*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.
-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.
-From 7:35 pm, April 12th, we started transferring the high level
radioactive accumulated water in the trench of the turbine building to
the condenser by an underwater pump. At 5:04pm, April 13th, the scheduled
transfer was completed.
Unit 3(Shut down)
-Explosive sound and white smoke were confirmed at approximately 11:01am
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, March 19th, we started the Residual Heat Removal System Pump
(C) in order to cool the spent fuel pool.
-At 2:30 pm, March 20th, the reactor achieved reactor cold shutdown. At
around 5:24 pm on March 23rd, when we switched the temporary Residual
Heat Removal System Seawater Pump, it has stopped automatically. At
around 4:14 pm, March 24th we replaced the pump, and restarted cooling
of reactor at around 4:35 pm.
-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, 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, March 20th, the reactor achieved reactor cold shutdown.
-In relation to the two seawater side pumps of the Residual Heat Removal
System, we switched the power source from temporary to permanent at 3:38
pm and 3:42 pm, Mar 25 respectively.
-At this moment, we do not consider any reactor coolant leakage inside
the reactor happened.
Operation for cooling the spent fuel pools
-From 3:56 pm to 4:32 pm April 14th, water spray to the spent fuel pool
of Unit 3 was conducted with the concrete pumping vehicle.
-We will conduct further water spray depending on the conditions of spent
fuel pools, if needed.
Others
-We measured radioactive materials (iodine etc.) inside of the nuclear
power station area (outdoor) by monitoring car and confirmed that
radioactive materials level is getting higher than ordinary level. As
listed below, we have determined that specific incidents stipulated in
article 15, clause 1 of Act on Special Measures Concerning Nuclear
Emergency Preparedness (Abnormal increase in radiation dose measured
at site boundary) have occurred.
· Determined at 4:17 pm Mar 12th (Around Monitoring Post 4 )
· Determined at 8:56 am Mar 13th (Around Monitoring Post 4 )
· Determined at 2:15 pm Mar 13th (Around Monitoring Post 4 )
· Determined at 3:50 am Mar 14th (Around Monitoring Post 6 )
· Determined at 4:15 am Mar 14th (Around Monitoring Post 2 )
· Determined at 9:27 am Mar 14th (Around Monitoring Post 3 )
· Determined at 9:37 pm Mar 14th (Around main entrance )
· Determined at 6:51 am Mar 15th (Around main entrance )
· Determined at 8:11 am Mar 15th (Around main entrance )
· Determined at 4:17 pm Mar 15th (Around main entrance )
· Determined at 11:05 pm Mar 15th (Around main entrance )
· Determined at 8:58 am Mar 19th (Around MP5)
Hereafter, if the measured figure fluctuates and goes above and below
500 micro Sv/h, we deem that as the continuous same event and will not
regard that as a new specific incidents stipulated in article 15, clause
1 of the Act on Special Measures Concerning Nuclear Emergency
Preparedness (Abnormal increase in radiation dose measured at site
boundary) has occurred. In the interim, if we measure a manifestly
abnormal figure and it is evident that the event is not the continuous
same event, we will determine and notify.
-The national government has instructed evacuation for those local
residents within 20km radius of the periphery and evacuation to inside
for those residents from 20km to 30km radius of the periphery, because
it is possible that radioactive materials are discharged.
-From April 2nd, we began to transfer the radioactive water we collected
from the Central Environmental Facility to the Unit 4 turbine building.
On April 4th, water level of the pit in the trench of Unit 3 increased
by 15cm from previous day. Pathway of water flow is unknown. We can not
deny the possibility that water in the turbine building of Unit 4 flows
into the trench of Unit 3. So, we stopped transferring water to the Unit
4 turbine building to make assurance. Present water level of the pit in
the trench of Unit 3 is not changed from the time we stopped transferring,
and is being stable.
-From 7:03 pm, April 4th, we started to discharge to the sea approximately
ten thousand tons of the accumulated low level radioactive water in the
Central Radioactive Waste Disposal Facility. We are confirming the amount
of discharged water. From 9:00 pm on April 4, we conducted discharging a
total of 1,500 tons of the low level radioactive subsurface water stored
in the sub drain pits of Unit 5 and 6. The amount of discharged water was
approximately 1,323 tons.
-From 3:00 pm to 4:30 pm, April 5th, in order to prevent diffusion of
radioactive contaminated water out from the site port facility to
breakwater area which is south to the power station, we began repair of
breakwater by founding the large sandbag around it to replace damaged
steel water bar. We will continue the operation to prevent diffusion.
From 8:45 am to 10:45 am, April 11, in order to prevent water containing
radioactive material from spilling from a plant's port to the sea, we
conducted works to install 120m wide double silt fences around a
breakwater on the south of the station. From 8:45 am to 1:50 pm April
13th, we installed silt fences (double layered) in front of Unit 3 and
4 screens, and we also installed the same in front of Unit 1 and 2
screens, and around the north of south breakwater.
-We took a sample from Unit 4 spent fuel pool on 12th April, in order to
understand the fuel condition stored within the spent fuel pool. We are
planning to conduct a nuclide analysis.
-From 10:17 am to 0:25 pm April 14th an unmanned helicopter was flown over
Unit 1 to 4, in order to check the condition of the reactor buildings.
-We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the Power Station.
