ENS 46897
ENS Event | |
|---|---|
04:28 Apr 1, 2011 | |
| Title | 60-Day Telephonic Notification of Invalid Specified System Actuation |
| Event Description | This event is reportable under 10 CFR 50.73(a)(2)(iv)(A) as an automatic actuation of general containment isolation signals affecting containment isolation valves in more than one system. This 60-day telephone notification is being made in accordance with 10 CFR 50.73(a)(1) for invalid actuations reported under 10 CFR 50.73(a)(2)(iv)(A). This actuation was invalid since it was caused by a loss of power to the Reactor Protection System (RPS) power system bus and not by any actual plant condition warranting containment isolation. The RPS power system provides 120 VAC power to logic and system components including the RPS and the containment isolation system.
On March 31, 2011, at 2128 hours0.0246 days <br />0.591 hours <br />0.00352 weeks <br />8.09704e-4 months <br /> [PDT], normal power was lost to RPS Bus 'A' resulting in a half scram and actuation of the Groups 2, 5, 6 and 7 primary containment outboard isolation valves. The immediate investigation found that the associated RPS motor generator (MG) set was running with normal 120 VAC output and that the two electrical protective assemblies between the MG set and RPS Bus 'A' were closed with no abnormal indications. A visual inspection of the RPS power panel revealed a cleared fuse for the normal feed. The RPS Bus 'A' was subsequently transferred to the alternate supply at 2135 hours0.0247 days <br />0.593 hours <br />0.00353 weeks <br />8.123675e-4 months <br />. The actuations and isolations were reset at 2154 hours0.0249 days <br />0.598 hours <br />0.00356 weeks <br />8.19597e-4 months <br />. The RPS power system is supplied from either of two sources: the normal power source from the MG set or the alternate source from a non-Class 1E distribution panel. Transfer between the normal and alternate power supplies is manually initiated by the control room operator. Troubleshooting activities determined that the cleared fuse was due to an internal short in the windings of the 120 VAC coil on the RPS Bus 'A' normal feed contactor. The cause of the internal short was attributed to a random isolated occurrence. The contactor was subsequently replaced and RPS Bus 'A' was returned to the normal power supply. There were no actual safety consequences associated with this event. The affected equipment responded as designed. Valves affected by the invalid signal fulfilled their isolation function by successfully closing. The NRC Resident Inspectors have been notified. |
| Where | |
|---|---|
Columbia Generating Station  Washington (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+1335.45 h55.644 days <br />7.949 weeks <br />1.829 months <br />) | |
| Opened: | Lisa Williams 19:55 May 26, 2011 |
| NRC Officer: | Howie Crouch |
| Last Updated: | May 26, 2011 |
| 46897 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 566252023-05-17T10:39:00017 May 2023 10:39:00
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