ML19353A077
| ML19353A077 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 12/16/1980 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Gilberts D NORTHERN STATES POWER CO. |
| References | |
| NUDOCS 8101070082 | |
| Download: ML19353A077 (1) | |
Text
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UNITED STATES
" 7, NUCLEAR REGULATORY COMMISSION i
.E REGION li' o,
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799 ROOSEVELT ROAD e
CLEN ELLYN. lLLINOIS 60137 December 16, 1980 Those on Attached List:
The enclosed IE Information Notice No. 80-44 provides early notification of an event that may have safety sig,ificance. 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-mending or requesting specific licensee actions may be issued.
If you have any questions regarding this matter, please contact this office.
Sincerely, l
M.
ames G. Keppler#
Director
Enclosure:
IE Information Notice No. 80-44 8101070
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Docket No. 50-282 Docket No. 50-306 Northern States Power Company ATTN:
Mr. Dennis E. Gilberts Vice President Power Production and System Operation 414 Nicollet Mall Minneapolis, MN 55401 cc w/ encl:
F. P. Tierney, Jr., Plant Manager Central Files AD/ Licensing AD/ Operating Reactors AEOD Resident Inspector, RIII PDR Local PDR John W. Ferman, Ph.D.,
Nuclear Engineer, MPCA t
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SSINS No.
6835 oo Accession No.-
g 8012160001 IN 80-44 UNITED STATES NUCLEAR REGULATORY COMMISSION i
0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 December 15, 1980 IE INFORMATION NOTICE NO. 80-44:
ACTUATION OF ECCS IN THE RECIRCULATION MODE WHILE IN HOT SHUTOOWN PURPOSE:
The intent of this Information Notice is to alert PWR licensees and hol ers of construction permits of a potentially generic problem involving inadvertent actuation of the emergency core cooling system (ECCS) in the " Recirculation Mode" Such an event occurred at the Davis-Besse Nuclear Power Station (Decket No. 50-346) on December 5, 1980.
The plant was in a hot shutdown mode of opera-tion at the time of the event and was undergoing certain maintenance activities as described below.
DISCUSSION:
Just prior to the inadvertent actuation of the ECCS, the licensee was attempt-ing to isolate electrical shorts and/or grounds in the Safety Features Actua-tion System (SFAS).
Towards this end, A-C power had been removed from Channel 3 of the SFAS.
Upon reenergizing Channel 3 it was noted that an indicating lamp was out; therefore, an attempt was made to replace the failed lamp with a spare unit.
While removing a lamp from a spare output slot in a Channel 3 chassis, an arc was drawn between the lamp and the module chassis.
This arcing was apparent-ly due to a combination of shorts or grounds in the SFAS, which coupled with the " common" connection between Channel 1 and 3 resulted in the loss of a power supply in Channel 1.
Since all the bistable trips in Channel 3 had not been completely reset, and since a power supply to Channel 1 was lost, SFAS Levels 1, 2, 3 and 5 were actuated by the two-out-of four actuation logic.
Since SFAS Level 5 indicates that the Borated Water Storage Tank (BWST) is at a low level, the ECCS was placed in a recirculation mode (i.e., the ECCS suction was aligned to the emergency containment sump.)
In order to place the ECCS system in the recirculation mode, the supply valves leading to the Decay Heat Removal (OHR) pumps from the BWST start closing after those in the ECCS line and from the containment emergency sump fully open.
Thus, during this valve transition period, a flow path existed to the reactor coolant system (RCS) via the BWST and the ECCS pumping system (i.e., the DHR pumps); however, since the RCS pressure was higher than that of the pumping system (2100 vs. 1600 psig) no BWST water was pumped into the RCS.
- Rather, during the valve transition time of about 1-1/2 minutes, approximately 15,000 gallons of borated water was drained from the BWST to the containment-emergency sump.