ML19291C003
| ML19291C003 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 11/30/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | John Miller GEORGIA POWER CO. |
| References | |
| NUDOCS 7912190454 | |
| Download: ML19291C003 (1) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION
.E REGION 11 o
101 MARIETTA ST., N.W., SUITE 3100 o
ATLANTA, GEORGIA 30303 NOV 3 01979 In Reply Refer To:
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Georgia Power Company Attn:
J. H. Miller, Jr.
Executive Vice President 270 Peachtree Street, N.W.
Atlanta, Georgia 30303 Gentlemen:
The enclosed IE Bulletin No. 79-27, is forwarded for action. A written response is required. If you desire additional information regarding this matter, please contact this office.
Sincerely, JamesP.O'Re(
Director
Enclosures:
1.
List of Recently Issued IE Bulletins 1790 357 7912190 m
NOV 3 01979 Georgia Power Company cc w/ encl:
M. Manry, Plant Manager Post Office Box 442 Baxley, Georgia 31513 C. E. Belflower Site QA Supervisor Post Office Box 442 Baxley, Georgia 31513 W. A. Widner, General Manager Nuclear Generation Georgia Power Company Post Office Box 4545 Atlanta, Georgia 30303 s
1790 358 '
9
UNITED STATES SSINS No.: 6820 NUCLEAR REGULATORY COMMISSION Accession No.:
0FFICE OF INSPECTION AND ENFORCEMENT 7910250499 WASHINGTON, D.C.
20555 November 30, 1979 IE Bulletin No. 79-27 LOSS OF NON-CLASS 1E INSTRUMENTATION AND CONTROL POWER SYSTEM BUS DURING OPERATION Description of Circumstances:
On November 10, 1979, an event occurred at the Oconee Power Station, Unit 3, that resulted in loss of power to a non-class IE 120 Vac single phase power panel that supplied power to the Integrated Control System (ICS) and the Non-Nuclear Instrumentation (NNI) System. This loss of power resulted in control system malfunctions and significant loss of information to the control room operator.
Specifically, at 3:16 p.m.,
with Unit 3 at 100 percent power, the main condensate pumps tripped, apparently as a result of a technician performing maintenance on the hotwell level control system. This led to reduced feedwater flow to the steam generators, which resulted in a reactor trip due to high coolant system pressure and simultaneous turbine trip at 3:16:57 p.m.
At 3:17:15 p.m.,
the non-class 1E inverter power supply feeding all power to the integrated control system (which provides proper coordination of the reactor, steam generator feedwater control, and turbine) and to one NNI channel tripped and failed to automatically transfer its loads from the DC power source to the regulated AC power source. The inverter tripped due to blown fuses. Loss of power to the NNI rendered control room indicators and recorders for the reactor coolaot system (except for one wide-range RCS pressure recorder) and most of the secondary plant systems inoperable, causing loss of indication for systems used for decay heat removal and water addition to the reactor vessel and steam generators. Upon loss of power, all valves controlled by the ICS assumed their respective failure positions. The loss of power existed for approximately three minutes, until an operator could reach the equipment room and manuelly switch the inverter to the regulated AC source.
The above event was discussed in IE Information Notice No. 79-29, issued November 16, 1979.
NUREG 0600 " Investigation into the March 28, 1979 TMI Accident" also discusses TMI LER 78-021-03L whereby the RCS depressurized and Safety Injection occured on loss of a vital bus due to inverter fai1.ure.
j 7gn zqg Actions to Be Taken by Licensees For all power reactor facilities with a DUPLICATE DOCUMENT completion of construction (North Anna Sequoyah, and Zimmer):
g Entire document previously entered into system under:
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