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 0:30 pm to 4:44 pm, April 23rd, we conducted water spray to Unit 4 by the concrete pumping vehicle. -From 0:25 pm, April 24th, we started water spray to Unit 4 by the concrete pumping vehicle. -We will conduct further water spray depending on the conditions of spent fuel pools, if needed. Others -At 10:08 am on April 19th we started transferring high level radioactive wastewater to the Centralized Radiation Waste Treatment Facility. -From 11:30am to 2:00pm, we opened and closed the double doors and conducted surveys of the situation of the inside of the nuclear reactor building of Unit 3 and measured a dose of radiation, etc. by a remote control robot. Also, from 4:00pm to 5:30pm, we did the same kind of work on Unit 1. From 1:42pm to 2:33pm on April 18th, we opened and closed the double doors, measured a dose of radiation and so on, and conducted surveys of the situation of the inside of the nuclear reactor building of Unit 2, by a remote control robot. -We will continue to take all measures to ensure the safety and to continue monitoring the surrounding environment around the power station.
