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No way to find hot spots with dosimeter at 1m from the ground

Special thanks for their very important work to Kurumi Sugita of the Fukushima 311 Voices Blog and to Mr Yoichi Ozawa of the citizen’s measurement group named the “Fukuichi Area Environmental Radiation Monitoring Project“.
We have published several articles in this blog saying that to protect the population the Japanese goverment should take into account the soil contamination as well as the radiation dose in the air.  The policy to open the evacuation zones and encourage the population to return to live there (with the end of financial compensation and relocation aid) is based only on the airborn radiation dose measurements (the evacuation order is lifted when the radiation dose is under 20mSv/year).  We have been saying that this is very dangerous, even  criminal, for the air radiation dose rate (indicating the amount of radioactive dose received by a person within a certin period time) is useful with a well-identfied fixed source of radiation, but is not adequate to reveal the overall environmental contamination after a nuclear accident. It doesn’t account for the internal radiation exposure induced health hazards (note 1).
Now we would like to point out another problem related to hotspots: it is nearly impossible to find hotspots by the usual measuring practice of the airborn radiation dose rate (in sieverts per unit of time).  To illustrate this difficulty, we are translating here a Facebook post of Mr Yoichi Ozawa of the citizen’s measurement group named the “Fukuichi Area Environmental Radiation Monitoring Project“.
 
Here are the radiation dose rates, captured vertically above a highly radioactive substance (“black substance” or “black dust”) of 4,120,000 Bq/kg, measuring 79 μ Sv/h.
Below are measurements at different distances from the ground.
5cm:9.112 μSv/h
50cm:0.630 μSv/h
1m:0.251 μSv/h
Nov 30 2017.jpg
Conclusion: it is impossible to discover micro-hotspots right under your feet when you walk around measuring radiation doses at 1m of distance from the ground.
Measuring device:
Aloka TCS172B
Measurements carried out by Mr Yoichi Ozawa.
For 0cm from the ground, Aloka TCS172B, which cannot measure over 30µSv/h, was replaced by Polimaster PM1703M and Radex RD1706. The value is the average of the measurements of these two devices.  
 
Here is the video of the measurement.
As we can see from the graph above, the value in terms of Sieverts decreases drastically with the distance from the ground. At 1m, which is the usual reference height to measure the radiation dose rate, the value becomes very small even with the soil of over 4 million Bq/kg, which is absolutely enormous (note 2).
Some readers might be familiar with the image of a Japanese citizen measuring  radioactivity with a device at about 1m from the ground. This practice, almost unknown before the Fukushima Daiichi nuclear accident, has become widespread among citizens, although it has become rather a rare practice nowadays as many people have more or less become accustomed to live with radiation. Besides the fact that it is hard to live a life worrying about radiation around the clock and some people prefer to stop thinking about it, this “normalisation” of radiation is strongly enforced by a governmental security campaign. One of the methods employed is to focus on the external irradiation risk, neglecting the internal irradiation risk, by spreading the knowledge and data only in terms of the radiation dose in the air (measured by Sieverts), at the expense of other measurements such as the radiocontamination density in soil (surface contamination density in terms of Becquerel/unit of surface).
One of the now well-known problems of radiocontamination of the environment is that the contamination is not homogeneous, but dispersed with what is called a hot spot. This is a serious problem for the population, as the absorption of radioative particles contained in these hot spots can cause internal irradiation related health damage. And as we see above, it is extremely difficult to detect these hotspots, from 1m and above, even with the extremely highly contaminated substance such as “black dust”.
It is widespread belief among the public that if the value of the airborn radiation dose at 1m from the ground is under 0.23µSv/h (note 3), it is safe. This value, diffused by the authorities as well as by media, is indeed applied as the lower limit to carry out decontamination work.  Yet, as we have seen, even with the extremely highly contaminated substance such as “black dust”, at 1m, the radiation dose is only 0.25µSv/h, that is to say, only slightly over the limit of the 0.23µSv/h, which is believed to be the “safety level”.
It is unfortunate to say that for most of the residents taking the measurements of the airborn radiation dose by themselves, the values they observe have become rather an “encouraging” factor to continue living there or to return to live, than an alarming factor, as these values do not reveal but rather conceal the presence of hotspots which can cause internal radiation exposure induced health damage.
It is difficult to find hotspots anyway.  So when the soil contamination is high (see the concentration maps in this blog, for Namie, Minamisoma), it is better to keep the zone closed, continuing to aid the evacuated people.
 
Note 1: In opposition to the external radiation exposure which occurs when the human body is exposed to an external source, the internal radiation exposure is an exposure from inside the body due to the incorporation of radioactive particles through ingestion, inhalation or adhesion to skin.
Note 2: This extremely high level of contamination is understandable, for what is measured here is the infamous “black substance” or “black dust”, a kind of Cyanobacteria, about which we invite you to listen to podocast of Marco Kaltofen with English transcription.
Note 3: In fact, the 0.23µSv/h value is problematic in itself.  This is based on the 1mSv/year value following the ICRP (International Commission on Radiological Protection) recommendations on the public health.  However,  the 0.23µSv/h value is not the result of a simple division of 1mSv by 365 days x 24 hours. The calculation of 0.23µSv/h presupposes that people stay inside for 16 hours/day and that the radiation is reduced by 60% because of the building structure.  Then, the background of 0.04µSv/h is added. (1000µSv÷365÷(8 + 〈16×0.4〉) + 0.04  But in the real life in rural areas such as Fukushima, people spend more time outdoors.  Besides, some recent research has shown that in some cases the radiation dose can be higher indoors than outdoors because of the infiltration of hot particles. Thus, the reality is much more complex to apply uniformly the value of 0.23µSv/h as a safety threshhold. Lastly, many people in Fukushima were victimes of the initial exposure right after the accident. For such population, any exposure, whatever the quantity is, is to be avoided.

December 1, 2017 Posted by | Fukushima 2017 | , , , | Leave a comment

East Japan Soil Measurement Project of Minna no Data, Dec.2015 to Sept. 2016

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Source: http://www.minnanods.net/soil/pref17_colored/map17.html

September 26, 2016 Posted by | Fukushima 2016 | , , | Leave a comment

East Japan Soil Measurement Project of Minna no Data Site

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About This Project

It’s time to cooperate

When we started up MDS (Minna no Data Site, Everyone’s Data Site) we constructed inclusive and shared system on measuring data of food as the first stage, as there were many people who were concerned about food intake.

However, we planned to launch the measuring data of soil as a second stage after intensively equipped the system on food.

In autumn 2014, after one year from opening of MDS, we start up to platform soil measurement data. We, as citizens, try to start to map the status of soil contamination spread over East Japan.

The following is the reason why we stand up to start the East Japan Soil Becquerel Measurement Project. Objectives, outline and methodology of the project is explained.

Outline

In the Project, the method of collection is standardized in order to make comparison of data from multiple measurement laboratories. The Manual for Collection is developed by considering the easiest method of measurement within the limits of keeping accuracy, because many citizens conduct collection and measurement by themselves.

Collected soil is measured by the participating measuring laboratories of MDS. The result becomes open to the public and the report is sent to the collector.

Objectives

Radioactivity contamination by the accident of Tepko Fukushima Nuclear Power Plant is long term lasting.
The soil contamination map of broader areas is needed to understand contamination of neighborhood by measurement and comparison of data.

Though central and local governments conduct soil researches, those researches are insufficient because the value is lower by measuring deep place, or they measure only air dose.
As they decide the spot of measurement by mesh, the data what citizens want to know is lacking.

In our Project, we aim to grasp status of contamination where citizens make living every day. For example, place where children frequently play, where people pick wild grass, or where farmers work is being measured.

The Project aims that people can access necessary information as much as possible by utilizing data and database and by accumulating information which one can find at a glance and can search at ease.
We hope the result would be used as a tool for action for everyone.

Methodology

The depth of collection is from 0 to 5 cm, because most of cesium stays within 5 cm from surface of the earth.

Collection of soil should be conducted when it does not rain for several days, in order to avoid weight error caused by water. Less than 10 percent of moisture content is desirable.

Spot for collection is set at higher dose spot by measuring rate of air dose (1m5cm).
The extreme high spot such as micro hot spots and concentrated environment are excluded.

Collection is made by a method to compare results of each place.

Samples are measured at the participating laboratories of MDS.

  ・Measurement accuracy of those laboratories is ensured by the MDS original examination.

  ・The results are accumulated in the common database.

The result sof measurement are open to public on MDS. MDS has Japanese and English site.

Mapping of data is planned after gathering enough results.

Trial calculation of amount of radioactivity by a square meter is planned to be conducted. (Becquerel/ Kg →Becquerel /square meter)

Target areas17prefectures in east-Japan

Tohoku : Aomori Iwate Akita Miyagi Yamagata Fukushima

Kanto : Ibaragi Tochigi Gunma Saitama Chiba Tokyo Kanagawa

Chubu : Yamanashi Nagano Shizuoka Nigata

* In Iwate, the Soil Project Iwate had implemented measurement at more than 300 spots in 2012 and 2013.

The project activity will be made starting from requested districts. Individuals, groups and any organization such as school and daycare can participate in measurement of proposed spots. Proposing more than 5 spots are desirable.
The measurement spots will be decided after consultation basically in the same municipality.

How to support us: 
Collection of samples, payment of 2,000yen for measurement of one sample, payment of actual postage for samples.

How to feed back :
Sending result of measurement of the spots including spectrum, Reading and downloading data at MDS.

Support our site and project!
To those of you who are viewing this site from overseas, Thank you for visiting ”Minna no Data Site” (Combined Database of Independent Radioactivity Measurement Labs) .

MDS has stacked the data measured by the independent radioactivity measurement laboratories in response to the Fukushima Daiichi nuclear power plant accident, As of September 2014, the number of the food data became nearly 10,000.

For the benefit of those who worry about radioactive contamination of Japan from overseas, we opened the English site. We have started “East Japan soil measurement project” since October 2014 in addition to the food data.

From the fact that government has not done the adequate soil contamination survey for the citizens, this project promotes measuring soils of the places like parks, vacant lots, and educational facilities which are closely related to children’s daily life.

This project is based on the method of “Iwate soil measurement project “(2012- 2013) by citizens of Iwate Prefecture. If the method for collecting the soil is different, the results of monitoring vary greatly.

By using an easy-to-understand manual of the standardized method, you are able to compare, review and analysis the data from different locations. We will publish the measurement results of soil on this site.


We record the status of the radioactive contamination of Japan carefully from the standpoint of citizens, and hope that it will help people who are living with anxiety. For the people overseas, we are preparing the English version of data to show where and how much radioactively contaminated.

To run this project, big budget for measurement cost and update cost of web systems are required. There are 300 locations in each 17 prefectures in Eastern Japan, and each place costs about 4,000 yen.
Although it is planned to reduce costs and to ask for volunteers as much as possible, still the costs such as measurement costs, project management costs and Web systems costs are expected to some extent also.

It is a project of the scale that no one even challenged yet. We rely on your generosity to help funding for this project. We would appreciate your support from abroad. Thank you for your cooperation and support.


The information page of “East Japan soil measurement project” is currently in preparation. It will be published shortly.

◎Donate by the bank transfer
Postal Transfer:
Postal Transfer Account : 10090-85754261
Account Name: Minna no data site Unei Iinkai

Bank Account
Yuucho Bank Branch : Zero Zero Eight (Branch 008):
Interim : 8575426
Account Name: Minna no data site Unei Iinkai

Remittances in either USD or EUR can be made from overseas banks,.  
Please note that remittances to Japan cannot be made from certain financial institutions.
For details, please ask your local bank.

http://en.minnanods.net/#mds_indx_srch

http://en.minnanods.net/soil/soil_support.html

http://en.minnanods.net/support/supportourproject.html

Japanese Site

Contact

September 26, 2016 Posted by | Fukushima 2016 | , , , , | Leave a comment