ML19305B843
| ML19305B843 | |
| Person / Time | |
|---|---|
| Site: | La Crosse File:Dairyland Power Cooperative icon.png |
| Issue date: | 09/27/1977 |
| From: | Milos R NUCLEAR ENERGY SERVICES, INC. |
| To: | |
| Shared Package | |
| ML19305B840 | List: |
| References | |
| NES-81A0028, NES-81A28, NUDOCS 8003200468 | |
| Download: ML19305B843 (23) | |
Text
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SAFETY EVALUATION AND COMPLIANCE WITil NRC STAFF POSITIONS RELATIVE TO Tile LACBWR EMERGENCY POWER SYSTEMS Prepared under Project 5101 for the DAIRYLAND POWER COOPERATIVE
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NUCLEAR ENERGY SERVICES, INC.
Danbury, Connecticut 06810 Prepared by:
Approved by:
V.
P.
Enginndring h
I Q. A. Ma dger v
?~ 27' 77 Date:
8003200Lb3
TABLE OF CONTENTS Page 1.
INTRODUCTION.
1-1 2.
DESCRIPTION OF THE LACBWR ONSITE POWER SYSTEM 2-1 3.
COMPARISON OF THE LACBWR EMERGENCY POWER SYSTEMS WITH THE STAFF POSITIONS 3-1 4.
PROPOSED PLANT MODIFICATIONS 4-1 5.
PROPOSED CHANGES TO THE LACBWR TECHNICAL SPECIFICATIONS 5-1 6-1
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6.
REFERENCES t
APPENDIX A - Test Procedures for the Annual Tests of Emergency Diesel Generators lA and 1B 4
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1.-
INTRODUCTION NRC has requested DPC to compare the LACBWR onsite power distribu-tion system with the new Staff Positions delineated in Reference 1.
The following evaluation was made to provide the required comparison and in addition to provide a brief description of the LACBWR emer-gency power systems, proposed changes to the power distribution sys-tem, and proposed changes to LACBWR's Technical Specifications.
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2.
DESCRIPTION OF THE LACBWR ONSITE POWER SYSTEM The LACBWR onsite power system is described in detail in References 2 and 3.
Figure 1 and the following brief description are provided to illustrate basic interconnection of the safety related buses and the operation of the undervoltage protection system.
Normally, the 440 volt Essential Bus lA is supplied from the 440 volt Bus lA, which recieves its power from either the offsite power sources or.the main station generator.
Under emergency conditions, the 440 volt Essential Bus lA is supplied by diesel generator lA.
Similarly, Essential Bus 1B is supplied from the 440 volt Bus 1B, or by its emergency source, diesel generator 1B.
Referring to Figure 1, the safety related buses at LACBWR are as follows:
(a)
Essential Bus lA (440 VAC)
(b)
Essential Bus 1B (440 VAC)
(c)
Turbine Bldg. Reg. Bus (120 VAC)
)
(d)
Non-Interruptible Bus lA (120 VAC)
(e)
Non-Interruptible Bus 1B (120 VAC)
(f)
Reactor Water Level, Chan. 3 Safety Bus (120 VAC)
(g)
Reactor Plant DC Bus (125 VDC)
(h)
Diesel Bldg. DC Bus (125 VDC)
(i)
Generator Plant DC Bus (125 VDC)
Buses (d) through (i) are considered non-interruptible and free from external causes of voltage degradation, since their normal sources of power from the Essential Buses are backed-up by on-line standby batteries.
Loads connected to these buses, therefore, will not be affected by temporary loss of voltage or voltage degradation, which may be experienced by loads connected to buses (a) through (c).
Bus (c) " Turbine Bldg. Reg. Bus" is fed from Essential Bus lA through a voltage regulating transformer and, therefore, has some built-in protection against voltage degradation.
Only buses (a) and (b), the 440V Essential Buses, would be directly affected by voltage fluctua-tions in the offsite power system.
Referring to Figure 1, one set of undervoltage relays for each Essen-tial Bus provid2s the two required levels of undervoltage protection (i.e. protection against complete loss of voltage and degraded voltage).
Figure 2 shows the variable voltage and time delay characteristics of the undervoltage relays used at LACBWR.
Presently these relays U
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w OFFSITE POWER OR MAIN STATION GENERATOR h
h 2400v Bus lA 2400v Bus 1B dM (Tm nFT) 440v Bus lA 440v Bus 1B O 452 452 Oj l
l O 52A 52B O/
440v ESS Bus lA 440v ESS Bun 1B EV LAAAJ Ldn d U/V Relays U/V Relays Y""
427 EAXA/C 427 EBXA/C I
g Diesel ProrIosed ~l 6)roposed 1
Dicsol
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U/VRelaysj U/V Relays Gen 1B
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Gen lA
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l Reactor Plant Diesel Bldg Gen Plant 125 VDC Bus 125 VDC Bus 125 VDC Bus or l
Turb Bldg 120 VAC Non-Interruptible Non-Interruptible RX LVL III Regulated Bus 120 VAC Bus IA 120 VAC Bus IB 120 VAC Bus l
t Onsite Power Distribution System Within Broken Line FIGURE I--SIMPLIFIED SKETCH OF THE LACBWR ONSITE POWER DISTRIBUTION SYSTEM
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82v & 2.5s (Relay setpoints) 10
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FIGURE 2 TRIP TIME DELAY VS BUS VOLTAGE 1
I EXISTING HELAYS 1
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o 80 160 240 320 400 480 -
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BUS VOLTAGE l
2-3 l
have their setpoint dials adjusted to 82 volts and 2.5 seconds.
Note that 82 volts at the relay is equivalent to 328 volts on an Essential Bus, since the relay is connected to its Essential Bus through a four to one stepdown transformer.
With these setpoints I
the relay will start timing when the bus voltage drops to 328 volts or less and, on a complete loss of voltage, the relay will trip in 2.5 seconds or less.
The trip time varies with voltage as can be seen from Figure 2.
Operation of the 440 volt Essential Bus lA undervoltage protection system is as follows:
Essential Bus lA undervoltage relays, 427EAXA and 427EAXC, are arranged in one out of two coincidence.
When the low voltage / time delay trip combination is reached on either relay, feed breader 452-52A opens and diesel generator lA starts automat-ically.
After the latter reaches rated voltage and frequency, breaker 452-EGA closes and supplies power to Essential Bus lA.
Essential Bus 1B relays and breakers operate similarly.
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3.
COMPARISON OF THE LACBWR EMERGENCY PONER SYSTEMS WITH THE STAFF POSITIONS
- 1) Position 1: Second Level of' Undcr-or-Over Voltage Protection uith a Time Datay.
We requ1.rc that a second level of voltage protection for the onsito pouer system be provided and that this cecond icvel of voltage protection chall catisj'y the follouing critoria:
a) The selection of voltage and time cet points shall be determined from an analysis of the voltage requirements of the safety-related loads at all onsite system distribution icvels.
As a result of this evaluation, LACBWR will provide a second set of undervoltage relays, which will complement the relays currently in to provide better degraded voltage protection.
Additionally,
- use, the existing set of undervoltage relays will have their set points
" changed from 82 volts /2.5 seconds to 93 volts /2 seconds.
The new set of undervoltage relays will be set to trip at 100 volts with a time delay of 9 seconds.
These new characteristic curves and the resultant combination are plotted in Figure 3.
Note from Fig-
}
ure 3 that the existing relay's trip time varies with bus voltage, whereas the new relay's trip time is independent of bus voltage.
Note also that the corresponding bus voltage is four times the relay voltage set points, since the relays are connected to their buses through four to one stepdown transformers.
Either set of under-voltage relays per Essential Bus will have the capability of auto-matically starting the emergency diesel generator and transferring its Essential Bus from offiste power to the emergency source.
The basis for the new set points, which primarily alter the allow-able degraded voltage conditions, was to select a voltage high enough to operate all ECCS equipment without damage, but low enough and with a long enough time delay to eliminate false tripping (e.g. due to starting large motors).
Tests at LACBWR show that Essential Bus voltage drops to approximately 400 volts (equivalent to 100 volts at the undervoltage relays) for a few seconds when starting a feed-water pump or the reserve exciter.
Other tests by DPC personnel showed that typical 120-volt control relays'used at LACBWR will operate at 75 to 93 volts and motor starter relays will operate at 82 volts.
The high pressure core spray pumps are expected to oper-ate at 10% less than their nameplate voltage of 440 volts.
The degraded voltage trip point of 100 volts (400 volts on the Essential Buses) is at a higher voltage level than that at which all vital electrical equipment is expected to operate without damage.
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Hb 93v & 2s (Relay setpoints)
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2.
FIGURE 3 TRIP TIME DELAY'~'
VS BUS VOLTAGE l'
PROPOSED RELAY ~
COMBINATION O
80 160 240 320 400 480
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BUS VOLTAGE I
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b) The voltage protcetion chall include coincidence logic to preclude
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spurious trips of the offaite power cource.
The second level of voltage protection will consist of three under-voltage relays for each Essential Bus (one relay per phase).
The relays trip contacts will be arranged in a two out of three coin-cidence logic to preclude spurious trips.
1.
c) The time delay colected shall be based on the follouing conditions:
(1) The allouable time delay, including margin, shall not exceed the maximum time delay that is asswned in the FSAR accident analyses; (2) The time delay shall minimize the effect of short duration disturbances from reducing the availability of the offsite pouer source (s); and (3) The allocabic time duration of a degraded voltage condition at all distribution cystem levels shall not result in fail-ure of cafety systems or components.
(1)
The ECCS safety analysis assumed a 20 second time delay from the simultaneous loss of offsite power and LOCA to the start-ing of a high pressure core spray pump.
Either diesel gen-erator at LACBWR is capable of coming up to operating voltage and frequency within 10 seconds of its start signal.
The
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allowable undervoltage relay time delay, including mar-in, is within the remaining 10 seconds.
(2)
The nominal time delay of nine seconds at 100 volts is con-sidered sufficiently long to minimize the effect of short duration disturbances (e. g. starting large motors).
(3)
As stated earlier in Section 2 of this evaluation, the only safety related buses which could be directly affected by degraded voltage conditions are both Essential Buses. 'All other safety related buses (see Figure.1) are protected against degraded voltage conditions by non-interruptable power sources or by a voltage regulator.
The only safety equipment fed directly by the Essential Buses which must be protected from excessive degraded voltage conditions is the high pressure core spray pumps.
The latter are expected to operate at less than 10% of their nominal voltage for con-siderably longer than the proposed time delay of nine seconds.
The allowable time duration of degraded voltage on the safety related buses will not, therefore, result in failure of safety components.
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d) The voltage monitors shall automatically initiate the disconnection
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of offsite poucr sources uhonever the voltage act point and time dalay limits have been exceeded.
Whenever their coincidence logic indicates that the voltage set point and time delay limit have been exceeded, the new undervoltage relays monitoring Essential Bus lA, will disconnect the latter from the offsite power source by automatically opening feed breaker 452-52A.
Similarly, the new undervoltage relays monitoring Es-sential Bus 1B, will disconnect this bus from the offsite source by automatically opening feed breaker 452-52B.
1.
c) The voltage monitors shall be designed to satisfy the requirements of IEEE Std. 279-1971, "Critoria for Protcetion Systems for Cuclear Pouer Gcncrating Stations.
The voltage monitors will be designed to satisfy the applicable re-quirements of IEEE Std. 279-1971.
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f) The Technical Specifications shall include limiting conditions for operation, surveillance requirements, trip set points with minim:ct and maximun limits, and allovable values for the second-level voltage protection monitors.
The Technical Specifications will be modified to include the appro-priate information.
See the proposed changes to the Technical
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Specifications contained in Section 4.
- 2) Position 2: Interaction of' Onsite Pouer Sources uith Load Shed Feat:c'a_
We require that the current system designs automatically prevent load shedding of the cmargency buses once the onsite sources are supplying pouer to all sequenced loads on the emergency buses.
The design shall also include the capability of the load shedding feature to be auto-matically reinstated if the onsite cource supply breakers are * 'pped.
The automatic bypass and reinstatement feature shall be verifwed during the periodic testing identified in Position 3.
In the event an adequate basis can be provided for retaining the load shed feature chan loads are energized by the onsita power system, ue vill require that the set point value in the Technical Specifications, uhich is currently specified as "... equal to or greater than... " be amended to specify a value having maximum and minimun limits.
The licensees' bases for the setpoints and limits celected must be documented.
At LACBWR both emergency and non-emergency loads are connected to the Essential Buses.
Emergency loads are defined as those required for emergency core cooling, containment isolation, reactor shutdown and post-accident monitoring instrumentation.
There is no auto-matic shedding of emergency loads on either Essential Bus whether
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the latter is supplied by the cmcrgency diesel generators or offsite Some of the non-emergency loads are shed, whenever their Es-I power.
sential Bus loses power, due to dropping out of their motor starter relays on low voltage.
These loads are not automatically sequenced when power is restored to the Essential Buses, however, if their reconnection is desired, this can be done manually.
Only one non-emergency load (i.e. Seal Injection Pump-1B) has an automatic re-connection feature after it is shed on loss of power.
Existing load shedding for all non-emergency loads at LACBWR will be retained whether the Essential Duses are supplied by offsite sources or by the emergency diesel generators, to insure that the diesel generators can restart the emergency loads which are not shed.
Refer to Tables 1 and 2 for a listing of Essential Bus loads and their load shedding status.
- 3) Position 3: Oncite Pover Source Testing We require that the Teobtical Specifications includa a tect requirement to demonstrate the full functional operability and independence of the oncite pouer coureco at icast once per 18 months during shutdown.
The Technical Specifications shall incitula a requirement for testo:
(1) cimulating loco of offsite pouer in conjunction uith a cafety injection actuation signal; and (2) cimulating interruption and cubsequcnt re-1 connection of onsite power cources to their recpective busec. Propar operation chall be deternined by:
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a)
Verifying that on loca of offsite pouer the cmargency bucec har; been de-energiced and that the loads have been ched from the emergency busec in accordance uith design requiremento.
b)
Verifying that on loco of offsite pouer the diccel generators start from ambient condition on the autostart signal, the cmargency buces are cnergiced uith permanently connected loads, the auto-connected cmergency loado are energiced through the load sequenece, and the cystem operates for five minutec chile the generatoro are loaded with the amargency loads.
c)
Verifying that on interruption of the ancito courecc the loado are ched from tha cmergency bucca in accordance with design re-quirementa and that cubacquent loading of the oncite coureco is through tha load sequencer.
Requirements as stated by Position 3 are satisfied by the " Annual i
Test of Emergency Diesel Generator lA" and the " Annual Test of Emergency Diesel Generator 1B."
Copics of these test procedures are attached to this evaluation in Appendix A.
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TABLE 1
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ESSENTIAL BUS 1A--LOAD SilEDDING STATUS Not Shed and Shed Shed Sequenced Emergency Core Spray Pump 1A X
Demineralized Water Transfer Pump 1A X
Shield Cooling Pump 1B X
Component Cooling Pump 1B X
Control Rod Nozzle Effluent Pump 1B X
1 Generator Plant Main Steam Shutoff Valve X
Backup Instrument Air Compressor X
Stack-Monitor Vacuum Pump X
Control Room Emergency Lights X
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125-Volt DC Reactor Plant Battery Charger X
Alternate Core Spray AC Motor-Operator 120 Volt Bus X
120-Volt AC Vital Loads 0 Turbine Building Bus X
Diesel Generator lA Battery Charger X
+
Off Gas Blower X
Control Rod Drive !!ydraulic Pump 1B X
Diesel Generator lA Radiator Fan Motor X
Diesel Generator lA Day Tank Fuel Oil Pump X
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TABLE 2 I
ESSENTIAL BUS 1B--LOAD SIIEDDING STATUS Not Shed and Shed Shed Sequenced Emergency Core Spray Pump 1B X
X Seal Injection Pump 1B a
Diesel Building Battery Charger X
d Diesel Generator Battery Charger X
X Static Inverter Domineralized Water Transfer Pump 1B X
29 Control Rod Drive Pump Motors X
X Shield Cooling Pump 1A 4
X Component Cooling. Pump 1A X
_) Vent Monitor Vacuum Pump X
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Decay IIcat Pump I
Control Rod Nozzle Effluent Pump 1A X
Reactor Level-Standpipe IIeaters X
l Control Rod Drive flydraulic Pump 1A X
X Relay Panel Emergency Lights and Receptables X
Diesel Building IIVAC Loads X
f Fuel Oil Transfer Pump Motors (2)
X X
Fuel Storage Well Pump 1B X
Radiator Fan Motor i
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4.
PROPOSED PLANT !!ODIFICATIONS i-There.are two proposed plant modifications which resulted from this evaluation:
1.
The first plant modification is to change the set points on the existing " type 427" undervoltage relays monitoring the Essential Duses.
The setpoints will be changed from 82 volts and 2.5 seconds to 93 volts and 2 seconds.
The change in the trip time delay vs trip voltage is shown by compar-ing Figures 2 and 3.
The reason for this change is to shorten the trip time for complete loss of voltage and to reduce the time vital equipment will be exposed to severe voltage degradation.
2.
The second plant modification is to add three new undervoltage relays to each Essential Bus.
These new relays will have set points of 100 vcits with a nine second time delay and will be arranged in two out of three coincidence.
The new relays in addition to the existing " type 427" undervoltage relays will provide the combined protection against degraded voltage con-J ditions, as shown in Figure 3.
Operat onally the new relays and the existing undervoltage relays will initiate the same sequence of events whenever the set points of either set of relays are exceeded.
This sequence for Essential Bux 1A is as follows:
Whenever the bus voltage drops to the volt-age set point for more than the allowable time delay on either set of undervoltage relays, automatic sequencing is initiated to start diesel generator lA and open feed breaker 452-52A.
The latter normally supplies offsite or statio.. generator power from the 440 volt Bus lA to the Essential Bus lA.
Imen the diesel generator comes up to rated voltage and frequency, breaker 452-EGA closes to connect the emergency diesel generator to its essentL.i bus.
The corresponding components on Essential Bus 1B operate similarly.
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PROPOSED CIIANGES TO Ti!E LACBWR TECllNICAL SPECIFICATIONS l
DPC. requests that the LACBWR Technical Specifications be amended to conform to the requirements of Reference 1.
A description of the proposed changes follows:
1.
Add the following paragraph (d) to existing Tech Spec 5.2.10.1.1.2.c.3:
(d)
Verifying that on diesel generator trip, the loads are shed from the emergency busses and the diesel re-starts on the auto-start signal, the emergency busses are energized with permanently connected loads, the auto-connected emergency loads are l
energized through the load sequencer and the diesel operates while its generator is loaded with the emergency loads.
I Note that the above requirement does not exist in the present LACBWR Tech Specs, however, similar specifications to nodel
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specifications 4.1.1.x.a.1 (a) and (b) of Reference 1 are presently included in the LACBWR Tech Specs as Specifications 5.2.10.1.1.2.c.3 (a) and (b).
2.
Add the following specifications 4.2.3.3 and 5.2.11.3 to the l
LACBWR Technical Specifications.
Note that this is a new
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requirement based on Reference 1; present LACBWR Technical Specifications do not include similar specifications.
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i INSTRUMENTATION 4.2.3.3 ONSITE POWER DISTRIBUTION SYSTEMS A.C.' DISTRIBUTION--INSTRUMENTATION i
Limiting Condition for Operation.
4.2.3.3.1 The Essential Bus instrumentation channels of Table 4.2.3.3-1 shall be OPERABLE with their trip set points L
set consistent with the values shown in the Trip Set Point column of Table 4.2.3.3-2.
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Applicability:
As shown in Table 4.2.3.3-1.
Action:
As shown in Table 4.2.3.3-1.
i Surveillance Requirements
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5.2.11.3 Each Essential Bus instrumentation channel shall be demonstrated OPERABLE by the performance of the CIIANNEL FUNCTIONAL TEST at the frequency shown in Table 5.2.11.3-1.
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i TABLE 4.2.3.3-1 ONSITE POWER DISTRIBUTION SYSTEMS A.C. DISTRIBUTION--UNDERVOLTAGE INSTRUMENTATION Minimum Trip Function and Total No.
Channels Channels Applicable Functional Units of Channels to Trip Operable Operating Modes
- Action LOSS OF POWER a.
440v Essential-2/ Bus 1/ Bus 2/ Bus 1,
2, 3
A Bus Undervoltage (undervoltage relays phases A and C) b.
440v Essential 3/ Bus 2/ Bus 2/ Bus 1,
2, 3 B
Bus Undervoltage (undervoltage relays phases A, B and C)
- Required when engineered safety equipment is required to be operable.
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TABLE 4.2.3.3-1 (continued)
Action Statements Action A -
With the number of channels OPERABLE one less than required by the Minimum Channels OPERABLE require-ment, be in at least ilOT SHUTDOWN within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />; except that one channel may be bypassed up to two hours for surveillance testing or maintenance pro'-
vided that:
a.
The other channel is OPERABLE, and b.
The time during which redundant protection is not provided shall not exceed 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> in any 30 day interval.
Action B -
With the number of OPERABLE Channels one less than the Total Number of Channels, operation may proceed until performance of the next CHANNEL FUNCTIONAL TEST provided the inoperable channel is placed in the tripped condition within one hour.
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v TABLE 4.2.3.3-2 ONSITE POWER DISTRIBUTION SYSTEMS A.C.
DISTRIBUTION--UNDERVOLTAGE INSTRUMENTATION TRIP VALUES Trip Function and Functional Units __
Trip Set Point LOSS OF POWER w
440v Essential Bus (150) volts with a j.,
a.
(1
- 5) second time delay Undervoltage (under-2 voltage relays phases A and C) b.
440v Essential Bus (196) volts with a Undervoltage (under-($10) second time delay voltage relays phases A, B and C) 1 l
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TABLE 5.2.11.3-1 ONSITE POWER DISTRIBUTION SYSTEMS A.C.
DISTRIBUTION--UNDERVOLTAGE INSTRUMENTATION SURVEILLANCE REQUIREMENTS Channel Operation A Conditions Trip Function and Channel Channel Functional In Which Functional Units Check Calibration Test Surveillance Required LOSS OF POWER a.
440v Essential Bus NA NA R
1,2,3 Undervoltage (under-voltage relays phases 3
A and C) b.
440v Essential Bus NA R
M 1,
2, 3
Undervoltage (under-voltage relays phases A, B and C)
R = at least once per 18 months M = at least once per 31 days
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6.
REFERENCES 1.
Letter:
Robert W.
Reid to John P. Madgett, dated June 3, 1977.
2.
LACBWR Operating Manual, Volume IV, Sections 13 through 23.
3.
ACNP-65544, LACBWR Safeguards Report, Section 9.
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APPENDIX A TEST PROCEDURES FOR THE ANNUAL TESTS OF EMERGENCY DIESEL GENERATORS lA AND 1B i.*