ML20091N193

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

ML20091N193
Person / Time
Site:	Point Beach
Issue date:	01/23/1992
From:	Zach J WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CON-NRC-92-010, CON-NRC-92-10, REF-GTECI-048, REF-GTECI-049, REF-GTECI-NI, TASK-A-48, TASK-A-49, TASK-OR GL-91-11, VPNPD-92-046, VPNPD-92-46, NUDOCS 9201300117
Download: ML20091N193 (4)

Text

_

c Wisconsin Electnc POWER COMPANY 23t w Mchcan.ro b 2h wmee w 63701 Mtarm 2345 VPHPD 04 6 NRC-92-010 January 23, 1992 U.S. NUCLEAR REGULATORY COMMISSION Document Control Desk Mail Station P1-137 Washington, DC 20555 Gentlemen:

DOCKET 50-266 AND 50-301 RESPONSE TO GENERIC LETTER 91-11

-RESOLUTION OF GENERIC ISSUES 48.

"LCOs FOR CLASS 1E VITAL INSTRUMENT BUSES,"

AND 49, "INTERLOOKS AND LCOs FOR CLASS 1E TIE BREAKERS" PU N:UANT TO 10 CFM 50.54(El POINT BEACH NUCLEAR PLANT, UNITk_1,AND 2

-This letter is;in" response to NRC_ Generic Letter No. 91-11,

" Resolution of Generic Issues 48, -'LCus-For Class 1E Vital Instrument 1 Buses,' and 49, ' Interlocks and LCOs For Class IE Tie Breakers' Pursuant to 10 CFR 50.54 (f) ," dated July 18, 1991. In the Generic Letter you directed all licensces to provide the NRC with' certification, within 180 days of receipt of the subject Generic Letter, that they-have_either implemented the appropriate procedures cnr prepared justification that: such procedures are not needed to fulfill-the following requirements:

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

-2. Require surveillances of these components.-

3. Ensure'that, except for-the times covered in Item (1), the plant is operating in an electrical configuration consistent with the regulations and its design bases.

After careful evaluation and consideratien of the above requirements,,we have concluded that the present and planned controls at Point Beach Nuclear Plant (PDNP) are adequate to satisfylthe intent of-this Generic Letter. Justification for our conclusion follows.

~

-9201300117 920123 L fi

-. PDR- ADOCK 05000266 / I U' P- PDR A sum!inyofiliswmm Emy.Topratim

l .

NRC. Document Control Desk January 2: 1992 Page 2 LCOs and Suryelllances For Class 1E Vital Instrument Buses Each PBNP unit utilizes four separate and independent reactor protection instru nent channels termed Channels I, II, III and IV; color-coded red, white, blue and yellew. Each instrument channel is supplied by a separate Class 1E 120 volt AC instrument bus.

Each Class 1E instrument bus is made up of two sub-buses (for example, buses 1YO4 and 1Y104). For each instrument channel, one laverter is dedicated to the Unit 1 instrument bus and a second is dedicated to the Unit 2 instrument bus. A third inverter is available as a spare which can swing between either unit's instrument buses of the same " color." This spare inverter allows either dedicated inverter to be taken out of service for preventive maintenance, corrective maintenance, or normal surveillance requirements, while maintaining power to reactor protection instrumentation. While it is physically possible to supply similar buses of two units by the same swing inverter, administrative controls are in place to prevent the swing inverter from supplying power to both units' instrument buses at the same time.

There arc no cross-ties between the instrument buses of the same unit. However, it is physically possible to cross-connect DC power supplies of two inverters supplying two instrument buses of the same unit. Simultaneously snutting breakers 72-302 and 72-402 would cross-connect 125 volt DC buces D03 and D04. However, interlocks prevent this lineup from occurring. Likewise, shutting breakers 72-104 and ~12-204 concurrently would cross-connect 125 volt DC buses D01 and D02. Plant modificatica 90 -134 will provide an interlock to prevent simultaneous closure of those breakers. Operating instructions presently restrict the above lineups. Since the breakers require manual operation, no single credible event could cause two of the breakers to simultaneously close.

Because physical and administrative controls prevent one power source from concurrently supplying more than one vital instrument bus, we are not in jeopardy of violating the single-failure criterion for Class 1E vital instrument Luces. Therefore, we have concluded that an LCO or surveillance is not needed to satisfy the above requiremants.

LCOs and Surveillances for Class lE Tie-Breakers The Class 1E tie-breakers at PBNP consist of breakers 1852-16C and 2B52-40C (Unit 1 and Unit 2 common tie-breakers for 480 volt safeguards buses B03/B04) and 1A52-61 and 2A52-71 (Unit 1 and Unit 2 common tie-breukers for 4160 volt safeguards buses l

i l.

NRC. Document Control Desk January 23, 1992 Page 3 A05/A06). In addition, simulte.neously shutting contactors 1B491 and 2B391 would connect safeguards buses 1B04 and 2B03 and shutting contactors 1B3212H and 2B4212B would connect buses 1803 and 2B04. However, interlocks and plant operating instructions

-prevent the_simultaneour closure of these contactors.

Presently, the normal configuration for the A05/A06 bus tie-breakers consists of (1) tie-breakers racked out, (2) tie-breakers physically removed from their cubicles, (3) DC control power fuses in "OFF," and (4) control switches in pull-out. The B03/B04 bus tie-breakers are normally racked in with DC control power fuses "OFF" and control switches in pull-out. Because the B03/004 bus tie-breakers are maintained racked in, plant moditication 90-175 has been approved to install an annunciator that will indicate in the control room if the B03/B04 tie-breaker is either advertently or inadvertently closed. This annunciator is being installed in response to Electrical Distribution System Functional Inspection (EDSFI) Deficiency. 90-201-08, " Single Failure of Safeguards 480 volt AC Bus Tie-Breaker." This deficiency identified the new configuration with control power secured and the inability to remotely monitor tie-breaker position. Annual maintenance is also conducted on all of the above tie-breakers to verify proper operation.

Point-Beach Nuclear Plant Licensee Event Report 301/80-005-00 reported an improper electrical lineup of buses 2A05 and 2A06.

Durf.ng.a training walkdown of the safeguards-electrical supply cabinets, it was discovered that the 2A05/2A06 tie-breaker was shuc. The improper lineup probably occurred after a loss of AC power test on May 2, 1980, but was not discovered until June 9, 1980. To prevent recurrencc of this e'ent, the breaker was uniquely identified on the electrical layout board, and procedure changea1were (2plemented t, include an electrical lineup check after performance of the loss of AC power test and prior to return to power.

The allowable duration for use of the common tie-breakers is

-administratively controlled in plant operating instructions to be

- less than eight hours. PBNP Technical Specification Change Request 132, "LCO's For Power Distribution on Safeguards Buses,"

was suomitted to the NRC on September 22, 1989, to allow the use of the tie-breakers for up to eight hours. A modification to this request is being reviewed in-house to provide a more l

L acceptable duration'for use of the tie-breakers and to allow

their use only when the associated reactor is shutdown.

l Since the A05/A06 tie-breakers are physically removed from their cubicles and the B03/B04 tie-breakers are disabled while l

_. . ~_ - .. - . ___- -. . -_._- . .. .--. - - .. , ,

i~ f * '

NRC. Document Control Desk January 23, 1992 Page 4 providing remote position indication at all times, we have concluded that a surveillance in addition to the yearly maintenance inspections is not needed to satisfy the above requirements.

Please contact us if you have any questions regarding the above information.

Sincerely, sk Jam a J. Zac

.L Vice! President Nuclear Power Copies to NRC Regional. Administrator, Region III

~

NRC Resident Inspector Subscribed and agorn to before me this 211d day of \ un ,1992.

Mveuo Ci- .h Ow4 heto-zpa -

Notary-Public, State of Wisconsin My commission expires 5-2 2 - y y ,

9

~,