ML18136A177
| ML18136A177 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 11/09/1979 |
| From: | Stallings C VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | Harold Denton, Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| 811-092579, 811-92579, NUDOCS 7911140189 | |
| Download: ML18136A177 (9) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND,VIHGINIA 23261 November 9,.19 7 9 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation Attn:
Darrell G. Eisenhut Acting Director Division of Operating Reactors U. S. Nuclear Regulatory Commission Serial No.
811/092579 PO/FHT:baw Docket Nos: 50-280 50-281 License Nos: DPR-32 DPR-37
Subject:
Surry Power Station Units 1 and 2 Auxiliary Feedwater System Requirements
Dear Mr. Denton:
In response to your letter of September 25, 1979, on the above subject, we are forwarding our responses to your short-term and long-term requirements in the attachment.
The Auxiliary Feedwater System at Surry is as described in Enclosure 1 to your letter.
The information required to respond to Enclosure 2 of your letter, Basis for Auxiliary Feedwater System Flow Requirements, is being assembled at this time and will be forwarded as soon as it is available.
If you have any questions, or require additional information, please contact this office.
Attachment cc:
Mr. James P. O'Reilly Very truly yours, J, m. ~d1atu.r;.~J C. M. Stallings Vice President-Power Supply and Production Operations f
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e e
Surry Power Station Units 1 and 2 Auxiliary Feedwater System Requirements_
Attachment A.
Short-Term Recommendations
- 1. NRG POSITION Recommendation GS The licensee should propose modifications to the Tech-nical 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.
RESPONSE
A modification to the Technical Specifications to provide limited conditions of operation of the Auxiliary Feedwater System will be submitted.
This modi-fication will limit the time that one AFW system pump and its associated flow path and essential instrumentation can be inoperable.
The limits of the Stand-ard Technical Specifications will -be utilized.
The submittal will be made by January 1, 1980.
- 2. NRG POSITION Recommendation GS Emergency procedures for transferring to alternate 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:
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.
RESPONSE
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 alternate sources as the primary source is depleted.
These modifications will be made before January 1, 1980.
- 3. NRG POSITION Recommendation GS The as-built plant should be capable of providing the
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- I e e Attachment (cont'd).
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 co-0ling 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 station~d 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).
RESPONSE
a.)
Our primary water source provides sufficient water volume to insure we can supply 700 gpm 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.
No change is therefore required.
b.)
Procedure modifications will be made to give the operator guidance for controlli~g feed to the steam generators manually and.how the steam driven auxiliary feedwater pump can be *manually started and controlled if necessary.
This procedure modification will be accomplished prior to January 1, 1980.
c.)
Each of our Auxiliary Feedwater pumps is cooled by a flow path from its own discharge back to its suction, independent of any alternating current power. *Therefore, no change is necessary.
d.)
The requirement to station an operator or modify procedures in the event of the loss of all AC power to insure bearing cooling is also 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 will be in-corporated in the manual procedure as described *in Item b. above.
This will be accomplished prior to January 1, 1980.
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.
This change will be accomplished prior to Jan. 1, 1980 or as soon thereafter as equipment becomes available.
g.)
Sound power phone communication is already available in the area of the AFW pumps and discharge valves.
This circuit will be checked to be operable and head/hand sets provided to insure we have ready communi-cation with the Control Room should it be necessary.
This will be accomplished prior to January 1, 1980.
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e e Attachment (cont'd.)
We feel one general comment is necessary.
The probability of a total loss of all normal and emergency alternating current sources would seem very small.
Only a series of failures without operator action would allow a complete loss of AC power.
With the present capability to supply the affected unit's S/G's with auxiliary feedwater from the unaffected unit, it is extremely unlikely that we could deteriorate to having only steam driven auxiliary feedwater pumps available to both or either unit.
- 4. NRC POSITION Recommendation GS 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:
RESPONSE
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 ~icensee should propose Technical Specifications to assure that prior to plant startup following an extended cold shutdown, a flow test would be performed to verify the normal flow path from the pri-mary AFW system water source to the steam generators.
The flow test should be conducted with AFW system valves in their normal alignment.
a.)
The 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.
This modification will be accomplished prior to January 1, 1980.
b.)
Our present start-up procedure, OP-1. 4, provides
- for an actual flow verification of the Auxiliary Feedwater systems prior to taking the reactor critical.
A change to our Technical Specifications will be proposed to require the flow test to verify normal flow path for the primary AFW system water source to the steam generators prior to plant start-up following an extended cold shutdown.
This change will be submitted prior to January 1, 1980.
- 5. NRC POSITION 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 functional requirements listed below.
For the longer term, the automatic initiation signals and circuits should be upgraded to meet safety-grade requirements as indiciated in Recommendation GL-5.
RESPONSE
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e e Attachment (cont'd.)
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 system function.
Testability of the initiation signals and circuits shall be a feature of the design.
The initiation signals and circuits should be powered from the emergency buses.
Manual capability to initiate the auxiliary feedwater system from the control room should be retained and should be implemented so that a single failure in the manual circuits will not result in the loss of system function.
The alternating current motor-driven pumps and valves in the auxiliary feedwater system should be included in the automatic actuation (simul-taneously 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.
Our plant's present design has been verified and we have determined that the automatic start signals and associated circuitry are saf~ty-grade.
All of the concerns listed above are at the present time incorporated in the system design.
- 6. NRC POSITION Recommendation - Procedures should be established to lock open and periodically verify the open position of all manual AFWS valves inside containment.
RESPONSE
Our startup procedure (OP-lB) presently verifies the open position of all manual AFWS valves inside containment.
In addition, our checklist (CL-53) which is done periodically, checks the Auxiliary Feedwater.Pump Manual Discharge valves in the open position.
We will modify procedures and lock open the manual valves inside the containment.
This change will be accomplished prior to January 1, 1980 or as soon as operating conditions permit.
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- 7. NRC POSITION 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.
RESPONSE
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.
This change will be accomplished prior to February 1, 1980.
- 8. NRC POSITION Recommendation - Emergency procedures should be available to *the operators for operating the AFWS of one unit such that it is supplying water to the steam generator(s) of the opposite unit in the event that such an operating mode should be necessary.
RESPONSE
Emergency procedures w;i.11 be modified to give operational guidance to utilize the other unit's AFWS should this condition become necessary.
This change will be accomplished on or about January 1, 1980.
B. Additional Short-Term Recommendations
- 1. NRC POSITION Recommendation The licensee should provide redundant level indications and low level alarms in the control room for the AFW system primary water supply to allow the operator to anticipate the need to make up water or transfer to.an alternate water supply and prevent a low pump suction pressure condition from occurring.
The low level alarm setpoint should allow at least 20 minutes for operator action, assuming that the largest capacity AFW pump is operating.
RESPONSE
Our 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.
We also have a low level alarm, annunciated in the Control Room, which actuates at 87.3% level (96,000 gals.).
The present alarm point level alarms at the minimum T.S. Limit.
We will lower the setpoint to provide the operator with an annunciation when the tank level has decreased to where the remaining tankage still has at least 20 minutes operation for the highest volume pump.
This change will be accomplished by January 1, 1980.
A design change will be generated to install a redundant level indication.
The design will be completed by January 1, 1980, and will be installed as soon thereafter as practical.
e e Attachment (cont'd.)
- 2. NRC POSITION 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 include demonstrating that the pump~ remain within design limits with respect to bearing/bearing oil tem-peratures and vibration and that pump room ambient conditions (temperature, humidity) do not exceed environmental qualification limits for safety-related equipment in the room.
RESPONSE
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 temperatures, vibration and*the environmental qualification limits are not exceeded for safety-related equipment in the area.
The test will be prepared prior to Jan. 1, 1980 and completed as soon thereafter as practical.
- 3. NRC POSITION Recommendation -
The licensee should implement the following requirements as specified by Item 2.1. 7.b on page A-32 of NUREG-0578:
RESPONSE
"Safety-grade indication of auxiliary feedwater flow to each steam generator shall be provided in the control room.
The auxiliary feedwater flow instrument channels shall be powered from the emergency buses consistent with satisfying the emergency power diversity requirements for the auxiliary feedwater system set forth in Auxiliary Systems Branch Technical Position 10-1 of the Standard Review Plan, Section 10. 4.9."
As stated in the NUREG-0578 response, we presently have Auxiliary Feedwater Flow indication with its power being supplied from the emergency bus through a semi-vital bus.
This does not meet the diversity requirements of ASTB-10-1 of the standard review plan Section 10.4.9. To meet the diversity requirements of ASTB-10-1, the Auxiliary Feedwater flow indication power supplies will be moved to an existing cabinet which meets the diversity requirement.
Tµis change will be implemented prior to January 1, 1980.
- 4. NRC POSITION 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 opera-
e -
Attachment (cont'd.)
tion, 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 AFW system train from the test mode to its operational alignment.
RESPONSE
Our 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 communi-cation with the Control Room will be stationed at the manual valves and upon instruction from the Control Room, would re-align the AFW valves t9 their operational alignment.
To insure this, a precaution will be added to the Periodic Test Procedure prior to January 1, 1980.
C.
Long Term Recommendations
- 1. NRC POSITION Recommendation GL At least one AFW 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.
RESPONSE
Our present design has at least one AFW system pump and flow path automa-tically 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 buses 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 inde.pendently supplied from ultimate DC sources.
We will review possible design changes and. implement prior to January 1, 1981.
- 2. NRC POSITION Recommendation GL The licensee should upgrade the AFW system automatic initiation signals and circuits to meet safety-grade requirements.
RESPONSE
Our present design provides for automatic initiation signals and circuits meet safety-grade requirements.
Therefore, no further action is required.
e Attachment (cont'd.)
- 3. NRC POSITION 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 r~evaluated, including the possibility of relocating the valves outside containment, assuming an accident inside containment*
which necessitates AFWS operation and which creates a containment en-vironment (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 MOV's in a throttled position.
- b.
An AFWS line break downstream of the MOV's and failure of the MOV's to operate *.
RESPONSE
An AFWS design re-evaluation will be performed, including possibility of.
relocating the MOV's supplying water to the individual steam generators outside of the containment.
Also, the AFWS will be re-evaluated for a possible common mode failure causing spurious closure or failure of the MOV's in a throttled position or a line break downstream of the MOV's and failure of the MOV to operate.
This re-evaluation will be accomplished prior to January 1, 1981.
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