Wildfires in Fukushima: reliable data or disinformation?

The forest fire in the Ide area of Namie in Fukushima prefecture, which occurred on April 29, has been going on for almost a week.
See video 消火活動動画
Video and photo sources 写真と動画の出典 : 陸上自衛隊第6師団; JGSD 6th Division
The major media reported it at the time of the outbreak, but except for some local television news, the fire has not been covered much. Furthermore, the news does not pop out immediately on web sites, and we have to make a considerable effort to find the information. Let’s keep in mind that most of the nuclear accident victims have only cellphones, and not PCs, which makes it very difficult to search for the information if it involves several clicks and the opening of PDF documents.
The danger of the secondary dispersion of the radioactive substances is not mentioned at all in the announcement of Fukushima prefecture (see the picture below).
Equally, no mention is made about the danger on its homepage.
This is the announcement from Fukushima prefecture. The danger of the secondary dispersion of radioactive substances is not given to the residents, though it’s said that there is the possibility of repression of the fire.
As for the media, about the secondary dispersion of the radioactive substances that accompanies the fire, they say that there is no change in the radioactivity measurement values at present, and that there is nothing to worry about. The local newspaper Fukushima Minyu (in Japanese) calls for attention to the hoax about radiation risk.
The information source of the risk of secondary dispersion of radioactive substances used by the media is the data of airborne radioactivity measurements by monitoring posts and the airborne dust measurement published on the Fukushima prefecture website.
For those who have difficulties to open the PDF files, please look at the pictures below.
Are these data reliable?
In addition, the public relations of Fukushima prefecture as well as the major media say that there is no influence on inhabitants’ life and health because there is little variation in the airborne radioactivity measurements. Do the measurement values of the individual dosimeters or of the nearby monitoring post help the residents to judge the situation?
Currently, the “Fukuichi (Fukushima Daiichi) Area Environmental Radiation Monitoring Project” group and “Chikurin-sha” are collecting the data of airborne dusts by setting up linen and dust samplers.
We have received comments from Mr Yoichi Ozawa of the “Fukuichi Area Environmental Radiation Monitoring Project”, that we are reporting below.
A. Airborne radioactivity measures in terms of sievert are not appropriate.
“The problem is of that of the increased radio-contamination”
-The sievert is a measure of the health effect of ionizing radiation on the human body, and not a unit of measure of the environmental contamination (becquerel).
-It evaluates how much pollution has come in with the radioactive plume.
-The representative measuring device is a monitoring post (MP) that measures the radiation dose at one meter from the ground. The monitoring posts are installed after the decontamination work of the surrounding environment.
-MP measures only gamma rays, beta and alpha rays are not covered, and thus it is not suitable for environmental contamination evaluation.
-MP gives an average of 10 minutes measurements. Consequently, the result cannot reflect the passage of radio-contaminated plumes of a few seconds.
-Even if the dose is high, if there is less contamination, the fear of internal irradiation is less.
B. Reliability of the data on airborne dust published by Fukushima.
-The time period of the plume collecting in the environment is too short. The air is flowing.
In normal nuclear facilities, dust sampling takes about 20 minutes. It is because all air in the sealed room is absorbed in this time. However, it is not possible to absorb all air in the open environnent. Therefore, it takes a long time to collect the dust and to measure it. In our case, it takes us a week for sampling and from 2 to 4 days for measurement.
-The measurement time is too short. They should continue measuring until cesium 134 is detected.
-The result should be compared to the data before the accident.
-We cannot help thinking that all data are organized in such a way that they are either under the lowest limit (marked as ND – Non Detected) or they conform to the new standards.
We have installed linen cloths at 10 locations and air dust samplers in 2 places. The installation of linen surrounds the fire scene, like in the case of usual measurements of “Fukuichi Area Environmental Radiation Monitoring Project”. They are installed in Namie Town, Futaba Town, Okuma Town, Tamura City, Katsurao village, and Minami Soma City, surrounding the scene of the forest fire (Mount Jyuman in the map).
It is premature to draw conclusions about the secondary dispersion of radioactive materials.
I think that the peak will come after three to four days after the extinction of the fire. But then, the contamination will continue to move with the wind and rain.
In addition, a summary of the measurement results of the fallen leaves is underway. They are from the border between Namie Town and Katsurao Village, which is 4-5km west of the fire site. The contamination is lower than that of the fallen leaves collected at the Ogaki dam. We are also measuring the burnt ash.
We are working with Mr. Kazuhide Fukada, another member of “Fukuichi Area Environmental Radiation Measuring Project”, living in Miyakoji District, Tamura city. When we burn the fallen leaves measuring 5,710 Bq/kg, we obtain the ash of 19,500 Bq/kg that is, 3.4 times more densly contaminated in terms of weight. We can concentrate the contamination up to about 30 times artificially, but I think this is about the value in the natural environment.
In about two weeks, the data on airborne dust by the citizen groups will come out. We will publish the information as soon as it is known.
However, it is likely that the the environmental contamination fluctuation will become different by this fire, and we need long-term rather than short-term monitoring.
It would be most dangerous to stop monitoring and paying attention after the fire is extinguished. The current media reports seem to be leading us to that direction.
Just after the Tepco Fukushima Daiichi accident, the central government repeated many times that “there is no immediate risk on health”. The major media fled from Fukushima, and they diffused the news from Tokyo, saying that there was nothing to worry about in Fukushima.
We have not forgotten.
Fukuichi Area Environmental Radiation Monitoring Project web site (in Japanese)

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