ML19309H753
| ML19309H753 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 05/08/1980 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Millen C PUBLIC SERVICE CO. OF COLORADO |
| References | |
| NUDOCS 8005190678 | |
| Download: ML19309H753 (1) | |
Text
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UNITED STATES POR:HQ mM8c,%
NUCLEAR REGULATORY COMMISSION LPOR REGloN IV g
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611 RY AN PLAZA oRIVE, SulTE 1000 bb1b 7 j.x. [ './ j j ARLINGTON, TEXAS 76012
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.g, STATE May 8, 1980 Docket No. 50-267 Public Se M ee Company of Colorado AI"IN:
Mr. C. K. Millen Senior Vice President P. O. Box 840 Denver, Colorado 80201 Gentlemen:
The enclosed IE Informatien 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 recom-
=ending or requesting specific licensee actions =ay be issued.
If you have questions regarding this matter, please contact me.
Sincerely, p_
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3-j ~j A9]$,( dl,if 3
vf Karl V. Seyfrit
/r Director
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Enclosures:
1.
IE Information Notice No. 80-20 2.
List of Recently Issued g
IE Information Notices cc:
D. W. Warembourg, Nuclear Production Manager Fort St. Vrain Nuclear Station P. O. Box 368 Platteville, Colorado 80651 i
L. 3 rey, Manager, Quality Assurance
SSINS No.:
6870 UNITED STATES Accession No.:
NUCLEAR REGULATORY COMMISSION 8002280671 0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D. C. 20555 IE Information Notice No. 80-20 Date: May 8, 1980 Page 1 of 3 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 90 F; 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 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 a of all four output channels (i.e.,
loss of power to Channels 1 and 3 Channels 2 and 4.
The actuation o DUPLICATE DOCUbHUTT Decay Heat Loop No. 2, the operati Entire document previously Since the initiating event was a 1 entered into system under:
ANO were actuated (i.e., Level 1 - Hig l
tion; Level 3 - Low Pressure Injec N o.
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