ML19256E057
| ML19256E057 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 10/03/1979 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | Goodwin C PORTLAND GENERAL ELECTRIC CO. |
| References | |
| NUDOCS 7910250578 | |
| Download: ML19256E057 (22) | |
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UNITED STATES i
NUCLEAR REGULATORY COMMISSION
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,S WASHING TON, D. C. 20555 L
%..w. p 3M Cocket No.: 50-344 Mr. Charles Goodwin Assistant Vice President Portland General Electric Company 121 S. W. Salmon Street Portland, Oregon 97204
Dear Mr. Goodwin:
SUBJECT:
NRC REQUIREMENTS FOR AUXILIARY FEEDWATER SYSTEMS AT TROJAN NUCLEAR PLANT 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.
Enclosure I to te is letter identifies each of the requirements applicable tc the subject facility. These requir3ments 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 generic request for additional information regarding auxiliary feedwater system flow requirements.
The designs and procedures of the subject facility should be evaluated against the applicable requirements specified in Enclosure 1 to detemine the degree to which the facility currently confoms to these requirements. The results of this evaluation and an associated schedule and cormiitment for implementation of required changes or actions should be provided for tRC 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 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 Bulle. ins and Orders Task Fcrce. Such requirements are those resulting from cur review of the loss-of-feedwater event and the small break loss-of-coolant accicent as cescribed in the Westinghcuse report WCAP-9600, " Report on Small P00RBR(in um m sv g
=
. r. Charles Goodwin OCT 3 1979 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 from the Bulletins and Orders Task Force review.
S Sincerely, rg6, g ga' dor ei
. Ei s nfidt, ncting' Di rector va Division of Operating Reactors Office of Nuclear Reactor Regulation Enclosures.
As stated 100RORBNA 1210 946
Mr. Charles Goodwin, Jr.
Portland General Electric Company cc:
Mr. H. H. Phillips Robert M. Hunt, Chairman Portland General Electric Company Board of County Commissioners 121 S.W. Salmon Street Columbia County Portland, Oregon 97204 St. Helens, Oregon 97051 Warren Hastings, Esquire Counsel for Portland General Electric Company 121 S.W.
'imon Street Portlano, Oregon 97204 Mr. Jack W. Lentsch, Manager Generation Licensing and Analysis Portland General Electric Company 121 S.W. Salmon Street Portland, Oregon 97204 Columbia County Courthouse Law Library, Circuit Court Room St. Helens, Oregon 97501 Director, Oregon Department of Energy Labor and Industries Building, Room 111 Salem, Oregon 97310 Richard M. Sandvik, Esquire Counsel for Oregon Energy Facility Siting Counsel and Oregon Department of Energy 500 Pacific Building 520 S.W. Yamhill Portland, Oregon 97204 Michael Malmrose U. S. Nuclear Regulatory Commission Trojan Nuclear Plant P. O. Box 0 Rainier, Oregon 97048 Mr. Donald W. Godard, Supervisor Siting and Regulation Oregon Department of Energy Labor and Industries Building, Rocm 111 Salem, Oregon 97310 1210 047
ENCLOSURE 1 X.15 (W)
TROJAN AUXILIARY FEEDWATER (AFW) SYSTEM X.15.1
System Description
X.15.1.1 Confiauration, Overall Design The Auxiliary Feedwater (AFW) system for Trojan uses two full capacity pumps (1 turbine driven, 1 diesel driven - 880 gpm per pump) to feed four steam generators.
A simplified flow diagram of the Trojan AFW is shown in Figure 1.
The licensee is currently planning installation of a third motor driven pump (non-safety grade) for startup and shutdown.
Each' of the two installed pumps takes suction from a non-safety grade condensate storage tank through manually locked open valves via a common suction header.
The seismic Category I classification of the AFW system stops at the check valve in each pump's suction line.
A long term seismic Category I supply of water from the service water system (SWS) connects to the piping between the check valves and the pumps via normally closed motor operated isolation valves.
These valves can be opened or closed from the control room.
Each pump feeds all four steam generators through a discharge line wnich branches into four lines to supply the four steam generators.
Each pump discharge line is proviced with a check valve and an isolation valve to permit maintenance of the pumo and the check 10 94g
2 valve.
The discharge line then branches into four lines to supply the four steam generators.
Each of these four lines is provided with a motor-operated control valve, a check valve downstream, and manually-operated isolation valves upstream and downstream of the control valve.
Each of these four auxiliary feedwater lines joins with a ccrresponding line from the second pump into a single line in which a flow indicator is provided for remote and local indication.
Also, flow restrictors are located upstream of each motor-operated control valve in each of the two supply lines to each steam generator.
In the event of a pipe break downstream of the MOV, a high-flow signal from a flow element at one of these restrictors will automatically close the motor-operated valve associated with the orifice.
The single auxiliary feed line then joins with the steam. generator main feedwater line in the Seismic Category I section between the feedwater line isolation check valve and the containment.
The system is designed to automatically start both AFW pumps upon receipt of initiating signals.
All valves in the system flowpath are normally open and fail as-is.
The steam turbine driven pump (880 gpm to the S/G's) is auto / manual started by opening motor operated isolation valves from the steam lines of all four steam generators and by opening the turoine trip throttle valve in the common heacer down-stream of the four inlet valves.
Service water to cool the lube oil of the turoine driven pump is automatically initiated by opening of a 1210 949
3 MOV from the service water system whenever the turbine pump gets a signal to start.
The licensee is presently revising this design such that the lube oil will be cooled by the discharge of the turbine driven pump.
The diesel driven pump has its own starting battery which auto-matically starts the diesel.
The initiating signals also start a reduction gear lube oil priming pump, and open an MOV to supply service water for jacket cooling and lube oil cooling.
The diesel has a day tank with a 500 gallon capacity good for 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> of diesel operation. ' Automatic transfer of oil to the day tank # rom the emergency diesel fuel oil transfer system is controlled by day tank level.
Both the diesel and turbine driven pumps use governors that control the speed to automatically maintain a set pressure differential between the pump discharge and the steam generators.
This pressure differential can be selected by the control room operator to help control steam generator level.
~5.1.2 Comoonents. Desian Classification The condensate storage tank and the piping frcm the condensate s+.orage tank to the check valve in each pump's suction line are non-safety grade (non-seismic).
The recirculation lines from the cump discharge to the condensate storage tank are also non-safety
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4 grace.
The pumps, piping, valves, and valve actuators for the rest of the AFW system are seismic Category I.
The controls, instrumentation and power supplies for the operation of the auxiliary feedwater system are seismic Category I, Class IE.
However, the actual indicators in the control room are not designed to meet seismic Cctegory I requirements.
The ventilation supply fans, diesel fuel oil and lube oil system, service water cooling supply and water source supply are designed to seismic Category I requirements.
X.15.1.3 Power Sources The turbine driven pump (train A) is associated with the train A electri' cal buses, including the train A ESF tiannels for automatic operation.
The diesel driven pump is supplied by train B in the same manner as the turbine driven pump.
Neither train is independent of AC power.
The steam inlet valves to tP.e turbine driven pump are operated frcm the train A vital 480 volt aC cus.
Manual operation of these valves is required to cpen these MCV's upon loss of the train A vital bus,since they fail as-is and are normally closed.
These valves are normally closed to protect
}2.kb
5 against the effects of a steam line creak in the supply line downstream of these valves.
The diesel driven pump may start and operate withcut AC power but due to lack of cooling water to the jacket and lube oil, and due to lack of ventilation, operation of the diesel coulc not be sustained.
The licensee estimates that this diesel will trip on over-temperature in 5-10 minutes.
The vital DC buses are used to supply cortrol power to the speed governors for both pumps and for operation of the turbine trip throttle valve to the turbine driven pump.
X.15.1.4 Instrumentation and Controls X.15.1.4.1 Controis All controls for normal operation for the AFW system are Class 1E and operated from the control room.
These include steam inlet valves, the trip throttle, the steam control valve in the steam line to the turbine, ti.e AFW flow control valves (2 to each S/G), and pump start and stop.
Steam Generator level is cor. trolled from the control room by con-trolling pump speed and opening /cicsing of the AFW flow control valves to the steam generator.
Steam generater level transmitters 1210 052
=
6 and instrumentation circuits are safety grade Dut the level indicators on the control panel are not.
X.15.1.4.2 Information Available to the Operator I.
Alarms i.
Hi/Lo Steam Ger.erator Level 2.
Lo Condensate Storage Tank Level 3.
Low AFW Pump Suction Press-each pump 4.
Local-Control Override for each pump 5.
Hi Conductivity AFW II.
Indication 1.
Steam Generator Level 2.
Condensate Storage Tank Level 3.
Valve Position Indication for all MOV's, including SWS 4.
Steam Pressure at Turbine 5.
Suction Press each pump 6.
Discharge Press each pump 7.
Auto / Man Light for Pump Control 8.
AFW Flow to each Generator (not for,ach pump) 9.
Differential Pressure - Pump discharge and steam generator
.i.l.3 Initia:i c Signals for Auto Coeration Soth P'm:s 1.
Safety Injection Signal 2.
Lo-Lo Level in any steam generator (2 out of j 2 j O I)b3 3 detectors)
7 3.
Loss of Both main Feed Pumps 4.
Less of Offsite Power - Sensed on Vital Bus t15.'.5 Testirq Pumps and motor operated valves are tested monthly.
All the MOV's, including the service water system supply isclation valves,are cycled during their monthly test.
The pumps are tested by closing the flow control valve for the pump, starting the pump, and checking pressure and recirculation flow.
All testing is done from the control room.
Every 18 months,a flow verification test from the condensate storage tank to the steam generators is performed.
Also every 18 months, automatic start of the AFW pumps from the auto-start logic is tested.
Every 18 months,a routine instrumentation and controls calibration check is performed.
X.15.1. 6 Technical Soecifications I-At least two independent steam generator auxiliary feedwate pumps and associated flow paths shall be operable with:
a.
One feedwater pump capable of being powered by an operable diesel with >450 gallons of fuel in its day tank, and One feed ater pumo capable of being cowered from an operacle steam supply.
1210 054
8 2.
With one AFW pump inoperable, restore the inoperable pump 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 the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
X.15.2 Reliability Evaluation X.15.2.1 Dominant Failure Modes LOFW with Offsite Power Available The dominant failure contributors include a combination of human errors associated with the two water sources (manual valve left closed and failure to take corrective actions).
Other dominant contributors are combinations of hardware failures associated with each pump train, test and maintenance outages, and a human error resulting in manual valves left closed in the pump discharge lines, undetected by control room indication or by pump test indications.
LOFW with Loss of Offsite Power with Onsite AC Power Available The dominant failure contributors are the same as for the non-LOP transient with the addition of a single emergency AC train failure in combination with other failures in the other pump train.
LOCW with Loss of All AC. DC Available Under present cesign, assuming completion of the modification to provide bearing cooling water from the AFW turcine pumo line, the dominant failure contributors are single failures. They include tne human failure to cpen a condensate storage tank manual valve, the hardware, test and maintenance and human error contributors associated 1210 055
9 with the turbine train human failure to open the AC steam inlet MGV's by hanc and AC power dependence for cooling the diesel driven pump.
4.15.2.2 Interdependencies The principal noted dependenc, as the design for AC cooling of the diesel driven pump and for operation of the tarbine steam inlet valves.
X.15.3 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 relia *ility that should be implemented by January 1, 1980, or as
]
soon thereafter as is practicable.
In general, they involve upgrading of Technical Specifications cr establishing procedures to avoid or mitigate potential system or operator failures. The long-term (both generic, 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,.931, or as soon thereafter as is practicable.
.15.3.1 Short Term 1.
Reco rendation GS The licensee should lcck open single valves er multiple valves in series in the AFW system pump suction piping and lock ocen ether single valves or multiple va ses in series that could interrupt all AFW ficw. Monthly inspe ions should be performed to verify that these valves are locked and in the open position.
12't0 056
10 These inspections should be proposed for incorporation into the surveillance requirements of the plant Technical Specifications. See Recommendation GL-2 for the longer-term resolution of this concern.
2.
Recommendation GS Emergency procedures for transferring to alternate sources of AFW supply should be available to the plant operators.
These procedures should include criteria to inform the operators 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 avail;ble.
The procedures for this case should include any operator actions required to protect the AFW system pumps against self-damage before water flow is initiated; and, The case in which the primary water supply is being depleted.
The procedure for this case should provide for transfer to the alternate water sources prior to draining of the primary water supply.
3.
Recommendation GS The as-built plant should be capable of providing the required AFW flow for at least two hours from one AFW pumo train indeoendent of any alternating current power source.
If manual AFW system initiation or flow control is requirec following a complete loss of alternating current ocwer, emergency procecures should be establisned for manually initiating anc controlling
'e system under these ccaditions.
1210 057
=
11 Since the water for cooling of the lube oil for the turbine-driven pump bearing may be dependent on alternating current power, design or procedural changes shall be made to eliminate this dependency as soon as practicable.
Until this is done, the emergency precedures should 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 and, if necessary, this operator would operate the turbine-driven pump in an on-off mode until alternating current power is restored.
Adequate lighting
- powered Dy 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.)
4.
Recommendation GS The licensee should confirm flow path availability of an AFW system flow train that has been out of service to perform periodic testing or maintenance as follows:
Proceduresshould 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.
The licensee should croDose Technical $;ecifications to assu e that prior to clant startup folicwing an extended co'0 shutdown, a flow test aculd be performed to verify the normal flow path from the primary AFW system water source to the steam generators.
The flow test should be conductec
- it" AFW syste valves in their normal alignment.
1210 958
12 5.
Recommendation GS The licensee should verify that the automatic start AFW 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 Recommendation G L-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 shall 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 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-driver pum:s and valves in the auxiliary feedwater system shoulc be included in the automatic actuation (simultaneous and/or secuential) of the loads to the emergency buses.
1210 059
13 The automatic 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.
X.15.3.2 Additional Short-Term Recommendations The following additional short-term recommendations resulted from the staff's Lessons Learned Task Force 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 operating plants.
They have not been examined for specific applicability to this facility.
1.
Recommendation - The licensee should provide redundant level indications and 15w level alarms in the control room for the AFW system primary water supply to allow the operator to antici-pate 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 cumos, if such a test or continucus period of operation has not been accomplishec to date.
Following the 72-hour pump run, the pumps should ce shut down anc cooled cown and then restarted and run for one hour.
Test k.\\ N
14 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 Branch Techn-nical Position 10-1 of the Standard Review Plan, Section 10.4.9."
4.
Recommendation - Licensees with plants which require local manual realignment of valves to conduct periodic tests on one AFE 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 instructicn from the control room, this operator would re-align the valves in the AFW system train from the test mode to its operational alignment.\\0
15 .'0.3.3 Lonc Term Long-term recommendations for improving the system are as follows: 1. Recommendation - GL Licensees with plants in which all (primary and alternate) water supplies to the AFW systems pass through valves in a single flow path should install redundant parallel flow paths (piping and valves). Licensees with plants in which the primary AFW system water supply passes through valves in a single flow path, but the alternate AFW system water supplits connect to the AFW system pump suction piping downstream of the above valve (s) should install redundant valves parallel to the above valve (s) or provide automatic opening of the valve (s) from the alternate water supply upon low pump suction pressure. The licensee should propose Technical Specifications to incorporate appropriate periodic inspections to verify the valve positions. 2. 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 power source ' c at least two hours. Con.ersion of direct current ;ower to alternati g current is accettacle. 3. Recer endation - GL Licensees hacing clants with u.9 protected normal AFW system water supplies shouic e'aluate the cesign of 1210 062
a 16 their AFW systems to determine if autcmatic protection of the pump is necessary following a seismic event or a ternaco. The time available before pump damage, the alarms and indications available for the control room operator, and the time necessary for assessing the problem and taking action should be considered 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 water to meet seismic Category I and tornado protection requirements. 4. Recommendation - GL The licensee should upgrade the AFW system automatic initiation signals and circuits to meet safety grade requirements. 5. Recommendation - A motor driven pump is currently being installed or is planned to be installed by the licensee. Present plans are for a non-safety grade motor driven pump system. Based on past experience of the problems associated with the speed control (overspeed trips) of both the diesel and turbine driven pumps and other Licensee Esent Recorts cn the Trojan AFW system, the licensee shoulc further rev'ew ine orcpcsea installat'on to determine if the cter cr'ven cump snould be safety grade and autcmatically actuated :y t.me AFW autcmatic start logic. 1210 063
17 6. Recommendation - A pipe break in certaia locaticns of the turbine driven auxiliary feedwater pump discharge piping ray af fect both AFW trains,since portions of this piping pass thrcugn the diesel driven pump room. The motor driven pump to be installed should be located such that a break in the AFW system (nct associated with the motor driven pump train) could not affect the motor drive pump. Also the licensee should 1) install the motor pump with appropriate valves in the pump discharge line connections to meet the high energy line break criteria in SRP 10.4.9 and Branch Technical Position 10-1; namely, the AFWS should maintain the capability to supply the required AFW flow to the steam generator (s) assuming a pipe break anywhere in the AFW pump discharge lines plus a single active failure 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. O
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cmum Sasis for Auxiliary F eedwater System Flow Recui rerents As a result of recent staff reviews of operating piir.: Auxiliary Feed-water Systems (AFWS), the staff concludes that tne desi;n bases and criteria provided by licensees for establishing AFW5 re;uirements for flow to the steam generator (s) to assure adequate removal cf reactor decay heat are nat well defined or docurented. We recuire that you provide the following AFWS flow design basis infor-Tation 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 ficw requirements, including the following events:
- 1) Loss of Main Feed (LMFJ)
- 2) LMFW w/ loss of offsite AC power
- 3) LMFW w/ loss of onsite and offsite AC pcwer
- 4) Plant cooldown
- 5) Turbine trip with and without bypass Main steam isolation valve closure 6).
- 7) Main feed line break
- 8) Main steam line break
- 9) Small break LOCA 10)
Other transient or accident conditions n t liste.d above b. Describe the :: Tant protection acceptance crite-ia ar.d c:rres-pending technical bases used for ea.h initia ir; event identi-fied above. The acceptan:e criteria should address plant limits such as: 1210 066
- Maxi ;- RCS pressure (PORY or safety valve actuation) - Fuel temoerature or damage limits (DNE, PCT, maximum fuel cer.:ral te.perature) - RCS cooling rate limit to avoid excessive coolant shrinkace - Minimum steam generator level to assure sufficient steam generator heat transfer surface to remove decay heat and/or cool do'wn the primary system. 2. Describe the analyses and assumptions end 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 or 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 AFk'3 flow into steam generator (s). d. Minimum steam generator water level when initit ting event occurs. Initial steam generator water inventory and depletion rate before e. and a'ter AFWS flow commences - identify reactor de:ay heat ra:e used. 1<>10 007 2n Maximum pressure at which steam is released i'ro. steam ger.erator(s) f. and acainst which the AFJ pump must develop suf ficient her.d. Minimum number of steam generaters that must receive APJ flow; g. e.g. 1 out of 2?, 2 out of 4? RC flow condition - continued operation of RC pumps or natural .h. circulation.
- i. Maximum AFJ inlet temperature.
Fc110 wing a postulated steam or feed line break, time delay j. assumed to isolate break and direct AFn' flow to intact steam generator (s). AFJ pump fica capacity allowance to accomodate t'le time dclay and maintain minimum steam generator water level. Also identif: credit taken for primary system heat removal due to blowdown. Volume and maximum temperature of water in main feed lines k. between steam generator (s) and AFWS connectica to main feed line. Operating condition of steam generator nomal blowdown following 1. initiating event. Primary and secondary system water and metal sensible heat m. used for cooldown and APJ flow sizing. Time at het standby and time to cooldown RCS to R= system cut n. in tegerature to si:e AFW water source inventory. 1210 068
_4 3. Verify that the A punps in your plant will supply the necessary fic i to the steam generator (s) as detemined by items 1 and 2 above considering a sincie failure. Identify the margin in sizina the pump flow to allow for pump recirculation flow, seal leakage and pump wear. 1210 069}}