ML20147A482
| ML20147A482 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 05/26/2020 |
| From: | Christopher Hunter Office of Nuclear Reactor Regulation |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1980-027-00 | |
| Download: ML20147A482 (5) | |
Text
C Accession Number: 158650 e: June 3, 1980 le: Failure of Service Water System Plus Subsequent Auxiliary Feedwater System Unavailability at Calvert Cliffs I failure sequence was:
With the plant at 100% power, the No. 12 service water subsystem was removed from service for heat exchanger saltwater side cleaning. The heat exchanger service water side outlet valve was closed.
A complete failure occurred in one of the No. 11 instrument air compressor aftercooler tubes. The air compressor after cooler is cooled by a common portion of the service water system (during safeguards actuation, the common portion of the service water system is isolated from the two redundant safety-related portions).
The tube leak allowed compressed air to enter the service water system. The constant vent valves on the operating header were designed to maintain the service water system free of air.
However, air accumulated in the idled heat exchanger because the rate of leakage exceeded the capacity of that of the two constant vent valves.
When the idled heat exchanger was returned to service, the air bubble was released and, since the service water systems are not independent in the turbine building. Both No. 11 and No. 12 service water pumps lost suction.
The operator received low pressure alarms on both service water subsystems and verified that valve lineups were correct.
The reactor was manually tripped due to high main turbine bearing temperatures. All reactor coolant pumps, auxiliary feedwater pumps and the main condenser remained operable and were utilized to remove decay heat.
During the shutdown, No. 12 condensate storage tank (CST) was used to supply AFW to the steam generators.
When low level was indicated in No. 12 CST, flow was switched to No. 11 CST and No. 12 CST was isolated.
Later, the main feed system was restored to operation on auxiliary steam and the AFW system was shut down. The control room operator incorrectly designated the CST valves to be realigned.
Due to the valve realignment error, No. 11 and 12 CSTs were both isolated, rendering the auxiliary feedwater system unavailable.
rrective action:
Service water was isolated from the affected compressor; the system was vented, and normal flow was restored.
The No. 12 CST was properly aligned for service 3 h after the operator error was made.
subsystems to service.
gn purpose of failed system or component:
The service water system provides cooling water for turbine-side onents as well as the diesel generators, containment coolers, and t fuel pool coolers.
The auxiliary feedwater system provides water for steam generator ing in the event the main feedwater system is unavailable.
gress exchanger service feedwater flow is returned to water system pro- terminated service cooling vides SG and MFW cooling system started for SG cooling No No SIC 158650 - Actual Occurrence for Failure of Service Water System and Subsequent Auxiliary Feedwater ilability at Calvert Cliffs 1
No I No 2 No 3 Yes 4 Yes 5 No 6 No 7 Yes 8 Yes 9 No 10 Yes 11 No 12 Yes 13 158650 - Sequence of Interest for Failure of Service Water System and Subsequent Auxiliary Feedwater lity at Calvert Cliffs 1
IC ACCESSION NUMBER: 158650 R NO.: 80-027 TE OF LER: June 3, 1980 TE OF EVENT: May 20, 1980 TEM INVOLVED: Service water system, auxiliary feedwater system MPONENT INVOLVED: Air compressor aftercooler, condensate storage tank USE: Air leakage to service water system due to aftercooler tube failure, operator error in realigning valves when switching from one CST to another UENCE OF INTEREST: LOOP UAL OCCURRENCE: Loss of service water and subsequent unavailability of auxiliary feedwater CTOR NAME: Calvert Cliffs Unit 1 CKET NUMBER: 50-317 CTOR TYPE: PWR SIGN ELECTRICAL RATING: 845 MWe CTOR AGE: 5.6 years DOR: Combustion Engineering CHITECT-ENGINEERS: Bechtel RATORS: Baltimore Gas Electric ATION: 40 miles south of Annapolis, Maryland RATION: 3 h NT OPERATING CONDITION: 100% power E OF FAILURE: Made inoperable COVERY METHOD: Operational event and operator inspection MENT: See also NSIC 157124 (for Arkansas Nuclear One, 50-368, April 24, 1979).