ML19305E759
| ML19305E759 | |
| Person / Time | |
|---|---|
| Site: | La Crosse File:Dairyland Power Cooperative icon.png |
| Issue date: | 05/12/1980 |
| From: | Pappas H NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Linder F DAIRYLAND POWER COOPERATIVE |
| References | |
| NUDOCS 8005200371 | |
| Download: ML19305E759 (1) | |
Text
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UNITED STATES e
[\\,".,.,g['g NUCLEAR REGULATORY COMMISSION Q
- 1 e REGION 111
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799 ROOSEVELT ROAD
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j' cLEN ELLYN, ILLINOIS 60137 Docket No. 50-409 Dairyland Power Cooperative ATTN:
Mr. F. W. Linder General Manager 2615 East Avenue - South La Crosse, WI 54601 Gentlemen:
Due to an oversight, the attached " Enclosure A" to IE Information 1
Notice No. 80-20 was omitted from our letter dated May 8, 1980.
Sincerely, ftA< YA W Helen Pappas, Chief Administrative Branch 1
Enclosure:
Attachment A to IE Information Notice No. 80-20 cc w/ enc 1:
Mr. R. E. Shimshak, j
Plant Superintendent Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Mr. John Duffy, Chief Boiler Inspector, Department of Industry, Labor and Human Relations
IE Information Notice No. 80-20 Enclocure A DAVIS-BESSE EVENT OF APRIL 19, 1980 STATUS OF DAVIS-BESSE 1 PRIOR TO LOSS OF PC'JER TO BUSSES E-2 AND F-2:
1.
Refueling mode with RCS temperature at 90 F and level slightly below vessel head flange.
Read detensioned with bolts in place.
Hanway cover on top of OTSG removed.
Tygon tubing attached to lower vents of RCS hot leg for RCS level indication. Decay heat loop 2 in service for RCS l
cooling.
2.
All non-nuclear instrument (NNI) power and Static Voltage Regulator YAR supplied from 13.8 KV Bus B via HBBF2.
13.8 K Bus A energized but not connected.
RPS and SEAS Channels 1 and 3 being supplied from YAR.
3.
Equipment Out of Service a.
Source Range Channel 2 - Surveillance b.
Emergency Diesel Generator 1 - Maintenance.
c.
Decay Heat Loop 1 - Maintenance.
4.
Breakers for containment spray and HPI pumps racked out.
SEOUENCE OF EVENTS TIME EVENT CAUSE/ COMMENTS 2:00 p.m.
Loos of power to Ground short on 13.8 KV breaker HBBF2 Busses E-2 and F-2 which caused breaker to open.
This (non-essential 480 interrupted power to busses E-2 and F-2 l
VAC) which were supplying all non-nuclear' instrument (NNI) power, channels 1 and 3 of the Reactor Protection System (RPS) and
.the Safety Features Actuation Signal (SFAS),
the computer, and much of the control room indicators.
2:00 p.m.
SFAS Level 5 (recircu-Two out of four logic tripped upon loss lation nede) actua-of Busses E-2 and F-2.
Actuation caused tion.
ECCS pump suction valves from containment aump to open and ECCS pump suction valves from Berated Water Storage Tank to close.
During valve travel times, gravity flow path existed from BWST to containment sump.
2:02 p.m.
Decay Heat (low Operator turned off only operating DH pressure safety in-pump to avoid spillage of RCS water to jection) flow secured containment via the tygon tubing for RCS by operator level indication and open SG manway.
2:33 p.m.
Partial restoration of power Power to Bus E 2 and SFAS channels 1 and 3 restored along with one channel of 551.
This restored all essential power for ECCS.
. TIME EVENT CAUSE/COMTENTS 2:44 p.m.
Attempt to reestab-Started DH pu=p 1-2 then stopped it when lish DH flow it was determined that air was in suction line.
Pump secured to prevent da= age.
3:34 p.m.
Source Range Channel 2 energized.
4:00 p.m.
Restoration of Busses Busses restored sequentually as efforts to (480 VAC) F-2, F-21, progressed to isolate ground fault.
4:06 p.m.
F-22, and F-23 4:25 p.m.
DH flow restored DH pump 1-2 started af ter venting.
RCS temperature at 170 F.DH flow bypassing 18 1756r. '"" "* 'C '
- b* *" 8 """*" '"d ""***""
4:46 p.m.
Containment sump Precautionary measure to assure containment pump breakers sump water from BWST remained in gentainment, opened Incore TC's range from 161 to 164 F.
5:40 p.m.
Computer returned to Incore TC's range from 158 to 160 F.
service.
l
~
6:24 p.m.
DH flow directed RCS cooldown established at less than 25 F through cooler per hour.
RCS te erature at 150 F. Incore Ti rangefrom151toiS80F.
9:50 p.m.
Power completely RCS temperature at approximately 115 F.
restored STATUS OF DAVIS-BESSE 1 AFTER RECOVERY FROM LOSS OF p0WER TO BUSSES E-2 AND F-2:
1.
Refueling mode with RCS temperature at 115 F and level slightly below vessel he flange.
Head detensioned with bolts in place.
Manway cover on top of OTSC removed.
Tygon tubing attached to lower vents of RCS hot leg for RCS level indication.
Decay heat loop 2 in service for RCS cooling.
2.
Bus E-2 being suppAicd from 13.8 KV 3us A via breaker RAAE7e and Eus F-2 being supplied from 13.6 KV Bus B via breaker HBBF2.
3.
Decay heat loop filled, all tags clear.
Maintenance work restricted so restoration of system will be less than two hours.
4.
ECCS pump suction valves (DH-9A and DH-9B) from containment sump closed and breakers racked out.
This will prevent the suction of air into the decay
i a'
3-heat loop during a level 5 actuation (recirculation mode) when there is no water in the.aump.
5.
Equipment out of service:
Emergency Diesel Generator 1 - maintenance 6.
Breakers for containment spray and EFI pumps racked out.
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