ML20203E244

Safety Evaluation Accepting Re Approval of Realistic,Median Centered Spectra Generated for Resolution of USI-A-46

ML20203E244
Person / Time
Site:	Millstone
Issue date:	02/09/1998
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20203E140	List: ML20203E135 ML20203E244
References
TASK-A-46, TASK-OR NUDOCS 9802260289
Download: ML20203E244 (4)

Text

_ _ _ _ ___________________-- - -- - -- - -- ~-

@ Hog hg g t UNITED STATES fyl g j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20066 0001 y*****j*

SAFE 1Y EVALUATION BY THE OFFIC.E OF NUCLEAR REACTOR REGULATION RELATED TO THE REALISTIC MEDIAN CENTERED SPECTRA GENERATED FOR THE RESOLUTION OF UNRESOLVED SAFETY ISSUE A-46 FACILITY OPERATING LICENSE NO. DPR-21 NORTHEAST NUCLEAR ENERGY COMD6t[(

MILLSTONE NUCLEAR POWER STATION. UNIT 1 DOCKET NO. 50-245

1.0 INTRODUCTION

As a part of Northeast Nuclear Energy Company's (NNECO's) effort in responding to NRC Generic Letter 87-02," Verification of Seismic Adequacy of Mechanical and Electrical Equipment in Operating Reactors, Unresolved Safety issue (USI) A-46," NNECO submitted a letter to the NRC dated September 26,1995, with engineering calcu at ons discussing the methodology and assumptions used for generating its realistic, mcGan centered in-structure response spectra for Millstone Unit No.1 Reactor, Auxiliary Rai ;ste/ Control and Turbine Buildings. The staff reviewed NNECO's submittal and issued a request for additional information (RAI) by NRC letter dated June 4,1996. NNECO formally provided a response to the staff RAI by letter dated October 17,1996.

The steff has completed its review of NNECO's latest response to the RAI and other pertinent documents. The staff's safety evaluation !s provided below.

2.0 EVALUATION NNECO used 30 earthquake time histories in performing seismic analyses to generate in-structure response spectra for the above noted Millstone Unit 1 structures. The 30 earthquake time histories included a suite of 14 real earthquake acceleration time histories snd 16 artificiel earthquake acceleration time histories. The 30 earthquake time histories were mcdified to achieve a suitable match with tha 5% damped licensing basis ground response spectrum anchored at 0.17g that was generated for the Millstone Unit 1 sustematic evaluation program.

Five percent damped response spectra for each of the 30 time histories were generated. The median of these response spectra were shown to match closely with the licensing basis ground response spectrum.

NNECO used three dimensional, fixed based structural models in performing dynamic analyses to generate in-structure response spectra for the buildings. Variation in the structural response due to variation in structural frequency and demping was accounted for by use of a Latin Hypercube simulation to select random variables to be used in each of the 30 earthquake time history analyses. The 30 earthquake time histories were assumed to be uniformly distributed, whereas, damping ratios and structur,a frequencies were assumed to be random variables that were log normally distributed with the median and log normal stcndard deviations.

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9002260289 980209 PDR ADOCK 05000245 P PDR Enclosure

4 2-Thirty dynamic anahses were performed for each structure, in these analyses, the horizontal components of time histories were paired randomly. Each horizontal time history pair was scated by a factor in order to match the licensing basis spectrum with the corresponding vertical time history being scaled by tu kthirds of the horizontal acceleration. Different time histories and different structural properties were used for each analysis. The median value of structural damping used is consistent with damping values provided in Regulatory Guide 1.61. Spectra were generated at each floor from each of the 30 individual analyses. The median of the 30 spectra for each floor and each of the two horizontal directions is computed and compared to the 1.5 times the bouncing spectrum given in the Generic Implementation Procedure, Revision 2 (GIP-2).

NNECO's selsmic analysis approa:h and the assumptions used in the analysis are consistent with Standard Review Plan Section 3.7.1 guidelines for multiple time history analysis. They are also judged ss consistent with applicable Millstone Unit i licensing basis and the GIP-2 guidelines provided for generation of realistic, median centered in structure response spectra for resolution of USI A-46 lasues.

3.0 CONCLUSION

On the basis of the preceoing evaluation, the staff concludes that NNECO's proposed seismic -

analysis approach and in structure response spectra for use in resolution of Millstone Unit 1 USI A-46 issues are acceptable. if NNECO changes the response spectra to be used in the resolution of USl A-46 issues during the program, it should notify the NRC of such an action.

Northe st Nucle:r Energy Company .

. Millstone Nuclear Power Station t

cc:

Unit i I

Lillian M. Cuoco,8 Esquire i

Mr. Wayne D. Lanning Senior Nuclear Counsel Deputy Director of Inspections Northeast Utilities Service Company Special Projects Office ~

P. O. Box 270

! Hartford, CT 061410270 475 /Jiendale Road King of Prussia, PA 19406-1415 2

. Mr. Kevin T. A. McCarthy, Director Mr. F. C. Rother Monitoring and Radiation Division Depa,tment of Er.vironmental Vice President - Work Services Protection Northeast Nuclear Energy Company P. O. Box 128 79 Elm Street Waterford, CT 06385 Hartford, CT 06106 5127 Mr. Allan Johanson, Assistant Emest C. Hadley, Esquire Director 1040 B Main Street P. O. Box 549 Office of Policy and Management West Wareham, MA 02576 Policy Development and Planning Division Mr. John Buckingham 450 Capitol Avenue - MSt SERN Department of Public Utility Control P. O. Box 341441 Hartford, CT 06134-144*i Electric Unit-10 Liberty Square New Bntain, CT 06051 Regional Administrator Region i Mr. David Amerine U.S. Nuclear Regulatory Commission Recovery Officer- Nuclear 475 Allendale Road King of Prussia, PA 19406 Engineering and Support Northeast Nuclear Energy Company P. O. Box 128 First Colectmen Waterford, CT 06385 Town of Woiarford Hall of Records-Senior Resident inspector 200 Boston Post Road Miptene Nuclea- Power Station Waterford, CT 06385 c/o ; .S. Nuclear Regul story Commission Mr. D. M. Goebel P.O. Box 513 Vice President - Nuclear Oversight Niantic, CT 06357

_ Northeast Nuclear Energy Company P. O. Box 123 Waterford, CT 06385 Mr. J. P. McElwain Recovery ONicer- M21 stone Unit 1 "

. Northeast Nuclear Energy Company P. O. Box 128 Waterford, CT 06385 4

a i

' Northeast Nuclear Energy Company Millstone Nuclear Power Station Unit 1 cc:

The Honorable Terry Concannon Co-Chair Nuclear Energy Advisory Council Room 4035 Legislative Office Building Capitol Avenue Hartford, Ct 06106 Mr. Even W. Weollacott Co-Chair Nuclear Energy Advisory Council 128 Terr /s Plain Road Simsbury, C1 06070 85

- Citizens Regulatory Commission ATTN: Ms. Susan Perry Luxton 180 Great Neck Road Waterford, Ct 06%5 Deborah Katz, President

- Citizens Awareness Network s P. O. Box 83 Shelbume Falls, MA 03170 Little Harbor Consultants, Inc.

Miilstone -ITPOP Project Office P. O. Box 0630 Niantic, Ct 06357-0630 Mr. Daniel L Curry Project Director Parsons Power Group Inc.

2675 Morgantown Road i

Reading, PA 19607 Mr. Don Schopfer Verification Team Manager ^

Sargent & Lundy 55 E. Monroe Street

! Chicago, IL 60603 b '