ML081830003

Approval of Extension Request for Corrective Actions Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized Water Reactors.

ML081830003
Person / Time
Site:	South Texas
Issue date:	07/02/2008
From:	Thadani M NRC/NRR/ADRO/DORL/LPLIV
To:	Sheppard J South Texas
Thadani, M C, NRR/DORL/LPL4, 415-1476
References
GL-04-002, TAC MC4719, TAC MC4720
Download: ML081830003 (8)

Text

July 2, 2008 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 June 19, 2008 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML081780060), STP Nuclear Operating Company (STPNOC, the licensee), requested an extension to the 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, corrective actions due dates for the South Texas Project (STP), Units 1 and 2, from June 30, 2008, to December 12, 2008. On June 24, 2008, the NRC staff participated in a telephone call with the STPNOC staff to seek clarification of the licensees June 19, 2008, request. STPNOC documented the telephone discussion in a letter attached to an email dated June 26, 2008 (ADAMS Accession No. ML081820164).

By letter dated December 19, 2007 (ADAMS Accession No. ML073520076), the NRC had previously approved an extension of the due date for completion of STP, Units 1 and 2 sump strainer blockage corrective actions from December 31, 2007, to June 30, 2008.

The NRC staff has evaluated the information provided in the STPNOC letter dated June 19, 2008, and clarifying letter attached to the email dated June 26, 2008. Based on that evaluation, the NRC staff has determined that for STP, Units 1 and 2, extension of the due date for completion of debris generation and transport calculation revisions and additional strainer head-loss testing until December 12, 2008, is acceptable.

J. J. Sheppard The NRC staffs evaluation of the extension request is enclosed. If you have any questions, please contact me at (301) 415-1476 or email mohan.thadani@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:

As stated cc w/encl: See next page

ML081830003 *memo dated OFFICE NRR/LPL4/PM NRR/LPL4/LA DSS/SSIB/BC NRR/LPL4/BC NRR/LPL4/PM NAME MThadani JBurkhardt MScott (*) THiltz MThadani DATE 7/1/08 7/1/08 6/27/08 7/2/08 7/2/08

South Texas Project, Units 1 and 2 7/2/2008 cc:

Senior Resident Inspector S. M. Head, Manager, Licensing U.S. Nuclear Regulatory Commission STP Nuclear Operating Company P.O. Box 289 P.O. Box 289, Mail Code N5014 Wadsworth, TX 77483 Wadsworth, TX 77483 C. M. Canady C. T. Bowman, General Manager, Oversight City of Austin STP Nuclear Operating Company Electric Utility Department P.O. Box 289 721 Barton Springs Road Wadsworth, TX 77483 Austin, TX 78704 Ms. Marilyn Kistler J. J. Nesrsta/R. K. Temple Senior Staff Specialist, Licensing E. Alercon/Kevin Pollo STP Nuclear Operating Company CPS Energy P.O. Box 289, Mail Code 5014 P.O. Box 1771 Wadsworth, TX 77483 San Antonio, TX 78296 Environmental and Natural Resources INPO Policy Director Records Center P.O. Box 12428 700 Galleria Parkway Austin, TX 78711-3189 Atlanta, GA 30339-3064 Mr. Jon C. Wood Regional Administrator, Region IV Cox, Smith, & Matthews U.S. Nuclear Regulatory Commission 112 E. Pecan, Suite 1800 612 E. Lamar Blvd., Suite 400 San Antonio, TX 78205 Arlington, TX 76011-4125 Director, Division of Compliance & Inspection Steve Winn/Christie Jacobs Bureau of Radiation Control Eddy Daniels/Marty Ryan Texas Department of State Health Services NRC Energy, Inc. 1100 W. 49th Street 211 Carnegie Center Austin, TX 78756 Princeton, NJ 08540 Mr. Ted Enos Mr. Nate McDonald 4200 S. Hulen, 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 Ms. Susan M. Jablonski Office of Permitting, Remediation E. D. Halpin, Site Vice President and Registration STP Nuclear Operating Company Texas Commission on Environmental Quality South Texas Project Electric MC-122 Generating Station P.O. Box 13087 P.O. Box 289 Austin, TX 78711-3087 Wadsworth, TX 77483

South Texas Project, Units 1 and 2 7/2/2008 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

EVALUATION OF EXTENSION REQUEST TO COMPLETE CORRECTIVE ACTIONS RELATED TO GENERIC LETTER 2004-02 BY THE OFFICE OF NUCLEAR REACTOR REGULATION FACILITY OPERATING LICENSES NOS. NPF-76 AND NPF-80 SOUTH TEXAS PROJECT, UNITS 1 AND 2 DOCKET NOS. 50-498 AND 50-499 By letter dated June 19, 2008 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML081780060), STP Nuclear Operating Company (STPNOC, the licensee), requested an extension to the 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, corrective actions completion due dates for the South Texas Project (STP), Units 1 and 2. The licensee requested an extension to the due date to complete corrective actions from June 30, 2008, to December 12, 2008, to allow additional time for revision of debris generation and transport calculations and additional strainer head-loss testing to confirm acceptable performance of the strainers with revised debris loading.

STPNOC requested an extension for completion of the activities and submittal of a final response to GL 2004-02. In a letter attached to an email dated June 26, 2008 (ADAMS Accession No. ML081820164), STPNOC summarized a June 24, 2008, telephone call between the NRC staff and STPNOC and provided clarification of the June 19, 2008, letter.

The NRC staff has reviewed the information provided by the licensee. The NRC staff had previously approved in a letter dated December 19, 2007 (ADAMS Accession No. ML073520076), an extension for the GL 2004-02 completion of STP, Units 1 and 2 sump strainer blockage corrective actions due date from December 31, 2007, to June 30, 2008. In its June 19, 2008, letter, STPNOC stated that the request for an additional extension to allow for revision of debris generation and transport calculations and performance of additional strainer testing with the revised debris loading is necessary due to the adverse results of strainer chemical effects head-loss testing completed in February 2008. In its June 19, 2008, letter and in the February 29, 2008, Supplement 3 to the Response to Generic Letter 2004-02 letter (ADAMS Accession No. ML080700338), the licensee stated that the facility hardware modifications and procedure changes and administrative controls required to support actions taken in response to issues identified in GL 2004-02 have already been implemented as had been previously discussed in the December 2007 extension approval letter.

In this evaluation, the NRC staff has based its reviews for granting extensions of the due date for completion of GL 2004-02 corrective actions on the criteria stated in SECY-06-0078 (ADAMS Accession No. ML053620174).

ENCLOSURE

Specifically, an extension may be granted if:

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

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

In addition, in SECY-06-0078, the NRC staff states that for the proposed extensions beyond several months, a licensees request will more likely be accepted if the proposed mitigation measures include temporary physical improvements to the ECCS sump or materials inside containment to better ensure a high level of ECCS sump performance.

With regard to the first extension criterion, STPNOC has provided a plant-specific technical/experimental plan, with milestones and schedules, to complete the GL 2004-02 corrective actions. The licensee-proposed plan includes:

• additional vendor strainer head-loss testing scheduled for July 2008;

• receipt of test report from the vendor in September 2008;

• STPNOC formal verification of design inputs, assumptions and conclusions of calculations and evaluations conducted in response to issues identified in GL 2004-02, including possible revision of the downstream effects analysis, and changing the plant design and licensing bases; and

• submission of the licensees final GL 2004-02 response by December 12, 2008.

With regard to the second extension criterion, the licensee stated in its letter dated December 10, 2007 (ADAMS Accession No. ML073520021), that hardware, procedures, and administrative controls required to support actions taken in response to issues identified in GL 2004-02 are already implemented at STP, Units 1 and 2, and that plant systems and operators would respond in a manner consistent with the intent of the GL 2004-02 during the extension period. The staff evaluation of the previous extension request concluded that STPNOC had mitigation measures in place at STP, Units 1 and 2 to adequately reduce risk for the previous requested extension period (through June 30, 2008).

In its June 19, 2008, letter, STPNOC stated a justification for an extension request for the final GL 2004-02 submittal to December 12, 2008, is essentially the same as the justification from the STPNOC extension request to the NRC dated December 10, 2007. The STPNOC June 19, 2008, extension request also included a summary of a quantitative risk assessment which conservatively assumed a loss of recirculation capability in all three trains due to strainer blockage and showed a delta core damage frequency of 2.4E-06/reactor year and a delta large early release frequency of 5.7E-09/reactor year. While the NRC staff has not evaluated this assessment in detail, for the half-year extension being requested, the incremental risk is small.

The NRC staff believes that STPNOC has a reasonable plan for STP, Units 1 and 2 that should result in the completion of final GL 2004-02 corrective actions that provide acceptable strainer function with adequate margin to address uncertainties. The additional time requested in the June 19, 2008, letter is relatively short and considered to be of low safety concern given the mitigation measures and plant improvements already in place.

Based on the licensee having satisfactorily addressed the NRC GL 2004-02 due date extension criteria as discussed above, the NRC staff finds that it is acceptable to extend the completion date for GL 2004-02 corrective actions associated with strainer chemical effects head-loss testing from June 30, 2008 to December 12, 2008.

The NRC staff expects STPNOC to place a high priority on completing the remaining actions and updating the plants licensing bases as soon as possible. In its June 19, 2008, letter, STPNOC committed that it will have completed changes to the STP, Units 1 and 2 licensing bases and will have submitted a letter to the NRC confirming completion of all GL 2004-02 corrective actions and confirming compliance with the regulatory requirements listed in GL 2004-02 by December 12, 2008.

In the June 24, 2008, telephone call, documented in the attachment to the email dated June 26, 2008, the licensee indicated that the July 2008 testing will be structured to demonstrate one or more debris load combinations, for which contingency actions could be taken to achieve satisfactory strainer performance. The contingency actions STPNOC is considering include additional analytical revisions and hardware modifications. The licensees preferred contingency actions are additional analytical revisions removing the excessive conservatisms in the debris generation and transport calculations. Another analytical option is to risk-inform the maximum break size for debris generation. Other potential contingency actions include modification of insulation to reduce fiber load in containment, installation of debris interceptors, installation of additional strainer modules, and elimination of the CSS automatic start. STPNOC indicated that a subsequent additional extension of the due date into 2009 may be requested if major contingency actions are required. However, STPNOC stated that the July 2008 testing scope will be structured to minimize the need for future testing iterations and will support a timely completion of GL 2004-02 corrective actions for STP, Units 1 and 2.

Principal Contributor: J. Bettle J. Golla Date: