*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 12. It was assumed to be hydrogen explosion.
- At 3:37 pm on March 25, 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.
The current water injection volume is approx 4.4m3/h from the reactor
feed water system.
- We commenced injection of nitrogen gas into Primary Containment Vessel at
1:31 am on April 7.
- At 10:55 am of December 7, in order to increase the reliability of
nitrogen injection, we started installing works of flow rate indicators
and pressure indicators to the unit 1 nitrogen injection line. At 11:26
am this work was completed. During this time we stopped injecting
nitrogen but there was no impact to the Reactor Pressure Vessel.
- At 11:22 am on August 10, we started cyclic cooling for the water in the
spent fuel pool by an alternative cooling equipment of the Fuel Pool
Cooling and Filtering System.
- On October 28, we completed installation of the cover for the Reactor
Building in order to contain dispersion of radioactive substances.
- At 4:04 pm on November 30, we started operation to inject nitrogen into
the reactor pressure vessel.
- On December 7, in order to secure enough time before the hydrogen reached
the explosion limit in case the nitrogen injection facility stops, we
increased the injection amount of Nitrogen to the Reactor Pressure Vessel.
At 1:15 pm on the same day, we increased nitrogen injection from 10Nm3/h
to 15Nm3/h.
Unit 2 (Shut down)
- At approximately 6:00 am on March 15, an abnormal noise began emanating
from nearby Pressure Suppression Chamber and the pressure within the
chamber decreased.
- At 10:10 am on March 26, 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.
- At 2:59 pm on September 14, we started injecting water to the reactor
through core spray system water injection piping arrangement in addition
to the water injection through reactor feed water system piping
arrangement.
Water is currently injected at approx. 3m3/h through reactor feed water
system piping arrangement, and at approx. 4.1m3/h through core spray
system water injection piping arrangement.
- At 5:21 pm on May 31, we started cyclic cooling for the water in the
spent fuel pool by an alternative cooling equipment of the Fuel Pool
Cooling and Filtering System.
- At 8:06 pm on June 28, we started injecting nitrogen gas into the Primary
Containment Vessel.
- At 2:16 pm on December 7, we had enough time before the hydrogen reached
the explosion limit, and we decreased nitrogen injection from 26 Nm3/h to
20 Nm3/h.
- From 6:00 pm on October 28, we put the gas management system of the
reactor containment vessel in operation.
- At 11:04 am on November 6, we started operation of radioactive material
decontamination instrument of spent fuel pool. On December 5, the
facilities finished its operation.
- At 10:46 am on December 1, we started the nitrogen injection to the
Reactor Pressure Vessel.
- On December 7, in order to secure enough time before the hydrogen reached
the explosion limit in case the nitrogen injection facility stops, we
increased the injection amount of Nitrogen to the Reactor Pressure Vessel.
At 2:16 pm on the same day, we increased nitrogen injection from 10Nm3/h
to 13Nm3/h.
- On December 6 we conducted air sampling at the gas controlling system of
the Primary Containment Vessel of unit 2. As a result we confirmed that
at the exit of the gas controlling system of the Primary Containment
Vessel, the level of xe-135 detected was below detection limit (1.1 x
10-1Bq/cm3) and below the recriticality standard 1Bq/cc.
- At 4:17 am on December. 7, on the alternative Spent Fuel Pool cooling
system of Unit 2, the alarm indicating that the difference of flow rates
between at the entering and at the exit of the primary pump is big went
off, and the system stopped automatically. At 4:41 on the same day, after
field investigation, no defect such as leakage was confirmed. Currently
the cause is under investigation,. At 4:00 am, the temperature of Spent
Fuel Pool was 18.4 degree C, the assumed increase of temperature is 0.3
degree C/h, from the viewpoint of Spent Fuel Pool temperature, there is
still enough allowance, so that there is no problem.
Unit 3 (Shut down)
- Explosive sound and white smoke were confirmed at approximately 11:01 am
on March 14. It was assumed to be hydrogen explosion.
- At 6:02 pm on March 25, 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.
- At 2:58 pm on September 1, we started water injection by core spray
system in addition to water injection by the reactor feed water system
piping arrangement.
Water is currently injected at approx. 2.1 m3/h through reactor feed
water system piping arrangement, and at approx. 6.0 m3/h through core
spray system water injection piping arrangement.
- At 7:47 pm on June 30, we started cyclic cooling for the water in the
spent fuel pool by an alternative cooling equipment of the Fuel Pool
Cooling and Filtering System.
- At 8:01 pm on July 14, injection of nitrogen gas into the Primary
Containment Vessel started.
- At 4:26 pm on November 30, we started operation to inject nitrogen into
the reactor pressure vessel.
- On December 7, in order to secure enough time before the hydrogen reached
the explosion limit in case the nitrogen injection facility stops, we
increased the injection amount of Nitrogen to the Reactor Pressure Vessel.
At 10:52 am on the same day, we increased nitrogen injection from 10Nm3/h
to 15Nm3/h.
Unit 4 (Outage due to regular inspection)
- At around 6 am on March 15, we confirmed the explosive sound and the
sustained damage around the 5th floor rooftop area of Reactor Building.
- At 12:44 pm on July 31, we started cyclic cooling for the water in the
spent fuel pool by an alternative cooling equipment of the Fuel Pool
Cooling and Filtering System.
- Regarding spent fuel pool for unit 4, from August 20 to November 8, we
had decreased salinity by using the desalting facility. In order to
decrease more salinity, we installed Ion exchange equipment and started
the equipment at 10:58 am on November 29.
- At this moment, we don't think there is any reactor coolant leakage
inside the primary containment vessel.
Unit 5 (Outage due to regular inspection)
- Sufficient level of reactor coolant to ensure safety is maintained.
- At 5:00 am on March 19, we started the Residual Heat Removal System Pump
in order to cool the spent fuel pool.
- At 2:30 pm on March 20, the reactor achieved cold shutdown.
- At 2:45 pm on July 15, we started the operation of the original Residual
Heat Removal System (System B) by its original seawater pump.
- At this moment, we don't think there is any reactor coolant leakage
inside the primary containment vessel.
Unit 6 (Outage due to regular inspection)
- Sufficient level of reactor coolant to ensure safety is maintained.
- At 10:14 pm on March 19, we started the Residual Heat Removal System Pump
of Unit 6 to cool down Spent Fuel Pool.
- At 7:27 pm on March 20, the reactor achieved cold shutdown.
- At 2:33 pm on September 15, we started separately cooling the reactor
through the Residual Heat Removal System and the spent fuel pool through
Equipment Cooling Water System and Fuel Pool Cooling System.
- At this moment, we do not think there is any reactor coolant leakage
inside PCV.
Others
- At around 10 am on June 13, we started the operation of the circulating
seawater purification facility installed at the screen area of Unit 2
and 3.
- At 8 pm on June 17, we started operation of Water Treatment Facility
against the accumulated water. At 6:00 pm on July 2, we started the
circulating injection cooling to inject the water, which was treated by
the accumulated water treatment system, to the reactors through the
buffer tank.
- At 7:41 pm on August 19, we started treatment of accumulated water by
parallel operation of one line from the cesium adsorption instrument to
the decontamination instrument and the other treatment line of the cesium
adsorption instrument No.2.
- At 2:06 pm on October 7, we started to spray purified accumulated water
brought from Unit 5 and 6 continually in order to prevent dust scattering
and potential fire outbreaks from the cut down trees.
- On October 28, we started installation of the water proof wall at the sea
side, in front of the existing shore protection, Units 1-4, in order to
contain marine pollution by underground water.
- At 6:03 pm on November 30, we started transfer of the accumulated water
from the basement of Unit 2 turbine building to Centralized Radiation
Waste Treatment Facility High Temperature Incinerator Building.
- On December 4, workers of partner companies found that there was puddle
water inside the barrier around the evaporative condensation apparatus.
Afterwards we stopped the apparatus, and workers made visual inspection
of the apparatus and confirmed the leakage have stopped. After conducting
investigation, we found a crack in the concrete barrier, and water
leaking from this crack to the gutter (surface dose rate of leaked water:
beta ray 110 mSv/h, gamma ray 1.8 mSv/h). We also found water leaking
from between the barrier and the base concrete. We are considering
measures to stop this leakage to outside of the barrier. We confirmed
that the leakage had stopped by piling up sandbags between the barrier
and base concrete, and in the gutter. We sent the leaked water remaining
in the barrier to the waste water RO supply tank with a water pump
(approx. 15 m3).
Since the gutter led to the generally used channel of the power plant, we
have taken sea water from the channel around the water desalinations
(evaporative concentration apparatus) and the south drain (drain for the
generally used channel) and have conducted a nuclide analysis, and we
judged that the leaked water has been discharged into the sea from the
exit of generally used channel. It was estimated that approx. 150 liter
out of leakage water has flew in the channel, and assumed that it has
been discharged into the sea through the generally used channel. As a
result, the whole amount of radioactivity was approx. 2.6 x 1010 Bq
(temporary). As the impact of the discharge water into the sea, in the
assumption that we eat fish and seaweeds around the discharge channel
every day, the effective zone for an adult is approx. 0.0037 mSv / year,
that equals to approx. 1/600 of annual dose from nature for general
public (2.4 mSv), so that we evaluate there is almost no impact
- We plan to establish the system injecting water into the reactor in Unit
1 to 3 using the condensate storage tank of Unit 3. In preparation of
such establishment, the stored water in the tank was transferred to the
basement of turbine building of Unit 3 from 10:22 am on November 21 to
9:45 am on November 24. As the calibration of water level gauge is
required if all the water is transferred, approx. 200 ton was left in the
tank. During the measurement of salt concentration in the left water, it
turned out that concentration was high. In order to secure the space for
additional water injection to decrease such concentration, at 10:00 am on
December 6, the left water was transferred from the tank to the basement
of the turbine building of Unit 3.
At 8:54 on December 7, we stopped transferring, and at approx. 9:19 am on
the same day, we started filling water in the tank, but afterwards, we
confirmed water leakage at the joint section of horse connecting to the
tank (approx. 5 liters), at approx. 9:52 am, we stopped filling water and
confirmed the leakage has stopped. We are planning to repair. The leakage
water was disposed through removal system and desalination.