JP6041578B2 - Treatment method of radioactive cesium contaminated soil - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a treatment method for reducing the volume of soil contaminated with radioactive cesium, in which fine particles containing clay minerals are separated from soil contaminated with radioactive cesium and solidified as a lump (pellet). Further, release of radioactive cesium from the lump is suppressed.

  Surface soil has been removed as a decontamination measure for soil contaminated with radioactive cesium scattered by nuclear power plant accidents, but securing the storage location is a problem. As a countermeasure, a non-patent document 1 proposes a treatment method for reducing the volume of soil contaminated with radioactive cesium. In Non-Patent Document 1, radioactive cesium contained in soil contaminated with radioactive cesium is adsorbed and fixed by clay minerals (especially 2: 1 type layered silicate) in the soil, It has been reported that fixed radioactive cesium is insoluble in water, acid and alkali, and that such clay minerals are often contained in particles with a particle size of 30 μm or less in the soil. . Therefore, in the treatment method described in Non-Patent Document 1, the soil contaminated with radioactive cesium is classified by washing with water to separate fine particles containing clay minerals. Since there is not much radioactive cesium remaining in the remaining large particles from which the microparticles have been separated, they can be backfilled to the original location or reused as a surface layer covering material such as highly contaminated land. The separated fine particles need to be stored as radioactive waste, but the volume of the soil to be stored as radioactive waste can be reduced because the volume is smaller than the original soil capacity.

“Decontamination of Radioactive Cesium-Contaminated Soil by Water Washing” September 6, 2011, 34th Annual Meeting of the Atomic Energy Commission, Material No. 1, Keizo Ishii, Graduate School of Engineering, Tohoku University, Internet <URL: http://www.aec.go.jp/jicst/NC/iinkai/teirei/siryo2011/siryo34/siryo1.pdf>

  Non-Patent Document 1 proposes that the separated fine particles are further dried and pelletized. However, the pellets from which the fine particles have been dried are fragile and easily crushed, and dust containing radioactive cesium may be scattered, or the radioactive cesium may ooze out from the pellet or sublimate and be scattered outside.

  This invention solves the above-mentioned problems in the prior art, and when separating fine particles containing clay minerals from soil contaminated with radioactive cesium and solidifying them as a lump such as pellets, the radioactive cesium is removed from the lump. An object of the present invention is to provide a method for treating radioactive cesium-contaminated soil that is suppressed from being released.

The method for treating cesium-contaminated soil according to the present invention includes a first step of separating microparticles containing clay minerals from surface soil collected in a region contaminated with radioactive cesium, and solidifying the separated microparticles. The method includes a second step of forming the separated fine particle lump and a step of baking and solidifying the lump to form a sintered body. The method for treating cesium-contaminated soil according to the present invention includes a first step of separating microparticles containing clay minerals from surface soil collected in a region contaminated with radioactive cesium, and solidifying the separated microparticles . A second step for forming a lump of the separated microparticles , a third step for unglaring the lump, a fourth step for applying glaze to the unbaked lump, and a lump coated with the glaze the may comprise a fifth step of the fitting. The method for treating cesium-contaminated soil according to the present invention may further include a step of scraping the surface soil in an area contaminated with the radioactive cesium before the first step.

According to the present invention, radioactive cesium can be concentrated and recovered by separating fine particles containing clay minerals adsorbing and fixing radioactive cesium from surface soil collected in an area contaminated with radioactive cesium. Thus, the volume of contaminated soil to be stored as radioactive waste can be reduced, and the storage location of the contaminated soil can be reduced. In addition, the separated fine particles are solidified into a lump such as a pellet, and then sintered into a sintered body or ceramic, so that the brittle lump is hardened and hard to break by simply hardening, thus generating dust containing radioactive cesium. And can be prevented from being scattered. Also, by applying glaze as well as unglazed baking, it is possible to prevent radioactive cesium from leaching out of the lump or sublimating and scattering to the outside compared to unglazed baking, making radioactive cesium more reliable. Can be contained in the mass.

  The processing method of this invention is a sixth step of measuring the radiation dose emitted from the main-baked lump, and the lump whose radiation dose has been measured is separated according to the radiation dose and stored in a storage container. And a seventh step. According to this, a lump can be sorted and stored for each radiation dose. By storing by dose, management processing by attenuation of radiocesium radioactivity can be performed for each storage container.

  In the processing method of the present invention, the seventh step includes a step of storing each lump in each storage space of the pallet using a pallet having a storage space for individually storing the lump, and each storing the lump. And stacking and storing the plurality of pallets in the storage container so that the respective chunks can be stored in the storage container without contacting each other. According to this, by storing lumps using a pallet, it is possible to improve the efficiency of storage, and also prevent the lumps from coming into contact with each other and being damaged when transporting a storage container containing the lumps. be able to.

  The processing method of the present invention may further include an eighth step of attaching individual identification information to the main-baked lump. According to this, the traceability management for every lump becomes possible. The individual identification information includes, for example, the soil collection location, the collection date, the individual number, and the like that are the basis of each lump. As a method of attaching individual identification information, for example, individual identification information is directly printed on each lump with numbers, symbols, barcodes, etc., or a sticker on which these are printed is attached to each lump, or individual identification information is stored. For example, a method of attaching an IC chip.

The treatment method of the present invention is a ninth step of drying the granular material including pebbles and sand left after separating the fine particles including the clay mineral from the surface soil collected in the area contaminated with the radioactive cesium. Can further comprise. According to this, it is possible to prevent residual moisture containing radioactive cesium from leaking out and leaking out as contaminated water after final disposal such as buried storage and backfilling, and causing secondary contamination. . Further, since the volume and weight of residual moisture are reduced by drying, it becomes easy to pack, transport and store in a flexible container bag or the like. Further, by drying, the true radiation dose can be measured without being affected by the radiation shielding effect by moisture.

In the treatment method of the present invention, in the first step, the surface soil collected in the area contaminated with the radioactive cesium is washed with water to extract a suspension containing fine particles containing the clay mineral. And separating the fine particles containing the clay mineral from the suspension, and the water left by the separation of the fine particles containing the clay mineral is scraped up in an area contaminated with radioactive cesium. It can be reused for surface soil cleaning. According to this, even if the radioactive element remains in the water left by the separation of the fine particles containing the clay mineral, the contaminated water can be prevented from leaking to the outside. Moreover, since the washing water is reused, the amount of water newly replenished can be reduced.

  The treatment method of the present invention may further include a tenth step of releasing the gas and exhaust generated in the treatment to the atmosphere after purifying with the cesium adsorption device. According to this, cesium hydroxide is purified by the cesium adsorption device even if sublimation of cesium hydroxide occurs during mass firing or cesium hydroxide is melted in the moisture in the exhaust gas during drying. The cesium hydroxide is prevented from being released into the atmosphere.

  The processing method of this invention can use the glaze which can be used for a roasting as said glaze. According to this, since the main baking can be performed at a relatively low temperature, sublimation of cesium hydroxide can be suppressed at the time of firing the lump. Moreover, the processing method of this invention can perform the said unglazed baking and main baking at the temperature of easy baking. According to this, since uncoating and main baking are performed at a relatively low temperature, sublimation of cesium hydroxide can be suppressed at the time of mass firing.

It is a flow diagram which shows embodiment of the processing method of the radioactive cesium contaminated soil of this invention. It is a graph which shows the experimental result of volume reduction of radioactive cesium contaminated soil by the processing method of FIG. It is a flowchart which shows embodiment for implementing the processing method of the radioactive cesium contaminated soil of this invention on a large scale, and is a figure which shows a one part process of all the process steps comprised by FIGS. It is a flowchart which shows embodiment for implementing the processing method of the radioactive cesium contaminated soil of this invention on a large scale, and is a figure which shows another one part process of all the process steps comprised in FIGS. is there. It is a flowchart which shows embodiment for implementing the processing method of the radioactive cesium contaminated soil of this invention on a large scale, and is a figure which shows another one part process of all the process steps comprised in FIGS. is there. It is a flowchart which shows embodiment for implementing the processing method of the radioactive cesium contaminated soil of this invention on a large scale, and is a figure which shows another one part process of all the process steps comprised in FIGS. is there. It is a flowchart which shows embodiment for implementing the processing method of the radioactive cesium contaminated soil of this invention on a large scale, and is a figure which shows another one part process of all the process steps comprised in FIGS. is there. 5A and 5B are schematic views showing a configuration example of the vacuum drying / forming machine 68 in FIG. 4, where FIG.

<< Embodiment 1 >>
An embodiment of the method for treating radioactive cesium-contaminated soil of the present invention will be described with reference to FIG. In FIG. 1, blocks indicated by double frames indicate work by workers, and blocks indicated by single frames indicate work by automation. Contaminated with radioactive cesium was Topsoil was scraped by region and sewers mud contaminated soil (S1), the large dust and large stones are separated in the coarse separation manual (S2) (S3). The separated large garbage and large stone are washed with high-pressure water (S4), and adhering pebbles, sand, soil, etc. are washed away. The washed large garbage and large stone can be discarded if the radiation dose is measured and the radiation dose is sufficiently reduced. If the radiation dose is not sufficiently reduced, re-cleaning is performed to reduce the radiation dose.

  The pebbles, sand, soil, etc. washed off by the high-pressure washing (S4) are collected in the water tank together with the washing water, and settled and separated (precipitation separation) in the water tank (S5). The pebbles, sand, soil, and the like separated and separated are taken out from the water tank (S6). The clean water (S7) separated in the water tank is reused for washing classification (S8).

  The pebbles, sand, earth, etc. separated from large garbage and stones by coarse separation (S2), and the pebbles, sand, earth, etc. separated by sedimentation separation (S5) (S6) can be washed, for example, using a sieve ( In S8), the particles are separated into pebbles and sand (S9) having a particle size of 53 μm or more and suspension (clay water) (S10) in which fine particles containing clay mineral having a particle size of 53 μm or less are dispersed in water. The separated pebbles and sand are drained and ventilated (S11). Exhaust gas discharged by ventilation drying is adsorbed and removed by the cesium adsorption device (S12) and released to the atmosphere (S13). The dried pebbles and sand are stored in a flexible container bag (S14), the radiation dose is confirmed (S15), and if the radiation dose is sufficiently reduced, the flexible container bag is removed from the original place (or Transported to designated places), buried in a flexible container bag and stored in a park, schoolyard, etc., drained back pebbles and sand from the flexible container bag, or reused as a cover material for highly contaminated land, etc. The final disposal is performed (S16). If the radiation dose is not sufficiently reduced, transport to a designated radioactive waste storage location for storage.

  On the other hand, the separated clay water (S10) is added with a flocculant in the water tank, and fine particles containing clay minerals are aggregated and settled (S17). The separated water (S18) separated at this time is reused for washing classification (S8). The precipitate (clay) of the fine particles that has been agglomerated and settled is taken out of the water tank (S19) and dehydrated by a dehydrator (S20). As a result, the radioactive cesium is concentrated and recovered while adhering to the clay. The separated water (S21) separated at this time is reused for washing classification (S8).

  The hydrous clay (S22) obtained by the dehydration (S20) by the dehydrator is vacuum dehydrated and dried to evaporate the water leaving enough water for extrusion (S23). The separated water (S24) separated at this time is reused for washing classification (S8). The evaporated vapor is exhausted (S25), cesium is adsorbed and removed by the cesium adsorption device (S12), and released to the atmosphere (S13).

  The dehydrated and dried clay is pressed and formed into pellets (S26). The formed pellets are dried and baked (S27), and after cooling, a glaze is further applied to the entire surface (S28), then baked and fired (S29), and ceramicized. Gases (S30, S31) generated during the uncoating and main baking are adsorbed and removed by the cesium adsorption device (S12) and released to the atmosphere (S13).

  The main-baked pellets (sintered pellets) are cooled (S32), the radiation dose is measured, and sorted according to the radiation dose (S33). The sorted sintered pellets are stored in a dedicated storage tray (pallet) for each radiation dose (S34). Further, the storage tray is hermetically stored in a storage container for each radiation dose (S35), transported to a designated location, and stored as radioactive waste (S36).

<< Experimental example >>
The inventors conducted an experiment to reduce the volume of radioactive cesium-contaminated soil by the treatment method of FIG. This experiment will be described.

《Soil samples and equipment used in the experiment》
・ Soil sample used in the experiment: Garden soil collected in Azumi-cho, Koriyama City, Fukushima Prefecture (weight before drying 346 g, volume before drying 300 cubic cm, surface dose rate 1.57 μSv / h)
・ Classifier used in cleaning classification (S8) in FIG. 1: Metal mesh sieve with openings of 500 μm, 75 μm and 53 μm conforming to JIS Z8801-1 ・ Measurement device used for measuring surface dose rate: NaI scintillation Survey meter

《Experimental procedure》
(1) Place the above three sieves with a small mesh size on top and a large mesh size on top of each other in order, and pour and wash the soil sample stirred with water from the top of the screen. Classification (step S8 in FIG. 1) is performed.
(2) Dry the pebbles and sand remaining on each sieve and measure the weight and surface dose rate, respectively.
(3) A flocculant is added to the suspension (clay water) that has passed through the entire sieve to allow the clay to settle (same step S17), the precipitated clay is taken out (same step S19), and press-molded for dehydration. Processing into pellets (step S26).
(4) Dry pellets and measure weight and dimensions and surface dose rate.
(5) The pellet is unbaked (the temperature is gradually raised from room temperature and the maximum temperature of 700 degrees Celsius is maintained for 10 minutes, and then the temperature is gradually lowered) (step S27).
(6) When the temperature of the pellet is sufficiently lowered, measure the weight and dimensions and the surface dose rate.
(7) A glaze is applied to the entire surface of the pellet (a commercially available glaze for easy baking that can be baked at 800 degrees Celsius is used as the glaze) (step S28).
(8) The glaze is dried and burned (the temperature is gradually raised from room temperature and the maximum temperature of 800 degrees Celsius is maintained for 10 minutes, and then the temperature is gradually lowered) (step S29).
(9) When the temperature of the pellet (sintered pellet) is sufficiently lowered, the weight and dimensions and the surface dose rate are measured.

"Experimental result"
The experimental results are shown in FIG. The background dose rate at the time of measuring the surface dose rate was 0.11 μSv / h.

<Discussion>
According to the experimental results of FIG. 2, the following can be said.
・ The radiation dose of pebbles and sand remaining in each sieve is sufficiently reduced. In contrast, the radiation dose of the clay after pressing remains high. Therefore, most of the radioactive cesium contained in the soil sample is extracted in a state of being incorporated in clay (pellet).
・ Much of the radioactive cesium remains in the sintered pellets even in the unbaking and the main baking.
The initial volume of the soil sample is 300 cubic cm, whereas the volume of the sintered pellet after the main baking is 33.5 cubic cm, which is reduced to a volume of about 1/9. The amount of radiation of pebbles and sand remaining in each sieve is sufficiently reduced and can be buried and stored in the original place, etc., so that final disposal such as backfilling can be performed, greatly reducing the amount to be stored as radioactive waste. it can.

<< Embodiment 2 >>
Embodiments for carrying out the method for treating radioactive cesium-contaminated soil of the present invention on a large scale are shown in FIGS. A series of processing steps according to this embodiment will be described.

Contaminated soil, such as were scraped in contaminated with radioactive cesium local surface soil or sewers mud is collected in treatment plants placed in flexible container bag 10 (S101). In the treatment plant, the contaminated soil 12 is discharged from the flexible container bag 10 and applied to the coarsely separated raw material hopper 14 with a sieve to separate large trash and large stones 18 with the sieve 16 (S102). The separated large garbage and large stone 18 are put into a washing booth 20 equipped with a sieve, washed with high-pressure water 24 supplied from a recovery water tank 36 (FIG. 6) and sprayed from a high-pressure washing machine 22, and large garbage and Pebbles, sand, soil, etc. adhering to the surface of the large stone 18 are washed away (S103). The air in the cleaning booth 20 is sucked and supplied to the exhaust cesium adsorption tower 52 (FIG. 7). The washed large trash and large stone 18 ′ can be discarded as they are if the radiation dose is measured and the radiation dose is sufficiently reduced. If the radiation dose is not sufficiently reduced, re-cleaning is performed to reduce the radiation dose. The pebbles, sand, soil, etc. washed away by the high pressure washing are collected in the lower hopper 28 through the sieve 26 together with the washing water. The water containing pebbles, sand, soil and the like collected in the hopper 28 is discharged from the lower part of the hopper 28 and transferred to the raw material washing tank 32 by the transfer pump 30 (sand pump) (S104). On the other hand, pebbles, sand, soil, and the like that have passed through the sieve 16 of the coarsely separated raw material hopper 14 are collected in the hopper 34 thereunder and mixed with water supplied from the recovery water tank 36 (FIG. 6). The mixed water is discharged from the lower portion of the hopper 34 by the discharge screw 38 and transferred to the raw material cleaning tank 32 (S105).

  In the raw material washing tank 32, water supplied from the recovery water tank 36 (FIG. 6) is added to pebbles, sand, soil, etc. transferred from the hoppers 28 and 34, and stirred by the stirrer 40 (S106). The mixed water in which pebbles, sand, soil, etc. are stirred is discharged from the lower part of the raw material washing tank 32, and a part (for example, 20% of the discharged amount from the raw material washing tank 32) is a wet classifier by the transfer pump 42 (sand pump). 44 (S107), and the remainder is returned to the raw material washing tank 32 by the circulation pump 46 (sand pump) (S108). By this rubbing of the sand in the mixed water with each other, the soil adhering to the surface of the sand can be removed sufficiently.

  The wet classifier 44 adds the water supplied from the recovered water tank 36 (FIG. 6) to the transferred mixed water and further mixes the mixture, and the mixed water contains granular materials having a large particle size such as pebbles and sand, and clay minerals. Classification is made into a suspension (clay water) in which fine particles are dispersed in water (S109). As the wet classifier 44, various types such as sedimentation classification, mechanical classification, hydraulic classification, and centrifugal classification can be adopted. The clay water is supplied to the flocculant mixing tank 60. Granules such as pebbles and sand are supplied to the cleaning trombol 48. The cleaning trommel 48 incorporates an inclined rotating net drum, and is washed with water supplied from the recovery water tank 36 (FIG. 6) while putting granular materials such as pebbles and sand into the rotating net drum and rotating ( S110). The washed granular materials such as pebbles and sand are supplied to the rotary dryer 50. The rotary dryer 50 has a built-in rotating drum and feeds hot air into the rotating drum while rotating the granular material such as pebbles and sand into the rotating drum to dry the granular materials such as pebbles and sand ( S111). By this drying, it is possible to prevent the residual moisture containing radioactive cesium from leaking out and leaking out as contaminated water after final disposal such as burying storage and backfilling, and causing secondary contamination. The exhaust (used hot air) from the rotary dryer 50 is supplied to the exhaust cesium adsorption tower 52 (FIG. 7). The dried pebbles and sand and other particulate matter discharged from the rotary dryer 50 are measured for the radiation dose, and if the radiation dose is sufficiently reduced, they are packed in the flexible container bag 51 (S112) for transportation. Transported to the original location (or designated location) by truck 54, buried in a flexible container bag, stored in a park or school yard, backfilled by discharging pebbles and sand from the flexible container bag, highly contaminated land, etc. It is reused as a surface cover material or the like for final disposal (S113). If the radiation dose is not sufficiently reduced, transport to a designated radioactive waste storage location for storage.

  The fine particles containing clay minerals washed away from the granular materials such as pebbles and sand by washing with the washing trommel 48 flow into the precipitation separation tank 56 through the mesh of the rotating mesh drum of the washing trommel 48 together with the washing water. The sedimentation separation tank 56 accumulates the water falling from the washing trommel 48 and precipitates and separates the fine particles containing the clay mineral (S114). The sludge extraction pump 58 extracts sludge water from the bottom of the precipitation separation tank 56 and supplies it to the coagulant mixing tank 60. The water pump 62 collects the supernatant from the upper part in the precipitation separation tank 56 and supplies it to another precipitation separation tank 64. The precipitation separation tank 64 precipitates and separates finer particles contained in the supplied supernatant liquid by taking a longer time than the precipitation separation tank 56. When an appropriate amount of sludge is precipitated at the bottom of the settling tank 64, the sludge is transferred to the coagulant mixing tank 60. The supernatant liquid in the sedimentation separation tank 64 is returned to the recovered water tank 36 (FIG. 6) and reused.

  The flocculant mixing tank 60 mixes and stirs the flocculant with the clay water and sludge water supplied from the wet classifier 44 and the precipitation separation tanks 56 and 64, and fine particles containing clay minerals contained in the clay water and sludge water. To increase the particle size and facilitate separation of fine particles containing clay mineral (S115). The clay water discharged from the bottom of the flocculant mixing tank 60 is supplied to the automatic centrifuge 66 shown in FIG. The automatic centrifuge 66 filters the clay water supplied to the built-in rotary cylinder with a filter cloth to dehydrate it, and separates the fine particles containing clay mineral (S116). The fine particles (dehydrated clay) 21 containing the separated clay mineral are scraped off with a knife and put into a vacuum drying / forming machine 68.

  The vacuum drying / molding machine 68 deaerates the dehydrated clay 21, extrudes it, cuts it, and processes it into pellets 76 (S117). A structural example of the vacuum drying / forming machine 68 is shown in a schematic sectional view in FIG. The vacuum drying / molding machine 68 is a so-called vacuum extrusion molding machine. The dehydrated clay 21 is supplied to the raw material inlet 23 and supplied to the upper extruder 25. The upper stage extruder 25 includes an extrusion screw 29 driven by a motor 27 with a speed reducer, and conveys the dehydrated clay 21 in the axial direction of the extrusion screw 29. The transported dehydrated clay 21 is pushed out from each hole of a perforated plate (resistive honeycomb plate) 31 disposed at the end of the upper extruder 25 and separated into small blocks 21a. The outlet of the perforated plate 31 communicates with the upper part of the vacuum chamber 35 of the deaeration tank 33, and the small blob 21 a is put into the vacuum chamber 35. The vacuum chamber 35 is evacuated and decompressed by a vacuum pump (not shown). The exhaust from the vacuum chamber 35 sucked by the vacuum pump is supplied to the exhaust cesium adsorption tower 52 (FIG. 7). The deaeration tank 33 has a double structure in which the vacuum chamber 35 is surrounded by a casing 37, and steam or hot water is caused to flow into a space 39 between the vacuum chamber 35 and the casing 37. The small lump 21a put into the vacuum chamber 35 is accumulated in the lower part of the vacuum chamber 35, and is stirred by the stirring paddle 45 driven by the motor 43 with a speed reducer while being heated by the heat of steam or hot water, and the small lump 21a The air contained inside is deaerated. The stirring paddle 45 is not always necessary and may be omitted. The deaerated clay (deaerated clay) 21 b is supplied to a lower extruder 47 communicating with the lower part of the vacuum chamber 35. The lower extruder 47 includes an extrusion screw 53 driven by a motor 49 with a speed reducer, and conveys the degassed clay 21b forward in the axial direction of the extrusion screw 53. The conveyed degassed clay 21b is extruded from a round hole 55a of a cutting die (single hole plate) 55 arranged at the end of the lower extruder 47 and formed into a continuous cylindrical shape. A turning cutter 57 is disposed at the exit of the round hole 55 a of the cutting die 55. The revolving cutter 57 is rotationally driven by a motor 59 intermittently every half rotation by a motor 59, and cuts the deaerated clay 21b formed into a columnar shape by a predetermined size, and has a predetermined diameter and thickness. It is processed into a round pellet 76.

  The pellets 76 of the deaerated clay 21b discharged from the vacuum drying / forming machine 68 are picked up one by one by the alignment robot 78 and aligned on the pellet tray 80 (S118). The pellet tray 80 in which the pellets 76 are arranged is put into the unfired baking furnace 82 of FIG. 5, and the temperature is gradually raised and unbaked at a predetermined temperature for a predetermined time (for example, 700 degrees Celsius for 10 minutes) (S119). The exhaust from the unfired baking furnace 82 is supplied to the exhaust cesium adsorption tower 52 (FIG. 7). The pellet 76 ′ after the unglazed baking is cooled and transported on the belt conveyor 84, and when passing under the glaze application device 86, the glaze sprayed from the glaze application device 86 (for example, glaze for easy baking) is pellet 76. It is applied to the upper surface and side surface of 'and further dried to the extent that no glaze is attached even if it is held by hand while passing through the drying heater booth 88 (S120). Thereafter, the pellet 76 ′ is reversed and placed on the belt conveyor 84 and conveyed again. When passing under the glaze application device 86, the glaze sprayed from the glaze application device 86 is the upper surface of the pellet 76 ′ (previous time). Is applied to the lower surface and the side surface of the coating and further dried to the extent that the glaze does not stick even if it is held by hand while passing through the drying heater booth 88. As a result, the glaze is applied to the entire surface of the pellet 76 '.

  The pellets 76 ′ coated with the glaze are aligned on the pellet tray 80 again. The pellet tray 80 in which the pellets 76 'are arranged is put into the main baking furnace 90, and the temperature is gradually raised and main baking is performed at a predetermined temperature for a predetermined time (for example, 700 degrees Celsius for 10 minutes) (S121). Exhaust gas discharged from the main baking and firing furnace 90 is supplied to an exhaust cesium adsorption tower 52 (FIG. 7). Note that the main baking furnace 90 can also be used as the unfired baking furnace 82.

  Pellets (sintered pellets) 76 ", which have been baked after completion of the main baking, are picked up one by one from the pellet tray 80 by the alignment robot 92 and transported on the belt conveyor 94. The pellets are transported by the belt conveyor 94. The individual identification information is printed on the upper surface or the like while the sintered pellet 76 "passes through the individual identification printing device 96 on the way (S122). The individual identification information includes, for example, the soil collection location, the collection date, the individual number, etc., from which each sintered pellet 76 ″ is based. The sintered pellet 76 ″ on which the individual identification information is printed continues to the belt conveyor. 94, the radiation dose for each sintered pellet 76 "is measured while passing through the automatic dose measurement sorter 98 (S123). The automatic dose measurement sorter 98 is used in parallel with the radiation dose measurement. The individual identification information of the sintered pellet 76 ″ is read, and the measured radiation dose is combined with the individual identification information and transmitted to the alignment robot 100. The alignment robot 100 reads the identification information of the sintered pellets 76 ″ discharged from the automatic dose measurement sorter 98, and according to the radiation dose measured for the sintered pellets 76 ″, the drum cans 102 (for example, high dose, medium dose) The dose is classified and stored (three types of dose and low dose) (S124). By storing by dose, management processing by attenuation of radiocesium radioactivity can be performed for each storage container (drum drum 102 by dose).

  The dose-dependent drum can 102 contains a pallet-shaped drum separator 104 made of resin, metal, etc., and the sintered pellets 76 ″ are arranged in a line in the individual storage spaces in the drum separator 104 one by one. When the sintered pellets 76 ″ are accommodated one by one in the entire accommodating space of one drum separator 104 and the drum separator 104 becomes full, an empty drum separator 104 is accommodated thereon, and further sintered pellets are stored. 76 "is stored. The upper drum separator 104 is supported on the lower drum separator 104, and a sintered pellet 76" is accommodated in the space therebetween. Each sintered pellet 76 "can be stored and stored in a separate storage space of the drum separator 104, and storage efficiency can be improved, and since the sintered pellets 76" are not in contact with each other, the sintered pellets 76 "are prevented from being damaged. The dose-dependent drum can 102 filled with the sintered pellets 76 ″ is sealed, placed on the radioactive waste transporting vehicle 106, and transported to a predetermined radioactive waste storage place for storage (S125). .

  The recovered water tank 36 shown in FIG. 6 recovers and stores the supernatant liquid in the precipitation separation tank 64 (FIG. 3), and the stored water passes through the recovered water supply pump 108 to the coarsely separated raw material hopper 14, the high pressure washer 22, and the raw material cleaning. It supplies to the tank 32, the wet classifier 44, and the washing | cleaning trommel 48 (all are FIG. 3). In this way, the treated water is circulated and reused in the treatment system and is not discharged outside the treatment system. However, since the amount of water to be evaporated in the processing system decreases, the water level in the recovered water tank 36 is monitored, and the recovered water tank 36 is replenished with the reduced amount of water. Moreover, the radiation amount of circulating water is constantly monitored, and when the radiation amount becomes higher than a predetermined value, the circulating water is purified by a cesium adsorption device and then reused or discharged externally.

  The exhaust cesium adsorption tower 52 shown in FIG. 7 is filled with a cesium adsorbent such as zeolite or Prussian blue. The exhaust fan 111 is exhausted from the processing system (specifically, the cleaning booth 20 and the rotary dryer 50 in FIG. 3, the vacuum drying / forming machine 68 in FIG. 4, the unglazed firing furnace 82 and the drying heater booth 88 in FIG. 5) All or most of the gas, steam, etc. discharged from the main baking and firing furnace 90 etc. are recovered and passed through the exhaust cesium adsorption tower 52 to adsorb and remove the cesium contained in the exhaust by the cesium adsorbent. To purify the exhaust. The purified exhaust gas is discharged from the exhaust port 113 to the atmosphere. Moreover, the whole processing equipment shown in FIGS. 3 to 7 is placed in a sealed indoor space, the indoor air is filtered through a cesium removal filter and released to the atmosphere, and fresh outdoor air is introduced indoors for overall ventilation. By doing so, we will try to preserve the indoor environment.

10,51 ... flexible container bag, 12 ... soil contaminated with radioactive cesium, 14 ... rough separation material hopper, 18 ... large dust and large stones, 20 ... washing booth, 32 ... raw material cleaning tank, 36 ... recovery water tank, 44 ... wet classifier, 48 ... washing trommel, 50 ... rotary dryer, 52 ... exhaust cesium adsorption tower (cesium adsorption device), 56 ... precipitation separation tank, 60 ... flocculant mixing tank, 64 ... precipitation separation tank, 66 ... automatic centrifugation Separator 68 ... Vacuum drying / molding machine 76 ... Pellets (lumps) 76 '... Unbaked pellets (lumps) 76 "... Mainly baked pellets (lumps) (sintered pellets) 82 ... Unglazed firing Furnace, 86 ... Glaze coating device, 90 ... Main baking oven, 96 ... Individual identification printing device, 98 ... Automatic dose measurement sorter, 102 ... Drum can (storage container) by dose, 104 ... Drum separator (Pallet)

Claims (11)

A first step of separating microparticles containing clay minerals from surface soil scraped in an area contaminated with radioactive cesium;
A second step of solidifying the separated microparticles into a mass of the separated microparticles ;
A third step of uncooking the mass;
A fourth step of applying glaze to the unbaked mass;
A method for treating cesium-contaminated soil, comprising: a fifth step of subjecting the lump coated with the glaze to main baking. A sixth step of measuring the amount of radiation emitted from the main-baked mass;
The cesium-contaminated soil treatment method according to claim 1, further comprising: a seventh step of separating the lump whose radiation dose has been measured according to the radiation dose and storing the lump in a storage container. The seventh step includes
Using a pallet having an accommodation space for individually accommodating the lumps, and storing each lumps in each accommodation space of the pallet;
A step of stacking and storing the plurality of pallets each containing the lump in the storage container,
3. The method for treating cesium-contaminated soil according to claim 2, wherein the respective lump is accommodated in the storage container without contacting each other.   The method for treating cesium-contaminated soil according to any one of claims 1 to 3, further comprising an eighth step of adding individual identification information to the main-baked lump. 9. The method according to claim 1, further comprising drying a granular material including pebbles and sand left after separating the fine particles including the clay mineral from the surface soil scraped in the area contaminated with the radioactive cesium. To 4. The method for treating cesium-contaminated soil according to any one of items 1 to 4. The first step is a step of extracting a suspension containing fine particles containing the clay mineral by washing the surface soil collected in the radioactive cesium-contaminated area with water, and from the suspension. Separating the fine particles containing the clay mineral,
The cesium according to any one of claims 1 to 5, wherein the water left by the separation of the fine particles including the clay mineral is reused for cleaning other surface soils collected in an area contaminated with radioactive cesium. How to treat contaminated soil.   The method for treating cesium-contaminated soil according to any one of claims 1 to 6, further comprising a tenth step of releasing the gas and exhaust gas generated in the treatment into the atmosphere after being purified by a cesium adsorption device.   The method for treating cesium-contaminated soil according to any one of claims 1 to 7, wherein the glaze is a glaze usable for easy baking.   The method for treating cesium-contaminated soil according to any one of claims 1 to 8, wherein the unglazed baking and the main baking are performed at a temperature of easy baking.   A first step of separating microparticles containing clay minerals from surface soil scraped in an area contaminated with radioactive cesium;
  A second step of solidifying the separated microparticles into a mass of the separated microparticles;
  A step of baking and solidifying the mass to form a sintered body;
  A method for treating cesium-contaminated soil.   The method for treating cesium-contaminated soil according to any one of claims 1 to 10, further comprising a step of scraping the surface soil in an area contaminated with the radioactive cesium before the first step.

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