ML19309H735
| ML19309H735 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 05/08/1980 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Tallman W PUBLIC SERVICE CO. OF NEW HAMPSHIRE |
| References | |
| NUDOCS 8005190656 | |
| Download: ML19309H735 (1) | |
Text
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UNITED STATES I UO h
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8 NUCLEAR REGULATORY COMMISSION a
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REGION I 8,
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$31 FARK AVENUE KING OF PRUSSIA, PENNSYLVANIA 19406 May 8, 1980 Docket Nos. 50-443 50-444 Public Service Company of New Hampshire ATTN:
Mr. W. C. Tallman President 1000 Elm Street Manchester, New Hampshire 03105 Gentlemen:
The enclosed IE Information Notice No. 80-20, " Loss 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 regardin-this matter, please contact this office.
Sincerely,
&s g Boyce H. Grier
,. " Director
Enclosures:
1.
IE Information Notice No. 80-20 with Attachment 2.
List of Recently Issued IE Information Notices CONTACT:
W. Baunack (215-337-5253) cc w/encls:
John DeVincentis, Project Manager
ENCLOSURE 1 SSINS No.: 6870 UNITED STATES Accession No.:
NUCLEAR REGULATORY COMMISSION 8002280671 0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D. C. 20555 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 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 Attachment 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 maintenarice or testing purposes.
In addition, other systems and components were ceactivated 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 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 t,eing conducted at the time, Channels 1 and 3 of the Reactor Protection System (RPS) and Safety Features Actuation System (SFAS) were being energized from caly 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 bistables also resulted in actuation of SFAS Channels 2 and 4.
The actuation Decay Heat Loop No. 2, the operat Since the initiating event was a were actuated (i.e., level 1 - Hi Entire document previously tion; Level 3 - Low Pressure Inje entered into system under:
ANO OO bh!
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