ML19309H783
| ML19309H783 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay, Diablo Canyon |
| Issue date: | 05/08/1980 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Crane P PACIFIC GAS & ELECTRIC CO. |
| References | |
| NUDOCS 8005190712 | |
| Download: ML19309H783 (1) | |
Text
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'o UNITED STATES
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g NUCLEAR REGULATORY COMMISSION 8005190 712-c REGION V g.
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1990 N. CALIFORNIA BOULEVARD o,
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SulTE 202, WALNUT CREEK PLAZA e,,,o WALNUT CREE K, CALIFORNIA 94596 l
l May 8, 1980 1
Docket flos. 50-133, 50-275, 50-323 Pacific Gas and Electric Company 77 Beale Street San Francisco, California 94106 Attention: fir. Philip A. Crane, Jr.
Assistant General Counsel Gentlemen:
The enclosed Information tiotice provides early notification of an event that may have safety significance. Accordingly, you should review the Information flotice for possible applicability to your facility.
tio 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 actions may be issu_ed.
If you have questions regarding this matter, please contact me.
Sincerely,
,el L R. H. Engelken Director
Enclosures:
1.
IE Information Notice flo. 80-20 2.
List of Recently Issued IE Information tiotices cc w/ enclosures:
W. Barr, PG&E W. Raymond, PG&E R. Ramsay, PG&E, Diablo Canyon E. Weeks, PG&E, Humboldt Bay E. B. Langley, Jr., PG&E l
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SSIrlS No-: 6870 UtlITED STATES Accession t'o. :
flVCLEAR REGULATORY COMMISSION 8002280671 0FFICE OF IflSPECTION Afl0 ENFORCEMErlT WASHIflGT0ft, D. C. 20555 May 8, 1980 IE Information Notice 80-20 LOSS OF DECAY HEAT REtiOVAL CAPABILITY AT DAVIS-BESSE UtilT 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 mariay 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 comoonents were deactivated to preclude their inadvertent actuation while in a refueling mode.
Systems and components that were not in service or deactivated included:
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Containnent Spray System; High Pressure Injection System; Source Range Channel 2; Decay Heat Loop No.1; Station Battery IP and Ifl; Energency 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 scurce 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 and 4), the loss of power to Channels 1 and 3 bistables also resulted Channels 2 and 4.
The actuation of Decay Heat loop No. 2, tha operatin Since the initiating event was a los were actuated (i.e., Level 1 - High Entire document Previously tion; Level 3 - Low Pressure Injecti entered into system under:
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