KR20220122819A - Method and System for Decontamination of Contaminated Soil - Google Patents

Abstract

The present invention relates to a decontamination method and a decontamination system for soil contaminated with radioactive substances released into the environment due to the operation and accident of a nuclear power plant, wherein radioactive waste can be minimized by separating and treating contaminated soil into fine soil that is mainly combined with radioactive materials and contaminated soil of a larger particle size, a decontamination process and a decontamination system are simplified so that decontamination work can be carried out continuously, quickly and efficiently at a contaminated site, secondary water treatment is unnecessary due to non-use of acid or alkaline agents, and water quality of washing wastewater is high to enable recycling.

Description

Method and System for Decontamination of Contaminated Soil

The present invention relates to a method and a decontamination system for decontamination of contaminated soil contaminated with radioactive material emitted to the environment due to operation and accident of a nuclear power plant. radioactive waste can be minimized by treating with It relates to a radioactive contaminated soil decontamination method and decontamination system that can be recycled because of the high quality of washing wastewater.

The radioactive material released into the environment due to the accident at the Fukushima Daiichi Nuclear Power Plant in Japan caused by the natural disaster on March 11, 2011 directly or indirectly affects the surface and oceans of northeastern Japan as well as neighboring countries. The development of various decontamination technologies for the restoration of contaminated soil, forests, roads, and rivers, and decontamination activities for the removal of pollutants are continuing.

Meanwhile, in the case of domestic nuclear power plants, Kori No. 1 and other nuclear power plants that reach the end of their lifespan by 2030 are scheduled to be dismantled sequentially. After the nuclear power plant is dismantled, site restoration work is finally carried out, and the contaminated soil is decontaminated to reduce the generation of contaminated soil. Currently, the development of various dismantling and decontamination technologies required for dismantling is being promoted under the leadership of the state.

Since a small amount of gaseous radioactive material is released into the environment even during operation of nuclear power plants, the possibility of contamination of the surrounding soil and forest is high. In Korea, there is a silo-type repository that can treat 100,000 drums of low- and medium-level waste, and an additional landfill repository with a disposal capacity of about 350,000 drums is planned. Since the disposal cost per 200L drum is expensive, about 15 million won, decontamination and reduction technologies are being developed for various wastes including contaminated soil and concrete in order to reduce disposal costs.

Environmental pollution by these radioactive materials occurs due to unplanned leakage, and a significant amount of radioactive material leaked into the environment is ionized by moisture in the soil and spreads to the surface or the lower part of the soil. , can be contaminated over a wide range, including water in oceans and lakes. In particular, ionic cesium (Cs+) released into the atmosphere meets with rainwater or snow and migrates to the water, and by rainfall, it infiltrates the soil and groundwater around the nuclear power plant and pollutes the surrounding environment.

Although various nuclides exist in radioactive contaminated soil, cesium (Cs), which has good adsorption properties to the soil, is not easily removed and is strongly adsorbed to the clay minerals in the soil and stays for a long time. Only minerals are separated and treated. In general, cesium (Cs) moves to a depth of about 5 cm (10 cm depending on the soil type) of the soil and is adsorbed to the clay minerals in the soil. is difficult In addition, radioactive strontium (Sr) and radioactive cobalt (Co), which have long half-lives, have different adsorption and desorption patterns in the soil, but have similar patterns of adsorption to fine soil like general heavy metals.

As a general method of purifying contaminated soil, there are various methods such as solidification/stabilization, landfill, soil loam, plant purification, and soil washing. Among them, the soil washing method is known as the most economical and technologically stable method. Soil washing uses water or detergent to weaken the surface tension of contaminants bound to soil particles or to increase solubility of heavy metals and elute them to separate contaminants from soil particles.

In particular, many studies are being conducted on decontamination treatment of soil contaminated with cesium (Cs) due to the Fukushima nuclear accident. As a method to replace the existing wet washing method, a method of extracting cesium (Cs) from contaminated soil and adsorbing it with blue blue or zeolite to separate it, and a method of removing cesium (Cs) using an adsorbent bound with a magnetic material are proposed. have. These methods require a post-processing process, resulting in secondary waste. A method of separating the magnetic material of the soil by superconducting technology has also been proposed, but this method is difficult to apply because of its small adsorption amount when targeting a large volume.

Patent No. 10-1652811 (Radioactive Contamination Soil Decontamination System) technology is a step of decontamination of radioactively contaminated soil by separating soil and organic matter through a mesh and an air blower and spraying high pressure water to the soil that has passed through the mesh. After classifying the particle size and reclassifying it by applying a hydrocyclone, the soil classified as having a small particle size is aggregated and precipitated, the sediment is dehydrated and treated as waste, and the dehydrated filtrate is reused as washing water or discharged to the environment through a filtration process, and pollution; There is a difference in physically exfoliating the fine soil containing radionuclides from the original soil using a fan-shaped ball joint nozzle to exfoliate the material, and using a coagulant specialized for sedimentation in the separated fine soil.

Patent No. 10-1612403 (Prussian blue-supported nanofiber complex for adsorption of radioactive cesium, filter media and radioactive cesium decontamination method using the same) technology uses a Prussian blue and Prussian blue-type metal complex-supported nanofiber complex. Although it adsorbs and removes cesium (Cs) in radioactive waste or water, the efficiency of removal of nuclides such as cobalt (Co) and strontium (Sr) is not verified, so additional verification is required.

Japanese Patent No. 6516317 (Decontamination method and decontamination apparatus for soil contaminated with radioactive cesium) technology uses a treatment solution composed of water and phosphate in a reaction tank to stir contaminated soil contaminated with radioactive materials at a pH of 4 or less. The radioactive material is separated from the soil into a treatment solution by treatment at 80-100°C for 1-5 hours. The separated treatment liquid is additionally reacted with an adsorbent such as Prussian Blue to remove radioactive contaminants.

Patent No. 10-1375482 (High-concentration polluted soil purification system and purification method that combines continuous high-level selection step-by-step and differential heavy metal removal process by polluting load) is a system and As a method, in the pre-treatment unit, contaminated soil with a specific concentration or higher is mixed with water to be powdered, and after removing foreign substances, the soil with a certain particle size or larger is separated into purified soil, and contaminated soil with a smaller particle size is selected, and then, through a purification device, After washing with washing water, purified soil and washing water are separated through a filter, and the washing water is neutralized in a neutralization tank and discharged, and acid and alkali are added. This technology is mainly optimized for heavy metal removal and chemical behavior is similar to that of radioactive materials, but the removal efficiency of radioactive contaminants has not been reviewed.

Patent No. 10-1068523 (a method of removing cobalt and cesium from radioactive waste) technology is a process for removing cobalt (Co) and cesium (Cs) from contaminated waste fluid through a step-by-step rapid stirring process, and non-radioactive cobalt is added to radioactive waste fluid. After adding the salt, it is stirred rapidly, and then potassium ferrocyanide is added and stirred rapidly, and after adding an alkali solution, the cobalt (nuclide component, cobalt) ( It is a technology to remove Co) and cesium (Cs) with high efficiency, and it is focused on the process of removing radionuclides from radioactive waste. do.

The conventional method and apparatus for decontamination of contaminated soil as described above do not have a significant effect on reducing radioactive waste, and require a lot of investment in facilities because of complex processes and facilities such as soil washing, chemical cleaning, and water treatment, and take up a lot of space as well as pollution. There are disadvantages in that decontamination work cannot be carried out quickly on site, and waste liquid increases due to the use of acid or alkali agents, and secondary water treatment is required.

KR 10-1652811 B KR 10-1612403 B JP, P-6516317, B KR 10-1375482 B KR 10-1068523 B

In order to solve the above disadvantages of the prior art, the present invention can minimize radioactive waste, and the decontamination process and decontamination system are simplified, so that decontamination work can be performed continuously quickly and efficiently at the contaminated site, and the amount of waste is increased. The purpose of the present invention is to provide a decontamination method and decontamination system for radioactive contaminated soil that does not require secondary water treatment.

The radioactive contaminated soil decontamination method of the present invention includes a contaminated soil input process of injecting contaminated soil into a decontamination system, a high-pressure washing process of breaking the aggregate structure by high-pressure washing of the contaminated soil input to the decontamination system and separating coarse gravel and impurities; A fractionation process by particle size of fractionating the contaminated soil that has undergone the high-pressure washing process for each particle size by high-pressure washing and a vibrating dehydration screen, and the turbid solution that has undergone the fractionation process by particle size is fractionated into a fine soil turbid solution and an ultra-fine turbidity solution according to the particle size a hydrocyclone process, a coagulation precipitation process of coagulating and precipitating the turbidity that has undergone the hydrocyclone process to separate solid-liquid and removing radioactive materials in the turbid solution, and a microscopic process for removing moisture from the sludge precipitated by solid-liquid separation in the coagulation precipitation process It includes a drying and solidification process of drying the dewatered sludge dewatered through the total dewatering process and the micrototal dewatering process, shielding, isolating, and fixing the dewatered sludge.

On the other hand, the radioactive contaminated soil decontamination system of the present invention is a drum screen separator for washing contaminated soil and separating gravel and contaminants with a particle diameter of 25 mm or more, and a first high pressure washing device installed above the entrance of the drum screen separator , a first vibrating dewatering screen installed under the drum screen sorter to separate washing soil with a particle diameter of 5 mm or more, a second high-pressure washing device installed on the first vibrating dewatering screen, and installed under the first vibrating dewatering screen A second vibrating dehydration screen that separates washing soil with a particle diameter of 2 mm or more, a third high-pressure washing device installed on the second vibrating dewatering screen, and a turbidity passing through the second vibrating dewatering screen installed under the second vibrating dewatering screen A first storage tank for storing a liquid, a first hydrocyclone connected to the first storage tank by a pipe to separate the turbid solution into upper and lower parts according to the particle size thereof, installed under the first hydrocyclone and the first hydrocyclone A third vibrating dehydration screen that separates washing soil with a particle diameter of 0.2 mm or more among the turbid liquid discharged to the lower part of the A second storage tank for storing the turbid liquid that has passed through the third vibrating dewatering screen, a second hydrocyclone connected to the second storage tank by a pipe to separate the turbid liquid in the second storage tank into upper and lower parts according to the particle diameter, the above A flow control tank that is connected to the upper part of the first and second hydrocyclones by a pipe and stores the turbid solution discharged to the upper part of the first and second hydrocyclones, and is connected to the second hydrocyclone by a pipe. An underflow storage tank for storing the turbid liquid discharged to the lower part of the second hydrocyclone, an overflow storage tank for storing the turbid liquid flowing out from the flow control tank by being connected to the flow control tank by a pipe, and the underflow storage tank and the pipe connected to A fine earth flocculation precipitation tank that receives and coagulates the turbid liquid stored in the underflow storage tank, is connected to the overflow storage tank and a pipe, and is stored in the overflow storage tank A very fine soil coagulation and precipitation tank for receiving and flocculating and precipitating the turbidity in progress, a dehydrator for removing moisture from the sludge that is connected to the fine earth coagulation and precipitation tank and the micro fine soil coagulation and precipitation tank and settling in the fine earth coagulation and precipitation tank and the ultrafine soil coagulation and precipitation tank; and a sludge drying device for drying the sludge from which moisture has been removed by the dehydrator.

The present invention can minimize radioactive waste by separating and treating contaminated soil into fine soil to which radioactive materials are mainly bound and contaminated soil with a particle size larger than that, and the decontamination process and decontamination system are simplified to continuously and rapidly and efficiently at the contaminated site. Decontamination work can be done, and the treated clean soil can be immediately backfilled on site or recycled for other purposes. In addition, since the present invention does not use an acid or alkali agent, the waste liquid does not increase and secondary water treatment is not required, and the water quality of the washing wastewater is high, so that it can be recycled.

In addition, in the present invention, the contaminated soil is not limited to a specific contaminated soil, and the radioactive material is also not limited to a specific nuclide, cesium (Cs), strontium (Sr), barium (Ba), cobalt (Co), uranium (U), etc. It has the effect of being able to target various radioactive materials.

1 is a schematic diagram of a radioactive contaminated soil decontamination method of the present invention. Figure 2 is a detailed view of the radioactive contaminated soil decontamination method of the present invention. 3 is a schematic diagram of the radioactive contaminated soil decontamination system of the present invention. 4 is a detailed view of the drum screen sorter of the present invention. 5 is an explanatory diagram of the action of the hydrocyclone of the present invention. 6 is an exemplary view of the vibrating dehydration screen of the present invention. 7 is a graph of the overflow particle size characteristics after the hydrocyclone process of the present invention. 8 is an underflow particle size characteristic graph after the hydrocyclone process of the present invention. 9 is a turbidity graph for each coagulant before and after the coagulant precipitation process in Examples of the present invention; 10 is a cobalt concentration graph of the supernatant for each coagulant after the coagulant precipitation process in Examples of the present invention. 11 is a graph showing the correlation between the turbidity of the wash water and the concentration of cobalt in the example of the present invention. 12 is a graph showing the concentration of radioactive cesium before and after the coagulation precipitation process in Example of the present invention.

Hereinafter, the present invention will be described in detail based on the accompanying drawings.

In the radioactive contaminated soil decontamination method of the present invention, as shown in FIGS. 1 and 2 , the contaminated soil input process (S10) of introducing the contaminated soil into the decontamination system, and the high-pressure washing of the contaminated soil injected into the decontamination system. High-pressure washing process (S20) of crushing and separating coarse gravel and impurities The hydrocyclone process (S40) of fractionating the turbidity that has undergone the fractionation process (S30) into a fine earth turbid solution and a very fine turbidity solution according to the particle size, and the hydrocyclone process (S40). and a coagulation precipitation process (S50) for removing radioactive substances in the turbid solution, a micrototal dewatering process (S60) and the micrototal dewatering process ( It includes a drying and solidification step (S70) of drying the dewatered sludge dewatered through S60), shielding, isolating, and fixing the dewatered sludge.

On the other hand, the radioactive contaminated soil decontamination system of the present invention, as shown in FIG. 2, a drum screen separator 204 that washes contaminated soil and separates gravel and contaminants with a particle diameter of 25 mm or more, and the drum screen separator 204. A first high-pressure washing device 201 installed above the inlet, a first vibrating dewatering screen 205 installed below the drum screen sorter 204 to separate washing soil with a particle diameter of 5 mm or more, the first vibrating dewatering screen ( 205) a second high-pressure washing device 202 installed above, a second vibrating dewatering screen 206 installed below the first vibrating dewatering screen 205 to separate washing soil having a particle diameter of 2 mm or more, and the second vibrating dewatering A third high-pressure washing device 203 installed on the screen 206 and a first storage tank installed below the second vibrating dewatering screen 206 to store the turbid liquid that has passed through the second vibrating dewatering screen 206 (210), the first hydrocyclone 301, which is connected to the first storage tank 210 by a pipe to separate the turbid solution into upper and lower parts according to the particle size, and is installed under the first hydrocyclone 301 A third vibrating dewatering screen 304 that separates washing soil with a particle diameter of 0.2 mm or more from the turbid solution discharged to the lower part of the first hydrocyclone 301, and a fourth high-pressure washing installed on the third vibrating dewatering screen 304 Device 303, a second storage tank 307 installed under the third vibrating dewatering screen 304 to store the turbid liquid that has passed through the third vibrating dewatering screen 304, and the second storage tank 307 A second hydrocyclone 302, the first hydrocyclone 301, and a second hydrocyclone 302 that are connected to a pipe to separate the turbid solution of the second storage tank 307 into upper and lower parts according to the particle size thereof. The flow rate adjustment tank 308 for storing the turbid liquid discharged to the upper part of the first hydrocyclone 301 and the second hydrocyclone 302 connected by a pipe to the upper part of the, and the second hydrocyclone 302 through a pipe Underflow storage connected to store the turbid solution discharged to the lower part of the second hydrocyclone 302 The tank 309, the flow control tank 308 and the pipe connected to the overflow storage tank 310 for storing the turbid liquid overflowing from the flow control tank 308, and the underflow storage tank 309 and the pipe connected to the The fine earth coagulation and precipitation tank 404 for receiving and coagulating and precipitating the turbid solution stored in the underflow storage tank 309, the turbidity solution stored in the overflow storage tank 310 and connected to the overflow storage tank 310 through a pipe The ultrafine earth coagulation and sedimentation tank 407, the fine soil coagulation and sedimentation tank 404, and the ultrafine soil coagulation and sedimentation tank 407 are connected to the pipe and the fine soil coagulation and sedimentation tank 404 and the ultrafine soil coagulation and sedimentation tank 407. It includes a dehydrator 501 for removing moisture from the sludge deposited in the sludge dryer 501 and a sludge drying device 702 for drying the sludge from which moisture has been removed by the dehydrator 501 .

In addition, in the radioactive contaminated soil decontamination system of the present invention, a washing water tank 101 for storing contaminated soil washing water, a hopper 105 for storing contaminated soil, and the drum screen separator 204 from the hopper 105 are used. The inclined conveyor belt 110 for transporting contaminated soil, the first discharge conveyor belt 208 connected to the outlet of the first vibrating dewatering screen 205 to discharge the first washing soil, the second vibrating dewatering screen ( A second discharge conveyor belt 209 connected to the outlet of 206 to discharge the second washing soil, and a third discharge conveyor belt connected to the outlet of the third vibrating dewatering screen 304 to discharge the third washing soil ( 305), the fine soil flocculation and sedimentation tank 404, the ultrafine soil flocculation and sedimentation tank 407 and the dehydrator 501 are connected to a pipe to store the supernatant and dewatering filtrate separated from the sedimentation turbidity solution 601, radioactivity Required devices or devices such as a measuring device 703, a zeta potential measuring device 408, pressure and flow sensors 103, 104, 602, and water supply and distribution pumps 102, 109, 409 and 603 may be added.

In the contaminated soil input process (S10) of the present invention, the amount of contaminated soil to be decontaminated is measured by measuring the radioactivity level of the contaminated soil collected from the surface layer of approximately 5 to 10 cm contaminated with radioactive material with a radioactivity measuring instrument 703 and compared with a preset standard. It is determined that the amount of contaminated soil is collected and put into the decontamination system. The collected contaminated soil can be directly put into the drum screen sorter 204 of the decontamination system by manpower or equipment, but the collected contaminated soil is stored in a hopper 105 as a ton bag and then inclined conveyor It is preferable to put the belt 110 into the drum screen sorter 204 . It is calculated by measuring the initial radioactivity concentration using the radioactivity meter 703 or converting the radioactivity concentration of the sample by the surface dose rate of the hopper 105 using a high purity germanium (HPGe) semiconductor detector or NaI scintillation meter. When measuring from the outside, it is desirable to formulate the correlation coefficient between the surface dose rate and the radioactivity concentration of the sample in advance so that it can be estimated only with the dose rate.

In the high-pressure washing process (S20) of the present invention, the contaminated soil injected into the drum screen sorter 204 of the decontamination system in the contaminated soil input process (S10) is crushed by high-pressure washing to break the aggregate structure, and coarse gravel and impurities are separated. At the moment the contaminated soil is put into the drum screen sorter 204, high-pressure washing water is sprayed from the nozzle of the first high-pressure washing device 201 installed above the inlet of the drum screen sorter 204, so that there is a strong relationship between the washing water and the contaminated soil. A collision occurs. By the impact of such a strong current, the radioactive material attached to the surface of the solids (pebbles, sand, silty soil, fine soil) in the contaminated soil is desorbed. In this way, the washing water and the contaminated soil strongly collide with each other and enter the drum screen separator 204, and as the drum screen separator 204 rotates, the collision between the washing water and the contaminated soil and washing of the contaminated soil are continued.

In this high-pressure washing process (S20), after the mixture of contaminated soil and washing water enters the drum screen separator 204, as the drum screen separator 204 rotates, the cleaning of the contaminated soil continues due to the collision of the contaminated soil and the washing water. Gravel and contaminants having a particle diameter of 25 mm or more are discharged through the first outlet 2041 and separated, and most of the gravel and contaminants discharged in this way are desorbed from radioactive materials and can be used as regenerated aggregate. On the other hand, gravel, soil, and washing water having a particle diameter of less than 25 mm, passing through the second outlet 2042 composed of a 25 mm screen screen, is installed on the lower part of the drum screen sorter 204 and 5 mm above the first vibration dehydration screen 205. falls off

When tree branches, debris, large stones or gravel are included, a trommel sorter is usually used to dryly separate them, but it is efficient in fractionating relatively large stones or lumps, and large stones with a particle diameter of 25 mm or more It is not suitable for removing fine soil attached to gravel, etc.

Therefore, in the present invention, as shown in FIG. 4, the structure of the trommel sorter is modified to a drum screen method, and a first outlet 2041 through which contaminants with a particle diameter of 25 mm or more can be discharged at the rear end of the drum, and the middle A second outlet 2042 composed of a 25mm screen for the eyes is formed in the part, and the remaining part is closed.

In addition, a plurality of retention jaws 2043 are formed along the inner circumferential surface of the drum to increase the cleaning effect by increasing the collision, disturbance, and residence time between soil with a large particle diameter, soil with a small particle size, and washing water. It is preferable to form several such retention jaws 2043 at regular intervals so that the residence time of the washing water and the contaminated soil is maintained at a constant height and the residence time for the reaction of the washing water and the contaminated soil is increased and moved forward slowly by setting the height of 5 to 15 cm for efficient disturbance of the water flow. do. In addition, the disturbance of the water flow may be further promoted by drilling a plurality of through-holes 2044 in the retention jaw 2043 . The installation angle of the drum screen sorter 204 is selected differently depending on the amount of treatment, the treatment efficiency, and the movement speed of the contaminated soil, but about 10 to 20 degrees is preferable.

In the fractionation process by particle size (S30) of the present invention, the contaminated soil that has undergone the high-pressure washing process (S20) is fractionated by particle size by high-pressure washing and a vibrating dehydration screen. In the high-pressure washing process (S20), the gravel, soil and washing water having a particle diameter of less than 25 mm that passed through the second outlet 2042 of the drum screen sorter 204 fell onto the first vibration dehydration screen 205 of 5 mm of the eyes and the first vibration The second high-pressure washing is additionally performed by the washing water sprayed from the second high-pressure washing device 202 installed thereon while moving toward the outlet with the vibration of the dewatering screen 205, and the soil with a particle diameter of 5 mm or more is subjected to the first vibrating dewatering screen. As the vibration of 205 moves the water to the outlet (after it is transported by the first discharge conveyor belt 208), it is discharged to the first washing soil S31a.

On the other hand, the soil and washing water having a particle diameter of less than 5 mm, passing through the first vibrating dehydration screen 205, falls onto the second vibrating dewatering screen 206 of 2 mm around the eyes and moves toward the outlet due to the vibration of the second vibrating dewatering screen 206. The third high-pressure washing is performed by the washing water sprayed from the third high-pressure washing device 203 installed on the upper part, and the soil with a particle diameter of 2 mm or more is moved to the outlet while moisture is drained by the vibration of the second vibrating dewatering screen 206 ( After being transported by the second discharge conveyor belt 209), it is discharged to the second washing soil S32a. Meanwhile, the turbid liquid having a particle diameter of less than 2 mm that has passed through the second vibrating dehydration screen 206 is stored in the first storage tank 210 .

In the hydrocyclone process (S40) of the present invention, the turbid solution that has passed through the fractionation step (S30) by particle size is fractionated into a fine earth turbid solution and an ultra-fine turbid solution according to the particle size. After the first sand pump 211 is operated and the particle size fractionation process S30 is performed, the turbid solution having a particle diameter of less than 2 mm stored in the first storage tank 210 is transferred to the first hydrocyclone 301 . The turbid solution transferred to the first hydrocyclone 301 in this way is divided into upper and lower portions according to its specific gravity and discharged. The turbid liquid having a particle diameter of less than 0.05 mm discharged to the upper portion is discharged to the overflow storage tank 310 through the flow rate adjustment tank 308 and overflows.

On the other hand, the turbid liquid discharged to the lower part of the first hydrocyclone 301 and falling onto the third vibrating dehydration screen 304 of 0.2 mm around the eye is installed on the upper part while moving toward the outlet due to the vibration of the third vibrating dehydration screen 304. The fourth high-pressure washing is performed by the washing water sprayed from the fourth high-pressure washing device 303, and the soil with a particle diameter of 0.2 mm or more is moved to the outlet while moisture is drained by the vibration of the third vibrating dewatering screen 304 (the third After being transported by the discharge conveyor belt 305), it is discharged to the third washing soil (S41a). Meanwhile, the turbid liquid having a particle diameter of less than 0.2 mm that has passed through the third vibrating dewatering screen 304 falls into the lower second storage tank 307 and is then transferred to the second hydrocyclone 302 by the second sand pump 306 . do.

Among the turbid liquid transferred to the second hydrocyclone 302 in this way, the turbid liquid having a particle diameter of less than 0.05 mm discharged to the upper portion of the second hydrocyclone 302 passes through the flow rate adjustment tank 308 and overflows the overflow storage tank 310 ) is released as However, the turbid liquid having a particle diameter of less than 0.05 m to 0.2 mm discharged to the lower portion of the second hydrocyclone 302 is discharged to the underflow storage tank 309 .

The hydrocyclone is a conical container, and has an inlet, an upper outlet, and a lower outlet through which the turbid solution is introduced, and generates an upflow and a downflow by centrifugal force to transform the turbidity into suspended particles. and the fluid are separated according to the difference in specific gravity. The treatment performance, pressure loss, removal particle size, and treatment flow rate vary depending on the shape of the inlet, the diameter of the cylindrical portion and the diameter of the lower outlet. The higher the inlet pressure, the more effective separation is achieved. In addition, when the particles are large or the difference in density between the fluids is large, the separation efficiency is high, but when the fine particles or the difference in density is small, the separation efficiency is low.

As such, in the hydrocyclone process (S40), the turbid solution containing fine soil is introduced into the conical container, and in the process of generating a vortex and turning it along the inner wall of the container, the turbid solution containing coarse soil is recovered to the bottom, and specific gravity These light particles are discharged to the upper outlet by an upward flow generated in the central part of the hydrocyclone. In the hydrocyclone process (S40) of the present invention, the fractionation performance was improved by changing the pressure of the inlet and the diameter of the lower part of the cone in order to achieve fractionation with a particle diameter of less than 0.05 mm (50 μm). If an inverter is installed in the first sand pump 211 and the discharge performance is variably controlled in the range of 40 to 80%, it is possible to fractionate to a desired particle size.

The following Table 1 is an example of the particle size distribution of the overflow turbidity solution that has gone through the hydrocyclone process (S40) with artificial cobalt (Co) contaminated soil, and 0.05mm (50) when the first hydrocyclone 301 and the second hydrocyclone 302 are passed. It can be seen that most of the fine particles of less than ㎛).

Particle size distribution of hydrocyclone overflow turbidity of artificial cobalt-contaminated soil Distribution Table Size Range Fraction (% of total) 54.643 ?? 29.0939 0.0 29.0939 ?? 15.4907 47.03 15.4907 ?? 8.2478 3.47 8.2478 ?? 4.3914 4.28 4.3914 ?? 2.3382 10.98 2.3382 ?? 1.2449 13.9 1.2449 ?? 0.6628 9.79 0.6628 ?? 0.3529 4.94 0.3529 ?? 0.1879 3.27 0.1879 ?? 0.1001 2.34 Total Weight: 12,971.05 MicrogramsWeight Mean: 4.8493

The high-pressure washing devices 201, 202, 203, and 303 used in each process are composed of an inlet of contaminated soil, a plurality of injection nozzles and a washing water transfer pipe connected thereto. can be raised As a material of such a cleaning device, iron or stainless steel is usually used, but abrasion-resistant materials such as ceramics may be used.

These high-pressure washing devices (201, 202, 203, 303) use a high-pressure injection nozzle having a discharge pressure in the range of 2 to 10 MPa, and the injection flow rate, injection pressure, and injection direction can be freely adjusted. In addition, it is possible to increase the contact area with the soil by arranging several spray nozzles in a fan shape rather than arranging them in a single direction.

In addition, when the high-pressure water sprayed from these high-pressure washing devices (201, 202, 203, 303) is sprayed obliquely in the opposite direction to the flow of the soil moving by the vibration of the vibrating dewatering screens (205, 206, 304), the fine particles attached to the soil of large particle size are removed. It can be desorbed more effectively, so that fine particles containing a lot of radioactive material can be desorbed more easily.

In the coagulation precipitation process (S50) of the present invention, the turbidity that has undergone the hydrocyclone process (S40) is coagulated and precipitated to separate solid and liquid, and radioactive materials in the turbid solution are removed. In the hydrocyclone process (S40), the turbid solution having a particle diameter of 0.05 m to less than 0.2 mm stored in the underflow storage tank 309 is moved to the fine earth flocculation and precipitation tank 404 for flocculation and precipitation, and the particle diameter stored in the overflow storage tank 310 The turbid solution of less than 0.05 m is moved to the ultra-fine sedimentation tank 407 for coagulation and precipitation to separate solid-liquid.

In the turbid solution that has undergone the hydrocyclone process (S40), fine particles or colloidal particles coexist to generate a zeta potential. An appropriate coagulant is selected according to the zeta potential of the turbid solution having a particle diameter of less than 0.05 m to 0.2 mm and the turbid solution having a particle diameter of less than 0.05 m to efficiently remove radioactive materials from the turbid solution.

The fine soil coagulation and sedimentation tank 404 and the ultrafine soil coagulation and sedimentation tank 407 include a stirrer (M) for stirring the turbid solution inside, a zeta potentiometer (403,408) for measuring the zeta potential of the turbid solution, and the zeta potentiometer (403,408) ), the coagulant automatic injectors 405 and 406 for automatically injecting the coagulant according to the measured value are installed. The characteristics of the incoming turbidity depend on the soil of the original soil, and by measuring the zeta potential of the incoming turbidity in real time, the amount of coagulant injected from the initial zeta potential to the point of neutralization (0mV) is automatically determined. Inject coagulant.

In this coagulation and precipitation process (S50), when the coagulant is put into a turbid solution containing colloidal particles, the negatively charged ions of the colloidal particles and the positively charged ions of the coagulant are combined to aggregate the colloidal particles. For coagulation of such a turbid solution, it is usually used as a coagulant by combining at least one of magnesium chloride, aluminum sulfate, and calcium chloride with an inorganic coagulant and a polymer coagulant. In addition, polyelectrolyte ions may be added to the turbid solution to improve the treatment effect of the inorganic coagulant and the polymer coagulant.

As the inorganic coagulant, aluminum-based coagulants such as PAC and aluminum sulfate, iron coagulants such as ferric chloride and ferric sulfate can be used, and as the polymer coagulant, polyacrylamide or polyacrylic acid ester coagulants can be used. . Both emulsion-type and powder-type coagulants can be used. As a result of using a natural inorganic polymer coagulant that exhibits the best performance by comprehensively evaluating the pH change according to the use of various coagulants, the goodness of the lower precipitated floc, and the turbidity, the coagulant precipitation effect of co-precipitating most contaminants was shown.

9 is a graph showing the change in turbidity of each coagulant before and after the coagulation precipitation process in the example of the present invention. In the case of a powder-type natural polymer coagulant among commercially available coagulants, the turbidity of the supernatant after the coagulation precipitation process is within 5 NTU compared to other coagulants. The water quality was good. It is considered that the fine colloidal particles causing turbidity were settled by aggregation reaction. The level of radioactivity is measured using a germanium semiconductor detector, an automatic gamma spectrometer, a NaI scintillation detector, etc., which is a radioactivity measuring instrument 703, for the supernatant where solid-liquid separation has been completed through this coagulation precipitation process (S50). Supernatant water whose measured radioactivity level is below the standard value is discharged to the outside, but some of it can be recycled as washing water.

In the micrototal dewatering process (S60) of the present invention, moisture is removed from the sludge precipitated by solid-liquid separation in the coagulation and sedimentation process (S60) with a dehydrator 501 . A belt press dehydrator, a filter press dehydrator, a screw decanter dehydrator, a centrifugal dehydrator, etc. can be used as dehydrators for removing moisture from the sludge.

However, in the case of a belt press dehydrator or a filter press dehydrator, the amount of recovered filtrate and coagulant is increased due to the manual method, maintenance problems such as clogging of the filter press, worker exposure problems due to maintenance, and an increase in the amount of filtrate discarded after use There are disadvantages such as increased cost.

In consideration of this point, in the present invention, fine dewatered sludge (S62) and ultrafine dewatered sludge (S63) containing particulates containing radioactive material coagulated in a coagulation tank are transferred using a continuous-type screw decanter centrifuge. while continuously dehydrating. As a result, the risk of exposure is reduced because there is less access by workers, and it can be processed at a relatively high speed. In this micrototal dewatering process (S60), the moisture content of the fine dewatered sludge (S62) and the ultrafine dewatered sludge (S63) is 30 to 40%, respectively, after measuring the radioactivity level, the drying and solidification process (S70) is performed.

In the drying and solidification process (S70) of the present invention, after measuring the radioactivity level with the radioactivity meter 703 for the dewatered sludge that has undergone the fine total dewatering process (S70) as above, it is dried in the sludge drying device 702, and then the solidifying agent By mixing the remaining radioactive material (Solidification) to improve the strength of the solidified body. After that, in terms of structural stability of the solidified material, tests are performed on compressive strength, solidification degree, etc. to determine whether it is suitable for final disposal. Fine soil with a particle diameter of 0.2 to 0.05 mm solidified in this way is mixed with sand and used for civil engineering or industrial use if the degree of radioactive contamination is insignificant. On the other hand, despite such solidification treatment, fine soil with a particle diameter of 0.2 to 0.05 mm and ultra-fine soil with a particle diameter of less than 0.05 mm containing a high concentration of radioactivity are treated as low-level waste.

The supernatant water separated from the turbidity in the coagulation and precipitation process (S60), the dehydration filtrate from the precipitation turbidity, and the dehydration filtrate separated in the micrototal dewatering process (S70) are stored in the washing wastewater tank (601). The radioactivity level of such washing wastewater can be measured with a high-purity gamma spectrum, automatic gamma spectrometer, NaI scintillation detector, etc., and can be discharged if it meets the standards for river water discharge. In addition, if necessary, the washing wastewater can be passed through a bag filter or MF membrane, or radioactive substances contained therein can be removed through electrochemical treatment. However, in the present invention, such washing wastewater can be reused as washing water, thereby eliminating the need for complicated and expensive treatment.

After fractionating the contaminated soil by particle size through the high-pressure washing process (S20), the particle size fractionation process (S30), the hydrocyclone process (S40) and the micrototal dewatering process (S60), the radioactivity level is measured, respectively, and the purification efficiency to judge In each of these processes, the separated particles have a lower radioactivity level, but if the radioactivity level is higher than the reference value, the previous process is returned. That is, if the radioactivity level is measured for each of the gravel, the first wash soil, the second wash soil, the third wash soil, the micro-dehydrated sludge and the ultra-fine dehydrated sludge discharged from each process, and is higher than the standard value, the previous process return to

In this example, 100 kg of artificial contaminated soil (Co) made by mixing 95 kg of non-contaminated commercial Masato with 100 mg/kg 5.0 kg of cobalt (Co) having a particle diameter of less than 0.25 mm, which was dry sieved, was put into the high-pressure washing process (S20). . The ratio of water to soil was maintained at about 1:15, and soils with particle diameters of 25mm, 5mm, 2mm, and 0.2mm or more were prepared by sieving through a vibrating sieve for each particle diameter.

Figure 9 shows the change in turbidity for each coagulant before and after the coagulation precipitation process (S50). 10 shows the cobalt (Co) concentration of the supernatant water for each coagulant after the coagulant precipitation process (S50), and Table 2 below shows the cobalt (Co) concentration measurement for the selected soil by repeatedly washing artificial cobalt (Co) contaminated soil. is the result As a result of the first washing, the removal efficiency was close to 78%, and after that, the soils washed for each particle size were recovered and dried for a week. could Compared to the first washing, the removal rate was about 97%, and as shown in FIG. 10 , as a very small amount of cobalt (Co) was detected in the supernatant, it is determined that most of the contaminants are attached to the contaminated soil. Therefore, if the surface soil around the nuclear power plant is washed once and repeatedly washed, it is judged that contaminated soil with a particle diameter in the range of 0.2 ~ 2mm can be recycled.

Cobalt concentration of each selected soil after repeated washing of artificial cobalt-contaminated soil No. Sample name Co (100 mg/kg) Co concentration after the first wash Co concentration after the second wash One artificial soil 3.83 2 Particle size 2~5 mm Washed and sorted soil 0.72 0.07 3 Particle size 0.2~2 mm Washed and sorted soil 0.87 0.12 4 Dewatering Sludge (Under) 2.70 0.01 5 Dewatering sludge (Over) 0.13 0.00

11 is a graph showing the correlation between the turbidity of the turbidity and the concentration of cobalt in this Example. Here, it can be seen that there is a positive correlation between the turbidity of the turbidity and the cobalt (Co) concentration, so instead of measuring the radioactivity of the turbid solution, the turbidity of the turbidity is measured and the degree of contamination of the turbidity and It is also possible to measure the removal rate indirectly.

In order to implement the contaminated soil decontamination process in a reality where it is difficult to directly secure radioactive contaminated soil, in this embodiment, the hydrocyclone process (S40) is carried out with the surface soil around the nuclear power plant, and non-radioactive cobalt (Co) is added to the resulting turbid solution. ) and a compatible standard radioactive cesium (Cs-137) was administered to prepare a contaminated turbid solution, and a natural inorganic powder-type polymer coagulant was added to the turbid solution as a coagulant. In other words. 0.5 g of the coagulant was added to 500 mL of the contaminated turbid solution prepared as described above (500 mL: 0.5 g), and the turbidity was stirred for 2 minutes at a stirring speed of 200 rpm or more, followed by 1 minute at a weak stirring speed of 50 rpm. did. The concentration of radioactive cesium in the turbid solution before the addition of the coagulant (before treatment) and the concentration of radioactive cesium (Cs) in the supernatant water after the addition of the coagulant (after treatment) are measured, and the removal rate is calculated by the following equation, and the result is shown in FIG. indicated.

As shown in FIG. 12, it can be seen that when a natural inorganic polymer coagulant is administered to a turbid solution of washing water and contaminated soil, radioactive materials are well removed. The removal rate of radioactive cesium (Cs) was 96.5% in the case of supernatant water.

The decontamination system of the present invention as described above configures each component to be movable, so that it can be operated in combination at the polluted site, so that each process of soil collection, crushing, and fractionation is performed on site, and the remaining uncontaminated soil is so that it can be restored again. In addition, a special vehicle capable of mounting each component is provided, mounted on one or several vehicles, and moved to the contaminated site so that it can be operated immediately, eliminating the need for foundation construction, etc. to be minimized.

According to the present invention, radioactive waste can be minimized by separating and treating contaminated soil into fine soil to which radioactive materials are mainly bound and contaminated soil with a particle size larger than that, and the decontamination process and decontamination system are simplified to continuously and rapidly and efficiently at the contaminated site. Decontamination work can be done, and the treated clean soil can be immediately backfilled on site or recycled for other purposes. In addition, since the present invention does not use an acid or alkali agent, the waste liquid does not increase and secondary water treatment is not required, and the water quality of the washing waste water is high, so that it can be recycled.

In addition, in the present invention, the contaminated soil is not limited to a specific contaminated soil, and the radioactive material is also not limited to a specific nuclide, cesium (Cs), strontium (Sr), barium (Ba), cobalt (Co), uranium (U), etc. It can target various radioactive substances.

Although the present invention has been described based on the embodiments above, the present invention is not limited thereto, and various changes and modifications are possible within the scope of the technical spirit of the present invention. Therefore, the scope of the present invention is not limited by the above description. In addition, the reference numerals described in the detailed description of the present invention and the claims are appended for reference in order to facilitate the understanding of the present invention, and the present invention is not limited to the form in the drawings.

101: washing water tank 102: water pump 103: pressure sensor 104: flow sensor 105: Hopper 106: quantitative feeder 107: flow sensor 108: pressure sensor 109: water pump 110: inclined conveyor belt 201: first high-pressure washing device 202: second high pressure washing device 203: third high pressure washing device 204: drum screen sorter 2041: first outlet 2042: second outlet 2043: stay chin 2044: through hole 205: first vibration dehydration screen 206: second vibration dehydration screen 207: mobile bogie for discharging cleaning soil 208: first discharge conveyor belt 209: second discharge conveyor belt 210: first storage tank 211: first sand pump 301: first hydrocyclone 302: second hydrocyclone 303: fourth high pressure washing device 304: third vibration dehydration screen 305: third discharge conveyor belt 306: second sand pump 307: second storage tank 308: flow control tank 309: underflow reservoir 310: overflow reservoir 403: zeta potentiometer 404: fine soil coagulation and sedimentation tank 405: coagulant automatic injector 406: coagulant automatic injector 407: ultra-fine settling coagulation and precipitation tank 408: zeta potentiometer 409: distribution pump 501: dehydrator 502: fine soil dewatered sludge storage tank 503: fine earth dewatered filtrate storage tank 601: washing wastewater tank 602: flow sensor 603: water pump 701: mobile bogie for sludge discharge 702: sludge drying device 703: radioactivity meter

Claims (12)

Contaminated soil input process (S10) of putting contaminated soil into the decontamination system, high-pressure washing process of breaking the aggregate structure and separating coarse gravel and impurities by high-pressure washing of the contaminated soil injected into the decontamination system (S20), the high-pressure washing process Partitioning process by particle size (S30) of fractionating the contaminated soil that has passed (S20) by particle size by high-pressure washing and vibration dehydration screen, A hydrocyclone process (S40) of fractionation into a seto turbid solution, a coagulation precipitation process (S50) of coagulating and precipitating the turbidity that has undergone the hydrocyclone process (S40) to separate solid and liquid and removing radioactive materials in the turbid solution (S50), the coagulation precipitation process A micrototal dewatering process (S60) of removing moisture from the sludge precipitated by solid-liquid separation in (S50) and a drying and solidification process of drying the dewatered sludge dewatered through the micrototal dewatering process (S60), shielding, isolating and fixing it ( S70) radioactive contaminated soil decontamination method comprising According to claim 1, If the radioactive contamination level of the fine soil with a particle diameter of 0.2 to 0.05 mm solidified in the drying and solidification step (S70) is insignificant, it is mixed with sand and used for civil engineering or industrial use. The radioactive contaminated soil decontamination according to claim 1, wherein, in the dry and solidification process (S70), fine soil with a particle diameter of 0.2 to 0.05 mm and ultra-fine soil with a particle diameter of less than 0.05 mm containing a high concentration of radioactivity are treated as low-level waste. Way According to claim 1, The high-pressure washing process (S20), the particle size fractionation process (S30), the hydrocyclone process (S40), or the radioactivity level of the washed soil or dewatered sludge separated through the micrototal dewatering process (S60) Radioactive contaminated soil decontamination method, characterized in that by measuring and returning to the previous process if the level of radioactivity is higher than the standard value A drum screen sorter 204 for washing contaminated soil and separating gravel and contaminants with a particle diameter of 25 mm or more, a first high-pressure washing device 201 installed above the entrance of the drum screen sorter 204, The drum screen sorter 204 ) installed under the first vibrating dewatering screen 205 to separate washing soil with a particle diameter of 5 mm or more, a second high-pressure washing device 202 installed on the first vibrating dewatering screen 205, the first vibrating dewatering screen A second vibrating dewatering screen 206 installed under the 205 to separate washing soil having a particle diameter of 2 mm or more, a third high-pressure washing device 203 installed on the second vibrating dewatering screen 206, the second vibrating A first storage tank 210 installed under the dewatering screen 206 to store the turbid liquid passing through the second vibrating dewatering screen 206, and connected to the first storage tank 210 through a pipe to drain the turbid liquid. A first hydrocyclone 301 separated into an upper part and a lower part according to the particle size, a particle diameter of 0.2 mm or more among the turbid solution installed under the first hydrocyclone 301 and discharged to the lower part of the first hydrocyclone 301 A third vibrating dewatering screen 304 for separating the washing soil, a fourth high-pressure washing device 303 installed on the third vibrating dewatering screen 304, and installed under the third vibrating dewatering screen 304, A second storage tank 307 for storing the turbid liquid that has passed through the third vibrating dehydration screen 304, is connected to the second storage tank 307 through a pipe to drain the turbid liquid from the second storage tank 307 according to its particle size. A second hydrocyclone 302 separating the upper part and the lower part is connected to the upper part of the first hydrocyclone 301 and the second hydrocyclone 302 by a pipe to the first hydrocyclone 301 and the second hydrocyclone Flow control tank 308 for storing the turbid liquid discharged to the upper part of (302), is connected to the second hydrocyclone 302 by a pipe to store the turbid liquid discharged to the lower part of the second hydrocyclone 302 The underflow storage tank 309, the flow control tank 308 and the turbidity overflowing from the flow control tank 308 connected to the pipe The overflow storage tank 310 for storing the liquid, the fine soil coagulation and sedimentation tank 404 connected to the underflow storage tank 309 and the pipe and receiving the turbid solution stored in the underflow storage tank 309 for flocculation and precipitation, the The ultrafine soil coagulation and sedimentation tank 407 connected to the overflow storage tank 310 by a pipe and receiving the turbid solution stored in the overflow storage tank 310 for coagulation and precipitation, the fine soil coagulation and sedimentation tank 404 and the ultrafine soil coagulation and sedimentation tank A dehydrator 501 that is connected to 407 by a pipe and removes moisture from the sludge settling in the fine soil coagulation and sedimentation tank 404 and the ultrafine soil coagulation and sedimentation tank 407 and the sludge from which moisture has been removed by the dehydrator 501 Radioactive contaminated soil decontamination system comprising a sludge drying device 702 for drying According to claim 5, Washing water tank 101 for storing contaminated soil washing water, a hopper 105 for storing contaminated soil, the fine soil flocculation and sedimentation tank 404 and the ultrafine soil flocculation and sedimentation tank 407 and dehydrator 501 ) and a pipe connected to the radioactive contaminated soil decontamination system, characterized in that it further comprises at least one of the washing wastewater tank 601 for storing the supernatant water and the dehydrated filtrate separated from the sedimentation turbid solution. According to claim 5, Radioactive soil decontamination system characterized in that the drum screen separator 204 is installed at an angle of 10 to 20 degrees According to claim 5, A plurality of retention jaws 2043 are formed along the inner circumferential surface of the drum screen separator (204), and a plurality of through holes (2044) are drilled in the retention jaws (2043). Contaminated soil decontamination system The collision plate according to claim 5, wherein the first high-pressure cleaning device (201), the second high-pressure cleaning device (202), the third high-pressure cleaning device (203), or the fourth high-pressure cleaning device (303) is inside the injection nozzle. Radioactive contaminated soil decontamination system characterized in that it is installed The high-pressure water sprayed from the first high-pressure washing device 201, the second high-pressure washing device 202, the third high-pressure washing device 203, or the fourth high-pressure washing device 303 for the first vibration Radioactive contaminated soil decontamination, characterized in that it is configured to be sprayed obliquely in the direction opposite to the flow of the soil moving by the vibration of the dewatering screen 205, the second vibrating dewatering screen 206 or the third vibrating dewatering screen 304 system According to claim 5, A zeta potential meter (403,408) for measuring the zeta potential of the turbid solution and an automatic coagulant injector (405,406) are installed in the fine soil coagulation and precipitation tank (404) and the ultrafine soil coagulation and precipitation tank (407), and the zeta Radioactive contaminated soil decontamination system, characterized in that the coagulant auto-injector (405, 406) is configured to automatically inject the coagulant according to the zeta potential measured by the potentiometer (403, 408) Each component device of the decontamination system is configured to be movable, and a special vehicle suitable for mounting each component device is provided, and each component device is mounted on the special vehicle so that it can be moved to a contaminated site and operated immediately. Radioactive contaminated soil decontamination system, characterized in that

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