ML20010F441
| ML20010F441 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 08/31/1981 |
| From: | William Jones OMAHA PUBLIC POWER DISTRICT |
| To: | Clark R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8109100191 | |
| Download: ML20010F441 (6) | |
Text
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Omaha Public Power District 1623 HARNEY e OMAHA. NEBRASKA 68102 e TELEPHONE 536 4000 AREA CODE 402 August 31, 1981
.e Mr. Robert A. Clark, Chief Fp O
A U. S. Nuclear Regulatory Commission g
A=l Office of Nuclear Reactor Regulation Ici SEP 0919815 ;9 Division of Licensing Operating Reactors Branch No. 3 Washington, D.C.
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Reference:
Docket No. 50-285
Dear Mr. Clark:
The Commission's letter dated May 13, 1981, requested additional information regarding the adequacy of Fort Calhoun Station's electrical distribution system voltages. The District's submittal dated July 2, 1981, provided responses to Questions A, B, and C of the Commission's letter, while responses to Questicns D and E were to be provided at a later date. The District's response to Questions D and E is attached.
Sincerely, i 'Y'duW
. M W. C. Jones Division Manager Production Operations WCJ/KJM/TLP/RWS:jmm Attachment cc: LeBoeuf, Lamb, Leiby & MacRae 1333 New Hampshire Avenue, N.W.
Washington, D.C.
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a Attachment Question (D)
What is the service factor for the 4160V, 4000V and the 460V safeguards motors?
Response provides a complete listing of motor service factors (except for ventilation air fan motors VA-3A, VA-3B, VA-7C, and VA-70) for the 4160V, 4000V, and 460V safeguards motors.
Custom built, high efficiency motors such as VA-3A, VA-3B, VA-7C, and VA-7D are manufactured without motor service factors because they are designed and used for a specific function.
Question (E) w The NRC letter of August 8,1979 requires a test be performed to verify your analytical results. The latest guidelines required that this test should be performed by:
(a) Loading the station distribution buses, including all Class 1E buses down to the 120/208V level, to at least 30%;
(b) Recording the existing grid and Class 1E bus voltages and bus loading down to the 120/208 volt level at steady state con-ditions and during the starting of both a large Class 1E and non-Class 1E motor (not concurrently);
(Note)
To minimize the number of instrumented locations (recorders),
during the motor starting transient tests, the bus voltages and loading need only be recorded on that string of buses which previously showed the lowest analyzed voltages.
(c) Using the analytical techniques and assumptions of the pre-i vious voltage analyses and the measured existing grid voltage l
and bus loading c*ditions recorded during conduct of test, altaaes for all Class 1E buses down to calculate a new : :t
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the 120/208 volt level.
(d) Compare the analytical der;ved voltage values against the test results.
With good correlation between the analytical results and test results, the test verification requirement vdll be met. That is, the validity of the mathematical model used in performance of the analysis will have been established.
In general the test results should be l
within + 3% of the analytical results; however, the difference between the two when subtracted from or added to should never provide values that would allow operation of the Class 1E equipment outside of rated I
voltage ranges.
1
. Response The District performed voltage measurement tests as part of an und:rvoltage study on the Fort Calhoun Station's electrical distribution system, including all Class 1E buses down to the 120/208V level, during December 1977.
(Note: The District's July 2, 1981 submittal which stated that the electrical distribution system voltage test was con-ducted during 1978 was incorrect.) The voltage measurement tests in-volved electrically loading the Fort Calhoun Station's distribution buses, including all Class IE buses down tc the 120/208V level, to at least 30% of full load as required by the Commission's test guidelines.
Steady state and motor starting transient test voltages were measured for the existing grid and Class 1E buses down to the 480V level. Steady sta;e and motor starting voltage measurements were not recorded at the 120/208V level because all critical safety related electric motors at Fort Calhoun operate on 480V buses or higher.
Based on the District's previous undervoltage analysis, bus IB4B was determined to have the lowest analyzed voltage. Therefore, only transient voltage measurements on bus 184B were recorded.
Two separate motor starting tests were conducted with Class 1E motors to provide voltage data. This test data was then compared to the analytically derived voltages for bus 184B. The first test involved starting the 300 HP containment spray pump SI-3B.
The second test involved the con-current starting of two motors, containment spray pump SI-3C and venti-lation air fan motor VA-70, with combined power requirements of 425 HP.
The compared results of the voltage test measurements and of the analyti-cally derived voltages at bus 1B4B for both transient tests are sum-marized in Enclosure 2.
Voltage values above the 480V level were not analyzed as recording equipment measuring transient voltage changes on the distribution grid (161 KV) and bus 1A4 (4.16 KV) measured no detect-able voltage drops when the motors were started.
Comparison of the test and analytically derived voltage values in revealed the test voltages to be higher than the calculated vol tages.
The calculated voltage of 429V for the motor starting analysis of SI-3B was found to be 3.8% lower than the measured test voltage of 446.2V. The calculated voltage of 421V for the concurrent motor start-ing analysis of SI-3C and VA-7D was found to be 3.5% lower than the measured test voltage of 436.5V. The District believes the resultant correlations of 3.5% and 3.8% are sufficient 2vivence to justify the l
validity of our analytical model and that no further testing is re-quired. Selected variable values (e.g, motor locked rotor factors) used in the calculation of the analy+.cally derived voltages were conservative and probably accounte; for the dif ferences.
It is believed that the use of less conservative variable values would result in closer correlations between analytical and test results.
Please note the District did not perform a motor starting voltage analysis using a non-Class 1E motor as required by Commission guide-lines.
The District believes the concurrent starting of both SI-3C and VA-70 motors for the second transient test provided test results that were more pertinent in establishing the validity of the analytical results than would have been obtained from testing a single non-Class IE motor.
GSE-0-2 2 FORM flotor Terminal Voltage PREPARED BY Calculations 01 REVISION CHECKED BY SH 7 CONT. ON SH 3
AUG 011975 appROvEo 047c OMAHA PUBLIC PCWER DISTRICT REV DATE TASK NO C ENERATING STA. ENG.
- 1) One Line Diagram:
(Refer to Fig. 8.4-1 FSAR) 60B 1261 TI A 3
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(z 6I-3A AC-3C VA-7C At-3A 61-ZA CM-tA VA-3A 61-20 320RR tEAb LOAb 420RP CObum loRR DEAbLBAb (1) - 1st Group of Sequence Starting Motors (2) - 2nd Group of Sequence Starting Motors (3) - 3rd Group of Sequence Starting Motors gccen, (see Gacs+or, D)-
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(.pcci f $cd GSE B-2-2 FORM Motsr Terminal Voltage PREPARED BY -
Calculations O1 7
CHECKED BY SH _Z__ CONT. ON SH 3
REVISION AUG 011975 APPROVED DATE OMAHA PUBLIC POWER DISTRICT REV DATE TASK NO FC-77-40 GENERATING STA ENG.
- 1) One Line Diagram:
(Refer to Fig. 8.4-1 FSAR) 60B 1291 M
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g 325HP At-3B 22 HHP 61-3B 61-3CI.!5 CH-\\C 220MP SI-2B Cu-1B VA-3B bEAb LOAb bEAb LOAb VI,Tb bEAb tbAb (1) - 1st Group of Sequence Stortiry Potors (2) - 2nd Group of Sequence Starting Motors (3) - 3rd Group of Sequence Starting Motors Se r vice. Factors in gecen
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Test and Analytically Derived Voltages at Bus 1B4B During Class 1E Motor Starting Transient Tests Motor Group Started Test Voltage Calculated Voltage 1)
Containment Spray Pump 446.2V 429V SI-3B 2)
Containment Spray Pump 436.5V 421V SI-3C and Ventilation Air Cooling Unit VA-70 i
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