ML19256F460
| ML19256F460 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 11/30/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Eric Turner HOUSTON LIGHTING & POWER CO. |
| References | |
| NUDOCS 7912190177 | |
| Download: ML19256F460 (1) | |
Text
7Ec UNITE D STATES
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e NUCLEAR REGULATORY COMMISSION R EGloN IV
/no 611 RYAN PLAZA DRIVE, SUITE 1000 2
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ARLINGTON, TEXAS 76012
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November 30, 1979 In Reply Refer To:
RIV Docket Nos. 50-498/IE Bulletin No. 79-27 50-499/IE Bulletin No. 79-27 Houston Lighting & Power Company ATTN:
Mr. E. A. Turner, Vice President Power Plant Construction and Technical Services Post Office Box 1700 Houston, Texas 77001 Centlemen:
The enclosed IE Bulletin No. 79-27, is forwarded to you for information.
Although no written response is required at this time, these concerns will be addressed as part of the licensing process for your plant.
If you desire additional 1..?ormation regarding this matter, please contact this office.
Sincerely, I
',: h -; l2ll: ja.
~
KarlV.Seyfrit/f Director
Enclosures:
1.
List of Recently Issued IE Bulletin 1774 336
,7 91219 0 l77
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 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 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 TMI LER 78-021-03L whereby the RCS depressurized and Sa on loss of a vital bus due to inverte Actions to Be Taken by Licensees DUPLICpcNS DOCUbusNT For all power reactor facilities with Entire docnnnent previcxisly completion of construction (North Ann entered into system under:
Sequoyah, and Zimmer):
0774
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