ENS 41560
ENS Event | |
|---|---|
13:56 Feb 7, 2005 | |
| Title | Invalid Specified System Actuation |
| Event Description | The following information was obtained from the licensee via facsimile (licensee text in quotes):
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 February 7, 2005, at 0756 [CST], with Unit 2 in Mode 3 'Hot Shutdown' in preparation for the 2005 refueling outage, the 2A Reactor Protection System (RPS) bus unexpectedly de-energized during performance of LOS-RP-W1, 'Manual Scram Instrumentation.' As a result, an RPS Bus A half scram and Division 1 Primary Containment Isolation System (PCIS) isolations were received, including the isolation of shutdown cooling. All affected containment isolation valves closed as designed. An inspection found that the 2A RPS MG set output breaker had opened. RPS Bus A was transferred to its alternate feed, and the associated containment isolations were reset. Shutdown cooling was restored at 0845 hours0.00978 days <br />0.235 hours <br />0.0014 weeks <br />3.215225e-4 months <br /> on February 7, 2005. Troubleshooting found that the 2A RPS MG set voltage regulator had failed. The voltage regulator was replaced and successfully tested, and the 2A RPS MG set was returned to service. Laboratory testing of the failed voltage regulator circuit board found that a solder joint had failed on load-dropping resistor R8, which caused the excitation output voltage to decrease sharply. This resulted in a trip of the 2A RPS MG set output breaker on low voltage. The apparent cause of the failed solder joint was a manufacturing defect. Corrective actions include visual inspections of RPS MG set voltage regulatory circuit boards in the field and in the storeroom, and the development of enhanced receipt inspection requirements. 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 has notified the NRC Resident Inspector. |
| Where | |
|---|---|
Lasalle  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+1344.38 h56.016 days <br />8.002 weeks <br />1.842 months <br />) | |
| Opened: | Harold Vinyard 13:19 Apr 4, 2005 |
| NRC Officer: | Howie Crouch |
| Last Updated: | Apr 4, 2005 |
| 41560 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Hot Shutdown (0 %) |
| After | Hot Shutdown (0 %) |
WEEKMONTHYEARENS 552402021-03-10T13:15:00010 March 2021 13:15:00
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