ML060510001
| ML060510001 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 02/20/2006 |
| From: | Burgess B L, West K S Division Reactor Projects III |
| To: | |
| References | |
| PNO-III-06-005 | |
| Download: ML060510001 (2) | |
Text
February 20, 2006PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE -- PNO-III-06-005This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or publicinterest significance. The information is as initially received without verification or evaluation, and is basically all that is known by the Region III staff on this date.FacilityLaSalle Unit 1Exelon Generation Co.Marseilles, ILDocket: 50-373 License: NPF-11Licensee Emergency Classification Notification of Unusual Event Alert X Site Area Emergency General Emergency Not Applicable
SUBJECT:
INDICATION FAILURE FOR 3 CONTROL RODS FOLLOWING REACTOR TRIPDESCRIPTION:At 12:23 a.m. CST on February 20, 2006, the Unit 2 reactor shut down automatically from 6percent power, and reactor instrumentation showed that three control rods failed to insert fully into the reactor core. There are 185 control rods which control reactor power level and which are fully inserted to shut down the reactor.Because of the uncertainty of the position of the three control rods, the licensee declared a SiteArea Emergency under its emergency plan at 12:28 a.m. A site area emergency is the second highest classification under the NRC emergency response system. The licensee notifiedappropriate state, local, and federal agencies according to its emergency plan.Subsequently, the instrumentation showed that the reactor was shut down (i.e., subcritical)although the position indication for one control rod remained indeterminate. There was noindication of a release of radioactivity to the environment, and reactor conditions were stable.At the time of the automatic reactor trip, the plant was being shut down for a refueling outage.Following investigation of the control rod indication problems, the utility terminated the Site AreaEmergency classification at 4:27 a.m.The NRC entered the monitoring mode and staffed the Region III (Chicago) incident responsecenter and the Headquarters Operations Center. The resident inspectors responded to theplant to monitor the licensee's response to the event.Preliminary information showed that the reactor trip was caused by a malfunction of the plant'sturbine control system.CONTACTS:Bruce BurgessSteven West630/829-9629630/829-9601 PNO-III-06-005-2-The licensee is investigating the cause of the turbine control system malfunction and the controlrod indication anomalies.Region III will initiate a special inspection to review the circumstances surrounding the event.The State of Illinois has been notified of the event.The licensee and the NRC will issue a news release on this event. Region III is prepared torespond to news media inquiries. The information in this preliminary notification has beenreviewed with licensee management.The licensee notified Headquarters Operation of this event at 1:14 a.m. CST on February 20,2006. This information is current as of 7 a.m. CST on February 20, 2006.