JP2019095300A - Lake decontamination method - Google Patents

Abstract

To provide a lake decontamination method for surely and efficiently decontaminating reserved water and bottom soil contaminated by a radioactive material.SOLUTION: A lake decontamination method in the invention is conducted by: a decontamination area segmentalization step of using a silt fence to segmentalize a lake into prescribed decontamination areas; a bottom excavation step of making bottom soil in the respective decontamination areas muddy by using a hydraulic shovel to excavate the bottom soil by prescribed depth and also by using a mixer to mix it with reserved water in the same areas; a flocculation and separation step of using a jetting machine to jet a flocculant to the muddy reserved water and then separating it into coagulated soil and clear water; a suction step of using a suction pump to suck the separated coagulated soil along with the clear water; a sorting step of using a sorter to sort out the sucked coagulated soil and clear water from each other; a clear water returning step of returning the sorted clear water to the lake; and a soil decontamination step of applying decontamination processing to the sorted coagulated soil.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a decontamination method in a lake, and more particularly, to a lake decontamination method for reliably and efficiently decontaminating reservoir water and bottom soil contaminated with radioactive materials in a lake.

  Conventionally, radioactive substances including radioactive cesium (cesium 134 and cesium 137), radioactive iodine (iodine 131), and radioactive strontium (strontium 90) released to the atmosphere due to a radioactive accident are diffused by wind or rain. The rain falls on the surface and deposits in rivers, dams, lakes, and paddy fields, which, unlike the methods of decontaminating rainwater and soil on the ground, simultaneously decontaminate a large amount of stored rainwater and sedimentary soil. As a result, no effective decontamination method has been established until now.

  Most of the lake decontamination methods in recent years have adopted a method of removing the contaminated soil deposited on the bottom of the lake using a power shovel or vacuum, but the water stored in dams and lakes is used for the construction. A method of excavating all contaminated soil and a method of vacuuming the contaminated soil and reservoir water deposited on the bottom of the lake, separating the contaminated soil and reservoir water, and then discharging only the reservoir water to process the contaminated soil Was taken. Therefore, in order to decontaminate a wide range of lakes, it is necessary to empty all the storage water anyway, so it is practically difficult and operation efficiency is poor, and a large amount of labor is required for workers. There was a problem that

  As a method for treating contaminated soil in the prior art, for example, a "method of decontaminating radioactive material" (see Patent Document 1) has been proposed and has become a well-known technology. The "method for decontamination of radioactive material" is an adsorption method which conventionally occurs after adsorbing the radioactive material to an adsorbent which adsorbs the radioactive material for decontamination of soil, rubble and water contaminated with the radioactive material. A technology that makes it possible to more freely crawl and mix the adsorbent by reducing the difficulty of recovering the material itself, and does not require the use of a net or cloth to prevent the diffusion of the adsorbent itself It is a proposal.

  However, such a proposal of “method of decontamination of radioactive material” is to remove radioactive material from a mixture of one or more of soil, rubble and water contaminated with radioactive material (hereinafter referred to as the mixture). The basalt which has a porous property and contains iron oxide as an adsorbent for adsorbing radioactive substances is mixed with the mixture, and after the radioactive substances are adsorbed to the basalt, the basalt is attracted using magnetic force and separated from the mixture Adopt a means of recovering basalt adsorbed with radioactive material, and the contaminated soil at the bottom of the lake can be removed, but when decontaminating a large area of lakes, the water stored there It is necessary to pull out all the problems, and the solution to the above problems has not been achieved.

  In addition, it is possible to easily set the amount of radioactive material in the pond below the standard value, and the method for decontamination treatment of radioactive materials (see Patent Document 2) is proposed, which generates less radioactive waste due to decontamination. And has become known. Specifically, a drainage step for draining water from the reservoir, a suction droop step for sucking and collecting sediment sludge deposited on the bottom of the reservoir after the water drain step, and a sediment deposited after the suction droop step A method comprising a flocculating separation step of adding a coagulant to sludge and separating it into flocculated sludge and supernatant, and a dewatering step of pressure dewatering the flocculated sludge after the flocculation separation step to make a dewatered cake is there.

  However, such a proposal for the “method of decontamination treatment of radioactive materials” requires a suction dredging operation for sucking and covering sediment sludge deposited on the bottom of the reservoir after draining water from the reservoir, so As the workers move, the working efficiency is extremely low, and the labor burden on the workers also increases, and if it is necessary to decontaminate the pond for a wide area, it is still necessary to drain all the stored water. It has not reached the solution of the above problem.

  Furthermore, it can remove pollutants including radioactive materials such as ponds rapidly and reliably over a wide area "contaminants containing radioactive substances by spraying granular zeolite with a flying object such as a helicopter on the pond etc. No. 5,075,014 has been proposed, and has become a well-known technology. Specifically, radioactive material-containing pollutants are deposited on the bottom and so on, so particulate zeolite is sprayed in the air from the top of the pond etc using the flying object etc., and the surface such as the bottom containing pollutants is zeolite layer Covering with zeolite, adsorbing and sealing contaminants with zeolite, preventing floating and scattering of contaminants, and decontamination methods such as ponds, wherein the zeolite layer adsorbs and seals contaminants with zeolite, It has a thickness effective to prevent floating and scattering of contaminants, and employs a means for covering the surface such as the bottom containing contaminants with a zeolite layer.

  However, the proposal of “method of decontaminating reservoirs etc.” is that the coated zeolite layer is cracked or eroded by the subsequent temporal change of the formation or natural phenomena such as earthquakes, and the contaminants are again in the water. It may be released and is effective as a temporary emergency measure, but as a permanent pollution prevention measure, it is not possible to secure sufficient security and security for the people living nearby. It was a technical proposal.

  Furthermore, a radioactive material contained in water or sediment of the water bottom can be decontaminated by a simple apparatus or method "a method of decontaminating a radioactive substance contained in water bottom sediment or in water" (see Patent Document 4) Has been proposed and is known. Specifically, a method of decontaminating radioactive substances contained in the bottom of the water bottom or in the water by sinking the connection mat in which a plurality of bags filled with adsorbents are connected to the bottom of the water, and recovering it. The adsorbent is obtained by natural coagulum of diatomaceous earth, or by crushing and calcining mudstone or clay rock, and the bag has a mesh of a size that does not cause the adsorbent to flow out and clog, At both ends of the connection mat, a means for pulling up from the bottom of the water is provided for decontamination.

  However, such a proposal of “Method for decontaminating radioactive substances contained in bottom sediments or in water bottom” is a method in which a connection mat in which a plurality of bags filled with adsorbent are connected is sunk to the bottom of a wide range of lakes. The decontamination of toxic substances requires a bag filled with a large amount of adsorbent, and due to the change over time, dirt, dirt, algae, etc. adhere on the bag and the radiation removal effect is diminished. It is a proposal that there is a problem that

  The present applicant focused on a method for decontaminating stored water and radioactive materials in the bottom soil in a wide range of reservoirs such as lakes and the idea that decontamination work can not be performed without emptying all the stored water, We developed a lake decontamination method that decontaminates the area and decontaminate the reservoir water and bottom soil for each area reliably and efficiently, and leads to the proposal of the "lake decontamination method" in the present invention.

JP 2013-164407 Unexamined-Japanese-Patent No. 2015-117988 JP 2015-111100 JP 2015-10852

  An object of the present invention is to provide a lake decontamination method for reliably and efficiently decontaminating reservoir water and bottom soil contaminated with radioactive materials in a lake, in view of the above problems.

  In order to solve the above problems, the present invention is a lake decontamination method for reliably and efficiently decontaminating storage water and bottom soil contaminated with radioactive materials, and the lake is subjected to a predetermined decontamination area with a silt fence. Decontamination area demarcation process to be divided, Bottom excavation process to excavate the bottom soil in the decontamination area with a reservoir at the same time by excavating the water bottom soil in the decontamination area to a predetermined depth and stirring with the agitator in the same area, Mud Flocculating separation step of injecting flocculating agent into solidified soil water by injection machine to separate into coagulated soil and clear water, suction step of sucking separated coagulated soil together with clear water by suction pump, and coagulated suction It consists of a sorting process to separate the soil and clear water with a sorting machine, a clear water return process to return the sorted clear water to the lake, and a soil decontamination process to decontaminate the sorted coagulated soil. hand The take.

  Further, according to the present invention, the decontamination area dividing step is sequentially moved according to the size of the lake and repeatedly constructed, and the water bottom excavation step, the flocculation separating step and the suction step are sequentially moved correspondingly to it, and repeated construction Can be adopted.

  Furthermore, the present invention may employ means that is installed in a state in which the excavator, the injector, and the suction pump are placed on one or more vessels floated in a lake.

  Furthermore, according to the present invention, prior to the construction of the decontamination area dividing step, there is a prior monitoring step for confirming the bottom condition such as bottom topography and depth in the lake, thickness and hardness of bottom soil, and presence or absence of obstacles in the lake. The means to be constructed can be adopted.

  Furthermore, the present invention may employ a method in which a post-monitoring step for confirming the suction condition of the solidified soil is implemented by collecting a sample of the bottom soil in the decontamination area after the application of the suction step. .

  According to the lake and lake decontamination method according to the present invention, the area is divided by dividing the wide area to be decontaminated with the lake by the silt fence, and the storage water and the bottom soil are decontaminated reliably and efficiently for each area. It has an excellent effect of improving work efficiency and reducing labor.

  Further, according to the lake and lake decontamination method according to the present invention, since the work area is divided, the storage capacity of the suctioned clear water to be returned to the lake can be small, and space saving of working equipment and the like can be realized. It plays an excellent effect such as.

  Furthermore, according to the lake decontamination method in the present invention, the decontamination area dividing step is sequentially moved according to the size of the lake and repetitively constructed, and according to it, the water bottom excavation step, the flocculation separation step and the suction step By sequentially moving and repeating construction, it is possible to reliably and efficiently decontaminate the area even in a wide area of the lake, which has an excellent effect of contributing to the improvement of work efficiency and reduction of labor.

  Furthermore, according to the lake and lake decontamination method according to the present invention, the equipment used in each process is placed on one or a plurality of vessels floated in the lake and floated on the water to move as needed. By doing this, it is possible to install while moving a wide range of lakes smoothly, and there are outstanding effects such as contributing to the improvement of work efficiency and reduction of labor.

It is a flowchart which shows the 1st implementation process of the lakes and lakes decontamination method concerning this invention. Example 1 BRIEF DESCRIPTION OF THE DRAWINGS It is typical sectional explanatory drawing which shows the embodiment of the lakes and lakes decontamination method concerning this invention. It is explanatory drawing which shows the construction aspect of the lakes and lakes decontamination method concerning this invention. It is a flowchart which shows the 2nd implementation process of the lakes and lakes decontamination method concerning this invention. (Example 2)

The lake and decontamination method 10 according to the present invention divides the area by dividing the lake into predetermined decontamination areas 21 with the silt fence 22 so as to divide the area and store water W1 and the bottom of each area. The greatest feature is that it has taken measures to decontaminate soil S1 reliably and efficiently.
Hereinafter, an embodiment of a lake and decontamination method 10 according to the present invention will be described based on the drawings.

The lake decontamination method 10 according to the present invention is not limited to the embodiment described below, but is within the scope of the technical idea of the present invention, that is, the range of methods, devices and the like that can exhibit the same effects. It can be changed as appropriate.
Further, the meanings of the terms used in the description of the present invention are not necessarily determined uniquely, and can be broadly interpreted within the scope of the technical idea of the present invention. For example, in the present invention, "lakes and lakes" refer to lakes, swamps, and ponds in the natural world, as well as rivers and oceans, or artificially created artificial ponds, reservoirs, dams, reservoirs, paddy fields, etc. It is a word that can be interpreted as a concept that includes everything.

FIG. 1 is a flow chart showing a first implementation process of the lake and decontamination method 10 according to the present invention. Moreover, FIG. 2 is typical sectional explanatory drawing which shows the embodiment of the lake decontamination method 10 concerning this invention. Furthermore, FIG. 3 is explanatory drawing which shows the construction aspect of the lake decontamination method 10 concerning this invention.
The lake decontamination method 10 according to the present invention includes the decontamination area dividing step 20, the bottom excavation step 30, the flocculation and separation step 40, the suction step 50, the sorting step 60, the clear water return step 70, and the soil removal. Taking the means constituted by the dyeing process 80, the specific contents of each process are as follows.

  The decontamination area dividing step 20 is a step of dividing the lake into predetermined decontamination areas 21 by the silt fence 22. Specifically, the bottom condition such as the size and depth of the lake to be decontaminated, presence or absence of obstacles, etc. Further, the decontamination area 21 of an arbitrary range is divided by the silt fence 22 based on the construction schedule and the like.

  The silt fence 22 used has a length capable of vertically or horizontally dividing the lake, and a height at which the bottom contacts the bottom over the entire length, and a plurality of floats that can float on the water surface at the top The body is properly arranged, a weight consisting of a metal chain etc. for keeping the bottom of the body in contact with the bottom of the body is arranged in the whole area, and the middle part from the top to the bottom has water permeability while impinging soil material For example, it is formed of a material having a mesh structure. In addition, in order to aim at the transportability improvement of the silt fence 22, the aspect which ensures a required length is also possible by connecting the silt fence 22 of predetermined length together.

  The water bottom excavation step 30 is a step in which the water bottom soil S1 in the decontamination area 21 is excavated to a predetermined depth by the excavator 31 and simultaneously stirred with the stored water W1 in the area 21 by the agitator to form a muddy is there. The depth to which the bottom soil S is excavated is not particularly limited, and is appropriately determined in consideration of the degree of contamination of the lake, the thickness of sedimentation of the bottom soil S1, etc. The bottom soil S1 will be excavated.

The excavator 31 is, for example, a hydraulic power shovel and is excavated so as to pierce the bottom soil S1 at the tip of a bucket (excavator). The stirrer is not particularly limited, and it may be considered to prepare separately from the excavator 31. However, the excavator 31 can be considered by using a power shovel having a bucket (excavator) with a mixing function inside. It becomes possible to put together and the stirrer together in one unit. Thereby, the stored water W1 and the bottom soil S1 in the decontamination area 21 are stirred simultaneously with the excavation and become muddified.
In addition, the digging machine 31 is equipped with a digging sensor at the tip of the bucket (excavator), and when the digging reaches a predetermined depth, the sensor may react. Moreover, the aspect which equips an underwater camera with a bucket (excavator) tip and works while monitoring an excavation condition can also be considered.

  The flocculation and separation step 40 is a step of injecting the coagulant 41 into the muddy storage water W1 by the injector 42 to separate it into solidified soil S2 and clear water W2, specifically, it is agitated with the bottom soil S1. The coagulant 41 having the adsorptive action of radioactive contaminants is sprayed and dissolved in the stored water W1 in the mud-like decontamination area 21 to dissolve the contaminants together with the bottom soil S1 by the action of the coagulant 41. It coagulates and separates into solidified soil S2 and clear water W2.

As coagulant | flocculant 41, coagulant | flocculant 41, such as PAC (poly aluminum chloride) and a zeolite type, is used, for example. In addition, it is preferable to use an inorganic coagulant 41 safe to human bodies and animals and plants in consideration of the natural environment.
In this step, it is necessary to wait for several minutes until the coagulated soil S2 and the clear water W2 are separated after spraying the coagulant 41, and the solidified soil S2 precipitates in water by its own weight, and the clear water W2 is upward It will accumulate in the

  The suction step 50 is a step of sucking the separated coagulated soil S2 together with the clear water W2 by the suction pump 51. Specifically, the coagulated soil S2 precipitated on the water bottom in the decontamination area 21 is combined with the clarified water W2 Aspiration process. At this time, although the stored water W1 flows into the decontamination area 21 from the outside of the area due to the water permeability of the silt fence 22, the inflow of the contaminated water bottom soil S1 is inhibited. The coagulated soil S2 and the clear water W2 sucked are sent to the sorting machine 61 via the transfer hose 62 and the like.

  It is sufficient for the suction pump 51 used in this step to use a conventional method, and is not particularly limited. In addition, the tip of a suction hose may be fixed to the tip of the bucket (excavator) in the excavating machine 31, and the aspiration point in the decontamination area 21 may be moved by the movement of the bucket (excavator).

  The sorting step 60 is a step of sorting the suctioned coagulated soil S2 and the clear water W2 respectively by the sorter 61. Specifically, the solidified soil S2 is removed from the coagulated soil S2 and the clear water W2 sucked together. It is separated into only the solidified soil S2 and only the clear water W2, and is performed simultaneously with the suction of the coagulated soil S2 and the clear water W2 in the suction step 50.

Although it does not specifically limit about the specific structure of the sorter 61, For example, the aspect which makes solidified soil S2 pass and clear water W2 can mediate the filter (cloth body etc.) which can pass can be considered.
The separated solidified soil S2 is placed in a storage container 82 such as a flexible container bag, and the clear water W2 is placed in a storage tank 72 and stored.

  The clear water return step 70 is a step of returning the sorted clear water W2 back to the lake, specifically, temporarily for the clear water W2 sorted into the solidified soil S2 and the clear water W2 in the sorting step 60. It is a process of storing the storage tank 72 and thereafter returning the clear water W2 to the lake. There is no limitation in particular about the place which returns the clear water W2 in a lake, and the inside and the outside of the decontamination area 21 do not matter.

  Although the water amount of the clear water W2 to be returned is that the coagulated soil S2 has some water content, substantially the same water amount as the initial stored water W1 is returned. As a result, the lake is reborn as a lake with the newly decontaminated fresh bottom as the surface layer by digging and removing the contaminated bottom soil S1 of the required depth.

  The soil decontamination step 80 is a step of decontaminating the coagulated soil S2 thus selected. Specifically, the coagulated soil S2 is placed in a storage container 82 such as a FIBC bag and transported to a disposal site, and then to the disposal site. Specifically, the final treatment for decontamination is performed. The decontamination treatment of the solidified soil S2 in the disposal site is carried out by a conventional decontamination treatment for the soil, and is not particularly limited.

  That is, first, the coagulated soil S2 is washed to decontaminate the radioactive material by 50% or more (washing step), and then the washed coagulated soil S2 is subjected to a classifier and contaminated soil containing elementary particles (fine particles) of 200 microns or less Classify into water and soil containing coarse particles of 200 microns or more (classification process), stir in a stirring tank so that radioactive substances contained in contaminated soil water are evenly distributed in water (stirring process) ) The stirred contaminated soil water is separated into water-containing sludge and fresh water by a single-liquid separator (solid-liquid separation step), and the water-containing sludge is dewatered by a dehydration filter to form sludge (dewatering step), the sludge Is placed in a container such as a flexible container bag for disposal (bagging process). In addition, soil containing coarse particles of 200 microns or more generated in the classification step and fresh water generated in the solid-liquid separation step are returned to the lake because they are decontaminated without containing radioactive substances. It is also possible.

  The lake decontamination method 10 according to the present invention is constructed by the above-described steps, but various devices used in each step, for example, the excavating machine 31 used in the water bottom excavation step 30 or the aggregation In the case of a relatively small scale of the lake, the injector 42 used in the separation step 40 and the suction pump 51 used in the suction step 50 can be installed on the shore and constructed. However, in view of the working efficiency when the lake is wide, etc., it is desirable that the various devices be placed on the boat 23 floated in the lake as needed, and each process be implemented.

At this time, the number of platforms 23 on which various devices are mounted is not particularly limited, and a plurality of platforms 23 are prepared and mounted in addition to a mode in which all the devices are mounted on one platform 23. It is also possible to appropriately allocate the devices to be installed.
Further, the device to be mounted on the vessel 23 is not limited to the above-exemplified one, and, for example, the storage tank 72 used in the sorting machine 61 used in the sorting process 60 or the clear water returning process 70 The storage container 82 and the like used in the soil decontamination step 80 can also be appropriately placed on the berth 23 as needed. However, the coagulated soil S2 sucked with the clear water W2 by the suction step 50 is contaminated with radioactivity and has a high radiation dose due to aggregation, so it was temporarily stored on the table ship 23 even if temporarily In such a case, there is a concern that the workers working on the vessel 23 will be exposed to radiation. Therefore, it is desirable that the sorting machine 61 and the storage container 82 be installed on land instead of being mounted on the vessel 23.

  By the way, the division of the decontamination area 21 of the lake using the silt fence 22 in the decontamination area dividing step 20 is carried out by using a plurality of silt fences 22 as shown in FIG. Although the construction aspect divided into the area 21 can also be considered, the aspect which moves repeatedly according to the size of the lake and carries out division of the decontamination area 21 sequentially is also possible. That is, as shown in FIG. 3A, the area A is first divided as the decontamination area 21 by the silt fence 22, and after the decontamination of the area A is completed, the new silt fence 22 is used to The B area adjacent to the area is divided as the decontamination area 21. When the decontamination of the B area is completed, the silt fence 22 which has divided the A area and the B area is removed, and the C area adjacent to the B area is divided as the decontamination area 21 using the silt fence 22. Thus, by using the silt fence 22 removed while moving sequentially for division of the next decontamination area 21, if there are two silt fences 22 for one lake which is to be decontaminated, the present invention The construction of the Lake Decontamination Method 10 is possible.

In the embodiment in which the decontamination area dividing step 20 (division of the decontamination area 21 of the lake using the silt fence 22) is sequentially moved and repeatedly constructed, the bottom excavation step 30 and the aggregation and separation step 40 in the subsequent steps Also in the suction process 50, each decontamination area 21 is sequentially moved and repeatedly constructed.
In this way, when carrying out decontamination work by dividing the lake into a plurality of decontamination areas 21, by repeating construction while moving sequentially, decontamination can be carried out reliably and efficiently for each area even in a wide range of lakes. Contribute to work efficiency and labor reduction.

The construction procedure of the lake decontamination method 10 according to the present invention including the above-described steps and each configuration is as follows.
<< construction procedure >>
(A) An arbitrary number of decontamination areas 21 (for example, A, B, C, D, and E areas) are assumed in accordance with the size of the lake to be decontaminated and the construction schedule.
(B) A stand 23 is floated on a lake, and various devices (excavator 31, injector 41, suction pump 51, etc.) are mounted on the stand 23.
(C) The area A is divided into the decontamination area 21 using the silt fence 22. At this time, the boat 23 is located in the same area A. (Decontamination area cutting process 20)
(D) While excavating the bottom soil S1 in the area A with the excavator 31, it mixes with the reservoir water W1 in the area with the agitator to form a mud. (Bottom drilling process 30)
(E) The coagulant 41 is sprayed to the accumulated water W1 by the injector 42 and then waits for several minutes to separate it into coagulated soil S2 and clear water W2 which are precipitated by their own weight. (Agglomeration separation process 40)
(F) The separated solidified soil S2 is suctioned by the suction pump 51 together with the clear water W2. At this time, the stored water W1 flows into the area A from outside the area via the silt fence 22. (Suction process 50)
(G) Simultaneously with the suction of the solidified soil S2 and the clear water W2, the coagulated soil S2 and the clear water W2 sucked by the land sorting machine 61 are respectively separated, and the solidified soil S2 is stored in a container 82 such as a FIBC bag. While storing it, the clear water W2 is sent to the storage tank 72 and temporarily stored. (Sorting process 60)
(H) The clear water W2 temporarily stored in the storage tank 72 is returned to the lake. (Clear water return process 70)
(I) The storage container 82 containing the solidified soil S2 is transported to a disposal site outside the lake, and the decontamination treatment of the solidified soil S2 is performed according to a conventional method. (Soil decontamination process 80)
(J) When the above operations (c) to (f) are completed in the area A, the operation moves to the next area B and the operations after the above (c) are performed again.
(K) After that, move sequentially from C area → D area → E area, and do the work from (c) onward in the same way, and the work of the final area (E area) is completed. Construction of the dye reduction method 10 is completed.

  In the above construction procedure, the area A is an area surrounded by the shore of the lake and the new silt fence 22. The B area is an area outside the A area and sandwiched between the silt fence 22 used for dividing the A area and the new silt fence 22. The same applies to the subsequent areas (after the C area). The area is sandwiched between the silt fence 22 used for dividing the former area and the new silt fence 22. The final area (E area) is an area surrounded by the silt fence 22 used to divide the preceding area and the shore of the lake.

  By the way, the silt fence 22 used for division after C area except the final area in the above-mentioned construction procedure can take the aspect which removes the silt fence 22 used for division of the front second row area and reuses it. It is. That is, the silt fence 22 used in the A area is reused to divide the C area, and the silt fence 22 used in the B area is reused to divide the D area. Therefore, when constructing the lake and decontamination method 10 according to the present invention, at least two silt fences 22 are sufficient for one lake which is to be decontaminated.

  Moreover, in the said construction procedure, the construction aspect which does not use the barge 23 which mounted various apparatuses in the operation | work of an initial area (A area) and a final area (E area) can also be considered. That is, since the tangent distance with the shore is long in the initial area (area A) and the final area (E area), various devices can work efficiently while moving along the shore without using the ship 23 It is.

  In the lake and lake decontamination method 10 according to the present invention configured as described above, the broad area to be decontaminated with lakes and lakes is divided into a plurality of decontamination areas 21 by the silt fence 22 and decontamination work is sequentially performed for each divided area By carrying out the method, the stored water W1 and the bottom soil S1 can be decontaminated reliably and efficiently, which contributes to the improvement of work efficiency and reduction of labor compared with the conventional method.

  Another embodiment will be described with reference to FIG. The same parts as in the first embodiment are omitted. FIG. 4 is a flowchart showing a second implementation process of the lake and decontamination method 10 according to the present invention.

In each lake, the condition of the bottom such as presence or absence of driftwood and the amount of sediment of the bottom soil S1 is not uniformly determined by the surrounding environment, but excavating the bottom soil S1 and adhesion to the bottom of the silt fence 22 It is considered that it affects each operation related to the lake and lake decontamination method 10 according to the present invention, and in some cases, it may be an adverse effect such as operation efficiency.
Moreover, when the water depth is deep when constructing the suction process 50, it may be difficult to determine whether suction of the solidified soil S2 in the decontamination area 21 has been completely made.

  Therefore, first, in the lake decontamination method 10 according to the present invention, it can be considered to adopt an aspect in which the pre-monitoring step M1 is performed before the decontamination area dividing step 10 is performed. That is, the pre-monitoring step M1 is a step for confirming and monitoring the bottom condition in the lake in advance, such as bottom topography, depth, thickness and hardness of bottom soil S1, and presence or absence of obstacles.

  Although the specific construction mode in the pre-monitoring step M1 varies depending on the work content to be confirmed, a general monitoring method is generally used for each content. For example, to monitor underwater topography, water depth, and the presence or absence of obstacles, a method of underwater exploration with a remote control type underwater camera, a method of bathymetric survey using a sonar (ultrasonic measurement instrument), and each color from the sky A method of emitting laser light and using a time difference of reflection may be considered, and further, it may be considered to adopt a method of visually confirming the water quality after dispersing the coagulant and then visually confirming it. In addition, when monitoring the thickness and hardness of the bottom soil S1 and the state of contamination, a method of sampling the bottom soil S1 at one or a plurality of fixed points can be considered. The fixed point management at this time is performed by, for example, DGPS or lightwave surveying.

  As described above, by performing monitoring on the condition of the bottom of the water in advance before the construction of the decontamination area dividing step 10, it contributes to the improvement of the adhesion of the silt fence 22 to the bottom of the water, and the dividing area in consideration of work efficiency. Contribute to the decision of

  Moreover, in the lake decontamination method 10 according to the present invention, it may be considered to adopt an aspect in which the post-monitoring step M2 is performed after the suction step 50 is performed. That is, the post-monitoring process M2 is a process for confirming and monitoring the aspiration situation of the coagulated soil S2 in the decontamination area 21 after the fact.

  Regarding a concrete construction mode in the post-monitoring step M2, a method of collecting a sample of the bottom soil S1 in the decontamination area 21 and visually confirming the presence or absence of the solidified soil S2 remaining is used. Sampling of the bottom soil S1 is performed at one or more fixed points. The fixed point management at this time is also performed by, for example, DGPS or light wave surveying, as described above.

  As described above, after the construction of the suction process 50, by performing monitoring on the situation of suction afterward, it is possible to eliminate the suction failure of the contaminated solidified soil S2 in the decontamination area 21 and to perform a reliable decontamination work It becomes possible.

  The lake decontamination method 10 according to the present invention is not only lakes and marshes, ponds, rivers and seas in the natural world, but also artificial ponds, reservoirs, dams, reservoirs, paddy fields, etc. It is possible to construct anywhere, and decontaminating the storage water W1 and the bottom soil S1 reliably and efficiently by sequentially performing decontamination work with the decontamination area 21 divided into a plurality of sections by the silt fence 22. It can be done. Therefore, the industrial applicability of the "lake decontamination method" according to the present invention is considered to be extremely large.

10 Lake Decontamination Method 20 Decontamination Area Division Process 21 Decontamination Area 22 Silt Fence 23 Barge 30 Bottom Drilling Process 31 Excavator 40 Cohesive Separation Process 41 Flocculant 42 Sprayer 50 Suction Process 51 Suction Pump 52 Transport Hose 60 Sorting Process 61 Sorting machine 70 Clearing water return process 72 Storage tank 80 Soil decontamination process 82 Storage container M1 Pre-monitoring process M2 Post-monitoring process S1 Water bottom soil S2 Solidification soil W1 Reservoir water W2 Clear water

In order to solve the above problems, the present invention is a lake decontamination method for reliably and efficiently decontaminating storage water and bottom soil contaminated with radioactive materials, and the lake is subjected to a predetermined decontamination area with a silt fence. The decontamination area demarcation process to divide and the bottom soil in the decontamination area are excavated to a predetermined depth by an excavating machine to excavate so as to pierce the bottom of the bucket (excavator) and at the same time the stored water in the area and the agitator. Stirring and muddy water bottom excavation process, Coagulation and separation process where a coagulant is injected into the muddy storage water by a jet to separate it into coagulated soil and clear water, and the coagulated soil separated is clarified water The suction process which sucks with a suction pump with it, the sorting process which separates the coagulated soil and the clear water which are sucked by the sorting machine respectively, the clear water return process which returns the sorted clear water to the lake, the sorted coagulated soil Soil decontamination process for decontamination takes the unit consisting of.

Claims (5)

A lake decontamination and volume reduction method that decontaminates reservoir water and bottom soil contaminated with radioactive materials reliably and efficiently.
Decontamination area division process which divides lakes and marshes into predetermined decontamination area with silt fence,
A bottom excavation step of excavating the bottom soil in the decontamination area by a drilling machine to a predetermined depth and simultaneously stirring and muddying the stored water in the same area by a stirrer;
Flocculation and separation step of injecting a flocculant into the muddy storage water by a jet and separating it into solidified soil and clear water;
A suction step of suctioning the separated coagulated soil together with the clear water by a suction pump;
A sorting step of sorting the aspirated coagulated soil and clear water with a sorting machine;
A clear water return process to return the sorted clear water to the lake;
A soil decontamination step of decontaminating the separated solidified soil;
Lake decontamination and volume reduction method characterized by being composed of   The decontamination area dividing step is sequentially moved according to the size of the lake to be repeatedly constructed, and the water bottom excavation step, the flocculation separating step and the suction step are also sequentially moved and repeatedly constructed accordingly. The lake decontamination and volume reduction method according to claim 1.   The construction according to claim 1 or 2, wherein the excavator, the injector, and the suction pump are installed on one or more vessels floating in a lake. Description of lake decontamination and volume reduction method.   Before the construction of the decontamination area dividing process, a pre-monitoring process is carried out to confirm the water bottom condition such as the bottom topography and depth of the lake, the thickness and hardness of the bottom soil, and the presence or absence of obstacles in the lake. The lake decontamination and volume reduction method according to any one of claims 1 to 3.   After the construction of the suctioning step, a post-monitoring step is carried out to confirm the suctioning state of the solidified soil by collecting a sample of the bottom soil in the decontamination area. Lake decontamination and volume reduction method described in