ML19305B686
| ML19305B686 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities, Zion  |
| Issue date: | 02/28/1980 |
| From: | Peoples D COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEB-79-27, NUDOCS 8003200076 | |
| Download: ML19305B686 (25) | |
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Cornfnonwealth Edison gC One First Nitional Plaza. Chicago. Illinois
~r k C 1 Address Reply to: Post Office Box 7@
Nj Chicago. Illinois 60690 February 28, 1980
?'r James G. Kepoler, Director Directorate of Inspection and Enforcement - Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Poad Glen Ellyn, IL 60137
Subject:
Dresden Station Units 1, 2, and 3 Quad Cities Station Units 1 and 2 Zion Station Units 1 and 2 Response to IE Bulletin 79-27 Concerning Ioss of Instrumentation and Control Power Buses NRC Docket Nos. 50-10/237/249, 254/265, and 50-295/304 Reference (a):
J. G. Keppler letter to C. Reed dated November 30, 1979
Dear Mr. Keppler:
Reference (a) transmitted IE Bulletin 79-27, which requested a response in ninety days to concerns relating to loss of non-Class I-E instru-mentation and control power system buses during operation.
Our responses for Dresden Unit 1, Dresden Units 2 and 3, Guad Cities Units 1 and 2, and Zion Units 1 and 2 are contained in attachments 1, 2, 3 and 4, respectively.
No nodifications, except for those already in progress at Dresden 1, are deemed to be necessary based on the reviewes of existing installations at Dresden, Quad Cities, and Zion.
Please address any aditional questions you may have concerning this matter to this office.
Very truly yours, u
~
. up.
D. L. Peoples Director of Nuclear Licensing cc: Director, Division of Reactor Operations Inspection
%hh 8003200076
ATTACllMENT 1 REVIEW OF CLASS lE AND NON-CLASS 1E INSTRUMENTATION AND CONTROL BUSES DRESDEN UNIT 1 i-
I.
Introduction The NRC has required all power reactor facilities with an operating j
license, in I.E.Bulletin 79-27, to review the loss of Class IE and Non-Class 1E instrumentation and control power buses during operation.
This report documents this review for Dresden Unit 1 and indicates that no modifications are required as a result.
II.
Systems /Compo_nents Necessarv for Safe Shutdown The Dresden Unit 1 Fire Protection Safe Shutdown Analysis, Janecek letter to Ziemann, dated March 20, 1979, identifies the equipment utilized to obtain a cold shutdown. The review of instrumentation and control sys-l tems which could effect the ability to achieve a cold shutdown condition was therefore limited to that equipment.
Figures 1 and 2 illustrate the method and identify the associated equipment.
III.
Instrumentation and Control Power Buses Tables 1 and 2 identify the instrumentation and control power buses utilized by the equipment listed in Figures 1 and 2, respectively. The following list summarizes the instrumentation and control power buses, including the associated control room indication and loss of pcwer annunciation.
Control Room Instrument / Control Bus Indication Annunciation ECCS 125VDC (Div. I & Div. II)
Bus yes/ meter
" trouble"
" trouble" l
Charger no
" trouble" Inverter no RPS MG (Train A & B) yes/ light "undervoltage" Unit 125VDC
" trouble" Charger (A & B) no
" trouble" Bus 3 no
" trouble" Bus 4 no "tro uble" Power Center no i
i Lighting Panels (120VAC) 22L(1) no no 31L(1) no no 39L(1) no no Instrument Bus 1(2) no no NOTES:
(1) Equipped with automatic throwover capability (2) Equipped with manual throwover capability As previously analyzed in the Fire Protection Safe Shutdown Analysis,
- a safe shutdown is not inhibited by an instrument / control bus failure.
Therefore, no modifications are planned as a result of this review.
~.
t IV.
Instrumentation / Control Bus Emergency Procedures The revision / development of the electrical system emergency pro-cedures will be included with the present upgrading of the Emergency Core Cooling System and the Essential Service Auxiliary Power System.
These modifications will be completed prior to unit startup.
The loss 2
of instrument and control power bus procedures will include, if appli-cable:
l A.
the available diagnostics, alarm, and indication B.
the identification of any alternate instrumentation or control circuits available 5
C.
methods for restoring lost power.
V.
Static Inverter Power Supplies
]
Two (redundant) 120VAC static inverters are being installed as part of the Essential Service Au::iliary Power System modification.
With respect to 1.E. Circular 79-02, Failure of 120 Volt Vital AC Power Supplies, the following design features are presently intended for the static inverters:
t A.
Upon loss of the preferred source and subsequent restoration, there will be ar approximate 2.0 second time delay before auto-matic transfer'oack to the preferred source.
This is intended to assure preferred source stability.
i B.
The vital bus preferred source will be a direct feed from an ESF distribution panel. The alternate source will be the ECCS 125VDC bus and the static inverter.
I C.
Associated alarms to ensure operability after maintenance and I
testing will include:
4 1.
low AC input voltage 2.
low DC input voltage 3.
inverter output failure 4.
manual transfer to inverter No static inverter design changes are planned as a result of this review.
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Emergency Condenser 4.
Control Rod Drive System h
h 5.
Motor Generator Sets - (RPS) 6.
125 V Battery 7.
Recirculation Pumps h
h h
8.
Primary Feed Pumps 9.
Secondary Feed Pumps h
h h
10.
Condens' ate Pumps h
h h
11.
Circulating Water Pumps h
12.
Service Water Pumps h
h 13.
Reactor Enclosure Cooling m
Water Ur 14.
Unloading Heat Exchanger lb.
Emergency Feed Pump r
16.
Feed Regulating Station h
17.
urbine Building Cooling g
g 18.
Turbine Oil Pumps h
h 19.
Instrument Air 20.
Service Air 21.
Make-up Pumps
- 22. Motor Generator Sets -
g r
Battery Charger DRE,SDEN STATION Unit 1 FIGURE 2 Number of components needed
+ Number of components available NORMAL SHUTDOWN PATH WITH OFFSITE POWER
.~
TABLE 1 CONTROL AND INSTRUMENTATION BUSES FOR EQUIPMENT IDENTIFIED IN FIGURE 1 Component / System Control / Instrument Bus SBLC Unit 125VDC (Bus 3 & 4)
Pumps Unit 125VDC (Bus 3)
Valves Lighting Panel 22L Instruments ESAP DG(I)
ECCS 125VDC(l)
HPCI{I)
ECCS 125VDC(I)
Logic ECCS Inverters (I)
Instruments (including Post Accident Monitoring)
Valves (2)
Electromatics Unit 125VDC (Bus 3)
Annunciators ECCS 125VDC(1)
ECCS (CS/PI)
Lighting Panel 22L Other Unit 125VDC (Bus 3)
DC Bell Unit 125VDC (Bus 3)
AC Bell Lighting Panel 31L NOTES:
(1) Part of the present upgrading modifications in progress (2) Control power obtained from a step-down transformer on the main power feed
i, TABLE 2 CONTROL AND INSTRUMENTATION BUSES FOR EQUIPMENT IDENTIPIED IN FIGURE 2 I
Control / Instrument Bus Component /Astem RPS ECCS 125VDC(l)
Backup Scram Valves ECCS 125VDC(l)
Containment Isolation Initiation RPS MG Sets Other L
i
~ Nuclear Instruments RPS MG Sets Channel 1-11 Unit 125VDC (Bus 3) e_
Channel 12 l
Bypass Indication Lighting Panel 22L i
Emergency Condenser II)
ECCS 125VDC MO-101 & 109 Unit 125VDC (Bus 3) l LCV-11 Lighting Pnnel 22L LIT-11 Lighting, Panel 22L TR-5 CRD RPS MG Sets Solenoid Valves
{
Position Indication Lighting Panel 38L i
Position Control Lighting Panel 22L t
4 RPS MG Sets (2) 125VDC Battery N/A Unit I
ECCS Division I N/A ECCS Division II N/A 1
Unit 125VDC (Bus 3 & 4)
Recirculation Pumps Primary Feedwater Pumps Unit 125VDC (Bus 3 & 4)
Unit 125VDC (Bus 3 & 4)
Secondary Feedwater Pumps Condensate Pumps Unit 125VDC (Bus 3 & 4)
Unit 125VDC (Bus 3 & 4)
Circulating Water Pumps Service Water Unit 125VDC (Bus 3 & 4)
Pumps
-MO-510 & 520 (2)
MO-521 Unit 125VDC (Power Center)
RECW Pumps (2)
PIT-504 Lighting Panel 38L Unloading (2).
l
is TABLE 2 CONTROL AND INSTRUMENTATION BUSES FOR EOUIPMENT IDENTIFIED IN FIGURE 2 (Continued)
'I' Control / Instrument Bus Component / System Emergency Feedwater Pump Unit 125VDC (Bus 3)
Feedwater Reg. Sta.
ECCS Inverter (I)
[
Primary Secondary Lighting Panel 31L, 38L, 6 Instrument Bus 1 (2) j! -
TBC1 Turbine Oil Pumps Emergency Bearing Lube 011 Unit 125VDC (Power Center)
Other (2) i l
Instrument Air Compressors (2)
Isolation Valve SV-562 Unit 125VDC (Bus 4)
Service Air Compressors (2)
Isolation Valve SV-563 Unit 125VDC (Bus 4) j Make-Up Pumps (2) 125VDC Chargers i
Unit MG Sets (2)
ECCS Static Chargers (2) i I
i NOTES: '(1) Part of the present upgrading modifications in progress (2) Control power obtained from a step-down transformer on the f.
main power feed L
ATTACHMENT 2 DRESDEN STATION UNITS 2 AND 3 RESPONSE TO I.E. BULLETIN 79-27 1.
Based on review of this bulletin, the following buses are addressed in this response to the bulletin for both units:
Instrument Bus 24/48 VDC Buses A and B s
Reactor Protection Buses A and B Essential Service Bus Instrument Bus The 120/240 VAC instrument bus is normally fed from MCC 28(38)-2, with the reserve supply from MCC 25(35)-2.
There is a normal seeking auto-matic transfer switch to MCC 25(35)-2 If normal power is lost.
A.
Control Room alarms are:
1) 120 VAC Instrument Bus Transfer to Emergency Supply 2) 120 VAC Instrument Bus Low Voltage Bus voltage indication is available in the Auxiliary Electrical Equipment Room. Other alarms that would come up if the instrument bus was lost are:
1) 24/48 VDC Battery Trip
- 2) Moisture Separator High Level
- 3) Main Steam Drain Tank High Level
- 4) Heater Drain Valve Closure B.
The following loads are connected to the instrument bus:
Panel 902(3) Off Gas Panel 902(3) HPCI Panel Panel 2202(3)-16 and 20 - Accumulator monitor Panel 902(3)-4 and 5 - Control Room panels Panel 902(3) Area radiation tonitors l
Panel 902(3) Reactor system process instrument power supply and 2202(3)-25A and 25B recire. M-G set Panel 902(3) CRD instrument, process instrument
1.
B.
(Continued)
Panci 902(3)-19 and 902(3) Jet pump and RPV level, pressure temperature instrumentation Panel 902(3)-6, 7, and 8 - Main control board, instruments, and recorders Panel 902(3)-6, 7, 8 and 2252(3) Main generator voltage regu-lator cubicle recorders and instrumentation Panel 902(3) Annunciator input relay, D.C. supply failure alarm Panel 902(3)-28, 40 - Reactor manual control Panel 902(3)-3, 4 - Test and pilot solenoid valves, isolation valves Panel 902(3)-32, 33 - ECCS relay, test check valves 1402-9A, 1501-25A Panel 2252(3)-14A and B, 2252(3)-16A-D - F.W. heater racks j
Panel 902(3)-2,10, 923-4,2223-4, 7, 9 - Prccess Radiation Monitor Panel 902(3) EHC cubicle Panel 2202(3) SRM/lRM drive control, 2252(3)-30, 48 local panel Master station supervisory cabinet 24/48 VDC neutron monitor battery chargers 125 and 250 VDC battery ground detector recorders Loss of the instrument bus would cause c loss of feedwater heater level control.
The normal drains would fail closed and the ex-traction steam dump valves will open. The moisture separator level would rise, and a high moisture separator level turbine trip and a reactor scram would occur.
Feedwater controllers, regulating valves, narrow range Yarway level indications, power level indication, and rod position indi-cation would be operable.
The above indications would be 'uffi-cient to verify the scram.
The loss of the 24/48 VDC battery chargers is of minimal concern since the battery is sized to main-tain the bus for eight hours. The following indications would be lost:
feedwater regulating valve position, feedwater flow, steam flow, GEMAC reactor water level, eore spray flow, core spray pres-l sure, wide-range reactor water levels, M-G set temperatures, CRD pressure, CRD flow, jet pump flow, recire. pump flow, recirc. pump DP, cleanup flow, cleanup temperature, recire. pump seal pressure, suppression chamber pressure, suppression chamber level, recire.
l The I
pump temperature, cleanup conductivity, and drywell pressure.
1.
B.
(Continued)
TIP ball valves would cloes, SBGTS trains would start, and the reactor building ventilation would isolate.
The reactor build-ing to suppression chamber vacuum breakers would open; however, t e check valves would prevent venting the suppression chamber to the reactor building. Placing and maintaining the reactor in a cold shutdown condition may still be accomplished due to the availability of normal feedwater flow, shutdown cooling, ECCS, and the main condenser. Also, the Yarway level instruments would be available to closely monitor reactor water level.
Other loads that would be lost are of no significance in placing or maintaining the reactor in cold shutdown.
C.
No modifications are proposed based on the above review.
24/48 VDC Buses A.
The 2(3) A and 2(3)B distribution panels are supplied by the 24/48 VDC batteries, rated at 80 amperes hours, and battery chargers.
There is an alarm in the Control Room for battery undervoltage.
Loss of the 24/48 VDC buses would cause Neutron Monitor Low Sup-ply alarm to come up.
The unit battery charger room has the following indications: charger voltage and amps, Bus A and B positive, and negative voltage.
B.
The following loads are connected to the 24/48 VDC system:
Panel 902(3) Process Radiation Monitor Panel 902(3) Source and Intermediate Range Monitor (SRM and IRM)
Panel 923 Process Radiation Monitor (Units 2 and 3)
Loss of the entire 24/48 VDC system will disable the process liquid radiation monitors and the chimney effluent monitors. The trip logic for the SJAE off-gas radiation monitors comes from the 24/48 VDC bus, the high radiation isolation would not function.
The SRM and IRM's will not function when the bus is lost. Oper-ating in any mode but RUN, the IRM protective relays vill de-energize and a reactor scram will occur. The SRM and IRM indica-tions, recorders, and lights will also be lost. Due to the use of both the battery chargers, the battery itself, and the redun-dant A and B buses, it is not anticipated that a loss of the en-tire system is likely. If a loss of the entire system did occur, the reactor can still be brought to, and maintain, a cold shut-down condition, due to the availability of feedwater, ECCS, reactor normal control, shutdown cooling, and the main condenser.
C.
No modifications are proposed based on the above review.
Reactor Protection System (RPS) Buses A and B Both 120 VAC RPS buses are supplied normally by an M-G set, which is fed from 480 VAC MCC 28(38)-2 and 29(39)-2. These MCC's are supplied
1.
(Continued) from emergency 480 VAC buses 28(38) and 29(39), which can be fed from their own emergency diesel generator. A reserve supply is key interlocked with 480 VAC MCC 25(35)-2 to prevent simultaneous feed to the RPS buse.
A.
Loss of both RPS buses for the unit will result in a reactor Group 11 and III Primary Containment Isolation (PCI) scram.
will occur, as will half the permissive for a Group I PCI.
Numerous control room alarms, as well as the reactor and turbine-generator parameter changes associated with a reactor scram will alert the operator to a loss of power to the RPS buses.
There are indications for bus amps, bus voltage, and generator voltage in the auxiliary electrical equipment room.
B.
The following loads are connected to the RPS buses:
Bus 2(3) A 1.
Panel 902(3) Process Radiation Monitoring 2.
Panel 902(3) RPS and PCI relays 3.
Panel 902(3) Power Range Neutron Monitoring Bus 2(3)B 1.
Panel 902(3) Process Radiation Monitoring 2.
Panel 902(3)-li - RPS and PCI relays 3.
Panel 902(3) Power Range Neutron Monitoring The loss of both RPS buses will result in a reactor scram and a Group II and III isolation.
From this logic, the mechanical vacuum pump trips and SJAE suction valve will close.
A Group I isolation will not occur, since the essential service bus supplies power to channel B isolation relays.
In hot shutdowr., the follow-ing conditions existe normal feedwater, condensate, and level control are operable, and the main condenser is available to be used as a primary heat sink, the reactor can reach and maintain cold shutdown conditions. Loss of RPS power to the 902(3)-10 panel would isolate the Reactor Building Ventilation and Fuel Pool monitors. Loss of power to the Offgas SJAE Radiation moni-tors will start the 15-minute isolation timer.
The timer can be reset to prevent an off-gas isolation so the main condenser can remain available. Loss of power to the 902(3)-37 panel will re-sult in a loss of Power Range Neutron monitoring, but with the reactor shutdown, it is not needed.
It will also cause a loss of Recirculation Loop Flow instrumentation; however, pump speed, jet pump flow, and total core flow instrumentation will still be operable and Recire. Pumps will be running at minimum speed. All ECCS system will remain operable with a loss of RPS power.
C.
No modifications are proposed based en the above review.
Essential Service Bus (ESS)
The 120/240 VAC ESS is normally energized from an M-G set which is fed from 480 VAC Bus 29(39).
If the normal AC power should fail, the turbine building 250 VDC MCC 2(3) will provide power to the M-G set motor.
There is a power seeking automatic transfer switch to MCC 28(38)-2 if both of the AC and DC power sources are lost.
1.
'(Continued)
A.
Control Room alarms are:
- 1) ESS M-G Set AC Feed Trip
- 2) ESS M-G Set DC Feed Trip 3) 120/240 VAC ESS Service Bus on Emergency Supply 4) 120/240 VAC ESS Service Bus Voltage Low Indications located in the auxiliary electrical equipment room AC motor amps and voltage, DC motor amps and voltage, AC are:
generator amps and voltage, bus amps, voltage, and frequency.
The B and D Main Steam Line Radiation Monitors are powered by the ESS Bus.
Alarms that will come up are: Channel B reactor scram, channel B main steam high radiation, and Group I isola-tion Channel B trip, if ESS is lost. Alarms for loss of power to the process computer are: recire, flow limit, RPIS inoperr.-
tive, and low vessel water level.
B.
The following loads are connected to the ESS Bus:
Panel 2252(3) Generator Hydrogen and stator cooling Panel 902(3) Stack gas, off-gas Panel 902(3) Core Spray and LPCI System II Panel 902(3) Reactor Manual Control Panel 902(3) Core Spray sump pump Panel 902(3) Recire. Pump speed control, Channel B sensor relays and trip relays t
Panel 902(3) Off-gas valves, control panel Panel 90!(3) HPCI instrument poser supply Panel 902(3y SRM, IRM, APRM, RBM recorders and feedwater control Panel 902(3) Rod Worth Minimizer Computer Computer Main Feed Cabinet ComputerPeripheralandTtansducerPowb~r'SupplyCabinet i
s in.
Main Chimney satple vacuum pump
?f B and D Main Steam Line Radiation, monitors.
l l
's s,
Safety / Relief valve acoustic position monitors
. c.
7 Panels. 902(3)-3, 4, 5, and 6 - Control Room panels.
fl
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s
1.
B.
(Continued)
Panci 902(3) Procers Radiation Monitor Panel 902(3) PCI Channel B isolation relays Panel 902(3) RPIS relays Loss of ESS could eventually cause the reactor to be shutdown.
This would be due to a loss of vacuum resulting from the off-gas isolation and SJAE suction valve closure.
In hot shutdown, the following conditions exist:
narrow range GEMAC water level in-dication, reactor pressure, steam flow, and feed flow will still be available. There would be a loss of the feedwater level con-trol system, HPCI flow control, isolation condenser flow control, the feedwater pump minimum flow valves will fail open, narrow range GEMAC recorder, narrow and wide range Yarway level indica-tion, and recire. pump speed control and indication.
A Group 1 PCI would not take place due to the RPS Bus supplying power to Channel A isolation relays. The chimney activity re-corder would be lost; however, the chimney and SJAE monitors would still be available. Shutdown cooling, ADS, and all low pressure ECCS systems would still be operable.
One train of standby gas would also be available.
The ability to achieve and maintain a cold shutdown condition does not appear to be a problem, based on the inventory of water available, shutdown cooling, ADS, low pressure ECCS, and rod block and CRD scram functions would be operational. Other loads that would be lost are of no significance in placing and main-taining the reactor in cold shutdown.
C.
No additional modifications are proposed based on the above review.
2.
The existing emergency operating procedures have been reviewed.
These procedures include symptoms, action to be taken, and alarms, which are sufficient to restore power to the bus. Based on this re-view, no revisions are proposed.
3.
I.E. Circular No. 79-02 has been reviewed. The difficulties de-scribed by the circular were caused by a failure of solid state un-interruptible power supplies. The specific trouble was with the in-verters and static switches. A review of the items of concern listed by the circular as compared to equipment at Dresden Units 2 and 3 was made.
Since there is no equipment of the nature described by the circular, no action on any of the items to be considered is required at the present time. However, modifications are in progress to replace the ESS M-G Sets with static inverters. A copy of the circular was sent to Commonwealth Edison Company Station Nuclear Engineering De-partment (SNED). Those review items and recommendations given in the circular will be re-examined and implemented as necessary by SNED prior to completing the modifications.
ATTACII9TP 3 QUAD-CITIES UNITS 1 AND 2 RESPONSE TO IE BULLETIN 79-27 1.
Based on review of this Bulletin, the following buses are addressed in response to the Bulletin, for each unit:
Reactor Protection Bus A and B Essential Service Bus Instrument Bus 24/48 VDC Bus A and B Reactor Protection System (RPS) Bus A and B Each 120 V.A.C. RPS bus is supplied normally by an M-G set, which in turn is fed f rom a 480 V Motor Control Center (MCC 18-2 and 19-2 for Unit 1, MCC 28-2, 29-2 for Uni t 2). These MCC's are supplied from emergency 480V buses 18 and 19 (28 and 29), which may be fed from their respective emergency diesel generators.
A reserve supply to each RPS bus exists from 480V MCC 15-2 (25-2).
This reserve supply is interlocked with the normal supply by use of a keylock switch to prevent simultaneous feed from both sources.
A.
Loss of power to either RPS bus, even momentarily, will give a half-scram condition, and partial Groups 11 and til primary containment isolations (PCI). Control Room alarm CHANNEL A(B) MANUAL SCRAM would annunciate, indicating loss of power to the A(B) RPS bus.
Numerous other control room alarm indications would be present, including all of those associated with the particular RPS trip system that was de-energized.
If both RPS buses are lost on the unit, a full reactor scram will occur.
Group 11 and Group 111 PCI will also take place, as'will half the permissive for a Group I isolation.
Numerous control room alarms, as well as the reactor and turbine generator parameter changes associated with a scram, will more than adequately alert the operator to a loss of power to the RPS buses.
Indications exist in the Auxilairy Electrical Equipment Room for Bus Amps, Bus Volts, and Generator Vol ts.
B.
The loads on the RPS buses are as follows:
Bus IA(2A) - (1)
Process Radiation monitoring panel 901-10 (902-10)
(2) PCI Division I, relay panel 901-40 (902-40)
(3)
RPS' Division I relay panel 901-15 (902-15)
(4)
Power Range Neutron Monitoring panel 901-37 (902-37) l l
l
Bus IB (2B) -
(1) PCI Division 11 relay panel 901-41 (902-41)
(2) RPS Division il relay panel 901-17 (902-17)
(3)
Power Range Neutron Monitoring panel 901-37 (902-37)
(4)
Process Radiation Monitoring Panel 901-10 (902-10)
As mentioned above, loss of power to both of the RPS buses will result in a full reactor scram and Groups 11 and 111 isolations.
From this logic, a mechanical vacuum pump trip and SJAE suction valve closure will also occur. A Group i isolation will not occur, since the redundant power supply to the isolation relays will still be energized from the Essential Service Bus.
Further, the D.C. Solenoids for the MSIV's and the solenoids for the Primary Sample Valves fed from the Instrument Bur will remain energized, and the valves will remain open.
Thus, ability to achieve and maintain a cold shutdown condition is not impaired, since the reactor has been shutdown, all rods are inserted, normal condensate-feedwater and associated level control are available, and the main condenser is available as a primary heat sink.
All ECCS also would be available in this condition.
With the reactor in this condition, there is no need to rely on the power range neutron monitoring panel (901-37, 902-37).
Loss of power to panel 901-37 (902-37) will disable the Reactor Recirculation Loop Flow instrumentation.
This is of minimal concern, since the Recirculation Pumps would be at minimum speed.
Pump speed, Jet pump flow, and total core flow instrumentation would still be available to monitor Recirculation System performance.
Loss of RPS power to panel 901-10 (902-1 ould result in a Reactor Building Vent isolation, Vent Fan Trip,..
iBGTS Auto-Start from loss of power to the Reactor Building Vent and Fuel pool Radiation Monitors.
Loss of power to the Off-Gas SJAE Radiation Monitors will initiate the 15-minute isolation timer. The timer can be reset to inhibit an off gas isolation so the main condenser would remain available.
No Main Steam Line High Radiation Monitor Group 1 isolation trip will occur, since the B and D monitors are supplied from the Essential Service Bus.
The above evolutions do not affect the ability to achieve a cold shutdown condition.
A loss of a single RPS bus would be less significant, since redundant monitors would still be operating.
C.
No modifications are proposed based on the above review.
Essential Service Bus The 120/240 -V. A.C. Essential Service System (ESS) Bus is normally fed f rom MCC 18-2 (28-2), with a reserve feed from a M-G Set.
The M-G Set may be powered from 480 V.A.C. Bus 18 (28), or from 250 V.D.C. Bus 1 (2). An auto-bus transfer exists from MCC 18-2 (28-2) and the M-G Set in the event the MCC is'iost.
If A.C. power to the M-G Set is lost (i.e. loss of Bus 18 (28)) the D.C. Motor is energized to continue running the M-G Set.
t
A.
The following alarms persuant to the ESS Bus exist in the control room:
120/240 VAC ESS BUS LOW VOLTAGE ESS M-G SET A.C. FEED TRIP 120/240 VAC ESS BUS ON M-G SET ESS M-G SET D.C. FEED TRIP Since the B and D Main Steam Line Radiation Monitors are powered by the ESS Bus, Alarms will come up for CHANNEL B REACTOR SCRAM, CHANNEL B MAIN STEAM HIGH RADIATION and GROUP i ISOLATION CHANNEL B TRIP if ESS is lost. Alarms for loss of power to the process computer, recirc flow limit, RPIS inoperative, and low vessel water level will also come up.
Indications exist in the Auxiliary Electrical Equipment Room for the following:
AC Motor Amps and Volts Transfer Volts AC Generator Amps and Volts Frequency Bus Amps and Volts B.
The following loads are connected to the ESS Bus:
Control Room Panel 901-4 (902-4)
Control Room Panel 901-5 (902-5)
Turbine and Auxiliary Panel 901-7 (902-7)
Process Radiation Monitor Panel 901-10 (902-10)
RPS Division ll Relay Panel 901-17 (902-17)
FW and Recirculation Panel 901-18 (902-18 Hydrogen and Stator Cooling Panel 2251-7 (2252-7)
SBGT Local Panel 2212-29A (2212-298)
Main Chimney Instrument Rack 2212-5 RPIS Relay Panel 901-27 (902-27)
Computer Panel 901-45 (902-45)
Computer Main Feed Cabinet Computer Peripheral and Transducer Power Supply Cabinet FW Controls, Panel 901-5 (902-5)
Radiation Recorder, Panel 912-4 S P.M. IRM, APRM Recorders, Panel 901-5 (902-5)
Control Room Panel 901-3, (902-3)
Recirculation M-G Set Protection Auxillary Relay Panel 2201-25A (2202-25A)
HPCI Flow Control Unit 2340-1 Main Chimney Sample Vacuum Pump Control Room Panel 901-6 (902-6)
Feedwater Instrument Rack 2251-9 (2252-9)
B and D Main Steam Line Radiation Monitors HPCI Signal Converter 2386 Off-Gas Panel 901-54 (902-54)
Safety / Relief Valve Acoustic Position Monitor
A total loss of ESS for a sustained period of time is very unlikely due to the diverse backup power sources available, and the reliability of these sources.
These sources are switched over automatically, and the bus is intended to remain in continuous service even if all other sources of A.C. electrical power (including the diesel generators) should fall.
Both A.C. power supplies came from an emergency 480 V bus, supplied by a Diesel Generator. The 250 VDC source is reliable, since it comes from the Station Battery System.
A loss of ESS for a period of time will not directly cause a reactor scram, although a shutdown will probably occur from either reactor vessel low or high water level.
This would be due to the loss of the feedwater level control system. The feedwater pump minimum flow valves will also fall open.
Reactor water level narrow-range GEMAC indication will be available, but the associated level recorder and YARWAY narrow and wide-range indicators will not.
Local manual operation of the feedwater regulating valves could still be accomplished.
Reactor pressure, feedwater flow, and steam flow int! cation would still be available.
The recirculation pumps' speed control system and indication would be lost.
HPCI and RCIC flow control devices would be unavailable.
No PCI would take place, although half of the logic permissive would be satisfied. An Off-Gas isolation and SJAE suction valve closure would occur. The chimney activity recorder would be lost, but the chimney and SJAE monitors would still be available. Although one SBGTS train would be unavailable, the redundant train would be available.
ADS and all low pressure ECCS would be intact and available, as would the Shutdown Cooling Mode of RHRS.
Of relatively minor significance in achieving cold shutdown, the following items would not be available:
RCIC testable check valve test feature CRD flow control (Scram function not affected)
APRM & RBM indication lights SRM, IRM, APRM recorders (Indication would still be available).
Turbine overspeed trip test feature Stator cooling and Seal Oil local instrumentation (Runback circuit not affected)
RPIS, Rod Select, RWM Off-Gas system instruments and valve indications RHR SW instrumentation Process computer Recorders for feedwater flow, steam flow, & reactor pressure (Indicators still available)
Based on the availability of water for the vessel, the availability of ADS and low pressure ECCS, the operability of CRD scram and rod block functions, the initial availability of the main condenser, and the use of Shutdown Cooling, a sustained loss of ESS, although extremely improbable, would not effect the ability of the reactor to achieve a cold shutdown condition.
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C.
No additional modifications are proposed based on the above review.
lNSTRUMENT BUS The 120/240 V.A.C. instrument bus is noramily fed from MCC 18-2 (28-2), with a reserve supply from MCC 15-2 (25-2).
There is an automatic transfer to the i
reserve supply upon loss of the normal feed.
A.
Alarms exist for the following in the Control Room:
120 VAC INSTRUMENT BUS LOW VOLTAGE 120 VAC INST. BUS TRANSFER TO EMERGENCY SUPPLY Bus voltage indication is available at the bus cabinet in the auxiliary electrical equipment room. Alarms would likely come up indicating heater drain valve closure, MSDT and moisture separator high level, and 24/48 VDC battery charger trip upon loss of the instrument bus.
B.
The following loads are connected to the instrument bus:
Rod control relay panel 901-28 (902-28)
Area radiation monitors, panel 901-11 (902-11)
Generator voltage regulator cubicle Protection relay panel 901-29 (902-29)
Process instruments, panel 901-19 (902-19)
Cleanup system instrument rack 2201-2 (2202-2)
Containment cooling benchboard 901-3 (902-3)
Area leak detection temperature monitoring panel 901-21 (902-21)
EHC panel 901-31 (902-31)
Control Room Panel 901-4 (902-4)
Control Room Panel 901-5 (902-5)
Feedwater and recirculation panel 901-18 (902-18)
Accumulator panels 2201-16 & 20 (2202-16 & 20)
Turbine panel 901-7 (902-7)
SRM/lRM drive control panel 2201-14 (2202-14)
Jet pump panel 901-38 (902-38)
HPCI panel 901-39 (902-39) 24/48 VDC Battery Chargers A and B FW heater racks 2251-14A, 14B, 16 (2252-14A, 14B, 16)
Process radiation monitors & panel 912-4 Radwaste control panel 2212-4 ECCS relay panels 901-32 & 33 (902-32 & 33)
Pressure suppression panel 901-3 (902-3)
Recire. M-G Set panels 2201-25A & B (2202-25 A. & B)
Annunciator input relay cabinet 901-34 (902-34)
Oxygen Analyzer panel 912-7 345 KV meter panels 912-400 & 912-402 345 KV frequency recorder, panel 912-2 Service building telephone room service PCI panels 901-40 & 41 (902-40 & 41)
s 125 VDC turbine bldg panel IA (2A) ground detection Recirc sample valves A0-220-44 and A0-220-45 Control Room Fire Protection HVAC panel 2212-89 Control Room Panel 901-8 (902-8)
Panel 2251-45 (2252-45)
Panel 2251-45 (2252-45)
Heating boiler pressure indicator, panel 912-5 Refuel bridge telephone FW regulating valves' position indication Off gas panel 901-54 (902-54)
Relief and safety valve acoustic position monitors A complete loss of the instrument bus would not directly cause a reactor scram, but would likely cause a loss of all low pressure and high pressure feedwater heater level control. The normal drains would fall closed, and the extraction steam dump valves would open.
This would probably result in a high moisture separator level turbine trip and subsequent reactor scram.
Of added significance is that the reactor manual control system would incur rod blocks,and indicating lights for accumulator trouble, scram, and scram discharge volume valve position would be lost.
Scram could be verified from the rod position indication system and a power decrease.
Indications in the control room for feedwater regulating valve position, feedwater flow, steam flow, and GEMAC reactor water level would be lost. The feedwater controllers, regulating valves, and both narrow range YARWAY level indications would be avaliable.
Of significance is the loss of the 24/48 V.D.C. battery i
chargers. However, the batteries themselves would provide their designed function.
Numerous other indications would be unavailable, such as RHR flow, Core Spray flow, Core i
Spray pressures, wide-range reactor water levels, drywell 1
pressure, suppression chamber pressure, suppression chamber level, recirc pump and M-G set temperatures, CRD pressures and flows, Jet pump flows, recirc pump seal pressures, cleanup flow and temperature, cleanup conductivity, recirc pump DP and flows, etc.
Both SBGTS trains would start and the reactor building vent system would isolate.
The recirc sample valves 220-44 and 220-45 would go closed and the TIP ball valves would close, if open. The reactor building-to-suppression chamber vacuum breakers would open, but in-line check valves would preclude venting the suppression chamber to the reactor building atmosphere.
Although many indications would be lost, the ability to place the reactor in a safe cold shutdown condition would not be impaired. Normal feedwater, the shutdown cooling mode of RHRS, ECCS, and the main condenser heat sink would be available.
No PCI would take place, and the ability to
shutdown the reactor would remain intact.
Since the YARWAY level instrumentation would be available, close monitoring of the reactor vessel level could still be accomplished. Of less relative importance, the following items would be disabled upon loss of the instrument bus:
Generator ground detection Indication for HPCI drain valves Test feature for HPCI and RHR testable check valves Area radiation monitors Turbine Lift Pumps Pressure / level monitoring of CRD accumulators SBLC tank level indication Condenser Seal trough valves Condensate make-up pump auto-start feature Area leak detection Reset feature of Group 1, ll, and lil PCI SJAE suction valve position indication Process radiation recorders (indicator and trip units would still be available)
Cleanup drain flow regulator Control Room Vent Isolation feature Makeup Demineralizers Stack gas sampling Radwaste Instrumentation and Valves A0 5406 valve position C.
No modifications are proposed based on the above review.
24/48 V.D.C. Buses A.
The 1A (2A) and IB (2B) distribution panels are supplied by the 24/48 V.O.C. batteries and battery chargers.
Each battery is rated a t 80-ampere hours. Voltage indication is provided in the Control Room. An alarm exists in the Control Room for battery undervoltage.
Alarm indication for neutron monitor low supply voltage would come up in the event of a loss of 24/48 VDC.
Local Indications exist in the Unit 1(2) Battery Charger Room for:
Charger Volts and Amps, Bus A Positive and Negative Volts, and Bus B Positive and Negative Volts.
B.
The following loads are connected to the 24/48 V.D.C. system:
Startup Range Neutron Monitoring (SRM/lRM) Panel 901-36 (902-36)
Process Radiation Monitor Panel 901-10 (902-10)
Stack Gas Monitor Panel 912-4 Loss of the entire 24/48 V.D.C. system will disable the process liquid radiation monitors (RBCCW, Service Water, Radwaste Effluent)
and the main chimney effluent monitors.
Since the trip logic for the SJAE off gas radiation monitors comes from the 24/48 VDC System, the isolation function from high radiation would be disabled.
However, the Main Steam Line Radiation Monitors and trips would be available, as would indication from the SJAE monitors.
Loss of the 24/48 V.D.C. system will also disable the SRM and IRM Systems.
If not in the RUN Mode, this will de-energize the associated IRM protective relays and cause a reactor scram. The indications, recorders, and lights would also be lost.
Loss of the' entire system is very unlikely, and a partial system loss (A or B) would have minimal implications as far as obtaining a cold shutdown condition.
Even for a complete 24/48 V.D.C. system loss, the reactor can still be brought to a cold shutdown condition due to the availability of normal feedwater, ECCS, the main condenser, reactor normal control, and the shutdown cooling mode of RHRS.
C.
No modifications are proposed based on the above review.
2.
Emergency operating procedures exist pertaining to loss of power to the aforementioned buses. These procedures include appropriate symptoms, alarms, and operator actions to be taken to restore power to the appropriate bus. Based on the review performed in response to item 1 above, procedure revisions will be made to more clearly give the use of alternate indications and circuits from other buses. These revisions will also increase the scope of symptoms and operator actions, based on the findings and reviews performed persuant to item 1.
Procedure revisions will be implemented by April 1, 1980.
3 IE Circular No. 79-02 has been reviewed.
SCI inverters do not exist at Quad-Cities Station.
However, modifications had been initiated prior to issuance of the Circular to replace the ESS M-G Sets with static inverters, and to install an inverter to power the Station process computer.
These modifications had been issued to upgrade the 120 V.A.C. ESS system to improve its reliability, and to add a measure of flexibility to the system.
j Af ter having initially received circulation 79-02, a copy was sent to the 4
Commonwealth Edison Company Station Nuclear Engineering Department, who was in the process of designing and procuring the inverters in accordance with the modifications. At present, the design and procurement of the new inverter systems is being finalized. Those review items and recom-mendations given in Circular 79-02 will be re-examined and implemented as necessary prior to completion of the modifications and placing the inverters into service.
c
,-r--
ATTAC1 DENT 4 Response to IE Bulletin 79-27, Zion Station Units 1 and 2 The subject bulletin related a problem which occurred when an instrument inverter tripped and failed to auto transfer. The bulletin requested four specific actions by operating plants.
1.
Review all instrument and control feeds:
Zion Station has completed a detailed review of the Unit 1 Instrument buses by following all the wiring drawings from the respective breakers on each instrument bus and identifying all the loads indicated by the physical wiring drawings. The loads were checked for correctness by cross correlating the wiring drawings with the instrument loop schematics. In addition to this an independent review and tabulation of the loads is being conducted by Station Electrical Engineering Department Personnel in the General Office. When their review is completed it will be compared with the list's developed by Zion Station Electrical Group. This process will insure that all loads are correctly identified and an accurate load list will be available for operator use. Verification that Unit 1 is in fact typical of Unit 2 is still in progress. To date only very minor differences have been detected between Unit 1 and Unit 2 This review of Unit 2 should be completed in about one month.
The symptoms of a loss of instrument bus are extremely obvious to the operator.
Instantaneously approximately one fourth of all the annunciators for the respective Unit will alarm.
All Reactor Protection Status Lights and Safeguards status lights from the affected bus go out along with the power supply lights for the affected channel. The power supply lights key the operator to which bus has been lost. The review has shown that a loss of a single instrument bus would not cause a reactor trip or Safety Injection nor prevent an actual reactor trip, Safety Injection, or bringing the pl. ant to cold shutdw n.
As a result of this review and because of the design require-ments for redundant and diverse signals for reactor protection and safeguards which originate from instruments provided from these buses no modifications are deemed necessary at this time.
2.
'Preoare emergency procedures and review procedures required to achieve cold shutdown:
An abnormal operating procedure is being developed and will be implemented by mid April to give the operator guidance as to how to reenergize the bus and directs him to the list for each specific bus which contains a section on the effects
.of the loss of that bus on the overall plant. On a complete and sustained' loss of an Instrument Inverter, Zion Station Instrument Buses can be energized directly from bus 137, 138, 139,.& 133 through manually operated breakers located in the ~ instrument distribution cabinet. As a result of this additional source of power for the instrument buses and this review, no modifications are planned.
3 Re-review IE Circular 79-02:
The IE Circular 79-02 has been reviewed with respect to this bulletin and no changes are deemed necessary.
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