ML063340702

Unit No.1 - Approval of Extension Request for Completion of Corrective Action in Response to Generic Letter 2004-02

ML063340702
Person / Time
Site:	Calvert Cliffs
Issue date:	12/18/2006
From:	Milano P NRC/NRR/ADRO/DORL/LPLI-1
To:	Spina J Calvert Cliffs
Milano P, NRR/DORL/LPLA, 415-1457
References
GL-04-002, TAC MC4672
Download: ML063340702 (5)

Text

December 18, 2006 Mr. James A. Spina, Vice President Calvert Cliffs Nuclear Power Plant, Inc.

Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657-4702

SUBJECT:

CALVERT CLIFFS NUCLEAR POWER PLANT, UNIT NO. 1 - APPROVAL OF EXTENSION REQUEST FOR COMPLETION OF CORRECTIVE ACTIONS IN RESPONSE TO GENERIC LETTER 2004-02 (TAC NO. MC4672)

Dear Mr. Spina:

In a letter dated March 3, 2005, as supplemented on July 15, 2005, Calvert Cliffs Nuclear Power Plant, Inc. (the licensee) provided its 90-day response to 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, for Calvert Cliffs Nuclear Power Plant, Unit Nos. 1 and 2 (Calvert Cliffs 1 and 2). In the response, the licensee included a request for an extension of the completion date for the corrective actions at Calvert Cliffs 1 from December 31, 2007, to May 31, 2008. The licensees rationale for the extension was the complexities involved in installing a dual train self-cleaning strainer device designed by General Electric Company (an active strainer whose functionality is largely independent of debris load). In an August 30, 2005, letter, the licensee reiterated its request but changed the extension date to February 24, 2008. In Attachment 2 to the August 30 letter, as supplemented on November 29, 2005, and February 3, 2006, the licensee provided its justifications for the extension request at Calvert Cliffs 1. The NRC approved this extension request by letter dated April 12, 2006.

On June 30, 2006, the licensee updated its response to GL 2004-02, stating that it had decided to change from an active strainer design to a passive strainer design. In addition, the licensee stated that the installation of the passive strainer devices for both Calvert Cliffs 1 and 2 would be completed during the first refueling outage after April 1, 2006. The first refueling outage for Calvert Cliffs 1 after April 1, 2006, is in the spring 2008 outage. In Attachment 2 to a letter dated September 20, 2006, the licensee provided the following as justification for the extension request:

Licensee analysis supported by NUREG/CR-6808, Knowledge Base for the Effect of Debris on PWR [pressurized-water reactor] Emergency Core Cooling Sump Performance, and NEI-04-07, Pressurized Water Reactor Sump Performance Evaluation Methodology, concluding that only small fines of suspended fibrous insulation would be transported to the sump screen (so that a thin bed is not expected to form on the screen through accumulation of small fines on larger pieces of fiber, and therefore, much of the small fines and almost all of the chemical precipitates reaching the sump screen would pass through the screen);

J. Spina

• Conservative use of a 17 pipe diameter (17D) zone of influence (ZOI) for the licensees emergency core cooling system (ECCS) pump net-positive suction head (NPSH) calculations (derived from unjacketed insulation destruction testing), while there is actual test information showing that the Calvert Cliffs 1 jacketed NUKON fibrous insulation with Sure-Hold bands has a 1.6D ZOI. The licensee, therefore, inferred that fibrous debris loads would be significantly less than has been calculated for Calvert Cliffs Unit 1.

NRC approval of application of the leak-before-break principle at Calvert Cliffs 1 for dynamic effects from breaks in the reactor coolant system loop piping, accumulator piping, and reactor coolant loop bypass piping. The licensee stated that this increases the likelihood of noticeable leakage being detected and safe shutdown being conducted before an actual break in the subject piping; The existence of uncredited containment overpressure, leading to a calculated clear-screen NPSH margin of approximately 22 feet during a loss-of-coolant accident (LOCA) event; High standards of containment cleanliness at Calvert Cliffs 1; and Bulletin 2003-01 measures including operator training and actions (e.g., throttling or securing pumps to reduce head losses and to potentially have some debris fall off of the screen due to flow rates below the minimum screen retention velocity of NUREG/CR-6808).

In its April 12, 2006, letter, providing the original approval of an extension of the date for completing the GL 2004-02 corrective actions at Calvert Cliffs 1, the NRC noted that the existing Calvert Cliffs 1 sump screen is relatively large in size at 229 square feet, and that, although tri-sodium phosphate is used as a containment pH buffer, the calcium silicate insulation material with which the tri-sodium phosphate might react to form calcium phosphate precipitate is actually outside of the LOCA ZOI. Therefore, during a LOCA event, calcium phosphate chemical precipitate would not form, and calcium silicate insulation would not be dislodged and could not transport to and create blockage at the sump screen.

The NRC staff 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 staff has concluded that the licensee has put mitigation measures in place to reduce the risk during the requested short extension period. Therefore, the staff finds it acceptable to extend the completion date for the corrective actions for the issues discussed in GL 2004-02 until the completion of the Calvert Cliffs Unit 1 spring 2008 refueling outage, currently scheduled to begin on February 24, 2008. Should the licensee elect to begin the Calvert Cliffs 1 outage more than 30 days after February 24, 2008, it will need to provide the NRC with additional justification for further delay in completing GL 2004-02 corrective actions.

A PWR licensee with an approved extension into 2008 or beyond should submit an "as complete as possible" GL 2004-02 response by December 31, 2007. If any substantive

J. Spina 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 supplemental response should be submitted within 90 days of the change or outage completion.

If you have any questions, please contact me at 301-415-1457.

Sincerely,

/RA/

Patrick D. Milano, Senior Project Manager Plant Licensing Branch I-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-317 cc: See next page

ML063340702 OFFICE LPLI-1\\PM LPLI-1\\LA SSIB\\BC LPLI-1\\BC NAME PMilano SLittle MScott RLaufer DATE 12/07/06 12/12/06 11/07/06 12/18/06

Calvert Cliffs Nuclear Power Plant, Unit Nos. 1 and 2 cc:

President Calvert County Board of Commissioners 175 Main Street Prince Frederick, MD 20678 Mr. Carey Fleming, Esquire Sr. Counsel - Nuclear Generation Constellation Generation Group, LLC 750 East Pratt Street, 17th floor Baltimore, MD 21202 Mr. Jay S. Gaines Director, Licensing Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657-4702 Resident Inspector U.S. Nuclear Regulatory Commission P.O. Box 287 St. Leonard, MD 20685 Mr. R. I. McLean, Manager Nuclear Programs Power Plant Research Program Maryland Department of Natural Resources 580 Taylor Avenue (B wing, 3rd floor)

Tawes State Office Building Annapolis, MD 21401 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Ms. Kristen A. Burger, Esquire Maryland People's Counsel 6 St. Paul Centre Suite 2102 Baltimore, MD 21202-1631 Ms. Patricia T. Birnie, Esquire Co-Director Maryland Safe Energy Coalition P.O. Box 33111 Baltimore, MD 21218 Mr. Roy Hickok NRC Technical Training Center 5700 Brainerd Road Chattanooga, TN 37411-4017