ENS 45866

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v t e ENS Event
14:51 Apr 22, 2010
Title	Reactor Scram on Low Reactor Vessel Water Level During Feedwater Integrated Control System Testing
Event Description	At 10:51 on 4/22/10, Susquehanna Unit 1 experienced an automatic reactor SCRAM on reactor low level, +13", during the initial testing of the Feedwater Integrated Control System. Following the SCRAM, reactor water level dropped to approx. -30", and the Reactor Core Isolation Cooling system initiated and injected into the vessel. Level was recovered by the Feedwater System and the RCIC system. Division 2 Alternate Rod Insertion unexpectedly initiated during the level transient. Due to scheduled maintenance activities, the 11B Aux Bus did not transfer to the off site power supply post SCRAM. The 11B Aux bus was restored at 12:17. There were no ECCS initiations and no challenges to containment. This event is a Reactor Protection System (RPS) actuation when the reactor is critical, and is reportable as a four hour ENS Notification under 10 CFR 50.72(b)(2)(iv)(B). This event is also an unplanned actuation of a system used to mitigate the consequences of a significant event and is reportable as an eight hour ENS notification under 10CFR50.72(b)(3)(iv)(A). The scram was described as uncomplicated. All rods fully inserted and all systems functioned as required. The initiation of the alternative rod insertion should not occur unless level drops below -38" but the initiation did not result in any complications. The offsite supply breaker to Aux bus 11B was under maintenance when the scram occurred and so the loss of power was expected. This bus supplies some balance of plant loads which were lost (recirculation pump, condensate pump, and circulating water pump) but the loss of these components had no impact on the transient. The NRC Resident Inspector has been notified. The licensee will notify State authorities and also plans a press release.

ENS 45866 +/-
Where
Susquehanna Pennsylvania (NRC Region 1)
Reporting

10 CFR 50.72(b)(2)(iv)(B), RPS Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation
LER:	05000387/LER-2010-002
Time - Person (Reporting Time:+-1.52 h-0.0633 days <br />-0.00905 weeks <br />-0.00208 months <br />)
Opened:	Darvin Duttry 13:20 Apr 22, 2010
NRC Officer:	Bill Huffman
Last Updated:	Apr 22, 2010
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v • d • e

v t e Emergency Notification System
Susquehanna with 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation
WEEKMONTHYEAR2023-03-23T21:36:00 [Table view]
[ENS list for Susquehanna]

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