ML19345G439
| ML19345G439 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 04/02/1981 |
| From: | Nichols T SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8104070249 | |
| Download: ML19345G439 (9) | |
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T SOUTH CAROLINA ELECTRIC a GAS COMPAN/
Post orrect som 7s4
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CotuMelA, SOUTH CAROLINA 2921e
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T.C.NICHOLs Jn.
April 2, 1981 4
%ct Ps tSetMF amp O#OUP DECOMWE h
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19ettan Openatens 5
'1PR o c ;ggy j s Dt y
'b Mr. Harold R. Denton, Director
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' Office of Nuclcar Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.
20555
Subject:
Virgil C. Summer Nuclear Station Docket No. 50/395 SER - Confirming Issue 1.7.13 (1)
Degraded Grid Voltage
Dear Mr. Denton:
' The attached change' to FSAR ' Chapter 8 ' provides the information requested by Mr. Om Chopra regarding degraded grid voltage. This should
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provide sufficient material to reuolve SER. Issue 1.7.13 item 1.
This material will be. included in'the next FSAR amendment.
If you have any' questions, please let us know.
Very truly yours,
[
,gg T. C. Nichols,'Jr.
.RC:TCN:pj.
Attachment CC:
V. C. Summer w/o.att.
.G. H. Fischer w/o att.-
T. C' Nichols,- Jr. w/o att.
C. A. Price w/att.
D.-A.-'Nauman w/att.
W.,A.; Williams, Jr. w/att.
iR. B. Clary w/att.
-A. R. Koon w/att.
TA.-A.'. Smith w/att.
-H. N. Cyrus w/att.
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4 (J. B. Knotts,.Jr. w/att.
-J. L. Skolds w/att.
L-B. A'. Burs'ey w/att.
=0.~S.:Bradham w/att.-
ISEG-NPCF/Whitaker'
' File' 1 PRS' l810407.0 M t
are established, closes the emergency power source circuit breaker. 'In the case of a. safety injection signal and/or ESF bus undervoltage, the w'
ESF loading sequencer (see Section 7.3.1 for a detailed discussion) 5-
. trips selected bus loads including all non-class IE loads. The bus is t
then reloaded in the sequence shown in Table 8.3-3.
Items indicated by zero second Icading sequence in Table 8.3-3 are not tripped and, there-fore, are ic=rediately loaded when the emergency power source circuit (g
breaker is closed. All other required loads are loaded in sequence by 1
lthe ESF loading sequencer.
loss The'7.2 Kv ESF buses are each provided with three Q of voltage
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'M relays set at Approximately 80 percent of the nominal bus voltage 1cvel and three degraded voltage relays set at approximately 91.34 percent of the nominal. bus voltage level. Operation of a set of loss of voltage or
' degraded. voltage relays will initiate a diesel generator start, a per-missive for EFW turbine pump start, an engineered safety features load sequence operation and a permissive for diesel generator circuit breaker close. These operations occur in a timed sequence as outlined in' Table 8.3-5.
The: logic of the controls are illustrated in Figure 8.3-0a.
M As illustrated in Table 8.3-5 the 7.2 Kv bas circuit brea'Aers are tripped @. econds'after the diesel generator is started on a degraded 24 Z6 voltage condition as comparedito seconds for.a loss of voltage
- condition. The delay in.. tripping for a degraded voltage condition allows the' bus to be energized during the time the diesel generator is coming up to speed. 'Therefore, with the degraded voltage condition the maximum dead bus.tir.e is seconds as compared.to a 10.25 seconds O
c.
- dead bus time allowed for a'less of voltage condition.
M
- Appendix 8%
provides a discussion of;the time sequence of equipment operation with' a'. degraded voltage condition coincident wix-an accident
. Appendix'.to be provide'd later). - When the diesel generators -
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( cond i ti on.-
are started and loade'd as'a result of an undervoltage condition, the ESF
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-8.3-9 AMENDMENT 86
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'May m,.1981 4
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TABLE 8.3-5 Sacuence of Operation Following a Loss or Degraded Voltage Condition Loss of Degraded G"
Items of Voltage Voltage Operation' Time in Seconds J
Loss or Degraded Voltage Condition 0
0
- Diesel Generator Start 0.25 3
i Permissive to EFW Pump Start 0.25 3
Initiate ESFLS Operation 2.25 0![~[
. 7.2Kv Bus Circuit
~ Breaker. Trip 2.25 jh[}]P Permissive to Close Diesel
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l[k /0 Generator Circuit Breaker -
5.25 O'
- Diesel Generator
- Ready to Load-(Initiate Block Loading) 10.25 13 h
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- - 1 8.3-55 AMENDMENT N d Aj Sy MancH,-1981
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APPENDIX SF STARTING SEQUENCE OF ESF EQUIPMENT FOLLOWING AN ACCIDENT COINCIDENT WITH A DEGRADED VOLTAGL CONDITION INTRODUCTION The following study identifies the tired sequence of starting the ESF system equipment for an accident coincident with degraded voltage on the offsite power system.
The accidents considered are (1) Loss of Coolant Accident (LOCA) and (2) Main Steam Line Break (MSLB).
The study compares the equipment starting times during accident conditions, with a degraded voltage to the starting times assumed in the accident analyses with total loss of voltage. See tables 1 and 2.
DISCUSSION During these two accident scenarios the diesel generator will start when safety injection is initiated at time zero. A maximum of 10 seconds is then re-quired for the generator to reach the speed and voltage necessary to connect to the ESF buses.
The degraded voltage relays are set to actuate at 91.34% of nominal voltage.
If-the voltage drops below 80% of nom
- 21, the undervoltage relays will actuate.
A time delay of 3 seconds is provided before the degraded voltage relays signal the' diesel to allow for voltage dips caused by a large motor starting.
- However, it should be noted that for these accidents the diesel was started at time zero by safety injection; therefore the signal to start the diesel generated by the degraded voltage relay is duplicative. lf the degraded voltage condition persists for 4 more seconds (now a total of 7 seconds), the 7.2 kV ESF buses are cleared.
An additional time delay of 3 seconds is then provided to allow residual motor voltage to decay.
CONCLUSION Under the accidents discussed here, a maximum of 10 seconds is req'uired before the diesel generator can be connected to the ESF buses. However, if there is no accident and a degraded voltage condition exists, a maximum of 13 seconds would be required before the diesel is connected.
8F-1 AMENDMENT 26 MAY, 1981
}
l TABLE 1 DEGRADED GRID VOLTAGE COINCIDENT WITH LOCA TIME (Saconds)
DESCRIPTION OF EVENT 0
Degraded voltage condition en 7.2Kv ESF Busses
{
Loss of Coolant Accident (S.I. Signal - Start Diesel Get erator signal).
3 Degraded voltage detection signal.
7 Clear 7.2Kv ESF bus (Trip inec=ing and feeder breakers).
10 Close Diesel Generator breaker.
Start load block #1 (Start SI/ Charging Purp, Start opening valves).
12 SI/ Charging Pu p at full speed ( % 2 sec starting time).
(25.57)-Note 1 15 Start RHR Purp.
19 RHR Pu=p at full speed (% 4 sec starting ti=e).
_ (25.57)-Note 1 20 Start S. W. Pump.
Start Chilled. Water Purp.
22 Safety Injection related valves at their final position (25.57)-Note 1 (12 see travelling time per FSAR, Section 15.4.2.1.2.1, page 15.4-31).
24.5 S. W. Pump at full speed ( %4.5 see starting time).
(60)-Note 2 2S' Start Co=ponent Cooling Pump.
Component Cooling Pump at full speed ( %4 see starting tire).;
1 30 Start Emergency Feedwater Purp.
j 35 Start Reactor Building Cooling Units.
Start Fuel Handling Building Exhaust Fan.
40 Start S. W. Booster'Pu=p.
42~
Emergency Feedwater Pump at Full Speed. (%12 see starting
-(60)-Note 3-time) i SF-2 AMEhTENT 26 MAY, 1981
TABLE 1 - (Continued)
DEGRADED GRID VOLTAGE COINCIDENT WITH LOCA TIME (Seconds)
DESCRIPTION OF EVENT 43 Reactor Building Cooling Units at full speed and air (43)-Note 4 flow has reached operating values (8 sec delay frc=
time of starting the fans to the time of having reached operating values of air flow per FSAR, Section 6.2.2.2.2.2, page 6.2-58) 45 Start HVAC Chiller.
S. W. Booster Pump at full spped (5 sec starting tice per FSAR, Section 6.2.2.2.2. 2, page 6.2-59).
NOTES:
'l.) -Per FSAR Table 15.4-1, page 15.4-96.
2.)
Critical case is the requirement to provide cooling water to the Diesel Generator within 1 minute from the time of starting.
3.)
Per FSAR, Section 15.4.2.2.2.1, page 15.4-44
' 4.)
Per FSAR, Section 6.2.1.3.4.3, page 6.2-20a.
AMENDMENT 26 8F-3 MAY, 1981
TABLE 2 DEGRADED GRID VOLTAGE COINCIDENT WITH MSLB TIME (Seconds)
DESCRIPTION OF EVENT 0
Degraded voltage condition on 7.2Kv ESF Buss on Main Steam Line Break Accident (S.I. Signal -
Start Diesel Generator signal).
3 Degraded voltage detection signal.
7 Clear 7.2 Kv ESF 'cus (Trip incoming and feeder breakers).
10 Close Diesel Generator breakar.
Start load block #1 (Start S1/ Charging Pump, Start
-opening valves).
12 SI/ Charging Pump at full speed (%2 sec starting time).
(22)-Note 1 15 S tart RHR Pump.
19 RHR Pump at full speed (N4 see starting time).
(22)-Note 1 20 Start S. W. Pump.
Start Chilled Water Pump.
22 Safety Injection related valves at their final position (22)-Note 1 (12 see traveling time per FSAR, Section 15.4.2.1.2.1, page 15.4-31).
24.5 S. W. Pump at full speed (%4.5 see starting time),
(60)-Note 2 25 Start Component Cooling Pump.
29 Component Cooling Pump at full speed (14 see starting time).
30 Start' Emergency Feedwater Pump.
35 Start Reactor Building Cooling Units.
Start Fuel Handling Building Exhaust Fan.
40 Start S. W. Booster Pump.
42 Emergency Feedwater Pump at full speed. (%12 sec starting (60)-Note 3 time)
SF-4 AMENDMENT 26 FMY, 1981
TABLE 2 - (Continued)
DEGRADED GRID VOLTAGE COINCIDENT WITH MSLB TIME'(Seconds)
DESCRIPTION OF EVENT A 43 Reactor Building Cooling Units at full speed and air (43)-Note 4 flow hcs reached operating values (8 sec delay from time of starting the fans to the time of having reached operating values of air flow per FSAR, Section 6.2.2. 2. 2.2, page 6. 2-58).
45 Start HVAC Chiller.
S. W. Booster. Pump at full speed (5 see starting time per FSAR, Section 6.2.2.2.2.2, page 6.2-59).
. NOTES:
' 1.)
Per FSAR, 'Section -15.4.2.1.2.1, page 15.4-31.
2.). : Critical case is. the requirement to provide cooling water to the Diesel
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- Generator within l minute from the. time of starting.
3.). Per FSAR, Section-15.4.2.2.2.1,.page 15.4-44.
4.)
Per FSAR, Section-16.2.1.3.4.3,, page 6.2-20a.
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AMENDMENT'26-MAY,11981-c' s
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