ML19209A420

Forwards NRC Requirements for Auxiliary Feedwater Sys & Requests That Plant Designs & Procedures Be Evaluated Against Applicable Requirements to Determine Degree of Conformity

ML19209A420
Person / Time
Site:	Point Beach
Issue date:	09/21/1979
From:	Eisenhut D Office of Nuclear Reactor Regulation
To:	Burstein S WISCONSIN ELECTRIC POWER CO.
References
TASK-2.E.1.1, TASK-2.E.1.2, TASK-TM TAC-11692, TAC-11693, NUDOCS 7910030831
Download: ML19209A420 (23)

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September 21, 1979 Docket Nos.: 50-266 50-301 Mr. Sol Burstein Executive Vice-President Wisconsin Electric Power Company 231 West Michigan Street Milwaukee, Wisconsin 53201

SUBJECT:

NRC REQUIREMENTS FOR AUXILIARY FEEDWATER SYSTEMS AT POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 The purpose of this letter is to advise you of our requirements for the auxiliary feedwater systems at the 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.

Enclosu:a 1 to this letter identifies each of the requireme'nts 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. conta, ins a generic request for aoditional infomation regarding duxiliary feedwater syster flow requirements.

The desiens and procedures of the subject facility should be evaluated against the applicable requirements specified in Enclosure 1 to determine the 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 should be provided for NRC staff review within thirty days of receipt of this letter. Also, this schedule should indicate your date for submittal of informatiun 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 addition to the requirements identified in this letter, other requirements which may be applicable to the subject 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 1087 001 7910080 8

l'r. Sol Burstein-September 21, 1979 Break Accidents for Westinghouse NSSS Systen;."

Our specific concerns include systens 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 ite'ns from the Bulletins and Orders Task Force review.

incerely, f

I$.E@isen' hut, ting Director re Division of Operating Reactors Office of Nuclear Reactor Regulation Enclosures :

As stated cc: w/ enclosure See next page 1087 002

Mr. Sol Burstein Wisconsin Electric Power Company cc: Mr. Bruce Churchill, Esquire Shaw, Pittman, Potts and Troworidge 1800 M Street, N.W.

Washington, D. C.

20036 Document Department University of Wisconsin Stevens Point Library Stevens Point, Wisconsin 54481 Mr. Glen Reed, Manager Nuclear Power Division Point Beach Nuclear Plant Wisconsin Electric Power Company 231 West Michigan Street Milwaukee, Wisconsin 43201 1087 003

ENCLOSURE 1 X.ll (W)

POINT BEACH 1 AND 2 AUXILIARY FEEDWATER SYSTEM (AFWS)

X.ll.1

System Description

X.ll.l.1 Configuration, Overall Design A simplified flow diagram of Point Beach I a..d 2 AFWS is shown in Figure 1.

The automatically initiated auxiliary feedwater (AFW) system for each Point Beach Unit is partially shared between units I cnd 2 to supply AFW to both steam generators of each unit.

Each AFW system uses a turbine drive pump and a motor driven pump.

The turbine driven pump of one unit feeds both steam generators of that unit only.

The motor driven pump of each unit feeds one steam generator in each unit and therefore is shared between units.

The turbine driven pumps supply AFW to the main feedwater piping inside containment through a motor operated valve for each steam generator of their respective units.

The motor operated valves (MOV 1A and 2A for Unit 1, MOV 1B and 2B for Unit 2 on Figure 1) are normally opened to a throttled posi m to supply design flow to each steam generator.

On loss of power these valves fail as-is.

Each of the two motor driven pumps supplies AFW to one steam generator of each unit through individual motor operated isolation valves which are normally open and fail as-is on loss of power.

(MOV 3A and 38 from one pump and MOV 4A and 48 from the ether pump).

A pressure control valve (PCV-1 for Unit 1, PCV-2 for Unit 2) at the discharge 1087 00h1

2 of each. pump controls flow to two steam generators ( one generator per unit) by maintaining a constant pressure at the pump discharge. The set point of this controlled pressure determines flow to the steam generators and can be varied by the control room operator.

The PCV's a,re air operated and fail open upon loss of air.

All four AFW pumps normally take suction from two non-seismic Category I conder. sate storage tanks (45,000 9:llons capacity each) through manually operated locked open isolation valves.

The condensate storage tanks are normally lined up in parallel to the common suction header of the AFW pumps.

The minimum total capacity of the condensate storag,e tanks (by Technical Specifications) is 10,000 gallons per operating unit.

The total capacity (20,000 gallons) will allow at least 25 minutes of supply with both' turbine drive AFW pumps running (400 gpm per turbine-driven pump) or 50 minutes supply with both motor-driven pumps running (200 gpm per motor driven pump).

The service water system serves as the seismic Category I source of water to the AFWS and is capable of unlimited supply.

The service water system (SWS) connects directly to the suction of each AFW pump down-stream of the suction check valves and is therefore unaffected by malfunctions in the condensate tank supply portion of the AFW system.

SWS supply is initiated in the control room by opening a motor operated valve in the SWS to each AFW pump suction.

The system is arranged such that a failure of either of the two diesel generators on site will not prevent water from being supplied to the AFW system for either unit.

1087 005

3 Since all valves in the flow ph.:. to the steam generators are normally open and fail as-is (with exception of PCV-1 and 2 which fail open) a loss of A-C or D-C power does not require v;-1ve manipulation. The motor operated steam valves at the inlet to the turbines (MS-1A and 2A for Unit 1, MS-1B and 28 for Unit 2) are 0-C motor operated valves and will automatically open in the event of a loss of all A-C power.

In the even't of an unisolable main steam or feedwater line break coincident with a worst case single active failure, operator action within the control room will isolate AFW flow to the af fected steam generator and assure flow to the unaffected steam generator. The

~

licensee estimates >;U minutes to boil dry.

A break anywhere in the auxiliary feedwater system discharge piping would not prevent automatic AFW flow to at least one steam generator on demand.

A single active failure coincident with a break could dis-able automatic AFW to both steam generators, depending on break location.

In either case, breaks could be isolated by operator action within the control room.

X.ll.l.2 Component Design Classification All pumps, valves, piping, instrumentation and controls associated with the auxiliary feedwater system (except Condensate Storage Tanks) are designed safety Class I wh;ch includes seismic Category I requirements.

1087 006

4 The condensate storage tank and associated instrumentation are not designed to safety grade requirements.

The piping from the tank to the auxiliary feedwr.ter system is classified as safety class I which includes se,ismic Category 1 requirements.

e X.ll.1.3 Power Sources Power sources for all instrumentation and coat-n'- are taken from the emergency buses wh1ch are supplied by the safety

• elated diesel generators or safety related station batteries.

Steam generator water level control and the automatic initiation system are designed as a safety related system, including seismic Category I.

Each motor driven pump and associated instrumentation and controls are powered by a separate diesel-generator, such that a failure of one diesel generator will only disable one motor driven train.

The turbine driven pump for each unit receives steam from both steam generators of its respective unit through parallel d-c motor operated isolation valves.

The parallel valves are powered from separate D-C buses such that a loss of one d-c system will not prevent operation of either turbine driven pump.

X.11.1.4 Instrumentation and Controls X.11.1.4.1 Controls All controls for the active components of the auxiliary feedwater system can be operated from the control room.

Normally steam generator 1087 007

5 level is controlled in the control room by adjusting the pressure set point of the pressure control valves at the discharge of each motor driven pump.

If it is necessary to control turbine pump flow for level contr,ol, the motor operated valves in the discharge lines from the turbine driven pump each steam generator can be throttled from the control room.

Each concrol actuator in the control room is located in a basic system layout (MIMIC Bus) to help identify the control switch function in addition to the identifying name plate.

X.11.1.4.2 Information Available to the Operator I.

Alarms a)

H'./Lo Steam Generator Level b)

Low Level - Condensate Storage Tank c)

Service Water System Header Pressure Low II.

Ira cation a)

Steam Generator Level b)

Condensate Storage Tank Level c)

AFW pump dischargt pressure d)

Service Water Header pressure e)

Valve Position Indication - All Active Valves f)

Pump Running Lights - Motor Drive g)

Pump Breaker Trouble Light - (Did Not Close on Demand) h)

Pressure Set Point - Pressure Control Valve 1087 008

6 All valve position indicators are located with their respective centrols on the " MIMIC Board" such that the valves are readily identified.

X.ll.l.4.3 AFW Initiatina Signals I.

Turbine Pumps a)

Lo-Lo Level in both S/G's of its respective unit - automatic b)

Loss of both 4 KV busses (Supply reactor coolant Pumps) -

automatic c)

Manual - From Control Room II.

Motor Driven Pumps a)

Lo-Lo Level in any one S/G of either unit - automatic b)

Trip of both Main Feed Pump - either unit - automatic c)

Safety Injection Signal - either unit automatic d)

Manual - from Control Room X.11.1.5 Testing 1)

Valve position is verified monthly 2)

Service Water System supply valves are cycled monthly 3)

Operational tests of AFW pumps are performed monthly by verifying pump suction and discharge pressure (Tests are staggered) 4)

Flow verification tests from condensate tanks to S/G's are performed at each refueling or whenever in cold shutdown (Not more frequently than quarterly) 1087 009

7 5)

Automatic initiation of the AFW system is verified during each refueling.

6)

Control and initiating circuits are tested with each pump and valve test 7)

Following maintenance on the system,an operational test is performed to bring the system back in ser.-ice.

X.ll.1.6 Technical Specifications A.

When the reactor coolant is heated above 350 F the reactor shall not be taken critical unless the following conditions are met:

la.

Two Unit Operation - Three of the four auxiliary feedwater pumps are operable.

lb.

Single Unit Operation - Either the turbine driven pump associated with that unit together with one of the two

' motor driven pumps or both motor driven pumps must be operable.

E.

A minimum of 10,000 gallons of water per operating unit in the condensate storage tanks and an unlimited water supply from the lake via either leg of the plant service water system.

3.

System piping and valves required to function during accident conditions directly associated wi'h the above components must be operable.

B.

During power operation, the requirements are modified to allow the following components to be inoperable for a specified time.

1087 010

8 If the system is not restored to meet the above requirements within the time period specified the appropriate reactor (s) shall be placed in the hot shutdown condition.

If they are not satisfied within an additional 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, the appropriate reactor (s) shall be cooled down to less than 350*F.

1.

Two Unit Operation - One of the threc operable auxiliary feedwater pumps may be out-of-service provided a pu.np is restored to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

2.

Single Unit Operation - One of the two 1perable auxiliary feedwater pumps may be out-of-service provided a pump is restored to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

X.11.2 Reliability Evaluation X.ll.2.;

Dominant Failure Modes The dominant failure modes are expressed for three transient situations and two operational configurations. single unit operation and double unit operation.

Limiting conditions for single unit operation are a single motor-driven pump and associated turbine driven pump operable or both motor driven pumps operable.

Any ane can be out of service for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

Limiting conditions for double unit operation are three of four auxiliary feedwater pumps operable.

Any one can be out of service for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

1087 011

11 LOFW with Only DC Power Available Single Unit Operation The dominant failure contributor is loss of both motor-driven pumps and subsequent fail >~9 of the turbine driven pump due to loss of service water (AC) cooling to steam turbine pump bearing oil.

Double Unit Operation Same failure as single unit operation.

X. l l. 2. 2 Interdependencies The principal noted dependency is the design for AC cooling of the turbine driven put;s.

X.11.3 Recommendations for this Plant The short-term recoma,endations (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 operatcr failures. The long-term (both generic, denoted by GL, and plant-specific) recommandations identified in this sec-tion involve system de;ign evaluat.

' and/or modifications to improve AFW system reliability and repr sent actions that sht.uld be implemented by January 1, 1951, or as soon thereafter as is practicable.

1087 012

~ ^

12 X.11.3.1 Short-Term 1.

Recommendation GS The licensee should propose modifications to the Technical Specifications to limit the time that one AFW system pump aqd its associated flow train angi essential instrumention can be inoperable. The outage time limit and subsequent actior, time should be as required in current Stancare Technical Specifications; i.e., 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, respectively.

2.

Recommendation GS The licensee should lou open single valves cr multiple valves in series in the AFW system pump suction piping and lock open other single valves or multiple w ives in series at could interrupt all AFW flow. Monthly inspections should be performed to verify that these valves are locked and i*n the open position.

These inspections should be proposed for incorporation into the surveillance requirements of the plant Technical Specifications. See Recor endation GL-2 for the longer-term resolution of tt.is concern.

4 Recomendation GS Emergency procedures for transferring to alternate sources of AFW supply should be available to th.e plant operators. These procedures should include criteria to inform the operator when, and in what crder, the transfer to alternate water sources should take place. The following cases should be covered by the procedures:

1087 013

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

a vail able. The procedures for '.his case should include any operator actions required to protect the AFW sy; tem pumps

, against self-damage before water flow is initiated; and, e The case in wh:c: che primary water supply is being depleted.

The procedure for this case shouH 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-viding the required AFW flow for at least two hours from one AFW pump

.f 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 established for manually initiating and controlling the system under these conditions: Since the water for cooling of the lobe oil for the turbine-driven pump bearings may be dependent on alter-natirg current power, design or procedural changes shall be made to eliminate this dependency as soon as practicable. Until this is done, the emergency procedures shculd provide for an individual to be stationed at the turbine-driven pump in the event of the loss of all alternating current power to monitor pump bearing and/or lube oil temperatures.

If necessary, this operator would operate the 1087 014

14 turbine-driven pump in an on-off mode until alternating current p3wer is restored. Adequate lighting powered by direct current power sources and communications at local stations should also be provided if manual initiation and con'rol of the AFW system is needed.

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

5.

Recommendation GS The licensee should confirm flow path avail-ability of an AFW system flow train that has been out of s ice to perform periodic testi a 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 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 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.

6.

Recommendation CS The licensee should verify that the automatic start AFW system signals and associated circuitry are safety-grade.

If this cannot be ve ified, the AFW system automatic initiation system shot,'

be modified in the short-term to meet the functional rer. cements 11.ted 1087 015

15 below. For the longer term, the automatic initiation signals and circuit should be upgraded to meet safety-grade 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 ar: circuits should be designed so that a single failure will not result in the loss of auxiliary feedvater system function.

Testability of the initiation signals and circuits shall be be a feature of the design.

The ini.tiation signals and circuits should be powered from the emergency buses.

Manual capability 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.

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 failure will not result in the loss of manual capability to intiate the AFW system from the control room.

1087 016

16

.11.3.2 Additional Short-Term Recommendations The following additional short-term recommendations resulted from the staff's lessons Learned Task Force review and the Eu.letins 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 operating plants. They have not been eaamined for specific applicabily to this facility.

1.

Recommendation - The

censee should provide redundant level indications and low level 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 an alternate water supply and prevent a low pump suction pressure condition from occurr.ing.

The low level alarm setpoint should allow at least 20 minutes for operator actions, assuming that the largest capacif / 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 ope ation has not been accomplished to date.

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

Test acceptance criteria should include demonstrating that the pumps remaia within design limits with respect to bearing / bearing oil tempera-tures and vibration and that pump room ambient conditions 1087 017

17 (temperature, humidity) do not exceed envircomental 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:

"Sa. ty-grade indication of auxil.ary 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 req trements for the auxiliary

.feedwater system set forth in Au>;iliary Systems Branch Techn-nical Position 10-1 of the Standard Review Plan, Section 10.4.9."

Recommendation - Licensees with plants which require local manual 4.

realignment of valves to conduct periodic tests on one AF8 system train and which have only one remaining AFW train available for operation, should propose Technical Specifications to provide that a dedicated individual who is in communication with the control room be stationed at the manual valves.

Upon instruction from the contro',

room, this operator woulo re-align the valves in the AFW system.trai-from the test mode to its operational aligr. ment.

1087 018

18 X.11.3.3 Long-Term Long-term recomnendations for improving the system are as follows:

1.

Recommendation GL At least one AFW system pump and its associated flow path and essential instrumentation should auto-matically initiate AFW system flow and be capable of being operated independently of any alternating current ower source for at least two hours. Conversion of direct curren power to alternating current is acceptable.

2.

Recommendation - GL Licensees having plants with unprotected normal AFW system water supplies should evaluate the design of their AFW systems to determine if automatic protection of the pumps is necessary following a seismic event or a tornado.

The time available before pump damage, the alarms and indications available to the control room operator, and the time necessary for assessing the problem and taking action should be corsidered in determining whether operator action can be relied on to prevent pump damage.

Consideration should be given to providing pump protection by means such as automatic switchover of the pump suctions to the alternate safety grade source of water, automatic pump trips on low suction pressure or upgrading the normal source of watar to meet seismic Category I and tornado protection requirements.

3.

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

1087 019

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1087 020 0

,g Basis for Au,aliary Feestater System Flou Recuirements As a result of recent staff revie<:s of operatin; piant Auxiliary Feed-water Systcms (AFWS), the staff concludes that the design bases and criteria prcvided by licensees for establishina AFWS requirements for flow to the steam generator (s) to assure adequate removal of reactor decay heat are not well defined or documented.

We recuire that you prcvide the following AFWS fic design basis infor-mation as applicable to the design basis transie ts and accident con-ditior.s for your plant.

Identify the plant transient and accident conditions considere) 1.

a.

in establishing AFWS flow requirements, including the following events:

1) Loss of Main Feed (Lf1FW) 2)

LMFW w/ loss of offsite AC power

3) LMFW w/ loss of onsite and offsite AC power 4)

Plant cooldown

5) Turbine trip with and without bypass

6) Main steam isolation valve closure

7) Main feed line break

8) Main steam line breck

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 t

limits such as:

- M;ximum RCS pressure (PORY or safety valve actuation)

- Fuel temperature or damage.licits (DfG, PCT, maximum fuel central temperature)

- RCS cooling rate limit to avoid excessive coolant shrinkage

- flinimum 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 cor: e:ponding teJhnical 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 or accidcat.

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.

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

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

1087 022

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

and against which the AFW pump mu!.t develop sufficient head.

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

e.g.1 out of 2?, 2 out of 4?

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 maintain m'inimum steam generator water level.

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

Volume and maximum tenperature of water in main feed lines k.

between steam generatcr(s) and AFWS connection to main feed line.

Operating condition nf steam generator normal blowdown following 1.

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.

1087 023

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 rr.argin in sizing the pu.; f'.ow to allow for pump recirculation flow, seal leakage and pump wear.

1087 024

.