ML19291B984
| ML19291B984 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 11/30/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Millen C PUBLIC SERVICE CO. OF COLORADO |
| References | |
| NUDOCS 7912190189 | |
| Download: ML19291B984 (1) | |
Text
CENTRAL FILES PDR:HQ UNITED STATES
[pa asc jo NUCLEAR REGULATORY COMMISSION oq (pgg 47 '@
REGION IV
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% Y,,,[df November 30, 1979 Docket No. 50-267 Public Service Company of Colorado ATTN:
Mr. C. K. Millen Senior Vice President P. O. Box 840 Denver, Colorado 80201 Centlemen:
The enclosed IE Bulletin ". 79-27, is forwarded for action. A uritten response is required.
If'you desire additional information regarding,this matter, please ccTtact this office.
Sincerely, 1
/
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gKarctLT/y *I -
f/ g A?
r V. Scyfrit Director i
Enclosure.
1.
List of Recently Issued IE Bulletins cc:
D. W. Warembourg, Nuclear Production Manager Fort St. Vrain Nuclear Station P. O. Box 368 Platteville, Colorado 80651 L. Brey, Manager, Quality Assurance
/
~179b 314-7912190 M
UNITED STATES SSINS No.:
6820 NUCLEAR REGULATORY COMMISSION Accession No.:
OFFICE OF INSPECTION AND ENFORCEMENT 7910250499 WASHINGTON, D.C.
20555 IE Bulletin No. 79-27 Date:
November 30, 1979 Page 1 of 3 LOSS OF NON-CLASS 1-E 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 1-E 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 1-E inverter power supply feeding all power to the integrated control system (which provides proper coordination o'f the reactor, steam generator feedwater control, and turbine) and to one NNI channel tripped and failed to automatically t ransfer 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 coolant. 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 manually 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 THI LER 78-021-03L whereby the RCS depressurized and Safety Injection occurred on loss of a vital bus due to inverter failu Actions to Be Taken by Licensees DUPLICATE DOCUMENT For all power reactor facilities wi Entire document previously completion of construction (North entered into system under.
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