ENS 48575
ENS Event | |
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23:41 Oct 13, 2012 | |
Title | 60-Day Optional Telephonic Notification of Invalid Multiple System Actuations |
Event Description | On Saturday, October 13, 2012, Unit 1 was operating at 100% power. At 1841 [EDT], the 1A RPS/UPS inverter tripped and the automatic transfer of the RPS and UPS 120 VAC distribution panel (1A-Y160) loads to the primary alternate AC power source was delayed. The delay in automatic load transfer caused the RPS series breakers to trip on undervoltage. The failure caused a loss of power to Division IA and IIA RPS relays and Division IA and IIA NS4 relays. This caused primary containment isolation valves (PClVs) to automatically close on more than one system. The IB and IIB channels were unaffected.
The most probable cause for the delayed load transfer was a failed logic power supply with a momentary loss of synchronization. Troubleshooting continues [in order] to confirm the specific cause of the component failure. The distribution panel loads are currently supplied by an installed alternate AC power source. The portion of the primary containment isolation system that received an actuation signal functioned successfully. All of the affected open isolation valves automatically closed. The isolation was a partial actuation. This 60-day ENS report is being made per 10CFR50.73(a)(2)(iv)(A) and 10CFR50.73(a)(1) to report invalid automatic actuations of systems listed in paragraph (a)(2)(iv)(B). The listed system that actuated was general containment isolation signals affecting containment isolation valves in more than one system. Primary containment isolation valves (PCIVs) closed on drywell chilled water (DWCW), reactor enclosure cooling water (RECW), primary containment instrument gas (PCIG), Unit 1 containment leak detector, and Unit 2 containment leak detector. The licensee notified the NRC Resident Inspector. |
Where | |
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Limerick ![]() Pennsylvania (NRC Region 1) | |
Reporting | |
10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
Time - Person (Reporting Time:+1388.98 h57.874 days <br />8.268 weeks <br />1.903 months <br />) | |
Opened: | John Harkins 21:40 Dec 10, 2012 |
NRC Officer: | Vince Klco |
Last Updated: | Dec 10, 2012 |
48575 - NRC Website
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Unit 1 | |
---|---|
Reactor critical | Critical |
Scram | No |
Before | Power Operation (100 %) |
After | Power Operation (100 %) |
WEEKMONTHYEARENS 564642023-02-16T12:05:00016 February 2023 12:05:00
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