ML19350E465
| ML19350E465 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 06/15/1981 |
| From: | Kay J YANKEE ATOMIC ELECTRIC CO. |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| FYR-81-90, GL-81-12, NUDOCS 8106230121 | |
| Download: ML19350E465 (15) | |
Text
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YANKEE ATOMIC ELECTRIC COMPMiY
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1671 Worcester Road, framingham, Massachusetts 01701 yyg 81-90 YAuxse m
June 15, 1981 United States Nuclear Regulatory Commission Washington, D. C.
20555 Attention:
Mr. Darrell G. Eisenhut, Director Division of Licensing
References:
(a) License No. DPR-3 (Docket No. 50-29)
(h) USNRC Letter to YAEC dated Februsry 20, 1981 (Generic Letter 81-12)
(c) YAEC Letter to USNRC dated March 19, 1981, FYR 81-43 (d) YAEC Letter to USNRC dated March 11, 1980, WYR 80-34
Subject:
Additional Infomation on Alternative Safe Shutdown System Proposal
Dear Sir:
Enclosures I and II have been prepared to provide the additional information on our Alternative Safe Shutdown System ( ASSS) as requested in Reference (b).
In Reference (c), the schedule for implementing this design change was discussed. We would like to point out again the need for a timely review and approval in order to meet the 1982 refueling outage. NRC approval is needed as soon as possible since engineering must begin in July to support equipment procurement for the 1982 refueling outage.
We trust this information will be satisfactory; however, if you have any questions, please contact us.
Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY J. A. Kay Senior Engineer - icensing JAK/abm y
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Generic Letter 81-12, dated February:20, 1981 ENCLOSURE 1 SECTION 8: 'Information Required for Staf f Review -
Item (a)
Description of the systems or portions thereof used to provide the shutdown capability and modifications required to achieve the alternate shutdown capability if required.
-Response:
Attachment A to the March 19, 1981 submittal by YAEC to the NRC, letter No. FYR 81-43, supplied the information requested. The design basis for the ASSS is a single exposure fire in the turbine building. This event requires the control room operator to transfer operation and control of
. the plant to a remote location (ASSS console) powered from an emergency power supply and to disconnect the plant from of f-sit ac power.
In formulating this design basis, we have concluded that no single exposure This conclusion fire directly results in a loss of all off-site ac power.
is based on the high reliability of the off-site ac power system and 20 years of operating experience. In those 20 years,.the plant has experienced which have caused a loss of both or either off-105 plant trips, none o site power aupply. Furthermore, the plant has experienced only one loss of ac power, during the " Northeast Blackout" of 1965, and only 8 losses of one of the two off-site power linet-. This information was previously sent to you by Reference (d).
Item (b)
System design by drawings which show normal and alternate shutdown control and power circuits, location of components, and that wiring which is in the area aad the wiring which is out of the area that required the alternate system.
Response
Figure 1, Alternative Safe Shutdown System Layout, shows the general location of the major components required for the Alternative Safe Shutdown System (ASSS). The fire area which required the ASSS consists of the turbine building, control room and switchgear room, all of which are shown on Figure 1.
Table 1 is a compilation of all of the components that are required for safe shutdown and their location. Table 2 is a compilation of all of the instrumentation required for safe shutdown and their location.
Figure 2 is a typical circuit diagram for the equipment compiled in Table This figure underlines the design philosophy being utilized in the design 1.of the ASSS. By using transfer switches located in the new ASSS room, all n-of'the equipment and cables located in the fire area are isolated from the ASSS so that their damage or loss in the fire will not ha"e any affect on the operation of the equipment required for safe shutdown and cooldown.
The same transfer switches will connect alternate power and control circuits, not affected by the fire, to the ASSS equipment to assure its operation.
Item (c)
Demonstrate that changes' to safety systems will not degrade safety systems, (e.g., new isolation switches and control switches should meet design criteria and standards in FSAR for_ electrical equipment in the system that the switch is to be installed;1 cabinets that the switches are to be mounted in should also meet the same criteria-(FSAR) as other safety-related cabinets and panels; to avoid inadvertent isolation from the control room, the isolation switches should be keylocked, or alarmed in the control room if in the '" local" or " isolated" position; periodic checks should be made to verify switch is in the proper position for normal operation; and a single transfer switch or other new device should not be a source for a single failure to cause loss of redundant safety systems).
Response
All of the new electrical components that interface with existing Safety Class components will be designed and specified to equal or better criteria as the existing components.
The features which are planned to avoid inadvertent isolation from the control room of the operation of this equipment will include classifying the new ASSS room as a security area with controlled and restricted access, keylocking the transfer switches, and performing periodic checks of the ASSS room to verify that the transfer switches are in the proper position for normal operation.
Item (d)
Demonstrate that wiring, including power sources for the control circuit and equipment operation for the alternate shutdown method, is independent of equipment wiring in the area co be avoided.
Re sponse:
As discussed in the response to Item (b), the design philosophy being utilized here uses transfer switches which disconnect all of the equipment and wiring in the fire area so that their damage by fire will not affect the aperation of the necessary equipment. The power sources for the equipment will consist of the existing site Nos. 2 and 3 diesel generators and their associated busses, along with a new motor control center for the ASSS equipment (see Figure 3).
The control circuits will be powered from the existing site No. 3 battery and battery charger which are powered from
.No. 3 diesel, and a new inverter and vital bus. The new control circuitry for the power sources will be isolated from th. ' in the fire area by utilizing transfer switches as discussed above. The busses will be isolated l
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by manually tripping the breaker in the fire area and the series breaker
.at the diesel busses.-
Item (e)
Demonstrate that alternate shutdown power sources, including all breakers, have isolation devices on control circuits that are routed through the area-
-to be avoided, even if the breaker is to be operated manually.
Re sponse :
The control circuits located in the fire area for the alternate shutdown Power sources required for the ASSS are isolated by means of transfer switches (see Figure 3, note 5).
Item (f)
Demonstrate that licensee procedure (s) have been developed which describe the tasks to be performed to effect the shutdown method. A sumnary of these procedures should be submitted.
Response
Procedures will be prepared following the completion of the engineering design when all aspects of the design have been formalized and approved by the NRC.
Item (g)
De.tonstrate that spare fuses are available for control circuits where these fuses may be required in supplying power to control circuits used for the shutdown method and may be blown by the effects of a cable spreading room fire. The spare fusec should be located convenient to the existing fuses.
The shutdown procedure should inform the operator to check these fuses.
Response
Spare control circuit fuses will be made available in the ASSS room. The procedures will alert the operator to the possibility of having blown control circuit fuses.
Item (h)
Demonstrate that the manpower required to perform the shutdown functions using the procedures of (f), as well as to provide fire brigade members to fight the fire is available as required by the fire brigade Technical Specifications.
Responsef Lased on present fire brigade requirements, there are three people available
= to perform the shutdown functions; the shif t supervisor and the two control l
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av Jrooml operators.- However, only two; people'are required to shift controll sc
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from the control room'to.the ASSS room.
Nhen'it has been determined thatucontrol must be shifted from the control
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room'to'~the'ASSS room,ithe following sequence of _ actions are taken by the (two operators:
LThe1 reactor is l manually tripped which results in an automatic turbine.
- _ 1.
This function'can'be performed from the. control' room or the
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- switchgear room. _ Since a ' fire barrier exists between the. two rooms,
- a. simultaneous. forced evacuation is-not considered a credible event.
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'2.-
Start No.f3 diesel.
?One of ~the operators then leaves the control room and proceeds to' the 3.1 2
Here he lines up safety upper: level primary auxiliary building.(PAB).
Linjection flow to the alternate emergency feedwater system. JThis requires the operation of>two valves.
~ Th'is operator.then; proceeds to the safety injection building on his
' 4.
Here he insures that the breaker from the No.
'way to the'ASSSl room.
3 battery: distribution switchboard over.to the switchgear room is open
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and-locked-open. ~He also insures that the No'. 3 diesel bus' tie breaker sover-to the switchgear room is open and locked open.
This operator _then enters the:ASSS room and-establishes communication
-5.
with the operator remaining-in the.concrol* room or the switchgear room.
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He~then; transfers control of the No. 3^ diesel over to the ASSS room.-
He then energizes.the panels'in the ASSS room and operates all of the transfer switches to take control of the safe shutdown equipment.
At this point, the operator remaining in the control room or switchgear 6.
room-causes a loss of off-site ac power 'and proceeds over to the ASSS The six breakers required'for this action can be operated from room.
either the' control room or switchgear room.
7.
Simultaneous _with Step 5, the operator in the ASSS room initiates steam generator feed by starting the two safety injection pumps, No. 3 high pressure (HPSI) and.No. 3 low pressure (LPSI). The operator _can then monitor system parameters and operate pressurizer heaters, charging
'and bleed as necessary to maintain _ hot shutdown conditions.
4 At the completion of the above actions, the conditions required to maintain the plaat in a hot shutdown are being monitored and controlled from the t
new ASSS room by the two operators.
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Item'(i)
Demonst rate that adequate acceptance tests are performed. These should equipment operates from the_ local control station when the verify:that:-
transfer or isolation switch is placed in the " local" position and that
.the equipment cannot be operated 'from the control room; and that equipment
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operates from the control room but cannot be operated at the local control station _when-the transfer or isolation switch is in the " remote" position.
Re sponse :
DAs part of the initial system testing following installation, test-procedures will be prepared and performed to verify the proper operation of the equipment with the new arrangement as required.
Item-(j)
Technical l Specifications of the surveillance requirements and limiting _
conditions for operation for that equipment not already covered by existing Tech. Specs. For example, if new isolation and control switches are added to a service water system, the existing Tech. Spec. surveillance requirements on the service water system should add a statement similar to the following:
"Every third pump test should also verify that the pump starts from the alternate shutdown station after moving all service water system isolation switches to the local control position."
Response
Technical Specification revisions will be submitted as part of the proposed change when the system design is completed and prior to implementation.
These revisions will include the necessary surveillance requirements and limiting conditions for operation for that equipment not already covered and for equipment already covered where needed.
Item (k)
Demonstrate that the systems available are adequate to perform the necessary shutdown functions. The functions required should be based on previous analyses, if possible (e.g., in the FSAR), such as a loss of normal ac power or shutdown on a Group I isolation (BWR). The equipment required for the alternate capability should be the same or equivalent to that relied on in the above analysis.
Response
l u.e loss of ac power procedure requires the following functions:
1..
Reactor scram capability.
2.
Decay heat removal, utilizing emergency feed to the steam generators and dumping steam to atmosphere.
L3.
Primary system pressure control utilizing charging, bleed, and pressurizer heaters.
The ASSS system provides these same necessarv functions with the following systems:
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Risactor scram is accomplished manually from the control room or the twitchgear room.
2.
Decay-hest removal is accomplished by using - the No. 3 LPSI and HPSI pump combination to supply emergency feed utilizing the SI connection to the alternate emergency feed path. The capacity of this pump
- combination is in excess of the normal' emergency feed pumps. - The steam is vented to the secondary: vent stack using the safety valves and/or the steam durp valves, which are also used by the loss of ac power procedure.
3.,
. Primary system pressure control is maintained by-using a set.of pressurizer heaters, a charging pump, and the necessary motor-operated valves (MOVS) required for charging and volume control.
Item (1)
Demonstrate that repair procedures for cold shutdown systems are developed and material for repairs is maintained on-site.
Re sponse :
Cold shutdown will be accomplished using a shutdown cooling pump and a component cooling pump with their respective heat exchangers. This is the normal: shutdown cooling system. In order to use this system, the following temporary system connections must be utilized:
1.
Cooling water for the component cooling water heat exchanger will be-supplied by the fire system, if available, or a fire truck or other portable pump utilizing an existing emergency connection in the service water-piping to the component cooling heat exchanger. This is located in piping in the PAB.
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2.
Power to the component cooling water pump will be supplied by the No.
2 diesel generator utilizing temporary connections (see Figure 4).
3.
The de power to start No. 2 diesel will be supplied by temporary jumpers from No. 3 battery.
As discussed in the response to Item (f), procedures covering these requirements will be forwarded as soon as available following completion of the engineering design. The necessary material required by these procedures will be maintained on-site.
F-K i, -
ENCLOSURE 2 Request for Additional Information
' Item 1.A.:
Provide a table that lists all' equipment including instrumentation and support system equipment that are required by the alternative or dedicated -
method of achieving-and maintaining hot shutdown.
Re sponse:
Tables 1 and 2, attached, list all of. the equipment, instrumentation, and-
~ support system equipment that are required by the ASSS.
Item 1.B._
For each alternative shutdown equipment listed in 1.A above, provide a table that lists the essential cables (instrumentation, control and power) that are located in the fire area.
Response
As discussed in various responses to Enclosure 1, the basic design philosophy of the ASSS utilizes transfer switches which divorce all of the control e
and power cables in the fire area from the ASSS equipment. The system will provide new instrumentation circuits, and new power and control cabling and circuits whenever the normal cabling and circuits are located in the fire-area.
Item 1.C.
Provide a table that lists safety-related and non-safety-related cables associated with the equipccat and cables constituting the alternative or dedicated method of shutdown that are located in the fire area.
Re sponse :
The table requested is not required since all of the cabling for the ASSS equipment which is located in the fire area will be isolated from the equipment by the transfer switches. Also, all of the existing cabling and new cabling being' installed which are required for the operation of the ASSS equipment will be located outside of the fire area.
Item 1.D.
Show that fire-induced failures of the cables listed in B and C above will not prevent operation or cause maloperation of the alternative or dedicated j
shutdown method.
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Response
. As discussed in Items 1.B and' C and shown in,the typical circuit diagram,
- Figure 2, all cables.that are subject to file damage are isolated from the ccircuit for the - ASSS equipment by their respective transfer switches.
.-.Therefore, any fire-induced failures of these cables will have no affect
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on.the operation of the ASSS' equipment.
Item 1.E.
For each cable listed in 1.B above, provide detailed electrical schematic drawings that show how each cable is isolated from the fire area.
Re sponse:
As discussed in item 1.B, there are no essential cables for the ASSS equipment located in the fire area.
Item 2.A.
Identify aach high-low pressure interface that uses redundant electrically controlled devices (such as two series motor-operated valves) to isolate or preclude rupture of any primary coolant boundary.
Response:-
There are three high-low pressure interfaces that use redundant electrically controlled devices to isolate or preclude rupture of any primary coolant boundary:
1.
The shutdown cooling system.
2.
The main coolant drain and sampling system.
3.
The pressurizer power operated relief valve (PORV).
Item 2.B.
Identify the device's essential cabling (power and control) and describe the cable routing (by fire area) from source to termination.
Response
The fire area of concern is the switchgear room which is located directly under the control room (see Figure 1).
1.
The shutdown cooling system utilizes series MOVS to isolate the suction and return lines to the primary. The four (4) LuVS power and control cables are located in close proximity on the south wall, facing the containment (see Figure 1).
2.
The main coolant drain and sampling system utilizes two MOVS and one po. '
-e air-operated trip valve in' aeries to isolate two different. paths.
a The trip' valves are actuated by,two de solenoid-operated valves in series. The trip valves are part of the containment isolation -system.
The MOVS power and contro1 cable _are located in close proximity on
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.thessouth. wall, facing the containment. The de power.and control cables
.for the soleno!.d-operated trip. valves are located on the. west wall of the switchgear room (see Figure 1).
3.
1&ur pressurizer' PORV and its motor-operated block valve have power and control cables which are run in close proximity in the cable trays located in'the switchgear room overhead, where these cables run up through the floor into the main control board in the control room..
Item i.C.
Identify each location where the identified cables are separated by less than a wall having a three-hour fire rating rrom cables for the redundant
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device.
Response
See the response to Item 2.B.
Item 2.D.
For the areas identified in Item 2.C above (if any), provide the. bases and n
justification as to the acceptability of the existing design or any proposed.
modifications.
Response
1.
Shutdown cooling system valves -
The ASSS design will modify the existing arrangement to insure separation of power and control cables by either 20 feet or a three-hour fire barrier.
2.
Main coolant drain and sampling system valves - the existing design is acceptable'since there is a physical separation between the power and control cables for the MOVS and solenoid-operated trip valves of greater than 20 feet, and the area has fire detectors and an automatic fire suppression system.
I-3.
Pressurizer PORV and block valve - the existing design is acceptable.
l The ' power cable to the pressurizer PORV runs out of the switchgear room, the fire area of concern, and into the control room where it is separately fused. Therefore, removal of the fuses in the control room removes power to the PORV and isolates it from any fire damage j
in the switchgear room.
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TABLE 1 Equipment for-Safe Shutdowa Component Component Location 1.
Required for Safe St.utdown No.,1 Charging Pump Primary Auxiliary Building MOV-523,524,525 & 527 Containment Containment-
_ Vari-Orifice Containment 1 Croup Pressurizer. Heaters
-No. 3 High : Pressure Safety Injection Pump Safety. Injection Building No. 3 Low-Pressure Safety Injection Pump Safety-Injection Building
.2. ; Required for Cooldown MOV-191 & 613 Containment
. Shutdowr. Cooling Pump Primary Auxiliary Building Component Cooling Pump Primary Auxiliary Building.
MOV-551,552,553 & 554 Containment 3.
Supporting Equipment for Safe Shutdown No. 3 Diesel Generator & Associated Safety Injection Building Equipment No. 3 Battery.
Safety Injection Building.
New Instrumentation Vital dus Inverter Safety. Injection Building
'Emergencf Lighting and Communications 4.
Supporting. Equipment for Cooldown No. 2 Diesel Safety Injection Building t
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Instrumentation For Safe ShutdownL
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Instrument Number of Instrument Location Channels PressurizerLWide Range Level Containment 1
Pressur'izer Pressure Containment 1
Steam Generator Wide Range Levels Containment 4(one per loop)
-Incore Thermocouples or Loop TH's Containment 2
Neutron Detector Containment 1
Steam Generator Pressure Non Return Valve
- 4(one per loop).
Platform
< Shutdown Cooling Inlet Temperature PAB l'
Shutdown Cooling Outlet Temperature PAB 1
Component Cooling Inlet Temperature PAB 1
Component Cooling Outlet Temperature PAB 1
Diesel Generator (D.G.):
Water Temperature D.G. Cubicle 1 per D.G.
Oil Pressure D.G. Cubicle 1 per D.G.
Frequency ASSS Console 1 per D.C.
Voltage ASSS Console 1 per D.G.
Amperage ASSS Console 1 per D.G.
KW ASSS Console 1 per D.G.
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