ML18139A594
| ML18139A594 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Surry |
| Issue date: | 10/01/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML093450149 | List:
|
| References | |
| FOIA-80-515, FOIA-80-555 NUDOCS 8010170303 | |
| Download: ML18139A594 (17) | |
Text
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SAFETY EVALUATION REPORT SURRY, UNITS 1 AND 2 IMPLEMENTATIONS OF RECOMMENDATIONS AUXILIARY FEEDWATER SYSTEMS I.
Introduction and Background FOR The Three Mile Island Unit 2 (TMI-2} accident and subsequent investigations and studies highlighted the importance of the Auxiliary Feedwater System (AF\\~S) in the mitigation of transients and accidents.
As part of our assessment of the TMI-2 accident and related implications for operating plants, we evaluated the AFW systems for all operating plants having nu.clear steam supply. systems (NSSS) designed by Westinghouse (NUREG-0611) or Combustion Engineering (NUREG-0635).
Our evaluations of these system designs are contained in the above NUREGs along with our recommendations for each plant and the concerns which led to each recommendation.
The objectives of the evaluation were to:
(1) identify necessary changes in AFW system design or related procedures at the operating facilities in order to assure the continuance of the safe operation of these pl ants and (2) to identify other system characteristics of the AFW system which, on a long term basis, may require system modifications.
(1)
Reviewed plant specific AFW system designs in light of current regulatory requirements (SRP) and, (2) Assessed the relative reliability of the various AFW 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 poten-tial for AFW system failure due to common causes, single point vulner-abilities, and human error.
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e e We concluded that the implementation of the recommendations identified during this review will considerably improve the reliability of the AFW systems for each operating plant.
The following plant specific recommendations did not apply to this plant:
GS-2, GS-3, GS-8 and GL-1, GL-2, GL-4.
The basis for these recommendations can be found in Appendix III of NUREG-0611 and the system description which determined the basis for not applying these recommendations can be found in Section X of NUREG-0611.
II. Implementation of Our Recommendations A.
Short Term Recommendations
- 1.
Recommendation GS 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 the 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.
The licensee responded by letter dated November 9, 1979, and stated that a modification to the Technical Specifications to provide limited conditions of operation of the Auxiliary Feedwater System will be submitted. This modification will limit the time that one AFW system pump and its associated flow path and essential instrumentation can be inoperable.
The limits of the Standard Technical Specifications will be utilized.
l
- We conclude that the licensee's commitment to provide the requested Technical Specification is acceptable pe.nding receipt of the actual.
proposed Technical Specification.
- 2.
Recommendation GS Emergency procedures for transferring to alter-nate sources 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:
(1)
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, (2)
The case in which the primary water supply*is b~ing depleted.
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The. procedure for this case should pro vi de for ttansfer to the alternate water sources prior to draining o.f the primary water supply.
The licensee responded by letter dated November 9, 1979, and stated that procedure modifications will be made to provide operators with guidance to diagnose availability of the primary water supply and protect the AFW system pumps against self-damage before water flow is
. initiated. The procedure will also provide a prioritized list of alternate water sources and define when and how to shift to the alter-nate sources as the primary source is depleted.
We find the licen~ee 1s response acceptable pending verification by the Office of Inspection and Enforcement.
e 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 condi-tions. 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 provided if manual initiation and control of the AFW system is needed.
(See Recommendation GL-3 for the longer-term resolution of this concern.)
The licens*ee's response by letter dated November 9, 1979, stated the fol lowing:
- a.
The primary water source provides sufficient water volume to
- insure that 700 gpm can be supplied for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, independent of any alternating current power source.
e b.
Procedure modifications were made to give the operator guidance for controlling feed to the steam generators manually and how the steam driven auxiliary feedwater pump can be manually started and controlled if necessary.
- c.
Each of the Auxiliary Feedwater pumps is cooled by a flow path from its own discharge back to its suction, independent of any alternating current power.
- d.
The requirement to station an operator at the turbine-driven pump or modify procedures for operating in the event of the loss of all AC power to insure bearing cooling is considered unnecessary, as the cooling water is provided by the individual pump.
- e.
The concern for the operator to operate the turbine-driven AFW pump in an on-off mode until alternating power is restored was incorporated in the manual procedure as described in Item b.
above.
- f.
Emergency (D.C.) lighting will be provided to give sufficient lighting to manually control the turbine-driven AFW pump and manually control pump discharge valves.
- g.
Sound power phone communication is already available in the area of the AR-J pumps and discharge valves. This circuit will be checked to be operable and head/hand sets provided to insure ready communication with the Control Room should it be necessary.
e e The licensee 1s response to this recommendation is acceptable.
We conclude that the changes that have been made fully meet this recommendation.
- 4.
Recommendation GS The licensee should confirm flow path avail-ability 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 Specifications to assure that prior to plant startup following an extended cold shut-down, a flow ~est 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 conducted with AFW system valves in their normal alignment.
The licensee 1s response to this recommendation by letter dated November 9, 1979, states the following:
- a.
A periodic test (PT-15} for testing the operability of the auxiliary feedwater pumps will be modified to provide for a second operator to verify that the valves manipulated as part of the test are in proper alignment following the completion of the test.
e e b.
Start-up procedure, OP-1.4, provides for an actual flow verifi-cation of the Auxiliary Feedwater Systems prior to taking the reactor critical. A change to the Technical Specifications will be proposed to require the flow test to verify normal flow path for the primary AFW system water source to the stt~am generators prior to plant start-up following an extended cold shutdown.
The licensee 1s commitment to this recommendation is acceptable pending receipt of proposed Technical Soecification.
- 5.
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 automatic initiation system should be modified in the short term to meet the function require-ments 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 aux*:liary feedwater system flow.
- The autc,matic 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 cir~uits 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 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 (simultaneously and/or sequentially) 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.
The licensee resporided by letter dated November 9, 1979, stating that the plant 1 s pres.ent design has been verified and determined that the automatic start signals and associated circuitry are safety-grade.
All of the concerns listed above are at the present time incorporated in the system design.
We conclude that this response satisfies the control grade ri'!quire-ments and is, therefore, acceptable.
Refer to GL-5 for long term safety grade implementation of this i tern.
- 6.
NRC Recommendation - Procedures should be established to lock open and periodically verify the open position of all manual AFWS valves inside containment.
The licensee responded by letter dated November 9, 1979, stating that startup procedure (OP-18) presently verifies the open position of all manual AFWS valves inside containment.
In addition, checklist (CL-53) which is done periodically, checks the Auxiliary Feedwater Pump Manual Discharge valves in the open position. Procedures will be modified to lock open the manual valves inside the containment.
The licensee's response to this recommendation is acceptable pending verification by the Office of Inspection and Enforcement.
- 7.
NRC Recommendation - The licensee should require staggering of the periodic pump train tests (e.g., one train at North Anna is tested every 10 days rather than all three trains tested at once on a monthly basis). This reduces the potential for inadvertently leaving closed the discharge valves of all trains after test.
The licensee's response by letter dated November 9, 1979, stated the fo 11 owing:
Our periodic testing will be staggered to test the motor driven and steam driven *auxiliary feedwater pumps at different times to reduce the potential for inadvertently leaving closed the discharge valves of all trains after a test.
The licensee's response to this recommendation is considered acceptable.
- 8.
NRC Recommendation - Emergency procedures should be available to the operators for operating the AFWS of one unit such that it can supply
e water to the steam generator(s) of the opposite unit in the event that such an operating mode should be necessary.
The licensee's response by letter dated November 9, 1979, stated that emergency procedures will be modified to give operational guidance to utilize the other unit's AFWS should this condition become necessary.
The licensee's commitment to this recommendation is acceptable.
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 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.
The licensee's response by letter dated November 9, 1979, stated that the present design provides for a recorded level for the primary water source (l-CN-TK-1) in the Control Room and a redundant local level indicator. A low level alarm, annunciated in the Control Room, which actuates at 87.3% level (96,000 gals.) is also available.
The present alarm point level alarms at the minimum T.S. Limit.
The set-point will be lowered to provide the operator with an annunciation when the tank level has decreased to where the remaining tankage still
e has at least 20 minutes operation for the highest volume pump.
A design change will be generated to install a redundant level indica-tion. This response is acceptable.
- 2.
NRC Recommendation - 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 focl ude demonstrating that the pumps remain within design 1 imi ts 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's response by letter dated November 9, 1979, stated the following:
A special test will be performed to subject the AFW pumps to a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> endurance test to demonstrate that the pump remains within design limits with respect to bearing/bearing oil tempera-tures, vibration and the environmental qualification limits are not exceeded for safety-related equipment in the area.
Subsequent to the issuance of the original recommendation it was revised reducing the endurance test from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.
The licensee committed to follow the provisions of the revised AFW pump endurance test provisions and submit the requested test information.
The revised pump test results ~ithout the turbine driven pump was provided by letter dated February 8, 1980.
The motor driven pump tests were satisfactorily performed.
- 3.
NRC Recommendation - The licensee should implement the following require-ments as specified by ltem.2.1.7.b on page A-32 of NUREG-0578:
11Safety-grade i ndi cation of auxiliary feedwater fl ow 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 th~ emergency 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.
11 The licensee 1s response by letter dated November 9, 1979, states the following:
As stated in the NUREG-0578 response, Auxiliary Feedwater Flow indication is presently available with its power being supplied from the emergency bus through a semi-vital bus.
This does not meet the diversity requirements of ASTP-10-1 of the Standard Review Plan Section 10.4.9.
To meet the diversity requirements of ASTP-10-1, the Auxiliary Feedwater flow indication power supplies have been moved to an existing cabinet which meets the diversity requirement.
We conclude that this response satisfies the control grade require-ments specified in the NUREG~0578 position and, therefore, is acceptable.
The safety grade requirements for this recommendation are still under review.
Our evaluation of this matter will be con-tained in a supplement to this SER.
- 4.
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 AFW train available for operation, should propose Technical Specifications to provide that a dedicated individual who is in communication with the control room be stationed at the manual valves.
Upon instruction from the control room, this operator would re-align the valves in the AHi system train from the test mode to its operational alignment.
The licensee's response by letter dated November 9, 1979, stated that the plant does require local manual realignment of valves to conduct periodic tests on the AFW system.
In the event that a periodic test is performed with only one AFW system train available, a dedicated individual who is in communication with the control room will be stationed at the manual valves and upon instruction from the control room, would re-align the AFW valves tn their operational alignment.
To insure this, a precaution was added to the Periodic Test Procedure.
W~ conclude that the licensee's response to this recommendation is acceptable.
C.
Long Term Recommenda ti ans
- 1.
NRC Recommendation GL At least one AFW sys_tem 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.
The licensee responded by letter dated November 9, 1979, stating that the present design has at least one AFW system pump and flow path automatically initiated and capable of being operated independently of any alternating current power source for at least two hours.
The essential instrumentation (Auxiliary Feedwater Flow Indication) must be modified to provide for loss of all AC power.
The present vital bu_ses are powered such that two are AC supplied via sola transformers and two are DC supplied via invertors. Therefore, at present only two indicators can be independently supplied from alternate DC sources.
Design changes will be reviewed and implemented prior to January 1, 1981.
We advised the licensee by letter dated February 8, 1980, that its response to this recommendation is not clear.
From the licensee's response to GS-5 above it appears that operator action outside the control room is required following a loss of all AC power. It also appears that the turbine driven pump may have to be operated in an on-off mode for AFW control.
In the long term we require that following a complete loss of AC power no operator action should be necessary outside the control room for at least two hours.
The licensee should also verify that on-off control of the turbine can be accomplished from the control room without AC power. It is requested that the licensee commit to meeting these requirements in addition to the instrumentation modifications discussed in his response in the long term.
The licensee has not responded to our letter of February 8, 1980.
We will report our evaluation of this matter in a supplement to this SER.
- 2.
NRC Recommendation GL The licensee should upgrade the AFW system automatic initiation signals. and circuits to meet safety-grade require-ments.
Th~ licensee responded by letter dated November 9, 1979, that the present design provides for automatic initiation signals and circuits which meet safety-grade requirements.
We will review the licensee 1 s design in detail and our evaluation will be contained in a supplement to this SER.
- 3.
NRC Recommendation - The AFWS flow control valves for both the motor and turbine pump trains are AC powered, normally open, fail-as-is motor operated valves which are located inside containment. Also, manual normally open valves are located inside containment. The AFWS design should be reevaluated, including the possibility of relocating the valves outside containment, assuming an accident inside contain-ment which necessitates AFWS operation and which creates a containment environment (humidity, radiation) that precludes access to the valves.
The reevaluation should consider the following:
- a. A possible common mode failure (environmentally induced} causing spurious closure or failure of the MOVs in a throttled position.
- b.
An AFWS line break downstream of the MOVs and failure of the MOVs to operate.
The licensee responded by letter dated November 9, 1979, stating the fa 1 lowing:
An AFWS design re-evaluation will be performed, including possibility of relocating the MOVs supplying water to the individual steam generators outside of the containment. Also, the AFWS will be re-evaluated for a possible corrnnon mode failure causing spurious closure or failure of the MOVs in a throttled position or a line break downstream of the MOVs and failure of the MOV to operate. This re-evaluation will be accomplished prior to January 1, 1981.
The staff accepts the licensee's response in that the licensee has committed to performing the design re-evaluation requested in this recommendation.
We will review the results of the re-evaluation when they are submitted and if they are not acceptable, we will require
- modifications and provide a safety evaluation regarding the re-evalua-tion and modifications.
D.
Basis for AFW System Flow Regui rements The licensee should provide a commitment date for responding to the infor-mation requested in Enclosure 2 of the NRC letter dated September 25, 1979.
We will provide our evaluation of this matter in a supplement to this SER.
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