ML20161A179
| ML20161A179 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 06/09/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1981-033-00 | |
| Download: ML20161A179 (4) | |
Text
PRECURSOR DESCRIPTION AND DATA NSIC Accession Number:
171733 Date:
January 8, 1982
Title:
Unavailability of Three Auxiliary Feedwater Pumps at Zion 2 The failure sequence was:
- 1. With the reactor at 90% power and 2A turbine-driven AFW pump out of service for maintenance, water leaks from two hydrogen coolers in the unit generator resulted in
- a. generator trip and subsequent reactor trip.
- 2.
Motor-driven auxiliary feedwater pumps 2B and 2C failed to start and run on steam generator low-low level due to improperly sensed pump suction pressure.
(It was determined that, immediately after
- start, reverse flow existed in the pressure switch sensing line, resulting in a momentary low suction pressure indication when adequate pressure actually existed.)
- 3.
Both pumps were manually started.
Corrective action:
A time delay relay which momentarily bypasses the low suction pres-sure trip on pump start was added to the pump starting circuitry.
Design purpose of failed system or component:
- 1. The auxiliary feedwater system provides water for RCS cooling via the steam generators when the main feedwater system is unavailable.
- 2.
An alternate safety-related source of water is service water supplied to suction of auxiliary feedwater pumps at 100 psig.
Reactor at 90%
Water leaks from Motor-driven AFW Motor-driven power and 2A two hydrogen coolers pumps fail to auto-AFW pumps turbine-driven in the unit generator start and run on low-manually AFW pump out result in generator low steam generator started of service for trip and subsequent level due to low maintenance reactor trip suction pressure trip caused by improperly sensed suction pressure Potential Severe Core Damage No No - bleed and feed plus main feed-water recovery available No No NSIC 171733 - Actual Occurrence for Unavailability of Three Auxiliary Feedwater Pumps at Zion 2
Loss of Reactor Auxiliary PORV f
PORV or High Long Term Main Trip Feedwater and Demanded PORV Isola-Pressure Core Feedwater Secondary tion Valve Injection Cooling Heat Removal Closure Potential Severe Core Damage Sequence No.
No I
No 2
Yes 3
Yes 4
No 5
No 6
Yes 7
Yes 8
No 9
No 10 Yes 11 Yes 12 Yes 13 NSIC 171733 -
Sequence of Interest for Unavailability of Three Auxiliary Feedwater Pumps at Zion 2
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER:
171733 LER NO.:
81-033 DATE OF LER:
January 8, 1982 DATE OF EVENT:
December 11, 1981 SYSTEM INVOLVED:
Auxiliary feedwater COMPONENT INVOLVED:
Auxiliary feedwater pumps CAUSE:
One pump was unavailable due to maintenance and the other two pumps tripped due to incorrectly sensed low suction pressure on starting SEQUENCE OF INTEREST:
Loss of feedwater ACTUAL OCCURRENCE:
Unavailability of three AFW pumps following trip REACTOR NAME:
Zion 2 DOCKET NUMBER:
50-304 REACTOR TYPE:
PWR DESIGN ELECTRICAL RATING:
1040 MWe REACTOR AGE:
8.0 years VENDOR:
Westinghouse ARCHITECT-ENGINEERS:
Sargent & Lundy OPERATORS:
Commonwealth Edison LOCATION:
40 miles north of Chicago, Illinois DURATION:
360 h (estimated)
PLANT OPERATING CONDITION:
Cooldown TYPE OF FAILURE:
Failed to start DISCOVERY METHOD:
Operational event COMMENT: