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Press Release (Apr 15,2011)
Result of discharge of low level radioactive accumulated water in the Fukushima Daiichi Nuclear Power Station to the sea
 
There is currently great amount of radioactive wastewater in the turbine 
buildings of the Fukushima Daiichi Nuclear Power Station. Especially, the
wastewater in Unit 2 is extremely highly radioactive.

We think it is necessary to transfer the radioactive wastewater to the 
Central Radioactive Waste Disposal Facility in order to store it in a 
stable condition. However, ten thousand of low level radioactive 
wastewater is already stored and we have to discharge the existing low 
level radioactive wastewater to receive new liquids. 
 
In addition, as low radioactive subsurface water is piling up in 
sub-drain pits of Unit 5 and 6 and a part of subsurface water is running 
into buildings, we are concerned that important equipment to secure the 
safety of reactors will be submerged. 

Based on the Section 1 of the Article 64 of the Nuclear Reactor 
Regulation Law, we have decided to discharge to the sea approximately ten
thousand tons of the accumulated low level radioactive water and a total 
of 1,500 tons of the low level radioactive subsurface water stored in the
sub drain pits of Unit 5 and 6 as soon as we get ready.

We evaluate approximately 0.6 mSv of effective radioactive doses per year
for adults as the impact on the discharge of the low radioactive 
wastewater to the sea if they eat adjacent fish and seaweeds every day. 
The amount (0.6 mSv of effective radioactive doses per year) is one-forth
of annual radioactive dose to which the general public is exposed in 
nature.

                                        (We notified on April 4th, 2011.)

As to the low level radioactive wastewater stored at the Central 
Radioactive Waste Disposal Facility, we began discharging at 7:03PM, 
April 4th to the south of the water discharge channel and finished at 
5:40PM, April 10th. After that, at 9:55AM, April 11th, we confirmed that 
the wastewater in the building had been discharged sufficiently so that 
the preparation work to accept high level radioactive wastewater (such as
 water sealing) in the building could be done.
In relation to the low level radioactive subsurface water in sub-drain 
pits of Units 5 and 6, we began discharging from 9 PM, April 4th via the 
water discharge channel of Units 5 and 6 and finished by 6:52PM, April 
9th.

In terms of the discharge of low level radioactive accumulated water to 
the sea, as instructed by NISA, we have been conducting ocean monitoring 
in a steadfast manner. We have been increasing the number of monitoring 
points and the frequency to investigate and confirm the influence of the 
dispersion of radioactive substances and have been notifying the result.
The radioactive density monitored at the measurement points including 
near the power station did not indicate significant fluctuation in 
comparison with the trend one week before the discharge.

The amount of low level radioactive wastewater discharged to the sea 
this time was approx 9,070 tons from the Central Radioactive Waste 
Disposal Facility and approx 1,323 tons from the sub-drain pits of Units 
5 and 6 (Unit 5: approx 950 tons, Unit 6: approx 373 tons). The total 
radiation discharged was approx 1.5 x 1011 Bq.

We evaluate approximately 0.6 mSv of effective radioactive doses per year
for adults as the impact on the discharge of the low radioactive 
wastewater to the sea if they eat adjacent fish and seaweeds every day. 
The amount (0.6 mSv of effective radioactive doses per year) is one-forth
of annual radioactive dose to which the general public is exposed in 
nature. The level is similar to the evaluation we made before the 
discharge to the sea.

With the completion of discharge, as soon as the preparation work to 
accept high level radioactive wastewater at the Central Radioactive Waste
Disposal Facility such as water sealing is over, we will transfer the 
extremely highly radioactive wastewater in the turbine building of Unit 2
to the Central Radioactive Waste Disposal Facility and store under stable
conditions.
Also, from now on, as to the low level radioactive subsurface water in 
sub-drain pits of Units 5 and 6, we will transfer to a temporary outdoor 
tank and consider an appropriate radiation mitigation plan.

We wholeheartedly apologize for causing tremendous concern and 
inconvenience to all living near the power station and general public for
discharging radioactive water even the nature was an emergency escape.

We will closely monitor the evaluation result of the seawater sampling 
and conduct the environmental assessment. 
Attachment: Nuclide analysis of the radioactive substances in the seawater 
                                                                   (PDF 32.5KB) 
Attachment: Nuclide analysis of the accumulated water and water in the 
            sub-drain pits, Fukushima Daiichi Nuclear Power Station 
                                                                   (PDF 9.56KB) 
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