ML19309H786
| ML19309H786 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 05/08/1980 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Papay L SOUTHERN CALIFORNIA EDISON CO. |
| References | |
| NUDOCS 8005190716 | |
| Download: ML19309H786 (1) | |
Text
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'o UNITED STATES 8 005190 7 I b
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.c REGION V
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1990 N. CALIFORNI A BOULEVARD o
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SUITE 202, WALNUT CREE K PLAZA o.,.e WALNUT CREE K, CALIFORNIA 94S96 May 8, 1980 Docket Nos. 50-206, 50-361, 50-362 + ~ GSMttv maaNN#^
Southern California Edison Company P. O. Bcx 800 2244 Walnut Grove Avenue Rosemead, California 91770 Attention:
Dr. L. T. Papay, Vice President Advanced Engineering 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, contingent upon the results of further staff evaluation, a Bulletin or Circular recommending or requesting specific licensee actSns may be issued.
If you have quastions regarding this m&tter, please contact me.
Sincerely,
.I Sc@-
R. H. Engelken Direttor
Enclosures:
1.
IE Information Notice No. 80-2G 2.
List of Recently Issued IE Information Notices cc w/ enclosures:
J. M. Curran, SCE R. Dietch, SCE wm
SSIriS No.: 6870 UtlITED STATES Accession No.:
NUCLEAR REGULATORY COMMISSI0ft 8002280671 0FFICE OF INSPECTION AtlD ErlFORCEMEtlT WASHIrlGT0tl, D. C. 20555 May 8, 1980 IE Information Notice 80-20 LOSS OF DECAY HEAT REMOVAL CAPABILITY AT DAVIS-BESSE UNIT 1 WHILE IN A REFUELING MODE Description of Circumstances:
On April 19, 1980, decay heat removal capability was lost at Davis-Besse Unit 1 for approximately two and one-half hours. At the time of the event, the unit was in a refueling mode (e.g., RCS temperature was 90F; decay heat 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 purpeses.
In ? dition, other systems and d
components were deactivated to preclude their inadve; t.ent actuation while in a refueling mode. Systems and components that were not in service or deactivated included:
~
Containnent Spray System; High Pressure Injection System; Source Range Channel 2; Decay Heat Loop No.1; Station Battery IP and Irl; Emergency Diesel-Generator No. 1; 4.16 KV Essential Switchgear Bus C1; and 13.8 KV Switchgeer 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 Sy: tem (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 1 and 3, and Channels 2 e
loss of power to Channels 1 and 3 bista Channels 2 and 4.
The actuation Decay Heat loop No. 2, the operat DUPLICATE DOCUMENT Since the initiating event was a reviously were actuated (i.e., Level 1 - Hi.
Entire document tion; Level 3 - Low Pressure Inje entered into sys bh ANO
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