05000373/LER-2014-002
| Lasalle County Station Unit 1 | |
| Event date: | 03-29-2014 |
|---|---|
| Report date: | 05-23-2014 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident |
| Initial Reporting | |
| 3732014002R00 - NRC Website | |
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LaSalle County Station Unit 1 is a General Electric Company Boiling Water Reactor with 3546 Megawatts Rated Core Thermal Power.
A. CONDITION PRIOR TO EVENT:
Unit(s): 1 Reactor Mode(s): 1 Event Date: March 29, 2014 Event Time: 1620 CDT Mode(s) Name: Power Operation Power Level: 100%
B. DESCRIPTION OF EVENT:
On March 29, 2014, Unit 1 was in Mode 1 at 100% power. At 1620 hours0.0188 days <br />0.45 hours <br />0.00268 weeks <br />6.1641e-4 months <br /> CDT, the Division 3 Core Standby Cooling System (CSCS) Pump Room, Switchgear Room, and Battery Room Ventilation system [VF] failed in such a manner that heat could not be removed from the rooms. Due to the lack of ventilation in the Division 3 Switchgear Room, the High Pressure Core Spray (HPCS) [BG] system was declared inoperable and Condition B of Technical Specification (TS) 3.5.1 was entered.
TS 3.5.1 Required Action (RA) B.1, which verifies by administrative means, that Reactor Core Isolation Cooling (RCIC) [BN] is operable, was immediately entered and completed. TS 3.5.1 RA B.2 was entered to restore the HPCS system to an operable status within 14 days.
HPCS was restored to an available status at 1745 CDT on March 29, 2014 by manually wiring the 1VD18Y, Division 3 CSCS Ventilation Recirculation Damper, open.
The cause of the event was failure of the hydramotor pump bearing for the 1VD19Y, Division 3 CSCS Ventilation Return Fan Outlet Damper. The loss of hydraulic pressure in the hydramotor resulted in the 1VD19Y damper failing in the closed position.
The corrective action for the event was the replacement of the hydramotor for the 1VD19Y damper.
Hydramotor replacement and testing was completed and HPCS restored to operable at 1615 CDT on March 30, 2014.
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# 49973) at 2349 ET on March 29, 2014, pursuant to 10 CFR 50.72(b)(3)(v)(D).
This event constitutes a safety system functional failure for Unit 1.
C. CAUSE OF EVENT:
Troubleshooting found that the hydramotor hydraulic pump bearing failed resulting in a loss of hydraulic pressure. The 1VD19Y damper is designed to fail closed on a loss of hydraulic pressure to protect room components from freezing during winter months.
The corrective action completed was replacement of the 1VD19Y hydramotor.
D. SAFETY ANALYSIS:
The safety significance of this event was minimal. The HPCS system was unavailable and inoperable for a short period of time (unavailable for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> 25 minutes and inoperable for 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br /> and 55 minutes). During this period of time all other Emergency Core Cooling Systems were operable.
E. CORRECTIVE ACTIONS:
- The 1VD19Y hydramotor was replaced and tested satisfactorily.
F. PREVIOUS OCCURRENCES:
A search of LaSalle LERs over the last 10 years did not identify any LERs initiated as a result of a failed hydramotor.
In 2012 LaSalle performed a Common Cause Analysis (CCA) for switchgear room cooling failures that included hydramotor equipment issues. The CCA documented 6 hydramotor equipment issues from 2008 to 2012. There were 3 issues in 2008, two in 2010, and one in 2012. None of the six hydramotor equipment issues recorded in the CCA resulted in an LER and none had the same failure mode as the 1VD19Y.
Improved hydramotor performance has been seen at LaSalle by replacing the hydramotors on a six year preventative maintenance schedule with vendor (AREVA) refurbished hydramotors.
G. COMPONENT FAILURE DATA:
Automatic Switch Company (ASCO)/Model AH91 Hydramotor