05000373/LER-2014-004
| Lasalle County Station, Unit 1 | |
| Event date: | 08-28-2014 |
|---|---|
| Report date: | 10-27-2014 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident |
| Initial Reporting | |
| 3732014004R00 - NRC Website | |
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LaSalle County Station Units 1 and 2 are General Electric Company Boiling Water Reactors with 3546 Megawatts Rated Core Thermal Power.
A. CONDITION PRIOR TO EVENT:
Unit(s): 1 / 2 Event Date: August 28, 2014 Event Time: 1227 CDT Reactor Mode(s): 1/1 Mode(s) Name: Power Operation Power Level: 100% / 100%
B. DESCRIPTION OF EVENT:
On August 28, 2014, both Units 1 and 2 were in Mode 1 at 100% power. The 'B' train of Auxiliary Electric Equipment Room ventilation (VE)[VI] was inoperable due to a planned repair of an oil leak. The Main Control Room ventilation envelope consists of both the Main Control Room and the Auxiliary Electric Equipment Room.
Both the Control Room HVAC (VC) and VE were required to be operable at the time of the occurrence.
Technical Specification (TS) 3.7.5 Required Action (RA) A.1 had been entered to restore the control room area ventilation (VC) air conditioning subsystem to operable status within 30 days.
At 1227 hours0.0142 days <br />0.341 hours <br />0.00203 weeks <br />4.668735e-4 months <br /> CDT, the Main Control Room received a start alarm on the Unit 1 plant process computer (PPC)[ID] for the 'A' train VE compressor. A check of the PPC computer point indicated that the 'A' train VE compressor was not running. The rounds operator responded to the area and reported that the 'A' train VE compressor was cycling on and off. The 'A' train of VCNE was declared inoperable. With both trains of VCNE inoperable, the Station entered TS 3.7.5 RA B.1 to verify control room area temperature less than 90 degrees once per four hours, and RA B.2 to restore one control room area ventilation AC subsystem to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
This occurrence is reportable under 10 CFR 50.73(a)(2)(v)(D) as an event or condition that could have prevented the fulfillment of the safety function of the structures or systems that are needed to mitigate the consequences of an accident. An ENS report was made to the NRC (EN# 50413) at 1726 CDT on August 28, 2014, pursuant to 10 CFR 50.72(b)(3)(v)(D).
This event constitutes a safety system functional failure for Unit 1 and 2.
C. CAUSE OF EVENT:
The cause of the event was a strand of wire that was grounding to the valve case on the liquid line solenoid valve (ORG053A). This caused the liquid line solenoid valve to close, resulting in the compressor shutting down on low suction pressure.
D. SAFETY ANALYSIS:
The safety significance of this event was minimal. The 'B' train of VCNE was repaired and restored to operable status at 2335 hours0.027 days <br />0.649 hours <br />0.00386 weeks <br />8.884675e-4 months <br /> on August 28, 2014. The approximately 11 hours1.273148e-4 days <br />0.00306 hours <br />1.818783e-5 weeks <br />4.1855e-6 months <br /> that both VCNE trains were inoperable is significantly less than the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Completion Time allowed by TS 3.7.5 Required Action B.2. Main Control temperature did not exceed 90 degrees, and online risk remained Green throughout the event.
E. CORRECTIVE ACTIONS:
- The oil leak on the 'B' train of VE was repaired, and the train was returned to service at 2335 hours0.027 days <br />0.649 hours <br />0.00386 weeks <br />8.884675e-4 months <br /> on August 28, 2014.
- The wiring problem on liquid line solenoid valve ORG053A was repaired, and the 'A' train of VCNE was returned to service at 0001 hours1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> on August 29, 2014.
F. PREVIOUS OCCURRENCES:
On November 22, 2013, both Units 1 and 2 were in Mode 1 at 100% power. The 'A' train of Main Control Room ventilation (VC) was inoperable due to an emergent repair of a Freon leak. TS 3.7.5 Required Action (RA) A.1 had been entered to restore the control room area ventilation AC subsystem to operable status within 30 days.
At 1920 hours0.0222 days <br />0.533 hours <br />0.00317 weeks <br />7.3056e-4 months <br /> CST, the Main Control Room received an Auxiliary Electrical Equipment Room (AEER) HVAC (VE) Panel Trouble Alarm. The rounds operator responded to the panel and reported that the 'B' AEER Cooler Condenser Fan trip alarm was in, and the fan (OVE03CB) was not turning. An acrid smell was detected coming from the fan motor breaker compartment. The 'B' train of VC and VE was declared inoperable.
With both trains of VCNE inoperable, the Station entered TS 3.7.5 RA B.1 to verify control room area temperature less than 90 degrees once per four hours, and RA B.2 to restore one control room area ventilation AC subsystem to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
The cause of the event was a winding failure of the 'B' AEER Cooler Condenser fan motor. Corrective actions included replacing the failed fan motor, and performing a failure analysis to determine the cause of the winding failure. These actions would not have prevented the cause of the August 28, 2014, inoperability of the 'A' train VE compressor.
G. COMPONENT FAILURE DATA:
There were no component failures associated with this event.