ML072910733

Final Accident Sequence Precursor Analysis of February 23, 2006 Operational Event

ML072910733
Person / Time
Site:	Millstone
Issue date:	10/29/2007
From:	John Hughey NRC/NRR/ADRO/DORL/LPLI-2
To:	Christian D Virginia Electric & Power Co (VEPCO)
Sanders, Carleen, NRR/DORL 415-1603
Shared Package
ML072910721	List: ML071930281 ML072910733
References
IR-06-002
Download: ML072910733 (4)

Text

October 29, 2007 Mr. David A. Christian President and Chief Nuclear Officer Virginia Electric and Power Company Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711

SUBJECT:

MILLSTONE POWER STATION, UNIT NO. 2 - RE: FINAL ACCIDENT SEQUENCE PRECURSOR ANALYSIS OF FEBRUARY 23, 2006, OPERATIONAL EVENT

Dear Mr. Christian:

The enclosure provides the final results of the Accident Sequence Precursor (ASP) analyses of an event which occurred at Millstone Power Station, Unit No. 2 (MPS2) as documented in Licensee Event Report 336/06-002, dated April 21, 2006, and Inspection Report 05003366/2006002, dated May 5, 2006. These documents are publicly available through the Agencywide Document Access Management System, Accession Numbers ML061220573 and ML061250262, respectively. The subject matter event occurred at MPS2 on February 23, 2006, during which a manual reactor trip was initiated due to both steam generator feed pumps tripping following an instrument air leak. Following the trip, the plant experienced an abnormal cool down in part due to excessive auxiliary feed water flow. The ASP analysis calculated a point estimate conditional core damage probability (CCDP) of 8 x 10-6. The event is categorized as a low risk event (<1 x 10-4), in accordance with Regulatory Issue Summary 2006-24, Revised Review of Transmittal Process for Accident Sequence Precursor Analyses, therefore, this is an informal analysis review.

The U.S. Nuclear Regulatory Commission (NRC or Agency) established the ASP Program in 1979 in response to the Risk Assessment Review Group report (see NUREG/CR-0400, dated September 1978). The ASP Program systematically evaluates U.S. nuclear power plant operating experience to identify, document, and rank the operating events that were most likely to have led to inadequate core cooling and severe core damage (precursors), accounting for the likelihood of additional failures.

The ASP Program has the following objectives:

• Provide a measure for trending nuclear power plant core damage risk.

• Provide a partial check on dominant core damage scenarios predicted by probabilistic risk assessments.

• Provide feedback to regulatory activities.

• Evaluate the adequacy of NRC programs.

D. Christian The NRC also uses the ASP Program to monitor performance against the safety goal established in the agency's Strategic Plan. (See NUREG-1100, Vol. 21, dated February 2005.)

For more information about the ASP program, see the annual ASP program report at http://www.nrc.gov/reading-rm/doc-collections/commission/secys/2005/secy2005-0192/2005-0192scy.pdf.

The enclosure is provided for your information and no response is requested. If you have any questions please contact me at 301-415-3204 Sincerely,

/RA/

John D. Hughey, Project Manager Plant Licensing Branch I-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-336

Enclosure:

Final ASP Analysis cc w/encl:

See next page

D. Christian The NRC also uses the ASP Program to monitor performance against the safety goal established in the agency's Strategic Plan. (See NUREG-1100, Vol. 21, dated February 2005.)

For more information about the ASP program, see the annual ASP program report at http://www.nrc.gov/reading-rm/doc-collections/commission/secys/2005/secy2005-0192/2005-0192scy.pdf.

The enclosure is provided for your information and no response is requested. If you have any questions please contact me at 301-415-3204 Sincerely,

/RA/

John D. Hughey, Project Manager Plant Licensing Branch I-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-336

Enclosure:

Final ASP Analysis cc w/encl:

See next page DISTRBUTION:

Public RidsNrrDorlLpl1-2 RidsNrrLAABaxter RidsNrrPMJHughey RidsOgcMailCenter RidsAcrsAcnwMailCenter RidsRgn1MailCenter LPL1-2 R/F FEltawila ADAMS ACCESSION NOS: Package: ML072910721 Letter: ML072910733 Final ASP: ML071910721*By Memorandum dated OFFICE LPL1-2/GE LPL1-2/PM LPL1-2/LA RES/DRASP LPL1-2/BC NAME CSanders JHughey ABaxter FEltawila* HChernoff DATE 10/24/07 10/24/07 10/23/2007 08/08/2007 10/29/07 OFFICIAL RECORD COPY

Millstone Power Station, Unit No. 2 cc:

Lillian M. Cuoco, Esquire Mr. J. W. "Bill" Sheehan Senior Counsel Co-Chair NEAC Dominion Resources Services, Inc. 19 Laurel Crest Drive Building 475, 5th Floor Waterford, CT 06385 Rope Ferry Road Waterford, CT 06385 Mr. Evan W. Woollacott Co-Chair Edward L. Wilds, Jr., Ph.D. Nuclear Energy Advisory Council Director, Division of Radiation 128 Terry's Plain Road Department of Environmental Protection Simsbury, CT 06070 79 Elm Street Hartford, CT 06106-5127 Ms. Nancy Burton 147 Cross Highway Regional Administrator, Region I Redding Ridge, CT 00870 U.S. Nuclear Regulatory Commission 475 Allendale Road Mr. Chris L. Funderburk King of Prussia, PA 19406 Director, Nuclear Licensing and Operations Support First Selectmen Dominion Resources Services, Inc.

Town of Waterford Innsbrook Technical Center 15 Rope Ferry Road 5000 Dominion Boulevard Waterford, CT 06385 Glen Allen, VA 23060-6711 Charles Brinkman, Director Mr. David W. Dodson Washington Operations Nuclear Services Licensing Supervisor Westinghouse Electric Company Dominion Nuclear Connecticut, Inc.

12300 Twinbrook Pkwy, Suite 330 Building 475, 5th Floor Rockville, MD 20852 Rope Ferry Road Waterford, CT 06385 Senior Resident Inspector Millstone Power Station Mr. Joseph Roy, c/o U.S. Nuclear Regulatory Commission Director of Operations P.O. Box 513 Massachusetts Municipal Wholesale Niantic, CT 06357 Electric Company Moody Street Mr. J. Alan Price P.O. Box 426 Site Vice President Ludlow, MA 01056 Dominion Nuclear Connecticut, Inc.

Building 475, 5th Floor Rope Ferry Road Waterford, CT 06385