ML20156A194
| ML20156A194 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 06/04/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1981-039-00 | |
| Download: ML20156A194 (4) | |
Text
C Accession Number: 168548 e: August 25, 1981
- Switchyard Voltage Drops Below Low Limit at Rancho Seco failure sequence was:
With the reactor in hot shutdown, excessive electrical demand resulted in a reduction in switchyard voltage to 206 kV. This is below the minimum voltage (214 kV) assumed for analysis.
The diesel generators were started and provided power to the safety-related buses.
rrective action:
Direct switchyard voltage indications and alarms were to be lled to facilitate control room monitoring of switchyard voltages.
ign purpose of failed system or component:
Offsite power provides the preferred source of power to safety-ated loads. The vital buses have 2 power supplies, offsite and ergency diesel generators.
Reactor in hot shutdown Diesel generators Potential and excessive load demand supply safety-related Severe results in reduction of loads Core switchyard voltage to Damage below 214-kV minimum voltage No V--
Possible - (Use of turbine-driven AFW train for natural circulation cooling may provide adequate core cooling)
NSIC 168548 - Actual Occurrence for Effective LOOP at Rancho Seco
Runs Back Power Secondary tion Valve Injection Core Core and Assumes Heat Removal Closure Cooling Damage House Loads 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 NSIC 168548 - Sequence of Interest for Effective LOOP at Rancho Seco
C ACCESSION NUMBER: 168548 NO.: 81-039 E OF LER: August 25, 1981 E OF EVENT: August 7, 1981 TEM INVOLVED: Offsite power PONENT INVOLVED: Switchyard SE: Low switchyard voltages due to excessive load demand UENCE OF INTEREST: LOOP UAL OCCURRENCE: Effective LOOP CTOR NAME: Rancho Seco KET NUMBER: 50-312 CTOR TYPE: PWR IGN ELECTRICAL RATING: 918 MWe CTOR AGE: 6.9 years DOR: Babcock & Wilcox HITECT-ENGINEERS: Bechtel RATORS: Sacramento Municipal Utility District ATION: 25 miles SE of Sacramento, California ATION: N/A NT OPERATING CONDITION: Shutdown E OF FAILURE: Inadequate performance; made inoperable OVERY METHOD: Operational event MENT: The safety feature equipment called upon was the DGs. They performed as designed and powered the vital buses. They did not experience inadequate performance or inoperability. Also see Accession 167117 (Rancho Seco, 50-312, LER 81-034, July 7, 1981).