ML19254D290
| ML19254D290 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 10/19/1979 |
| From: | Peoples D COMMONWEALTH EDISON CO. |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7910230291 | |
| Download: ML19254D290 (24) | |
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Commonwealth Edison one first National Plata. Chicago. Ilhnois Address Reply to. Post Office Box 767 ChrCago. flhnois 60690 October 19, 1979 Mr. Darrell G. Eisenhut, Acting Director Division of Operating Reactors U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Zion Station Units 1 and 2 Response to NRC Requirements for Auxiliary Feedwater Systems NRC Docket Nos. 50-295 and 50-304 Reference (a):
September 18, 1979 letter from D.
G.
Eisenhut to C.
Reed transmitting "NRC Requirements for Auxiliary Feedwater Systems at Zion Station Units 1 and 2"
Dear Mr. Eisenhut:
In Reference (a), the NRC Staff requested Commonwealth Edison Company to evaluate the Zion Station Auxiliary Feedwater Systems against the applicable requirements specified in of Reference (a) to determine the degree to which the Zion systems conform to the Staff requirements.
In addition, Cnclosure 2 of Reference (a) contained a generic NRC Staff re-quest for additional information regarding auxiliary feedwater system flow requirements.
Attachments 1 through 3 to this letter contain Commonwealth Edison's responses to these NRC Staff require-ments.
More specifically, Attachments 1 and 2 contain responses to the NRC Staff's short-term recommendations in Enclosure 1 of Reference (a).
Unless otherwise indicated, all proposed design, procedure or technical specification changes associated with these responses will be implemented, completed or submitted for Staff review by January 1, 1980. contains responses to the NRC Staff's long-term recommendations in Enclosure 1 of Refccence (a).
l'nless otherwise indicated, all proposed design, procedure, or technical specification changes associated with these responses will be implemented, completed or submitted for Staff review by January 1, 1981.
Curren the Westinghouse Operating Plant owners' Group is considecing the possibility of a generic response to the NRC Staff's generic request for the additional information 11"/
212 7910230 2-91
Commonwealth Edison til?C Docket tion. 50-295/304 Mr. Darrell G.
Eisenhut: October 19, 1979 as outlined in Enclosure 2 of Reference (a).
Therefore, a schedule for submittal ot the requested information is not available at this time.
!!oweve r, within thirty (30) days Commonwealth Edison will provide the NRC Staff with a schedule for responding to the items of Enclosure 2.
Please address any questions that you might have regarding thin matter to this office.
On? (1) signed original and thirty-nine (39) copies of this letter are provided for your use.
Very truly yours, (I
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Pe op'le s Director of Nuclear Licensing WFN:mae attachment (3) 1"/
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.TTTACHMENT 1 COMMONWEALT!! EDISON COMPANY'S RESPONSES TO NRC STAFF'S SHORT-TERM RECOMMENDATIONS REGARDING AUXILIARY FEEDWATER SYSTEMS AT ZION STATION NRC DOCKET NOS. 50-295 AND 50-304
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1.
NRC Recommendation GS-1 The licensee should propose modifications to the Technical Specifications to limit the time that one AFW system pump and its associated flow train and essential instrumentation can be inoperable.
The outage time limit and subsequent action time should be as required in current Standard 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.
Commonwealth Edison Response to GS-1 Commonwealth Edison has determined that the NRC recommended technical specification modification is not necessary.
The basis for this determination follows.
The design basis of the Zion Station Auxiliary Feedwater System (AFW) as stated in lion FSAR Section 6.7 and as analyzed in Section 14.1.9, I,oss of Normal Feedwater, clearly indicates the adequacy of the APW system.
The single active failure analysis states that with the three pumps installed, any one is sufficient to supply the required flow.
Section 3.7.2 of the Zion Station Technical Specifica-tions is based on the above information and requires two of the three AFW pumps operable for reactor operation.
Should only one AFW pump be operable, reactor operation is permios i,le only during the succeeding seven days.
In addition, whenever the turbine-driven pump is not available, the motor-driven pumps are realigned by procedure to different headers, therefore, maintaining two distinctly separate trains for AFW supply.
Thus, considering the system design, i.e.,
three full capacity or greater pumps, each with an independent power supply, additional technical specification requirements are not necessary.
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2.
NRC Recommendation GS-2 The licensee should lock open single valves or multiple valves in series in the AFW system pump suction piping and lock open other single valves or multiple valveu in series that could interrupt all AFW flow.
Fonthly inspections should be performed to verify that these valves are locked and in tho open position.
These in-spections should be proposed for incorporation into the surveillance requirements of the plant Technical Specifica-tions.
See Recommendation GL-2 for the longer-term resolution of this concern.
Cammonwealth Edison Response to GS-2 Commonwealth Edison has determined that the NRC recommended technical specification modification is not necessary.
The basis for this determination follows.
Present operating procedures and valve lineup sheets require that all manual valves that could interrupt flow to and from any AFW system pump be locked open.
In addition, station administrative procedures that address the removal and restoration of equipment from and to service, require review and approval of valve lineup changes by licensed operators and also management verification of valve lineups upon restoration to service.
A provision is being added to the monthly operating surveillance of the AFW system to verify the status of the applicable valves.
The surveillance procedure currently ensures that the normal flow path for AFW to the stean genera tors is functional.
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NRC Recommendation GS-3 The licensee has stated that it throttles AFU system flow to avoid water hammer.
The licensee should re-examine 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 flow to the necessary steam generators to assure adequate decay heat removal following loss of main feedwater flow and a reactor trip from 100% power.
In cases where this reevaluation results in an increase in initial APW system flow, the licensee should provide suf ficient information to demonstrate that the required initial AFW system flow will not result in plant damage due to water hammer Commonwealth Edison Response to GS-3 Section 14.1.9, Loss of Normal Feedwater, of the Zion FSAR indicates that the purpose of the analysis is to demonstrate that following a loss of normal feedwater the APW system is captble of removing the stored and residual heat and thus prevent either overpressurization of the reactor coolant system or un-covery of the reactor core.
In addition to other conservatisms included in the analysis, the AFW flow is assumed to be 410 GPM.
The APW system is set by procedure to deliver 420 GPM (105 GPM per steam generator) following the locs of main feedwater flow and a reactor trip.
Use of periodic tests and general operating pro-cedures in all cases will leave the AFW system throttled to deliver the required minimum flow.
Following the determination of conditions after a reactor trip, the APW flow can be throttled so as not to exceed 210 GPM to any steam generator.
This action is based upon Westinghouse's recommendations for minimizing water hammers.
With regard to minimizing the potential for water
- hammers, i.e., maintaining the feedwater lines and spargers full of water, Commonwealth Edison i nstalled J-tubes on the 2C Steam Generator during the Spring 1978 refueling outage for Zion Units 2.
Commencing with the current Zion Unit 1 Fall 1979 refueling outage, J-tubes will be installed at the rate of one steam generator per refueling outage until all Zion Station steam generators have been modified (see August 8, 1979 letter from Cordell Reed to A. Schwencer).
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NRC Recommendation GS-4 Emergency procedures for transferring to alternate cources of AFW supply should be available to the plant operators.
These procedures should include criteria to inform the operator when, and in what order, the transfer to alternate water sources should take place.
The following cases should be covered by the procedures:
The case in which the primary water supply is not initially available.
The procedures for this case should include any operator actions required to protect the APW system pumps against self-damage before water flow is initiated; and, The case in which the primary water supply is boir.g depleted.
The procedure for this case should provide for transfer to the alternate water sources prior to draining of the primary water supply.
Commonwealth Edison Response to GS-4 Emergency procedures that establish the criteria for transferring to alternate sources of AFW supply will be developed to cover the cases addressed by the NRC in its recommendation.
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5.
NRC Recommendation GS-5 The as-built plant should be capable of providing the required AFW flow for at least two hours from one AFW pump train independent of any alternating current power source.
If manual 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 lube oil for the turbine-driven pump bearings 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 procedures should provide for an individual to be stationed at the turbine-driven pump in the event of the loss of all alternating current pcwer to monitor pump bearing and/or lube oil temperatures.
If necessary, this operator would operate the turbine-driven pump in an on-off modo until alternating current power is restored.
Adequate lighting powered by direct current power sources and communications at local stations should also be provided if manual initiation and control of the AFW system is needed.
(See Recommendation GL-3 for the longer-term resolution of this concern.)
Commonwealth Edison Response to GS-5 Currently, the as-built system at Zion Station is not capable of providing the required AFW flow for two hours independent of any alternating current power source.
Therefore, until design changes are made, emergency procedures will be developed to operate the turbine-driven AFW pump in an on-off mode in the event of the loss of all alternat-ing current.
As indicated in response to NRC Recommendation GL-3 (see Attachment 3), the modifications necessary to permit the turbine-driven AFW pump to operate for at least two hours independent of any alterna ting current power source will be implemented as a long-term item, i.e.,
by January 1, 1981.
Adequate direct-current-powered lighting and sound-powered-communications facilities already exist in the vicinity of the turbine-driven pumps.
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NRC 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 properly aligned.
The licensee should propose Technical Specifica-tions 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 con-ducted with AFW system valves in their normal alignment.
Commonwealth Edison Response to GS-6 As indicated in the response to NRC Recommendatien GS-2, at Zion Station administrative procedures that address removal and restoration of equipment from and to service and that establish abnormal valve lineups require both a review by licensed operators prior to their implementation and a management verification of the restoration to a normal valve lineup.
Section 3.7.1.2 of the Zion Station Technical Specifications requires that two AFW pump systems be operable whenever the reactor is taken from cold shutdown to hot standby.
Operability is proved by a periodic test requiring a flow check.
Operating procedures direct that this periodic test be accomplished prior to leaving cold shutdown.
In addition, steam generator level control on startup is performed using the AFW system.
When main feedwater flow is established and AFW is to be removed from operation, station operating procedures require the AFW system to be functioning in its normal alignment and at design flow.
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NRC Recommendation GS-7 The licensee should verify that the automatic start APW 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 fur ational requirements listed below.
For the longer term, the automatic initiation signals and circuits should be upgraded to meet safety-grade require-ments as indicated in Recommendation GL-5.
The design should provide for the automatic initiation of the auxiliary feedwater system flow.
The automatic initiation signals and circuits should be designed so that a single failure will not result in the loss of auxiliary feedwater nystem 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 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 initiate the AFW system from the control room.
Commonwealth Edison Response to GS-7 The auxiliary feedwater system at Zion Station is automatically initiated by low steam generator level, loss of off-site pc,wer, or a safety injection signal and meets the control grade requirements of NUREG-0578.
The initiation circuitry will be reviewed and any changes necessary to meet the NUREG-0578 safety-grade requirements will be proposed by January 1, 1980.
It will be necessary for the NRC review to proceed on an expeditious schedule for installation of any changes to be completed by January 1, 1981.
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NRC Recommendation GS-8 The licensee should prcpose modifications to the Technical Specifications to include a Limiting Condition of Operation when the condensate storage tank level falls below the 170,000 gallon level, considering both one and two-unit operation.
Commonwealth Edison Response to GS-8 Technical Specifications providing for the required ondensate storage tank level will be proposed.
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ATTACIIMENT 2 COMMONWEALTl! EDISON COMPANY'S RESPONSES TO NRC STAFF's ADDITIONAL SliOP.T-TERM RECOMMENDATIONS REGARDING AUXILIARY FEEDWATER SYSTEMS AT ZION STATION NRC DOCKET NOS. 50-295 AND 50-304 I I ' /
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NRC Recommendation The.icensee should provit 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 eccurring.
The low-level alarm setpoint should allow at least 20 minutes for operat.or action, assuming that the largest capacity APW pump in operating.
Commonwealth P.dison Response Adequate primary water supply level indication and redundant level alarms presently exist.
Tne low-level alarm setpoint allows the operator more than 20 minutes to make up water to the primary supply, or to transfer the largest capacity AFW pump to an alternate supply of water.
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NRC Recommendation The licensee should perform a 72-hour endurance test on all APW system pumps, if such a test or continuous period of operaticn 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 tnat the pumps remain within design limits with respect to bearing /
bearing til temperatures and vibration and that pump room ambient conditions (temperature, humidity) do not exceed environmental qualification limits for safety-related equipment in the roota.
Commonwealth Edison Response Commonwealth Edison will perform the recomnended endurance test.
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NRC Pecommendation The licensee should implement the following requirementn as specified by Item 2.1.7.h on Page A-32 oi NUREG-0578:
" Safety-grade indication of auxiliary feedwater flow to each steam generator shall he provided in the control room.
The auxiliary feedwater flow instrument channels shall be powered from the emergency buses con-sittent with satisfying the emergency power diversity requirements for the auxiliary feedwater system set forth in Auxiliary Syrtems Branch Technical Position 10-1 of the Standard Review Plan, Section 10.4.9."
Commonwealth Edison Response The auxiliary feed flow to each steam generator is indicated in the Zion control room and meets the control grade criteria of NUREG-0578.
In a.idition, each steam generator level is indicated on three narrow range and one wide range gauge in the control room.
The existing flow instrumentation will be reviewed an.1 any changes necessary to meet the NUREG-0578 safety-grade requirements will be outlined by January 1, 1980.
It is ex-pected that any changes required would be complete by January 1, 1981.
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NRC Recommendation Licensees with plants which require local manual realignment of valves to conduct periodic tests on one AFW system train and which have only one remaining APW 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 control room, this operator would realign the valves in the AFW system train from the test mode to its operational alignment.
Commonwealth Edison Response Commonwealth Edison has determined that the NRC recommended technical specification modification is not neces-sary.
The basis for this determination follows.
During the periodic tests of the AFW system, only one local manual valve of any significance is operated.
This valve is in the backup water supply to the turbine-driven AFW p ump.
Operation of this valve does not affect the ability of the pump to deliver the normal water supply to the steam generators.
In addition, the operability of the pump with the normal water supply is verified in the periodic test just prior to alignment of the above manual valve.
Thus, based on the above and the fact that verifica-tion of the subject valve position will be incorporated into the test as discussed in the response to NRC Recommendation GS-2 in, additional technical specification requirements are..0L necessary.
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ATTACf! MENT 3 COMMONWEALTH EDISON COMPANY'S RESPONSES TO NRC STAFF'S LONG-TERM RECOMMENDATIONS REGARDING AUXII,I ARY FEEDWATER SYSTEMS AT ZION STATION
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NRC Recommendation GL-2 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 supplies 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 ot 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.
Commonwealth Edison Response to GL-2 At Zion Station, the alternate AFW system water supply connects downstream of the primary water supply isola-tion valves.
There is an additional redundant parallel flow path for the primary water supply from the other unit.
This path also connects downstream of the above valves.
(A corrected copy of the simplified system drawing is attached to this response)
As indicated in the response to NRC Recommendation GS-2 in Attachment 1, existing procedural controls and surveillance requirements preclude the necessity for additional technical specification requirements.
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MRC Recommendation GL-3 At least one AFW system pump and its an30ciated flow path and essential instrumentation should automatically initiate APW system flow and be capable of being operated independently of any alternating current power source for at least two hours.
Conversion of direct current power to alternating current power is acceptable.
Commonwealth Edison Response to GL-3 Zion Station will make the modifications necessary to permit the turbine-driven AFW pump system to operate for at least two hours independent of any alternating current power source.
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3.
NRC Recommendation GL-4 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 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.
Commonwealth Edison Response to GL-4 At Zion Station, automatic AFW pump trips on low suction pressure already exist.
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NRC Recommendation GL-5 The licensee should upgrade the AFW system automatic initiation signals and circuits to meet safety-grade requirements.
Commonwealth Edison Response to GL-5 As indicated in the response to NRC Recommendation GS-7 in Attachment 1, the auxiliary feedwater system at Zion Station is automatically initiated by low steam generator level, loss of off-site oower, or a safety injection signal and meets the control grade requirements of NUREG-0578.
The initiation circuitry will be reviewed and any changes necessary to meet the NUREG-0578 safety-grade requirements will be proposed by January 1, 1980.
It will be necessary for the NRC review to proceed on an expeditious schedule for installa tion of any changes to be completed by January 1, 1981.
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233 3.5
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NRC Recommendation The licensee shcald evaluate the consequences of a postulated break in the steam line to the turbine-driven AFW pump to determine the need to qualify the AFW system valves, valve actuators, and instrumentation for the environmental conditions resulting from such a high energy line break in order to maintain operability of the motor-driven AFW pumps and their associated flow trains.
Commonwealth Edison Response As addressed in the response to Question 10.16 in the Zion FSAR, the rupture of a high-energy line in the auxiliary building will not cause loss of operability of the motor-driven AFW pumps.
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NPC Recommendation There are no valves in either of the common headers supplied from the motor-driven AFW pumps or the turbine-driven pump to all four steam generators.
A pipe break in either header could cause loss of all AFW flow to all steam generators frem either the motor-driven or turbine-driven AFW pumps.
The licensee should evaluate a postulated pipe break in either header and indicate the AFW system design changes or emergency procedures necessary to detect and isolate the break and boil direct AFW flow to the steam generators before the i
dry.
Commonwealth Edison Response An evaluation of the postulated pipe break will be performed and appropriate actions will be taken to assure this concern is addressed.
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