ML20138G200

Discusses Aug 1995 Meeting W/Seimens Power Corp Re LBLOCA Evaluation Model & Identifing Problems Concerning Changes in Model Used by Siemen Power Corp.Requests Assessment of Impact of Model Error & Changes

ML20138G200
Person / Time
Site:	Millstone
Issue date:	10/11/1996
From:	Sheron B NRC (Affiliation Not Assigned)
To:	Feigenbaum T NORTHEAST UTILITIES SERVICE CO.
References
TAC-M96355, NUDOCS 9610180280
Download: ML20138G200 (4)

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g k UNITED STATES g j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20666-0001

. o k /g October 11, 1996 Mr. Ted C. Feigenbaum Executive Vice President and Chief Nuclear Officer Northeast Utilities Service Company

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c/o Mr. Terry L. Harpster

. Director - Nuclear Licensing Services P.O. Box 128 Waterford, CT 06385

SUBJECT:

10 CFR 50.46 LARGE BREAK LOSS-0F-COOLANT ACCIDENT EVALUATION MODEL FOR MILLSTONE NUCLEAR POWER STATION, UNIT 2 (TAC NO. M96355)

Dear Mr. Feigenbaum:

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During August 1995, the Nuclear Regulatory Commission (NRC) met with Siemens l Power Corporation (SPC) with regard to the large break loss-of-coolant l accident (LBLOCA) evaluation model. As a result of that meeting, we sent a letter to SPC, dated November 13, 1995, which identified problems concerning changes in the model used by SPC for pressurized water reactors. This model l was approved by the NRC staff to meet the requirements of 10 CFR 50.46 in the l

letter of July 8,1986, from D.M. Crutchfield (NRC) to G. Ward (Exxon).

In the staff's letter of November 13, 1995, we stated that SPC had made changes to the NRC-approved Fuel Cooling Test Facility (FCTF) reflood heat transfer coefficient correlation used ir the T00DEE" euter code and did not properly assess the significance of the code changs wraars that the following two major changes were made to FCTF cr A in the T00DEE2 code: (1) some nonphysical non-monotonit. .navior . .e FCTF heat transfer coefficient correlation with respect to the reflood rate were eliminated and

(2) the quench time calculation used i

the model, using data from Cylindrical Core Test Facility (CCTF) experiments, was modified. By letter dated March 13, 1996, the staff requested SPC to address the changes to the T00DEE2 model l

and the code errors identified since Juiy 1986. I On June 2,1996, SPC submitted topical report XN-NF-82-20, "EXEM/PWR Large Break LOCA ECCS T000EE2 Updates," Revision 1, Supplement 5, which described the updates made to the T00DEE2 computer code since 1986. The staff has completed its review of this report and has concluded that the proposed LBLOCA-ECCS model (i.e.,1991 model) is not acceptable and the previous approved model (i.e., the 1986 model) has an unacceptable error in the model.

The staff's letter to SPC dated October 11, 1996, 1 of conference calls with SPC on October 10 and 11,1996, whichincludesthesummaryh9 on this matter, will be telecopied separately.

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9610180280 961011 \

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i. Mr. Ted C. Feigenbaum- ,

Because of the staff's conclusions regarding the unaccepability of the reflood heat transfer coefficient correlation used in the T000EE2 computer code, we conducted a conference call on Thursday, October 10, 1996, with several licensees, including a representative of your plant. Other participants were i

4 representatives from Comanche Peak Station Units 1/2, Kewaunee Plant, Palisades Plant, Robinson Plant Unit 2, Shearon Harris Plant Unit 1, St. Lucie

Plant Unit 1, and SPC. The purpose of the conference call was to inform each

! licensee that the staff had found changes in the unapproved 1991 LBLOCA 1

evaluation model, which were intended to address problems with the approved 1986 model used by SPC for the LBLOCA and emergency core cooling system l analyses, unacceptable. In addition, the staff indicated that it will not '

accept LBLOCA analyses using the previously approved 1986 model unless that model adequately corrects the non-physical behavior observed in the reflood heat transfer correlation.

Therefore, in accordance with 10 CFR 50.46(a)(3)(ii), you should assess the impact of these model errors and changes and take whatever actions are required to assure compliance with 10 CFR 50.46. Further, as you were informed in the conference call, the staff has scheduled a public meeting on October 16, 1996, at 1:00 pm, in 0-12B11, at its Headquarters Offices. The affected plants and SPC were requested to attend this meeting to present the results of their assessment of the peak cladding temperature for the LBLOCA and the corrective actions and compensatory measures that have been undertaken, both short-term and long-term, to assure plant compliance with 10 CFR 50.46.

If you have any questions about this matter, please contact Daniel Mcdonald at 301-415-1408, or Jack Donohew at 301-415-1307.

Sincerely, f d  %

Brian W. Sheron, Acting Associate Director for Technical Review Office of Nuclear Reactor Regulation Docket No. 50-336 cc: See next page l

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T. Feigenbaum Millstone Nuclear Power Station Northeast Utilities Service Company Unit 2 cc:

Lillian M. Cuoco, Esq. Mr. D. B. Miller, Jr.

Senior Nuclear Counsel Senior Vice President Northeast Utilities Service Company Nuclear Safety and Oversight l P. O. Box 270 Northeast Utilities Service Company Hartford, CT 06141-0270 P. O. Box 270 l Waterford, CT 06141-0270 l Mr. John Buckingham Department of Public Utility Control P.M. Richardson,NuclearUnitDirectorl '

Electric Unit Millstone Unit No. 2 10 Liberty Square Northeast Nuclear Energy Company New Britain, CT 06051 P. O. Box 128 Waterford, CT 06385 Mr. Kevin T. A. McCarthy, Director Monitoring and Radiation Division Charles Brinkman, Manager l Department of Environmental Protection Washington Nuclear Operations l 79 Elm Street ABB Combustion Engineering l Hartford, CT 06106-5127 12300 Twinbrook Pkwy, Suite 330 Rockville, MD 20852 Mr. Allan Johanson, Assistant Director Office of Policy and Management Mr. E. A. DeBarba l Policy Development and Planning Division Vice President - Nuclear Technical 80 Washington Street Services Hartford, CT 06106 Northeast Utilities Service Company P. O. Box 128 Mr. S. E. Scace, Vice President Waterford, CT 06385 Nuclear Reengineering Implementation Northeast Utilities Service Company Mr. F. C. Rothen P.O. Box 128 Vice President - Nuclear Work Services Waterford, CT 05385 Northeast Utilities Service Company P. O. Box 128 Regional Administrator Waterford, CT 06385 Region I U.S. Nuclear Regulatory Commission Ernest C. Hadley, Esq.

475 Allendale Road 1040 B Main Street King of Prussia, PA 19406 P.O. Box 549 West Wareham, MA 02576 First Selectmen Town of Waterford Mr. B. D. Kenyon Hall of Records President - Nuclear Group 200 Boston Post Road Northeast Utilities Service Company Waterford, CT 06385 P. O. Box 128 Waterford, CT 06385 Mr. P. D. Swetland, Resident Inspector Millstone Nuclear Power Station c/o U.S. Nuclear Regulatory Commission P.O. Box 513 Niantic, CT 06357

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l I Mr. Ted C. Feigenbaum '

October 11, 1996 DISTRIBUTION:

PUBLIC

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