ENS 41667
ENS Event | |
|---|---|
19:07 Mar 6, 2005 | |
| Title | Invalid Safety System Actuation During an Outage |
| Event Description | This 60-day ENS report is being made per 10CFR 50.73(a)(2)(iv)(A) to report an invalid automatic actuation of systems listed in paragraph (a)(2)(iv)(B), namely ECCS, emergency diesel generator (EDG), and emergency service water (ESW).
On March 6, 2005 at 15:07 hours a Unit 2 Division 3 LOCA signal was inadvertently initiated during replacement of a power supply on ECCS. Continuity on the 24 VDC power distribution signal common was lost while lifting leads on the power supply. One terminal on the power supply was part of a daisy chain circuit connection. This resulted in an unplanned actuation of the high drywell pressure relays. Two 24 VDC power supplies are connected in parallel to supply power to Division 3 ECCS trip units and relays. It was planned to replace one of these power supplies while the power distribution network remained energized by the redundant power supply. However, the continuity of the power distribution network relied on the connection of two leads on one terminal on the out-of-service power supply. When the two leads were separated several relays lost their normal connection to the signal common. Reverse currents caused the false actuation of the Division 3 high drywell pressure relays. D23 EDG automatically started and ran unloaded. The C ESW pump automatically started due to the EDG start. The 2A Core Spray (CS) loop received a partial actuation in that the Division 3 signal was initiated but the Division 1 signal was not initiated. 2C CS pump started as designed and 2A CS pump did not start which was expected. The 2A CS loop automatic valve alignment is initiated by the Division 1 signal; therefore, no automatic 2A CS loop valve alignment occurred. All systems functioned as designed during the event. The cause of the event was that the work package planner for the power supply replacement failed to recognize the impact on plant systems and as a result applied less than adequate technical rigor. The maintenance planning procedure will be revised to ensure the appropriate level of technical rigor is applied for work packages that lift or manipulate a signal common lead. This event Is reportable per 10CFR50.73(a)(2)(iv)(A) since 2C Core Spray pump, D23 EDG and C ESW pump automatically actuated on an invalid signal. The NRC Resident Inspector has been notified. |
| Where | |
|---|---|
Limerick  Pennsylvania (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+1437.62 h59.901 days <br />8.557 weeks <br />1.969 months <br />) | |
| Opened: | Mark Crim 15:44 May 5, 2005 |
| NRC Officer: | Pete Snyder |
| Last Updated: | May 5, 2005 |
| 41667 - NRC Website
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WEEKMONTHYEARENS 564642023-02-16T12:05:00016 February 2023 12:05:00
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