ML20072K411
| ML20072K411 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 06/29/1983 |
| From: | Oprea G HOUSTON LIGHTING & POWER CO. |
| To: | Jay Collins NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, ST-HL-AE-972, NUDOCS 8307060268 | |
| Download: ML20072K411 (4) | |
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The Light Company n.,i,si.,,, usiii,im <,-> m u. moo n 3<>ii.1~,,oin au> 22w2u June 29 1983 ST-HL-AE-972 File Number: G12.144 3B@ M JWE 3, Mr. John T. Collins s
Regional Administrator, Region IV JUN 3 0 083 s
Nuclear Regulatory Commission 611 Ryan Plaza Dr., Suite 1000 O
Arlington, Texas 76012
Dear Mr. Collins:
South Texas Project Units 1 & 2 Docket Nos. STN 50-498, STN 50-499 Final Report Concerning the Voltage Regulation Problem for Large Motors on 480V Class IE Load Centers On April 19, 1983, pursuant to 10CFR50.55(e), Houston Lighting & Power Company (HL&P) notified your office of an item concerning a voltage regulation problem for the ESF 4160/480 Volt Load Center Transformers.
Attached is the Final Report concerning this item.
If you should have any questions concerning this matter, please contact Mr. Michael E. Powell at (713) 877-3281.
Very trul
[',V @u. fl y yours 1
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Execut'ive Vice President MEP/mg Attachment
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PDR ADOCK 05000498 U
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Ilouston I.ighting & l'ower Comgiany June 29, 1983 cc:
G. W. Oprea, Jr.
ST-HL-AE-972 J. H. Goldberg File Number: G12.144 J. G. Dewease Page 2 J. D. Parsons D. G. Barker M. R. Wisenburg R. A. Frazar J. W. Williams R. J. Maroni J. E. Geiger H. A. Walker S. M. Dew J. T. Collins (NRC)
H. E. Schierling (NRC)
W. M. Hill, Jr.
(NRC)
M. D. Schwarz (Baker & Botts)
R. Gordon Gooch (Baker & Botts)
J. R. Newman (Lowenstein, Newman, Reis, & Axelrad)
STP RMS Director, Office of Inspection & Enforcement Nuclear Regulatory Commission Washington, D. C. 20555 G. W. Muench/R. L. Range Charles Bechhoefer, Esquire Central Power & Light Company Chairman, Atomic Safety & Licensing Board P. O. Box 2121 U. S. Nuclear Regulatory Commission Corpus Christi, Texas 78403 Washington, D. C.
20555 H. L. Peterson/G. Pokorny Dr. James C. Lamb, III City of Austin 313 Woodhaven Road P. O. Box 1088 Chapel Hill, North Carolina 27514 Austin, Texas 78767 J. B. Poston/A. vonResenberg Mr. Ernest E. Hill City Public Service Board Lawrence Livermore Laboratory P. O. Box 1771 University of California San Antonio, Texas 78296 P. O. Box 808, L-46 Livermore, California 94550 Brian E. Berwick, Esquire William S. Jordan, III Assistant Attorney General Harmon & Weiss for the State of Texas 1725 I Street, N. W.
P. O. Bo'x 12548 Suite 506 Capitol' Station Washington, D. C.
20006 Austin, Texas 78711 Lanny Sinkin Citizens for Equitable Utilities, Inc.
Citizens Concerned About Nuclear Power c/o Ms. Peggy Buchorn 5106 Casa Oro Route 1, Box 1684 San Antonio, Texas.78233 Brazoria, Texas 77422 Robert G. Perlis, Esquire Hearing Attorney
-Office of the Executive Legal Director
- U. S. Nuclear Regulatory Commission
-Washington, D.
C.-
20555 Revision Date 04-29-83 i
Final Report Concerning the Voltage Regulation Problem for Large Motors on 480V Class IE Load Centers I.
Summary The ESF 4160/480 volt transformers are required to supply the ESF 480 volt load centers and to ensure that the ESF load center bus voltage does not drop
'below 80% of the motor rated voltage of 460 volts. As presently designed, the subject transformers have an impedance which is too high for acceptable voltage regulation on the 480 volt ESF load center on start up of equipment on the busses.
II.
Description of the Deficiency On April 19, 1983, pursuant te 10CFR50.55(e), Houston Lighting & Power (HL&P) notified your office of an item concerning the ESF 4160/480 volt load center transformers.
There are six transformers per unit which supply the 480 volt load centers EIA, ElB, and E1C in a double ended, split bus arrangement utilizing a normally open tie breaker.
This results in two busses per load center or train, which are identified as EIA1, E1A2, E181, E182, E1C1 and E1C2. There is one RCFC Supply Fan Motor assigned to each of these basses.
The transformers are required to ensure that the ESF 1 cad center busses identified above do not drop below 80% of motor rated voltage (460 volts).
On initiation of a safety injection (SI) signal, two (2) RCFC Supply Fan Motors per train are designed to start simultaneously. As a result of the transformer impedance (7%) and the high starting current of the RCFC Supply Fan Motors, there is a high probability that the ESF bus voltages would drop below 80% of motor rated voltage to the extent that none of the motors could be started. Without the RCFC Supply Fan Motors, the ability to remove heat from the Containment could be inhibited during an accident.
Other equipment served by the same busses are the Residual Heat Removal Pumps and the Spent Fuel Pool Cooling Pumps.
The ability of this equipment to be started may also be impacted by the high transformer impedance.
III. Corrective Action The corrective action will be to replace the existing ESF Load Center Transformers with new transformers with a lower impedance based on system requirements.
Once the re-design has progressed sufficiently, Chapter 8 of the FSAR will be updated providing the details of the change.
IV.
Recurrence Control A recurrence control program is not necessary.
Bechtel has procedures in place to preclude this type of incident from recurring.
l Page 2 V.
Safety Analysis No detailed safety hazards analysis will be performed.
It is conservatively assumed that the large Class 1E motors served by the auxiliary transformers would fail to start on demand.
This is considered to be a potential common mode failure.
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