Diffuse releases into the environment continue due to the very serious deterioration of the confinment barriers. TEPCO is continuing its actions to control these emissions, notably with the establishment of structures covering the buildings of the damaged reactors and underground barriers to manage groundwater.
The volume of water accumulated in the storage tanks and basements of the buildings reached nearly 900 000 m3 in early 2016.
Management of radioactive water
In 2015, a major milestone in the decontamination of water was completed. Since May 2015, around 600 000 m3 of water were treated with the ALPS radionuclide removal system and around 150 000 m3 were partially treated (removal of caesium and strontium, before complete treatment later on). The waste of the treatment processes have led to the filling of nearly 3 000 containers of radioactive waste, which are stored at the site.
Water treatment is only a first step towards managing the water accumulated on the site. Indeed, it is necessary for TEPCO to obtain authorisations for the release of treated water still containing residual radioactivity (mainly tritium). This situation forces TEPCO to store ever increasing volumes of water. The storage capacity has now reached about 1 000 000 m3.
Following the leakages found in the storage area, TEPCO decided to replace some types of tanks with welded tanks and initiated a vast retention area renovation and improvement programme. These developments, combined with the tightening of the surveillance, improved the management of the water storage facilities.
Download "Management of radioactive water from the damaged reactors" (PDF, 413 Ko)
Groundwater under the site
In early 2016, it appears that the provisions implemented by TEPCO enable the bulk of the groundwater contamination to be contained within the Fukushima Daiichi plant.
In order to understand the sources of radioactive contamination of the groundwater under the site, three different areas should be considered:
The inlet channel area
This area is located next to the harbour. Shortly after the accident, highly radioactive water from the reactors filled several trenches and passages and then spilled into the harbour.
With the draining of the trenches, the establishment of sealing barriers and pumping wells, TEPCO considers that it has managed to minimise the diffuse releases of contaminated groundwater into the ocean.
The nuclear buildings area
The basements of these buildings are filled with highly radioactive reactor cooling water (of the order of 70 000 m3). In addition, they receive significant inflows of groundwater (about 200 m3/day).
After a year of operation, TEPCO estimated in summer 2015 that the upstream pump wells - the "groundwater bypass wells" – had reduced seepage into the buildings from 400 to 300 m3/day. According to statements made by TEPCO in late 2015, the commissioning of the pumps in the drainage pits - the "subdrains" - around the buildings has also reduced seepage from 300 to 200 m3/day.
A test showed encouraging results with regard to freezing the ground. However, since August 2015 and the beginning of the rainy season, increased groundwater flows have led to a rise of soil temperature in most of the boreholes.
The tanks area
Created after the accident to manage the highly radioactive water pumped on the site, this tank installation area covers an area five times larger than that of the nuclear buildings. To date, around 750 000 m3 of radioactive water are stored there.
The implementation of the water treatment has reduced the radiological content of the water. Since the commissioning of the "groundwater bypass" in 2014, most of the contaminated groundwater from this area is captured by this device. Only the tritium remains detectable.
Download "Groundwater under the site" (PDF, 829 Ko)
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