ML19321A806
| ML19321A806 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 05/08/1980 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Nichols T SOUTH CAROLINA ELECTRIC & GAS CO. |
| References | |
| NUDOCS 8007240220 | |
| Download: ML19321A806 (1) | |
Text
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UNITED STATES NUCLEAR REGULATORY COMMISSION a
REGION il g
101 MARIETTA ST N.W., SUITE 3100 ATLANTA, GEORGIA 30303 MAY 8 1980 In Reply Refer To:
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South Carolina Electric and Gas Company Attn:
T. C. Nichols, Jr., Vice President Power Production and System Operations Post Office Box 764 Columbia, South Carolina 29218 Gentlemen:
The enclosed Information Notice provides early notification of an event that may have safety significance. Accordingly, you should review the Information Notice for possible applicability to your facility.
No specific action or response is requested at this time; however, con-tingent upon the results of further staff evaluation, a Bulletin or Circular recommending or requesting specific licensee actions may be issued. If you have questions regarding this matter, please contact me.
Sincerely,
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_A James P. O'Reilly Director
Enclosures:
1.
IE Information Notice No. 80-20 2.
List of Recently Issued IE Information Notices 8007240220
SSINS No.:
6870 UNITED STATES Accession No.:
NUCLEAR REGULATORY COMMISSION 8002280671 0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D. C. 20555 May 8, 1980 IE Information Notice 80-20 16SS 0F DECIV~HE FREMOTAI C piBfLIT fkT DAVIS BESSE M IT~1 WHILE IN A
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REFUELING MODE Description of Circumstinces:
On April 19, 1980, decay heat removal capability was lost at Davis-Pesse Unit I for approximately two and one-half hours. At the time of the event, the unit was in a refueling mode (e.g., KCS temperature was 90F; decay beat was being removed by Decay Heat Loop No. 2; the vessel head was detensioned with bolts in place; the reactor coolant level was slightly below the vessel head flanges; and the manway covers on top of the once through steam generators were removed).
(See Enclosure A, Status of Davis-Besse 1 Prior to Loss of Power to Busses E-2 and F-2 for additional details regarding this event.)
Since the plant was in a refueling mode, many systems or components were out of service for maintenance or testing purposes.
In addition, other systems and components were deactivated to preclude their inadvertent actuation while in a refueling mode. Systems and components that were not in service or deactivated included:
Containment Spray System; High Pressure Injection System; Source Range Channel 2; Decay Heat Loop No. 1; Station Battery IP and IN; Emergency Diesel-Generator No. 1; 4.16 KV Essential Switchgear Bus C1; and 13.8 KV Switchgear Bus A (this bus was energized but not aligned).
In brief, the event was due to the tripping of a non-safeguards feeder breaker in 13.8 KV Switchgear Bus B. Because of the extensive maintenance and testing activities being conducted at the time, Channels 1 and 3 of the Reactor Protec-tion System (RPS) and Safety Features Actuation System (SFAS) were being ener-gized from only one source, the source emanating from the tripped breaker.
Since the SFAS logic used at Davis-Besse is a two-out-of-four input scheme in which the loss (or actuation) of any two input signals results in the actuation of all four output channels (i.e., Channels I and 3, and Channels 2 and 4), the loss of power to t;hannels 1 and 3 bistables also resulted in actuation of SFAS Channels 2 and 4.
The actuation of SFASA:mnhkrdr. hint =cennfEqm5 SEW 7:
Decay Heat Loop No. 2, the operating lojipj 7 ~ 9 " " P " 9 M'T " N "- ~']
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