ML19291B979
| ML19291B979 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 11/30/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Counsil W NORTHEAST NUCLEAR ENERGY CO. |
| References | |
| NUDOCS 7912190039 | |
| Download: ML19291B979 (1) | |
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UNITED STATES
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%,**N***,o KING OF PRUSSIA, PENNSYLVANIA 19406 November 30, 1979 Docket Nos. 50-336 50-245 50-423 Northeast Nuclear Energy Company ATTN: Mr. W. G. Counsil Vice President - Nuclear Engineering and Operations P. O. Box 270 Hartford, Connecticut 06101 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, i ~ ~ A:w Boyce H. Grier
" Director
Enclosures:
1.
List of Recently Issued IE Bulletins CONTACT:
D. L. Caphton (215-337-5308) cc w/encls:
K. W. Gray, Construction Quality Assurance Lead H. R. Nims, Director of Nuclear Projects J. F. Opeka, Station Superintendent D. G. Diedrick, Manager of Quality Assurance J. R. Himmelwright, Licensing Safeguards Engineer O
1790 252 q 912190057
ENCLOSURE 1 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 supplisd 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 In 16, 1979.
NUREG 0600 " Investigation into the Mar DUPLICATE DOCUMENT TMI LER 78-021-03L whereby the RCS dep on loss of a vital bus ~due to invertei.
Entire document previously entered into system under:
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