ML081760100

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

ML081760100
Person / Time
Site:	Comanche Peak
Issue date:	06/27/2008
From:	Balwant Singal NRC/NRR/ADRO/DORL/LPLIV
To:	Blevins M Luminant Generation Co
Singal, Balwant, 415-3016, NRR/DORL/LPL4
References
GL-04-002, TAC MC4676, TAC MC4677
Download: ML081760100 (6)

Text

June 27, 2008 Mr. M. R. Blevins Executive Vice President

& Chief Nuclear Officer Luminant Generation Company LLC ATTN: Regulatory Affairs P. O. Box 1002 Glen Rose, TX 76043

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION, UNITS 1 AND 2 - GENERIC LETTER 2004-02, "POTENTIAL IMPACT OF DEBRIS BLOCKAGE ON EMERGENCY RECIRCULATION DURING DESIGN BASIS ACCIDENTS AT PRESSURIZED WATER REACTORS," EXTENSION REQUEST (TAC NOS.

MC4676 AND MC4677)

Dear Mr. Blevins:

The U.S. Nuclear Regulatory Commission (NRC) has evaluated the information provided in Luminant Generation Company LLC letter, dated June 19, 2008, supporting a request for an extension of the due date for certain Comanche Peak Steam Electric Station (CPSES), Units 1 and 2 corrective actions for Generic Letter 2004-02, "Potential Impact Of Debris Blockage On Emergency Recirculation During Design Basis Accidents At Pressurized Water Reactors." The NRC has determined that for CPSES, Units 1 and 2, it is acceptable to extend the due date for completion of certain corrective actions, as described in the enclosure, until August 31, 2008.

If you have any questions regarding this matter, I may be reached at 301-415-3016.

Sincerely,

/RA/

Balwant K. Singal, Senior Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-445 and 50-446

Enclosure:

As stated cc w/encl: See next page

ML081760100

• Memo dated 6/23/2008 OFFICE NRR/LPL4/PM NRR/LPL4/LA NRR/SSIB/BC NRR/LPL4/BC NRR/LPL4/PM NAME BSingal JBurkhardt MScott (*) THiltz BSingal DATE 6/25/08 6/24/08 6/23/08 6/27/08 6/27/08 Comanche Peak Steam Electric Station 6/10/2008 cc:

Senior Resident Inspector Mr. Richard A. Ratliff, Chief U.S. Nuclear Regulatory Commission Bureau of Radiation Control P.O. Box 2159 Texas Department of Health Glen Rose, TX 76403-2159 1100 West 49th Street Austin, TX 78756-3189 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Mr. Brian Almon 612 E Lamar Blvd., Suite 400 Public Utility Commission Arlington, TX 76011-4125 William B. Travis Building P.O. Box 13326 Mr. Fred W. Madden, Director 1701 North Congress Avenue Regulatory Affairs Austin, TX 78701-3326 Luminant Generation Company LLC P.O. Box 1002 Ms. Susan M. Jablonski Glen Rose, TX 76043 Office of Permitting, Remediation and Registration Timothy P. Matthews, Esq. Texas Commission on Environmental Morgan Lewis Quality 1111 Pennsylvania Avenue, NW MC-122 Washington, DC 20004 P.O. Box 13087 Austin, TX 78711-3087 County Judge P.O. Box 851 Anthony P. Jones Glen Rose, TX 76043 Chief Boiler Inspector Texas Department of Licensing Environmental and Natural and Regulation Resources Policy Director Boiler Division Office of the Governor E.O. Thompson State Office Building P.O. Box 12428 P.O. Box 12157 Austin, TX 78711-3189 Austin, TX 78711

EXTENSION REQUEST TO COMPLETE CORRECTIVE ACTIONS GENERIC SAFETY ISSUE-191 ASSESSMENT OF DEBRIS ACCUMULATION ON PRESSURIZED-WATER REACTOR SUMP PUMP PERFORMANCE GENERIC LETTER 2004-02, "POTENTIAL IMPACT OF DEBRIS BLOCKAGE ON EMERGENCY RECIRCULATION DURING DESIGN BASIS ACCIDENTS AT PRESSURIZED WATER REACTORS COMANCHE PEAK STEAM ELECTRIC STATION, UNITS 1 AND 2 DOCKET NOS. 50-445 AND 50-446 By letter dated June 19, 2008 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML08xxxxxxx1), Luminant Generation Company LLC (the licensee) requested an extension to the U.S. 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 action due date for Comanche Peak Steam Electric Station (CPSES), Units 1 and 2. The stated intent of this extension was to allow for additional time to complete revisions to downstream effects analyses; documentation of plant-specific testing; and formal verification of design inputs, assumptions, and conclusions of calculations and evaluations. The licensee requested an extension to August 31, 2008, for completion of these activities.

By letter dated December 3, 2007, the licensee had previously submitted a request for extension of the CPSES, Units 1 and 2 sump clogging corrective actions due date of December 31, 2007, stated in the GL 2004-02. The licensee stated that the schedule for chemical testing for support of resolution of GL 2004-02 had been extended from December 2007 into the first quarter of 2008. The NRC staff reviewed the information provided and determined that it was acceptable to extend the due date for completion of corrective actions at CPSES, Units 1 and 2 for GL 2004-02 to June 30, 2008 (NRC letter dated December 27, 2007, ADAMS Accession No. ML073600874).

The licensee stated in its June 19, 2008, letter that it has successfully completed testing that showed adequate head-loss margin for all tested configurations, that the test protocol was established based on input from the NRC staff, and that testing confirmed the effectiveness of the new strainer design and its resistance to blockage from miscellaneous debris and labels.

The licensee also stated that the design-basis debris load did not result in a thin bed condition, and that the head loss increase due to chemical effects was minimal. Bypass testing was also performed. The licensee concluded, therefore, that corrective actions are substantially complete.

1 As of the date of issuance of this letter and enclosure, document not yet placed into ADAMS.

Enclosure

The licensee noted, however, that additional time is needed to perform the following:

• Complete revisions to the various downstream effects analyses, scheduled for July 2008.

• Complete numerous additional actions that are required prior to the vendor completing a final test report that meets the procurement specifications requirements, including those of Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Appendix B for control of purchased services and procurement document control. These actions are expected to be completed in July 2008.

• Complete formal verification of design inputs, assumptions, and conclusions of calculations and evaluations conducted in response to issues identified in GL 2004-02. These activities include finalizing the assessment of the impact of the test results on strainer net positive suction head (NPSH) calculations, strainer bypass sampling input to downstream effects analyses (in-vessel and ex-vessel),

as well as the potential impact on other GL 2004-02 corrective action evaluations.

These activities also include compliance with 10 CFR 50, Appendix B requirements for design control, document control, procedures and quality assurance records. These actions will be completed in August 2008.

The NRC has based its reviews for granting extensions to the due date for completion of GL 2004-02 corrective actions on the criteria stated in SECY-06-0078. 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 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 functions during the extension period.

SECY-06-0078 also states that for proposed extensions beyond several months, a licensees request will more likely be accepted if the proposed mitigative 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, the licensee has provided a plant-specific technical/experimental plan, with milestones and schedules, to complete the GL 2004-02 corrective actions, as discussed above.

With regard to the second extension criterion, the licensee stated in its letter dated June 19, 2008, that the following mitigative measures are in place:

• Plant hardware modifications, developed in response to issues identified in GL 2004-02, are installed at CPSES, Units 1 and 2 and are actively supporting compliance with the regulatory requirements for long-term cooling following a

design-basis loss-of-coolant accident. Hardware modifications include the following:

- ECCS sump screens were replaced with new strainers increasing the effective surface area from 200 square feet to almost 4000 square feet per emergency sump. The new strainers are contained within a 1-foot-tall solid debris interceptor, which will significantly reduce the quantity of debris which could reach the strainers. Modifications which divert water and debris from entering the recirculation pool near the strainers are complete. The design approach is to maximize the capability of the strainer while minimizing the debris load.

- The Refueling Water Storage Tank (RWST) low-low setpoint and the RWST switchover procedure were revised to support the new strainers.

The RWST to Containment Spray Isolation valves were replaced to reduce closing time for switchover from injection to recirculation. Control board instruments and controls and alarm were modified to support the setpoint change and enhance the operator interface for ECCS and spray switchover.

- Various modifications were made to reduce recirculation water holdup volumes and to assure that blockage would not occur in critical areas such as the refueling cavity. These modifications, in combination with the RWST changes above, increase the minimum post accident flood levels from 4 feet to over 5 feet resulting in a corresponding increase in NPSH margin.

• Implementation is complete for CPSES, Units 1 and 2 plant administrative procedures and processes to support the GL 2004-02 hardware modifications and revised operating practices.

• The interim compensatory measures implemented at CPSES, Units 1 and 2, in accordance with NRC Bulletin 2003-01, as described in the licensee letter to NRC dated August 8, 2003, providing response to NRC Bulletin 2003-01, remain in effect to minimize interim risks associated with post-accident debris blockage while GL 2004-02 evaluations are being completed. In accordance with NRC Bulletin 2003-01, these measures will remain in place at a minimum until all corrective actions for GL 2004-02 are complete.

In summary, the licensee has stated that it believes it has substantially completed corrective actions for GL 2004-02 and that it has demonstrated adequate NPSH through testing. Given this situation and the mitigation measures and plant improvements already in place, the additional time requested in the licensees June 19, 2008, letter to complete remaining evaluations and documentation is considered to be of low safety concern. Based on the licensee having satisfactorily addressed the NRC GL 2004-02 due date extension criteria as discussed above, the NRC staff finds it acceptable to extend the completion date for GL 2004-02 corrective actions associated with strainer performance testing, final analysis and related licensing activities, as described in this enclosure, for CPSES, Units 1 and 2 to August 31, 2008.