ML13333A475
| ML13333A475 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 01/23/1980 |
| From: | Baskin K Southern California Edison Co |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| TASK-10, TASK-RR TAC-44652, NUDOCS 8001250514 | |
| Download: ML13333A475 (26) | |
Text
Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD. CALIFORNIA 91770 K. P. BASKIN T
9 ~)TELEPHONE MANAGER, NUCLEAR ENGINEERING (213) 5 72.1401 AND LICENSING Director, Office of Nuclear Reactor Regulation Attention: Mr. D. G. Eisenhut, Acting Director Division of Operating Reactors U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Gentlemen:
Subject:
Docket No. 50-206 NRC Requirements for Auxiliary Feedwater System San Onofre Nuclear Generating Station Unit 1 By letter dated November 15, 1979, you forwarded the NRC staff's evaluation of the Auxiliary Feedwater System (AFWS) at San Onofre Unit 1. Enclosure 1 to your letter set forth (1) generic requirements applicable to most Westinghouse-designed operating plants, and (2) plant-specific requirements applicable only to San Onofre Unit 1. You requested that we evaluate each of the requirements contained in Enclosure 1 with respect to the existing design and procedures for the San Onofre Unit 1 AFWS and advise you of the results of the evaluation, including associated schedules and commitments necessary to comply with the requirements.
Our January 2, 1980 letter advised you that additional time was required to provide our response to Enclosure 1 of your November 15, 1979 letter.
Accordingly, our responses to your Short-Term and Long Term Recommendations (as contained in Enclosure 1 to your November 15, 1979 letter) are provided as Enclosures 1 and 2 to this letter, respectively.
The organization of the enclosures corresponds to the enumeration of your recommendations.
If you have any questions, or desire additional information concerning this matter, please contact me.
A p
Very truly yours, Enclosures o1Ae CI, I
8001250 S
/
ENCLOSURE 1 Short Term RecommendationsSection X.13.3.1.1 Recommendation GS 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 valves in series that could interrupt all AFW 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 Specif cations.
See Recommendation GL-2 for the longer term resolution of this concern.
Response
Manual valves in the primary AFW system suction piping and the normal path from the AFW pumps to the main feedwater header that could interrupt all flow to the steam generators will be locked open and inspected monthly to assure proper system alignment.
Station Operating Instruction S-3-2.38, "Safety Related System Valve Alignment," has been revised to provide for the above inspection.
Station Order S-0-108, "Locking of Critical Valves,"
is currently being revised to require the appropriate valves to be locked open and will be implemented prior to resumption of power operation following the outage currently scheduled in January, 1980.
A proposed Technical Specification surveillance requirement incorporating the above monthly inspections is currently being prepared and reviewed in accordance with the Technical Specifications.
The proposed Technical Specification will be submitted shortly to allow NRC approval prior to resumption of power operation following the outage currently scheduled in January, 1980.
Upon implementation of the long term modifications, we will revise station procedures and propose additional Technical Specification surveillance requirements, as necessary, to meet the above recommendations.
-2 Section X.13.3.1.2. 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:
o 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, o
The case in which the primary water supply is being depleted.
The procedures for this case should provide for transfer to the alternate water sources prior to draining of the primary water supply.
Response
Station procedures for transferring to an alternate source of AFW to meet the above recommendations are currently in preparation and will be implemented prior to resumption of power operation following the outage currently scheduled in January, 1980.
-3 Section X.13.3.1.3 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 should 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.)
Response
Station procedures are currently being revised to manually initiate and control the AFW system flow for at least two hours from the steam driven AFW pump train following a complete loss of alternating current power.
These procedures will be implemented prior to resumption of power operation following the outage currently scheduled in January, 1980.
A two hour test of the steam driven AFW pump has been performed to determine its reliance on alternating current power for the bearing cooling water.
The test demonstrated that the pump can be operated continuously with bearing cooling water supplied by gravity feed from the station reservoir.
Therefore, emergency procedures to provide for an individual to be stationed at the steam-driven AFW pump in the event of loss of all alternating current power to monitor bearing/lube oil temperatures or to operate the pump in an on-off mode are not necessary.
Sufficient lighting powered by direct current sources currently exists within the station to allow access for initiation and control of the AFW system.
Radios are available to provide communication between local stations and the control room.
Section X.13.3.1.4 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:
o 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.
o The licensee 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 primary AFW system water source to the steam generators. The flow test should be conducted with AFW system valves in their normal alignment.
Response
Station Order S-A-133, "Safety Related Systems and Components Control", is being revised to meet the above recommendations. In addition, a proposed Technical Specification testing requirement incorporating the above recommendations is currently being prepared and reviewed in accordance with the Technical Specifi cations.
The procedure revisions will be implemented and the proposed Technical Specification will be submitted shortly to allow NRC approval prior to resumption of power operation following the outage currently scheduled in January, 1980.
-5 Section X.13.3.1.5 Recommendation GS The licensee should install a system to automatically initiate AFW system flow.
This system need not be safety-grade; however in the short-term, it should meet the criteria listed below, which are similar to Item 2.1.7a of NUREG-0578.
For the longer term, the automatic initiation signals and circuits should be upgraded to meet safety-grade requirements as indicated in Recommendation GL-1.
o The design should provide for the automatic initiation of the auxiliary feedwater system flow.
o 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.
o Testability of the initiating signals and circuits should be a feature of the design.
o The initiating signals and circuits should be powered from the emergency buses.
o Manual capability to initiate the auxiliary feedwater system should be included in the automatic actuation (simultaneous and/or sequential) of the loads to the emergency buses.
o The automatic initiation signals and circuits should be designed so that their failure will not result in the loss of manual capability to initiate the AFW system from the control room.
Response:.. to our November 21, 1979 letter provided the design details associated with implementing the above recommendations.
During numerous telephone conversations with members of the NRC staff, we provided clarification concerning the design details.
The clarification consisted of the following:
- 1.
Figure 2, Logic Diagram Auxiliary Feedwater Automatic Initiation, of Enclosure 1 to our November 21, 1979 letter incorrectly shows the new steam generator level transmitter signal conditioners (3) being supplied power from vital buses 1,2, and 3. These signal conditioners will actually be supplied power from vital bus 1 as are the new steam generator level transmitters shown in Figure 1, Block Diagram Auxiliary Feedwater Automatic Initiation, of Enclosure 1 to our November 21, 1979 letter.
- 2.
The existing flow control valves to be utilized for controlling flow to each steam generator will not be automated.
Only the motor driven AFW pump and its associated discharge valve will be provided with an automatic initiation signal.
The flow control valves can be remotely operated from the control room and this capability will be retained.
-6
- 3. to our November 21, 1979 letter indicates that the existing flow control valves to be utilized for controlling flow to each stean generator are closed on a Safety Injection signal and that the control circuitry will be modified to override this signal allowing renote manual operation of the flow control valves at all times.
Hbwever, further evaluation of this design concept indicates that the control circuitry cannot be modified in this manner since closure of the flow control valves on a Safety Injection signal is necessary for signal failtre protection.
In aidition, the control circuitry for the new motor operated valve to be installed in the path connecting the AFW punp header to the main feedwater line must be ndified to close on a Safety Injection signal for the sane reasn. Accordingly, if a Safety Injection signal should ccur simultaneously with a denand fbr AFW (i.e., low stean generator level), the electric driven AFW punp will be autanatically started and the Energency AFW flow path wll be utilized wLth flow controlled by the operator stationed at the manual AFW systen isolation valves, as required by IE Bulletin No.79-06A.
Since in excess of fifteen minutes is available to establish AFW flow prior to stean generator dry ott, sufficient time is available to manually establish AFW flow in this manner.
The design details discussed in our Novenber 21, 1979 letter, as clarified aove, will be conpleted prior to resunption of power operation following the outage currently scheduled in January, 1980.
However, as discussed in our January 16, 1980 letter, we will not activate the autanatio-start systen or adversely effect the manual-start systen urtil the NRC has canpleted their review and issued an approval of the information concerning the applicability of current analyses of a main steanline break or main feedwater line break assuming early initiation of auxiliary feedwater flow with a failure to limit flow to the affected stean generator as requested by the NRC letter dated Decenber 21, 1979.
Our January 16, 1980 letter indicated that the requested infornation would be subnitted by October 1, 1980.
Additionally, the NRC staff indicated during telephone conversations that the design details do not meet all of their requirenents.
Specifically, the NRC indicated that the following design details we also required:
- 1.
The stean driven AFW punp, including its stean side supply, must receive an autanatic initiation signal,
- 2.
The stean driven AFW punp, including its stean side supply, must be remote manually operable fron the control roan,
- 3.
The manual and autcnatic initiation signals and circuits must meet single failure criteria and must be physically independent fran each other, and 4;
The flow control valves must receive an autanatic initiation signal.
The NRC staff also requested drawings showing the autanatic and manual AFW systen initiation circuitry and the stean generator level/channel actuation circuitry.
These drawings are provided as Appendix 1 to this Enclosure.
The NRC was aivised during the telephone conversations that the design details discussed in our November 21, 1979 letter, as clarified above, provide an increased capability in the time frane established by the NRC and that it is our intention to meet the above requirenents in the long term following canpletion of the integrated assessment of potential nodifications identified by review of station design aid operation in connection with the Systenatic Evaluaticn Progran.
-7 Section X.13.3.1.6 Recommendation -
The licensee should propose modifications to Technical Specifications so that manual valves that are normally closed will be tested periodically.
Response
As discussed in our response to Recommendation GS-2 above, all manual valves in the primary AFW system suction piping and the normal path from the AFW pumps to the main feedwater header that could interrupt all flow to the steam generators will be locked open. However, normally closed manual valves do exist in the alternate AFW system suction line and the emergency AFW flow path from the AFW pumps to the steam generator feedwater lines.
Therefore, a proposed Technical Specification requiring that closed manual valves in the alternate AFW system suction line and the emergency AFW flow paths be tested every 18 months is currently being prepared and reviewed in accordance with the Technical Specifications. The proposed Technical Specification will be submitted shortly to allow NRC approval prior to resumption of power operation following the outage currently scheduled in January, 1980.
-8 Section X.13.3.1.7 Recommendation - The licensee should install valve operators that can be controlled from the control room on all the normally closed manual discharge valves.
This will reduce the time delay inherent in the present manual set-up discussed in Section 13.2.1.
The AFW system could then be operated from the control room until the system has been fully automated.
(See Recommendation GS-8 above).
Response
As discussed in response to Recommendation GS-8, station modifications being implemented prior to resumption of power operation following the outage currently scheduled in January, 1980 will provide automatic start of the motor driven AFW pump and opening of its associated discharge valve, except if a Safety Injection signal occurs. These modifications, in conjunction with remote manual operation from the control room of the steam generator main feedwater and AFW flow control valves, except if a Safety Injection signal occurs, will reduce the time delay inherent in the present manual set-up. Additionally, as discussed in response to Recommendation GS-8, if a Safety Injection signal occurs simultaneously with a demand for AFW, the electric AFW pump will be started automatically and AFW flow will be controlled by the operator stationed at the AFW system isolation valves.
The time delay inherent in the present manual setup will also be
.reduced in this case.
Therefore, separate modifications in accordance with this recommendation are not necessary.
0 9
-9 Section X.13.3.1.8 Recommendation -
To reduce dependence on a single flow path from the water sources and increase the quantity of water reserved and readily available for the AFW system, the licensee should connect temporary piping or a fire hose from the Service Water Reservoir/
fire protection system directly to the AFWS pump suction header.
Response
A temporary fire hose from the Service Water Reservoir/fire protection system directly to the AFWS pump suction header, with appropriate valves, will be installed prior to resumption of power operation following the outage currently scheduled in January, 1980.
-10 Section X.13.3.2.1 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
An additional condensate storage tank level indicator and low level alarm will be installed to supplement the level indicator and alarm already existing in the control room. The new level indicator and alarm will be installed prior to resumption of power operation following the outage currently scheduled in January, 1980.
The low level alarm setpoint will meet the criteria established in the above recommendation.
Section X.13.3.2.2 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 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> pump run, the pumps should be shutdown 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.
Response
Station procedure SPO-11 has been developed to establish test acceptance criteria for bearing temperatures and vibration during 72-hour endurance tests of the steam and electric driven-AFW pumps. A successful test of the steam-driven AFW pump has been completed as discussed in our letter dated January 10, 1980, to the NRC, Region V.
Our letter notified the NRC, Region V, that during an initial test attempt, a bearing failure (not associated with the bearing cooling water), apparently caused by an inoperative oil leveler, resulted in removal of the steam-driven AFW pump from service for repair. Following the repair, the endurance test was reinitiated and completed successfully. Following the 72-hour endurance test, the pump was shut down and cooled down and then restarted and run successfully for an additional hour.
Similar endurance testing of the electric-driven AFW pump will be completed prior to resumption of power operation following the outage currently scheduled in January, 1980.
The AFW pumps are located in an open area under the west feedwater heater deck. The exhaust from the steam-driven AFW pump is piped to a remote outside location. Thus, ambient conditions (tempera ture, humidity) resulting from AFW pump operation do not exceed environmental qualification limits for safety related equipment.
-12 Section X.13.3.2.3 Recommendation -
The licensee should implement the following requirements as specified by Item 2.1.7.b on page A-32 of NUREG-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 emergency power diversity requirements for the auxiliary feedwater system set forth in the Auxiliary Systems Branch Technical Position 10-1 of the Standard Review Plan, Section 10.4.9."
Response
Our letter dated October 17, 1979 indicated our plans to implement the above recommendations and our November 21, 1979 letter provided the design details associated with providing auxiliary feedwater flow indication in the control room.
As indicated in our November 21, 1979 letter, the auxiliary feedwater flow indication will be completed prior to resumption of power operation following the outage currently scheduled in January, 1980.
-13 Section X.13.3.2.4 Recommendation -
Licensees with plants which require local manual realignment of valves to conduct periodic tests on the 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 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.
Response
Auxiliary feedwater pump testing will be performed such that local manual realignment will not be required. Thus, a Technical Specification which provides for a dedicated auxiliary feedwater system operator is not necessary.
Appendix 1
ENCLOSURE 2 Long Term RecommendationsSection X.13.3.3.1 Recommendation GL Licensees with plants having a manual starting AFW system, should install a system to automatically initiate the AFW system flow. This system and associated automatic initiation signals should be designed and installed to meet safety-grade requirements. Manual AFW system start and control capability should be retained with manual start serving as backup to automatic AFW system initiation.
Response
Our October 17, 1979 and November 21, 1979 letters indicated our plans to implement these recommendations. The completion of the required modifications, however, have been deferred pending completion of the integrated assessment of potential modifications identified by review of station design and operation in connection with the Systematic Evaluation Program.
-2 Section X.13.3.3.2 Recommendation GL 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 supply is connected 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 of 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.
Response
AFW system modifications will be implemented and a proposed Technical Specification will be submitted to meet the above recommendations.
However, implementation of these recommendations has been deferred pending completion of the integrated assessment of potential modifications identified by review of station design and operation in connection with the Systematic Evaluation Program.
-3 Section X.13.3.3.3 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 currrent is acceptable.
Response
The AFW system in its current configuration, and as it will be following implementation of the long term modifications, can be supplied from either offsite power or the emergency diesel generators. Energizing the electrical buses following a loss of power is a manual action from the Control Room (unless loss of power is coincident with safety injection, in which case the buses are automatically energized); however, once the electrical buses have been energized, operation of the AFW system, if required, will be automatic/remote manual following implementation of the short term modifications discussed in response to Section X.13.3.1.5. Recommendation GS-8 of Enclosure 1 to this letter and totally automatic following implementation of the long term modifications discussed in this Enclosure 2. Since in excess of fifteen minutes is available to establish AFW flow and the water inventory and flow capabilities of the AFW system are adequate to cope with accidents and transients analyzed in the Final Safety Analysis Report, manually energizing of the electrical buses is acceptable and the recommended modifications are not considered necessary.
In addition, Enclosure 2 to the NRC November 15, 1979 letter contained a generic request for additional information regarding the Auxiliary Feedwater System flow requirements and the NRC December 21, 1979 letter requested additional information concerning the applicability of current analyses of a main steam line break or main feedwater line break assuming early initiation of auxiliary feedwater flow with a failure to limit flow to the affected steam generator. As part of these analyses, the available time to establish auxiliary feedwater flow will be reviewed, and if necessary, the need to implement the above recommendation will be reconsidered.
Section X.13.3.3.4 Recommendation GL 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 1 and tornado protection requirements.
Response
The above recommendation will be addressed during review of station design and operation in connection with the Systematic Evaluation Program.
Any necessary modifications will be deferred pending completion of the integrated assessment.of potential modifications identified by the review of station design and operation in connection with the Systematic Evaluation Program.
-5 Section X.13.3.3.5 Recommendation -
The licensee should evaluate the following concerns:
a)
A break in the main feed or main steamline outside containment or a break in the steamline to the turbine driven AFW pump may result in environmental conditions for which the main feed and AFW system components are not qualified.
b)
The San Onofre Unit 1 AFW system design does not meet the high energy line break criteria in SRP 10.4.9 and Branch Technical Position 10-1; namely, that the AFW system should maintain the capability to supply the required AFW flow to the steam generator(s) assuming a pipe break anywhere in the AFW pump discharge lines concurrent with a single active failure.
The licensee should evaluate the postulated pipe breaks stated above and (1) determine any AFW and main feedwater system design changes including environmental qualification, or procedures necessary to detect and isolate the break and direct the required feedwater flow to the steam generator(s) before they boil dry or (2) describe how the plant can be brought to a safe shutdown condition by use of other systems which would be available following such postulated events.
Response
The above recommendation will be addressed during review of station design and operation in connection with the Systematic Evaluation Program. Any necessary modifications will be deferred pending completion of the integrated assessment of potential modifications identified by the review of station design and operation in connection with the Systematic Evaluation Program.
-6 X.13.3.4.1.
The San Onofre Unit 1 plant, including the AFW system, will be reevaluated during the SEP with regard to internally and externally generated missiles, pipe whip and jet impingement including main steam and main. feed line breaks inside and outside containment, quality and seismic design requirements, and the effects of earthquakes, tornadoes and floods.
Response
None required.
-7 X.13.3.4.2. The San Onofre Unit 1 AFW System is not automatically initiated and the design does not have capability to automatically terminate AFW flow to a depressurized steam generator and provide flow to the intact steam generator in the event of a main steam or main feed line break. The effect of this design will be assessed in the design basis event evaluations for San Onofre Uniti.
Response
None required.