evacuation areas, which was reviewed in the "Basic Concept for Reviewing Alert and Evacuation Areas in Response to the Completion of Step 2 and Issues to be Reviewed in the Future" (Nuclear Emergency Response Headquarters, December 26, 2011). Since the formulation procedure closely relates to actual reviews of the evacuation areas, the Decontamination Plan for Specified Areas will be formulated in close collaboration with the stakeholders including related municipalities, while implementing pilot verification programs and initial decontamination programs.

Under the Decontamination Plan for Specified Areas, decontamination programs will start with enough preparation, including surveys of buildings and obtaining agreements.

① Pilot verification projects (collecting technical knowledge)

From November 2011, a decontamination experiment as a pilot verification project was implemented in the Emergency Planning Zone and the Evacuation-Prepared Area in Case of Emergency to verify techniques needed for effective decontamination. Pilot verification projects have been conducted in all respective planned decontamination areas except Futaba-cho since November 2011, and the results of the dose reduction project were reported at the end of March. The main points of this project are as follows below.

○In the areas where the air dose rate was less than an annual accumulated dose of 30 mSv, air dose rates were reduced to less than an annual accumulated dose of 20 mSv after decontamination.

On the other hand, where the experiment was performed in an area where the air dose rate was more than an annual accumulated dose of 40 mSv after decontamination, 40% to 60% of the air dose rate was reduced; however, the air dose rate did not fall to less than an annual accumulated dose of 20 mSv.

In the areas where the dose rate was low, a method minimizing the removed objects was tried, but the rate of reduction in the air dose rate was lower than it was in the areas where the air dose rate was high, while the quantity of removed objects was reduced relatively well.

○In each area, flowing water (including water collected in side ditches) or water that had collected before the accident (pool water) was processed with filtering, adsorption, agglomeration, and sedimentation depending on the degree of contamination. All methods resulted in all wastewater satisfying the standard regulated by the Nuclear Reactor Regulation Law.

O $ ^{1} $ Volume reduction with high temperature incineration did not result in dispersion of radioactive materials to outside with smoke, which had stuck to branches and leaves, and this method was also highly efficient in volume reduction. Moreover, with the process using bag filters and HEPA filters, concentrations of radioactive cesium in smoke exhaust was confirmed to be such that it is possible to achieve concentrations of radioactive material in the air that are sufficiently lower than is regulated by law.

○Regardless of the annual accumulated dose or land use classification, in almost all areas, more than 80% of radioactive materials could be reduced by removing at most 5 centimeters of topsoil. However, the thickness of removed soil that directly relates to the quantity of removed radioactive material needs to be determined in consideration of the depth and direction of the concentration of radioactivity, and the decontamination goal.

Implementation of the model project will continue both in the present and future, and knowledge on the effects and applicability of the decontamination techniques will be accumulated; the knowledge acquired at this point will be applied to future decontamination projects.

Photo 2-4-1 Pilot Decontamination Project

Photo: Ministry of the Environment

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## Decontamination and other efforts

Effective decontamination methods vary according to the radioactive material. Before starting decontamination, radiation is measured to select the optimal decontamination method. Radiation dose is also measured after completion of decontamination to check efficacy.

Examples of decontamination methods in places with relatively low radiation include: cleaning rain gutters installed under the eaves of local homes, mowing grass

Cleaning space under eaves and in rain gutters

Photo: Ministry of the Environment

Removing sludge in street gutters (photo: Fukushima City)

Source: Ministry of the Environment, Radioactive contamination information website

and cutting back wooded areas, and removing sludge in street gutters.

Examples of decontamination methods for places with relatively high radiation include: scraping surface soil in schoolyard with heavy machinery and removing thin layers of leaf mold by hand. Examples of decontamination for roofs and similar places include pressure-washing and watershoot decontamination.

Mowing grass and wooded areas (photo: Date City)

② Initial decontamination (prerequisites for full-scale decontamination)

From December 2011, the Self Defense Forces and other parties had already begun decontamination efforts, such as decontamination of the Joban Expressway. Initial decontamination will be continued in the future for locations such as public facilities (e.g., municipal offices and community centers) and infrastructure facilities (e.g., facilities for clean water and sewage water).

To implement full-scale decontamination in the future, it is necessary to implement initial decontamination at key decontamination facilities (e.g., municipal offices and community centers), roads accessing the area, and infrastructure facilities supplying water and other materials needed for decontamination.

## ③ Full-scale decontamination

Full-scale decontamination is scheduled for soil in residential areas as well as for offices, public buildings, roads, agricultural land, and forests around living areas by the end of March 2014, in order to gradually deliver the removed soil to properly managed temporary storage spaces.

The Ministry of the Environment stated its Basic Concept of Interim Storage Facilities That are Required as an Initiative to Address Environmental Contamination by Radioactive Materials Caused by the Accident at the TEPCO Fukushima Daiichi Nuclear Power Plant in October 2011, and requested discussions to site it in Futaba, Fukushima Prefecture at the end of 2011. In March 2012, discussions were held among Futaba municipality, Fukushima Prefecture, and the national government, and the national government proposed a plan to site it in multiple areas. The national government will make maximum efforts to start operations in three years after the beginning of full-scale emplacement into temporary storage areas.

## ④ Decontamination of specified areas

The Minister of the Environment has specified municipalities that need intensive surveys and measurement of environmental contamination due to accident-based radioactive materials. The specified areas are those that have an average radiation dose of at least 0.23 $ \mu $ Sv per hour (areas with at least 1 mSv of annual additional exposure). The specified municipalities shall determine areas where actual decontamination measures will be taken.

The concept for implementing decontamination indicates that it is appropriate to take measures while making due consideration of the actual situation in each location, and to take measures that focus on the lives of children, since even places with relatively low additional exposure sometimes have higher radiation than peripheral areas. Under this concept, decontamination shall be implemented according to the basic policy formulated under the Act on Special