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| Entered date | Event description | |
|---|---|---|
| ENS 46220 | 1 September 2010 13:42:00 | On July 26, 2010, at 1819 hours (CDT), with Unit 1 in Mode 1 (Run), the Division 1 Diesel Generator Cooling Water Pump (DGCWP) restarted after being secured. The DGCWP provides the Emergency Service Water to the 1A Residual Heat Removal (RHR) pump room area cooler and the Reactor Core Isolation Cooling (RCIC) water pump/Low Pressure Core Spray (LPCS) pump room area cooler. The apparent cause of the restart was the momentary interruption of the DGCWP run logic. The Division 1 DGCWP was in operation to support cooling of the Unit 1 RCIC/LPCS pump room area (run logic satisfied). When the Operator placed the Division 1 DGCWP control switch to the normal-after-stop position, the DGCWP feed breaker opened. The Operator reset the DGCWP feed breaker trip by returning the control switch to the normal-after-stop position and, because the run logic for the DGCWP was still satisfied (due to elevated room temperatures), the DGCWP restarted. This invalid start signal from the Division 1 DGCWP breaker being reset resulted in the automatic actuation of the Division 1 DGCWP. The Division 1 DGCWP responded satisfactorily. This report is being made in accordance with 10CFR50.73(a)(1), which states that in the case of an invalid actuation reported under 10CFR73(a)(2)(iv)(A), other than an actuation of the Reactor Protection System (RPS) when the reactor is critical, the licensee may provide a telephone notification to the NRC Operations Center with 60 days after discovery of the event instead of submitting a written LER. The licensee has notified the NRC Resident Inspector. |
| ENS 45868 | 22 April 2010 15:57:00 | A non-licensed employee supervisor had a confirmed positive for alcohol during a random fitness-for-duty test. The employee's access to the plant has been terminated. Contact the Headquarters Operations officer for additional details. The licensee informed the NRC Resident Inspector. |
| ENS 45087 | 21 May 2009 20:46:00 | At 1635 CDT on May 21, 2009, LaSalle Unit 1 automatically scrammed due to a main power transformer fault. The transformer fault appears to have been caused by a failed bushing or lightning arrestor. The main power transformers deluged and other than the initial flash, there was no fire. Two safety relief valves actuated in the relief mode on the turbine trip. There were spurious non-valid isolation signals due to electrical power perturbations that were received on the reactor building ventilation system and reactor water cleanup. The plant is stable with reactor pressure control to the main condenser via the turbine bypass valves. The plant (will) remain in hot shutdown pending transformer inspection and repair. All control rods fully inserted following the scram signal. Water level is being controlled via the motor driven reactor feedwater pump. Current reactor pressure is 927 psig and current reactor temperature is 532 degrees F. The plant is in a normal post-trip electrical lineup. No diesel generators started as a result of this event. The licensee notified the NRC Resident Inspector. |
| ENS 42737 | 27 July 2006 21:00:00 | This telephone notification is provided in accordance with 10 CFR 50.73(a)(1) to report an invalid actuation reportable under 10 CFR 50.73(a)(2)(iv)(A). On June 4, 2006, at 0419 (CST), with Unit 1 in Mode 1 'Run' at approximately 100% power, the 1B Reactor Protection System (RPS) bus unexpectedly de-energized. As a result, an RPS Bus B half-scram and Division 2 Primary Containment Isolation System (PCIS) isolations were received. All affected containment isolation valves closed as designed. RPS Bus B was transferred to its alternate feed, and restoration activities were begun. A walkdown found that the 1B RPS MG set output breaker had opened. Troubleshooting identified that the cause was a failure of the 1B RPS MG set voltage regulator. The voltage regulator was replaced and successfully tested, and the 1B RPS MG set was returned to service. Laboratory testing of the failed voltage regulator found that the stability potentiometer had failed, with excessive vibration identified as the apparent cause. Although the vibration levels at the MG set are considered to be normal, the voltage regulator is mounted in a control cabinet that sits directly on the generator end of the MG set. The normal vertical vibration on the 1B MG set was measured at greater than 2g, which could be sufficient over time to degrade the voltage regulator potentiometers. A design change has been initiated for both Units to isolate the voltage regulators from the RPS MG set vibrations. This event is reportable under 10 CFR 50.73(a)(2)(iv)(A) as an invalid actuation of containment isolation valves in more than one system. The licensee notified the NRC Resident Inspector. |
| ENS 40993 | 27 August 2004 12:20:00 | A contract supervisor tested positive for alcohol during a for-cause test. The individual's access to the plant has been terminated. Contact the Headquarters Operations Officer for additional details. The licensee informed the NRC Resident Inspector. |