ML19309H684
| ML19309H684 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 05/08/1980 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Kay J YANKEE ATOMIC ELECTRIC CO. |
| References | |
| NUDOCS 8005190595 | |
| Download: ML19309H684 (1) | |
Text
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-rA UNITED STATES 8
NUCLEAR REGULATORY COMMISSION o
D j
REGION I g
631 PARK AVENUE
- ,o' KING OF PRUSSIA. PENNSYLVANIA 19406 May 8, 1980 Docket No. 50-29 Yankee Atomic Electric Company ATTN:
Mr. James A. Kay Senior Engineer - Licensing 25 Research Drive Westborough, Massachusetts 01581 Gentlemen:
The enclosed IE Information Notice No. 80-20, " Lass of Decay Heat Removal Capability at Davis-Besse Unit 1 While in a Refueling Mode," 'is forwarded to you for information.
No written response is required.
If you desire addi-tional information regarding this matter, please contact this office.
Sincerely, c/
Boyce H. Grier
" Director
Enclosures:
1.
IE Information Notice No. SG-20 with Attachment 2.
List of Recently Issued IE Information Notices CONTACT:
W. Baunack (215-337-5253) cc w/encls:
H. Autio, Plant Juperintendent J. E. Tribble, President
ENCLOSURE 1 SSINS No.: 6870 l
UNITED STATES Accession No.:
NUCLEAR REGULATORY COMMISSION 8002280671 l
OFFICE OF INSPECTION AND ENFORCEMENT l
WASHINGTON, D. C. 20555 1
IE Information Notice 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 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 too of the once through steam generators were removed).
(See Attachment A, ' stus of Davis-Besse 1 Prior to Loss of Power to Busses E-2 and F-2 for ad ional 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 1N; Emergency Diesel-Generator No. 1; 4.16 KV Essential Switchgear Bus C1; and 13.8 KV Switchgear Bus A (this 1
bus was energized but not aligned).
In brief, the event was due to the tripping of a non-safeguards feeder breaker i
in 13.8 KV Switchgear Bus B. Because of the extensive maintenance and testing activit h being conducted at the time, Channels 1 and 3 of the Reactor Protection I
system (RPS) and Safety Features Actuation System (SFAS) were being energized 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 Channels 2 and 4.
The actuation Decay Heat Loop No. 2, the opera i
DUPLICATE DOCUMENT Since the initiating event was a were actuated (i.e., Level 1 - H Entire document previously tion; Level 3 - Low Pressure Inj entered into system under:
ANO No. of pages: