ML20168A435
| ML20168A435 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 06/16/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1973-001-00 | |
| Download: ML20168A435 (4) | |
Text
PRECURSOR DESCRIPTION AND DATA NSIC.Accession Number:.
85566 Date-
Title:
Complete Loss of a.c. Power Causes RCIC and HPCI to be Inoperable.
The failure sequence was:
- 1. In preparation for the turbogenerator trip and loss of offaite power test, the 4 kv unit boards were plated in maual to prevent automatic transfer.
- 2. The turbine was manually tripped because of increased vibration.
This resulted in a scram since offsite power could no longer be supp-lied, (because of lY
- 3. The RCIC and the HPCI systems could not be started until the standby diesels were energized, since their rest logic required a.c. power.
Corrective action:
The power source for some RCICIHPCI relays was changed and the manual reset was eliminlated.
Design purpose of failed system or component:
- 1. RCIC provides a source of water should the reactor become isolated.
Unavailability of system per WASH 1400:- RCIC: 8.0 x 10-2 /1)
IIDCI: 8.8 x lO72 /ID Unavailability of component per WASH 1400:
Unavailabilities are in units of per demand D-1.
Failure rates are In units of per hour 1R-1.
Turbine Trip Loop The Operator Manually Trips The Diesel Generators Load RCIC/HPCI Manually Test Underway Turbine Because Of Increasing Emergency Buses Reset And Supply Vibration And Offsite Power Cooling Water Is Lost Potential Severe Core Damage A
i 1
~-
No Yes Yes No NSIC 85566 -
Actual Occurrence of Complete Loss of Plant A.C. Power Causes RCIC and HPCI to be Unavailable
Loss of Reactor Diesel Reactor Made Sub-1RCIC/HPCI ADS/LPCI Long Offsite Scram Start and critical by the Iinitiates CS Term Power Load SBLCS Or Rods Are Initiates Core IManually Driven In jCooling Potential Severe Core Damage Sequence No.
No Yes No Yes Yes No Yes Yes No Yes No Yes Yes Yes Yes 1
2 3
4 5
6 8
9 10 11 12 13 14 15 NSIC 85566 -
Sequence of Interest for Complete Loss of Plant A.C. Power Caused RCIC and HPCI to be Inoperable at Browns Ferry 1
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUM-'BER:
85566 DATE OF LER:
November 19, 1973 DATE OF EVENT:
SYSTEM INVOLVED:
RCIC/IiPCI COMPONENT INVOLVED: RCIC/HPCI tripping logic CAUSE:
Design error SEQUENCE OF INTEREST:
Loss of Feedwater Flow ACTUAL OCCURRENCE:
Complete Loss of a.c. Power Causes RCIC and HPCI to be inoperable.
REACTOR NAME:
Browns Ferry 1 DOCKET NUfBER:
259 REACTOR TYPE:
BWR DESIGN ELECTRICAL RATING: 1065 e
REACTOR AGE: -18 yr VENDOR:
General Electric ARCHITECT-ENGINEERS:
TVA OPERATORS:
TVA LOCATION:
10 miles NW of Decatur, AL DURATION:
N/A PLANT OPERATING CONDITION:
Just scrammed during testing SAFETY FEATURE TYPE OF FAILURE:
(a) inadequate performance; (b) failed to start;
@Omade inoperable; (d) ___________
DISCOVERY METHOD:
Operational Event.
COYýh!ENT: Common Mode Design Error, a.c. requirement.