ML19254D505

Forwards Generic & plant-specific Requirements for Auxiliary Feedwater Sys

ML19254D505
Person / Time
Site:	Farley
Issue date:	10/13/1979
From:	Eisenhut D Office of Nuclear Reactor Regulation
To:	Barton A ALABAMA POWER CO.
References
TAC-12391, TAC-12963, NUDOCS 7910260103
Download: ML19254D505 (23)

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C W ASHINGTON. D. C. 20555 9,

r.u. 3 ms Docket No.: 50-348 Mr. Alan R. Barton Senior Vice-President Alabama Power Company P. O. Box 2041 Bimingham, Alabama 35291

SUBJECT:

NRC REQUIREMENTS FOR AUXILIARY FEEDWATER SYSTEMS AT JOSEPH M. FARLEY NUCLEAR PLANT, UNIT 1 The purpose of this letter is to advise you of our requirements for the auxiliary feeGater systems at the subject facility. These requirements were identiried during the course of the tRR Bulletins and Orders Task Force re,iew of operating reactors in light of the accident at Three Mile Island, Unit 2. to this letter identifies each of the requirements applicable to the subject facility. These requirements are of two types, (1) generic requirements applicable to most Westinghouse-designed operating plants, and (2) plant-specific requirer.:ents applicable only to the subject facility. centains a generic request for additional information regarding auxiliary feedwater sysam flow recuirements.

The oesigns and procedures of the subject facility should be evaluated against the applicable requirements specified in Enclosure 1 to detemine the degree to which the f acility currently conforms to these requirements. The results of this evaluation and an asscciated schedule and comitment for implementation of required changes or actions should be provided for tac staff review within thirty days of receipt of this letter. Also, this schedule should indicate your date for submittal of information such as design changes, procedure changes or Technical Specification changes to be provided for staff review. You may also provide your response to the items in Erclosure 2 at that time.

In addition to the requirements identified in this letter, other requirements which may be applicable to the suoject facility are expected to be generated by the Bulletins and Orders Task Force. Such requirements are those resulting from our review of the loss-of-feedwater event and the small break loss-of-coolant accident as described in the Westinghouse report WCAP-9600, " Report on Small

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Mr. Alan R. Barton - t c u-Break Accidents for Westinghouse NSSS System."

Our specific concerns include systems reliability (other than the auxiliary feedwater system), analyses, guidelines and procedures for operators, and operator training.

We plan to identify, in separate correspondence, the requirements resulting from the additional items frcm the Bulletins and Orders Task Force review.

Sincerely,

,],N'.hib Eb t d.s

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Darrell G. Eisenhut, Acting.irector Division of Operating Reactors Office of Nuclear Reactor Regulation Enclosures :

As stated

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Mr. Alan R. Barton Alabama Power Company 4M 3 '075 cc: Ruble A. Thomas, Vice President Sout'iern Services, Inc.

Post Office Box ?625 Biniiingham, Alabama 35202 George F. Trewbridge, Esquire Shaw, Pittman, ?otts and Trowbridge 1800 M Street, N.W.

Washington, D. C.

20036 John Bingham, Esquire Balch, Bingham, Baker, Hawthorne, Williams and Ward 600 North 18th Street Birmingham, Alabama 35202 Edward H. Keiler, Esquire Keiler and Buckley 9047 Jefferson Hignway River Ridge, Louisiana 70123 George S. Houston Memorial Library 212 W. Burdeshaw Street Dothan, Alabama 36303

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ENCLOSURE 1 X.3 (W)

FARLEY l AUXILIARY FEEDWATER SYSTEM X.q.1

System Description

X.3.1.1 Configuration. Overall Design i

The auxiliary feedwater (AFW) system as shown in the attached simplified diagram consists of three pumps (2 motor driven, I t urbine driven) each of which is normally lined up to feed all three steam generators. The motor driven pump discharges are cross connected through manually operated, locked-open valves upstream of the mot 3r operated isolation valves to each steam generator. The turbina driven pump supplies each steam generator down-stream of the motor operated steam generator isolation valves and the auxiliary feedwater control valves.

Check valves are provided downstream of the feedwater control valves that will prevent reverse flow through the control valves.

The primary water supply source for the AFW system is a 500,000 gallon capacity condensate etorage tank (CST).

150,000 gallons are reserved for decay heat removal in the event of an accident.

The licensee states that this reserve capacity is sufficient to maintain the plant at hot standby for two hours and cooldown to conditions that the RHR system can be oper-I ated.

The CST is normally lined up to supply water to the AFW pumps, through redundant lines (one to the motor driven pumps and t e to the turbine driven pump) through locked-open, manually operated 1.: lation valves.

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2-A backup long term source of water supply is provided by redundant service water trains.

Two normally closed motor operated valves in series isolate the service water trains from the auxiliary feedwater system.

These valves can be operated from the control room (key locked) to initiate service water flow to the AFW system. One SWS train is normally lined up to supply a motor driven pump and a turbine driven pump; the redundant SWS train normally supplies the other motor driven pump. With manual valve operation outside the control room, each SWS train can supply all three AFW pump suctions.,

X.3.1.2 Components All components of the auxiliery feedwater system are designed to Quality Group C, seismic Category I requirements including motor, pumps, piping, valves, and valve operators.

The auxiliary feedwater control valves, which are the only normally closed valves in the system flow path, are air operated and DC power controlled.

The air system is non-safety grade and the control valves will fail oper. on loss of air or DC control power.

X.3.1.3 Power Sources The motor driven pumps are powered from independent Class lE emergency buses supplied by the diesel generators.

All valves in the motor driven trains are A-C motor operated or manual valves with the exception of the auxiliary feedwater control valves which are air operated and controlled by DC power.

One air compressor can be powered by the diesel-generators to supply air, but it is not safety-grade. The control valves will fail open for maximum AFW flow on loss of air or DC power.

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, The turbine driven train can be operated and controlled from the control room, independently of AC power.

The steam inlet valves are air operated, fail closed, with a one-hour air accumulator available for valve operation upon loss of air. The accumulator will open the valve and keep it open upon loss of instrument air supply.

DC control power is used to actuate valve operation.

l i

The backup service water system supply series isolation valves are powered from the same Class lE bus that powers the service water system train and motor driven AFW pump train. Therefore a single failure of one bus will not disable both backup service water supplies.

There are two motor operated series isolation valves in the flow paths to each steam generator from the motor driven pumps that are powered from separate Class lE buses such that a single failure of a bus will not prevent isolation of an affected steam generator following a main steam or feedwater line break.

The circuit breakers for the motor driven pumps require DC control power to operate and energize the AFW motors.

These breakers can be manually closed locally without DC power.

X.3.1.4 Instrumentation and Controls X.3.1.4.1 Controls I

t Steam generator level is controlled manually from the control room.

Flow l

l to the steam generators from the motor driven pumps is controlled by I

I

. edulating three flow control valves, one to each steam generator.

These valves open for full flow to the steam generators following AFW system initiation.

This flow cannot be varied if the system was automatically started by a safety injection signal, until the injection signal has been reset which is 60 seconds after the receipt of the signal.

The flow to each steam generator from the turbine driven pump will normally be controlled from the control room by varying turbine speed. The flow control valves,to each steam generator from the turbine driven pump will normally be kept full open.

Each pump and all motor operateo and air operated valves can be operated from the control room and are powered from essential Class lE buses.

X.3.1.4.2 Information Available to Operator The control room operator has the following indications and alarms avail-able in the control room.

1.

Motor driven Aux Feedwater Pumps a.

Ammeter b.

Breaker Status c.

Monitor Light (Pump Running) d.

Fault Trip Alarm (overcurrent) e.

Pump in Local Control Alarm f.

Breaker Fails to Close Alarm (Loss of Offsite Power & SIAS) indication and alanE 9

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l 2.

St.m Admission Valves Turbine Driven AFW Pump a.

Valve Status indication P

b.

Monitor Light c.

Valve in Local Control Alarm d.

Turbine Driven Pump - Fault Alarm - (Overspeed Trip, Steam Valves Closed with Demand Signal) l, 3.

General a.

Valve Position Indication for all motor and air operated valves b.

Turbine Speed c.

Turbine Steam Pressure d.

Flow to each Steam Generator e.

Pump Discharge Pressure f.

Pump Suction Pressure g.

Condensate Storage Tank Level h.

Steam Generator Level i.

Low Suction Pressure Alarm to each pump j.

Loss of Ventilation Cooler for each motor driven pump room 1.

Hi.to Suction flow alarm i

X.3.1.4.3 Initiating Signals for Automatic Operation Motor Driven Pumos 1.

Lo-Lo S/G 1evel 2 out of 3 detectors to any one steam generator

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. 2.

Both Main I-ad Pumps Trip (senses stop valve to turbine driven main feed pumps) 3.

Loss of offs,ite power or two out of three undervoltage condition on respective ESF buses.

4.

Safety Injection Signal Turbine Driven Pump I

1.

Lo-Lo Steam Generator Level 2 out of 3 detectors to any 2 Steam Generators 2.

Undervoltage to any two of three reactor coolant pump buses, t

X. 3.1. 5 Testinq 1.

The motor driven pumps and the turbine driven pump are tested for operability by recirculation back to the condensate storage tank monthly. Each valve in the auxiliary feedwater system flow path or bypass flow path that is not locked,' sealed or otherwise secured in position is verified to be in its correct position at least once per month. Motor operated stop check valves in AFW discharge to each steam generator are verified to be open with the breaker to the valve operators locked open at least cnce a month.

2.

At least once per 18 months during shutdown:

Verify that the motor driven pumps will start upon receipt of a.

the following signals:

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(1) Loss of main feedwater pumps (2) safety injection signal (3) steam generator water level low-low from one steam generator (4) loss of offsite power b.

Verify that the steam turbine driven pump starts automatically upon receipt of the following:

(1), Blackout Signal (undervoltage to RCP buses )

(2) Steam generator low-low water from two steam generators Valve operability tests are performed quarterly on motor and air operated valves.

Stroke tests for these valves are performed quarterly.

X.3.1.6 Technical Specifications With any one auxiliary feedwater pump inoperable, restore three auxiliary feedwater pumps (2 motor, 1 steam) to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in Hot Shutdown within next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. This is in accordance with limiting conditions for operation of Standard Technical Specifications.

'^'9 062 X.3.2 1 liability Evaluation X.3.2.1 Dominant Failure Modes The do.n ant failure modes are expressed for three transient situations.

Success criterion is the operation of at least one of the three pump trains.

LOFW with Offsite Power Available The unavailability of the AFWS during this type of transient is dominated by several combinations of three failure elements.

These include test and maintenance autages and hardware failures in various combinations and a combination of failures in source lines from the condensate storage tank along with failure of the service water system backup.

Test and maintenance outages of turbine driven pump train and motor driven pump trains are based on monthly pump tests as well as 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowable maintenance periods for each train. The hardware failures of for the motor driven pump trains include pump failure, in-line valve failures and control signal failure to the pumps.

The hardware failures for the turbine driven p imp train include pump failure, in-line valve failures and valve f ailures in the steam supply lines, including control of steam inlet valves.

While the determination of dominant failure contributors is based on systems of this type in general, specific failure data for_Farley in its early life shows a series of failure on demand due to trip throttle valve action at the steam inlet to the turbine driven pump.

Failures of the supply line valves in the closed position are considered independent human errors.

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LOFW with loss of Offsite Power but with Onsite AC Availabl The conditional unavailability of the AFWS during this type of transient is dominated by the same failure contributors as in the LOFW with Offsite Power Available transient with the addition that failure of one of the two motor driven pump trains can come from potential.one train failure of onsite power.

LOFW with less of all AC, DC Available Only the steam' turbine driven pump train can be operable in this type of l

situation and failure contributors include test and maintenance and hardware single failure elements. Also included is a failure to manually reset steam inlet valves which are operated by AC derived compressed air.

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).3.2.2 Interdependencies l

l The principal noted dependency is the AC derived compressed air which operates the steam turbine steam inlet valves.

Loss of AC and compressed l

air supply result in eventual bleed-off and fail-closed of the steam inlet valves.

X.3 Recommendations for this Plant The short-term recommendations (both generic, denoted by GS, and plant-specific) identified in this section represent actions to improve AFW system reliability that should be implemented by January 1, 1980, or as soon thereafter as is practicable.

In general, they involve upgrading of Technical Specifications or establishing procedures to avoid or mitigate potential system or operator failures. The long-term (both generic,

'^~9 064 denoted by GL, and plant-specific) recommendations identified in this sec-tion involve system design evaluations and/or modifications to improve AFW system reliability and represent actions that should be implemented by January 1, 1981, or as soon thereafter as is practicable.

X,.3.3.1 Short-Term Recomendation GS Emergency procedures for transferring to alternate 1.

sources of AFW supply should be avail.able to the plant operators. These procedures should include criteria to inform the operator when, and in what order, the transfer to alternate water sources should take place. The following cases should be covered by the procedures:

The case in which the primary water supply is not initially e

avail able. The procedures for this case should include any operator actions required to protect the AFW system pumps l

against self-damage before water flow is initiated; and, I

The case in which the primary water supply is being depleted, l

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The procedure for this case should provide for transfer to the alternate water sources prior to draining of the primary water supply.

Recommendation GS The as-built plant should be capable of pro-2, viding the required AFW flow for at least two hours from one AFW pump If manual train independent of any alternating current power source.

AFW system initiation or flow control is required following a complete loss of alternating current power, emergency procedures should be estr.olished for manually initiating and controlling the system under these conditions: Since the water for cooling of the lube

'^'9 065 oil for the turbine-driven pump bearings may De dependent on alter-nating current power, design or procedural changes shall be made to eliminate this dependency as soon as practicable. Until this is donc, the emergency procedures should provide for an individual to be stationed at the turbine-driven pump,in the event of the less of all alternating current power to monitor pump bearing and/or lube oil temperatures.

If necessary, this operator would operate the turbine-driyen pump in an on-off mode until alternating current power is restored. Adequate lighting powered by direct current power sources and communications at local stations should also be provided if manual initiation and control of the AFW system is needed.

(See Recommendation GL-3 for the longer-term resolution of this concern.)

Rec mmendation GS The liccnsee should confirm flow path avail-3.

ability of an AFW system flow train that has been out of service to perform periodic testing or maintenance as follows:

o Procedures should be implemented to require an operator to determine that the AFW system valves are properly aligned and a second operator to independently verify that the valves tre properly aligned.

The licensee should propose Technical Specifications to e

assure that prior to plant startup following an extended cold shutdown, a flow tent would be perforced to verify the normal flow path from the primary AFW system water source to the steam generators.

The flow test should be-conducted with AFW system valves in their normal alignment.

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Recommendation GS The licensee should verify that the automatic i

start AFW system signa',s and associated circuitry are safety grade.

If this cannot be verified, the AFW system automatic initiation system should be modified in the short-term to meet the functional requirements listed below.

For the longer term, the automatic initia-tion signals and circuits should be upgraded to mr.et safety grade

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requirements as indicated in Recommendation GL-5.

The design should provide for the automatic initiation of the auxiliary feedwater system flow.

The automatic initiation signals and circuits should be designed so that a single failure will not result in the loss of auxiliary feedwater system function.

Testability of the initiation signals and circuits sha'l be a feature of the design.

The initiation signals and circuits should be powered from the emer-gency buses.

t Manual car:5ility to initiate the auxiliary feedwater system from the control room should be retained and should be implemented so that a single failure in the manual circuits will not result in the loss of system function.

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The alternating current motor-driven pumps and valves in the auxiliary i

feedsater system snould be included in the automatic actuation (simul-taneous and/or sequential) of the loads to the emergency buses.

The actomatic initiation signals and circuits shall be designed so that their failure will not result in the loss of manual capability to initiate the AFW system from the control room.

e X.3.3.2 Additional Short-Term Recommendations The following aeditional short-term reccamendations resulted from the staff's Lessons Learned Task Force review and the Bulletins and Orders Task Force review of AFW systems at Babcock & Wilcox-cesigned operating plants subsequent to cur review of the AFW system cesigns at W-and C-E-designed crerating plants.

They have not been exami.ned for specific applicEbility to this facility.

1.

Recommendatior - The licensee should provide redundant level indica-tions and low icvel alarms in the control room for the AFW system primary water supply to allow the operator to anticipate the need to make up water or transfer to a'i alternate water surply and prevent a low pump suction pressure condition from occurring.

The low level

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alarm setpoint should allow at least 20 r.utes for operator action, assuming that the largest capacity AFW pump is operating.

2.

Recommendation - The licensee should perform a 72-hour endurance test on all AFW system pumps, if such a test or continuous period of operation has not been accomplished to date.

Following the 72-hour pump run, the pumps should be shut down and cooled down and then

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restarted and run for one hour.

Test acceptance criteria should include demonstrating that the pumps remain within design limits with respect to bearing / bearing oil temperatures and vibration and that pump room ambient conditions (temperature, humidity) do not exceed environmental qualification limits for safety-related equipment in the room.

3.

Recommendation - The licensee should implement the following requirements as specified by Item 2.1.7.b on page A-32 of NUREG-0578:

" Safety-grade indication of auxiliary feedwater flow to each steam generator shall be provided in the control room.

The auxiliary feedwater flow instrument channels shall be powered from the emergency buses consistent with satisfying the emergency power diversity requirements for the auxiliary feedwater system set forth in Auxiliary Systems Eranch Techn-nical Position 10-1 of the Standard Review Plan, Section 10.4.9."

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Recom endation - Licensees with plants which require local "Inual realignment of valves to conduct periodic tests on one AFE system train and which have only one remaining AFW train available for cperation, should propose Technical Specifications to provide that a dedicated incividual who is in communication with the control room be stationed at the manual vr.lves. Upon inst-uction from the control room, this operator would re-align the valves in the AFW system train from the test mode to its operational alignment.

X.3.3.3 Long-Term Leng-term r commendations for improving the system are as follows:

e Recom endaticn GL At least one AFW system pump and its 1.

associated flow path and essential instrumentation should auto-matically initiate AFW system flow and be capable of being operated independently of any alternating current power source for at least Conversion of direct current power to alternating current two hours.

is acceptable.

2.

Recommendation GL The licensee should upgrade the AFW system automatic initiation signals and circuits to meet safety grade requirements.

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Auxiliary Feedwater System Farley 1 Figure 1 I

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' ENCLOSURE 2 W

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B. asis for Auxiliary Feedwater i

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System Flou Reouirements As a result of recent staff reviects of operatin; plant Auxiliary Feed-water Systems (AFMS), the staff concludes that the design bases and criteria provided by licensees for establishing AFWS requirements for flow to the steam generator (s) to assure adequate removal of reactor decay heat are not well defined or documented.

We require that you provide the following AFWS flow design basis infor-mation as applicable to the design basis transients and accident con-ditions for your plant.

Identify the plant transient and accident conditions considered 1.

a.

in establishing AFWS flow requirements, including the following events:

d

1) Loss of Main Feed (UW)

2) LMFW w/ loss of of fsite AC power

3) LMFW w/ loss of onsite and offsite AC power

4) Plant cooldown

5) Turbine trip with and without bypass E) Main steam isolation valve closure

7) Main feed line break

8) Main steam line break

9) Small break LOCA

10) Other transient or accident conditions not listed above b.

Describe the plant protection acceptance criteria and corres-ponding technical bases used for each initiating event identi-fied above. The acceptance criteria should address plant limits such as:

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- Maximum RCS pressure (PORY or safety valva actuation)

- Fuel temperature or damage. limits (DNS, PCT, maximum fuel central temperature)

- RCS cooling rate limit to avoid excessive coolant shrinkage

- Minimum steam generator level to assure sufficient steam generator heat transfer surface to remove decay heat and/or cool down the primary system.

2.

Describe the analyses and assumptions and corresponding technical justification used with plant condition considered in 1.a. above including:

Maximum reactor power (including instrument error allowance) a.

at the time of the initiating transient ors. accident.

b.

Time delay from initiating event to reactor trip.

Plant parameter (s) which initiates AFWS flow and time delay c.

between initiating event and introduction of AFWS flow into

, team generator (s).

d.

Minimum steam generator water level when initiating event occurs.

Initial steam generator water inventory and' depletion rate before e.

and after AFWS flow comences - identify reactor decay heat rate used.

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, Maximum pressure at which steam is released from steam generator (s) f.

and against which the AFW pump must develop sufficient head.

Minimum number of steam generators that must receive AFW flow; g.

e.g. 1 out of 2?, 2 out of 47 h.

RC flow condition - continued operation of RC pumps or natural circulation.

i. Maximum AFW inlet temperature.

j. Following a postulated steam or feed line break, time delay assumed' to isolate break and direct AFW flow to intact steam gene'rator(s). AFW pump flow capacity allowance to accommodate the time delay and mair.';ain m'inimum steam generator water level.

o Also identify credit taken for primary system heat removal due to blowdown.

k.

Volume and maximum temperature of water in main feed lines between steam generator (s) and AFWS connection to main feed line.

1.

Operating condition of steam generator nomal blowdown following initiating event.

Primary and secondary system water and metal sensible heat m.

used for cooldown and AFW flow sizing.

Time at hot standby and time to cooldown RCS to RHR system cut n.

in temperature to size AFW water source inventory.

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3.

Verify that the ARI pumps in your plant will supply the necessary flow to the steam generator (s) as,detemined by items 1 and 2 above considering a single failure. Identify the margin in sizing the pump f".ow to allow for pump recirculation flow, seal leakage and pump wear.

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