ML20168A747
| ML20168A747 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 06/16/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1974-002-00 | |
| Download: ML20168A747 (4) | |
Text
PRECURSOR DESCRIPTION AND DATA NSIC Accession Nunber:
97107 Date:
October 31, 1974
Title:
BIT Auto-Injection Failure at Zion 2 Meets precursor criteria no:
The failure sequence was:
- 1. An instrument mechanic inadvertently tripped a RCS pump.
- 2. The resulting flow transient caused a reactor trip and SI signal.
- 3. Train A safeguards failed due to a loss of power.
- 4. The train B inlet valve to BIT failed to open.
Corrective action:
Valve stem was cleaned, packing was changed, and torque limits. were increased.
Design purpose of failed system or component:
BIT protects the core from a main steam pipe break.
Unavailability of system per WASH 1400:
Unavailability of component per WASH 1400: *valve, failure to operate:
1 x 10-3 /D safeguards, train A` 5.8 x 10-3 /D 125 VDC system:
1.1 x 10-6 /D Unavailabilities are in units of per demand D-1.
Failure rates are in units of per hour HR'1
RC pump Flow Reactor Auto' BIT Core goes j Potential tripped transient trip injection critical Severe
& SIS
& returns Core to powerJ Damage No No t No ATWS No NSIC 97107 -Actual Occurrence for Boron Injection-Tank Inlet Valve Failures at Zion 2 (BIT is primarily for main steam pipe break -
FSAR says no core melt for any pump trips.
tTo return to criticality would require the most reactive RCCA to be stuck fully withdrawn and end of core life negative co-lant temperature coefficient.)
Steam Line Break Reactor Steam Trip Generator Isolation Feedwae and Secondar Heat Removal High PORV Opened PORV or Long Potential Pressure Due to Con-PORV Isola-Term Severe Injection tinued HPI tion Valve Core Core Closure Cooling Damage No No Yes Sequence No.
2 3
No Possible (with worst case stuck rod)
No Yes Yes Yes Yes 4
5 6
7 8
9 10 NSIC 97107 -
Sequence of Interest for Boron Injection Tank Valve Failures at Zion 2
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER,:
97107 DATE OF LER:
October 31, 1974 DATE OF EVENT:
October 22, 1974 SYSTEM INVOLVED: Safety Injection COMPONENT INVOLVED: Valves -
2 CAUSE:
Power failure to one safeguards train and stuck valve on other train, (human error)
SEQUENCE OF INTEREST:
Main steam pipe break ACTUAL OCCURRENCE:
Instrument mechanic inadvertently tripped a RCS pump, operator error REACTOR NAME:
Zion 2 DOCKET NUMBER:
50-304 REACTOR TYPE:
PWR DlESIGN ELECTRICAL RATING:
1040 MWe REACTOR AGE:
0.8 yr VENDOR:
Westinghouse ARCHITECT-ENGINEERS:
Sargent & Lundy OPERATORS:
Commonwealth Edison Co.
LOCATION:
40O;.mile8snortk..-of Chicago, Ill.
DURATION:
360(a) hours PLANT OPERATING CONDITION:
57% power SAFETY FEATURE TYPE OF FAILURE:
(a) inadequate performance; (b) failed to start; 0
made inoperable; (d) _______
DISCOVERY METHOD:
Operational event COMMENT: