Figure 1. Decontamination Zones (From the Ministry of the Environment website)

    Decontamination is now ongoing in many areas, including Fukushima. This article summarizes the current state of decontamination. Although we use the term “decontamination,” since the radiation does not disappear, it should perhaps more properly be termed “relocated contamination,” but here we use the term “decontamination.”

Basic Policy

    The actual organization carrying out the decontamination differs according to the degree of contamination with radioactive material in each target zone, the zones being divided into Special Decontamination Areas, which are directly controlled by the national government, and Decontamination Implementation Areas, where decontamination is carried out by the local municipality.
    Of the former, where the pre-decontamination level exceeded 20 milliSieverts/hour (mSv/yr), decontamination targets have been set based on the results of model decontamination projects and so on, and in zones where the pre-decontamination level was lower than 20 mSv/yr, a target of a 50% reduction in dose rate has been set for August 2013. Additionally, a 60% reduction will be aimed for in the daily life environment of children, such as schools and parks. These targets include the physical decay of radioactive cesium, which would show a roughly 30% reduction in two years and five months after the nuclear accident due to the radiological half-life even if no action were taken. The long term target is to reduce the dose rate to less than 1 mSv/yr.

    The latter are zones where the air dose rate exceeds 0.23 microSieverts/hour (μSv/h). It is possible that this is based on a standard of 1 mSv/yr. (Depending on the location, natural environments are usually thought to be less than 0.1 μSv/h.) Decontamination plans are formulated by each municipality.

Decontamination Effectiveness

Figure 2. Roofing Materials Left to right: slate roof, clay tiles, cement tiles

    According to the Ministry of the Environment Decontamination Model Demonstration Project Report1), decontamination methods show high effectiveness in some cases and low effectiveness in others, and there is wide variation depending on the location and the actual object being decontaminated.

    Looking, for example at the radioactive material decontamination rate for wiping methods, a 57% effectiveness was achieved for house walls and so on. While it was as high as 77% for clay roof tiles, only low effectiveness was achieved for cement tiles (0%) and slate roofs (24%). In cases where the clay tiles contained cracks, the decontamination effectiveness was 0%. As a result of house decontamination, the air dose rate in the vicinity of the house at a height above the ground surface of 1 m was reduced by an average of 18% to 74%. Out of ten model decontamination zones, only three zones were able to reach the 50% reduction target. It would seem that the expected effectiveness could not be achieved in actuality.

    The realities of decontamination carried out under the report are described in another report2) by Kenichi Hasegawa, a former resident of the Maeda district of Iitate Village. The crews who came to carry out the decontamination did not even try to decontaminate difficult objects such as old houses with cement tiles or houses with clay walls, but simply stuck “difficult to decontaminate” stickers on them. As a part of the decontamination operations they also felled large trees that had been planted as windbreaks and just left them lying where they fell, making the situation actually worse than it had been before.

    In addition, there are reports that the air dose rate declines immediately following the decontamination of a house, but rises again after some time has passed. This is probably because only an area of 20 m around a house is decontaminated, and therefore cesium returns to the grounds of the house from the mountain forests in the surrounding area due to the action of wind and rain.

The Sloppy Reality of Decontamination

    To add to the problems, the Asahi Shimbun reported on widespread negligence in decontamination operations in a scoop on January 4, 2013. At first, the general construction contractors who were involved in the decontamination work denied the negligence, but were finally forced to admit problems when they were faced with robust video evidence amassed by the Asahi Shimbun research team. The video showed fallen leaves collected as part of the decontamination, which should be appropriately handled, being simply kicked into a river; the runoff from roofs and verandahs washed with high pressure hoses not being recovered; the runoff from car parks decontaminated with high pressure hoses being allowed to drain off into side gutters instead of being reclaimed, and so on. The Ministry of the Environment finally awoke from its slumbers on January 24 to set up a decontamination 110 hotline3) and called on the population to provide information. By February 14, however, in a display of unenthusiastic management, the ministry refused to recognize the seven cases reported as instances of improper decontamination due to the difficulties of confirming the facts.
    Despite the fact that the Act on Special Measures for Toxic Waste contains punitive regulations for such widespread improprieties, and the fact that the decontamination guidelines stipulate detailed operations, the cause of the problem appears to be that the Ministry of the Environment has thrown the whole operation over to the general construction contractors and is totally unable to manage what goes on (See Nuke Info Tokyo 153 page 8).

    For the Decontamination Implementation Areas, where decontamination is carried out by the local municipality, national government subsidies are available for the costs of the decontamination. The problem is that the work for which subsidies are available does not match with the realities on the ground. As an example, the Gunma Prefecture Council adopted a written opinion demanding that the total cost of radioactive material decontamination be borne by national subsidies, pointing out that “The basic operation (the decontamination method covered by the subsidy) was deep cutting of lawns. However, the decontamination of the surface soil and the re-laying of the lawns were not recognized as being covered by the subsidy. In some places the deep cutting of the lawns did not result in the reduction of the dose, and there were many problems in the implementation of decontamination in the municipalities.”4)

Moves to Review Targets without Debate

    Large areas of Fukushima Prefecture have been designated evacuation zones because of the nuclear accident. Along with a grasping of the reality of the air dose rates and their decline, a review of the evacuation zones is ongoing, but many municipalities are making the achievement of the long-term target of decontamination, 1 mSv/yr, the condition for the return of the population. According to a Yomiuri Shimbun news report, on February 17, 2013, the Governor of Fukushima Prefecture, during an exchange of views with the national government, demanded that the 1 mSv/yr target be reviewed. The 1 mSv/yr target had originally been “the strong desire of Fukushima,” but since with the low level of decontamination effectiveness the return of the prefecture’s people now enduring daily life in evacuation has greatly receded into the future, it can be said that this was a demand to relax the target instead. The previous minister for the environment, Goshi Hosono, stated in a separate Yomiuri Shimbun interview published on March 10 that   while “the position of the national government is to make efforts toward achieving 1mSv, even if that takes time, it is also important that the dose level and the decontamination methods are handled in a flexible manner in line with the wishes of the towns and the residents.”

    However, if the wishes of the residents are to be respected, then efforts should be put into achieving the 1 mSv/yr target, and it has to be said that claiming that relaxation of the standard is in line with the wishes of the residents is putting the cart before the horse.

    What is necessary above all is that the national government should indicate clearly its willingness to carry out the following three points and discuss matters with the residents:

1) the risks of living for extended periods in an area that would be of high exposure rates be explained,
2) compensation by the national government should health impacts occur, and
3) the provision of funds for those who wish to evacuate or relocate to other regions.

 Sluggish plans and implementation

    There are huge doubts about the effectiveness of the decontamination, but lastly let’s look at how fast progress is being made. Although the total number of zones scheduled for decontamination has not yet been finally determined, according to a news report5), as of March 3, 2013, in 715,740 scheduled locations (e.g. private houses and so on), only 46,015 places have been completed, a mere 6.5%. Even if this were compared with the number of scheduled locations (148,378) to be completed by the end of FY2012, it would still only be a completion rate of 31%. It would seem that the FY plans are almost impossible to achieve.
    There are various reasons why the plans are not progressing satisfactorily. To understand this, it would be necessary to look at each area in detail, but one of the serious issues is thought to be the difficulty in reaching agreement over the location for depositories for the waste materials that result from decontamination.


Hideyuki Ban (Co-Director of CNIC)


References:

1) http://josen.env.go.jp/material/download/pdf/model004.pdf
2) “‘Beautiful villages’ will not return under a bogus ‘reconstruction,’” Sekai, April 2013, Iwanami Shoten
3) https://josen.env.go.jp/tekiseika/report_summary.html
4) http://www.pref.gunma.jp/gikai/s0700522.html
5) Yomiuri Shimbun, March 3, 2013.



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