ENS 45962

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v t e ENS Event
01:56 Apr 3, 2010
Title	Overvoltage Condition Causes Reactor Protective System Actuation
Event Description	On Friday April 2, 2010, Unit 1 refueling outage activities were in progress and the 1A RPS/UPS Static Inverter was being removed from service. At 2156 hours0.025 days <br />0.599 hours <br />0.00356 weeks <br />8.20358e-4 months <br />, the inverter static transfer switch was placed in 'Bypass' which transferred the load from the inverter to the secondary alternate source. The manual bypass switch was then placed in 'Bypass' which was followed by the RPS/UPS series breakers tripping on an overvoltage condition. The actuation caused a loss of power to the IA RPS/UPS power distribution panel loads which provides power to the Division 1A and IIA RPS relays and Division IA and IIA NS4 relays. This caused primary containment isolation valves (PCIVs) to automatically close on more than one system. The IB and IIB channels were unaffected. Troubleshooting determined that the secondary, alternate source voltage was 132 VAC which exceeded the overvoltage setpoint of 126 VAC. During outages, the 13kV bus voltages are higher than on-line voltages due to low operating equipment loading on the buses. The secondary alternate source to the inverter is not regulated which can result in greater than normal voltage to the RPS/UPS loads. 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 10CFR 50.73(a)(2)(iv)(A) and 10CFR 50.73(a)(1) to report invalid automatic actuation 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), and suppression pool cleanup. The licensee notified the NRC Resident Inspector.

ENS 45962 +/-
Where
Limerick Pennsylvania (NRC Region 1)
Reporting

10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation
Time - Person (Reporting Time:+1332.95 h55.54 days <br />7.934 weeks <br />1.826 months <br />)
Opened:	Dan Williamson 14:53 May 28, 2010
NRC Officer:	Mark Abramovitz
Last Updated:	May 28, 2010
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v • d • e

v t e Emergency Notification System
Limerick with 10 CFR 50.73(a)(1), Submit an LER
WEEKMONTHYEAR2023-02-16T12:05:00 [Table view]
[ENS list for Limerick]

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