ML20092C611

Forwards Responses to Generic Ltr 91-11, Resolution of Generic Issues 48, 'Lcos for Class 1E Vital Instrument Buses' & 49, 'Interlocks & LCOs for Class 1E Tie Breakers.'

ML20092C611
Person / Time
Site:	Davis Besse
Issue date:	02/07/1992
From:	Shelton D CENTERIOR ENERGY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-GTECI-048, REF-GTECI-049, REF-GTECI-NI, TASK-A-48, TASK-A-49, TASK-OR 2010, GL-91-11, TAC-M82403, NUDOCS 9202120015
Download: ML20092C611 (9)

Text

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Y M C.S h 300 Madson Avenue ign,y gpgg  ;

Vice hesidert.Nxlear 08N (419)2 4 2300  !

i Docket Number 50-346 i

License Number NPF-3 Serial Number 2010 t

February 7, 1992 I 9

United States Nucicar Regulatory Commission ,

Document Control Desk Vashington, DC ?O555 P Subject Response to INelear Regulatory Commission (NRC) Generic Letter 91-11, Resolution of Generic Issues 48, "LCOs for Class 1E Vital Instrutnent Duses," and 49, " Interlocks and LCOs for Class 1E Tie Breakers" Pursuant to 10CFR50.54(f)

Gentlemen:

Nuclear Regulatory Commission (NRC) Generic Letter 91-11 (Toledo Edison i letter Log Number 2523) dated July 18, 1991 advised licensees of the NRC staff positions resulting from the resolution of Generic Issues 48, "LCOs for Class 1E Vital Instrument huses," and 49, " Interlocks and

.LCOs for Class IE Tie Breakers". Attached is Toledo Edison's response for the Davis-Desse Nucicar Power Station (DDNPS) to Generic Letter ,

91-11.

Should you have any questions concerning this inatter, please contact Mr.-R. V. Schrauder, Manager - Nuclear Licensing at (419) 249-2366.

Very truly yours, ifWl ,

HKL/dlm attachments cci A. B. Davis, Regional Administrator, NRC Region III ,

J. D. llopkins, NRC/NRR DB-1 Senior Project Manager

• V. Levis, NRC Region 111, DB-1 Senior Resident inspector Utility Radiological Safety Boatd 9202120015 920207- ,A PDR P

ADDCK 05000346 PDR '

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Dockot Numb 2r $0-346 Licenso Numb 3r NPP-3

, Serial Number 2010

. . Attachment 1

. Page 1 l

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RESPONSE TO CENERIC LETTER 91-11 I

FOR DAVIS-BESSE NUCLEAR POVER STATION UNIT NUMBER 1 t

This letter is submitted pursuant to 10CFR50.54(f). Enclosed is Toledo  !

Edison's responso (letter Serial Humber 2010) to Generic Letter 91-11, Resolution of Generic Issues 48, "LCOs for Class IE Vital Instrument Buses," and 49, " Interlocks and LCOs for Class 1E Tie Breakers". t i.

/

By: .

\ W 3' '~3 D. C. Shelton, Vice President - Nuclear i

Svorn and subscribed before me this 7th day of February,-1992, Y1df]a) Yb ~ ~ ~ ~ ~ ~ ~

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1 Docket Number 50-346 License Number NPT 3 Serial Number 2010

_, Attachment 2

. Page 1 TOLED0_ EDISON RESPONSE TO GENERIC LETTER 91-11, Backgr_ounds l

The staff of the United States Nuclear Regulatory Commission (NRC) has completed the evaluation of Generic lasues (GIs) 40 and 49 as part of the tesolution of GI-120, " Electrical Power Reliability." Gl-48 and GI-49 address vital ac buses and tje breakers that connect redundant safety-related buses.

As a result of its evaluation, the staff concluded that unless licensees provide adequate justification that such provisions are not -

l needed at-their specific facilities, all licensees should have appropriate procedures to fulfill the following requirements:

1. Limit the time that a plant is in possible violation of the single-failute criterion with regard to the Class lE vital instrument buses and tie breakers, .,

2. Require surveillances of these components, and I

3. Ensure that, except for the times covered in Item (1), the i plant is operating in an electrical configuration consistent _

vith the regulations and its design bases.

As stated in the Generic Letter, " vital instrument buses" refers to the l ac buses that provide power for the instrumentation and controls of the engineered safety features (ESP) systems and reactor protection system i (RPS) and are designed to provide continuous power during postulated f events including the loss of normal offsite power, and " tie breakers" i are devices that. cross-connect either redundant Class lE buses in one

- unit or Class lE buses in different units at the same site.

Davis Besse Nuclear Power Station Design:

Based on the above definition, vital instrument bus (V1B) refers to the .

essential 120V ac instrumentation subsystem. As shovn on the attached i

- figures, there are four essential instrument distribution panels ,

(Yl/YlA,'Y2/Y2A, Y3, and Y4). Each of these panels normally receives  ;

power through a regulated rectifier.(YRF1, YRF2, YRF3 and YRF4) and an ,

inverter (YVI, YV2, YV3, and YV4) from essential 480V ac motor control centers (HCCs) E12A and F12A. Reserve power to the essential inverters

- is supplied f rorn the 125V.dc essential distribution panels (DIP, D2P, <

DIN,-and D2N) via coupling dindes. Each of these four redundant essential-125V de distribution panels is _ nor'nally povered -Irom one of the two redundant 250a25V de MCCs, (DC McC1 or DC HCC2), with a manually sn tched reserve (via an alternate feed breaker interlock device) from the second de MCC. The de McCs are backed by station batteries. The output of the regulated rectifiers-is maintained 3 i volts higher than-the station battery voltage. Failure of the .

rectifier input ac source or. failure of the rectifier itself vill cause the battery or charger to become the de source to the corresponding ,

essential inverter with no power interruption.

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Docket Numbet' 50-346 License Number NPP-3

, Serial Number 2010

. Attachment 2

. Page 2 Inverters YVI and YV4 are also equipped with a Static Transfer Switch ]

and a Hanual Bypass Switch. Through olther of these svitche% an ensential alternate source of power is available to panel Yl/Y1A or Y4 via a 480/120V at voltage regulated transfotmer (XY1 or af4, respectively). A non-essential alternate source of pover is also

, availabic to panel Yl/Y1A or Y4 from a 120V ac regulated instrument

, distribution panel (YAR or YBR, respec$4vely). A manual transfer is .

tequired. The fuse for this citeult i s normally removed when normal l Class lE pover through inverter YV1 or YV4 is available.

An essential alternate source of pover is available to panel Y2/Y2A or '

Y3 via a 480/120V ac voltage regulated transfo* met (XY2 or XY3, respectively). A manual transfer is required. 5 Each of the four essential 120V ac insttument disttibution panelt supplies power to one of the four channels in the reactor protection a system (RPS) and one of the four channels in the safety features actuation system (SPAS). The essential 120V ac. instrument subsystem is arranged so that any type of single fallute or fault vill not prevent the RPS or SPAS from. performing $ts salety functions. There are four independent panels available, and, while on the inverters, a single failure within the system can involve only one panel. A combination of simultaneous failures or faults on any two of the channels vill trigger ,

RPS and SPAS.

The Davis-Beste Nuclear Power Station essential 120V ec instrumentation ,

system does not include tie-breaker devices which vould allov redundant

essential instrument distribution panels to be cross-connected.

, Likewise, the Davis-Besse Nuclear Power Station essential 125V de i distribution system, which supplies reserve power to the 120V ac ,

instrumentation system, does not include tie-breaker devices which would allow redundant essential 12bV de distribution-panels to be cross-connected. .

Summary of Conformance of the Generic Letter Requirements:

• The Davis-Besse Nuclear Pover Station Operating License, Appendix A, Technical Specifications were developed from the Standard Technical Specifications for. Babcock and Vilcox Pressurized Vater Reactors -

NUREG-0103. Davis-Besse Nuclear Power Station has procedures which

implement the required veekly Technical. Specification sutveillances '

(TS 4.8.2.1, 4.6.2.2, 4.8.2.3.1, and 4.8.2.4.1) on the vital (essential) ae and dc instrument buses and power supplies, which verify correct breaker alignment and indicated pover-availability. .The essential power source panel indications and voltage outputs are i checked to verify that power is not being provided frat the essential -

L alternate source. -Transfer switches and alternate feed breaker interlock devices are checked to verify train separation. An .

appropriate note has.been added to the Instrument AC System Procedure  ;

to limit the maximum time alloved for povering a single channel (Panels ,

L Yl/YlA, Y2/Y2A, Y3, or Y4) f rom a non-essential er essential al ternate

) source of power to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> during'Hodes 1 through 4, provided the r

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Docket tiumber $0-346 License Humber NPF-3

, Serial Number 2010

, Attachment 2

- Page 3 i i

temaining three chdnnel$ are_ operable and poVered from their associated essential inverter. A note has also been added to clarify that in Mode 5 or 6, elther panel Yl/Y1A or Y2/(2A must be powered irom an essenttal source, however the remaining three channels may be povered f ro.n any source.

liased on the above, it is concluded that the Davis-liesse Nuclear Power Station design and procedures adequately address the Generic Letter 91-11 NRC stafi positions.

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Docket Number 50-346 License Number NPT-3 Settal Numbet- 2010 Attachment 2 Page 4 Figure 1 ESSENTIAL PANtt,$ Y1 AfiD Y1 A POWER SOURCES ORAVING DC DC MOC1 HCC2 0101 (NC) '"

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Docket Number 50-346 LicCnso Number NPF-3

- Serial Number 2010 Attachment 2 Page 6 Figure _]

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, Docket Number 50-346 License Number NPF-3 Sorial Number 2010

• • -Attachmeist 2 Page '/

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