ML20027C942

Forwards Responses to Nine Items in Eg Adensam 820609 Ltr Re Auxiliary Feedwater Sys,Per Draft Ser,Section 7.1.3.1

ML20027C942
Person / Time
Site:	Catawba
Issue date:	10/19/1982
From:	Tucker H DUKE POWER CO.
To:	Adensam E, Harold Denton Office of Nuclear Reactor Regulation
References
NUDOCS 8210280065
Download: ML20027C942 (9)

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DUKE POWER GOMPANY v.o.nox aaiso CHAMLoTTE, N.C. 28242 H AL 11. Tt'CHER TELEPHONE we raremm (704) 073~6531

" " " " * " " ~ " October 19, 1982 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Attention: Ms. E. G. Adensam, Chief Licensing Branch No. 4 Re: Catawba Nuclear Station Docket Nos. 50-413 and 50-414

Dear Mr. Denton:

Mr. R. L. Tedesco's letter of July 12, 1982 transmitted the preliminary draft SER from the Instrumentation and Control Systems Branch. Section 7 1 3 1 of this document identified two open items ((2) and (3)) related to the Auxiliary Feedwater System.

During a September 7-9, 1982 meeting with the Staff, Duke agreed to address the nine concerns identified in Ms. E. G. Adensam's letter of June 9, 1982.

This response is attached.

Very truly yours, jja/g k ker Hal B. Tucker [

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! Attachment cc: Mr. James P. O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission Region il 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303 l Mr. P. K. Van Doorn NRC Resident Inspector Catawba Nuclear Station Mr. Robert Guild, Esq.

Attorney-at-Law 314 Pall Hall Columbia, South Carolina 29201 {

8210280065 821019 PDR ADOCK 05000413 E PDR -

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Mr. Harold R. Denton, Director October 19, 1982 -

Page 2 cc: Palmetto Alliance 2135 Devine Street Columbia, South Carolina 29205-i Mr. Jesse L. Riley Carolina Environmental Study Group 854 Henley Place Charlotte, North Carolina 282C7 5

i Mr. Henry A. Presler, Chairman i

Charlotte-Mecklenburg Environmental Coalition 943 Henley Place Charlotte, North Carolina 28207 1

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RESPONSE TO ICSB INSTRUMENTATION AND CONTROL CONCERNS FOR CATAWBA AUXllIARY FEEDWATER SYSTEN Response to Concerns 1, 2, and 4 The auxiliary feedwater system can fulfill its safety function following an initiating event and assuming a single active failure and can do so without requiring operator action outside the control room for at least 30 minutes following any design basis event. The auxiliary feedwater system is not dependent upon the use of non-safe,ty grade equipment .or local operation of equipment to bring a unit to and maintain hot standby following any design basis event for which system function is required.

Hot standby is recognized as being a safe plant condition. Following unit transients, the unit will be taken to and maintained at hot standby fc a period of time sufficient to assess the situation and take the necessary corrective actions. The unit can be taken to and maintained at hot standby utIIIzing the safety grade main steam safety valves to control steam generator pressure and safety grade auxiliary feedwater isolation valves to control steam generator level . These are safety grade components and do not require local manual operation.

Normally the steam generator power operated relief valves (PORVs) will l be used to control steam generator pressure during hot standby and must be used to control the rate of heat removal while taking the plant to cold shut-down. These valves are pneumatically operable from the control room and the l

auxillary shutdown panels. The air supply system to these valves is highly l

reliable but is not safety grade. The unit can be taken to a cold l

shutdown condition by manually operating the steam generator l

PORVs using l ocal handwheels in the event instrument air o

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Is not available. Operation of these valves is not required to achieve or maintain hot standby. Manual operation of the valves is acceptable to achieve cold shutdown considering the time frame involved (generally cooldown will be preceded by an hour or more of hot standby) and the fact that hot standby can be maintained without the use of the PORVs.

Normal 1y the auxiliary feedwater control valves will be used to control steam generator level during hot standby and cooldown. These valves are pneumatically operable from the control room and the auxiliary shutdown panels. The air supply system to,these valves is highly re11able but is not safety grade. Operation of these valves is not required to achieve or maintain hot standby. The safety grade auxiliary feedwater isolation valves can be used to control steam generator level in the event instrument air is not available. These valves are operable from the control room and the auxillary shutdown panels and are not dependent on any non-safety equipment. Alternately, the auxiliary feedwater control valves can be manually throttled using local handwheels if instrument air is lost.

The steam generator PORVs and auxiliary feedwater control valves are supplied control air by the instrument Air System which is 9-safety grade but consists of redundant equipment and can be supplied blackout power.

Instrument air can be provided by any of the three instrument cir compressors or either of the two station ai r compressors which automatically backup Instrument ai r. The Instrument air compressors and dryers can be manually loaded on the blackout bus during sequence #13 no later than 12 minutes in the event of a station blackout. Based on the above, the complete unrestoreable loss of instrument air is very unlikely. However as discussed above the design of the auxiliary feedwater system provides the capability to reach and maintain a stable

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hot shutdown condition and subsequently proceed to cold shutdown without the use of instrument air.

Response to Concern 3 Operator action to control auxiliary feedwater flow is not required prior to 10 minutes af ter system initiation.

In addition to normal control via the auxiliary feedwater control valves, control of steam generator level from the control room is provided which is not dependent upon non-safety grade equipment and can be accomplished assuming a single active failure. Steam generator level may be controlled from the

< control room by either of two sa fety related means. Steam generator level may be controlled by starting and stopping the auxiliary feedwater pumps or by opening and closing the auxiliary feedwater safety grade isolation.

valves. Each steam generator can be supplied auxillary feedwater from both a motor driven pump and the turbine driven pump. Lines from each of the two pump sources to a steam generator each contain an auxillary feedwater Isolation valve. These valves are powered from the train of Essential AC power l

associated with their pump drive. This means that those valves associated l with Steam Generator's AG B fed from Motor Driven Pump A are powered from Train A. Those valves associated with Steam Generator s C & D fed from Motor 8

l Driven Pump B are powered from Train B. ,The valve arrangement for the Turbine

! Driven Pump is as follows; Steam Generator A & B Block Valves are powered l

from Train B, and Steam Generator C & D Block Valves are powered from Train A.

All valves are powered by 575 VAC fed from Essential Motor Control Centers.

These means of controlling steam generator level are safety grade and provide the redundancy necessary to satisfy single failure requirements.

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Normally the auxiliary feedwater control valves will be used to control steam generator level. These valves are pneumatically operable from the control room and auxiliary shutdown panels. Power for the Control Valve electronic signal loops is associated in a similar manner as the block valves except fed from the inverter-backed 240/120 VAC Auxiliary Control Power system. Those sources for the control valves for Steam Generator A & B Motor Driven Pump and Steam Generator C & D Turbine Driven Pump are the same while the source for Steam Generator C & D Motor Driven Pump and Steam Generator A $ B Turbine Driven Pump are the same.

These valves receive control air from reliable non-safety grade instrument ai r systems. Redundant and safety grade means of controlling steam generator level is provided by auxiliary feedwater isolation valves and by stopping and starting the auxiliary feedwater pumps. Addltionally, the auxiliary feedwater control valves can be manually operated utilizing a local handwheel to control steam generator level.

Response to Concern 5 ,

Termination of auxiliary feedwater flow to a faulted steam generator l Is not required prior to 30 minutes following development of the faulted condition.

The auxillary feedwater safety grade isolation valves or auxiliary feedwater control valves may be used to terminate flow to a faulted steam generator.

These valves provide redundant means of isolating auxiliary feedwater to a faulted steam generator. The safety grade auxiliary feedwater isolation valves may be operated from the control room, auxiliary shutdown panels, or locally and have safety grade power supplies and controls. In case of a failure of an isolation valve, the auxiliary feedwater control valves may be operated from

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r the control room or auxiliary shutdown panels if Instrument air is available.

If instrument air is not available, the valves may be manually closed.

These valves are located in the auxiliary feedwater pump room (which is quickly accessible from the control room), have handwheels for manual operation, and are accessible to the operator. Operator action outside the 4

control room under postulated single failure conditions is justifiable considering the location of the valves and since termination of flow is not required within 30 minutes.

Response to Concern 6 The Catawba Auxiliary Feedwater System is designed with a " Flow Optimization / Runout Protection" feature which will provide capability to terminate motor driven Auxillary Feedwater flow to either Steam Generator B or C If a faulted condition occurs with these steam generators or associated piping. This feature conforms to the requirements as stated in GDC-2 and GDC-4 in order to assure that they will not inadvertently operate due to the external influences as described in the above design criteria. These ,

circuits are an independent feature of the auxiliary feedwater system and will not compromise other circuitry associated with required system performance.

Response to Concern 7 j The Catawba Auxiliary Feedwater system design contains provisions to insure that no flow path is blocked by system control features.

The control valves are fitted with a sa fety class solenoid which vents air from the operator and falls the valve open to assure flow.

The Isolation valves are normally open except those on Steam Generators A & D associated with the Turbine driven pump. The safety grade isolation valves have Indicating lights in the control room and computer alarms in conjunction with l Inputs to the bypassed and inoperable status indication system. i Pump suction isolation valves are open and have power removed f rom the motors to insure open status. Supply source valves are also normally open

from the condensate grade sources. The nuclear service water sources are normally closed, but two trains are provided and either will open upon a low suction pressure signal from system logic circuits.

All motor operated suction isolation valves have inputs to the bypassed and inoperable status indication system. The manual valves associated with the flow paths are physically locked in the. open position to ensure an open flow path. The manual valves associated with pump performance testing and which are used during scheduled testing have inputs to the bypassed and inoperable status indication system. -

Besponse to Concern 8 a) As discussed in the response to ICSB Concern 7, those remotely operated valves that are capable of blocking flow to a pump or steam generator are either failed open upon automatic initiation, have safety grade control room position indication, have inputs to the bypassed and inoperable status indication system, or are locked open. All manual valves except those associated with pump performance testing are locked open. The performance test valves have inputs to the bypass and inoperable status panel, b) The Catawba Auxiliary Feedwater system does not have a single valve or multiple valves in series which could be placed in a position which could block all system flow.

I Response to Concern 9 The Power Operated Relief Valve solenoid valves are powered from the i

class IE 125 VDC Auctioneered Power System. These valves receive power i

! from two battery systems through an auctioneering scheme that allows botS I

the 125 VDC Vital Instrumentation and Control batteries and th'e Diesel Generator starting batteries to supply source voltage. These valves are designed to close upon loss of power or loss of motive air.. This is l

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a falisafe position which assures isolation of a steam generator. These valves may be reset from the control room and throttled for a controlled cooldoen. If both of the above described sources are not available, then manual handwheels are provided to allow manual throttling.

o RESPONSE TO

SUMMARY

OF MAJOR CONCERNS

1) See response to ICSB concerns 1, 2, & 4. A safety grade air system is not required to achieve or' maintain hot standby from the control room.

Hot standby is a safe plant condition. Operator action outside the control

, room during plant cooldown is acceptable as justified considering the time frames involved.

2) See response to ICSB concern 3

. 3) See response to ICSB concern I, 2 & 4.

4) See response to ICSB concern 5

5) As discussed in the response to ICSB Concerns 7 & 8 the manual handwheel operat'ed valves are locked open. Those valves that are frequently used for testing purposes have inputs to the bypassed and inoperable status indication system to alert the operator if they are not closed.

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