ML20168A737
| ML20168A737 | |
| Person / Time | |
|---|---|
| Site: | Three Mile Island  |
| Issue date: | 06/16/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1978-LTR-00 | |
| Download: ML20168A737 (4) | |
Text
29, 1978 ty Injection Occurs at TMI-2 sequence was:
e power source feeder breakers to vital bus 2-IV (120 V a-c) were tripped y control module failed resulting in blown fuses in the DC input to s 2-IV tripped on invertor failure, resulting in the PORV failing open.
of the reactor coolant pump configuration at the tine, a reactor trip urred.
ators did not realize the relief valve had failed open because of lack position indication.
initiated at 1650 psig.
utes into the transient, vital bus 2-IV was re-energized, which closed ef valve and terminated the transient.
ction; change was initiated to change the failure position of the relief on loss of power to closed in lieu of open.
alve position indication was provided in the control room.
se of failed system or component:
120 V a-c power for loads which require uninterrupted power.
t operated relief valve provides overpressure protection for the RCS.
ty of system per WASH 1400:
- N/A ty of component per WASH 1400: *solid state device, high power application: 3 x 10-6 /hr.
labilities are in units of per demand D-1. Failure rates are in hour HR-1 .
failure & failed closed cation powered intervention 2-IV Severe vital bus opening relief from vital bus successful reenergized Core 2-IV trip valve 2-IV available closing Damage
& reactor to operator relief valve trip & terminating
_____________ CS blowdown No No No No -reactor at power No No 097 - Actual Occurrence for Loss of Vital Bus and Relief Valve Opening at Three Mile Island 2
Small Reactor Aukiliary High Low Pressure Potential Sequence LOCA Trip Feedwater and Secondary Heat Removal jInjection Pressure Recirculation and LPR/HPI Cross-connect Severe Core Damage No.
2 3
4 5
6 7
NSIC 141097 - Sequence of Interest for Safety Injection Occurs at Three Mile Island 2
- failure requires operator error of failing to close the PORV isolation valve.
CATEGORIZAtTION OF ACCIDENT SEQUENCE PRECURSORS CESSION NUMBER: 141097 LER: June 27, 1978 EVENT: March 29, 19,78 NVOLVED: 120 V a-c vital power, ACS T INVOLVED: Vital bus invertor Blown fuse, faulty invertor control module OF INTEREST: small LOCA - stuck open PORV CCURRENCE: stuck open PORV NAME: Three Mile Island 2 NUMBER: 50-320 TYPE: PWR ELECTRICAL RATING: 906 MWe AGE: 0.0+ yr Babcock & Wilcox CT-ENGINEERS: Burns & Roe S: Metropolitan Edison Co.
- N/A PERATING CONDITION: Zero power physics testing FEATURE TYPE OF FAILURE: (a) inadequate performance; (b) failed to start; (c) made inoperable; G~)ailed inunafe position RY METHOD: incident during physics testing
- Vital bus tripped because of invertor failure while alternate power source was removed for testing.