas Department of State Health Services Eddy Daniels/Marty Ryan 1100 West 49th Street NRC Energy, Inc. Austin, TX 78756 211 Carnegie Center Princeton, NJ 08540 Mr. Ted Enos 4200 South Hulen Mr. Nate McDonald Suite 422 County Judge for Matagorda County Ft. Worth, TX 76109

\1700 7th Street, Room 301 Bay City, TX 77414 Mr. Brian Almon Public Utility Commission of Texas A. H. Gutterman, Esq. P.O. Box 13326 Morgan, Lewis & Bockius Austin, TX 78711-3326 1111 Pennsylvania Avenue, NW Washington, DC 20004 E. D. Halpin, Site Vice President STP Nuclear Operating Company South Texas Project Electric Generating Station P.O. Box 289 Wadsworth, TX 77483 S. M. Head, Manager, Licensing

South Texas Project, Units 1 and 2 12/5/2007 Ms. Susan M. Jablonski Office of Permitting, Remediation and Registration Texas Commission on Environmental Quality MC-122 P.O. Box 13087 Austin, TX 78711-3087 Mr. Ken Coates, Plant General Manager STP Nuclear Operating Company South Texas Project Electric Generating Station P.O. Box 289 Wadsworth, TX 77483 Mr. Anthony P. Jones, Chief Boiler Inspector Texas Department of Licensing and Regulation Boiler Division E.O. Thompson State Office Building P.O. Box 12157 Austin, TX 78711

SAFETY EVALUATION BY OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO GENERIC LETTER 2004-02 FACILITY OPERATING LICENSES NOS. NPF-76 AND NPF-80 SOUTH TEXAS PROJECT, UNITS 1 AND 2 DOCKET NOS. 50-498 AND 50-499 In a letter dated December 10, 2007 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML072520021), STP Nuclear Operating Company (STPNOC, the licensee), requested an extension of the due date of December 31, 2007, stated in Generic Letter (GL) 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized Water Reactors," for completion of corrective actions at South Texas Project (STP), Units 1 and 2. In a telephone conference on December 12, 2007, the U.S. Nuclear Regulatory Commission (NRC) staff asked the licensee to provide additional information on actions taken to date at STP, Units 1 and 2, to address GL 2004-02. STPNOC supplemented its submittal, in a letter dated December 13, 2007 (ADAMS Accession No. ML07XXXXXXX), to provide the requested additional information.

STPNOC stated that it has taken actions toward accomplishing the corrective actions described in GL 2004-02, including replacing the sump screens with substantially larger sump strainers at both units. However, the licensee stated that some testing activities needed to fully address GL 2004-02 will not occur until early 2008, and that additional time will be needed for the licensee to evaluate the test results. STPNOC stated its belief that the testing results will fully support all corrective actions taken in response to issues identified in GL 2004-02. The licensee further stated that, since hardware, procedures, and administrative changes are already implemented, STPNOC has reasonable assurance that plant systems and operators would respond consistent with the intent of the GL 2004-02 corrective actions, including compliance with the regulatory requirements listed in GL 2004-02.

The licensee stated that additional strainer head-loss testing for chemical effects is scheduled to be completed in February 2008, that the test report is expected to be available in May 2008, and that additional actions will then be needed by STPNOC to complete formal verification of design inputs, assumptions, and conclusions of STPNOC calculations and evaluations. In addition, STPNOC stated that revision of downstream effects analyses could possibly be needed. The licensee requested an extension to June 30, 2008, to allow full completion of Title 10 of the Code of Federal Regulations, Part 50, Appendix B, activities to support changing the plant design and licensing bases to be in compliance with actions taken in response to issues identified in GL 2004-02. The licensee stated that it will submit a letter by June 30, 2008, verifying completion of all corrective actions and confirming compliance with the regulatory requirements in GL 2004-02.

As of the date of issuance of this safety evaluation, document not yet placed into ADAMS.

The criteria for granting an extension to the due date of December 31, 2007, for completion of GL 2004-02 corrective actions are stated in SECY-06-0078. Specifically, an extension may be granted if:

• the licensee has a plant-specific technical/experimental plan with milestones and schedules to address outstanding technical issues with enough margin to account for uncertainties, and

• the licensee identifies mitigative measures to be put in place prior to December 31, 2007, and adequately describes how these mitigative measures will minimize the risk of degraded emergency core cooling system (ECCS) and containment spray system (CSS) functions during the extension period.

With regard to the first extension criterion, STPNOC has a plant-specific technical/experimental plan, with milestones and schedules, to complete the GL 2004-02 corrective actions by June 2008, as noted above.

With regard to the second extension criterion, the licensee stated that the following modifications, mitigative measures, compensatory measures, and/or favorable conditions are in effect at STP, Units 1 and 2, minimizing the risk of degraded ECCS and CSS functions during the extension period:

1. The three train-specific original design ECCS strainers for both STP units have been replaced with new design strainers. The new design increases the surface area of each strainer from 150.4 square feet to 1818.5 square feet. The diameter of the screen perforations has been reduced from 0.25 inches to 0.095 inches, thus significantly reducing the potential for downstream debris effects.

2. The surveillance procedure for inspection of the new design strainers has been implemented. The procedure requires a visual inspection of the entire exterior and the interior of the strainers, which includes a visual inspection of the sump and the vortex suppressor.

3. The procedure for design-change packages has been enhanced with additional controls related to managing potential debris sources such as insulation, post-loss-of-coolant accident (LOCA) recirculation flow paths, qualified coatings, addition of aluminum or zinc, and effect of post-LOCA debris on downstream components.

4. STPNOC has implemented actions described in its responses dated August 11, 2003, November 11, 2004, and July 13, 2005, to Bulletin 2003-01, Potential Impact of Debris Blockage on Emergency Sump Recirculation at Pressurized Water Reactors. The measures implemented include refilling the refueling water storage tank after verification of proper swap over to cold-leg recirculation, provision of guidance in emergency operating procedures for restoration of recirculation or for alternate cooling methods if flow blockage occurs, and operator training on indications of and response to strainer clogging.

The NRC believes that STPNOC has a reasonable plan for STP, Units 1 and 2, that should result in acceptable strainer function with adequate margin for uncertainties. Further, the NRC concludes that STPNOC has put mitigation measures in place at STP to adequately reduce risk for the requested extension period.

Based on the licensee satisfactorily addressing the applicable NRC criteria as discussed above, it is acceptable to extend the completion date for certain corrective actions for the issues discussed in GL 2004-02 (specifically, the tests and analyses described above) until June 30, 2008, for STP, Units 1 and 2. While the NRC accepts this date as reasonable allowance for contingencies regarding completion of remaining activities to address GL 2004-02, the NRC expects STPNOC to place a high priority on completing remaining actions and updating the plants licensing bases as soon as possible.

Principal Contributor: M. Scott Date: December 19, 2007