ML20149K381
| ML20149K381 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 05/28/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1980-006-00 | |
| Download: ML20149K381 (5) | |
Text
PRECURSOR DESCRIPTION AND DATA NSIC Accession Number:
158232 Date:
June 17, 1980
Title:
LOOP at Indian Point 2 The failure sequence was:
- 1. With the plant at full power, lightning struck a 345 kV/138 kV transmission tower between two substations.
- 2.
A transmission tower shield line fell, which faulted four feeder lines, resulting in the loss of all external grid system supplies to the Buchanan Substation.
- 3.
Two gas turbines previously brought on line as part of Con Edison's storm watch contingency operations were insufficient to supply the load connected to the "islanded" Buchanan Substation and tripped off following the loss of all 138 kV supplies to the Buchanan Substation.
- 4.
This loss of power at Buchanan directly caused the two 6.9 kV buses normally fed from offsite power to deenergize, along with their associated 480 V buses at IP2.
The remaining four 6.9 kV buses (and the two remaining safeguards 480 V buses) which are normally supplied directly from the IP2 unit output via the unit auxiliary transformer remained energized since the unit was still online.
- 5.
The three emergency diesels automatically started, as designed, upon the loss of a 480 V bus caused by loss of the 6.9 kV buses.
- 6.
Loss of one of the two 480 V buses associated with the loss of the two offsite 6.9 kV buses also caused a loss of the rod position in-dication system and a subsequent turbine runback to 70% power per design; core Tave increased.
- 7.
The condenser steam dump system operated resulting in a decreased core Tave.
- 8.
The operator began a manual plant shutdown (manual turbine trip).
An auto trip from the LOOP occurred first by the opening of breaker 7 in the North 345 kV ring bus at Buchanan, thereby disconnecting the Indian Point 2 main generator from the electrical grid and deenergizing the remaining 6.9 kV buses.
This caused an auto-generator/turbine trip, loss of power to all four reactor coolant pumps via loss of the remaining 6.9 kV buses and the deenergizing of the remaining 480 V buses.
- 9.
When the main generator tripped, the idling emergency diesel generators closed onto and energized the 480 V buses.
- 10.
With loss of all RCPs, RCS natural circulation cooling was begun.
Gas turbine GT-1 was started and placed on standby.
- 11.
A spurious signal from steam line break instrumentation initiated engineered safegards equipment.
(Mismatched flow through atmospheric steam dump valves.)
- 12.
All ESF systems functioned properly.
Corrective action:
Offsite power was restored.
Design purpose of failed system or component:
Offsite power provides the preferred source of power to safety-related loads when the unit generator is not available.
Reactor at Two previously Loss of power Loss of the Operator Generator trip Emergency Spurious power and started gas to two 6.9-kV 480-V buses initiates and subsequent generators safety lightning turgine genera-and two 480-V results in 70%
manual reactor/tur-energize injection strike tors trip due buses results turbine run-turbine bine trip from safety-due to results in to loss of in diesel back and loss trip breaker open-related steam line loss of 138-kV supply generator of rod posi-ing on north buses differential four at Buchanan start tion indica-ring bus; pressure feeder substation tion loss of all lines 6.9-kV buses Potential Severe Core Damage No No No - turbine driven AFW train available No NSIC 158232 -
Actual Occurrence for Loss of Offsite Power at Indian Point 2
Loss of Turbine Fmer-Auxiliary PORV PORV or High Long Offsite Generator gency Feedwater and Demanded PORV Isola-Pressure Term Power Runs Back Power Secondary tion Valve Injection Core and Assumes Heat Removal Closure Cooling House Loads.
Potential Severe Core Damage Sequence No.
No No No 1
3 Yes Yes 4
5 No No 6
Yes Yes 8
9 No Yes No Yes 10 11 12 13 NSIC 158232 -
Sequence of Interest for Loss of Offsite Power at Indian Point 2
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER:
158232 LER NO.:
80-006/99T Rev.
1 DATE OF LER:
June 17, 1980 DATE OF EVENT:
June 3, 1980 SYSTEM INVOLVED:
Offsite power system COMPONENT INVOLVED:
Transmission lines CAUSE:
Lightning strike on transmission tower SEQUENCE OF INTEREST:
LOOP ACTUAL OCCURRENCE:
LOOP REACTOR NAME:
Indian Point 2 DOCKET NUMBER:
50-247 REACTOR TYPE:
PWR DESIGN ELECTRICAL RATING:
873 MWe REACTOR AGE:
7.0 years VENDOR:
Westinghouse ARCHITECT-ENGINEERS:
United Engineers and Constructors OPERATORS:
Consolidated Edison LOCATION:
25 miles north of New York, New York DURATION:
N/A PLANT OPERATING CONDITION:
Full power TYPE OF FAILURE:
Made inoperable DISCOVERY METHOD:
Operation event COMMENT:
LER revised Sept.
5, 1980; see LER-80-006/99X-1.