This is misleading because it claims all safety systems responded the way they were supposed to. However the high pressure injection system was inoperable (although not called upon). This is how accident get started.
Power Reactor Event Number: 51925
Region: 1 State: PA
Unit: [ ]  [ ]
RX Type:  GE-4, GE-4
NRC Notified By: CARL YOUNG
HQ OPS Officer: HOWIE CROUCH Notification Date: 05/13/2016
Notification Time: 05:00 [ET]
Event Date: 05/13/2016
Event Time: 01:10 [EDT]
Last Update Date: 05/13/2016
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL
50.72(b)(3)(v)(C) - POT UNCNTRL RAD REL
50.72(b)(2)(iv)(A) - ECCS INJECTION
ART BURRITT (R1DO)
SCOTT MORRIS (NRR)
Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
2 M/R Y 100 Power Operation 0 Hot Shutdown
MANUAL REACTOR SCRAM DUE AFTER LOSS OF AN ESSENTIAL MOTOR CONTROL CENTER
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.
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].
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.