The Earthquake and Fukushima Revitalization Efforts
On March 11, 2011, a massive earthquake occurred and the coastal areas of Fukushima were struck by a tsunami.
The tsunami caused an accident at the Tokyo Electric Power Company’s Fukushima Daiichi Nuclear Power Station, resulting in the release of radioactive materials that had an extremely severe impact on a wide area.
We have been carrying out environmental restoration projects with a scale and methods never before seen in the world.
It has been 11 years, and the projects for environmental restoration and revitalization are still continuing today.
About the Great East Japan Earthquake
14:46 on March 11, 2011:The Great East Japan Earthquake
Earthquake and tsunami
On March 11, 2011, a magnitude 9.0 earthquake with a seismic intensity level of 6 – 7 occurred. It was one of the largest earthquakes ever recorded in the history of Japan. The earthquake was centered offshore of the Sanriku Region at a depth of around 24 km. It produced a giant tsunami that struck the Pacific coast of Japan centered on Iwate, Miyagi, and Fukushima Prefectures.
Accident at the Tokyo Electric Power Company’s Fukushima Daiichi Nuclear Power Station
The tsunami produced by this earthquake resulted in an accident at the Tokyo Electric Power Company’s Fukushima Daiichi Nuclear Power Station.
Environmental contamination by radioactive materials
The radioactive materials that were released in to the atmosphere fell in rain and other precipitation onto the ground, buildings, and trees, contaminating the soil and generating contaminated waste.
Immediately reducing the impact of this contamination by radioactive materials on human health and the living environment was an issue of the greatest urgency.
Environmental restoration projects being carried out for environmental restoration and revitalization in Fukushima.
The Act on Special Measures Concerning the Handling of Radioactive Pollution was passed (taking effect January 1, 2012) in order to immediately reduce the impact on human health and the living environment. Based on this law, work for decontamination and treatment of contaminated waste was carried out with the cooperation of many people.
Decontamination
In order to reduce the impact of radiation on people and the environment, radioactive materials are removed or covered with shielding materials.
Long-term Goals
In addition to the natural attenuation of radioactive materials, decontamination and health management measures are aimed to keep the additional exposure dose below 1 mSv/year in the long term.
Decontamination Methods
Radioactive cesium is easily adsorbed by clay minerals, and once fixed, it is difficult to dissolve in water. Therefore, in order to reduce the radiation dose from radioactive materials in the environment, we first took measures to remove, shield, and keep the soil with away from radioactive cesium attached.
Residential Areas
Surface soil was removed from gardens, and replaced by additional soil from outside.
Leaves and other accumulated materials were removed from rain gutters.
Roofs were wiped, and accumulated materials were removed.
Agricultural land
In rice paddies and fields, the following methods were taken:
1) Surface soil was removed, and replaced by an additional soil 2) Reversal tillage which replaces bottom soil at a depth of around 30 cm 3) Deep plowing of fields
Road
Remove sediments (leaves, moss, mud, etc.).
Paved surfaces may be cleaned with brushes or high-pressure water.
Forest
Remove fallen leaves, branches, etc. within an effective area of approximately 20 m from the forest edge.
If removal of fallen leaves, etc. alone is not effective enough, remove remaining fine fallen leaves and other sedimentary organic residues.
Decontamination of agricultural land (Okuma Town)
Implementation of Decontamination
With the exception of areas that are restricted, whole area decontamination has been completed, and the evacuation order for areas where whole area decontamination has been completed has been lifted.
Intensive Contamination Survey Area (ICSA)
An Intensive Contamination Survey Area is an area where the hourly radiation dose is 0.23 micro sieverts or more. The municipal or prefectural government is in charge of decontamination in these areas.
Special Decontamination Area (SDA)
Special decontamination area is "Restricted area" within a 20 km radius of TEPCO's Fukushima Daiichi Nuclear Power Station and "planned evacuation area" where cumulative doses may reach 20 millisieverts within a period of one year after the occurrence of an accident with a radius of more than 20 km. The national government took the lead in carrying out decontamination.
Interim storage
Interim Storage Facility is used to manage removed soil and waste materials. It is located in the area surrounding the TEPCO's Fukushima Daiichi Nuclear Power Station, and the towns of Okuma and Futaba have made a very serious decision to accept it. It covers an area of approximately 1,600 hectares.
Interim Storage Facility
Reception / separation facility (exterior view)
Reception / separation facility (interior view)
Soil storage facility
Temporary treatment facility
Waste storage facility
Recycling and final disposal
Technologies for reducing waste volume are under development and projects related to recycling are being carried out for the final disposal of removed soil and other materials generated in Fukushima Prefecture to outside the prefecture.
Recycling of removed soil and other materials
* 8,000 Bq/kg is equal to the upper-limit concentration for radioactive waste that can be disposed of in conventionally managed landfills without additional protective measures. The additional radiation dose received by nearby residents and workers is less than 1 mSv per year.
Working towards recycling and final disposal: Example of a demonstration project
Recycling demonstration project in Nagadoro District, Iitate Village(Started Nov. 2018)
This demonstration project precesses recycled materials in which trees and plants, metals, and other materials are removed from the removed soil, and verifies factor including stability of embankments created using the recycled materials. In the Specified Reconstruction and Revitalization Bases Area in the Nagadoro District of Iitate Village, removed soil from a temporary storage facility in the village is recycled and used as a resource for test cultivation of flowers, vegetables, and other produce in a raised earth test yard. The results from measurement of radioactive cesium concentration in food crops have been below the minimum detection value. (With the method prescribed by the Ministry of Health, Labour and Welfare for measurement of radioactive cesium in food, the minimum detection value is 20 Bq/kg or less. Measurement results until detection were 0.1 - 2.5 Bq/kg. This is well below the standard value of 100 Bq/kg for radioactive substances in general food products.)
