JP5850779B2 - Soil treatment / storage system containing radioactive cesium and treatment / storage method using the same - Google Patents

Description

  The present invention relates to a soil treatment / storage system containing radioactive cesium and a method for treating / storage soil containing radioactive cesium using the same.

Most of radioactive cesium such as cesium 134 and cesium 137 is concentrated in the surface layer portion in a stable state combined with clay in the soil.
For this reason, by removing the surface layer of the soil, the radioactivity concentration (space radiation dose) at the site where the surface layer has been removed can be greatly reduced.
Therefore, although the removal operation | work of the surface layer (contaminated soil) of the soil containing radioactive cesium is implemented, it has become a big problem to secure the place which installs the intermediate storage facility for storing contaminated soil.

JP-A-6-343948

  The present invention effectively treats soil containing radioactive cesium and does not generate secondary waste, thereby reducing the burden of treatment and storage, and a system for treating and storing soil containing radioactive cesium, It is an object to provide a method for treating and storing soil containing radioactive cesium using the same.

As a means for solving the problems, the present invention
A soil treatment / storage system comprising radioactive cesium containing radioactive cesium for treating soil composed of small-diameter particles containing radioactive cesium obtained by treating soil containing radioactive cesium,
Wet for adding water to soil consisting of small particles containing radioactive cesium that has been dry-classified and separating it into a liquid containing relatively small particles of soil and a soil hydrate containing relatively large particles of soil A classification device;
A first dehydrating and drying apparatus for dehydrating and drying the water-containing material separated by the wet classifier;
A microfilter device (MF device) for processing the liquid separated by the wet classifier;
A second dehydrating and drying apparatus for dehydrating and drying the concentrate separated by the MF apparatus;
A reverse osmosis membrane device (RO device) for treating the permeate treated with the MF device;
It has an incinerator for burning combustibles,
Each of the devices is connected by a line,
Furthermore, it has a line for returning the water separated by the first dehydration drying apparatus and the second dehydration drying apparatus to the MF apparatus,
The RO device and the incinerator are connected by a concentrate line that sends the concentrate produced in the RO device to the incinerator,
RO equipment and wet classifier are connected by a line that sends permeate generated in RO equipment to the wet classifier, the soil treatment / storage system containing radioactive cesium, and the soil containing radioactive cesium using the system Provide processing and storage methods.

The present invention provides other means for solving the problems,
Treating soil containing radioactive cesium, soil having relatively high radioactivity concentration consisting of small-diameter particles containing radiocesium, soil having relatively low radioactivity concentration consisting of particles larger than soil consisting of the small-diameter particles, And initial separation means for separating into combustibles,
Provided is a soil treatment / storage system containing radioactive cesium, and a method for treating / storage soil containing radioactive cesium using the initial separation means, which is a movable dry classification means mounted on a vehicle.

By carrying out the treatment / storage method using the treatment / storage system of the present invention, it is possible to effectively treat / store soil contaminated with radioactive cesium generated by decontamination work. The storage burden can be reduced.
Further, according to the present invention, since no additives such as chemicals (flocculating agents, stripping agents, adsorbents) are used, secondary waste that is expected to be generated in large quantities is not generated by using chemicals. Therefore, since the storage cost of chemicals and secondary waste can be omitted, the treatment / storage cost of contaminated soil can be greatly reduced.

  According to another means for solving the problem, on-site waste water treatment can be made unnecessary by preliminarily performing dry classification (initial separation means) of the soil at the temporary storage site of the contaminated soil. By performing the initial separation means, it is possible to significantly reduce the soil to be processed in the subsequent stage. As a result, the construction and operation costs of equipment for processing and storage can be greatly reduced.

The conceptual diagram of the processing / storage system of the soil containing the radioactive cesium of this invention.

<Processing and storage system>
The soil treatment / storage system containing radioactive cesium of the present invention will be described with reference to FIG.
In areas contaminated with radioactive cesium, contaminated soil containing radioactive cesium that must be treated and stored in large quantities is generated in various places by stripping the surface layer of soil containing radioactive cesium.
The processing / storage system of the present invention processes a large amount of contaminated soil by a processing / storage system comprising a combination of an on-site processing (mobile equipment processing) system and a fixed equipment processing system.

[On-site processing (mobile equipment processing) system]
Contaminated soil generated by the removal operation includes silt (2 to 20 μm), clay (about 2 μm or less), a relatively small particle size, sand (fine sand 20 to 200 μm, coarse sand 200 μm to 2 mm), Combustible materials such as twigs and fallen leaves are included, as well as those having a relatively large particle size such as reki (one having a larger particle size than sand).
In addition, radioactive cesium adheres to clay particles having a very small particle size in the soil at a high density.
Therefore, the initial separation means (sieving means) separates according to the following standard (approximate standard).
(1) A relatively small particle size such as silt or clay having a particle size of about 100 μm or less (for example, a radioactivity concentration of 8000 Bq / kg or more is a guide).
(2) Leki with a particle size exceeding 100 μm, sand having a relatively large particle size such as sand (for example, a radioactive concentration of less than 8000 Bq / kg is a guide).
(3) Combustible materials derived from plants such as twigs, fallen leaves, weeds, lawns, and combustible materials derived from animals such as dead carcasses of insects (however, soil may be included with the combustible materials).

(Initial separation means)
The initial separation means 10 used in the on-site processing (mobile equipment processing) system processes the contaminated soil on the spot, and is a movable dry classifying means (sieving means) 12 mounted on the vehicle 11. is there.
In addition, it is desirable that the periphery of the sieving means 12 is covered with a cover 13 to prevent scattering of small-diameter particles during processing. The cover 13 can be made of cloth or resin sheet.
Thus, by using the initial separating means 10 as the movable sieving means 12 mounted on the vehicle 11, it is possible to perform on-site processing in a place where contaminated soil exists.
Examples of the sieving means 12 used as the initial separating means 10 include a trommel and a dry cyclone.
The trommel (rotary screen) includes a cylindrical trommel and a conical trommel.

[Fixed equipment processing system]
The fixed equipment treatment system treats (1) soil with a relatively small particle size (soil made of small diameter particles containing radioactive cesium) and (3) combustible material separated by an on-site treatment (mobile equipment treatment) system. System.

[Wet classifier]
The wet classifier 21 adds water to soil composed of small-diameter particles containing radioactive cesium, and separates it into a liquid containing a relatively small-sized particle soil and a soil hydrate containing a relatively large-sized particle soil. It is a device.
The liquid containing relatively small-sized particles of soil contains small-sized particles to which radioactive cesium adheres at a high density. However, since it contains a large amount of water, the radioactivity concentration itself is low. . However, when water is removed, it will contain a high concentration of radioactivity.
The radioactivity concentration of the soil hydrate containing relatively large-diameter soil is sufficiently lower than the radioactivity concentration after removing the water.

As the wet classifier 21, a sieve classifier, a wet cyclone, or the like can be used.
Examples of the wet classifier include TR-5, TR-10, T-10, T-5 type super cron manufactured by Murata Kogyo Co., Ltd., Hydroplex AHP manufactured by Hosokawa Micron Co., Ltd., manufactured by Uji Electric Chemical Co., Ltd. A wet classifier, a sieving classifier, or the like can be used.
The wet classifier 21 is connected to the MF apparatus 22 through a line 31 for sending a liquid containing radioactive cesium.

[MF equipment]
The MF apparatus 22 is for processing the liquid separated by the wet classifier 21.
The MF apparatus 22 separates particles having a size of about 1 μm or more (over 1 to 30 μm) as a concentrated liquid and particles having a size of 1 μm or less (including clay particles to which radioactive cesium particles are attached) as a permeated liquid. .
A commercially available MF device can be used as the MF device 22. For example, an MF apparatus equipped with Microza MF, which is a hollow fiber membrane manufactured by Asahi Kasei Chemicals Corporation, can be used.
The MF device 22 is connected to the RO device 23 by a line 32 for sending permeate.
In the line 32, an ultrafiltration membrane device (UF device) can be further installed. The load on the RO device 23 can be reduced by installing a UF device and removing those having a large molecular weight.

The RO device 23 is for processing the permeate separated by the MF device 22, and the RO device pump and the RO membrane module are integrated.
As the RO device 23, a commercially available RO device can be used.
The RO device 23 separates water (including radioactive cesium particles) of 1 μm or less contained in the permeate separated by the MF device 22 from water, and the permeate (water) is separated from the line 33 by a wet classifier. 21 is returned.
The RO device 23 is connected to the incinerator 27 through a line 35 for sending the concentrate.

A permeate tank 24 can be installed in the line 33. The permeate treated by the RO device 23 is stored in the permeate tank 24 and returned to the wet classifier 21, and can also be used as RO membrane cleaning water for the membrane of the RO device 23.
The RO membrane cleaning is performed using the RO membrane cleaning line 34 using an RO membrane cleaning pump (not shown). The washing waste water is returned to the line 31 using a line (not shown).

The wet classifier 21 is connected to the first dehydrator / dryer 25 via a line 36.
The first dehydrating and drying device 25 is for dehydrating and drying the water-containing material separated by the wet classifying device 21.
As the first dehydrating and drying device 25, a known filter press (preferably a fully automatic filter press) can be used.
The first dehydrating and drying apparatus 25 and the line 31 are connected by a line 37 and a line 40 for returning dehydrated water.

The MF device 22 is connected to the second dehydration drying device 26 through a line 38.
The second dehydrating / drying device 26 is for dehydrating and drying the concentrated liquid separated by the MF device 22.
As the second dehydrating and drying device 26, a known filter press (preferably a fully automatic filter press) can be used.
The second dehydrating and drying apparatus 26 and the line 31 are connected by a line 39 and a line 40 for returning dehydrated water.
In addition, 51-55 are opening / closing valves which consist of electromagnetic valves etc., and are installed in each line as needed.

The incinerator 27 is for incinerating combustibles (containing radioactive cesium) separated by an on-site treatment (mobile equipment treatment) system.
The incinerator 27 includes a fly ash exhaust line provided with a filter having at least a ceiling surface as an outlet, a supply means for concentrated liquid produced by the RO device, and a means for taking out the incineration ash.
In addition, a means for supplying an auxiliary combustor (such as kerosene) can also be provided.

The exhaust line 41 is for collecting fly ash generated in the incinerator 27 and collecting the dust by the filter 28. A commercially available bag filter can be used as the filter 28.
Cesium in combustible materials (from plants and animals) is mostly combined with organic matter, and when incinerated in the incinerator 27, it is contained in the fly ash floating in the incinerator 27, so the exhaust line In 41, radioactive cesium is collected by the bag filter 28.
The incinerator 27 is preferably provided with means for supplying fresh water (such as tap water or groundwater) installed in the vicinity of the ceiling surface.

The means for supplying the concentrated liquid (containing high-concentration radioactive cesium) generated in the RO device 23 is means for supplying the concentrated liquid as cooling water into the incinerator 27. The supply means is preferably installed so that it can be supplied from an intermediate position of the height position of the incinerator 27 to the lower side.
Since the radioactive cesium in the concentrated liquid produced in the RO device 23 exists in a state of being combined with clay (silica, alumina, etc.), it is combined with the clay when the concentrated liquid is supplied into the incinerator 27. Most of the cesium accumulates on the bottom as incinerated ash. (Some will migrate to fly ash.)

<Processing and storage method using processing and storage system>
A processing / storage method using the processing / storage system of the present invention will be described step by step.
[Initial separation process]
As the initial separation means 10, the movable sieving means 12 mounted on the vehicle 11 is used to separate the contaminated soil into the following three types.
(1) A relatively small particle size such as silt or clay having a particle size of about 100 μm or less (activity level is 8000 Bq / kg or more) (soil with relatively high activity concentration).
(2) Leki having a particle size exceeding 100 μm, sand having a relatively large particle size such as sand (activity level is less than 8000 Bq / kg) (soil having a relatively low activity level).
(3) Combustible materials derived from plants such as twigs, fallen leaves, weeds, lawns, and combustible materials derived from animals such as dead carcasses of insects (however, soil may be included with the combustible materials).

(2) The soil with a relatively low radioactivity concentration is stored in a state of being placed in a container such as a flexible container at the treatment site after radioactivity analysis.
In addition, the radioactive concentration of (2) soil having a particle size exceeding 100 μm, sand having a relatively large particle size (soil with relatively low activity concentration) is high by the first separation operation. In case (when the radioactivity concentration exceeds 8000 Bq / kg), it is transferred to a volume reduction facility with water treatment equipment and washed with water.
The soil having a relatively high radioactive concentration in (1) and the combustible material in (3) are transported to a fixed facility processing system by a transportation means such as a truck and processed.

[Wet classification process]
Using the wet classifier 21, water is added to soil composed of small-diameter particles containing radioactive cesium (soil having a relatively high radioactivity concentration) to contain soil of relatively small-diameter particles (particle size of 30 μm or less). It is separated into a soil hydrate containing a liquid having a particle size of about 30 μm to 100 μm.
The ratio of soil and water composed of small-diameter particles containing radioactive cesium is preferably 10 parts by mass or more of water with respect to 1 part by mass of the soil.
The liquid containing relatively small-sized particles of soil contains small-sized particles to which radioactive cesium adheres at a high density. However, since it contains a large amount of water, the radioactivity concentration itself is low. . However, when water is removed, the radioactivity concentration increases.
The radioactivity concentration of the soil hydrate containing relatively large-diameter soil is sufficiently lower than the radioactivity concentration after removing the water.

During the treatment operation, the permeate generated in the RO treatment step is used as the water used in the wet classification step, but tap water or groundwater is used at the start of the operation.
The liquid containing radioactive cesium is sent from the line 31 to the MF device 22.
The hydrated product is sent from the line 36 to the first dehydrating / drying device 25 and dehydrated and dried to be separated into a dried product and water.
Since the dry matter has a relatively low radioactivity concentration, it is taken out from the lines 42 and 44, and then stored after analysis of the radioactivity concentration.
The dehydrated water is returned from the lines 37 and 40 to the line 31 and processed by the MF device 22.

[MF treatment process]
Using the MF apparatus, the liquid containing radioactive cesium separated in the wet classification process is processed to separate the permeated liquid and the concentrated liquid.
In the MF treatment step, the liquid is separated into a permeate (particles having a high radioactive cesium concentration) containing particles of about 1 μm or less and a concentrate (a liquid having a low radiocesium concentration) containing particles of about 1 μm to 30 μm or less.
The permeate is sent from the line 32 to the RO device 23.
The concentrated liquid is sent from the line 38 to the second dehydrating / drying apparatus 26, dehydrated and dried, and separated into a dried product and water.
Since the dried product has a lower radioactivity concentration than particles of 1 μm or less, it is taken out from the lines 43 and 44, and the radioactivity concentration is analyzed and stored.
The dehydrated water is returned from the lines 39 and 40 to the line 31 and processed by the MF apparatus 22.

[RO treatment process]
Using the RO device 23, the permeate obtained in the previous step is processed and separated into a permeate (water) and a concentrate (including particles having a particle size of 1 μm or less). In the RO treatment step, RO membrane cleaning is performed as appropriate in order to maintain filtration performance.
Radioactive cesium is contained in the concentrate and is substantially not contained in the permeate.
The permeate is returned from the line 33 to the wet classifier 21 process and used in the wet classification process.
The concentrated liquid is supplied from the line 35 into the incinerator 27.

[Incineration process]
Using the incinerator 27, the plant-derived and animal-derived combustible material (3) separated in the initial separation step is incinerated.
Most of the radioactive cesium contained in plant-derived and animal-derived combustibles is combined with organic matter. When incinerated in the incinerator 27, most of the radioactive cesium flies from the incinerated ash. Move into ash. For this reason, the fly ash is discharged from the exhaust line 41, and radioactive cesium is collected by the bag filter 28 in the middle thereof.
At this time, water is sprayed from a supply means of fresh water (not contaminated with radioactive cesium such as tap water or groundwater, or contaminated water at a very low level without any problem) installed near the ceiling surface. This spray of fresh water lowers the temperature of the exhaust line 41 and reduces the thermal effect on the bag filter 28.

The concentrated liquid (liquid containing clay fine particles with high radioactivity concentration) generated in the RO treatment process is supplied as cooling water from the line 35 into the incinerator 27. This concentrated water is supplied from the middle position of the incinerator 27 to the lower side.
Since radioactive cesium in the concentrated liquid produced in the RO treatment process exists in a state of being strongly bonded to the clay component, when the concentrated liquid is supplied into the incinerator 27, much remains in the incinerated ash. However, since the particle size is small, what flows to the off-gas side (exhaust line 41 side) during spraying in the furnace moves to the fly ash side.
The incinerated ash deposited on the bottom surface is taken out from the line 45 and stored in a container that can shield radiation.
Incineration ash and fly ash generated in the incinerator 27 contain high concentrations of radiation cesium, and are stored in a state where radiation is shielded.

In the processing / storage method using the processing / storage system of the present invention, the following effects can be obtained.
(I) In the contaminated soil (excluding combustible materials), (1) soil with a relatively high radioactive concentration (about 10% by volume) and (2) By separating the soil with a low active concentration (about 90% by volume) and storing the soil with a relatively low radioactive concentration in (2) on site, The load can be greatly reduced, and safety can be ensured by separating and treating soil with a high radioactivity concentration by covering with a cover to prevent scattering of small-diameter particles.
(II) By carrying out the wet separation step, MF treatment step, and RO treatment step following the initial separation step, a permeate substantially free of radioactive cesium (permeate of the RO treatment step) and a concentration containing radioactive cesium at a high concentration It can isolate | separate into a liquid (concentrated liquid of RO processing process). Since the permeated liquid can be reused as water added in the wet separation process, it is not discharged out of the processing / storage system.
(III) Since water (containing radioactive cesium) dehydrated from the water-containing material (containing low concentration radioactive cesium) obtained in the wet separation process is processed in the processing / storage system,・ It is not discharged outside the storage system. The dehydrated and dried product of the water-containing product has a low radioactive cesium concentration, and is stored after analyzing the radioactivity concentration.
(IV) Dehydrated water (containing radioactivity) is treated in the treatment / storage system from the concentrated liquid (containing soil particles with low radioactivity concentration) obtained in the MF treatment process. Therefore, it is not discharged outside the processing / storage system. The dehydrated dried product of the concentrated liquid has a low radioactive cesium concentration, and is stored in a state where radiation shielding treatment is performed as necessary.
(V) Although the ash (incineration ash, fly ash) generated in the incinerator contains high-concentration radiation cesium, they are all collected and stored in a state of radiation shielding.
As described above, by implementing the treatment / storage method using the treatment / storage system of the present invention, most of the contaminated soil that has been removed is buried directly at the site or near the site, or the soil having a low radioactive concentration is directly buried, or It can be stored in containers such as plastic containers and drums. By doing so, the amount of soil with high radioactivity concentration is reduced. And the burden of the intermediate storage facility which stores the soil with high radioactivity which needs processing and storage can be reduced greatly.
Further, the treatment / storage system is a closed system, and radioactive cesium is not scattered during the treatment or water containing the radioactive cesium leaks out and is not discharged out of the treatment / storage system.

10 Initial separation means 10
DESCRIPTION OF SYMBOLS 12 Sieve means 21 Wet classifier 22 MF apparatus 23 RO apparatus 25 1st drying apparatus 26 2nd drying apparatus 27 Incinerator 28 Bag filter

Claims (5)

A soil treatment / storage system comprising radioactive cesium containing radioactive cesium for treating soil composed of small-diameter particles containing radioactive cesium obtained by treating soil containing radioactive cesium,
Wet for adding water to soil consisting of small particles containing radioactive cesium that has been dry-classified and separating it into a liquid containing relatively small particles of soil and a soil hydrate containing relatively large particles of soil A classification device;
A first dehydrating and drying apparatus for dehydrating and drying the water-containing material separated by the wet classifier;
A microfilter device (MF device) for processing the liquid separated by the wet classifier;
A second dehydrating and drying apparatus for dehydrating and drying the concentrate separated by the MF apparatus;
A reverse osmosis membrane device (RO device) for treating the permeate treated with the MF device;
It has an incinerator for burning combustibles,
Each of the devices is connected by a line,
Furthermore, it has a line for returning the water separated by the first dehydration drying apparatus and the second dehydration drying apparatus to the MF apparatus,
The RO device and the incinerator are connected by a concentrate line that sends the concentrate produced in the RO device to the incinerator,
A soil treatment and storage system containing radioactive cesium, in which an RO device and a wet classifier are connected by a line that sends permeate generated in the RO device to the wet classifier. The incinerator is a fly ash exhaust line equipped with a filter having at least a ceiling surface or a wall surface in the vicinity thereof as an outlet;
Means for taking out incinerated ash from the bottom surface or the wall surface in the vicinity thereof, and
The processing / storage system for soil containing radioactive cesium according to claim 1, further comprising means for supplying concentrated liquid generated in the RO device, which is installed below an intermediate position of the incinerator height. . A method for treating and storing soil containing radioactive cesium using the soil treating and storing system according to claim 1 or 2,
Using a wet classifier, water is added to the soil composed of small-sized particles containing radioactive cesium that has been dry-classified, so that a liquid containing relatively small-sized particles and a soil containing relatively large-sized particles are contained. Wet classification process to separate into hydrated substances,
An MF treatment step of treating the liquid separated in the wet classification step by using an MF apparatus to separate the permeate and the concentrated solution;
It has RO treatment process using RO device to process the permeate obtained in the previous process and separate it into permeate and concentrate,
Furthermore, as a process accompanying each said process,
The first dehydrating and drying apparatus is a step of dehydrating and drying the hydrated material separated in the wet classification step to separate the dried product and water. The dried product is taken out, and the water is returned to the MF treatment step. Dehydration drying process,
This is a step of dehydrating and drying the concentrated solution generated in the MF treatment step using the second dehydration drying apparatus to separate the dried product and water, and taking out the dried product and returning the water to the MF treatment step. Drying process,
It has a step of returning the permeate obtained in the RO treatment step to the wet classification step,
A method for treating and storing soil containing radioactive cesium, further comprising a step of incinerating combustibles using an incinerator while supplying concentrated water produced in the RO treatment step as cooling water. Treating soil containing radioactive cesium, soil with relatively high radioactivity concentration consisting of small-diameter particles containing radiocesium, soil with relatively low radioactivity concentration consisting of larger particle size than soil consisting of the small-diameter particles And a system for treating and storing soil containing radioactive cesium in combination with an initial separating means for separating into combustible materials and the system for treating and storing radioactive cesium according to claim 1,
A soil treatment / storage system containing radioactive cesium, wherein the initial separation means is a movable dry classification means mounted on a vehicle. A method for treating and storing soil containing radioactive cesium using the soil treating and storing system containing radioactive cesium according to claim 4,
Using the initial separation means, the soil containing radioactive cesium is treated, the soil having a relatively high radioactivity concentration composed of small-diameter particles containing radioactive cesium, and a relative particle size larger than the soil composed of the small-diameter particles A process of separating soil with low radioactive concentration and combustible materials,
Using a wet classifier, water is added to the soil consisting of small-diameter particles containing radioactive cesium and separated into a liquid containing relatively small-diameter soil and a soil hydrate containing relatively large-diameter soil. Wet classification process,
An MF treatment step in which the liquid separated in the wet classification step is treated and separated into a permeate and a concentrate using an MF device;
It has RO treatment process using RO device to process the permeate obtained in the previous process and separate it into permeate and concentrate,
Furthermore, as a process accompanying each said process,
A step of using a first dehydrating and drying apparatus to dehydrate and dry a soil hydrate containing relatively large-diameter soil separated by the wet classification step to separate the dried product into water, A first dehydration drying process in which the water is taken out and returned to the MF device;
In this step, the concentrated liquid produced in the MF treatment step is dehydrated and dried into a dried product and water using the second dehydrating and drying device. The dried product is taken out and the water is returned to the MF device. Process,
It has a step of returning the permeate obtained in the RO treatment step to the wet classification step,
Furthermore, using an incinerator, it has a step of incinerating combustibles while supplying the concentrated water generated in the RO treatment step as cooling water,
The radioactive cesium containing radioactive cesium is stored at or near the treatment site of the soil containing radioactive cesium using the initial separation means, and the ash generated in the incinerator is stored in an intermediate storage facility. Soil treatment and storage methods.

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