ML20147A330
| ML20147A330 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 07/17/1980 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1980-015-01 | |
| Download: ML20147A330 (5) | |
Text
C Accession Number: 163499 e: July 17, 1980
- Reactor Coolant Pump Seal Failure at Arkansas Nuclear I failure sequence was:
With the reactor at 86% power, reactor coolant pump (RCP) "C" seal failed, resulting in excessive RCS leakage to the containment.
A controlled power reduction was begun, and approximately one-half hour later letdown was secured to reduce RCS inventory loss. RCS leak was estimated to be 10-20 gpm.
RCS leak rate increased during the power reduction and the plant was subsequently rapidly taken off line. RCP "C" was tripped after the turbine was taken off line but with the reactor critical.
RCS leak rate increased substantially when RCP "C" was tripped, and the RCP "C" lift pumps were started and stopped four times in succession in an attempt to reduce the leak rate. On the fourth attempt a reduction in leak rate was noticed. RCS leak rate had increased to a maximum of approximately 350 gpm.
The reactor was manually tripped and HPI pumps B and C started and all HPI valves opened to provide RCS makeup. The RCP "C" seal return line was isolated to prevent inventory loss through that line and RCP seal flow increased to quench the steam/water leaking by the failed seal.
A one-half psi increase in containment pressure occurred and the reactor building emergency coolers were put in service to minimize the pressure increase.
One HPI pump was secured and the HPI valves closed 1.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> after the seal failure. Two HPI pumps were used to provide continued RCS makeup from the BWST.
Individual SLBIC trains were inadvertently initiated twice during the cooldown, resulting in start of the turbine-driven EFW pump.
This pump was subsequently stopped and the auxiliary feedwater pump lined up to feed the steam generators.
During the RCS cooldown, containment entry was required to isolate the two core flood tanks to prevent their discharging into the RCS below 600 psig. A decrease in core flood tank level of 18 in. and 12 in. occurred prior to effecting isolation.
Throughout the incident a greater than 100'F margin to saturation existed. Approximately 60,000 gallons of water collected in con-tainment.
rective action:
The failed seal was examined and extensive damage observed. The cause of the damage could not be identified with certainty.
valve controls were relocated outside containment to facilitate access.
sign purpose of failed system or component:
The RCP seals provide a pressure boundary against RC system pressure the rotating shaft of the pump.
off line and sulting in provide at RCS pres-k RCP "C" some reduction makeup sure of tripped in leak rate 600 psig No No No No No No No - operating makeup pump sufficient for makeup 63499 - Actual Occurrence for Reactor Coolant Pump Seal Failure at Arkansas Nuclear 1
Small Reactor Auxiliary High Low Pressure Potential Sequence LOCA Trip Feedwater and Pressure Recirculation Severe No.
Secondary Injection and LPR/HPI Core Heat Removal Cross-Connect Damage No 1 Yes 2 Yes 3 No 4 Yes 5 Yes 6 Yes 7 NSIC 163499 - Sequence of Interest for Reactor Coolant Pump Seal Failure at Arkansas Nuclear 1
C ACCESSION NUMBER: 163499 NO.: 80-015 Rev. I E OF LER: July 17, 1980 E OF EVENT: May 10, 1980 TEM INVOLVED: Reactor coolant system PONENT INVOLVED: Reactor coolant pump seals SE: Seal failure UENCE OF INTEREST: Small break LOCA UAL OCCURRENCE: RCP "C" seal failure CTOR NAME: Arkansas Nuclear 1 KET NUMBER: 50-313 CTOR TYPE: PWR IGN ELECTRICAL RATING: 850 MWe CTOR AGE: 5.8 years DOR: Babcock & Wilcox HITECT-ENGINEERS: Bechtel RATORS: Arkansas Power & Light ATION: 6 miles NW of Russellville, Arkansas ATION: N/A NT OPERATING CONDITION: 86% power E OF FAILURE: Inadequate performance OVERY METHOD: Operational event MENT: See also: NSIC 165417 Arkansas Nuclear 1, 50-313, LER 80-015R, April 13, 1981, and Nuclear Safety, Vol. 22, No. 2, March-April 1981, pp. 237-238.