ML20091P129
| ML20091P129 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 01/24/1992 |
| From: | Chrzanowski D COMMONWEALTH EDISON CO. |
| To: | Murley T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| References | |
| REF-GTECI-048, REF-GTECI-049, REF-GTECI-NI, TASK-048, TASK-049, TASK-48, TASK-49, TASK-OR GL-91-11, NUDOCS 9201310240 | |
| Download: ML20091P129 (3) | |
Text
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Ccmmonwealth Edisen 5
1400 opus Place Downers Grove, minois 60515 i
January 24,1992 f
Dr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555 Attn: Document Control Desk
Subject:
Commonwealth Edison Response to Generic Letter 91 11 for Byron and Braldwood Stations Byron Units 1 and 2, h RC Docket Numbers 50 454 and 50 455 Braidwood Units 1 and 2, NRC Docket Numbers 50 456 and 50 457 i
Reference:
Generic Letter 91 11, " Resolution of Generic issues 48, LCO's for Class 1E Vital Instrument Buses, and 49, interiocks and LCOs for Class 1E Tie Breakers",
dated July 18,1991 I
Dear Dr. Murley:
Generic Letter 91 11 was issued as part of the resolution of Generic issues 128,
" Electrical Power Reliability". The Generic issues (GI-48 and GI 49 addressed by this letter involve vital AC buses and tie breakers. Specifically, the Generic Le)tter recommendsl nuclear plants ensure that procedures are in alace that include time limitations and survoillance requirements for; vital instrumen; buses (VIBs), inverters to VlBs and tie breakers that can con tect redundant Class 1E buses (AC or DC) at one unit or that can connect Class 1E buses between units at the same site.
L Commonwealth Edison (CECO) has reviewed Generic Letter 91-11 and has determined that Byron and Braidwood Stations are in compliance with the Letter's recommendations.
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Dr. Thomas E. Murley 2-January 24,1992 i
i The Technical Specifications for Byron and Braldwood were written using the Westinghouso Standard Technical Specifications (STS), NUREG 0452, Draft Revision 5, as a gulde. The NRC has recognized that the concerns of this Generic Lottor are addressed by those STS. Since Byron and Braldwood Stations have LCOs and Surveillanco requirements that closely follow the STS for VIBs and tio breakers, CECO bolloves Byron and Braldwood stations fully comply with the recommendations of Genoric Letter 91 11.
t The following evaluates the Generic Lettor issues against Byron's and Braldwood's Class IE AC and DC electrical distribution system.
Vital Insttument Buses (VIDs) and InYerters or Other Onsite Power Sources to the VIDs Byron and Braldwood Stations have four 120 volt AC VlBs per unit. Each of these busos is requirod, by Technical Specifications, to be onor0lzed from its associated Inverter connected to a DC bus. The Specifications do not allow continued power operation !! one of the vitalinstrument busos or invorters is inoperable. The allowed outage time for the instrument buses and invariers is two hours. If they are not restored, Technical Specifications require the reactor to be in HOT STANDBY within the next six hours.
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l In addition, Technical S aecifications indicate which inverters must energize o.oh of the vital buses. Technica Specification surveillance requirements assure that specified buses are determ8ned to be ener0 zad in the required mannor. This l
datormination is mado at least onco por sovon days.
Ile Breakers Connecting Common Unit.1E Buses (AC.otD.C)
The Class 1E safety related AC and DC electrical distribution systems at Byron and Braldwood do not have tio breakers that can connect common unit 1E busos.
Ile Dreakers Connecting Unit J E Buses (AC.otDC) Between Units Byron /Braidwood Technical Specifications section 3/4.9.2.1 establishes the LCOs and surveillance for cross tioing DC power sources between units. Typically, des the allowed outage time for the cross tle is two hours. However, if a shutdown unit (Mo 5 or 6) has an inoperable DC bus cross tied to the operating unit's bus the LCO is.
seven days. This LCO is permitted only if the loads on the affected bus are limited.
For AC power sources, Specifications 3/4.8.3.1, for Modes 1 through 4, and 3/4.8.3.2, for Modes 5 and 6. address 480 Class 1E buses. These buses do not have l
cross tie breakers between units. Specification 3.8.1.1 allows cross tleing tho 1E 4160 voit buses to the opposite unit's System Auxillary Transformer bank. No other cross ties between unit's 1E buses are possible.
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' Dr. Thomas E. Murley 3-January 24,1992 Based on the above information, CECO concludes that Byron and Braldwood Technical Specifications for AC and DC distribution systems provido controls that assure the recommendations of Generic Lotter 91-11 are met.
To the best of my knowled s and bollof, the statements contained in this 0
document are true and correct. In some res aoct these statements are not baced on my personal knowledge, but on information furn shed by other CECO employees, contractor employees, and consultants. Such Information has been reviewed in accordance with Company practice, and I believe it to be reliable, j
If thoro are any questions or comments, please contact me at (708) 515 7292.
Sincerely, O
A David J. Chrzano ' ski Nuclear Linensing Administrator 1
Generic lesues cc: A. Bert Davis, Regional Administrator Rill R. Pulsifer, Project Manager NRR/PDill 2 A. Hsia, Project Manager NRR/PDill 2 R. Elliott, Project Engineer NRR/PDill-2 S. Dopont, Senior Resident inspector Braidwood W. Kropp, Soolor Resident inspector Byron StMact N'
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