ML17319A601
| ML17319A601 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Cook |
| Issue date: | 08/27/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML093450149 | List:
|
| References | |
| FOIA-80-515, FOIA-80-555 NUDOCS 8009170135 | |
| Download: ML17319A601 (14) | |
Text
SAFETY EVALUATION REPORT DONALD C.
COOK, UNITS 1
& 2 IHPLEHENTATIONS OF RECOMHENDATIONS FOR AUXILIARY FEEDWATER SYSTEHS I.
'ntroduction and Back round
- ne Three Hile Island Unit 2 (THI-2) accident and subsequent investigations and s udies highlighted the importance of the Auxiliary Feedwater System (APIS) n the mit gat.on of transients and accidents.
As part of our assessment of the THI-2 acc.'dent and related implications for operating plants, we evaluated the APA systems for all operating and near-term operating license plants having nuclear steam supply systems (NSSS) designed by Wes inghouse (NURER-0611) or Combustion Engineering (NUREG-0635}.
Our evaluations of these system designs are contained in +he NUREGs along with our recommendations for each plant and the concerns which led to each recommendation.
The objec.ives of the evalua-tion were to:
{1) identify necessary changes in AFW svstem desian or related procedures in order to assure the safe operation of these plants, and {2) to
',dentify other system characteristics of the APE! systems
- which, on a long term
- basis, may require system modifications.
To accomplish these objectives, we:
(1)
Reviewed plant specific APd system designs in-light of current regulatory requirements (SRP)
- and, (2)
Assessed the relative reliability of the various APA sys+ems under various loss of eedwater transients (one of which was the initiating event of THI-2} and other postulated failure conditions by determining the ootential for API system ailure due to coomon causes, sinole point vulnerabilities, and human error.
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Me concluded that the implementation of the recommendations identified during this review will considerably improve the reliability of the AFM systems for each operating plant.
The following generic recommendations did not apply to this plant:
1 GS-1, GS-3, GS-8, GL-1 and GL-2.
The basis for these recommendations can be found in Appendix III of NUREG-0611, and the system description which deter-mined the basis for not applying these recommendations can be found in Appendix X of NUREG-0611.
II.
Im lementation of Our Recommendations A.
Short Term Recommendations 1.
Recommendation GS "The licensee should lock open single valves or multiple valves in series in the AFM system pump suction piping and lock open other single valves or multiple valves in series that could interrupt all AFM flow.
Monthly inspections should be performed to verify that these valves are locked and in the open position.
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."
In response to this recommendation, the licensee indicated in a letter dated December ll, 1979 (AEP:NRC:00300), that each valve, not automati c or power-operated, in the auxiliary feedwater flow path is locked or sealed in its correct position.
The licensee, also stated, present
Technical Specifications Surveillance Item 4.7.1.2 requires monthly verification of unlocked valves in the auxiliary feedwater flow path and present procedures require monthly verification of locked or secured valves.
The licensee's present Technical Specification 6.0.1.c require implementation of these procedures.
In response to our request, the licensee proposed a change to Technical Specifications to include the locked or secured valves in the auxiliary feedwater flow path.
We have reviewed the licensee's response and Technical Specifications and conclude that Recommendation GS-2 is adequately met and, therefore, the licensee's response to GS-2 is acceptable.
2.
Recommendation GS "Emergency procedures for transfer ring to al ter-nate 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 available.
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."
In response to this recommendation, the licensee indicated in a letter dated triarch 28 1980 (AEP:NRC:00307A), that Procedure No. OHP-4022.055.003 entitled "Loss of Condensate to Auxiliary Feedwater Pumps" had been developed to fulfill this recommendation.
This procedure prov-des tho operator with instructions to switch the auxiliary feedwater pumps suction from the condensate storage tank to the alternate Essential Service Water Supply (ESW).
On a lo-lo level alarm for the condensate storage
- tank, an operator is sent to the auxiliary feedwater oumo rooms to align the essential service wite~ valves to nro~id~ suction tn each o< tho pumps By npeninn the manual valve and the motor-operated valve in ~eries in e~ch ~lt~rn~te ~upnly 1in~, both motor-driven auxiliary feedwater pumps and the turbine - driven auxiliary feedwater pump will be supplied by the ESW.
We-conclude that recommenda-tion GS-4 is adequately
- met, and therefore, acceptable pending verifi-cation of the procedure by the Office of Inspection and Enforcement.
3.
Recommendation GS "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 power to monitor pump bearing and/or lube oil temperatures.
If necessary, this operator would operate the turbine-driven pump in an on-off mode until alternating current power is restored.
Adequate lighting powered by direct current power sources and communications at local stations should also be pro-vided if manual initiation and control of the AFM system is needed.
(See Recommendation GL-3 for the long-term resolution of this concern.)"
In response to this recommendation, the licensee indicated in a letter dated December ll, 1979, that until modifications to meet recom-mendation GL-3 are complete, emergency procedures will provide for manual initiation and control of the auxiliary feedwater system in case of a complete loss of AC power.
The turbine-driven auxiliary feedwater pump areas have been provided with emergency lighting and emergency radio communications, both powered by direct current sources.
The existing turbine-driven auxiliary feedwater pump bearing cooling system is independent of both AC and DC power.
Me conclude that recommendation GS-5 is adequately
- met, and therefore, acceptable pending verification of the procedure by the Office of Inspection and Er fnrcement.
4.
Recommendation GS "The licensee should confirm flow path availability of an AFM system flow train that has been out of servi ce to perform periodic testing or maintenance as follows:
- Procedure 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 I
are properly aligned.
- The licensee should propose Technical Specifications to assure that prior to plant startup following an extended cold shut-
- down, a flow test would be performed to verify the normal flow path from the primary AFM system water source to the steam generators.
The flow test should be conducted with AFM system valves in their normal alignment."
In response to this recommendation, the licensee in a letter dated
- lay 23, 1980, indicated that the plant procedures would be changed to include back-up verification by a second operator to existing procedures which require verification of valve alignment after testing and maintenance.
In a letter dated December ll, 1979, the licensee indicated that, "the operating procedure for unit heatup from cold shutdown to hot standby calls for operation of both the motor driven auxiliary feed pumps and the turbine driven auxiliary feedpump.
The pumps take suction from thei r primary water source and deliver flow to the steam generators in order to control steam generator water levels."
!Ae concluded that a Techn'.cal Specification to roqu-'re a
flow test is not required, in that both motor driven pumps and the turbine driven pumps are used to deliver flow to the steam generators during unit star tup.
Me conclude that 'recommendation GS-6 is adequately
- met, and therefore, acceptable, pending verification of operating an'u surveillance procedures by the Office of Inspection and Enforcement.
5.
Recommendation GS-7 -"The licensee should verify that the automatic start AFM signals arid associated circuitry are safety grade.
If this cannot be verified, the APA 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 GL-5.
- The design should provi de 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.
- Hanual capability to initiate the auxiliary feedwater system from the control room should be retained and should be imple-mented 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 auto-matic 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 AFM system from the control room."
In response to this recommendation, the licensee indicated in a letter dated Oecember ll, 1979, that the present AFW system automatic initiation signals and control systems are safety grade.
The licensee's response to Recommendation GS-7 is acceptable.
The long term counter-part of this recommendation, GL-5 (Safety Grade Automatic Initiation) will be reviewed in detail and our evaluation will be contained in a supplement to this SER.
B.
Additional Short Term Recommendations 1.
Recommendation
- "The licensee should provide redundant level indica-tions and a low level alarm 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 AFM pump is operating."
In response to this recommendation, the licensee stated that the existing Condensat>>
Storage Tank (primary water source) is provided with redundant level sensors which provide signals for a continuous recorder.
Low and low-low alarms which are powered by the same OC power bus, are provided for each level indicator sensor.
The low-low level alarm is set to allow 35 minutes for operator action.
In our position letter of April 4,
- 1980, to the licensee we stated that this design was acceptable for the short term.
For the long
- term, we require the licensee to meet the following:
- 1) Provide a
redundant level indicator in addition to the existing redundant level alarms inside the control room.
The current design with a single level recorder does not meet the single failure criterion; 2) Power supplies for the level indication and alarms should be redundant.
The present design utilitizes a single DC power source..Since the con-densate storage tank is not classified seismic Category I, use of non-Class IE circuitry and power supplies are acceptable provided one power train has a back-up battery source; and 3) reset the low-low level alarm to allow at least 20 minutes for operator's
- action, assuming that the largest capacity AFW pump is operating.
The licensee's response to items 1
and 2 of our position is not acceptable.
The licensee is required to make modifications to provide redundancy as stated in our April 4, 1980 letter.
2.
Recommendation This recommendation has been revised from the ori inal recommendation in NUREG-0611
- "The licensee should perform a 48-hour endurance test on all AFM system pumps, if such a test or continuous period of operation has not been accomplished to date.
Following the 48-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 design limits with respect to bearing/bearing oil temperatures and vibration and that pump room ambient conditions (temperature, humidity} do not exceed environ-mental qualification limits for safety related equipment in the room."
In response to this recommendation, the licensee in a letter dated June 26, 1980, indicated that it will perform the 48-hour endurance test on all auxiliary feedwater pumps for both units by December 31, 1980.
The licensee further indicated the results of the test will be provided within 60 days after all tests are completed.
l Based on the above licensee's commitment, we conclude that the response to this recommendation is acceptable.
- However, we intend to evaluate the AFM pump test results to confirm that the AFW pumps are acceptable.
If the test results are not acceptable, we will then require modifi ca-tion and provide a safety evaluation regarding the test and modifica-tions.
3.
Recommendation
- "The licensee should implement the following require-ments which are identical to Item 2.1.7.b of NUREG-0578:
Safety-grade indication of AFM flow to each steam generator should be provided in the control room.
The auxiliary feed-water flow instrument channels should be powered from the emergency power diversity requirements for the auxiliary feed-water system set forth in Auxiliary Systems Branch Technical Position 10-1 of the Standard Review Plan, Section 10.4.9."
Our Lessons Learned Implementation Task Force has completed its review of the short term requirements and their evaluation was forwarded to
- 11 the licensee in a letter dated March 20, 1980.
The long term require ments for this..recommendation are still under review.
Our evaluation of this matter will be contained in a supplement to this SER.
4.
Recommendation
- "Licensees with plants which require local manual realignment of valves to conduct periodic tests on one AFW system
- train, and there is only one remaining AFW train available for operation, should propose Technical Specifications to provide that a dedicated individual who is in communicati'on 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.
The licensee, in its letter of December ll, 1979, stated that this recommendation does not apply to D. C.
Cook 182, The current auxiliary feedwater system includes a turbine-driven feedwater pump and two motor-driven feedwater pumps shared by both units.
Each motor-driven auxiliary pump is connected to two steam gene ators in each unit; thus, each unit's four steam generators are supplied by both motor-driven pumps.
The licensee is presently modifying the AFS to provide three AFW pumps per unit, one turbine-driven pump and two motor-driven pumps.
- Further, Technical Specification only allow testing of one pump at a time.
We conclude that this recommendation does not apply to D. C.
- Cook, 1&2.
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Lon Term Recommendations commendation.GL "The licensee is currently performing modifications to make the turbine driven train independent of AC power sources.
The following recommendation shoul d be met when these modifications are complete.
At least one AFM system pump and its associated flow path and essential instrumentation should automatically initiate AFW 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 is acceptable."
In respone to this recomnendation, the licensee indicated in a letter dated December 11, 1979, that "The turbine driven auxiliary feedwater pump is being modified to eliminate its-dependence on AC power for automatic initiation of flow and operation."
The staff SER supporting Amendment 35 to Facility Operating License addresses this issue.
It was concluded in tnat amendment that the licensee's response i-s 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 automati c protection of the pumps is necessary following a seismic event or a tornado.
The time available before pump damage, the alaris and indi cations 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 upon to prevent pump damage.
Consideration should be given to
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providing pump protection by means such as automatic switchover of the pump suctions to the alternate safety-grade source of water, automati c pump trips on low suction pressure or upgrading the normal source of water to meet Seismic Category I and tornado protec'tion requirements."
Kn response to this recommendation, the licensee by a letter dated December ll, 1979, indicated that an automatic AFM pump trip on low suction pressure will be installed.
The pump trip will be provided with an alarm in the control room and operators will be instructed to follow emergency procedures for transferring to alternate source of AFW supply.
We conclude the licensee's response meets our recommenda-tion and, therefore, is acceptable.
3.
Recommendation GL "The licensee should upgrade the AFW system automati c initiation signals and circuits to meet safety-grade requi re-ments."
1n response to this recommendation, the licensee indicated in a letter dated December ll, 1979, that the present AFW system automatic initia-tion signals and circuits are safety grade.
We will review the licen-see's design in detail and our evaluation will be contained in a
supplement to this SER.