ML18046A833
| ML18046A833 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 07/29/1981 |
| From: | Johnson B CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8108030303 | |
| Download: ML18046A833 (6) | |
Text
consumers Power company General Offices: 212 West Michigan Avenue, Jackson, MI 49201 * (517) 788-0550 July 29, 1981 Director, Nuclear Reactor Regulation Att IV1r Dennis M Crutchfield, Chief Operating Reactors Branch No 5 US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT ~ ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES ADDITIONAL INFORMATION NRC letter dated June 24, 1981 requested additional information on the subject of Adequacy of Station Electric Distribution System Voltages*.
Attached are the questions presented by the NRC and Consumers Power c.omJ?anY respo~ses.
Brian D Johnson Senior Licensing Engineer CC Director,.Region I~I, USNRC NRC Resident Inspector-Palisades
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Attachment I Responses to Additional Information Requests from NRC Letter dated June 24, 1981
- i.
CPCo has shown in the speed torque curves that the majority of the Class lE motors will start, under load, when the motor terminal voltage is 70%.
Verify that all Class lE loads will start when the motor terminal voltage is 70% (or some other specified level) and deliver the capacity required to mitigate the consequences of an accident.
Response to Item 1
'Ille speed torque curves, which were submitted in CPCo letter dated March 3, 1981, show that. the 2400V motors will start anO. operate the required load when the motor terminal voltage is at or above the value shown in Table I.of this submittal.
The 480V containment cooling fan motors have been earmarked for replacement as a result of environmental qualification requirements which cannot be met by the existing motors.
These motors will be designed and tested to start and operate under load conditions at 70% voltage.
'Ille 480V boric acid pump motors are not required to start and operate until the voltage reaches 85% which is the voltage that the motor starter contactors pick up.
No curves are available for these motors.because of the small size and extremely rapid accelerating time.
A voltage of 85% is generally sufficient to overcome the initial starting inertia and also provides suffici~nt accelerat-ing torque to bring the motor to full speed.
Test documentation to support this assumption is not available but CPCo Technical experts are comfortable with the statement.
The 480V charging pump motors are provided with computer generated speed/torque curves for.100% voltage.
Our analysis assumes that the motors will start and operate at 70% voltage, but we do not have test doci.lmentation to provide absolute proof that our assumption is. correct.
Absolute proof would have to be obtained by actual test or possibly computer generated speed torque curves for 70% voltage on the motors and full load on the ptimps.
- 2.
CPCo has shown that the 460V. and 440V.motors and the 480V battery chargers do not have sufficient voltage to operate continuously with.maximum unit loads concurrent with the offsite grid at 95% of nominal.
Moreover, the voltage at the 480V contactors is less than that required to pic:k up additional loads that.may be required by an accident.
Additionally the instruments needed in an accident situation will not have adequate voltage to provide correct readout under the voltage conditions in question 2 with the l20V AC instrument bus supplying power to the 120V AC preferred instrument bus; It is* apparent that the 480V battery charger
- could he required to operate at less than the rated minimum input voltage (432V) while under a degraded condition without operation of the second level undervoltage relays.
Operation under this condition would discharge the batteries.. The FSAR assumes that these batteries will be fully charged prior to a design basis accident.
2 Based upon the above, either demonstrate that our findings are not correct or provide proposed modifications and schedules to correct these deficiencies.
The degraded grid voltage relay setpoint (91.4% + 0.13%) is higher than the minimum expected continuous operating voltag; for 2400V buses lC and 1D (87.3% of 24ooy).
The loss of voltage relay setpoint (77.5% + 3.3%) is higher than the minimum analyzed motor starting transient.
Based on the CPCo submittals, it is not evident that the time delay for either the degraded grid voltage relays or the loss of voltage relays is sufficient to ride through all expected motor starting transient dips when the grid is at 95% and the unit loads are maximum.
It appears that there may be potential for spuriously separating the Class lE buses from the offsite source by operation of either the loss of voltage or second level under-voltage relays.
Response to Item 2 Based on changes in the CPCo transmission system and recent improvements in the computer analysis, the 95% value should be disregarded as a reference for any future discussion and should be replaced with 100%.
Our review of station log books over several years has shown that 100% is a very realistic value.
The acceleration time bar chart, which was submitted as Figure 1 in the March 3, 1981 CPCo letter, shows that at-100% voitage, the emergency motoTs will start and operate.. That in.d~de_s the 46ov and 440V motors.
As stated in the Response to Item 2 in the March 3, 1981 letter, the battery chargers have a reduced output when the input voltage is reduced below its rating.
It is not apparent from this statement that operation under reduced voltage would discharge the batteries. It has not been shown that maxiumu unit loads means that the chargers are fully loaded and that a reduced input voltage would result in discharging the batteries.
In fact, the chargers do have built-in reserve capacity when the unit is operating under maximum load.
As stated in the Response to Item 6 in the March, 1981 letter, the four 120V a-c preferred busses are normally supplied by inverters from the batteries and battery chargers. It is also possible to power one of these busses at a time using the 120V a~c instrument bus which is connected to the MCCs.
No test results are avail_able to show what the effect of a slightly reduced voltage would have on the function of the instruments on the preferred bus. It is our position that a reduction of 5% below the rating of the instrument loop regulated power supply would have an undetectable effect and that if any effect did result, it would cause the instruments to react in a manner that would provide a safer condition in terms of mitigating the consequences of an accident.
The 2400V system is protected by three separate undervoltage relays of different types and settings.
These types and settings were previously submitted, but fo_r clarity, Figure II is being submitted again to show the actuai time vs* percent voltage for the three relays combined.
Also shown on Figure II.is the voltage vs time profile for the worst case loading of the emergency busses with the system vol*tage.at 100,~.
The value for 100% should be used as explained above instead of 95%.
'!'ABLE I
SUMMARY
OF INSTANTANEOUS VOLTAGES DURING SIS V 345 AT 1.0 PU Bus or Motor lC Component Cooiing P52A (R)
Service Water P7B (S)
Component Cooling P52C (R)
LPSI P67B (S)
Containment Spray P54B (S)
HPSI P66B (S)
Containment Spray P54C (S) 13 11 Recirc Fan V4A (S)
Charging Pump P55C (R)
MCC l Boric Acid P56B (S) 1D Service Water P7A (R)
Service Water P7C (R)
LPSI P67A (S)
HPSI P66A (S)
Component Cooling P52B (S)
HPSI P66C (S)
Containment Spray P54A (S) 12 Recirc Fan VIA (S)
Recirc Fan V2A (S)
Recirc.Fan V3A (S)
Charging Pump P55B (S)
Charging Pump P55A (S)
MCC 8 MCC 2 Boric Acid P56A (S) 16 lE (V Rating)
(2400)
(2300)
(2300)
(2300)
(2300)
(2300)
(2300)
(2300)
( 480)
( 480)
( 460)
( 440)
(. 480)
( 460)
(2400)
(2300)
(.2300)
(2300)
(2300)
C2300)
(2300)
(2300)
( 480)
( 460)
( 460)
( 460)
( 440)
( 440)
( 480)
( 480)
( 460)
( 480)'
(2400)
(R) = R~ing; (S) = Starting Prestart V 0.9516
- 0. 9511 0.9516
- 0. 9511
- 0. 9516 o.9516 0.9516 0.9516 0.9296 0.92i6 0.9216 0.9039 0.9213 0.9213 0.9515 0.9493 0.9493 0.9515 0.9515 0.9515 0.9515
- o. 9515 0.9211 0.9211
- 0. 9211 0.9211
- 0. 9211
- 0. 9211 0.9156 0.9204 0.9204..
0.9247.
0.9521 Per unit voltages are on a 2400 V or 480 V Base.
12/10/80 Starting V 0.7461 0.7455 0.7354
- 0. 7455.
0.7413 0.7433 0.7430
- o. 7434
- o. 7173 0.6660 0.6180 0.6410 0.6636 0.6306 0.7444 0.7416 o.. 7416.
0.7401 0.7405 0.7418 0.7397 0.7394 0.5570 0.5119 0.5119 0.5119 0.5169 0.5128 0.5477 0.5543 0.5318 Q.7234 0.7533 Running V 0.9303 0.9298 0.9282 0.9298 0.9294" 0.9299 0.9297 0.9299.
0.. 9078 0.8933 0.. 8778 0.8750 0.8926 0.8755 0.9297 0.9274 0.9274 0.9289 0.9289 0.9292 0.9288 0.9289 0.8690 0.8535 0.8535
- o. 8535 0.8559
. '0. 8573 0.8631 0.8678 0.8535 0.9035 0.9322
FIGURE PALISADES-ACCELERATION TIMES OF EMERGENCY MOTORS
~. 61 SEC IJ.60 SEC n----------- IJ.62 SEC RECIRC V~A LJ.*7q. SEC BEGI Ns1ccELERATIMG
. 80!1 C PS6~7 SEC CONTACTOR CLOSES RECIRC VIA
- ,--_... ______ 8. 53 SEC RECIRC V2A 19*********************************--****--------- 8. 53 SEC RECIRC V3A
- -*~-**~-~~*******************************--------- _8_. _S_3 SEC - --
CHARG PUMP PSSB
........,********************************------------ 10. I q SEC CHARG PUMP PSS.~
ii.. *************************************** ----------- 9.82 SEC*
BORIC PS6A COHTACTOR CLOSES_...
.7 SEC 0
2 3
s 6
7 a
9 10 11 12 TIME - SECOHOS
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