ML20012D830

Responds to Generic Ltr 89-19, Safety Implication of Control Sys in LWR Nuclear Power Plants. No Limiting Condition for Operation Required for Overfill Protection Sys at Plant

ML20012D830
Person / Time
Site:	Point Beach
Issue date:	03/20/1990
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CON-NRC-90-027, CON-NRC-90-27, REF-GTECI-A-47, REF-GTECI-SY, RTR-NUREG-1218, TASK-A-47, TASK-OR GL-89-19, VPNPD-90-135, NUDOCS 9003280435
Download: ML20012D830 (3)

Text

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- POWER COMPANY.

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~ NRC-90-027:

C March-20, 1990-

-U.- S. NUCLEAR REGULATORY COMMISSION-Document l Control' Desk-

'MailiStation P1-137.

Washington, D..C.;20555

. Gentlemen:

DOCKETS 50-266 AND-50-301

RESPONSE TO GENERIC LETTER 89-19

. tSAFETY IMPLICATION OF CONTROL-SYSTEMS 4 lIN LWR NUCLEAR' POWER PLANTS POINT BEACH-NUCLEAR PLANT. UNITS 1 AND 2 "NRC Generic. Letter 89-19,. dated September'20, 1989,, discussed the

' resolution:of USI A-47, " Safety Implications of Control Systems

i'n1 LWR Nuclear. Power

Plants."L The NRCLconcluded that protection

- fshould be provided for'certain control: system failures.

. . :Specifically, , the NRC concluded 'that all PWR- plants should; be.-

)provided with: automatic steam generator'overfilliprotection'.- 'Thol Generic-Letter, requested a, statement 1within-180 days whether-the

+ .recommendationsiprovidedTin: Enclosure 2cof:the1 letter would'be n ,

implemented.and, if so,. schedule for implementation. If~the recommendations were not=to be' implemented, appropriate

. justification 1was~to.be-provided.

Enclosure 2 to the Generic Letter 1identiflesethree groups-of Westinghouse-designed:plantsito be considered. Point Beach Nuclear? Plant appears to fall'into Group I, with the following exception. -Point; Beach uses a two-out-of-three hi-hi steam generator water level initiating logicxwhich is safety grade and unes one out of the three channels for=both level control'and Joverfill protection. The system isolates main feedwater (MFW)-by

closing the-MFW control valves. .This arrangement is the same as-that; described'for the MFW isolation of the Group I Westinghouse plants, except that-the MFW pump-is not tripped. Instead, a recirculation line for pump protection allows limited flow back to the1 main condensers.

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NRC Document Control Desk MarchJ20,-1990 Pagen2J

-The-steamigenerator level instrument loop components used'for  !

steam generator overfill protection are safety-grade and i addressed in the- Technical' Specifications as they are also used .{

for low-low steam. generator level reactor _ trip actuation. The  !

MFW control valves are closed on a 2/3 hi-hi. steam generator water level signal by venting the valve air actuators through two parallel solenoid-valves._ one of these solenoid valves also isolates air to the actuators. Both of these solenoid valves'are currently required to vent sufficient. air fast enough to meet the closure times for safety injection isolation, but either one is able to vent the actuator pressure within sufficient time to protect from an-overfill incident. Both of these solenoid valves are environmentally qualified.

p L The overfill protection system at Point Beach Nuclear Plant uses L, three water level channels per steam generator, each channel E being powered from a different instrument bus. Each of the  !

instrument buses is connected to its own battery and DC bus l through an inverter. Each of the. channels is located in a 1 L different instrument cabinet. One of the three channels also l L supplies the MFW control system. l L

L The 2/3 logic uses energized relays in series which are fed from H different instrument buses. The loss of power will de-energize the relay and close-the MFW control valves.

[ The' overfill protection system solenoid valves have Battery'D05 L as i their power supply. They are fed through a series of.DC i L

distribution panels. If the power supply is lost, the solenoid p valves will operate to prevent overfilling the steam generators.

DC power is required to keep the solenoid valves.in their proper ,

position for-normal operation. Air is required to keep the MFW  !

control valve open. Loss of DC power will de-energize the solenoid valves, isolating air to the MFW control valve operator and releasing the air in the operator, closing the valve. The MFW control system for the "A" steam generator is powered from the 120 volt AC, YO1, " red" instrument bus, which is powered from ,

the red channel inverter. The red channel inverter uses the DOS  !

battery or DOS battery charger as its source of power. The MFW  !

control system for the "B" steam generator is powered from.the 120 volt AC, YO4,." yellow" instrument bus, which is powered from the-yellow channel inverter. The yellow channel inverter uses i the D106 battery or the'D106 battery charger as its source of-power. Failure of the inverters or failure of the associated DC buses will cause the MFW control valves to close, preventing overfill of the steam generators.

There are some fire locations which could disable both the 1 automatic overfill protection system and the normal MFW control

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, NRC Document: Control Desk' >

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system.- The loss'of steam generator level indication for-fires j in:these areas was identified in the Point Beach Appendix R i review. :As a' result, alternate-wide-range steam generator' level-

-indicationxis available.outside the-control room. independent of'

~the fire zones of1 concern for the "B" steam generator on each

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. unit,.although-no indication-of "A" steam generator level is1 provided. Operator action would be required to ensure feedwater +

. isolation in the event of a' fire-related loss of steam generator -

' level instrumentation. 7 The~bistables for the overfill protection system are. functionally I

' tested monthly;. steam generator level transmitters are calibrated t each refueling'and feedwater isolation valves-are tested each '

refueling. However, there istno Technical' Specification

-requirement.for calibrating'or functionally. testing the overfill-protection system. A Technical Specification change Request to add theLoverfill protection system logic.asLpart of this item will be submitted 1by July-1990.' There are no LCO's associated  !

Lwith the overfill protection system. Because of.the low probability-of;an overfill event leading to core damage / main steam line break,.as identified in NUREG-1218, and the fact that no overfill events have occurred at Point Beach in.nearly forty

' years of reactor operation, no:LCo's should be required for the overfill protection system at Point Beach Nuclear' Plant.

If you have any questions, please do not hesitate to contact us.

Very truly yours, ,

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'{ 6 (A ' 4G / +

-C. W. fay LVice President

' Nuclear Power J Copies.to NRC Regional Administrator, Region III

NRC Resident Inspector Subscri ed and sworn to-before me l1 this26 ay of- W sr b , 1990.

1 uo k b -e F -Notary Public, State of Wisconsin My Commission expires 6 9 0 .

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