JP5889038B2 - Decontamination method for geological contamination by radioactive materials - Google Patents

Description

  The present invention provides a large-scale decontamination for a wide range of geological contamination contaminated with radioactive materials such as radioactive cesium (Cs-134 and Cs-137) scattered in the atmosphere due to accidents or disasters caused by nuclear power generation facilities. It is about how to do.

  As a method for removing contamination by this type of radioactive material, a plurality of means are known as conventional examples. For example, as a first conventional example, in a chemical decontamination liquid treatment method for treating a chemical decontamination liquid containing an iron complex and a dicarboxylic acid produced by a chemical decontamination method using dicarboxylic acid, an n-type semiconductor and visible light are used. A reduction step of reducing a part of the iron complex by a reduction device using visible light emitted from the irradiation device, a removal step of removing the reduced divalent iron ions from the chemical decontamination solution by the cation resin tower, This is a chemical decontamination solution treatment method comprising a hydroxy radical produced in the reduction step and a decomposition step in which dicarboxylic acid is decomposed with divalent iron ions as a reduction product (Patent Document 1).

  According to this treatment method, the apparatus is downsized, the apparatus cost is suppressed, and iron and dicarboxylic acid in the chemical decontamination solution can be effectively removed.

  As a second method according to the conventional example, the radioactive deposits accumulated in the horizontal pipe portion of the pipe when the decontamination liquid is filled in the decontamination part of the equipment and facility of the radioactive material handling facility and chemical decontamination is performed. A radiation performance decontamination method for removing a clad, wherein a liquid driving means for generating a flow of the decontamination liquid that enables movement of the clad is provided, and the decontamination liquid in the horizontal pipe is provided outside the pipe. This is a radioactive contamination removal method in which a flow is generated and the clad is discharged out of the pipe together with the decontamination liquid by the flow of the decontamination liquid (Patent Document 2).

  According to the above radioactive decontamination method, an insoluble radioactive volume film that is a radioactive deposit in the pipe that accumulates on the bottom of the horizontal pipe of the primary system pipe by chemical decontamination can be performed by simple operation and work. It can be sufficiently removed and decontaminated to remove the radioactivity in a nearly complete form.

  A third method according to the conventional example is a radioactive cladding removing method for removing radioactive cladding deposited in the facility of a nuclear power plant, wherein the facility is used during chemical decontamination in which a decontamination solution is circulated in the facility. Energy is applied from the outside of the equipment to a high dose rate position of the radioactive clad in the apparatus, the radioactive clad is suspended in the decontamination liquid, and the radioactive clad is transferred by the flow of the decontamination liquid. This is a radioactive cladding removal method (Patent Document 3).

  According to this removal method, there is no need to install a radioactive clad removing device in the facility. Therefore, the radioactive cladding deposited in the facility of the nuclear power plant can generate secondary waste due to radioactive contamination or enter the facility. It can be suitably removed while preventing the entry of foreign matter.

JP 2006-162277 A JP 2011-153855 A JP 2011-203018 A

  In the first to third conventional examples, all of them are to remove or decontaminate radioactive contaminants such as soft or hard clad accumulated in the piping in the nuclear power generation facility with a decontamination solution. It is only necessary to decontaminate a narrow range of radioactive contaminants accumulated in a part of the facility.

  Radioactive material scattered in the atmosphere due to accidents or disasters caused by nuclear power generation facilities diffuses and floats over a wide area along with airflow along with fine materials, and the radioactive material falls to the ground, and environmental geological knowledge It is also known that radioactive Cs is adsorbed by fine particles such as clay minerals, and mass transfer of fine particles adsorbed by radioactive Cs is extremely important knowledge for investigation and decontamination of radioactive materials.

  In particular, fine particles adsorbing radioactive material that has fallen on the ground move by natural forces such as rainfall and wind, but mainly by surface water. The adsorbed fine particles of radioactive material that have moved in the surface water accumulate around the confluence of surface water. For example, adsorbed fine particles of radioactive material are collected as mud and garbage in a gutter beside a road or a catchment. And a high radiation dose is shown at a junction. High radiation doses are also observed at the confluence of roof gutters. The intermediate material of radioactive material accumulates as mud and garbage at the confluence of surface water from each watershed section of the roof and the earth, and the vicinity of the confluence of surface water on the downstream side (including the confluence of streams). To do. Therefore, a high radiation dose is shown around these merge points.

  In addition, in the water areas of confluences such as catchment basins and streams, the bottom of the water is often exposed to the ground due to a drop in water level, and there is also a dehydration effect from the accumulated accumulation, and the radiation dose per unit accumulation is even higher. Become. And the accumulation which shows the high radiation dose around the confluence point of a stream is eroded by the river increase at the time of heavy rain, and moves downstream. In addition, in soil grounds such as schoolyards, the radiation dose with a higher concentration is detected in areas where water can be pooled than in other flat areas. This is because it moves to the lower part and accumulates. Moreover, the radiation half-life of Cs-137 is 30.17 years, and is one of the two main medium-life fission products together with Sr-90, and is at least 30 years susceptible to radiation exposure. It can be said.

  In this way, the radioactive material scattered in the atmosphere diffuses over a wide range depending on weather conditions and the like, and when they are effective on the ground surface and vegetation, they move together with earth and sand by surface water due to precipitation. The radiation dose is inevitably increased in a portion or region where the fine-grained material such as earth and sand adsorbed with the radioactive material is repeatedly moved and accumulated. This is the law related to radioactive cesium geopollution, where the radioactive material in the Earth's atmosphere and geosphere is extensively eroded, moved, and accumulated, and the amount of radiation in the downstream accumulation area or region increases. It is.

However, in the conventional technology, radioactive contaminants such as soft or hard clad accumulated in the pipes of nuclear power generation facilities are simply removed or decontaminated with a decontamination solution, and a wide range of geological contamination is eliminated. It cannot be applied to dyeing.
Therefore, there is a problem to be solved in order to be able to decontaminate a wide range of geological contamination on the ground efficiently and over a long period of time based on the law of geological contamination.

The present invention provides a method for decontaminating wide-area geological contamination contaminated with radioactive materials scattered in the atmosphere in an accident or disaster of a nuclear power generation facility as a specific means for solving the above-described problem, and a river in a contaminated area A plurality of dams composed of small-scale sabo dams and a large-scale water-use dam are provided, and at least one settling sedimentation dam is formed in the large-scale water-use dam. In addition, the above-mentioned dams are used to deposit and accumulate fine-grained substances adsorbing radioactive substances, and the upper layer water of the accumulation layer is used for hydroelectric power generation, agricultural water, or industrial water. A decontamination method is provided.

The decontamination method for geological contamination with radioactive substances according to the present invention includes, as an additional requirement, providing a small-scale sabo dam along with the large-scale water utilization dam in the river.

According to the decontamination method for geological contamination with radioactive substances according to the present invention, a plurality of dams composed of small-scale sabo dams in addition to large-scale water-use dams are provided in a river in the contaminated area, and the large-scale water utilization The dam is formed with at least one sedimentation dam in its interior , and adsorbs radioactive material and moves with fine water such as clay minerals and earth and sand containing radioactive material. The particulate matter is efficiently introduced into the bottom of the dam by the sedimentation dam and the sediment is accumulated , and the radiation dose is halved or eliminated by maintaining for a long period of at least 30 years or more by the sediment accumulation. In addition, the fine water substance adsorbed with radioactive material settles and accumulates, so that the upper water is free from contamination by radioactive material. An excellent effect of being able to use this in.

It is explanatory drawing of the principal part which showed schematically the Example of the decontamination method of the geological contamination by the radioactive substance which concerns on the 1st Embodiment of this invention. It is explanatory drawing of only the principal part which showed schematically the decontamination method of the geological contamination which concerns on the other Example of this invention.

  A first embodiment of the present invention will be described. In FIG. 1, the region A side schematically shows the area or the plane of the region contaminated by the radioactive substance, and the region B side schematically shows the section of the equipment for decontaminating the radioactive substance. In the figure, fine particles such as clay minerals adsorbing radioactive materials such as Cs-134 and Cs-137 scattered widely in the atmosphere due to accidents or disasters at nuclear power plants Surface water gathers from a plurality of streams 1 and drains and flows into river 2.

  Radioactive materials on the ground such as mountainous areas are adsorbed by fine-grained materials such as clay minerals and earth and sand that are moved by surface water, and from a plurality of streams 1 in which fine-grained materials 3 adsorbed by the radioactive materials are branched. They gather and move sequentially to the river 2 of the required size. Therefore, a radioactive substance decontamination facility is provided in the river 2 where the fine-grained substance 3 adsorbed with the radioactive substance moves. In addition, if a detailed geological contamination survey is conducted and a high-concentration radioactive material is expected to flow out, a continuous dam will be constructed, and the radioactive material adsorbing Cs-134, Cs-137, etc. will reduce the convection time in water. Increase the length and promote sedimentation to the dam.

  This decontamination equipment is, for example, the power generation / water utilization dam 4, and the water level in the dam varies from the water utilization side. A drain pipe or an outflow portion 6 is provided above the dam body 5 of the dam 4, and a hydroelectric power generation facility 7 is provided using a drop of water discharged or discharged from the drain portion 6. In this case, the power generation scale may be small enough to be managed by the local government.

  By providing the water-use dam 4 in this way, the fine-grained material 3 adsorbed by the radioactive material flowing into the river 2 is successively deposited and accumulated at the bottom of the dam 4, and the upper water collected in the upper layer Since there is almost no radioactive material in 8, it can be used for power generation or as agricultural water. And the fine-grained material 3 which adsorb | sucked the radioactive substance accumulates for a long time as the accumulation | aggregation 9 in the bottom part of the dam 4, If the accumulation state can be maintained for 30 years, a radiation dose will be reduced to a half and will not affect a human body. It is reduced. The generated power may be transmitted to a required place via the transmission line 10 and used as household, industrial, or other power sources in the area.

  Next, another embodiment shown in FIG. 2 will be described. Note that the same parts as those in the example according to the first embodiment are described in duplicate, and thus the same reference numerals are given and detailed descriptions thereof are omitted. In this embodiment, in particular, at least one or more sedimentation dams 11a and 11b having a height lower than the dam body 5 and the water pipe 6 are provided so as to partition the water use dam 4. . By providing the sedimentation dams 11a and 11b in this way, the fine-grained material 3 adsorbing the inflowing radioactive material is blocked to some extent by the sedimentation dam 11a upstream of the dam. Then, the finely divided fine substance 3 that overflows the sedimentation dam 11a is further dammed by the next sedimentation dam 11b, settled, and finally dammed by the dam body 5. Most of them are accumulated.

  By providing the sedimentation dams 11a and 11b in the water use dam 4 in this manner, the sedimentation dams 11a and 11b are sequentially dammed from the upstream side so that radioactive substances in the dam 4 The re-migration can be limited to a minimum, and the fine-grained material 3 adsorbing the radioactive material in the water flowing into the dam 4 has a long convection time in water. Accordingly, the radioactive material that has been dammed by the sedimentation dams 11a and 11b sequentially from the upstream side and has a long convection time is deposited and accumulated on the upstream side, and the radioactive material contained in the upper water 8 in the dam 4 is accumulated. Since the water is further thinned, the water discharged or discharged from the drainage portion 6 contains almost no radioactive substance.

  In the illustrated embodiment, only one dam 4 is shown, but a plurality of large and small dams, for example, a small sabo dam and a large dam are formed in combination in series along the river 2. The dyeing effect is increased. In other words, polluted water or pollutants used for decontamination in places with high radiation doses by human work, and fine-grained substances 3 adsorbing radioactive substances that move by erosion due to heavy rain are temporarily accumulated in a sabo dam. In addition, it can be accumulated until it is moved to a large dam by precipitation and the radiant energy becomes zero.

  In this way, the radioactive material scattered in the atmosphere falls to the ground, and the radioactive material is adsorbed by the fine-grained material 3 such as clay mineral and earth and sand. The stagnation or sedimentation is accumulated in the drainage area, and at least a large-scale water utilization dam 4 as a decontamination facility is formed in the river in the contaminated area by utilizing the phenomenon or property, and the bottom of the dam 4 The fine-grained material 3 adsorbing the radioactive substance is precipitated and accumulated, and the upper part of the accumulation layer 9 is sealed with the upper water 8 so that the radioactive substance does not leak outside the dam.

  In any case, the method for decontamination of geological contamination by radioactive material according to the present invention is basically based on the law of geological contamination by radioactive material scattered in the atmosphere. It is possible to reduce the radioactivity by halving by precipitating and accumulating fine particulate matter that has been adsorbed to the dam and maintaining it for a long period of time. It can be widely used.

DESCRIPTION OF SYMBOLS 1 Stream 2 River 3 Fine-grained material 4 Dam 5 Levee body 6 Drain pipe 7 Hydroelectric power plant 8 Upper water 9 Accumulated layer 10 Transmission line 11a, 11b Settling sedimentation dam A Area side with facilities for decontamination of substances

Claims (1)

A method for decontamination of wide-area geological contamination contaminated with radioactive materials scattered in the atmosphere due to an accident or disaster of a nuclear power generation facility,
Established multiple dams consisting of small sabo dams along with large irrigation dams in rivers in contaminated areas,
In the large-scale water utilization dam, at least one sedimentation dam is formed inside the dam ,
Precipitating and accumulating fine particulate matter adsorbing radioactive material in the dams,
A method for decontamination of geological contamination with radioactive substances, wherein the upper layer water of the accumulation layer is used for hydroelectric power generation, agricultural water or industrial water.

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