ENS 51925

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v t e ENS Event
05:10 May 13, 2016
Title	Manual Reactor Scram Due After Loss of an Essential Motor Control Center
Event Description	At approximately 0110 hours0.00127 days <br />0.0306 hours <br />1.818783e-4 weeks <br />4.1855e-5 months <br /> [EDT] on May 13, 2016, Susquehanna Steam Electric Station Unit Two reactor was manually scrammed by plant operators due to a sustained loss of AC power to essential plant loads. Power to MCC 2B246 was lost at 2355 on May 12, 2016, resulting in a loss of Drywell cooling. Drywell pressure increased to 1.3 psig when operators placed the mode switch to the shutdown position to manually SCRAM the reactor. All rods inserted as expected. Reactor water level lowered to -27 inches and was immediately restored by normal feedwater level control. Level 3 (+13 inch) PCIS isolations occurred, along with an initiation of the RCIC system (-30 inches). Once adequate level was verified, RCIC was overridden. Pressure was controlled with turbine bypass valves, and subsequently main steam line drains. All safety systems functioned as expected. The power loss also tripped Reactor Building HVAC, causing a loss of secondary containment differential pressure resulting in a loss of safety function. Due to the loss of drywell cooling, high drywell pressure actuations and a second reactor SCRAM signal, this signal was automatic, occurred at 0314 hours0.00363 days <br />0.0872 hours <br />5.191799e-4 weeks <br />1.19477e-4 months <br />. HPCI [which automatically initiated on high drywell pressure] was subsequently overridden and declared inoperable, resulting in a loss of safety function. [HPCI did not inject into the vessel]. The reactor is currently stable in Mode 3. Initial reports from the field indicate a phase to phase fault on the MCC 2B246 bus bars. The licensee has notified the NRC Resident Inspector and will be issuing a press release.

ENS 51925 +/-
Where
Susquehanna Pennsylvania (NRC Region 1)
Reporting

10 CFR 50.72(b)(2)(iv)(B), RPS Actuation 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge
Time - Person (Reporting Time:+-0.17 h-0.00708 days <br />-0.00101 weeks <br />-2.32866e-4 months <br />)
Opened:	Carl Young 05:00 May 13, 2016
NRC Officer:	Howie Crouch
Last Updated:	May 13, 2016
51925 - NRC Website
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)(2)(iv)(A), System Actuation - ECCS Discharge, 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material
WEEKMONTHYEAR2103-11-21T03:40:00 [Table view]
[ENS list for Susquehanna]

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