ML19256F157
| ML19256F157 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 11/06/1979 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | Cavanaugh W ARKANSAS POWER & LIGHT CO. |
| References | |
| NUDOCS 7911210552 | |
| Download: ML19256F157 (20) | |
Text
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-- ~ e;p e November 6, 1979 Docket No. 50-368 Mr. William Cavanaugh, III Executive Director of Generation and Construction Arkansas Power & Light Company P. O. Box 551 Little Rock, Arkansas 72203
Dear Mr. Cavanaugh:
SUBJECT:
NRC REQUIREMENTS FOR AUXILIARY FEEDWATER SYSTEMS AT ARKANSAS NUCLEAR ONE UNIT 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 lignt 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 Combustion Engineering-designed operating plants, and (2) plant-specific requirements applicable only to the subject facility. Enclosure 2 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 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 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 ar:e 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 ace-ident as described in the Cont)ustion Engineering report CEN-ll4-P (Amendment 1-P) l3//
?80 7 911210 SSC
c :- ~c:-dijisiiiisite-
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7.;;;C Mr. William Cavanaugh, III.
entitled, " Review of Small Break Transients in Combustion Engineering Nuclear Steam Supply Systems." 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 frm the Bulletins and Orders Task Force review.
- ncerely, i
Darrel G. E s n ut, cti g Director Division of Operating Reactors Office of Nuclear Reactor Regulation
Enclosures:
As stated cc w/ enclosures:
See next page e
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Arkansas Power & Light Coupany
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Cc:
r-Phillip K. Lyon, Esq.
House, Holms & Jewell 1550 Tower Building Little Rock, Arkansas 72201 Mr. David C. irimble Manager, Licensing Arkansas Power & Light Company P. O. Box 551 Little Rock, Arkansas 72203 Mr. James P. O'Hanlon General Manager Arkansas Nuclear One P. O. Box 608 Russellville, Arkansas 72801 Mr. William Johnson U. S. Nuclear Regulatory Commission P. O. Box 2090 Russellville, Arkansas 72801 Mr. Robert B. Borsum Babcock & Wilcox Nuclear Power Generation Division Suite 420, 7735 Old Georgetown Road Bethesda, Maryland 20014 Troy B. Conner, Jr., Esq.
Conner, Moore & Corber 1747 Pennsylvania Avenue, N.W.
Washington, D.C.
20006 Arkansas Polytechnic College
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Russellville, Arkansas 72801
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ENCLOSURE 1 X.1 (CE)
ARKANSAS 2 EMERGENCY FEEDWATER SYSTEM X.1.1
System Description
X.1.1.1 Configuration - Overall Design The emergency feedwater system (EFWS) as shown in Figure 1 consists of primary and seconcary sources of water and two emergency feedwater pumps, which feed either or both steam generators (SG). The primary source of EFM water is a non-seismi: Category I condensate storage tank with a 200,000 gallon capacity, 160,000 gallons of wnfcn are dedicated to the EFWS by the Technical Specifications.
There is also available 100,000 gallons of water from a swing condensate storage tank which is shared by both Unit 2 and Unit 1.
The secondary source of water is the plant service water system, a seismic Category I system, whose water source is either the emergency cooling pond o,' the Dardanell Reservoir.
The service water system is seismic Category I up to and including the suction piping from the emergency cooling pond (the ultimate heat sink).
Three service water pumps can draw water from the reservoir (normal mode) or from the emergency cooling pond.
The reservoir can also'act as a long term water source.
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. The primary condensate storage tank is normally lined up to supply water to both EFW pumps through manually operated locked open isolation valves.
Train A incl _udes the motor-driven pump and Train B includes the turbine-driven pump, each having 100% capacity, and designed to deliver 575 gpm @ 1390 psig.
The discharge lines from each pump are cross-connected through two normally closed (NC) manual isolation valves.
Upon low suction pressure to the operating pump (s), the suction to the pump is automatically aligned to the secondary water source.
Under the worst transient conditions the licensee estimates that, without the EFW flow,the SG would boil dry in 14 minutes,following loss of main feedwater with reactor trip.
X.1.1.2 Comoonents Except for the condensate storage tanks, the EFWS components (pumps, valves, and valve operators) and piping are safety grade, seismic Category I and tornado missile protected.
The power supplies and instrumentation are Class lE.
Each EFW pump is located in a separate room.
Because the pumps are located below the probable maximum flood level, these rooms are watertight with watertight doors to prevent flooding.
There are two room coolers in the steam-driven pump room and one room cooler in the motor-driven pump room.
The lubricating system for each EFW pump is air-cocled by vanes on its pump shaft.
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_ X.1.1.3 Power Sources Except for the turbine pump steam admission valves immediately down-stream of steam gener_ators A and B, respectively, Train B of the. system (turbine-driven pump) obtains contrelpower and power for operating valves from the Division II bus, a Class lE DC source.
The turbine pump stdam admission valves receive power from Division I add II Class lE AC sources, respectively..4cwever, they are locked open with power removed during operation.
Train A (motor-driven pump) is powered by the Division I bus, a Class IE AC source.
Except for the two ball valves used to isolate the steam generators which are DC powe md, all the valves in Train A are AC powemd.
The onsite emergency power system consists of two divisions, each being supplied by an independent diesel generator and corresponding DC battery system.
Both the diesel generators and battery systems ?re located in separate seismic Category I rooms.
X.1.1.4 Instrumentation and Controls X.1.4.1 Controls Steam generator level is controlled automatically by the engineered safety features actuation system (ESFAS) and can be controlled manually from the control room.
Steam generator level indication and alarm are available to the operator in the control room.
EFWS flow to the steam generator is automatically terminated when the level reaches a high point, and low steam generator level will auto-matically reestablish emergency feedwater flow.
This on-off type of i3//
?85 flow control is accomplished by opening or closing the ball valves located at the inlet to the steam generators.
X.1.1.4.2 Information Available to Goerator System information available to the operator in the control room to assess the performance of the emergency feedwater system is as follows:
Position indicating lights for each electrical and pneumatic operated valve.
Steam generator level Steam generator pressure EFWS flow indication in each of the four water paths to the steam generators.
X.l.l.4.3 Initiating Signals for Automatic Ooeration The EFW pumps and flow path control valves are automatically actuated by the ESFAS whenever any of the followino two out of four coincident logic conditions exist:
1.
Steam generator (A & B) low level 2.
Steam generator (A & B) low pressure 3.
Steam generator differential pressure-high (SG-A>SG-B) 4.
Steam generator differential pressure-high (SG-B>SG-A) i3//
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_ Main steam line break isolation is accomplished automatically whereas
'a nain feedwater line break is manually isolated.
If steam generator isolation is required, as in the case of a postulated main steam line or feedwater line break, the ESFAS will open only the EFW valves leading to the intact steam generator.
A combination of measured variables (level and pressure) for each steam generator are used to determine which steam generator is intact.
X.l.l.5 Testing and Technical Specifications X.1.1.6 The EFWS is per'odically tested and has Limiting Conditions of Operation in accordance with the Technical Specifications as follows:
EMERGENCY FEEDWATER SYSTEM Two emergency feedwater pumps and associated flow paths shall be OPERABLE with:
a.
One motor driven pump capable of being powered from an OPERABLE emergency bus, and b.
One turbine driven pump capable of being powered from an OPERABLE steam supply system.
APPLICAB!LITY:
MODES 1, 2 and 3.
ACTION:
With one emergency feedwater 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 />.
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)g7 SURVEILLANCE REQUIREMENTS Each emergency feedwater pump shall be demonstrated OPERABLE:
a.
At least once per 31 days by:
1.
Verifying that the turbine driven pump develops a discharge pressure of 11200 psig at a flow of 1560 gpm when the secondary steam supply pressure in greater than 865 psig and the pump speed is <3600 rpm.
The provisions of Specification 4.0.4 are not applicable.
2.
Verifying that each valve (manual, power operated or automatic) in the flow path that is not locked, sealed, or otherwise secured in position, is in its correct position.
b.
At least once per 18 months during shutdown by:
1.
Verifying that each automatic valve in the flow path actuates to its correct position on MSIS or ESFAS test signals.
2.
Verifying that the motor driven pump starts automatically upon receipt of an ESFAS test siqnal.
3.
Verifying that the turbine driven pump steam supply MOV opens automatically upon receipt of an ESFAS test signal, i3//
?88 X.1.2 Reliability Evaluation X.1.2.1 Dominant Failure Modes X.l.2.1.1 Loss of Main feedwater (LOFW)
No single failure was identified which would make both feedwater trains unavailable.
Thus the dominant failure modes were combinations of two independent failures, each failing one subsystem.
X.1.2.1.2 LOFW With Loss of Offsite AC Power The dominant failure modes are the same as those identified above in the case of loss of main feedwater only.
X.1.2.1.3 LOFW with Only DC Power Available The dominant failure modes for this event are failure of the turbine driven pump subsystem due to test and maintenance outages, hardware failure, or human error.
Since the motor driven EFW pump would not be available upon loss of all AC power, auxiliary feedwater flow would be dependent on the single turbine driven pump subsystem.
Single valve or pump failure, or a manual valve being left in the closed position, or the subsystem being out due to test and maintenance are all significant contri-butors to the unavailability of the EFWS during this event.
X.1.2.1.4 Potential Interactions I b !.7
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I None
8-X.1. 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 pro-cedures to avoid or mitigate potential syst'em or operator failures.
The long-term recommendations (both generic, denoted by GL, and plant-specific) identified in this section 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.1.3.1 Short-Tern 1.
Recommendation GS 6 - 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:
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 prorr t' aligned.
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 frcm the primary AFW system water source to the steam The term APA system as used in these recomendations applies to the ANO-2 E?ef system.
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generators.
The flow test should be conducted with AFW system valves in their normal alignment.
2.
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 auto-matic 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 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 fsedwater 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-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.
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The automatic initiation signals and circuits shall be designed so that their f >ilure will not result in the loss of manual capability to initiate the AFW system from the control room.
3.
Recommendation - The Surveillance Requirements see. ion of the Technical Specications should add pressure and flow acc< otance criteria for the periodic (31-day) testing of the motor driven pumps.
X.1.3.2 Additional Short-Term Recommendations The following additional short-term recommendations 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 operating plants.
The, have not been examined for specific applicability to this facility.
1.
Recommendation - The licensee 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 occurring.
The low level alarm setpoint should allow at least 20 minutes for operator action, assuming that the largest capacity AFW pump is operating.
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. 2.
Recommendaton - 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 restarted and run for one hour.
Test acceptance criteria should include demonstrating that the pumps remain within the design limits with respect to bearing / bearing oil temperatures and vibration and that pump room ambient conditions (temperature, humidity) do not exceed environmental qualification limit; for safety-related equipment in the room.
3.
Recommendation - The licensee should ii.71ement 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 Technical 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 AFW system i3//
?93 train, and there is only one remaining AFW train available for operation should propose the 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 control room, this operator would realign the valves in the AFW system train from the test mode to itsoperational alignment.
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 meet safety grade requirements.
2.
Recommendation - The Arkansas Unit 2 AFW system design does not meet the high energy line break criteria in SRP-10.4.9 and Branch Technical Position 10-1; namely, that the AFW system should maintain the capability to supply the required AFW flow to the steam genera-tor (s) assuming a pipe break anywhere in the AFW pump discharge lines concurrent with a single active failure.
The licensee should evaluate the postulated pipe breaks stated above and (1) determine any AFW system design changes or procedures necessary to detect and isolate the break and direct the required feedwater flow to the steam generator (s) before they boil dry or (2) 13//
?94 describe how the plant can be brought to a safe shutdown condition by use of other systems which would be available following such postulated events.
3.
Recommendation - Concern was expressed to the licensee about the capability of the design to isolate a break occurring downstream of the steam admission valve to the turbine-driven pump during AFWS operation concurrent with a single active failure of the DC emergency Division II.
Assuming that without DC, the corresponding diesel generator will not be able to start, the break could not be isolated because of the loss of DC and AC power in Division II.
The licensee advised that analysis has been performed showing that there is sufficient residual magnetism to flash the diesel generator field and consequently the Division II diesel generator can be brought up to speed and voltage without the need of DC from the emergency batteries.
Thus, the break could be isolated if the failure of the DC emergency Division II does not result also in the loss of AC in the same division.
The licensee should submit for staff review the analysis with regard to starting the diesel generator without DC ertergency power available.
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ENCMSURE 2
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EASIS FOR AUXILIARY EEI'4ATER SYSTEM FEW EOUIFEMDES As a msult of scent staff reviews of cperating plant auxh/ feedwater systems (ArdS), the staff ccncludes that the design bases and criteria provided by. licensees for establishing AFWS requirements for flow to the steam generater(s) to assum ade-quate mmoval of reacter decay heat are not well defined or dec=ented.
We require that you provide the folicwing AFdS flow design basis infcmaticn as appli-cable to the design basis transients and accident conditions for your plant.
Identify the plant transient and accident conditions censidend in estab-1.
a.
lishing A?dS flow requirements, including the follcwing events:
1)
I. css of Main Feed (LT4)
- 2) L'4T4 w/lcss of offsite AC pcwer
- 3) UdT4 w/lcss of offsite and ensite AC pcwer
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Plant cocidewn 4
- 5) Turbine trip with and without bypass
- 6) Main steam isolatica valve closure
- 7) Main' feed line break
- 8) Main steam line break
- 9) Small break LOCA
- 10) Other transient er accident ccnditiens not listed above.
b.
Describe e.e plant protection acceptance crite:da and ccrmspending techni-cal bases used for each initiating event identified abcve. The acceptance criteria shculd addm ss plant limits such as:
- Maxi:m:m RCS pressure (PORV cr safer / valve actuaticn)
- Fuel temperar.:n er darage limits (33, FCT, maxim =n fuel cental temperar.
- RCS cooling rate limi: to avcid e:<cessive ecclant shrinkage
- Mini:m=1 steam genera:Or level tc assure sufficient steam genera:Or hea rs fer su= face to mmove decay. heat and/cr cocidown the prra"./ s'ystem.
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2.
Describe the analyses and assumptiens and corresponding technical justificaticn used with plant ccnditiens censidend in 1.a. above including:
Maximum mactor power (including instnrent ermr allowance) at the tire of a.
the initiating transient or accident.
b.
Tire delay frca initiating event to reactor trip.
Plant parameter (s) which initiates A?dS ficw and time delay between initiat-c.
ing event and intreduction of A?dS ficw into steam generator (s).
d.
Mini:m:n steam generator water level when initiating event occurs.
Initial steam generator water inventerf and depletien rate before and after e.
A?dS ficw cemences - identify reactor decay heat rete used.
f.
Maxin n pressure at which steam is released from steam generatcr(s) and agains:
which the AEd pump ::ust develcp sufficient head.
g.
Mini:n n nurber of steam generatcrs that =ust receive ATd ficw, e.g.,1 of 2, 2 of 47 h.
RC ficw ccnditien - centinued cperatien of RC pumps or nataral circulaticn.
Pzxi. on A?d inlet temperarara.
i.
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- j. Folicwing 'a pcstulated steam or feed l'ine break, time delay assured to isolate break and direct AJd ficw to intac steam generator (s). A?d pump ficw capacir.
allowance to accenodate the tire delay and maintain mini:m:n steam generator water level. Also identify credit taken for prirarf system heat iemoval due to blcwd:wn.
k.
Voltre and maxi.::n temperature of water in rain feed lines between steam generator (s) and A?dS conneden to rain feed line.
1.
Operating ccndition of steam generater ncrral blcwdcwn fcilcwing initiating event.
Prirarf and seccndar,/ system water and retal sensible heat used for cocidewn m.
and ATd ficw sizing.
n.
Tire at hot standby and time to eccldc n RCS to ER (cr SCS) system cut in temperarare to size AT4 water scurce inventcry.
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- 3.
Verify that the A?d pu:=s in your plant w2.ll supply the necessary ficw to the stee:n generator (s) as dere:=ined by iters 1 and 2 above considering a single failure. Identify the rargin in sizing the pt=p ficw to allcw for pt=p recir-culatien ficw, seal leakage and pt=p wear.
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199
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