JP2013083616A - Method for removing widely-spread radioactive contaminant using pressurized water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for removing widely-spread radioactive contaminants using pressurized water and solve such problems that methods conventionally performed when removing radioactive substances widely spread on ground surface, such as a method for scrapingly removing soil surface and a method for spraying treatment agent and solidifying soil for preventing the spread of the radioactive substances, produce a large amount of waste soils and, when reusing them, the radioactive substances are inevitably spread again, and that fall of the radioactive substances on the ground surface is affected by a wind direction and rainfall, and often produces a so-called hot spot where the radiodensity is specifically high.SOLUTION: When radioactive substances are widely spread and contaminate not only flat lands but also lands with elevation difference such as mountain forests and hills, the contaminants are washed using pressurized water including microscopic bubbles and wash water is treated by a rotary screen and a pressurized flotation unit.

Description

Detailed Description of the Invention

In the present invention, in order to remove the radioactive material diffused in a wide area, the pressure levitation technique and the property of pressurized water are used. In order to extract radioactive substances when they are chemically combined with soil particles or humus components, special substances such as collecting nanoparticles with fluidity, fine dispersion, and various reactivity that enter the microstructure are collected. Without functionality, radioactive materials in a stable state cannot be taken out.
In the present invention, by using pressurized water, (1) fine particles such as fine earth particles and organic matter adhering to the gas-liquid interface where the fine bubbles of pressurized water flow vigorously interact with the radioactive substance, and on the fine bubbles of pressurized water. Be captured.
(2) Pressurized water containing radioactive material flows down to a downstream basin or well in the form of turbid water. The water flowing down the contaminated area is pumped up from the catchment pond or well, further washed with pressurized water on the rotary screen, and pumped up into the reaction tank of the pressurized flotation device.
(3) In the reaction tank, a pH adjuster, a flocculant, a radiation adsorbent, a shielding agent, a heavy metal treatment agent, and the like are added depending on the water quality, and the properties are adjusted to facilitate handling and separation.
The radioactivity shielding agent measures the radioactivity level of the dehydrated isolate with a dosimeter and adjusts the result by controlling the additive feeder.
(4) The muddy water that has flowed from the reaction tank into the pressurized flotation tank is separated into a floating separation and treated water.
(5) The levitated matter is periodically scraped and flows into the screw conveyor and sent to the dehydration process for dehydration. Radioactive material is contained in this levitated dehydrated product in concentrated form.
(6) The treated water in the pressurized levitation tank is circulated as pressurized water in the pressurized levitation tank, but an amount corresponding to the inflow amount is again circulated to the cleaning site as pressurized water and used as cleaning water.

Technical field to which the invention belongs

The present invention relates to the removal of radioactive material diffused over a wide area on the ground surface.

The removal of contamination by the diffusion of radioactive materials is conventionally done by excavating and removing contaminated soil if it is soil, by sowing and collecting plants that absorb radioactive material in contaminated soil, and by structures such as roads. Cleaning was the main method. However, excavation and removal of soil is effective for small scales, but contamination due to large-scale diffusion is an unexpected method, and it is economically effective for land with differences in elevation such as forests, lakes, and hills other than flat land. It costs enormous expenses, and there are restrictions on the movement of heavy machinery, climbing ability, etc. In addition, a large amount of waste is generated, and in reality, conventional technology cannot cope with pollution that has spread over a wide area. .

Problems to be solved by the invention

(1) The present invention is a conventional method for removing radioactive materials diffused over a wide area on the surface of the earth, such as a method of scraping off the soil surface or spraying a treatment agent that solidifies soil for the purpose of preventing the radioactive materials from being dispersed. Then, it solves problems such as a large amount of waste soil coming out and re-dispersion of radioactive materials inevitably occur during reuse.
(2) Descent of radioactive material to the surface of the earth is affected by wind direction and rainfall, and so-called hot spots with a high radiation concentration may be created. Becomes difficult. Generally, civil engineering work is carried out based on accurate surveying, and there is a corresponding field survey period until the work starts, so if the intensity of radioactivity is high, the work itself becomes impossible.
The method of the present invention provides a method for solving these problems using pressurized water.

Means to solve the problem

In the present invention, when radioactive material diffuses over a wide area and the contamination contaminates not only flat land but also land with a height difference such as forests, hills, etc., it is washed with pressurized water containing fine bubbles, rotary screen, pressurized The washing water is treated by the levitation device to solve the problem.
(1) Install a pressurized levitation device in one section of the contaminated area, sprinkle part of the pressurized water into the contaminated area, or spray the pressurized water generated by the additional pressurized water generator newly installed in the sprinkled area into the contaminated area. .
(2) Utilize the difference in elevation of the watering area, and make a natural flow or pump up to guide the water to a natural lake or artificial pond or water tank in the lowland. If it is expected that there will be a lot of suspended matter in the running water, connect several ponds or tanks in series, and then pump the running water to the rotary screen.
(3) In the rotary screen, radioactive contaminants are effectively reduced by washing with pressurized water using a plurality of rotary screens. Floats such as washed dead leaves should be stored or returned to contaminated areas after dose confirmation.
(4) The treated water of the rotary screen becomes turbid water, but is introduced as it is to the reaction tank of the pressurized floatation apparatus. Here, pH, radiation dose, etc. are measured, and adjusted shielding agent, flocculant, and adsorbent are added. Alternatively, it is allowed to flow down to the pressure levitation tank without addition.
(5) In the pressurized flotation device, the turbid water containing the radioactive substance is separated, and the turbidity of the flowing water under the flotation material to be concentrated in the flotation material is reduced, and the radiation dose is also reduced.
(6) The levitated matter is automatically attracted to the skimmer, flows down to the screw conveyor, and is automatically conveyed to the dehydration site and dehydrated.
(7) The treated water that has been floated by pressure is pumped up again from the water tank to the cleaning site and reused.
(8) The decontamination operation is repeated until this process cycle is repeated until the amount of radioactive material from the cleaning site decreases.
In this process, the pressurized water used to clean the rotary screen enters the fine structure of the surface of the suspended matter that contains fine bubbles and attracts the attached contaminants to the gas-liquid interface and adheres to the gas-liquid interface. Floating substances in the soil combine with fine contaminants by the binding force of van der Waals forces to promote cleaning. This force also works on soil particles, and enters and cleans the micropores that are the fine structure of the soil particles.
The bubbles are collected in the pressurized levitation tank and become floating matter in the levitation tank, and are concentrated as the fine bubbles collapse. According to the present invention, the radioactive material can be removed from the contaminated site and put into a state where it can be isolated and stored.

The present invention will be described with reference to FIG. At a site contaminated with a wide range of radioactive materials with different elevations, one or more (4) rotary screens and (5) pressurized flotation devices are installed in the lowlands, and (8) pressurized water generated in the pressurized tank. Is sent to a spray device of pressurized water located at a high position in a partly contaminated site (cleaning site) and pressurized again or discharged as it is to the contaminated site below.
Since the sprayed pressurized water contains fine bubbles where the gas-liquid interface flows violently, it flows down while washing the fine structure such as plants. In addition to following the natural ditches, the flowing water flows down with the turbidity of fine particles adsorbed with radioactive materials while being guided by artificial excavation newly excavated. The sewage is drained by a pump after finally flowing down to an existing pond or an excavated catchment pond or well. (4) A large floating substance such as fallen leaves is separated by a rotary screen. By doing so, fine soil particles can be removed together with radioactive substances. The separated fallen leaves, etc. are returned to the washed site after falling into the separation receptacle. The treated water of the rotary screen is led to the reaction tank before the pressurized flotation tank. Depending on the properties, pH adjuster, flocculant, radioactive shielding agent (ore powder, iron salt, soil, zeolite, clay, etc.), adsorbent It is mixed with fine particles of (activated carbon, zeolite, clay, etc.) and guided to (5) a pressurized flotation tank. In the pressurized flotation tank, the fine particles containing the radioactive substance are floated under pressure and concentrated to the floated material. The levitated material is automatically scraped and applied to the dehydrator by the screw conveyor and discharged as a dehydrated cake. The treated water that has been subjected to pressurized flotation is free from radioactive substances and is reused through the circulation path of the pressurized flotation treated water. A part of the excess pressurized levitation treated water is discharged. This method can be easily applied to flat rice fields and fields. Figure 2 shows the schematic diagram. Pressurized water flows down the surface of the field, and adsorbs fine particles containing radioactive substances onto the fine bubbles and flows down. Subsequent processing and circulation are performed in the same manner as in FIG. As a result, the radioactive material is localized on the suspended matter, facilitating subsequent processing.

Effect of the invention

In the present invention, in the process of the flow sheet shown in FIG. 1, radioactive substances such as radioactive cesium are adsorbed on the surface of fine bubbles or fine particles adsorbed on the fine bubbles and floated and removed to obtain safe pressurized levitation treated water. The following effects can be obtained by circulating this at the cleaning site.
(1) A wide range of contaminated sites can be washed without destroying the local soil environment and vegetation.
(2) Place the radioactive materials under safe control by concentration by floating separation and localization by dehydration.
(3) Volume reduction of waste by dehydration of floating soil particles containing radioactive materials.
(4) Purification of sediment concentrated in environmental water and lake sediments that are in a radioactive state is also concentrated by dewatering by concentrating radioactive substances as floating materials by pumping the sediment and applying it to pressurized flotation equipment. Can be disposed of.
Specifically, (1) Decontamination of forests that have been difficult to decontaminate conventionally becomes possible. Also, decontamination work on flat land and fields is easy.
(2) In the construction method of the present invention, the amount of radioactive waste generated is extremely reduced as compared with the conventional method.
(3) In the present invention, since the system can be operated automatically, it is possible to reduce the danger of radiation exposure to a minimum, and workers are exposed to radiation more than necessary even in highly contaminated land. It can be decontaminated by continuous automatic operation.

Is a flow sheet when applied to the forest of the present invention.

(1) Installed near the hills and mountain peaks (2) Pressurized water discharge facility (3) Opened excavation to guide water to the target catchment pond or well (4) Rotary screen Remove dead leaves.
(5) Pressurized flotation tank Removes fine soil particles containing radioactive materials and other suspended matters.
▲ 6 ▼ Flotation tank Floating and floating storage tank ▲ 7 Treatment water tank Pressurized flotation water storage tank ▲ 8 Pressurization tank Pressurized water retention tank containing fine bubbles ▲ 9 Dehydrator Floating floss dewatering equipment ▲ 10 ▼ Circuit of pressurized flotation treatment water mixed with pressurized water ▲ 11 ▼ Radiation site of pressurized water Temporary work facilities, repressurization facilities, water discharge facilities, etc. are placed.

Claims (3)

(1) Pressurized water in which fine bubbles are dispersed in water or (2) nano-level with fine bubbles against soil, plants, river water, lake water, and artifacts (houses, roads, etc.) contaminated by radioactive material fall Mixing and washing using pressurized water in which natural fine soil particles, clay particles or artificial fine suspended matters are dispersed. Applying radioactive substances attached to the surface of soil particles, plants, river water, lake water, and man-made materials to the surface of fine bubbles, the surface of fine particles, and the surface of fine suspended solids combined with fine bubbles Separated from the kimono, separated, adsorbed on the microbubbles side of the pressurized water, guided to the pressurized flotation facility together with the radioactive substance as turbid water, floated and separated, and the pressurized substance floated with the radioactive substance that is the source of contamination attached to the fine particles A method of localizing radioactive substances dispersed over a wide area by levitating and concentrating on the tank surface, obtaining treated water with reduced radioactive substances, and circulating it again at the washing site. A pH adjuster, an inorganic flocculant (sulfuric acid band, PAC, iron chloride, polyiron, etc.), a polymer flocculant, and a radioactive material shielding agent (soil particles) , Viscosity particles, zeolite, activated carbon, etc.), a reaction vessel that adds and mixes a heavy metal treatment agent, etc., and moves the suspended matter concentrated on the surface of the pressurized flotation vessel using transport means such as skimmers and conveyors for dehydration To localize and concentrate radioactive materials Shielding agent (ore powder) that feeds back and separates the radioactivity level of the dehydrated separation into the dosimeter installed in the reaction tank when the suspended matter separated in claim 2 and the levitated matter extracted from the levitation vessel are dehydrated and separated. , Soil particles, clay particles, etc.)

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