ML20012B297
| ML20012B297 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 03/02/1990 |
| From: | Boyle M Office of Nuclear Reactor Regulation |
| To: | Mroczka E CONNECTICUT YANKEE ATOMIC POWER CO., NORTHEAST NUCLEAR ENERGY CO. |
| References | |
| NUDOCS 9003140150 | |
| Download: ML20012B297 (3) | |
Text
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March 2, 1990 q
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Docket No. 50-245e F
. Mr. Edward J. Mroczka 1
. Senior Vice President-k
' Nuclear Engineering and Operations Connecticut. Yankee Atomic Power Company _
- Northeast Huclear_ Energy Company
- P.O. Box 270
- Hartford, Connecticut- 06141-0270-c f'
Dear Mr. Mroczka:
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SUBJECT:
- BWR LPCI SWING BUS TRANSFER DESIGNS L
In 1987, the NRC performed a survey of BWR plants to identify those plants.
whose LPCI swing bus transfer scheme is vulnerable to the single failure.of DC 3
control power similar to'an event at the Fermi 2 plant. During that survey,'
y M111 stone'1 was identified as one of six. plants that might have a similar-
, vulnerability. Subsequently, in telecons with your staff on November 29'and~
F iDecember 4, 1989,~it was stated that Millstone 1 uses two LPCI buses, instead of.a swing. bus, to meet the ECCS criteria of 10 CFR'50.46. This differs from our findings regarding LPCI loop selection logic which generally uses a swing C
-bus and-a bus transfer scheme. Therefore, in order to clarify this difference and to close out this issue, we request that you provide the information m'
requested in the enclosure to this letter.
If you have any questions regarding-the requested information, please contact me or Mr. Peter Kang of D
theElectricalSystemsBranch(301-492-0812)
The_ reporting-and/olr recordkeeping requirements of this letter affect fewer than 10 respondents; therefore, OMB clearance is not required under P.L'.-
96-511.
Sincerely,
/s/
R Michael L. Boyle, Senior Project Manager Project Directorate I-4 Division of Reactor Projects - I/II
^
Office of' Nuclear Reactor Regulation-
Enclosure:
DISTRIBUTION-f As: stated 4D,2 Docket m er MBoyle NRC & Local PDRs-OGC cc w/ enclosure:
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Mr. Edw'ard J. Mroc:kh Millstone Nuclear Power Station
. Northeast Nuclear Energy Company Unit No. I cc:
Gerald Garfield, Esquire R. M. Kacich,-Manager Day, Berry and Howard Generation' Facilities Licensing Counselors at Law Northeast Utilities Service Company City Place Post Office Box 270 Hartford, Connecticut 06103-3499 Hartford, Connecticut 06141-0270 W.-D. Romberg, Vice President D. O. Nordquist Nuclear Operations-Director of Quality Services
-Northeast-Utilities Service Company Northeast Utilities Service Company Post Office Box 270-Post Office Box 270 Hartford, Connecticut 06141-0270 Hartford, Connecticut 06141-0270 Kevin McCarthy, Director Regional Administrator Radiation Control Unit.
Region I Department.of Environmental Protection U. S. Nuclear Regulatory Commission State Office Building 475 Allendale Road Hartford, Connecticut 06106 King of Prussia, Pennsylvania 19406 Bradford S. Chase, Under Secretary First Selectmen Energy Division Town of Waterford-Office of Policy and Management Hall of Records 80 Washington Street 200 Boston Post Road Hartford, Connecticut 06106-Waterford, Connecticut 06385 S. E..Scace, Nuclear Station Director W. J. Raymond, Resident Inspector Millstone Nuclear Power Station Millstone Nuclear Power Station Northeast Nuclear Energy Company c/o U. S. Nuclear Regulatory Connission Post Office Box 128 Post Office Box 811 Waterford, Connecticut 06385 Niantic, Connecticut 06357 J. P. Stetz, Nuclear Unit Director Millstone-Unit No. 1 Northeast Nuclear Energy Company Post Office Box 128 Waterford, Connecticut 06385 o
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ENCLOSURE' l
REQUEST FOR ADDITIONAL INFORMATION ON LPCI SilING BUS TRANSFER SCHEME REGARDING A SINGLE FAILURE VULNERABILITY filLLSTONE UNIT 1 DOCKET NO. 50-245-We are currently reviewing design modifications proposed for the LPCI swing bus transfer " design flaw" that was recently discovered on Fermi-2 and several other-BWR/3 and BWR/4 plants. Since this design flaw could prevent the swing bus from
. seeking its alternative AC power source under a single failure of. DC control power in one division, there is a potential for a loss of all LPCI pumps. This would t
result in leaving only one core spray to perform their intended ECCS function i
under a design basis accident condition. For Fermi 2 this was found not to'be.
adequate for their ECCS function.
4 In order for the. staff to assure that fermi-2 concerns are not present at flillstone 1, ~ provide the following additional information:
1)~
Explain how your existing LPCI related buses are designed ' differently
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from other BWRs which employ LPCI swing bus design and still satisfy L:
the ECCS criteria when a single failure is assumed.
Include relevant i-electrical and piping diagrams, and any analysis and references to past L
NRC ECCS review of the swing bus design, g
2)
Demonstrate that there are no single failures in your electrical system (a.c. and d.c.) design which could degrade the ECCS to the point that only one core spray would be available to perform ECCS function during an accident by performing a failure mode and affect analysis on your LPCI system. The staff does not require that the bus itself be subjected to the single failure criterion since this failure was not required to be. considered during the original licen-sing of the plant.
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