ML19260A004

Advises of NRC Requirements for Auxiliary Feedwater Sys. Generic & plant-specific Requirements Encl

ML19260A004
Person / Time
Site:	Beaver Valley
Issue date:	10/11/1979
From:	Eisenhut D Office of Nuclear Reactor Regulation
To:	Dunn C DUQUESNE LIGHT CO.
References
TAC-12520, TAC-44632, NUDOCS 7910260280
Download: ML19260A004 (23)

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NUCLEAR REGULATORY COMMISSION l

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Cocket No.: 50-334 i

Mr. C. N. Dunn, Vice-President l

Cperations Division i

Duquesne Light Company 435 Sixth Avenue Pittsburgh, Pennsylvania

SUBJECT:

NRC REQUIREMENTS FOR AUXILIARY FEEDWATER SYSTEMS AT BEAVER VALLEY UNIT 1 The purpose of thi's letter is to advise you of our requirements for the auxiliary feedwater systems at tne subject facility. These requirements were identified during the course of the NRR Bulletins and Orders Task Force review 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 requirements applicable only to the subject facility. contains a 2neric recuest for acditional information regarding auxiliary feedwater synem flow requirements.

The designs and procedures of the subject facility should be evaluated against the appl teaDie requirements specified ic Enclosure I to detemine tlie degree to which the facility currently conforms to these requirements. The results of this evaluation and an associated schedule and comitment for implementation of required changes or actions shoula be provided for NRC 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 Enclosure 2 at that time.

In accition to the requirements identified in this letter, other requirements which may be applicaole to the subject facility are expected to be generated by the Bulletins anc Crders Task Force. Such recuirements are those resulting from our review of tne loss-of-feedwater event and the small brea.k loss-of-coolant accicent as described in the Westinghouse report WCAP-9600, " Report on Small 1212 240 7 910260 EFO

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Mr. C. N. Dunn -

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Break Accidents for 'aestinghcuse NSSS System."

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

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

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Vi!Lka Darrell G. Eisenhut, Acting Director Division of Operating Reactors Of fice of Nuclear Reactor Regulation Enclosu es:

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o e-O P00R ORGINAL Mr. C. N. Dunn Duquesne Light Company OCTG32R..W cc: Gerald Charnoff, Esquire Mr. James A. Werling Jay E. Silberg, Esquire Plant Superintendent Shaw, Pittman, Potts and Trowbridge Beaver Valley Power Station 1800 M Street, N.W.

P. O. Box 4 Washington, D. C.

20036 Shippingport, Pennsylvania 15077 Karin Carter, Esquire Mr. John A. Levin Special Assistant Attorney General Public Utility Commission Bureau of Administrative Enforcement P. O. Box 3265 5th Floor, Executive House Harrisburg, Pennsylvania 17120 Harrisburg, Pennsylvania 17120 Mr. Rorar Tapan Stone and Webster Enginec ing Corporation P. O. Box 2325 Boston, Massachusetts 02107 Mr. J. D. Woodward R & D Center Westinghouse Electric Corporation i.uilding 7-303 Pittsburgh, Pennsylvania 15230 B. F. Jones Memorial Library 663 Franklin Avenue Aliquippa, Pennsylvania 15001 Mr. Jack Carey Technical Assistant Duquesne Light Company P. O. Box 4 Shippingport, Pennsylvania 15077 Mr. R. E. Martin Duquesne Light Conpany 435 Sixth Avenue Pittsburgh, Pennsylvania 15219 Marvin Fe'n Utility Counsel City of Pittsburgh 313 City-County Building

?ittsburgh, Pennsylvania 15219 1212 242

ENCLOSURE 1 X (W)

BEAVER VALLEY UNIT 1 AUXILIARY FEEDWATER SYSTEM X.1.1 System Descriotion X.1.1.1 Conficuration, Overall Design A simplified flow diagram of the Beaver Valley Plant, Unit No. 1, Auxiliary Feedwater System (AFWS) is shown in Figure 1.

The AFWS consists of one turbine driven pump (700 gpm F.o96 ft head), and two motor driven pumps (350 gpm @ 2696 ft head).

The pump discharge headers are connected to permit auxiliary feedwater delivery to any one or all three steam generators by any AFW pump. The licensee states that for normal and transient plant operation, including loss of main feedwater flow, only one pump is required to cool the plant down to the condition where the RNR system can be put into operation to continue safe plant shutdown.

However, in the event of an unisolable main steam or main feed line break, either one turbine-driven AFW pump or both motor-driven pumps are required to prever't dryout of the steam generators.

The primary water supply of the AFWS is maintained in a 140,000 gallon seismic Category 1, primary plant domineralized water storage tank (CWST). The tank is reserved str'ctly for the AFWS pump usage.

The reserved water inventory is sufficient to maintain the plant at hot standby condition for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> following a reactor trip.

Low waten 1212 243

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P00R ORGINAL level in the DWST will alarm and annunciate in the main control room.

The secondary water supply is the seismic Category I river water system with an additional backup source from the fire protection system.

X.1.1 2 Components - Design, Classification All pumps, valves, piping, instrumentation and controls associated with the auxiliary feedwater system are designed to seismic Category I requiremen'6 -

The primary water source (Demineralized Water Storage Tank) and the secondary water source (River Water System) are also designed to seismic Category I requirements. The additional backup water source from the fire protection system is not designed to seismic Category I requirements.

X.1.1. 3 power Sources The turbine driven pump is supplied with steam from each steam generator outlet header upstream of the main steam isolation valve (MSIV) and exhausts to the atmosphere.

The motor driven pumps receive power from the 4160 V AC vital buses.

In the event of a loss of offsite power, the pumps are powered by the Division A and B emergency diesel generators, respectively.

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. X.'.1.4 Instrumentation and Controls X.1.1.4.1 Controls The control of auxiliary feedwater flow and steam generator watsr level is accomplished from the main control rcom by manually operated control valves. These valves can also be manually operated from the local shutdown control panel if the control room is not accessible.

All manually operated valves in the main flow path of the AFWS are either " lock-opened" or " lock-closed" in their normal position.

The motor operated valves fail in their "as is" position.

X.1.1.4.2 Information Available to Coerator The important information available to the operation includes AFW discharge header pressure, AFW flow to each steam generator, DWST water level, steam generator water level, steam pressure to turbine driven AFW pump and control valve position indicators. Additional information available is in the following instrument list:

SPECIFIC INSTRUMENTATION AND CONTROL Flow Auxiliary feed flow to IA (8, C) Steam Generator FI-FW-100A (B, C)

Readout location: Vertical Board - Section C 1212 245 P00R ORIGINAL FI-FW-100A1 (8, C)

Readout location:

Emergency Shutdown Panel AUX STEAM GEN FEED PUMP AUTO START-STOP PRI PLNT DEMIN WTR STRGE TNK LVL H-L CH 1 PRI PLNT DEMIN WTR STRGE TNX LVL H-L CH 2 1/3 STM GEN 1A HI-HI LEVEL 1/3 STM GEN 1A LOW LOW WATER LEVEL STM GEN 1A LOW WTR LEVEL CH 1 STM GEN 1 LOW WTR LEVEL CH 2 1/3 STM GEN IB HI-HI LEVEL 1/3 STEAM GEN 18 LOW LOW WATER LEVEL STM GEN 18 LOW WTR LEVEL CH 1 STM GEN 18 LOW WTR LEVEL CH 2 1/3 STM GEN 1C HI-HI LEVEL 1/3' STM GEN IC tow LOW WTR LEVEL STM GEN IC LCW WATER LEVEL CH 1 STM GEN 1C LOW WATER LEVEL CH 2 AUX STM GEN FEED PUMP 3A START-STOP AUX STM GEN FEED PUMP 38 START-STOP AUX STM GEN FD PP 3A MTR INB0 BRG TEMP AUX STM GEN FC ? 3B MTR INB0 BRG TEMP AUX STM GEN FD PP 3A MTR OUTBD BRG TEMP AUX STM GEN FD PP 3B MTR OUTBD BRG TEMP

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P00R ORGINAL X.1.1.4.3 Initiating Signals for Automatic Operation The AFWS is automatically initiated.

It can also be started manually from the main control room.

In addition, the pumps can be manually started from the local shutdown control panel.

The automatic initiating signals are as follows.

1)

Turbine Driven Pump a) 1/3 Steam Generator Lo-Lo Level (1 out of 3 channel logic) b)

Under Voltage 2)

Motor Driven Pumps a) 2/3 Steam Generator Lo-Lo Level b)

Both Main Feed Pumps Trip c)

Safety Injection Signal d)

Turbine Driven AFW puep low discharce pressure consistent with a start signal on turbine driven pump.

e)

Loss of offsite power X.1.1 5 Testing The systems are tested periodically in accordance with technical specification requirements.

The frequency of periodic testing is 31 days.

In addition, the particular system is tested in accordance with the technical specification after performing system maintenance.

The systems are tested using the recirculating lines, with various plant parameters noted (suction and discharge pressures, etc). The 1212 247

v -meerns n?. 0~0R BRGk instrumentation system is checked periodically, in accordance with the technical specifications, on a per shift, monthly or refueling time frame basis.

X.1.1.6 Technical Soecifications A review of the technical specifications indicated that these specifications cover limiting conditions of operation (LCO) and periodic surveillance testing consistent with current standard Technical Specifications.

X.l.2 Reliability Evaluation X.1.2.1 Ocminant Failure Modes The following failure modes were found to dominate the demand unavailability of the Beaver Valley Unit 1 AFWS.

Los's of Feedwater (LOFW) with Offsite AC Available The dominant failure mode (>90%) for this transient event was assessed to be those possible coupled human errors in testing, i.e.,

leaving two or more of the manual block valves closed in the discharge side of the pumps while performing the type of pump flow testing required by the Technical Specifications.

The licensee has recognized this possibla common mode error and is planning to chain lock all manual valves into their correct alignment state. Further, the licensee will, in the future, stagger his pump)} S ..a

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P00RDMNAL + test program such that no more than one of the three pun:ps will be tested in any one shift. Considering implementation of these pro-cedures, the overall availability of the Beaver Valley AFWS design should be improved by roughly a factor of three. LOFW with only Onsite AC Available Assessment of the AFWS,given this transient event, indi:ated that there would be no significant change in the predicted unavailability of the Beaver Valley AFWS. Human error concerning mispositioned ~ block valves in the AFWS discharge remained the dominant failure mode. LOFW with only DC Available In this transient event,the Beaver Valley Unit 1 AFWS would be expected to automatically actuate and the human could serve as backup to'open any of the valving that failed to electrically respond. The dominant contributors to AFWS unavailability in this event were: allowed test and maintenance outage hardware faults (principally the failure of steam turbine pump) X.1.2.2 Principal Decendencies Identified The principal dependency identified was the human error (common mode) vunerability associated with manual closure of the AFWS discharge block valves and failure to reopen them. 1212 249 ~. - ~ ~..

P00R ORGINAL X.1.3 Recommendations for this Plant The short-term recommendations (both generic, denoted by GS and plant specific) identifiec 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 recommendations (both generic, denoted by GL and plant specific) identified in this section involve system design evalua-tions 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.l.3.* Short Term

1. ' Reconsnendation GS The licensee has stated that it throttles AFW system flow to avoid water ha.mer. The licensee should reexamine the practice of throttling AFW system flow to avoid water hammer.

The licensee should verify that the AFW system.will supply on demand sufficient initial ficw to the necessary steam generators to assure adequate decay heat removal follcwing loss of main feedwater flow and a reactor trip from 100% power. In cases where this reevaluaticn results in aniincrease in initial AFW system flow, the licensee should provide sufficient information to demonstrate that the required initial AFW system flow will not result in plant damage due to water haarner. \\2\\1 50 ? ~ ~. -. _ ~ -

_g_ P00R BRER 2 Recomendation GS Emergency procedures for transferring to alternate sources of AFW supply should be availabl.e to the plant operators. These procedures should inclurie 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: e The case in which the primary water supply is not initially available. The procedures for this case should include any operJ.or actions required to protect the AFW system pumps against self-damage before water flow is initiated; and, e The case in which the primary water supply is being depleted. The procedure for this case should. provide for transfer to the altemate water sources prior to draining of the primary water supply. 3. Reccmendation GS The licensee should confirm flow path availability of en AFW system flow train that has been out of service to perform periodic testing or maintenance as follows: 1212 2M =w e 9 -wg- .,p- .e-e-- e

O ?00R ORGINAL e Procedures should be implecented to require an operator to determine that the AFW system valves are properly aligned and a second operator to independently verify that the valves are properly aligned. e The licensee should propose Technical Specifications to assure that prior to plant startup following an extended cold shutdown, a flow test would be performed to verify the nomal 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 nomal alignment. 4. Recommendation GS The licensee should verify that the automatic start AFW system signals 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 initiation signals and circuits should be upgraded to meet safety grade requirements as indicated in Recomendation GL-5. The design should provide for the automatic initiation of the auxiliary feedwater system flow. }}2 7 -~ mwe -an. .m 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 shall be be a feature of the design. The initiation signals and circuits should be powered from the emergency buses. Manual capability to initiate the auxiliary feedwater system from the control rocm 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. The alternating current motor-driven pumps and valves in the auxiliary feedwater system should be included in the automatic actuation (simultaneous and/or sequential) of the loads to the emergency buses. The automatic initiation signals and circuits shall be designed so that their fai!ure will not result in the loss of manual capability to initiate the AFd system from the control room. 9 \\2\\2

P00R ORGINAL 5. Recomendation - The normally closed manually operated suction valves from the river water system to the AFWS should be periodically tested and the position verified. The licensee should propose appropriate Technical Specifications to incorporata these provisions. 6. Recomendation - The strengthened administrative procedures described in Section X.1.2.1 above should be implemented; namely, the locking of manual valves in the correct position and staggered testing of the AFW system pumps. The licensee has advised us that it p'lans to implement such strengthened procedures before Beaver Valley Unit 1 (currently shut down for reasons unrelated to this AFW system review) returns to power. 7. Recommendation - As shown in Figure 1, the locked block valves in each AFW pump discharge line are aligned so that the combined flow from one motor-driven pump plus one turbine-driven pump is supplied to the steam generators via one AFW header while flow from the remaining motor-driven pump is supplied to the steam generators via the redundant AFW header. As indicated in Section 1.1.1, the ifcensee states that.in the event of an unisolable main steam or main feed line break, the ficw from both mctor-driven pumps or from the turbine-driven pump is required to prevent dryout of the steam generators. The licensee should review the present alignment of the AFW pump discharge block valves and modify as necessary to provide the AFV required for normal, transient, and accident conditions. O 'h D ... _ M

300R ORGINAL ~"- X.1.3.2 Additional Short-Term Recocinendations The following additional short-term recocnendations resulted from the staff's Lessons Learned Task Force review and the Bulletins and Orders Task Force review of AFW systems:at Babcock & Wilcox-designed operating plants subsequent to our review of the AFW system designs at W and C-E-designed cperating plants. They have nnt been examined for specific applicability to this facility. 1. Recomendation - The licensee should provide redundant level indications and low level alarms in the control room for the AFW systeo primary water supply to allow the operator to anticipate the need to make up water or transfer to an alternate water supply and prevent a low pump suction pressure condition from occurring. The low level alarm setpoint should allow at least 20 minutes 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 vate. Following the 72-hour pump run, the pumps should be shut down and cooled down and than restarted and run for one hour. Test acceptance criteria should include demonstrating that the pumps remain within design limits wi'.h respect to bearing oil temperatures and vibration and that r ump room ambient conditions (temperature, e humidity) do not exceed environmental qualification limits for safety-related equipment in the room. Q)} 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 Branch Techn-nical Position 10-1 of the Standard Review Plan, Section 10.4.9." 4. Recommendation - Licensees with plants wnich require local manual realignment of valves to conduct periodic tests on one AFW system train M which have only one remaining AFW train available for operation, should propose Technical Specifications tc provide that a dedicated individual who is in communication with the control room be stationed at the manual valve Upon instruction from the control room, this operator would realign the valves in the AFW system train from the test mode to its operational alignment. \\ 2 \\,l C [3 Q3 .eu--- .up-mm- = =s.w -<an-

P00R ORIGINAL X.1.3.3 Long-Term Long-term recommendations for improving the system are as follows: 1. Recommendation GL The licensee should upgrade the AFW system automatic initiation signals and circuits to c.eet safety grade requirements. 2. Recommendation - As indicated in Section X.1.1.1, the plant requires flow from two motor-driven pumps c ' one turbine-driven pump for accident conditions. This design does not meet the high energy line break criteria in SRP 10.4.9 and Branch Technical Position 10 1; namely, that the AFWS should maintain the ci.pability to supply the required AFW flow to the steam generator (s) assuming a pipe break anywhere in the AFW pump a discharge lines concurrent with a single active failure. The licensee should complete an evaluation assuming such an event and (1) determine any AFW system modifications or procedures necessary to maintain the required AFW flow to the steam generator (s) or (2) describe how the plant can be brought to a safe shutdown condition by use of other available systems following such a postulated event. 9 gl\\2 ...---e. e--w-

I 9 OillEll ALTEllNATIVE WATER SOURCES e USE OF Fille lDIESE L PtJMPSI SYSTEM Weill filVEli WATEll e CONDENSATE 1IIANSFEH FROM COND F ROM illVEll llOTWELL WAT Ell SYS TEM O { 8G 30 SG j WT-TK 10 I LE I 140.000 GAL 3fg.. OEMIN g WAT[ll to Lo 510111NK MOV POSITION i t i r V LVES [LO O[LO hi hg j g j j g g-g- A" B" A B** MFW 'A r y LCw a J J r' A N Lc f n LO J E LECTRICAL LEGEND PUMPS n LO - LOCKED OPEN )4 LC - LOCKED CLOSED LO NO1E: 1HESE BLOCK VALVES ARE CLOSED FO - Fall OPENED ~~ D TullBINE Foll PullPOSE OF TESTING OF PUMPS. FC - FAIL CLOSED OftlVEN PUMP TEST OF MORE TilAN ONE PUMP PER FA - Fall AS IS g SOV SillFT WILL NOT BE Tile PflACTICE. ATM ' Tills STAGGER TESTING SilALL M - NORMALLY OPENED IMPROVE ON CilANCE OF MUCil N - NORMALLY CLOSED O l m. s IluMAN Elll10lls. NC. FO - MOTOR OPEllATED M M OV STOP & { p - AIR OPERA 1ED GOVERNOR ) r, NC, FO VALVING may POslTION I INDICATED F W VALVES Auxiliary Feedwat=. System CO Deaver Valley, Unit.1 figure 1.

a Sasis for Auxiliary Feesiater System Flow Reouirements As a result of recent staff reviects of operatin; plant Auxiliary Feed-water Systems (AFWS), the staff concludes that the design bases and criteria provided by licensees for establishing AFdS 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:

1) Loss of Main Feed (UiFJ)

2) LMFW w/ loss of offsite AC power

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

4) Plant cooldown

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5) Turbine trip with and without bypass

6) 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: 759 \\2\\t n. e,-- .m. -mm-me., -.--e. -e.

j - Maximum RCS pressure (PORV or safety valve actuation) - Fuel temperature or damage Jimits (DNB, PCT, maximum fuel cen :ral tenperature) - P.CS cooling rate limit to avoid excessive coolant shrinkage - itinimum 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 corr'esponding taennical justification used with plant condition considered in 1.a. above including: a. Maximum reactor power (including instrument error allowance) at the time of the initiating transientmreaccident. 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 steam generator (s), d. Minimum steam generator water level when initiating event occurs. e. Initial steam generator water inventory a'nd depletion rate before and after AFWS flow cocnences - identify reactor decay heat rate used. O 9 \\1\\1 ' e .e me._ww e e4 --www ee.- -+e e ee-en .me*W h amame. e - e siwh==i m

J.- P00R ORIGNAL f. Maximum pressure at which steam is released from steam generator (s) and against which the AFW pump must develop sufficient head. g. Minimum number of steam generators that must receive APA flow; e.g.1 out of 27, 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 generator (s). AFV pump flow capacity allowance to accomodate the time delay and maintain m'inimum steam generator water level.

Also identify. credit taken for primary system heat removal due to blowdown. k. Volume u2 c3ximum temperature of water in main feed lines between s. team generator (s) and AFWS connection to main feed line. 1. Operating condition of steam generator normal blowdown following initiating event. m. Primary and secondary system water and metal sensible heat used for cooldown and AFW flow sizing. n. Time at hot standby and time to cooldown RCS to RHR system cut in temperature to size AFW water source inventory. , o \\'l \\ -~- y-

P00R DHM ~ 3. Verify tha2 the AFri 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. low to allow for pump recirculation flow, seal leakage and pump wear. 9 S 9 8 e e O O e%., 9 9bL}}