ML20168A731
| ML20168A731 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 06/16/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1977-026-00 | |
| Download: ML20168A731 (4) | |
Text
PRECURSOR DESCRIPTION AN~D DATA NSIC Accession Number:
125563 Date:
May 16, 1977
Title:
Offsite Power Lost at St. Luicie 1 The failure sequence was:
- 1. Fifteen minutes after a manual reactor trip due to grid system undervoltage condition occurred which caused the pumps to trip.
disturbances, a reactor coolant
- 2. Both diesel-generators started and loaded.
- 3. The reactor was cooled down using natural circulation until off-site power was restored (approximately 20 minutes).
- 4. One hour later, off-site power was again lost and natural circulation cool-down was used until off-site power was restored (one to one-and-a-half hours later).
Corrective action; None Design purpose of failed system or component:
- 1. Off-site power provides the preferred source of electric power to safety-related equipment when the unit generator is not in operation.
Unavailability of system per WASH.140G:
loss of offsite power:
2 x 10-5 /hr Unavailability of component per WASH 1400:*
i*Unavailabilitie are in units of per demand D-1.
Failure rates are in units of per hour HR-
Reactor manually Loss of off-Two of two diesel-Two of two motor-Turbine-driven tripped due to site power generators start driven AFW pumps AFW pump provides grid disturbances and assume safety-provide AFW flow AFW flow to steam related loads to steam generators generators Potential Severe Core Damage No No Yes No NSIC 125563 -. Actual Occurrence for Off-Site Power Lost at St. Lucie 1 specific pumps providing AFW flow not specified.
Loss of Turbine Emer-Auxiliary PORV PORV or High Long Offsite Generator gency Feedwater and Demanded PORV Isola-Pressure Term Power Runs Back Power Secondary tion Valve Injection Core and Assumes Heat Removal Closure Cooling House Loads Potential Severe Core Damage No Sequence No.
2 3
4 5
6 7
8 9
10' 11 12 13 NSIC 125563 - Sequence of Interest for Off-Site Power Lost at St. Lucie 1 not included in mitigation procedures.
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NU~MBER:
125563 DATE OF LER:
June 16, 1977 DATE OF EVENT:
May 16, 1977 SYSTE'M INVOLVED:
off-site power COIMPONIENT INVOLVED:
unknown CAUSE:
unknown SEQUENCE OF INTEREST:
loss of offsite power ACTUAL~ OCCURRENCE:
reactor trip with loss of off site power REACTOR NAkEE:
St. Lucie 1 DOCKET NUMBER:
50-335 REACTOR TYPE:
pWR DESIGN ELECTRICAL RATING:
802 MWe REACTOR AGE:
1.1 yr VENDOR:
Cbmbustion Engineering ARCHITECT-ENGINEERS:
Ebasco OPERATORS:
Florida Power & Light Co.
LOCATION:
12 muilea. SEA,f.J.ort. 1ierce, Fla.
DURATION:
N/A PLANT OPERATING CONDITION:
tripped prior to loss of off-site power SAFETY FEATURE TYPE OF FAILURE:
(a) inadequate performance; (b) failed to start; 0
made inoperable; (d)
DISCOVERY METHOD:
during operation COMMENT:
LER does not specify which AFW system components were used to provide core cooling.