ML20147A542
| ML20147A542 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 05/26/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1981-037-00 | |
| Download: ML20147A542 (4) | |
Text
PRECURSOR DESCRIPTION AND DATA NSIC Accession Number:
171842 Date:
December 18, 1981
Title:
Failure of Emergency Diesel Generators at Dresden 3 The failure sequence was:
- 1.
On October 23,
- 1981, with the plant at 66% power, DG 2/3 tripped due to high cooling water temperature during surveillance.
Unit 3 DG was manually tripped due to high cooling water temperature indication during subsequent testing.
In both cases the DG cooling water pumps had tripped prior to the DG trips.
Both cooling water pumps were restarted and the diesels subsequently declared operable.
The cause of the pump trips was not determined at the time.
- 2.
On November 19,
- 1981, the unit 3 DG was again shut down during testing because of high coolant temperatures.
- 3.
Subsequent testing revealed that both the Unit 2/3 and Unit 3 cooling water pump discharge check valve disks had separated from the valve operating arms and restricted cooling water flow.
- 4.
During the event, DG U2, DG 2/3, 4-kV cross-tie, and offsite power were still available.
Corrective action:
- 1. The defective valves were replaced, the systems were satisfactorily tested and placed back in service.
- 2.
A procedure revision was to be initiated to inspect these valves annually.
Design purpose of failed system or component:
The diesel generator system provides emergency power to safety-related loads in the event that offsite power and the unit generator are unavailable.
Reactor at power Both diesel generators for Unit 3 declared inoperable during test due to insuf-ficient cooling caused by defective diesel cooling water pump discharge check valves Potential Severe Core Damage No -
offsite power, Unit 2 DG, and cross-tie were available No NSIC 171842 -
Actual Occurrence for Failure of Emergency Diesel Generators at Dresden 3
Loss of Reactor Diesel Standby RCIC/HPCI Automatic LPCI Long Offsite Scram Start Liquid
Response
Depressuri-or CS Term Power and Control Adequate zation
Response
Core Load Initiated System Adequate Cooling Operates Potential Severe Core Damage Sequence No.
No 1
Yes 2
3 No Yes Yes Yes 4
No S
6 7
8 9
Yes Yes No Yes Yes Yes Yes 10 11.
12 13 14 NSIC 171842 -
Sequence of Interest for Failure of Diesel Generators at Dresden 3
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER:
171842 LER NO.:
81-037 DATE OF LER:
December 18, 1981 DATE OF EVENT:
October 23, 1981 SYSTEM INVOLVED:
Emergency power COMPONENT INVOLVED:
Diesel generator cooling system check valves CAUSE:
Mechanical failure SEQUENCE OF INTEREST:
LOOP ACTUAL OCCURRENCE:
Diesel generators declared inoperable during test REACTOR NAME:
Dresden 3 DOCKET NUMBER:
50-249 REACTOR TYPE:
BWR DESIGN ELECTRICAL RATING:
794 MWe REACTOR AGE:
10.7 years VENDOR:
General Electric ARCHITECT-ENGINEERS:
Sargent & Lundy OPERATORS:
Commonwealth Edison Co.
LOCATION:
7 miles east of Morris, Illinois DURATION:
One half test interval before October 23 plus time interval between October 23 and November 19:
1000 h (estimated)
PLANT OPERATING CONDITION:
66% power TYPE OF FAILURE:
Inadequate performance; made inoperable DISCOVERY METHOD:
Surveillance testing COMMENT:
Also see Accession 170009, Dresden 3, 50-249, LER 81-033, Nov.
6, 1981.