ML20195B763

Forwards Safety Evaluation Re Primary Cold Leg Piping leak- before-break Revised Analysis

ML20195B763
Person / Time
Site:	Millstone
Issue date:	11/09/1998
From:	Mcdonald D NRC (Affiliation Not Assigned)
To:	Bowling M, Loftus P NORTHEAST NUCLEAR ENERGY CO.
Shared Package
ML20195B766	List: ML20195B763 ML20195B871
References
TAC-MA1070, NUDOCS 9811160268
Download: ML20195B763 (3)

Text

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o att fo 97C p . UNITED STATES g NUCLEAR REGULATORY COMMISSION g '

WASHINGTON, D.C. asse64001 l

L  %,*,,,, Havesnber 9,1998 4

i l Mr. Martin L. Bowling, Jr.

Recovery Officer - Technical Services l Northeast Nuclear Energy Company l c/o Ms. Patricia A. Loftus l Director- Regulatory Affairs P. O. Box 128 y .Waterford, Connecticut 06385

SUBJECT:

REVISED EVALUATION OF THE PRIMARY COLD LEG PIPING LEAK-BEFORE BREAK ANALYSIS FOR THE MILLSTONE NUCLEAR POWER STATION, UNIT NO. 2 (TAC NO. MA1070) l

Dear Mr. Bowling:

By letters dated June 25,1998, and September 9,1998, Nc 'heast Nuclear Energy Company

- (NNECO/ licensee) submitted a request for NRC review and approval of its reanalysis of the leak-before-break (LBB) status of the Millstone Nuclear Power Station, Unit No. 2 (MNPS-2), reactor coolant loop (RCL) piping. This reanalysis was necessary since upon replacement of the

, MNPS-2 steam generators in 1992, the loadings for sections of the piping (the RCL crossover t

and cold legs) were no longer bounded by the licensee's previous LBB evaluation. NNECO's .

submittal was made in accordance with the provision of General Design Criterion 4 of Title 10 of f the Code of Federal Reaulations. Part 50, Appendix A, which permits licensees to exclude the  !

dynamic effects associated with postulated pipe ruptures from the facility's licensing basis if the '

analyses reviewed and approved by the Commission demonstrate that the probability of fluid )

system piping rupture is extremely low under conditions consistent with the design basis for the piping. LBB evaluations utilizing the guidance of NRC NUREG-1061, Volume 3 and/or Draft Standard Review Plan Section 3.6.3 have been previously approved by the staff as a method for this demonstration. The licensee requested that the LBB behavior of the RCL be credited toward the MNPS-2 design basis of the neutron shield tank, core barrel snubbers, core barrel support ledge, and core barrel stabilizer blocks.

The staff has completed its evaluation of the licensee's submittals. The information provided by the licensee in its submittats were sufficient to permit the staff to independently evaluate the licensee's conclusions. The staff agrees with the licensee's conclusions that LBB behavior continues to be demonstrated for the MNPS-2 RCL hot leg based on analyses previously

- approved by the Commission and for the RCL crossover and cold legs based on the reanalysis.

Therefore, the staff finds that the licensee may continue to remove censideration of the dynamic effects associated with the postulated rupture of these portions of the RCL line from the licensing basis of MNPS-2 and that LBB behavior may be credited toward the design basis of the neutron shield tank, core barrel snubbers, core barrel support ledge, and core barrel stabilizer blocks.

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M. L Bowling, Jr. l The enclosed Safety Evaluation provides the details of the staff's review. This completes all staff l actions related to the referenced TAC number, if there are any questions, please contact me at l (301) 415-1408.

l l , Sincerely, 1

_- t l

l Danle! G. Mcdonald, Jr., Senior Project Manager Millstone Project Directorate Division of Reactor Projects - t/II l Office of Nuclear Reactor Regulation i

! Docket No. 50-336

Enclosure:

Safety Evaluation cc w/ encl: See next page 1

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! M. L. Bowling, Jr. November 9, 1998 The enclosed Safety Evaluation provides the details of the staffs review. This completes all staff actions related to the referenced TAC number. If there are any questions, please contact me at (301) 415-1408.

l Sincerely, Original signed by:

Daniel G. Mcdonald, Jr., Senior Project Manager Millstone Project Directorate Division of Reactor Projects - 1/11 Office of Nuclear Reactor Regulation l Docket No. 50-336 Enclosure Safety Evaluation cc w/ encl: See next page QlSTRIBUTION:

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