ML19309H690
| ML19309H690 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 05/08/1980 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Rhode G NIAGARA MOHAWK POWER CORP. |
| References | |
| NUDOCS 8005190605 | |
| Download: ML19309H690 (1) | |
Text
_ _. -
Yb f ** % q #o,,
UNITED STATES 8
NUCLEAR REGULATORY COMMISSION g
5 REGION I 8006190605 OY [
0, NB1 PARK AVENUE
- [
KING OP PftUSSIA. PENNSYLVANIA 19408 May 8, 1980 0:cket No. 50-410 Niagara Mohawk Power Corporation ATTN:
Mr. G. K. Rhode Vice President System Project Management 300 Erie Boulevard, West Syracuse, New York 13202 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 regarding this matter, please contact this office.
S.incerely, M
[W Boyce H. Grier
" Director l
Enclosures:
1.
IE Information Notice No. 80-20 with Attachment 2.
List of Recently Issued IE Inft.mation Notices CONTACT:
W. Br...Tck (215 a3 5253) cc w/encls:
Eugene B. Thomas, Jr., Esquire
\\
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 detensi i with bolts in place; the reactor coolant level was slightly below the ves:,el head flanges; and the manway covers on top of the once through steam generators l
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 maintenance or testing purposes.
In addition, other systems and components were deactivated to preclude their inadvertent actuation while in a refueling mode, Systems and cc,mponents that were not in service or deactivated included.
i Containment Sp-ay 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 being conducted at the time, Channels 1 and 3 of the Reactor Protection 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 3 bistables also resu'ted in actuation of SFAS Channels 2 and 4.
The actuation of Decay Heat Locp No. 2, the operating DUPLICATE DOCUMENT
/
Since the initiating event was a los 3
were actuated (i.e., Level 1 - High Entire document previously tion; Level 3 - Low Pressure Inject 1 entered into system under:
h hh[
ANO i
N o.
of pages:
}
l
,