ML19309H776
| ML19309H776 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 05/08/1980 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| References | |
| NUDOCS 8005190703 | |
| Download: ML19309H776 (1) | |
Text
8 005190 M Tb o"%jo UNITED STATES g
NUCLEAR REGULATORY COMMISSION n
- c REGION V 1990 N. CALIFORNIA BOULEVARD o,
g'g SulTE 202, WALNUT CREEK PLAZA e,,,,
WALNUT CREE K. CALIFORN!A 945%
May 8, 1980 Docket flo. 50-312 Sacramento Municipal Utility District P. O. Box 15830 Sacramento, California 95813 Attention: Mr. John J. Mattimoe Assistant General Manager Gentlemen:
The enclosed Information flotice provides early notification of an event that may have safety significance. Accorr' agly, you should review the Information Notice for possible applicab' ty to your facility.
No specific action or response is r~eques.ted at this time; however, contingent 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,
+v cid -
3 R. H. Engelken Director
Enclosures:
1.
IE Information tiotice No. 80-20 2.
List of Recently Issued j
IE Information flotices cc w/ enclosures:
1 R. J. Rodriguez, SMUD L. G. Schwieger, SMUD w
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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 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 ruactor 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 pu.rposes.
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 1N; Emergency Diesel-Generator No. 1; 4.16 KV Essential Switchgear Bus Cl; 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 1 and 3, and Channels 2 and 4), the loss of power to Channels 1 and 3 bis Channels 2 and 4.
The actuation of 5 Decay Heat Loop No. 2, the operating DUPLICATE DOCUMENT Since the initiating event was a loss were actuated (i.e., level 1 - High R Entire document previously tion; Level 3 - Low Pressure Injectio entered into system under:
ANO f 0 0 $ $ 0 (o $
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