ML19305E757
| ML19305E757 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 05/12/1980 |
| From: | Pappas H NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Hines E DETROIT EDISON CO. |
| References | |
| NUDOCS 8005200367 | |
| Download: ML19305E757 (1) | |
Text
8005200567 f
g UNITED STATES Q
NUCLEAR REGULATORY COMMISSION g '
37 g
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799 ROOSEVELT ROAD 3
o, GLEN ELLYN, ILLINOIS 60137
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o Docket No. 50-341 The Detroit Edison Company ATTN:
Mr. Edward Hines, Assistant Vice President and Manager Quality Assurance 2000 St.cond Avenue Detroit, MI 48226 Gentlemen:
Due to an oversight, the attached " Enclosure A" to IE Information Notice No. 80-20 was omitted from our letter dated May 8, 1980.
Sincerely, Helen Pappas, Chief Administrative Branch
Enclosure:
Attachment A to IE Information Notice No. 8C 20 cc w/ enc 1:
Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Ronald Callen, Michigan Public Service Commission Eugene B. Thomas, Jr.,
Attorney
IE Information Notice No. 80-20 Enclosure A I
DAVIS-BESSE EVENT OF APRIL 19. 1980 STATUS OF DAVIS-BESSE 1 PRIOR TO LOSS OF POWER TO BUSSES E-2 AND F-2:
1.
Refueling mode with RCS temperature at 90 F and level slightly below vessel head flange.
Head detensioned with bolts in place.
Manway cover
~
on top of OTSG removed.
Tygon tubing attached to lower vents of RCS hot leg for RCS level indication.
Decay heat loo, 2 in service for RCS 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 consected.
RPS and SFAS 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.
SEQUENCE OF EVENTS TIME EVENT CAUSE/ COMMENTS 2:00 p.m.
Loss 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 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 (STAS),
the computer, and much of the control room indicaters.
2:00 p.m.
SEAS Level 5 (recircu-Two out of four logic tripped upon loss lation acde) actua-of Busses E-2 and F-2.
Actuation caused tion.
ECCS pump suction valves from containment sump to open and ECCS pump suction valves from Borated 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 NNI.
This restored all essential power for ECCS.
=
. TIMI EVENT CAUSE/ COMMENTS 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, prcgressed 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 fitr bypassing f: 1956r. '"" "* ' 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.
6:24 p.m.
DH flow directed RCS cooldown established at less than 25 F through cooler per hour.
RCS tew e_racure at 150 F. Incore Ti range from 151 to U 80F.
9:50 p.m.
Power completely RCS temperature at approximately 115 F.
restored STATUS OF DAVIS.BESSE 1 AFTER RECOVERY FROM LOSS OF POWER 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 Ing for RCS level indication.
Decay heat loop 2 in service for RCS cooling.
2.
Bus E-2 being supplied from 13.8 KV 3us A via breaker HAAE2 and Bus F-2 being supplied from 13.8 KV Bus 3 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-93) frem containment sump closed and breakers racked out.
This will prevent the suction of air into the decay
(
e 4
3 heat loop during a level 5 actuation (recirculation mode) when there is no water in the. sump.
5.
Equipment out of Service:
Emergency Diesel Generator 1 - maintenance 6.
Breakers for containment spray and HFI pumps racked out.
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