Insights on Accident Information and System Operations during Fukushima Events
Table 2
Records related to the operation of the IC and venting in Unit 1.
Date
Time
Event
March 11
2:46 pm
Earthquake, loss of offsite power, reactor trip, and IC autostart Fast cooldown (>55°C/hr) and operator closed MO-3A, 3B Control (open/close) of MO-3A (3 times before tsunami)
3:42 pm
Tsunami and SBO (operator unable to remember valve position)
6:18 pm
Temporary restoration of DC power MO-2A, 3A closed ⟶ open (confirmed with indication)
6:25 pm
MO-3A closed (unable to observe steam, fear of water depletion) No report to emergency response center
8:07 pm
RPV pressure (in the field) = 6.9 MPa
9:30 pm
Temporary restoration of DC power MO-3A open (steam generation confirmed)
11:50 pm
Battery connection to D/W pressure gauge (600 kPa)
March 12
2:30 am
D/W pressure = 840 kPa (= 528.3 kPa)
3:45 am
Repeated confirmation of vent operation
5:46 am
Started to pump fresh water through fire pumps to the RPV
8:27 am
Confirmed that evacuation is not complete
8:37 am
Informed Prefectural Government of venting at 9:00 am
