JP6502835B2 - Apparatus and method for treating radioactive material adsorbent - Google Patents

Description

  Embodiments of the present invention relate to an apparatus and method for treating a radioactive substance adsorbent.

  Radioactive material adsorbents are used for the separation of radioactive materials from radioactively contaminated water and the like. As a radioactive substance adsorbent, ferrocyanide is used because of high adsorption ability of radioactive substances and excellent mass productivity.

  At present, it is considered that the used radioactive material adsorbent be buried in the ground and treated. However, when ferrocyanide is buried in the ground, harmful cyanide may be generated due to contact with rain water, ground water and the like.

  As a general countermeasure against cyanide, it is known that cyanide is decomposed by oxidative decomposition, biodegradation and photolysis. However, in these methods, it is difficult to efficiently treat the spent radioactive material adsorbent.

  Therefore, a method of mixing ferrocyanide with zeolite and a method of mixing hydrotalcite are proposed as a method of treating a radioactive material adsorbent for suppressing the elution of cyanide. However, in the conventional treatment method described above, it may be difficult to efficiently treat the used radioactive material adsorbent.

JP, 2014-16311, A JP, 2015-4595, A

  The present invention has been made to solve the above-mentioned problems, and a radioactive substance adsorbent containing ferrocyanide can be treated efficiently while suppressing the elution of cyanide. An object of the present invention is to provide an apparatus and a processing method.

  One aspect of the radioactive substance adsorbent processing apparatus according to the present invention is an apparatus for processing a radioactive substance adsorbent containing ferrocyanide adsorbed with a radioactive substance, wherein the radioactive substance adsorbent dewaters the radioactive substance adsorbent. An apparatus, a dryer for drying the soil, a classifier for classifying the dried soil, a mixer for obtaining the mixture by mixing the dehydrated radioactive material adsorbent and the classified soil; And a heat treatment apparatus for heat treating the mixture.

  One embodiment of the method for treating a radioactive material adsorbent of the present invention is a method for treating a radioactive material adsorbent containing ferrocyanide adsorbed with radioactive material, which comprises the steps of dehydrating the radioactive material adsorbent, and A process of drying, a process of classifying the dried soil, a process of mixing the dehydrated radioactive material adsorbent and the classified soil to obtain a mixture, and a heat treatment of the mixture It is characterized by having.

  ADVANTAGE OF THE INVENTION According to the processing apparatus and processing method of the radioactive material adsorption agent of this invention, the radioactive material adsorption agent containing a ferrocyanide can be processed efficiently, suppressing elution of cyan | cyanogen.

It is a block diagram showing roughly an embodiment of a processing device of radioactive material adsorption agent. It is a flow figure showing the processing method of an embodiment roughly. It is a block diagram which shows roughly another embodiment of the processing apparatus of a radioactive material adsorption agent. It is a graph which shows the relationship between the particle size of the soil classified and the immobilization rate of a radioactive substance.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a processing apparatus 10 for a radioactive substance adsorbent according to an embodiment.

  The radioactive substance adsorbent processing apparatus 10 includes a radioactive substance adsorbent supply device 11 for containing the radioactive substance adsorbent 1 to be treated, and a radioactive substance adsorbent dewatering device 12 for dehydrating the radioactive substance adsorbent 1 There is. Moreover, the processing apparatus 10 of a radioactive substance adsorption agent is provided with the soil supply apparatus 13 which accommodates the soil 2, the dryer 14 which dries the soil 2, and the dry-type classification apparatus 15 which classifies the dewatered soil 2. .

  Furthermore, the radioactive substance adsorbent processing apparatus 10 mixes the classified soil 2 and the dehydrated radioactive substance adsorbent 1 to form a mixture 3 by mixing the mixture 3 and obtains a molded body. The molding apparatus 17 and the heat treatment apparatus 18 which heat-processes a molded object and produces | generates a solidified body are provided. The molding device 17 is not essential, and may be provided as needed.

  FIG. 2 is a flow chart showing a method of treating a radioactive material adsorbent according to the embodiment. In the method of treating a radioactive substance adsorbent shown in FIG. 2, a radioactive substance adsorbent dewatering step S100 for dehydrating the radioactive substance adsorbent 1, a drying step S200 for drying the soil 2, and a classification step for classifying the dried soil 2 A mixing step S400 of mixing S300, dehydrated radioactive material adsorbent 1 and classified soil 2 to obtain a mixture 3, a forming step S500 of compression molding the mixture 3, and a heat treatment of the compression molded mixture 3 Heat treatment step S600. The forming step S500 is not essential, and can be performed as needed.

The radioactive substance adsorbent 1 contains at least ferrocyanide. Examples of the ferrocyanide include Prussian blue (bitumen (ferric ferrocyanide)) represented by the following chemical formula (1).
M ^{4 +} [Fe (II) (CN) ₆ ] ^4- (1)
(Wherein, in the formula (1), M represents Fe, Co, Ni, K, Na, NH ₄ or the like).

  The radioactive substance adsorbent 1 is one on which a radioactive substance has already been adsorbed. Examples of the radioactive substance adsorbent 1 adsorbed with radioactive substances include those used for separating radioactive substances from radioactively contaminated water and the like. In the radioactive material adsorbent supply device 11, the radioactive material adsorbent 1 is usually stored in a metal container or the like while being wet with water such as contaminated water separated from the radioactive material by the radioactive material adsorbent 1, for example. .

  The radioactive substance adsorbent 1 is accommodated in the radioactive substance adsorbent supply device 11, and is supplied from the radioactive substance adsorbent supply device 11 to the radioactive substance adsorbent dewatering device 12.

  The radioactive substance adsorbent dewatering device 12 dewaters the water attached to or mixed with the radioactive substance adsorbent 1 (radioactive substance adsorbent dewatering step S100). The radioactive substance adsorbent dewatering device 12 is not particularly limited as long as it can dewater the radioactive substance adsorbent 1 to, for example, about 50% by mass or less, and a filter press or the like can be used. In addition, a device for dewatering by heating, such as a heater or a dryer, may be used.

  The water dewatered by the radioactive substance adsorbent dewatering device 12 is contaminated water containing radioactive substances. By using the radioactive substance adsorbent dehydrating apparatus 12, the polluted water can be dewatered collectively and recovered. The recovered contaminated water may be mixed with the untreated soil 2. When the soil 2 mixed with the contaminated water is treated with the radioactive substance adsorbent treatment apparatus of the present embodiment, when the soil 2 passes through the drying step S200, the radioactive substance in the contaminated water is transferred to the soil 2 and solidified It is immobilized inside. Thus, according to the radioactive substance adsorbent treatment apparatus 10 of the present embodiment, the contaminated water generated in the process of treating the radioactive substance adsorbent 1 can also be treated.

  The soil 2 is accommodated in the soil supply device 13. The soil 2 is not particularly limited, and soil generally present can be used. Examples of such soil 2 include, but are not limited to, brown lowland soil, brown forest soil, gray soil, black and white soil, and wet black and white soil, etc. in the division of the soil group.

  The soil 2 preferably contains clay. The inclusion of clay increases the immobilization rate of radioactive substances. The content ratio of clay in soil 2 is preferably 15% by mass or more. Examples of soils containing 15% by mass or more of clay include sandy clay loam, clay loam, silty clay loam, sandy clay, siliceous clay, silty clay and heavy clay soil in the soil category.

  Moreover, the soil 2 is preferably a radioactively contaminated soil on which radioactive substances have already been adsorbed. When a clean soil to which radioactive substances are not adsorbed is used as the soil 2, radioactively contaminated soil is newly generated. By using radioactively contaminated soil as the soil 2, the generation of new radioactively contaminated soil is suppressed and the increase in volume of the radioactively contaminated soil is suppressed. As radioactively contaminated soil, those to which radioactive substances adhere can be widely used. For example, as radioactively contaminated soil, soils such as houses, roads, satoyamas, sports fields, parks, etc. can be used.

  The soil 2 stored in the soil supply device 13 is supplied to the dryer 14 and dried before being classified by the dry classification device 15 (drying step S200). The temperature at the time of drying may be, for example, 60 ° C. or higher as long as the soil can be dry classified. The drying time depends on the amount of soil 2 but is about 24 hours.

  The dried soil 2 is classified by the dry classification device 15 (classification step S300). For the soil 2, for example, using a small particle having a particle diameter of about 20 μm or less increases the immobilization rate of the radioactive substance compared to using the soil 2 having a large particle diameter. On the other hand, when using the soil 2 with a small particle size, the load of classification operation becomes high. In addition, the amount of unused soil 2 increases and the amount of waste increases. Therefore, it is preferable to use the dry classification device 15 to classify soil 2 into soil 2 having a particle size of 100 μm or less and soil 2 having a particle size exceeding 100 μm, and to use soil 2 having a particle size of 100 μm or less. By using the soil 2 having a particle size of 100 μm or less, a high immobilization rate can be obtained. Here, the immobilization rate of the radioactive substance is the ratio of the radioactive substances contained in the radioactive substance adsorbent to those immobilized on the solidified body. The higher the immobilization rate of the radioactive substance, the more preferable because the radioactive substance is immobilized on the solidified body.

  The dry classification device 15 is not particularly limited, and an air separator, centrifugal separation, a sieve or the like can be used.

  The soil 2 classified with the radioactive substance adsorbent 1 dehydrated as described above is mixed by the mixing device 16 (mixing step S400). A known mixer can be used as the mixing device 16.

  The mixing ratio of the soil 2 in the mixing step S400 is preferably 40% by mass or more in order to increase the immobilization rate of the radioactive substance. On the other hand, if the mixing ratio of the soil 2 is too large, the amount of waste increases, so the content is preferably 60% by mass or less.

  In addition, in the mixing step S400, in addition to the radioactive substance adsorbent and the soil, other components can be added as necessary and within the scope not departing from the spirit of the present invention. As such a component, a component that facilitates mixing, molding, etc., a component that enhances the immobilization rate of radioactive substances, and the like can be mentioned.

  The mixture 3 obtained in the mixing device 16 is transferred to the forming device 17 and formed into a predetermined shape by a compressor or the like (forming step S500). The forming apparatus 17 has, for example, a mold including an upper mold, a lower mold, and a die, and compression molding is performed by applying pressure to the mixture 3 filled in the mold from the upper and lower direction with the upper mold and the lower mold. It consists of a machine. In addition, the shaping | molding apparatus 17 is not essential and is installed as needed. By heat treating the formed body formed by the forming device 17, the mixture 3 can be prevented from scattering in the heat treatment device 18.

When compression molding is performed in the molding apparatus 17, the pressing pressure is, for example, 300 kg / cm ² or more in terms of the immobilization rate of the radioactive substance.

In addition, when press pressure becomes high, there is a possibility that the mixture 3 may leak between the gaps of the mold, for example, between the upper die and the die or between the lower die and the die. From this mixture 3 of suppressing the leakage point of view, the press pressure is preferably 1100 kg / cm ² or less, 1000 kg / cm ² or less being more preferred.

  The formed body obtained in the forming apparatus 17 is transferred to the heat treatment apparatus 18 and subjected to heat treatment to produce a solidified body. As the heat processing apparatus 18, although an electric furnace, a kiln, a kiln, etc. are mentioned, it is not necessarily restricted to these.

  The heat treatment is preferably performed in an oxidizing atmosphere such as the atmosphere, because the ferrocyanide can be effectively decomposed. The temperature of the heat treatment is preferably 350 ° C. or more, more preferably 850 ° C. or more, and still more preferably about 1000 ° C. When the temperature of the heat treatment is 350 ° C. or more, ferrocyanide is effectively decomposed. In addition, if the temperature of the heat treatment is 850 ° C. or more, preferably 1000 ° C. or more, cesium is taken into the crystal in order to form a mineral from the clay contained in the soil 2. Thereby, since cesium can be confined more firmly in the solidified body, it is possible to extremely suppress, for example, the elution of cesium when it is immersed in water.

  The heat treatment apparatus 18 may be connected to, for example, an exhaust gas treatment apparatus for treating a gas containing toxic nitrogen oxides generated by decomposition of ferrocyanide. As the treatment method, an ammonia catalytic reduction method in which nitrogen oxide is reacted with ammonia by a catalyst to reduce it to harmless nitrogen, a noncatalytic reduction method in which nitrogen is blown into ammonia and is reduced to nitrogen without catalyst, catalytic action of activated carbon Although the activated carbon method etc. which reduce a nitrogen oxide to nitrogen according to are mentioned, it is not necessarily restricted to these.

  According to the apparatus and method for treating a radioactive substance adsorbent described above, the use of soil distributed widely and widely in the treatment of the radioactive substance adsorbent suppresses the treatment cost of the radioactive substance adsorbent. Ru. Further, since ferrocyanide is decomposed by heat treatment, elution of cyanide from the solidified body is also suppressed. In addition, since the radioactive substance released with the decomposition of ferrocyanide is adsorbed to the soil constituting the solidified body, the release of the radioactive substance to the outside is also suppressed.

  Furthermore, by collectively dewatering the water in which the radioactive material adsorbent coexists, it is possible to easily perform recovery and treatment of radioactive contaminated water generated along with the treatment of the radioactive material adsorbent. Further, by performing heat treatment while reducing the water content in the mixture of the radioactive substance adsorbent and the soil, a stable solidified body having a high immobilization rate can be produced.

  FIG. 3 is a block diagram schematically showing an apparatus 20 for treating a radioactive material adsorbent using a wet classification device in the classification step S300. In the radioactive substance adsorbent treatment apparatus 20 shown in FIG. 3, a wet classification apparatus 25 and a soil dewatering apparatus 24 are disposed in place of the dryer 14 and the dry classification apparatus 15 in the radioactive substance adsorption treatment apparatus 10. Although the present embodiment is different from the radioactive material adsorbent processing apparatus 10 in the point, the other configuration is the same as the radioactive material adsorbent processing apparatus 10. In FIG. 3, the same reference numerals are given to the configurations having the same functions as those of the processing apparatus 10 for a radioactive substance adsorbent shown in FIG.

  The radioactive substance adsorbent processing device 20 includes a radioactive substance adsorbent supply device 11 and a radioactive substance adsorbent dewatering device 12. In addition, the radioactive substance adsorbent treatment apparatus 20 includes a soil supply apparatus 13 for containing the soil 2, a wet classification apparatus 25 for wet classification of the soil 2, and a soil dewatering apparatus 24 for dewatering the classified soil 2. There is.

  Furthermore, the radioactive substance adsorbent treating apparatus 20 mixes the classified and dehydrated soil 2 with the dehydrated radioactive substance adsorbent 1 to form the mixture 3 by mixing, and the heat treatment for heat treating the mixture 3 And an apparatus 18.

  When a wet classification device is used to classify the soil 2, as shown in FIG. 3, the classification device 25 and the soil dehydrating device 24 are disposed to dewater the wet classified soil 2, and then the mixing device Supply to 16. As a result, the moisture mixed in the soil 2 can also be removed in the wet classification device 25, so the immobilization rate of the radioactive substance can be increased. In addition, the water recovered by the soil dehydrating device 24 can be used for wet classification of the untreated soil 2.

  The wet classification device 25 is not particularly limited, and a sedimentation separation device, a filtration device, or the like can be used.

  According to the apparatus and method for treating a radioactive substance adsorbent described above, the use of soil distributed widely and widely in the treatment of the radioactive substance adsorbent suppresses the treatment cost of the radioactive substance adsorbent. Ru. Further, since ferrocyanide is decomposed by heat treatment, elution of cyanide from the solidified body is also suppressed. In addition, since the radioactive substance released with the decomposition of ferrocyanide is adsorbed to the soil constituting the solidified body, the release of the radioactive substance to the outside is also suppressed.

  Furthermore, recovery and treatment of radioactive contaminated water can be easily performed by dewatering the water coexisting with the radioactive material adsorbent and collectively removing it. Further, by performing heat treatment while reducing the water content in the mixture of the radioactive substance adsorbent and the soil, a stable solidified body having a high immobilization rate can be produced.

(Example 1 to Example 4)
In Examples 1 to 4, the relationship between the particle size of the soil and the immobilization rate was examined. Examples 1 to 3 are Examples, and Example 4 is a Comparative Example.
As a radioactive substance adsorbent, ferrocyanide on which radioactive cesium was adsorbed was prepared. The ferrocyanide has a particle size in the range of 10 to 600 μm and an average particle size of 300 μm. The radioactive adsorbent was dewatered at 60 ° C. for 24 hours.

  In addition, as soils, the division in the soil group was gray lowland soil, and the division in soil type was sandy clay loam. After drying at 60 ° C., the soil was dry classified into soil having a particle size equal to or less than that of the sieve mesh and soil having a particle diameter exceeding that of the sieve mesh by a sieve having a predetermined size.

  Classification of the soil was carried out with the sieve mesh 100 μm in Example 1, 45 μm in Example 2, 20 μm in Example 3 and 300 μm in Example 4, respectively, and the soil which passed through the sieve mesh in each case was used.

The soil and the radioactive material adsorbent below the predetermined particle diameter in each of the classified examples were mixed at a mass ratio (soil: radioactive material adsorbent) of 1: 1 to obtain a mixture. The obtained mixture was compression-molded at a pressure of 900 kg / cm ² and calcined at 1000 ° C. for 1 hour for heat treatment. The immobilization rate of the obtained solidified body was calculated as follows. The amounts of radioactive cesium contained in the compact before heat treatment and in the compact after heat treatment were each measured with a germanium semiconductor detector, and calculated according to the following equation. The results are shown in the graph of FIG.

  Fixation rate of radioactive substance = (amount of radioactive cesium after heat treatment / amount of radioactive cesium before heat treatment) x 100

  It can be seen from FIG. 4 that although the immobilization rate of the radioactive substance increases as the particle size of the particles constituting the soil decreases, the immobilization rate of 100% is obtained when the particle size is 100 μm or less.

(Examples 5 to 8)
Example 1 except that the radioactive material adsorbent dewatered in the same manner as described above and soil having a particle diameter of 100 μm or less were mixed at a mass ratio (soil: radioactive material adsorbent) of 4: 6 in Example 5 and 3: 7 in Example 6. A solidified body was produced in the same manner as in. The immobilization rate was 100% in Example 5 and 93% in Example 6. Thus, it can be seen that the higher the soil mixing ratio, the higher the immobilization rate, and the immobilization rate of 100% can be obtained at 40% or more of the total amount of the mixture.

The radioactive material adsorbent dewatered in the same manner as described above and the soil having a particle diameter of 100 μm or less were mixed at a mass ratio (soil: radioactive material adsorbent) of 1: 1, and compression molded at 900 kg / cm ² . Then, in Example 7, it baked at 500 degreeC for 3 hours, and in Example 8 1 hour at 1000 degreeC, and obtained the solidified body. The immobilization rate was 100% in all cases, and the elution cyanide concentration was below the lower limit of detection (0.05 ppm).

  The dissolution test of cesium was conducted on the solidified products obtained in Examples 7 and 8 as follows. The solidified body was immersed in water for 6 hours, the amount of radioactive cesium in the water after immersion was measured in the same manner as described above, and the dissolution rate of cesium was calculated by the following equation.

  Dissolution rate = (amount of radioactive cesium in water after immersion / amount of radioactive cesium in solidified body before immersion) x 100

  The dissolution rate was 0.3% in Example 7 and 0.06% in Example 8. Thus, it can be seen that the higher the temperature of the heat treatment, the lower the dissolution rate, and the radioactive cesium is strongly confined in the solidified body.

  While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and the gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

  DESCRIPTION OF SYMBOLS 1 ... radioactive substance adsorption agent, 2 ... soil, 3 ... mixture, 10, 20 ... radioactive substance adsorption agent processing apparatus, 11 ... radioactive substance adsorption agent supply apparatus, 12 ... radioactive substance adsorption dewatering apparatus, 13 ... soil supply apparatus , 14: dryer, 15: dry classification device, 16: mixing device, 17: forming device, 18: heat treatment device, 24: soil dewatering device, 25: wet classification device, S100: radioactive substance adsorbent dewatering step, S200 ... Drying step, S300 ... classification step, S400 ... mixing step, S500 ... molding step, S600 ... heat treatment step.

Claims (8)

An apparatus for treating a radioactive substance adsorbent comprising ferrocyanide adsorbed with radioactive substance, comprising
A radioactive substance adsorbent dewatering device for dehydrating the radioactive substance adsorbent;
With a dryer that dries the soil,
A classifier for classifying the dried soil;
A mixing device for mixing the dehydrated radioactive adsorbent and the classified soil to obtain a mixture;
And a heat treatment apparatus for heat treating the mixture. An apparatus for treating a radioactive substance adsorbent comprising ferrocyanide adsorbed with radioactive substance, comprising
A radioactive substance adsorbent dewatering device for dehydrating the radioactive substance adsorbent;
A classifier for classifying soil,
A dewatering device for dewatering the classified soil;
A mixing device for mixing the dehydrated radioactive adsorbent and the dehydrated soil to obtain a mixture;
And a heat treatment apparatus for heat treating the mixture.   The processing apparatus of the radioactive material adsorbent according to claim 1 or 2, further comprising a compression molding device for compression molding the mixture to obtain a molded body, and the heat treatment device heats the molded body.   The said classification apparatus classifies the said soil with a particle size of 100 micrometers or less, The processing apparatus of the radioactive material adsorption agent of any one of the Claims 1 thru | or 3 characterized by the above-mentioned. What is claimed is: 1. A method of treating a radioactive material adsorbent comprising ferrocyanide adsorbed with radioactive material, comprising:
Dehydrating the radioactive material adsorbent;
Drying the soil,
Classifying the dried soil;
Mixing the dehydrated radioactive adsorbent and the classified soil to obtain a mixture;
Heat treating the mixture, and a method of treating a radioactive material adsorbent. What is claimed is: 1. A method of treating a radioactive material adsorbent comprising ferrocyanide adsorbed with radioactive material, comprising:
A step of classifying the soil,
Dewatering the classified soil;
Dehydrating the radioactive material adsorbent;
Mixing the dehydrated radioactive adsorbent and the classified soil to obtain a mixture;
Heat treating the mixture, and a method of treating a radioactive material adsorbent.   The method of treating a radioactive material adsorbent according to claim 5 or 6, wherein the proportion of the soil to the total amount of the mixture is 40% by mass or more.   The temperature of the said heat processing is 1000 degreeC or more, The processing method of the radioactive material adsorption agent of any one of the Claims 5 thru | or 7 characterized by the above-mentioned.

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