JP2013068586A - Method for removing radioactive contamination of soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that in almost conventional methods for removing radioactive contamination of soil caused by an accident of a nuclear power plant, soil contamination is performed by removing a surface layer of contaminated soil only by several centimeters and separating the removed contaminated soil from clean soil, but destination of the separated contaminated soil is not determined, and a place for storing the contaminated soil for a long period should be determined.SOLUTION: The contaminated soil on the surface layer is soaked in environmental water with less radioactivity such as uncontaminated rain water or ground water of the same amount as that of contaminated rain or snow causing the radioactive contamination of soil, discharging of the dipped water to the outside or downstream is repeated to finally discharge radioactive contaminated substances of the soil to the sea through rivers.

Description

The present invention relates to a method for removing radioactive contamination of soil derived from a nuclear accident.

The Fukushima Daiichi nuclear power plant contaminated the soil with radioactivity in Fukushima Prefecture and other vast areas nationwide. For the decontamination, the soil of several centimeters of surface is shaved and a vinyl sheet is applied to it to collect it in a corner of the land, or it is packed in a bag and collected in a temporary storage place to take temporary preservation measures.

When cutting the surface soil, it is necessary to use a machine such as a UNIC crane, but when cutting the surface of the soil, dust containing radioactive materials is generated. In general, such a working environment has a high radiation level, and there are many cases that require legal approval of radiation workers. Since ordinary workers who do not have sufficient knowledge about radiation exposure are forced to work, there are cases where violations of the law occur. The method of cutting the surface layer has such a problem.

Moreover, these contaminated surface soils are only collected temporarily, and there is no plan for the treatment method or destination. Where to go to that destination is a serious issue for the state and local governments.

Learn the following examples of changes in past radioactivity levels over time to solve challenges:
The uranium-type atomic bomb was dropped on Hiroshima in 1945 and the plutonium-type atomic bomb was dropped on Nagasaki, and it was expected that people would not be able to live for several decades. Reconstruction has begun, and even radioactivity can no longer be detected. In the Bikini Islands, from the nuclear test in 1946 to the hydrobombing test in 1954, a total of 66 nuclear tests were conducted by 1958, but the environment will recover until the residents finally return in 2011, 53 years later did. The accident at the Chernobyl nuclear power plant was in 1986, but even 25 years later, it cannot be said that it has recovered very much. Solving where the differences are is the key to solving the problem.

Regarding the time-dependent change in the radioactivity concentration in domestic soil by nuclear tests, please refer to Agricultural Research Report 24, 1-21 (2006) ( http://www.affrc.go.jp/agrolib/RN/000096962.pdf ). detailed. Here is a summary of the relationship between paddy and field soils and the observed half-life:
Paddy soil 90Sr: 6-13y, 137Cs: 9-24y, field soil 90Sr: 6-15y, 137Cs: 8-26y are important. This data means that the half-life of soil in the actual environment may be shorter than the half-life determined by physics.

In the latter half of the nuclear accident, most of the radioactive materials in the soil are radioactive cesium and radioactive strontium, and iodine can now be ignored.
The former is soluble in water and the latter reacts violently with water. This makes it possible to hypothesize that these radioactive substances in the soil stay with water and move with water. The environmental radioactivity in Hiroshima and Nagasaki disappeared in a much shorter time than the physical half-life, because these areas were typhoon passages, and radioactive materials were dissolved and flowed into the sea due to frequent heavy rainfall. This is considered to be the reason. By the way, in terms of annual precipitation, Nagasaki Prefecture is ranked 12th (1840 mm), Hiroshima Prefecture 38th (1149 mm), and Fukushima Prefecture 42nd (1149 mm). In Fukushima Prefecture, the amount of precipitation appears to be large due to snow, but since it stays in the snow during winter, the natural soil cleaning effect is much less than in Hiroshima and an artificial measure is required. The same is true for the Bikini Islands, and conversely in Ciel Nobyl, this effect is thought to be less because of the low precipitation.

If the Agricultural Research Laboratories data is rearranged from the viewpoint of precipitation, the understanding should be improved. It is suspected that the water in the paddy field was polluted that there was no difference in the half-life between the field soil and the paddy field in the data from the National Agriculture Research Institute. Recently, in September in Kanto, Typhoon No. 12 rained a lot of rain, but in Yango-cho (current Ishioka City), the spatial radioactivity level was 0.2 microsieverts / hour, which is over 30%. (Measured by doseRAE2). This is thought to be due to rain entering the topsoil due to rainfall, dissolving radioactive cesium and flowing radioactive material downstream.

Because there is little radioactive material in the rain, the radioactive material such as cesium contained in the soil is dissolved with this clean water with weak radioactivity and released from the stream to the river and into the sea to accelerate the physical half-life. It is possible to discharge radioactive materials in the soil and shorten the half-life of the radioactive soil.

Furthermore, in order to accelerate the removal mechanism by washing with water, a large amount of clean water is produced. In areas that are already heavily polluted, deep wells are dug and poured into the soil of rice fields and fields, leading to rivers. Children's halls, kindergartens, elementary and junior high schools, and the entire school grounds are considered to be rice fields. At that time, it is necessary to take care to improve the “communication” of water with a high-pressure hose or the like so that contaminated water does not stay. This can be scaled down at home. Examples are not good, but NHK and others have reported successful decontamination by washing roofs and verandas.

If this washing and decontamination method is repeated artificially, all radioactive materials are finally released into the ocean. Even if nothing is done, the same thing happens with natural decontamination. People only accelerate decontamination through the back of this mechanism. To further accelerate this water decontamination method, artificial rain can be applied to the entire contaminated area. Most of the radioactive contamination was originally carried by black rain. You can clean it with clean rain with little radioactive material. “Blade for blade, rain for rain”.

There are methods using dry ice and silver iodide, which are used in China and the like (http://ja.wikipedia.org/wiki/artificial rainfall), to cause artificial rainfall to fall over a wide area. As a more conspicuous method, it is conceivable that the typhoon is artificially induced by HAARP (High Frequency Active Research Program) or the like, but Japan does not have the technology so far. In this respect, Typhoon Ginza Street, such as Okinawa, Kyushu, Shikoku, and Kii Peninsula, is the best place for natural purification. Fortunately, Nagasaki and Hiroshima were in it, so it is thought that decontamination was carried out naturally in 2-3 years (hypothesis).

The radiation removal method of the present invention is essentially equivalent to a removal mechanism by natural providence. It is intended to shorten the half-life of radioactivity by personally strengthening the decontamination method by natural providence. The present invention has a great advantage in that it is not necessary to specially prepare a land for the destination of the pollutant by decontamination. Japan also has abundant groundwater and its cost is low. Since the water used for washing also flows into the sea, this method is incorporated in the natural circulation system.

In the first invention, the contaminated paddy field is filled with clean water instead of contaminated water, radioactive cesium, etc. in the topsoil is dissolved in clean water, and after confirming this with a radiation measuring instrument, discharge. In urban areas, it is discharged into sewage. During the process, clean up irrigation channels and sewage to prevent dirty water from staying, and monitor most of the radioactive dissolved water flowing into the ocean through the river.

Large quantities of radioactive material are already stored in the ocean from reprocessing plants, nuclear power plants, illegal dumping of radioactive materials, and nuclear submarines. The amount is unknown because there is no international monitoring, but it is estimated to be enormous compared to the amount from the Fukushima nuclear power plant to the environment. Nevertheless, no substantial failure has been reported yet.

The application of the present invention is small from individual households, some of which are decontamination of farmer's rice fields, and most are decontamination and scale of fields in the region. Population rainfall can be practiced by companies and national agencies such as the Japan Meteorological Agency because of the need to fly rockets. HAARP, etc. for controlling the course of typhoons will be a larger project, and will be a joint project with national projects in industrialization.

Claims (3)

      After immersing soil such as radioactively contaminated fields, rice fields, gardens and schoolyards from nuclear reactor accidents in clean natural water such as clean water, river water, and well water, irrigation channels and sewers downstream The removal method of radioactive pollutants learned from the natural cleaning mechanism by repeatedly flowing into the river.       A method in which the clean water used in claim 1 is obtained by human rain or the like, and after confirming that it is clean, radioactive contaminants are repeatedly removed by washing with water.       A method for removing radioactive pollutants in a region by repeatedly washing with a large amount of rainwater used in claim 1 by guiding tropical cyclones and typhoons to a radioactive contamination treatment region by an artificial method.