ENS 48370

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v t e ENS Event
01:25 Aug 6, 2012
Title	Rps Sub-Component Failure Caused Half Scram with Group 2 Pciv Actuation
Event Description	On August 5, 2012, at 21:25 EDT, Unit 1 received a Reactor Auto SCRAM System 'A' Trip signal in the main control room. The annunciator was initially reset by operators, but the operating crew noted that some white SCRAM lights and some Group 2 PCIV indication lights were flickering in the control room. This anomaly coupled with the ability to reset the annunciated condition immediately indicated an issue with fluctuating voltage on the power supply for RPS [Reactor Protection System] 'A'. Approximately 30 seconds after the annunciator was reset, the 'A' RPS bus tripped, causing a half SCRAM in conjunction with the automatic actuation of the Standby Gas Treatment system (SGT) and isolation of PCIVs in multiple systems, both of which are normal responses to this loss of the 'A' RPS bus. The crew entered the appropriate abnormal operating procedures and confirmed the actuations automatically occurred as required given the loss of the RPS bus. They investigated the 'A' RPS Motor/Generator (M/G) set, placed the 'A' RPS bus on its alternate supply, reset the SGT and PCIV actuation logic, and returned the PCIVs to their normal position. Upon investigation, the 'A' RPS M/G set was found running, but the Over Voltage Relay in the power monitoring cabinet was chattering. The field investigation team determined that the RPS trip was caused by the failure of its voltage regulator which was then replaced. The 'A' RPS M/G set was consequently returned to service as the primary RPS power source on August 6, 2012. Maintenance personnel subsequently determined that a voltage regulator subcomponent was defective. Because the malfunctioning subcomponent caused the loss of RPS 'A' as the initiating event rather than a valid SGT or PCIV actuation signal, the resulting actuation of SGT and the isolation of multiple PCIVs are considered invalid actuations. Based on that information, 10CFR50.73(a){2)(iv) allows this event to be reported via a telephone notification within 60 days instead of submitting a written LER. The licensee has notified the NRC Resident Inspector.

ENS 48370 +/-
Where
Hatch Georgia (NRC Region 2)
Reporting

10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation
Time - Person (Reporting Time:+1403.02 h58.459 days <br />8.351 weeks <br />1.922 months <br />)
Opened:	Kenny Hunter 12:26 Oct 3, 2012
NRC Officer:	John Knoke
Last Updated:	Oct 3, 2012
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v • d • e

v t e Emergency Notification System
Hatch with 10 CFR 50.73(a)(1), Submit an LER
WEEKMONTHYEAR2023-11-02T01:11:00 [Table view]
[ENS list for Hatch]

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