ML17258A832
| ML17258A832 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 01/29/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17258A831 | List: |
| References | |
| NUDOCS 8103020116 | |
| Download: ML17258A832 (16) | |
Text
SAFETY EVALUATION REPORT R. E.
GINNA IMPLEMENTATION OF RECOMMENDATIONS FOR AUXILfARY FEEDWATER SYSTB4S I.
Introduction and Back round The Three Mile Island Unit 2 (TMI-2) accident and subsequent investigations and studies highlighted the importance of the Auxiliary Feedwater System (AFMS) in the mitigation of severe transients and accidents.
As part of our assessment of the TMI-2 accident and related implications for operating plants, we evaluated the AFM systems for all operating plants having nuclear steam supply systems (NSSS) designed by Mestinghous~.
'.NUREG-0611) or Combustion Engineering (NUREG-0635).
Our evaluations of these systems designs are con-tained in the above NUREGs along with our recomnendations for each plant and the concerns which led to each recommendation.
The obiectives of the evalua-tion were to:
(1) identify necessary changes in AFM system design or re:ated procedures at the operating facilities in order to assure the continued safe operation of these plants, and (2) to identify other system characteristics of the APE/ system which, on a long term basis, may require system modifica-tions.
To accomplish these objectives we:
(1)
Reviewed plant specific AFM system designs in light of current regulatory requirements (SRP) and, (2)
Assessed the relative reliability of the various AFM systems under various loss of feedwater transients (one of which was the initiating event of TMI-2) and other postulated failure conditions by determining the potential for AFM system failure due to common causes, single point vulnerabilities, and human error.
"Me concluded that the implementation of the following recommendations identi-fied during this review wil, considerably improve the reliability of the AFM systems for each operating plant.
The following plant specific recommendations did not apply to this plant:
GS-l, GS-2, GS-4, GS-8 and GL-1, GL-2, GL-4 The basis for these recoranendations can be found in Appendix III of NUREG-0611 and the system description which determired the basis for not applying these recommendations can be found in Section X of NUREG-0611.
A.
Short Term Recommendations 1.
Recommendation GS The licensee has stated that it throttles AFM system flow to avoid water harmer.
The licensee should reexamine the practice of throttling AFM system flow to avoid water hammer.
The licensee should verify that the AFM 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 AFM system flow. the licensee should provide sufficient information to demonstrate that the required initial AFM system flow will not result in olant damage due to water hamner.
The licensee responded by letter dated November 28,
- 1979, and stated that both motor driven AFM pumps start and deliver at least 200 gpm to their respective S/Gs.
Only the flow from one (1) AFM pump (200 gpm) is needed to remove decay heat.
The discharge valves on the motor driven AFM pumps are automatically throttled to less than 230 gpm but more than 200 gpm upon pump start.
Automatically throttling the valves conserves auxiliary feedwater and helps limit the cooldown when all the pumps start but is not don>> to avoid water hammer.
Before an evaluation can be completed on this recommendation, the staff req'uires that the licensee provide the b"sis for limiting cooldown by throttling the discharge valves.
- Further, the licensee should provide the results of a single failure evaluation of the automatic throttling feature.
2.
Recommendation
- The plant has AC dependent service water cooling of the lube oil for the turbine driven pump.
The turbine driven feedwater pump has an AC lube oil pump and a
These pumps direct the oil through a heat exchanger which depends on the AC powered service water system pumps to cool the oil.
Tn the event of a total loss of AC power, lube oil cooling capability for the turbine-driven pump will be lost due to the loss of AC power to the service water pumps.
The turbine driven pump could cease to function due to the loss of lube oil cooling.
The as-built plant should be capable of providing
.he required AFM f ow for at least two hours from one AFH pump train independent of any alternating current power source.
Subsequent to this review, the ',icensee conducted a test to demonstrate that the turbine-driven pump could operate for two hours without lube oil cooling water flow.
The test was run for one hour and 45 minutes with the
final one hour and 15 minutes of the test with the pump at rated speed, but at 50K of required plant flow.
preliminary test results indicate the pump and turbine bearing temperatures remained within allowable limits.
The staff is evaluating these test results to determine if the test data will support a conclusion that the'required flow can be provided independent of'ny AC power source.
Until this evaluation is
- complete, interim emergency procedures should be established which pro-vide 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/
turbine bearing and/or lube oil temperatures.
Kf necessary.
the 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 provided if manual initiation and control for the AFM system is needed.
(See Recommendation GL-3 for the longer term resolu-tion of this concern.)
The licensee responded by letters dated November 28, 1979, and Hay 22,
- 1980, and stated that RGKE believes that the turbine driven AFif pump is capable of providing the required AFM flow for a period of two hours independent of AC power.
A test of the turbine driven pump was conducted August 10, 1979, to support that conclusion.
En a letter dated August 15, 1979, the licensee provided the test data and information on the characteristics of the pump to demonstrate the adequacy of the recirculation flow test to represent a full flow test.
The staff evaluation, provided in a letter dated April 18, 1980, stated that the RG&E response is acceptable for the short term provided interim emergency procedures for a complete loss of AC power are implemented that require an operator to be stationed at the turbine driven pump to monitor bearing oil temperatures and notify the control room if limits are exceeded.
This will allow for on-off operation of the pump if necessary.
In a letter dated tray 22, 1980, the licensee stated that they had imple-mented a procedure to assure the pump is periodically checked if all AC power is lost.
8ased on the results of the recirculation flow test and the procedure to periodically check the turbine driven pump, we have concluded that the licensee's response is acceptable for the short term.
3.
Recommendation GS The licensee should confirm flow path availability of an AFH system flow train that has been out of service to perform periodic testing or maintenance as follows:
a.
Procedures should be implemented to require an operator to deter-mine that the AFM system valves are properly aligned and a
second operator to independently verify that the valves are properly aligned.
b.
The licensee should propose Technical Specifications to assure ihat prior to plant startup following an extended cold shutdown, a flow test would be performed to verify the normal flow path from the primary AFA system water source to the steam generators.
The flow test should be conducted with APr( system valves in their normal alionment.
The licensee responded in letters dated November 28, 1979, and t1ay 22, 1980, stating that after the performance of periodic tests or mainten-ance on the Auxiliary Feedwater and Standy Auxiliary Feedwater
- System, the Results and Test Department personnel return all the valves mani-pulated to their safeguard position as directed by the procedure.
In addition, at the completion of the test, an independent verification of valve alignment is performed by the Operation Department personnel.
The independent verification is part of the procedure and applies to all safety related valves in the system that are manipulated during testing or maintenance.
Once the independent verification is accom-
- plished, the Shift Supervisor signs the procedure as completed.
Me find the response to part a. of this recommendation acceptable.
Regarding part b. the licensee stated that their technical specifica-tions already require that AFM flow paths be operable.
Their current practice to meet this technical specification is to perform flow tests that demonstrate that the flow paths from the primary AFM water source to the steam generators is operable.
~The,licensee.
has stated that revisions to their technical specifications would be proposed which will incorporate the verification of flow path operability following extended cold shutdowns.
Me, therefore, conclude that part b. of this recommendation is acceptable pending receipt of a proposed, acceptable Technical Specification.
4.
Recommendation GS The licensee should verify that the automatic start AFM system signals and associated circui try are safety-grade.
If this cannot be verified, the AFM 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.
(1)
The design should provide for the automatic initiation of the auxiliary feedwater system flow.
(2)
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.
(3)
Testability of the initiation signals and circuits shall be a
feature of the design.
(4)
The initiation signals and circuits should be powered from the emergency buses.
(5)
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.
(6)
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.
(7)
The automatic initiation signals and circuits shall be designed so that their failure will not result in the loss of manual capa-bility to initiate the APJ system from the control room.
The licensee responded by letters dated October 17, 1979, November 19,
- 1979, and December 14, 1979, providing responses to the seven require-ments of this recoranendation.
For the short term, the licensee's response to this recommendation adequately satisfies the "control grade" requirement of this recommendation and is, therefore, acceptable.
Refer to GL-5 for the long term "safety grade" evaluation of this item.
B.
Additional Short Term Recommendations 1.
Recommendation
- The licensee should provide redundant level indica-tions and low level alarms in 'the control room for the AFM system primary water supply, to allow theperator 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.
The licensee responded by letter dated November 28, 1979, and stated that the existing single train condensate storage level indication provides a low level alarm which provides more than 20 minutes warning for operator action to switch to the service water supply as
the 'AFN source.
The licensee further stated that the level indication and alarm circuits will be modified to provide redundancy by January 1,
1981.
Me informed the licensee by letter dated April 18, 1980. that their response to this recommendation was acceptable provided the redundant indication and alarm circuitry was redundant all the way from the detectors to the control room indicators including their power supplies.
They also should be powered by emergency busses with at least one circuit backed by a battery source.
By letter dated Hay 22,
- 1980, the licensee verified that their design will meet the above reconmendations.
Me find the licensee s response to this recommendation is acceptable.
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 AFH 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 environmental qualification limits for safety-related equipment in the room.
The licensee should provide a summary of the conditions and results of the tests.
The summary should include the following:
1} A brief description of the test method (including flow schematic diagram) and how the test was instrumented (i.e., where and how bearing temperatures were measured).
- 2) A discussion of how the test conditions (pump flow,
- head, speed and steam temperature) compare to design operating condi-tions.
- 3) Plots of bearing/bearing oil temperature vs. time for each bearing of each ARf pump/driver demonstrating that temperature design limits were not exceeded.
4)
A plot of pump room ambient temperature and humidity vs. time demonstrating that the pump room ambient condi-tions do not exceed environmental qualification limits for safety-related equipment in the room.
- 5) A statement confirming that the pump vibration did not exceed allowable limits during tests.
By letter dated Hay 28, 1980, the licensee provided the results of the 48-hour endurance tests for the Standby Auxiliary Feedwater pumps.
A description of how the test was conducted and instrumented included the water source and flow path for the test and the method of monitoring and recording the pump and motor bearing temperatures.
The test condi-.
tions were in conformance with the pump speed and discharge pressure conditions specified in th>> recommendation.
Plots of the bearing oil temperatures versus time were provided for each pump and each motor bearing and indicated that design limits were not exceeded.
The data provided on pump hearing vibration indicated that the vibra-tions, which were measured periodically during the test, were well within the allowable limit.
Ouring the endurance test.
the outside door of the pump room was kept open to the environment to help maintain the supply tank temperature
low and to accommodate a condensate supply tank bleed discharge hose.
Therefore, the temperature and humidity measurements did not reflect actual pump room environmental conditions.
The licensee should provide a su@vary of the results of an analysis to determine the pump room enviro'nmental conditions under actual operating conditions and a comparison of these conditions with the environmental qualification limits of the safety related equipment in this room.
Pending receipt of acceptable information on the pump room environ-
- ment, we conclude that the licenseels response to this recoranendation for the standby auxiliary feedwater pumps is acceptable.
By letter dated May 22, 1980, the licensee proposed not performing an endurance test of the main motor driven auxiliary feedwater pumps because of the extensive operating times that have been accumulated over the past ten years for these pumps.
This part of the response is noi acceptable
-.Me =will require.the licensee to,perform the 48-hour endurance tests on the main motor driven pumps as perscribed in our April 18, 1980 letter to RGINE or provide the information in the original recommendation.
- Further, we will require the licensee to perform the endurance test for the turbine driven pumps.
Me will complete our evaluation of this matter when the information is available and provide a supplement to this SER input.
3.
Recommendation
- The licensee should implement the following require-ments as specified by Item 2.1.7.b on page A-32 of iHUREG-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 emer-gency power diversity requirements for the auxiliary feedwater system set forth in Auxiliary Systems Branch Technical Position 10-1 of the Standard Review Plan, Section 10.4.9."
The licensee's response was provided in letters dated Novembe~ 19,
- 1979, and December 14, 1979.
The Instrumentation and Control Systems Branch will review this response and provide a safety evaluation at a later date.
4.
Recommendation - Licensees with plants which require local manual realignment of valves to conduct periodic tests on one AFM system train and which have only one remaining AFM 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 AF'1 system train from the test mode to its operational alignment.
The licensee's response by letter dated November 28, 1979, stated that the AFM system is composed of two main motor driven pumps, one turbine driven pump and two standby motor driven pumps all of which are capable of delivering the minimum required flow.
Therefore, during periodic testing the flow trains are tested individually and more than, one additional flow train is available.
We conclude, there-fore, that this recormendatfon does not apply to R. E. Ginna.
C.
Lon Term Recommendations 1.
Recommendation GL At least one AFM system pump and its associated flow path and essential instrumentation should automatically initiate AFW system flow and be capable o< being operated independently of any alternating curren". power source for at least 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
Conversion of direct current power to alternating current is acceptable.
The licensee responded by letter dated November 28,
- 1979, and stated that all AC power dependence will be removed by January 1, 1981, by making a piping change which will recirculate a small amount (10-15 gpm) of auxiliary feedwater from the pump discharge (or from a pump inter-mediate stage),
to the lube oil cooler and end bearing.
He conclude that with this piping change, the turbine-driven auxiliar': feedwater system can be operated independent of any AC power sources.
The licen-see should clarify that this flow train can be automatically initiated independently of any AC power source (refer to GS-7).
We require that this flow train be automatically initiated independently of any AC power source.
2.
Recomnendation
- The licensee should evaluate the water source capa-bilities (AC powered service water pumps, condensate transfer pumps and the limited inventory of condensate storage tank water gravity feed to the turbine pump suction} to assure that there is a water source sufficient to supply the required AFH flow for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> indepen-dent of any AC power source.
'By letter dated March 28, 1980, RGSE provided the decay heat analyses on which they have based their conclusion that 22,500 gallons total inventory in'the condensate storage tanks will provide the required flow by gr avity feed to the pump sucti on.
Ginna s present technical specifications require that at least 15,000 gallons be maintained in the condensate storage tanks.
Their stated practice is to maintain much more inventory than 15,000 gallons.
RG,rE will file an application to amend their technical specifications in the near future and in the interim will issue an administrative order to maintain at least 22,500 gallons in the tanks, The staff finds the licensee's response to this recommendation is acceptable pending Inspection and Enforcement verification of the administrative order and pending receipt of an acceptable application for an amendment to their technical specification.
3.'ecommendation GL The licensee should upgrade the AR4 system auto-matic initiation signals,and c-ircuits,to meet safety;grade require-ments.
The licensee responded by letter dated November 28,
- 1979, and stated that:
the existing automatic initiation signals and circuits meet safety grade requirements.
The evaluation of this recommendation will be provided by the Enstru-mentation and Control Systems Branch.
0.
Considerations Based on the S stematic Evaluation Pro ram 1.
There is no provision for either the main or standby AFHSs to auto-matically terminate flow to a depressu: ized steam generatu>
<,nd auto-matically provide flow to the intact steam generator.
This is accomplished by the control room operator.
2.
The staff will reevaluate the main and standby AFHS with respect to internally and externally generated
- missiles, seismic design require-
- ments, and flood and tornado protection.
The above two items are under review by the Systematic Evaluation Program.
E.
Recommendation "Basis for Auxiliar Feedwater S stem Flow Re uirements" In Enclosure 2 to our letter of October 22,
- 1979, we requested the licen-see to provide certain information regarding the design basis for. AFWS flow requirements.
By letter dated July 14, 1980, the licensee provided responses
-to this recommendation.
We are unable to complete this review since the licensee's response does not address the feedwater line break transient.
The feedwater line break transient should be evaluated in accordance with the criteria in SRP 15.2.8, "Feedwater System Pipe Breaks Inside and Outside Containment."