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
IC Accession Number: 171842 te: December 18, 1981 e: Failure of Emergency Diesel Generators at Dresden 3 failure sequence was:
. 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.
On November 19, 1981, the unit 3 DG was again shut down during testing because of high coolant temperatures.
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.
During the event, DG U2, DG 2/3, 4-kV cross-tie, and offsite power were still available.
rrective action:
. The defective valves were replaced, the systems were satisfactorily tested and placed back in service.
A procedure revision was to be initiated to inspect these valves annually.
sign purpose of failed system or component:
The diesel generator system provides emergency power to safety-ated loads in the event that offsite power and the unit generator are available.
during test due to insuf- Core ficient cooling caused by Damage defective diesel cooling water pump discharge check valves 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
and Control Adequate zation Response Core Core Load Initiated System Adequate Cooling Damage Operates No 1 Yes 2 No 3 Yes 4 Yes S Yes 6 No 7 Yes 8 Yes 9 No 10 Yes 11.
Yes 12 Yes 13 Yes 14 NSIC 171842 - Sequence of Interest for Failure of Diesel Generators at Dresden 3
C ACCESSION NUMBER: 171842 NO.: 81-037 TE OF LER: December 18, 1981 E OF EVENT: October 23, 1981 TEM INVOLVED: Emergency power MPONENT INVOLVED: Diesel generator cooling system check valves USE: Mechanical failure UENCE OF INTEREST: LOOP UAL OCCURRENCE: Diesel generators declared inoperable during test CTOR NAME: Dresden 3 CKET NUMBER: 50-249 CTOR TYPE: BWR SIGN ELECTRICAL RATING: 794 MWe CTOR AGE: 10.7 years DOR: General Electric CHITECT-ENGINEERS: Sargent & Lundy RATORS: Commonwealth Edison Co.
ATION: 7 miles east of Morris, Illinois RATION: One half test interval before October 23 plus time interval between October 23 and November 19: 1000 h (estimated)
NT OPERATING CONDITION: 66% power E OF FAILURE: Inadequate performance; made inoperable COVERY METHOD: Surveillance testing MENT: Also see Accession 170009, Dresden 3, 50-249, LER 81-033, Nov.
6, 1981.