*Updates are underlined
All 6 units of Fukushima Daiichi Nuclear Power Station have been shut down.
Unit 1 (Shut down)
- Explosive sound and white smoke were confirmed after the big quake
occurred at 3:36 pm on March 12th. It was assumed to be hydrogen
explosion.
- At approximately 2:30 am on March 23rd, seawater injection to the nuclear
reactor through the feed water system was initiated.
- From 3:37 pm on March 25th, we started injecting freshwater and are now
injecting fresh water by a motor driven pump powered by the off-site
transmission line.
- As it is suspected that hydrogen gas is accumulated inside reactor
containment vessel, we commenced the valve opening operation concerning
injection of nitrogen gas into the reactor container vessel at 10:30 pm
April 6th and commenced injection at 1:31am April 7th.
Unit 2(Shut down)
- At approximately 6:00 am on March 15th, an abnormal noise began emanating
from nearby Pressure Suppression Chamber and the pressure within the
chamber decreased.
- From 10:10 am on March 26th, we started injecting freshwater to the
reactor and are now injecting fresh water by a motor driven pump powered
by the off-site transmission line.
Unit 3(Shut down)
- Explosive sound and white smoke were confirmed at approximately 11:01am
on March 14th. It was assumed to be hydrogen explosion.
- From 6:02 pm on March 25th, we started injecting fresh water to the
reactor and are now injecting fresh water by a motor driven pump powered
by the off-site transmission line.
Unit 4 (outage due to regular inspection)
- At approximately 6:00 am on March 15th, we confirmed the explosive sound
and the sustained damage around the 5th floor rooftop area of the Nuclear
Reactor Building.
- At this moment, we do not consider any reactor coolant leakage inside the
reactor happened.
Unit 5 (outage due to regular inspection)
- Sufficient level of reactor coolant to ensure safety is maintained.
- At 5:00 am on March 19th, we started the Residual Heat Removal System
Pump (C) in order to cool the spent fuel pool.
- At 2:30 pm on March 20th, the reactor achieved reactor cold shutdown.
- At this moment, we do not consider any reactor coolant leakage inside the
reactor happened.
Unit 6 (outage due to regular inspection)
- Sufficient level of reactor coolant to ensure safety is maintained.
- At 10:14 pm on March 19th, we started the Residual Heat Removal System
Pump (B) of Unit 6 in order to cool the spent fuel pool.
- At 7:27 pm on March 20th, the reactor achieved reactor cold shutdown.
- At this moment, we do not consider any reactor coolant leakage inside the
reactor happened.
Operation for cooling the spent fuel pools
- From 6:15 pm on April 25th to 12:26 am on April 26th, water was sprayed
to the spent fuel pool of Unit 4 by the concrete pumping vehicle.
- From 12:25 pm to 2:02 pm on April 26th, fresh water was injected into
Unit 3 by the temporary motor driven pump.
- We will conduct further water spray depending on the conditions of spent
fuel pools, if needed.
Others
- From 2:44 pm to 5:38 pm on April 25, temporary power panel (6.9kV) became
temporarily offline due to the reinforcement work of power supply line
(connecting high voltage power panels in Unit 1/2 and Unit 5/6)
- From 1:30pm on April 26th, we started spraying dust inhibitor in order to
prevent diffusion of radioactive materials.
- From 11:35 am to 1:24 pm on April 26th, we confirmed plant conditions
using the unmanned remote-controlled robot. We confirmed the plant
conditions inside of Unit 1's reactor building measurement of radiation
dose is little difference exists from last survey. We also confirmed
there is no significant water leakage on Primary Containment Vessel (PCV).
- At 10:08 am on April 19th we started transferring high level radioactive
wastewater to the Centralized Radiation Waste Treatment Facility.
- We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the power station.
