ML20147A338
| ML20147A338 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 07/14/1980 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1980-018-00 | |
| Download: ML20147A338 (4) | |
Text
C Accession Number: 158279 e: July 14, 1980
- Degraded Emergency Feedwater System During a Loss of Offsite er at Arkansas Unit 2 failure sequence was:
With the reactor at full power with atmospheric dump valves isolated due to vibration and failure to close problems, tornado activity resulted in the sequential loss of four of five offsite power lines. Protective relaying disconnected the remaining offsite power line from the bus tie autotransformer. (Offsite power was available through manual connection from the 161 kV transmission system.)
Both diesel generators started and powered safety-related loads.
Natural circulation was established with both emergency feedwater (EFW) pumps using a common suction from the condensate storage tanks and the startup and blowdown demineralizer effluent.
Approximately 15 min after the LOOP, emergency feedwater flow became erratic with flow rate oscillating between 80% and 100% of rated flow due to cavitation. This was caused by flashing of the startup and blowdown demineralizer effluent.
The startup and blowdown demineralizer effluent was isolated from the EFW pump suction and both EFW pumps were alternately stopped, vented, and restarted.
The process-computer was unavailable during the event. This is be-lieved to have been caused by protective trips from low voltage.
rrective action:
Offsite power was restored via startup transformers ST-2 and ST-3.
EFW system operating procedures were revised to require isolation of startup and blowdown effluent prior to exceeding 5% power.
ign purpose of failed system or component:
Offsite power provides the preferred source of power to safety-re-ed loads when the unit generator is not available. The EFW system vides water to the steam generators for RCS when the main feedwater em is unavailable.
vented loads effluent with CST flow Possible - however, bleed & feed could provide core cooling No Possible - however, bleed & feed could provide core cooling No
-Possible - however, bleed & feed could provide core cooling NSIC 158279 - Actual Occurrence for Degraded Emergency Feedwater System During a Loss of Offsite Power at nsas Unit 2
No I No 2 No 3 Yes 4 Yes 5 No 6 No 7 Yes 8 Yes 9 No 10 Yes 11 No 12 Yes 13 8279 - Sequence of Interest for Degraded Emergency Feedwater System During a Loss of Offsite Power Unit 2
ACCESSION NUMBER: 158279 NO.: 80-018 OF LER: July 14, 1980 OF EVENT: April 7, 1980 M INVOLVEDz Offsite power, emergency feedwater system ONENT INVOLVED: Transmission lines, both EFW pumps E: Tornado damage and failure of operating procedures to require isolation of the startup and blowdown effluent thereby allowing flashing to occur in EFW pump suction lines.
ENCE OF INTEREST: LOOP AL OCCURRENCE: LOOP and FW pump cavitation from hot demineralizer effluent causing flashing.
OR NAME: Arkansas Nuclear Unit 2 ET NUMBER: 50-368 TOR TYPE: PWR N ELECTRICAL RATING: 912 MWe OR AGE: 1.3 years OR: Combustion Engineering ITECT-ENGINEERS: Bechtel ATORS: Arkansas Power and Light TION: 6 miles NW of Russelville, Arkansas TION: N/A OPERATING CONDITION: 100% rate power OF FAILURE: Inadequate performance; made inoperable VERY METHOD: Operational event ENT: