ML20041D938
| ML20041D938 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/03/1982 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Adensam E Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8203090576 | |
| Download: ML20041D938 (16) | |
Text
l TENNESSEE VALLEY AU"iOR!TY CH ATTANOOGA, TENN ESSEE. 3 '4o f 400 Chestnut Street Tower II March 3, 1982 O
o
\\
Director of Nuclear Reactor Regulation
- RECSVED
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Attention:
Ms. E. Adensam, Chief Licensing Branch No. 4 9;
- AR 0819 p Division of Licensing
'W mean U.S. Nuclear Regulatory Commission
,g 4
Washington, DC 20555 g
7 to
Dear Ms. Adensam:
In the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority 50-328 Enclosed is our rasponse to your November 12, 1981 letter to H. G. Parris which requested additional information on fire protection as a result of our October 1, 1981 submittal and the October 27, 1981 meeting to discuss differences in the Sequoyah plant design and the requirements of sections III.G, III.J, III.L, and III.0 of 10 CFR Part 50, Appendix R.
If you have any questions concerning this matter, please get in touch with J. E. Wills at FTS 858-2683 Very truly yours, TENNESSEE VALLEY AUTHORITY L. M. Mills, Manager Nuclear Regulation and Safety Sworn to d subscribed be ore me thist L_.- day of 1982 t
Notary Public My Commission Expires b
Enclosure cc:
U.S. Nuclear Regulatory Commission Region II Attn:
Mr. James P. O'Reilly, Regional Administrator 101 Marietta Street Suite 3100 Atlanta, Georgia 30303
= =8 e a88888, i
F PDR An Equal Opportunity Emptoyer
ENCLOSURE RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION f
SAFE SHUTDOWN IN THE EVENT OF FIRE l
AUXILIARY SYSTEMS BRANCH SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2-1.
The safe shutdown logic diagram (Figure 1-1) of the Sequoyah safe shutdovn submittal dated October 1, 1981, indicates that credit is taken for the use of automatic control functions to achieve and maintain hot shutdown conditions. During the meeting on October 27, 1981, the applicant indicated that all automatic control logic may be lost in the event of a fire in the auxiliary instrument room. Please provide a discussion of how hot shutdown will be achieved and
^
maintained in the event of a fire in the auxiliary instrument room or any other area in which automatic functions can be rendered inoperable. This discussion should address the use of alternate instrumentation and controls methods, and all systems to which automatic function or control will be disabled.
TVA RESPONSE 4
The following discussion illustrates 'how hot shutdown capability will be maintained in the event of loss of automatic control logic functions (ACLF) due to fire in the auxiliary instrument room (AIR), main control room (MCR), auxiliary control room (ACR), or local control panels. These locations house ACLF instrumentation appearing on the Fire Shutdown Logic Diagram (FSLD). The loss of any one of these locations can cause the loss of some but not all of the ACLF used in the event of fire.
Given below is a list of ACLF and information addressing alternate i
instrumentation and control methods.
I.
Automatic Logic Speed Control for CVCS Reciprocating Charging Pump The function is lost if the AIR or the MCR is lost in the postulated fire. If such a loss occurs, the alternate charging path identified on the FSLD (Centrifugal Charging Pumps) will be available by manual centrol for RCS makeup and RCP seal injection. The operator also has an option to regain control of the speed controller from the manual backup station on panel L-369. Therefore, it is not credible to lose RCS inventory control identified on the FSLD in the event of the loss 1
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of this automatic logic controller.
Note: Even in the event of failure of the automatic logic speed controller, flow within the setpoint range of 55-98 gpm would be provided to the regenerative heat exchanger and RCP seal injection line.
II. Automatic logic controls to motor-driven auxiliary feedwater pump's (MDAFWP) outlet valves (PCV-3-122, -132).
In the event of the loss of this automatic control function, the alternate steam generator charging path identified on the FSLD, turbine-driven auxiliary feedwater pump (TDAFWP), will not be affected by the postulated fire. A discussion of this has been 1
. provided in the Sequoyah safe shutdown submittal dated October 1, 1981. However, as an option, the operator can regain control of the function performed by the outlet valves. These techniques are discussed below in cases 1-4.
Case 1: Loss of AIR The automatic function will be lost for both valves if the AIR is lost in the postulated fire. However, the operator may_ regain the automatic function in the ACR.
Case 2: Loss of MCR The automatic function will be lost for both valves if the MCR is lost in the postulated fire. However, the o; orator may regain the automatic function in the ACR.
Case 3: Loss of ACR The automatic function from the ACR will be lest if panel L-10 is lost in the postulated fire. However, the normal control from the MCR will be unaffected.
The automatic function for one of these valves will be lost if the valves' respective panels L-11A or L-11B are lost in the postulated fire. However, the operator can regain control manually at the valve using the valves' handjack.
Case 4: Local Panels L-214 and L-222 Automatic control for valves PCV-3-122 or PCV-3-132 will be lost if the local panels L-214 or L-222, respectively, are lost in the postulated fire. However, normal operations of the opposite train will not be affected.
Therefore, the loss of the automatic control function, due to the postulated fire, will not prevent the operators from safely shutting the plant down.
III. Automatic Logic Controls to Steam Generator (SG) Level Control 7alves (LCV-3-148, -156, -164, -171, -172, -173, -174, -175)
Valve operation requires the availability of the ACR transfer switch panels.
If either one of the panels is lost, the redundant panel will prevent loss of AFW to any of the SGs. The ACR is divided by fire barriers such that a single fire would only affect one transfer switch panel. Therefore, it is not credible to lose the SG level control function.
.I
. IV.
Automatic Logic Controls to SG Relief Valves (PCV-1-5, -13, -23, -30)
Valve operation requires the availability of the ACR transfer switch panels. If either one of the panels is lost, the redundant panel will prevent loss of AFW to any of the SGs. The ACR is divided by fire barriers such that a single fire would only affect one transfer switch panel. Only two of the SG relief valves are required to be operable for safe shutdown. Manual backup control stations are also provided in the steam valve rooms for manual control and have been demonstrated to be acceptable for control operations of the valves. Therefore, it is not credible to lose the control function of the SG relier valves.
V.
Automatic Logic Control for the Centrifugal Charging Pump Discharge Flow Control Valve (FCV-62-93).
Case 1: The automatic function will be lost if the AIR is lost in the postulated fire. However, independent manual control may be used from the MCR, ACR, or local panel L-112.
Case 2: The automatic function and the independent manual controls in the MCR and ACR will be lost if panel L-11B
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in the ACR is lost in the postulated fire. However, independent manual control may be used from local panel L-112.
Case 3: The automatic function and independent manual controls in the MCR, ACR, and local panel L-112 will be lost if panel
.L-112 is lost in the postulated fire. However, the alternate RCS charging path for RCP seal water injection on the FSLD (positive displacement charging pump's path) will not be affected by this fire. Therefore, it is not credible to lose RCS seal injection capability with the loss of this automatic control function.
Note:
As an option, the operator can open the valve without i
regulating capability by manually terminating the electrical input signal at the valve or manually terminating the air supply to the valve. This is an effective method since FCV-62-93 is a fail-open valve.
VI.
Speed Control for Turbine-Driven Auxiliary Feedwater Pump (TDAFWP)
The automatic logic control for the TDAFWP is not located in the MCR, ACR, or the AIR. Therefore, the postulated fire in these locations would not have an impact on this automatic function; however, the function may be lost in the event of fire at L-326A or L-381. These panels are located near the TDAFWP. A fire at this location will not have an impact on the alternate charging path (MDAFWP) for the SG inventory control. A discussion with regard to this matter has been provided in the Sequoyah safe shutdown submittal dated October 1, 1981. Therefore, it is not credible to lose SG inventory control wic.h the loss of this automatic logic control function.
2
.. Therefore, we conclude that no essential ACLF functions identified on the FSLD will be rendered inoperable by a fire. Alternate instrumentation and control methods have been provided to assure that the necessary functions will be available.
2.
Provide a discussion of the auxiliary control room (ACR) with respect to electrical isolation from the main control room (MCR), dedicated instrumentation which will monitor required system parameters (i.e.,
pressure, temperature, tank levels), and manual actions required to transfer control from the MCR to the ACR.
TVA RDSPONSE The auxiliary control system (ACS) is aesigned to provide necessary controls to establish and/or maintain the plant in a safe shutdown condition external to the control building. Controls in the ACS are physically separated from wiring exposed to the control building environment. The separation is provided in some cases by instrument and control loops dedicated to the ACS and other cases by use of a transfer switch that will physically disconnect the desired circuit from the wiring in the control building. The transfer switches are seal-wired and are annunciated in the main control room (MCR) any time a switch is not in the norce.1 mode.
The design is for the ACR to be the central control point in the auxiliary control mode. All systans requiring frequent manipulation, such as auxiliary feedwater, have the necessary controls located in the ACR along with their transfer switches. Also, adequate system monitoring is provided in the ACR for the operator to monitor the condition of the plant. #
The ACR is the central point of a redundant sound-powered telephone system linking it with various areas in the plant.
Upon evacuating the MCR, the operator will proceed to the ACR and operate the transfer switches located there to activate the controls in the ACR.
Assistant operators will proceed to the various switchgear cabinets and operate the transfer switches located there. The auxiliary control switches for all motor-operated valves and motors are also located on the switchgear. These switches are maintained contact and only require alignment one time. The assistant operators align all the switches by way of a check sheet.
Figures 2-1 and 2-2 (attached) are single line representations of typical air-operated control valves that have ACH controls. The auxiliary control board and the transfer switch panels are located in the ACR. The trains A and B transfer switch panels are separated from the auxiliary control board and each other by fireproof barriers. For this type of circuit, complete elsetrical isolation of the ACR from the MCR is accomplished by the~
r ansfer switch. The contacts of the transfer switch are break-before-Joe, which means that the MCR and the ACR control devices and power supplies are never connected together.
-S-Figure 2-3 (attached) is a single-line representation of a typical motor-operated pump or valve which has auxiliary control. The control switch and transfer switch are both located in the same switchgear as the circuit breaker. When the transfer switch is in the " auxiliary" position, the MCR control devices are completely isolated. When the transfer switch is in the " normal" position, the auxiliary controls on the switchgear are disabled. The interlock is from a dedicated ACR instrument channel.
Figure 2-4 (attached) shows a representation of a dedicated instrument channel. The I/I device is a current-to-current isolator. This shows that the instrument channels that are dedicated to auxiliary control and have an MCR interface are immune to MCR faults. Table 2-1 gives the plant parameters that have indication in the ACR by a dedicated instrument channel or channels.
The manual actions required to transfer control from the MCR are to place all the transfer switches in the " auxiliary" position. There are several plant features which preclude inadvertent or unauthorized actuation of the transfer switches. There are administrative procedures as to the employees that have access (keys) to the areas its which the transfer switches are located. When any transfer switch is placed in the " auxiliary" position, the MCR has an annunciator alarm. There is a seal wire on each transfer switch that will be broken when the switch is placed in the " auxiliary" position.
TABLE 2-1 AUXILIARY CONTROL ROOM DEDICATED INSTRUMENT CHANNELS T
Reactor Coolant System Preasure (2 narrow range, 1 wide range)
Reactor Coolant System Temperature (4 Thot' 1 per loop)
Pressurizer Water Level (2 channels)
Auxiliary Feedwater Pumps Discharge Pressure (1 per pump)
Turbine-Driven Auxiliary Feedwater Pump Discharge Flow Steam Generator 1, 2, 3, 4 Auxiliary Feedwater Flow (1 per steam generator)
Steam Generator 1, 2, 3, 4 Level (1 per steam generator)
Steam Generator 1, 2, 3, 4 Pressures (1 per steam generator)
Containment Pressure Volume Control Tank Level Charging Header Flow Charging Header Pressure Letdown Heat Exchanger Outlet Temperature RCS Pressurizer Relief Tank Level RCS Pressurizer Relief Tank Pressure Safety Injection System Accum. Tanks 1, 2, 3, 4 Pressure (1 per tank)
RHR Injection or Recirculation after LOCA Flow RHR Pumps Discharge Flow (1 per pump)
ERCW Supply Headers Flow (1 per header)
CCS Heat Exchangers Inlet Pressure (1 per heat exchanger)
CCS Surge Tank Demineralized Water Inlet Level CCS Surge Tank Demineralized Water Outlet Level i
. CCS Supply Header to RHR Heat Exchanger Flow (1 per heat exchanger)
CCS Supply Header to Miscellaneous Equipment Heat Exchangers Flow RHR Heat Exchangers Outlet Temperature (1 per heat exchanger)
Source Range Neutron Flux RHR - Residual Heat Removal System ERCW - Essential Raw Cooling Water System CCS - Component Cooling System RCS - Reactor Coolant System 3
Provide a list of system parameters which must be monitored to assure proper plant conditions during hot shutdown and cold shutdown i
operation. Provide a list of instrumentation / alarms which will monitor these system parameters and component functions in the event of fire (e.g., pressurizer pressure indicator, cold leg / hot leg temperature,_
steam generator pressure and level, pump running indicators, condensate storage tank level). Verify that the applicable indicators are available in the MCR, ACR, and other remote shutdown boards.
TVA RESPONSE The parameters listed below are identified in the Fire Shutdown Logic Diagram (FSLD) as being essential for hot and cold shutdown:
Steam Generator Level Steam Generator Pressure Pressurizer Level Pressurizer Pressure Therefore, sufficient instrumentation (alarms, indicators, records, etc.) regarding these parameters have been verified to be available to the operator in the MCR and, separately, in the ACR in the event of a fire within the plant.
The following instruments are protected from fire by Kaowool blankets from the reactor building wall to the MCR wall:
Steam Generator Level Instrument Loops in MCR Required by FSLD SG #1 LT-3-38, 39, 42 SG #2 LT-3-51, 52, 55 SG #3 LT-3-93, 94, 97, 172 SG #4 LT-3-106, 107, 110 Steam Generator Pressure Instrument Loops in MCR Required by FSLD SG #1 PT-1-2A, 2B, 5 SG #2 PT-1-9A, 9B, 12 SG #3 PT-1-20A, 20B, 23 SG #4 PT-1-27 A, 27B-30
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, Pressurizer Level Instrument Loops in MCR Required by FSLD LT-68-339, 335, 320 Pressurizer Pressure Instrument Loops in MCR Required by FSLE PT-68-340, 334, 323, 322 The following instruments are protected from fire by Kaowool blankets from the reactor building wall to the ACR wall.
Steam Generator Level Instrument Loops in ACR Required by FSLD SG #1 LT-1-164 SG #2 LT-1-156 SG #3 LT-1-148 SG #4 LT-1-171 Steam Ger.erator Pressure Instrument Loops in ACR Required by FSLD SG #1 PT-1-1C SG #2 PT-1-8C SG #3 PT-1-19C SG #4 PT-1-26C Pressurizer Level Instrument Loops in ACR Required by ESLD LT-68-326C, 325C Pressurizer Pressure Instrument Loops in ACR Required by FSLD PT-68-337C, 342C The parameters given below are not required by the fire shutdown logic to be available for the operator in the event of a fire within the plant. However, the parameters instrument loops have been wrapped in Kaowool blankets. Therefore, these parameters will be available to the operator in the MCR.
4
, Reactor Coolant System Temperature TE-68-2A, 2B: Loop 1 Hot Leg RTD Manifold Temperature
- TE-68-1:
Loop 1 Hot Leg Temperature TE-68-18:
Loop 1 Hot Leg Temperature TE-68-25A, 25B: Loop 2 Hot Leg RTD Manifold Temperature
- TE-68-43:
Loop 3 Hot Leg Temperature TE-68-44A, 44B: Loop 3 Hot Leg Manifold Temperature TE-68-60:
Loop 3 Cold Leg Temperature TE-68-67A, 67B: Loop 4 Hot Leg RTD Manifold Temperature.
' Instrument loops also available in the ACR.
Reactor Coolant System Flow FT-68-6A, 6B, 6D:
Loop 1 Coolant Flow-FT-68-29A, 29B, 29D:
Loop 2 Coolant Flow FT-68-48A, 49B, 49D: Loop 3 Coolant Flow FT-68-71A, 71B, 71D:
Loop 4 Coolant Flow Steam Generator Feedwater Inlet Flow Loops SG #1:
FT-3-35A, 35B SG #2:
FT-3-48A, 48B SG #3:
FT-3-90A, 90B SG #4:
FT-3-103A, 103B Steam Generator Steam Header Flow Loops SG #1:
FT-1-3A, 3B SG #2:
FT-1-10A, 10B SG #3:
FT-1-21A, 21B SG #4:
FT-1-28A, 28B Miscellaneous Pressure Instrument Loops PT-68-66:
RCS Loop #4 Hot Leg Pressure PT-1-72: High Pressure Turbine Impulse Chamber Pressure PdT-30-42, 43: Containment Pressure Miscellaneous Level Instrument Loops LT-63-51,53 SIS RWST Level LT-63-176,177,179 Containment Level a
, Gi en below are additional parameters and instrumer.tation located in the ACR. The instrument cables between the reactor building and the ACR wall are not protected from fire. However, ttiese instruments are not required by the FSLD to function in the event of fire in the ACR or between the ACR and reactor building. This instrumentation would be used only in the event of a fire in the MCR and is electrically independent of the instruments located in the MCR.
PT-1-1C, -8C, -19C, -26C Steam Generators Nos. 1,2,3,4, respectively, pressure. 0-1200 psig l
l PT-3-122C, 132C Auxiliary Feedwater Pumps A&B backpressure 0-1600 psig FT-3-142C Turbine Driven Auxiliary Feedwater Pump Flow 0-1000 gpm FT-3-147C, -155C, -163C, -170C Steam Generators Nos. 1, 2, 3, 4, respectively, Auxiliary Feedwater Flow.
0-440 gpm.
LT-3-148, -156, -164, -171 Steam Generators Nos. 1, 2, 3, 4, respectively, Level 0-144 in water column PT-30-30C Containment Pressure +15 psig TE-62-80C Letdown Utx Outlet Temp 50-150 F PT-62-92C Charging Header Pressure 0-3000 psig FT-62-93C Charging Header Flow 0-200 gpm LT-62-129C Volume Control Tank level 0-100%
PT-63-59C, -83C, -102C, -120C SIS Accumulator Tanks Nos. 1,2,3,4, respectively, Pressure 0-700 psig FT-63-173C RHR Hot Leg Injection or Recirc After LOCA Flow 0-7000 gpm FT-63-91C, -92C RHR Pumps Discharge Flow 0-4500 gpm FT-67-61C, 62C ERCW Supply Headers A&B Flow 0-20,000 gpm TE-68-1C, -24C, -43C, -65C RCS Loops Nos. 1, 2, 3, 4, respectively, Hot Leg Temp 0-650 F
. PT-68-311C RCS PRT Pressure 0-10 psig LT-68-312C RCS PRT Level 0-100 in water column LT-68-325C, -326C RCS Pressurizer Level 0-525 in water column PT-68-3360, -337C RCS Pressurizer Level 1700-2500 psig PT-68-342C RCS Pressurizer Pressure 0-3000 psig PT-70-17C, -24C Component Cooling System (CCS) Htx A&B-Inlet Pressure 0-120 psig LT-70-63C, -99C CCS Surge Tank Level 0-100%
FT-70-159C, -165C CCS Flow to RHR Htx A&B 0-6000 gpm FT-70-164C CCS Mise Eqpt Supply Hde Flow 0-5000 gpm TE-74-38C, -40C RHR Htx A&B Outlet Temp 50-400 F RR-90-210 SourgeRangeNeutronFlux 1-10 We conclude that essential instrumentation, as required by the FSLD, and other desirable instrumentation will be available to the operator in the MCR or ACR. This instrumentation will provide the operators with sufficient parameter data to obtain and maintain hot and cold shutdown.
4.
In many instances, one control / actuation signal will cause the actuation of several functional components. Verify that the depressurization of the primary side via interfacing system will not occur due to the actuation of system components resulting from the fire induced generation of spurious signals from associated circuitry. Your discussion should include the means of preventing RHR isolation valve actuation, uncontrolled letdown, pressurizer PORV actuation, or operation of any valve or component which would prevent the system (s) from performing its functional objectives, t
. TVA RESPONSE Pathways by which the primary system potentially could be depressurized due to spurious fire-induced signals are as follows:
1.
RCS to RHR system by way of opening of the RHR isolation valves.
2.
RCS to. pressurizer relief tank by way of the pressurizer PORV's.
3 RCS to containment and/or pressurizer relief tank by way of the reactor vessel head vent system solenoid valves.
4.
Reactor coolant pump seal failure due to a loss of seal cooling.
5.
RCS to CVCS by way of the normal letdown or excess letdown paths.
TVA is investigating the potential for fire induced depressurization by way of these pathways and will describe the means of preventing the depressuri-zation in a supplemental response by February 28, 1982.
5.
Verify that procedures which describe tasks that are to be performed to effect the shutdown method have been developed and are available to appropriate plant personnel. Also, demonstrate that the manpower required to perform the shutdown functions in accordance with your procedures, as well as to provide fire brigade members to fight the fire is available as required by the fire brigade technical specifications.
TVA RESPONSE Procedures which describe tasks that are to be performed to effect the shutdown method have been developed and are available to the appropriate plant employees. Emergency Operating Procedures describes the required action and placement of operating employees to bring the plant to cold shutdown condition. Existing manpower is sufficient to perform the emergency procedure and comply with technical specification requirements regarding the plant fire brigade.
SRM:COH 02/02/82 Attachments
Figure 2-1 ccMROL Auxiliary Main Control tf IMIC h Control Board Board Supply #1 Auxiliary Instrument Battery e
Room Board Suop1y #2
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Transfer Switch
Normal "
position shown o
Transfer Switch Panel e
Final Control Device
figure 2-2 Main Control Board-I,
Auxiliary Auxiliary Control Instrument Board Room A
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-d Transfer Switch Power 7
Supply Transfer Switch Panel V
Fina)
Process Control Proce'ss Sensor Device Sensor O
Figure 2-3 Main Auxiliary Control Instrument Transfer, Switch Panel Board Room Interlock e
Control Switch IIS 1
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Transfer Switch
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H 52 Circuit Breaker Switchgear-V Motor 4
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Figure _2-4 Indicator Annunciator liain Control Room -
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I/l Alarm Relay A
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Tran.sfer Switch Pa.ne Power Supply V
Indicator Auxiliary Control Board Transmitter 4
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