ML20168A744
| ML20168A744 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 06/16/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1972-012-00 | |
| Download: ML20168A744 (4) | |
Text
PRECURSOR DESCRIPTION AND DATA NSIC Accession Number:
79565 Date:
December, 1972
Title:
Loss of Normal Station Power Causes Cooling System Transient at Vermont Yankee (Operations Report for December, 1972)
The failure sequence was:
- 1. An internal fault on the startup transformer resulted in a loss of offsite power.
- 2. This resulted in a reactor trip followed by a turbine trip.
- 3. The diesel generator started automatically and loaded essential busses.
- 4. The HPCI failed to autostart on high dry well pressure, but was manually initiated.
- 5. The reactor pressure rose to 1130 which resulted in the opening of 3 relief valves.
One relief valve failed to open.
One safety valve chattered on its seat about 100 psig. below its setpoint.
- 6. RCICIHPCI were used for decay heat removal and water level control.
- 7. No reason was given for the failure of HPCI to autostart. Failure of the fourth relief valve to lift was attributed to expansion of the valve's components.
Corrective action:
- 1. The chattering safety valve was replaced.
- 2. The failed relief valve components were replaced.
Design purpose of failed system or component:
- 1. Offsite power provides for station load when the unit is not generating electricity.
- 3. The relief valves are used for pressure control.
Unavailability of system per WASH 1400:
- HPCI:
8.6 -x lOY',/D RCIC:
8.0 X 10 2 /D Unavailability of component per WASH 1400:
- relief valve, failure to open: 1 x 105 /D Unavailabilities are in units of per demand D-1.
Failure rates are in units of per hour HR'1
An internal The reactor and The diesel HPCI fails to One out of 4 RCIC/Hl'CI are fault on the turbine trip generators auto-actuate relief valves.used for water startup 1start and at high drywell fails to open level control transformer load pressure results in a loop_________
Potential Severe Core Damage No No -
ADS/LPCI/CS available No No -
ADS/LPCI/CS available No ATWS NSIC 79565 -
Actual Occurrence of Loss of Normal Station Power Causes Cooling System Transient at Vermont Yankee
Loss of Reactor Diesel Reactor Made Sub- [RCIC/HPCI ADS/LPCI Long Offsite Scram Start and critical by the I Initciates Cs Term Power Load SBLCS Or Rods Are Initiates Core Manually Driven In ICooling Potential Severe Core Dama ge Sequence No.
No Yes No Yes Yes No Yes Yes No Yes No Yes Yes Yes Yes 1
2 3
4 5
6 7
8 9
10 11 12 13 14 15 NSIC 79565 -
Sequence of Interest of Loss of Normal Station Power Causes Cooling System Transient at Vermont Yankee
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBIER:
79565 DATE OF LER: December 1, 1972 DATE OF EVENT:
December, 1972 SYSTEM INVOLVED:
HPCI, ADS COMPONENT INVOLVED):
relief valve CAUSE:
Unspecified for HPCI, mechanical failure of valve components SEQUENCE OF INTEREST:
Loss of Offsite Power ACTUAL OCCURRENCE:
Loss of Normal Station Power REACTOR NAME:
Vermont Yankee DOCKET NUMBER:
50-271 REACTOR TYPE:
BWR DESIGN ELECTRICAL RATING:
514 NWe REACTOR AGE:
.8 yr VENDOR:
General Electric ARCHITECT-ENGINEERS:
Ebasco OPERATORS:
Vermont Yankee Nuclear Power Corp.
LOCATION:
5 miles S of Battleboro,. VT DURATION:
N/A PLANT OPERATING CONDIT ION:
63% power SAFETY FEATURE TYPE OF FAILURE:
(a) inadequate performance; (b) failed to start; Q made inoperable; (d)
DISCOVERY METHOD:
Operational Event COMMENT: