ML13333A455
| ML13333A455 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/15/1979 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | James Drake Southern California Edison Co |
| References | |
| TAC-44652, TASK-10, TASK-RR NUDOCS 7912200065 | |
| Download: ML13333A455 (31) | |
Text
Docket No.: 50-206 Mr. James H. Drake,.Vice-President Southern California Edison Company 2244 Walnut Grove Avenue 5 WUS P. 0. Box 800 Rosemead, California 91770
Dear Mr. Drake:
SUBJECT:
NRC REQUIREMENTS FOR AUXILIARY FEEDWATER SYSTEMS AT SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 1 The'purpose of this letter is to advise you of our requirements for the auxiliary feedwater systems at the subject facility. These requirements were identified during the course of the NRR Bulletins and Orders Task Force review of operating reactors in light of the accident at Three Mile Island, Unit 2.
Enclosure I to this letter identifies each of the requirements applicable to the subject facility. These requirements are of two types, (1) generic requirements applicable to most Westinghouse-designed operating plants, and (2) plant-specific requirements applicable only to the-subject facility. contains a generic request for additional information regarding auxiliary feedwater system flow requirements.
The designs and procedures of the subject facility should be evaluated against t.he applicable requirements specified in Enclosure 1 to determine the degree to which the facility currently conforms to these requirements. The results of this evaluation and an associated schedule and commitment for implementation of required changes or actions should be provided for NRC staff review within thirty days of receipt of this letter. Also, this schedule should indicate your date for submittal of information such as design changes, procedure changes or Technical Specification changes to be provided for staff review. You may also provide your response to the items in Enclosure 2 at that time.
In addition to the requirements identified in this letter, other requirements which may be applicable to the subject facility are expected to be generated by the Rulletins and Orders Task Force. Such requirements are those resulting from our review of the loss-of-feedwater event and the small break loss-of-coolant accident as described in the Westinghouse report WCAP-9600, "Report on Small 17912W0 BURNAME*...................................................
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Our specific concerns include systems reliability (other than the auxiliary feedwater system), analyses, guidelines and procedures for operators, and operator training.
We plan to identify, in separate correspondence, the requirements resulting from the additional items from the Bulletins and Orders Task Force review.
Sincerely, Original signed by Darrell G. Eisenhat Darrell G. Eisenhut, Acting Director Division of Operating Reactors Office of Nuclear Reactor Regulation
Enclosures:
As stated DIST:
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79 cc w/enclosures:
Charles R. Kocher, Assistant General Counsel Southern California Edison Company Post Office Box 800 Rosemead, California 91770 David R. Pigott Samuel B. Casey Chickering & Gregory Three Embarcadero Center Twenty-Third Floor San Francisco, California 94111 Jack E. Thomas Harry B. Stoehr Sart Diego Gas & Electric Company P. 0. Box 1831 San Diego, California 92112 U. S. Nuclear Regulatory Commission ATTN:
Robert J. Pate P. 0. Box 4167 San Clemente, California 92672 Mission Viejo Branch Library 24851 Chrisanta Drive Mission Viejo, California 92676
ENCLOSURE 1 X.13 (W)
SAN ONOFRE 1 AUXILIARY FEEDWATER SYSTEM X.13.1
System Description
X.13.1.1 Configuration, Overall Design A simplified diagram of the San Onofre Unit 1 Auxiliary Feedwater System (AFWS) is shown in Figure 1. Basically, the Auxiliary Feedwater System (AFWS) is a manually operated system which consists of two auxiliary feedwater pumps (AFP), one motor-driven pump whose capacity is 235 gpm at 1035 psi and one steam driven pump whose capacity is 300 gpm at 1110 psi.
Both pumps have common suction and discharge piping and valves.
Flow from the AFW pump can be directed to the three steam generators via two paths. The normal path is from the pumps to the main feed header through connections upstream and downstream of high pressure feed heater.
The second path is the emergency feedwater line which is a four-inch line which can be supplied by either AFP. This line branches into three three inch lines which join the main feed lines for each of the three steam generators between the main feedwater regulating valves (FRVs) and the main feed line containment penetrations. Normally closed isolation valves in the three-inch lines must be manually opened locally to supply feedwater through the emergency lines. Control of AFW flow through the normal path is by means of air-operated auxiliary feedwater regulating valves(AFRVs)
-2 which bypass the main FRVs. Another bypass line exists around each of the FRVs. This line has a two-inch manual valve which may be opened to allow feedwater to bypass a failed-closed FRV. The FRVs and AFRVs are air-operated and controlled from the control room. On loss of air, the FRVs fail open while the AFRVs fail closed. Portions of the main feedwater system are also used for safety injection; the main feed pumps are electric motor-driven and are safety-related and are powered from the emergency buses.
Isolation of failed portions of the AFW flow paths can be accomplished by manual valves.
If the motor-driven AFP fails due to electrical or mechanical problems, the turbine-driven AFP is available to provide the necessary steam generator makeup during a shutdown. The flow from the turbine-driven AFP (300 gpm) is sufficient to control and raise steam generator level about four minutes after a scram. The motor-driven auxiliary feedwater pump flow (235 gpm) is sufficient to control and raise steam generator level approximately seven to eight minutes after a reactor scram.
Both AFW pumps receive water via a four-inch line from the condenser make up and reject line, which is connected to the condensate storage tank (CST), with the CST being the primary source of water.
Sources of Water There are three sources of water for AFW System. The primary source is the Condensate Storage Tank (CST). This tank holds 240,000 gallons of
-3 which 15,000 gallons is dedicated to the AFW System. This will last for approximately three hours.
All valves to the AFWS are in the normally open position and are manually operated. This tank is not tornado missile protected.
The secondary source of water is the Primary Plant Make-up Tank (PPMT).
This tank holds 150,000 gallons of which a maximum of 105,000 gallons is reserved for the AFWS. The Technical Specifications require a total of 105,000 gallons be available either from this tank or the service water reservoir. The PPMT is not tornado missile protected. The licensee estimates that the 105,000 gallons will last approximately 39 hours4.513889e-4 days <br />0.0108 hours <br />6.448413e-5 weeks <br />1.48395e-5 months <br />. The licensee estimates that conservatively 30 minutes may be required to line up the system, since one manual valve must be opened and a primary plant make-up pump (one is normally operating at all times), is used to put water into the CST.
The back-up source and long term cooling is from the Service Water Reservoir through the service water and fire protection systems. This reservoir has a capacity of 3 million gallons of which 105,000 gallons is dedicated as stated above.
Portions of these systems, at least the pumps and some of the piping, are not tornado missile protected and would take about 30 minutes to line-up, since manual valves must be opened and a fire hose must be connected to the CST. Complete loss of water sources to the auxiliary feedwater system such as by extensive tornado damage to the CST would disable the AFWS; whereas, tornado damage to the service piping from the service water reservoir affects the availability of the long term supply of water for the AFW system.
-4 X.13.1.2 Components - Design and Classification Environmental Design Seismic Component Qualification Classification Category Motor-Driven Pump Ambient*
Safety Related 8
Steam-Driven Pump Ambient*
Safety Related B
AFWS Piping Safety Related B
Main Feed Piping Safety Related After main feed pumps AFWS Valves Ambient Safety Related B
MFWS Valves - After Ambient Safety Related MFW Pumps Condensate Storage Tank Ambient Safety Related A
Primary Plant Make-Up Ambient Non-Safety Related B
Tank Primary Plant Make-Up Ambient Non-Safety Related B
Tank Piping System Service Water Reservior Ambient Safety Related A
Service Water System Ambient Safety Related at Pumps Main Steam Piping Safety Related A
40-1040 F 100% Humidity Seismic Catetory A = Designed for SSE B = Designed for OBE C = Non seismic
-5 The system has been reviewed based on documents which are now available to the Staff for postulated breaks in high energy lines including the Main Steam, Main Feed and Auxiliary Feedwater Systems. As a result of the review, we conclude that for a break in the AFW System discharge piping with or without a single active failure, water can be supplied to the steam generator via the main feed pumps and the main feed system assuming these pumps are available and that there is no safety injection signal. A break in the main feed or main steamline outside containment may result in environmental conditions for which components in the main feed and AFWS have not been demonstrated to be operable. A break in the steam line to the turbine driven AFW pump at the pump may also result in local environmental condi tions for which main feed and AFWS components have not been demonstrated to be operable. In this latter case, one train of the main feedwater system would not be affected and would, therefore, remain available to provide feedwater to the steam generators provided there is no safety injection signal.
Based on the above, postulated breaks in the main steam and main feed lines may result in local environmental conditions which may disable conventional means to feed the steam generators and result in steam generators boiling dry.
In conjunction with high energy pipe breaks, the licensee states that in accordance with the criteria established by the NRC and previously approved by the NRC for San Onofre Unit 1, the licensee's analysis of pipe breaks outside containment did not postulate breaks in the annulus between the containment and the turbine building. However, in order to protect against the effects of cracks along pipes in this area, the main steam and main
-6 feedwater lines were enclosed in metal sleeves. The licensee stated that they consider that steam released from pipe cracks would, for the most part, condense on the sleeves and drip out the ends and any steam which did go out the ends would tend to rise to the open atmosphere. In view of these considerations. The licensee does not consider credible that the environment at the manual auxiliary feedwater valves located approximately 14 feet below the high energy lines would be such as to prevent an operator from opening the valves.
In the feedwater mezzanine area, in order to preclude breaks in the main steam and feedwater lines, an augmented ISI Program has been established.
However, breaks were postulated in smaller piping. In addition, cracks were postulated in all piping. To protect cable trays located below the high energy line from jet impingement from the breaks or cracks, the floor grating was replaced with a plate barrier. Although the cable trays penetrate the turbine building wall about 5 feet above the manual auxiliary feedwater valves, the licensee believes that steam is inhibited from passing through these pentrations by the plate barrier. Although steam could pass through penetraions at the elevation of the main steam and feedwater lines, the licensee considers that this steam would tend to rise to the open atmosphere. In the area of the manual auxiliary feedwater valves (about 14 feet below these lines) the licensee believes that the environment would not be so adverse as to prevent an operator from opening the valves.
See Section 13.3.3, Long Term Recommendations, and Section 13.3.4, Systematic Evaluation Program Considerations for recommendations relating to high energy pipe breaks.
-7 X.13.1.3 Power Sources The steam supply for the turbine-driven AFW pump is provided from the main steam header from a connection upstream of the main steam stop valves.
The turbine-driven AFW pump is started by local manual startup of the turbine. An air operated valve supplies steam to the turbine and takes power from D.C. Bus 1. On loss of air pressure this valve would fail closed. However, it can be opened manually to control the turbine locally.
The motor-driven pump can be started from the control room, the auxiliary control panel, or with the local operation of its breaker in the 480V switchgear room. The motor receives power from 480V switchgear bus #3. This bus can receive electrical power from both offsite and onsite sources. During a loss of offsite power, emergency diesel generator #1 supplies powertD switchgear bus #3 via 4160V bus lC after the electrical system has been realigned.
The main feedwater regulator motor-operated block valves take their power from the A-C buses and fail in the as-is position on loss of power. These valves can be manually operated locally.
Upon loss of all A-C power, the turbine pump will provide water to the steam generators via manually operated valves. The pump bearings will be cooled by gravity feed from the service water reservior.
-8 X.13.1.4 Instrumentation and Controls X.13.1.4.1Controls All controls for the system are local, manual controls except for the motor driven pump on-off control, the main feedwater regulating valves control and the auxiliary feedwater regulating valve control.
These controls are located locally as well as at the remote shutdown panel and the control room. The motor-operated block valves are controlled only locally or in the control room.
X.13.1.4.2Information Available to the Operator The following information is available to the operator in the control room.
- 2. CST and PPMT tank level indication
- 3. Steam Generator Level
- 4.
Steam Generator Low Level Alarms
- 5. Flow at feed flow control valves
- 6. Main steam pressure
- 7. Main Feed Line Pressure
- 8. Main Feed Flow Control Valve Position Indication
- 9. Electric AFW pump operation and ammeter
-9 The following information is available at the remote shutdown panel.
- 1. Steam canerator level indication.
- 2. Electric AFW pump operation All other information needed by the operator can be found at the local stations.
X.13.1.5 Initiating Signals for Automatic Operation Since the system is a manually initiated system this section is not appli cable, but manual initation is started on loss of main feed pumps and low steam generator level.
Subsequent to the staff review of the San Onofre 1 AFW system, the licensee completely revised his emergency operating instruc tions related to abnormal steam generator water level (including loss of main feed pumps) and steam generator high energy pipe break. These revised procedures identify plant symptoms and provide specific immediate and subsequent action requirements for the control room operator and the dedicated operator stationed at the redundant AFW system manually operated control valves to initiate AFW system operation.
X.13.1.6 Testing Both Auxiliary Feedwater Pumps are required to be tested bi-weekly, but the licensee states that they are presently being tested weekly in the recirculating mode of operation. The turbine-driven pump is tested every six months in an overspeed condition.
10 The feed control valves are used continuously for plant operation. All other normally closed valves are not tested except when in use.
The two diesel generators are tested monthly on a staggered bases.
X.13.1.7 Technical Specifications The Technical Specifications for the plant that are applicable to the Auxiliary Feedwater System are as follows:
TURBINE CYCLE Operating Status Applicability: Applies to the operating status of the turbine cycle.
Objective:
To define conditions of the turbine cycle necessary to ensure the capability to remove decay heat from the core.
Specification: The reactor shall not be pressurized above 500 psig unless the following conditions are met:
(1) A minimum turbine cycle steam-relieving capability of 5,706,000 lb/hr (except for resting of the main steam safety valves).
(2) Both auxiliary feedwater pumps operable, or the steam driven auxiliary feedwater pump is continuous operation when the residual decay heat levels are greater than the natural heat losses from the reactor coolant system.
11 (3) A minimum of 15,000 gallons of water in the condensate storage tank, and an additional 105,000 gallons in the service-water.-
eservoir and/or the primary plant makeup tank.
(4) System piping and valves directly associated with the above components operable.
After criticality is achieved, one auxiliary feedwater pump may be removed from service for maintenance for a period not to exceed 24 consecutive hours.
X.13.2 Reliability Evaluation X.13.2.1 Dominant Failure Modes The San Onofre auxiliary feedwater system was analyzed to determine the dominant failure modes under three transient conditions:
- a. LOFW with offsite power available
- b. LOFW with onsite power available
Results of the Anaysis are summarized below.
LOFW with Offsite Power Available Unavailability of the auxiliary feedwater system is dominated by the following:
12
- a. Operator failure to actuate system upon demand;
- b. Failure of the single manual valve in the supply line from the conden sate sto,'age tank.
The operator must recognize conditions requiring auxiliary feedwater, start the pumps (electric pump from the control room or turbine pump locally) and locally open the normally closed manual discharge valves.
Despite having a dedicated man at the local station, his actions are dependent upon instruction from the control room operator. The availability of the system is, thus, dependent upon the knowledge and actions of the control room operator.
Despite several sources of water, all water is drawn from the condensate storage tank through a single manual valve.
Should this valve fail closed, the system will be unavailable.
LOFW with Onsite Power Available The unavailability of the system is dominated by the same factors as the case discussed above. Postulating loss of one of the two diesel generators does not effect the dominant failure modes.
LOFW with Only DC Power Available Despite loss of all AC power, the turbine-driven pump train could continue to supply the necessary auxiliary feedwater. Sufficient cooling should be supplied by gravity feed to keep the pump bearings cool.
13 Short term system unavailability (.30 minutes) is dominated by the potential for maintenance being performed on the turbine driven pump and by the possibility of the discharge block valve inadvertantly being left closed following maintenance on the pump.
Long term unavailability (130 minutes) is dependent upon assuring that the steam admission valve remains open. This air operated valve will fail closed upon subsequent loss of air which is dependent upon AC power.
Manual action is required to open this valve or to provide an air supply after about 30 minutes when local air reservoirs could be depleted.
X.13.2.2 Dependencies One potential dependency was identified in the analysis. Both pumps of the auxiliary feedwater system are in a common location making them suscep tible to any locally adverse conditions such as high energy breaks or fires.
X.13.3 Recommendations for this Plant The short-term recommendations identified in this section represent actions to improve AFW system reliability that should be implemented by January 1, 1980, or as soon thereafter as is practicable. In general, they involve upgrading of Technical Specifications or establishing procedures to avoid or mitigate potential system or operator failures.
The long-term recommend ations identified in this section involve system design evaluations and/or modifications to improve AFW system reliability and represent actions that
14 should be implemented by January 1, 1981, or as soon thereafter as is practicable.
X.13.3.1 Short-Term
- 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 Specifications. See Recommendations GL-2 for the longer term resolution of this concern.
- 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 up 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,
15 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.
- 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.)
16
- 4. Recommendation GS The licensee should confirm flow path avail ability of an AFW system flow train that hat 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 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 vlaves in their normal alignment.
- 5. Recommendation GS The licensee should install a system to auto matically 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.
The design should provide for the automatic initiation of the auxiliary feedwater system flow.
e 0
17 The automatic initiation signals and circuits should be'designed so that a single failure will not results in the loss of auxiliary feedwater system function.
Testability of the initiating signals and circuits should be a feature of the design.
The initiating 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 (simultaneous and/or sequential) of the loads to the emergency buses.
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.
- 6.
Recommendation - The licensee should propose modifications to Technical Specifications so that manual valves that are normally closed will be tested periodically.
- 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
18 the present manual set-up as 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 5 above).
- 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.
X.13.3.2 Additional Short-Term Recommendations The following additional short-term recommendations resulted from the staff's Lessons Learned Task Force review and the Bulletins and Orders Task Force review of AFW systems at Babcock & Wilcox-designed operating plants subsequent to our review of the AFW system designs at W-and C-E-designed operating plants. They have not been examined for specific applicability to this facility.
- 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 trasnfer 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.
19
- 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-hour 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.
- 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."
- 4. Recommendation - Licensees with plants which require local manual realignment of valves to conduct periodic tests on the AFW system
20 train, and there is only one remaining AFW train available for opera 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 realign the valves in the AFW system train from the test mode to its operational alignment.
X.13.3.3 Long-Term Long-term recommendations for improving the system are as follows:
- 1.
Recommendation - GL-l -
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.
- 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 throughvavles in a single flow path, but the alternate AFW
21 system water supplies 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 openin-g 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.
- 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 current is acceptable.
- 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 I and tornado protection requirements.
22
- 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.
13.3.4 Systematic Evaluation Program Considerations The following items are still under review by the Systematic Evaluation Program (SEP) and supplement the above long term recommendations:
0 0
23
- 1. The San onofre Unit 1 plant, including the AFW System, will be reeval uated dur'ing 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.
- 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 Unit 1.
CONTAINMEI NT TYPICAL OF F FcI FROM PRiMARY PLANT MAKE-UP A
TANK & SERVICE WATER SYSTEM F
FO (FIRE PROTECTION LINES)
AS-IS FRV MAIN FEED SEE VALVING ABOVE CST M
N SEE VALVING MAIN FEED FEED HEATER LEGEND NORMALLY CLOSE NORMALLY OPEN TURB.
AIR OPERATED FC
- MOTOR OPERATED MAIN STEAM Auxiliary Feedwater System San Onofre 1 Figure 1
ENCLOSURE 2 Basis for Auxiliary Feedwater System Flovw Reauirements As a result of recent staff reviews of operating plant Auxiliary Feed water Systems (AFVS), the staff concludes that the design bases and criteria provided by licensees for establishing AFWS requirements for flow to the steam generator(s) to assure adequate removal of reactor decay heat are nqt well defined or documented.
We require that you provide the following'AFWS flow design basis infor mation as applicable to the design basis transients and accident con ditions for your plant.
- 1. a. Identify the plant transient and accident conditions considered in establishing AFWS flow requirements, including the following events:
- 1) Loss of Main Feed (LMFW)
- 2)
LMFW w/loss of offsite AC power
- 3) LMFW w/loss of onsite and offsite AC power
- 4) Plant cooldown
- 5) Turbine trip with and without bypass
- 6) Main steam isolation valve closure
- 7) Main feed line break
- 8) Main steam line break
- 9) Small break LOCA
- 10) Other transient or accident conditions not listed above
- b.
Describe the plant protection acceptance criteria and corres ponding technical bases used for each initiating event identi fied above.
The acceptance criteria should address plant limits such as:
-2
- Maximum RCS pressure (PORV or safety valve actuation)
- Fuel temperature or damage limits (ONS, PCT, maximum fuel central temperature)
- RCS cooling rate limit to avoid excessive coolant shrinkage
- Minimum steam generator level to assure sufficient steam generator heat transfer surface to remove decay heat and/or cool down the primary system.
- 2. Describe the analyses and assumptions and corresponding technical justification used with plant condition considered in l.a. above including:
- a. Maximum reactor power (including instrument error allowance) at the time of the initiating transient or accident.
- b. Time delay from initiating event to reactor trip.
- c. Plant parameter(s) which initiates AFWS flow and time delay between initiating event and introduction of AFS flow into steam generator(s).
- d. Minimum steam generator water level when initiating event occurs.
- e. Initial steam generator water inventory and depletion rate before and after AFWS flow commences - identify reactor decay heat rate used.
-3
- f.
Maximum pressure at which steam is released from steam generator(s) and against which the AFW pump must develop sufficient head.
- g. Minimum number of steam generators that must receive AFW flow; e.g. 1 out of 2?, 2 out of 4?
- h. RC flow condition - continued operation of RC pumps or natural circulation.
- i.
Maximum AFW inlet temperature.
- j. Following a postulated steam or feed line break, time delay assumed to isolate break and direct AFW flow to intact steam generator(s). AFW pump flow capacity allowance to accommodate the time delay and maintain minimum steam generator water level.
Also identify credit taken for primary system heat removal due to blowdown.
- k.
Volume and maximum temperature of water in main feed lines between steam generator(s) and AFWS connection to main feed line.
- 1. Operating condition of steam generator normal blowdowri following initiating event.
- m. Primary and secondary system water and metal sensible heat used for cooldown and AFW flow sizing.
- n. Time at hot standby and time to cooldown RCS to RHR system cut in temperature to size AFW water source inventory.
~ 0
- 3. Verify that the AFW pumps in your plant will supply the necessary flow to the steam generator(s) as deternined by items 1 and 2 above considering a single failure. Identify the margin in sizing the pump flow to allow for pump recirculation flow, seal leakage and pump wear.