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Nuclear Event – Potential Uncontrolled Radiation Release: Susquehanna Nuclear Power Plant, Pennsylvania

2016/05/13

North America – USA | State of Pennsylvania, Berwick – Susquehanna Nuclear Power Plant
Location: 41°05’20.0″N 76°08’56.0″W
Present Operational Age: ~34 years
Event: RPS ACTUATION – CRITICAL; POT UNCNTRL RAD REL; MANUAL REACTOR SCRAM

Nuclear Event in USA on Friday, 13 May, 2016 at 01:10 [EDT]

MANUAL REACTOR SCRAM DUE AFTER LOSS OF AN ESSENTIAL MOTOR CONTROL CENTER

“At approximately 0110 hours [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 hours. 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.

Source: NRC  Event Number: 51925

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