JP2013231678A - Method for decontaminating soil and incineration ash by ionization of radioactive cesium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method which enables isolation of radioactive cesium adsorbing to fine clayey particles contaminated with radioactive cesium, and return of the decontaminated fine clayey particles to actual places and reuse thereof as agricultural soil in decontamination of radioactive cesium-contaminated soil.SOLUTION: Radioactive cesium-contaminated soil is added to water and left to stand. Salt is added to a contaminated fine floating particle fraction separated from a coarse particle fraction and thereafter, the following is performed under atmospheric or reduced pressure: exclusively either heating of high-frequency dielectric heating and electromagnetic induction heating; a combination of either heating thereof with ultrasonic irradiation; or exclusively ultrasonic irradiation. Thereby, radioactive cesium adsorbing to fine clayey particles is exchanged for cations of salt and ionized so that the fine clayey particles, from which the radioactive cesium is desorbed, can be returned to soil at actual places and reused as agricultural soil. Radioactive cesium-contaminated incineration ash is decontaminated by similar treatment. Radioactive cesium adsorbing to incineration ash is exchanged for cations of salt, ionized and separated into a decontaminated incineration ash fraction and a radioactive cesium-containing supernatant fraction.

Description

  The present invention relates to a technique for ionizing and decontaminating radioactive cesium from soil or incinerated ash adsorbed with radioactive cesium.

  In soil contaminated by the fall of nuclear material scattered by nuclear tests or nuclear power plant accidents, cesium 137 with a half-life of about 30 years is considered to be the main radioactive element affecting the human body over a long period of time (non-patented) Reference 1), the development of effective technology for the treatment of soil and incinerated ash contaminated with radioactive cesium scattered in the accident at the TEPCO Fukushima Daiichi Nuclear Power Station is currently a major issue.

Regarding soil decontamination, a government-sponsored demonstration test project is underway, and various technologies have been verified (Non-Patent Document 2).
They can be broadly divided into dry technology and wet technology. As a dry technique, a demonstration test of a cesium sublimation technique by rotary heating was performed, and cesium volatilized by heating at 800 ° C. was 10% or less. The boiling point of cesium is 641 ° C., and this temperature exceeds it, indicating that the soil is strongly bound to radioactive cesium.
In this test, when a special chemical was added and heated at a high temperature of 1300 ° C., a volatilization rate of 99.9% was gradually obtained. However, such high heat treatment causes irreversible denaturation in the soil, so that the treated soil cannot be reused for agricultural land.

As a wet technique, a demonstration test of a cesium release technique that dissolves soil using an organic acid was conducted. In this test, a decontamination rate of up to 93% was obtained by destroying the microstructure of the soil with oxalic acid and releasing the adsorbed radioactive cesium.
Since this treatment also destroys the fine structure of the soil, the treated soil cannot be reused for agricultural land.

  In addition, because most of the radioactive cesium is adsorbed by the clay fraction of the soil, a demonstration test of technology to remove contaminated soil fines has also been performed. This method has the problem of losing all the clay that has a large role as cultivated soil, because it removes all the fine grains less than approximately 75 microns in diameter.

  The government manager of this project summarized the above results and concluded that all the technologies tested in this project remove soil fines and are all difficult to apply to farmland.

  As a technique for removing nuclear waste from contaminated soil, for example, Patent Document 1 discloses a technique for separating a mixed liquid obtained by mixing contaminated soil with an ammoniacal liquid by fractionation. According to this technology, not only various radioactive elements but also mercury and PCB in soil can be separated and removed. However, in this technique, since the soil is irreversibly denatured by the ammoniacal liquid, the treated soil cannot be reused for farmland as in the wet treatment technique.

On the other hand, a major problem has emerged regarding the contamination of municipal waste incineration ash.
According to the Ministry of the Environment, the radioactive cesium concentration of incinerated ash was measured at 469 facilities in 16 prefectures. The number of facilities whose radioactive cesium concentration exceeded the standard value (8000 Bq / kg) was 7 in the main ash, fly ash It was 42 (nonpatent literature 3).
In addition, according to estimates by the Ministry of the Environment, there are about 50,000 tons of incinerated ash stored in 13 prefectures exceeding the standard value (Non-Patent Document 4), and a final disposal method similar to that for soil exceeding the standard value is necessary. Yes. However, incineration ash decontamination technology has not been developed yet.

The data of Non-Patent Document 3 shows that as a general trend of radioactive cesium concentration of waste incineration ash, the concentration of fly ash is several times that of main ash, and the concentration of molten slag is about several tenths of fly ash. It shows that it is decreasing.
The decontamination technology for radioactive cesium-contaminated incineration ash, especially the high-dose fly ash decontamination technology, is now a major issue.

The form of cesium deposition on incinerated ash has not been elucidated like soil. Furthermore, the components of the incineration ash are not uniform because the waste is a composite material made of various materials, and also varies depending on the heating method and the fly ash treatment process. Therefore, the technique of removing radioactive cesium must be based on the premise that the forms of cesium adhesion to incineration ash are diverse.
In other words, as in the case of soil, radioactive cesium in contaminated incineration ash cannot be denied that it may be strongly adsorbed by fine incineration ash particles, and fine particles that pass through a bag filter that removes dust from the exhaust. Measures based on the premise of capturing are necessary.

Japanese National Patent Publication No. 10-505903

“About the creation of a radiation distribution map (soil map of radioactive cesium) by the Ministry of Education, Culture, Sports, Science and Technology”, Ministry of Education, Culture, Sports, Science and Technology, August 30, 2011 Yoshitake Shiratori and Akihiro Tagawa “(3) Report on the results of the decontamination technology verification test project”, Cabinet Office Nuclear Disaster Life Support Team, Ministry of the Environment, Japan Atomic Energy Agency Report Meeting ”, March 26, 2012, Fukushima City (3) Ministry of the Environment, “List of Radiocesium Concentration Measurement Results for Incineration Ash at 16 Waste Disposals in 16 Prefectures”, August 29, 2011 Asahi Shimbun, March 31, 2012 article Satoshi Matsumoto "Short comment on decontamination of forest and field soil, application of construction civil engineering technology", soil science of radioactive decontamination-from forest, field and field to home garden-, Science Council of Japan, Agricultural Academy of Agriculture, Heisei March 14, 2012, Fukushima Keizo Ishii “Decontamination of radioactive cesium-contaminated soil by water washing”, 34th Atomic Energy Commission Document No. 1, September 6, 2011 Masaru Shiozawa, “New knowledge of soil contamination”, Soil science of radioactive decontamination-From forests / fields / fields to home gardens-, Japan Academy of Soil Science Subcommittee, Japanese Academy of Agricultural Sciences, March 14, 2012, Fukushima

The main issues required for decontamination technology are as follows.
(1) In order to reuse soil after decontamination as agricultural soil, it is necessary to be able to remove radioactive cesium without loss of fine grains or destruction of fine structure.
(2) In order to decontaminate the contaminated incineration ash, it is necessary to remove radioactive cesium that may have adsorbed to the ash and to decontaminate the fine contaminated fly ash that passes through the bag filter of the exhaust without missing it. Don't be.

In order to solve the above-mentioned problem (1), the present invention releases radioactive cesium firmly adsorbed on fine particles (clay) of contaminated soil by substituting with a salt cation. Reusable to agricultural land.
In order to solve the problem (2), the present invention removes radioactive cesium that may have been adsorbed on the contaminated incineration ash by substituting it with a salt cation, and removes very fine contaminated fly ash. We realized dyeing.

In the decontamination technology of radioactive cesium-contaminated soil, the present invention is to put radioactive cesium-contaminated soil into water and leave it to stand, separate the coarse fraction and fine-floating fraction, and add salt ( After loading, the physical action is applied to ionize the radioactive cesium adsorbed on the fine particles, and the fine particle fraction from which the radioactive cesium is released and the radioactive cesium-containing supernatant fraction are separated, and the radioactive cesium-containing supernatant is separated. The main feature is that the radioactive cesium in the fraction is slightly soluble, aggregated and collected, and the decontaminated coarse and fine fractions are restored to the local site.
In the decontamination technology for radioactive cesium-contaminated incineration ash, the present invention adds the incineration ash to water, adds salt, and loads the physical action to ionize and remove the radioactive cesium adsorbed on the incineration ash. By separating the incinerated ash fraction after dyeing and the liquid fraction containing radioactive cesium, insolubilizing the radioactive cesium in the liquid fraction containing radioactive cesium and aggregating and collecting it, incineration without loss of extremely small size incinerated ash The main feature is the decontamination of ash.

  The decontamination method by ionization of radioactive cesium according to claim 1 according to the present invention is a method of ionizing and decontaminating radioactive cesium in soil contaminated with radioactive cesium, wherein the soil contaminated with radioactive cesium is poured into water and allowed to stand. After separating the coarse fraction formed by the precipitation of coarse particles and the upper contaminated fine particle floating fraction, adding salt to the contaminated fine particle floating fraction, Either high-frequency dielectric heating or electromagnetic induction heating alone or in combination with ultrasonic irradiation, or only ultrasonic irradiation is performed to ionize radioactive cesium adsorbed on fine particles, and then the fine particle floating fraction after treatment After decontamination, it is separated into a fine-grained fraction and a radioactive cesium-containing supernatant fraction, and the radioactive cesium-containing supernatant fraction is slightly solubilized, aggregated and recovered, and the radioactive cesium-containing supernatant fraction By the elevation of cesium aggregate and recovered by insolubilization, characterized in that to enable agricultural soil reuse of clay fines and decontaminated.

  The decontamination method by ionization of radioactive cesium according to claim 2 according to the present invention is a method of ionizing and decontaminating radioactive cesium contaminated incineration ash by adding radioactive cesium contaminated incineration ash to water and salting (En), and in a normal pressure or reduced pressure environment, either high frequency dielectric heating or electromagnetic induction heating alone or in combination with ultrasonic irradiation, or only ultrasonic irradiation, and radioactive cesium adsorbed on the incineration ash After ionization, after decontamination, it is separated into an incinerated ash fraction and a radioactive cesium-containing liquid fraction, and the radioactive cesium in the radioactive cesium-containing liquid fraction is slightly solubilized and aggregated and collected.

  The decontamination method by ionization of radioactive cesium according to claim 3 according to the present invention is the decontamination method by ionization of radioactive cesium according to claim 1 or 2, wherein the salt is a potassium salt compound for fertilizer. It is characterized by that.

  The decontamination method by ionization of radioactive cesium according to claim 4 according to the present invention is the decontamination method by ionization of radioactive cesium according to claim 1 or 2, wherein the frequency range of the high frequency dielectric heating is 1 MHz to 5 GHz. The frequency range of high frequency induction heating in the electromagnetic induction heating is 3 kHz to 10 MHz, the frequency range of low frequency induction heating in the electromagnetic induction heating is 50 Hz to 1 kHz, and the ultrasonic wave The frequency range is 20 kHz to 1 GHz.

  The decontamination method by ionization of radioactive cesium according to the present invention is a technique for decontaminating soil contaminated with radioactive cesium, and injecting the contaminated soil into water to separate it into a contaminated fine particle floating fraction and a coarse particle fraction. Salt is added to the fine-grained floating fraction, and physical undulation is applied to ionize the radioactive cesium adsorbed on the fine-grain by substituting the salt cation. The supernatant fraction and fine-grained fraction containing radioactive cesium Since the radioactive cesium in the supernatant fraction containing radioactive cesium is slightly soluble and agglomerated and collected, the decontamination that can reuse the coarse fraction and the decontaminated fine fraction as agricultural soil is actually There is an advantage that it can be performed at a reasonable processing speed and cost.

  In addition, in the technology for decontamination of incinerated ash contaminated with radioactive cesium, the contaminated incinerated ash is added to water, salt is added, and physical waves are applied to the radioactive cesium adsorbed on the fine particles. It is ionized by substituting ions, separated into a radioactive cesium-containing supernatant fraction and an incinerated ash fraction after decontamination, and radioactive cesium in the radioactive cesium-containing supernatant fraction is slightly solubilized and aggregated and recovered, so that very fine radioactive flying There is an advantage that decontamination without ash loss can be performed.

It is explanatory drawing which shows the contaminated soil decontamination step of 1st Embodiment. It is explanatory drawing which shows the contaminated soil decontamination step of 2nd Embodiment. It is explanatory drawing which shows the pollution incineration ash decontamination step of 3rd Embodiment. It is explanatory drawing which shows the pollution incineration ash decontamination step of 4th Embodiment.

In the first embodiment of the present invention, as shown in FIG. 1, first, radioactive cesium-contaminated soil 1 is accommodated in a container (not shown), water 2 is injected, and after stirring, allowed to stand for a certain period of time. Then, the coarse particles are precipitated, and separated into the coarse precipitate fraction 4 accumulated at the lower part of the container and the contaminated fine particle floating fraction 3 at the upper part.
The coarse precipitate fraction 4 thus separated is mainly composed of gravel and sand having a particle diameter of 2 mm or more, and hardly adsorbs radioactive cesium, and can be reused as it is as agricultural land (Non-patent Document 5).

Next, the contaminated fine particle floating fraction 3 and the coarse particle precipitate fraction 4 are accommodated in respective dedicated containers (not shown), and the potassium salt 5 is added to the contaminated fine particle floating fraction 3.
The potassium salt to be added is preferably a common salt compound for fertilizer because it is convenient for recycling the fine floating fraction to agricultural soil after the treatment. More preferable compounds are potassium silicate or potassium chloride. Can be used.

  In the radioactive cesium-contaminated soil, about 70% of cesium 137 forms a strong bond with the clay fraction (Non-patent Document 6). According to a recent announcement, 16,530 Bq / kg of radioactive cesium-contaminated soil In the soil, most of the radioactive cesium is present in the clay fraction having a particle size of 2 microns or less and the silt fraction having a particle size of 2 to 20 microns (Non-Patent Document 5).

  The first embodiment of the present invention includes a high-frequency dielectric heating device 7 and an ultrasonic generator 8, and is heated by high-frequency dielectric and / or ultrasonic waves in a normal pressure environment or an environment decompressed by the decompression device 6. Irradiation is performed to promote the replacement of cesium ions and cations in the aqueous salt solution, that is, potassium ions, by heating and / or shaking action, thereby releasing radioactive cesium ions into the aqueous solution.

The high-frequency dielectric heating of the first embodiment is not only the generation of frictional heat caused by the molecular motion of polarizable molecules, mainly water molecules, but also the molecular motion itself, particularly in the case of microwave dielectric heating. This promotes the replacement of the radioactive cesium salt adsorbed on the fine particles with cations.
A preferable frequency range of the high frequency dielectric heating in the first embodiment is 1 MHz to 5 GHz.

In the ultrasonic irradiation of the first embodiment, the fine-grain floating fraction 3 charged with salt is shaken to cause cavitation, and the substitution of the radioactive cesium salt adsorbed on the fine grains with the cation is promoted.
A preferable ultrasonic frequency range in the first embodiment is 20 kHz to 1 GHz.

  In the first embodiment, the physical action to be given according to the components and properties of the soil to be decontaminated is controlled only by high-frequency dielectric heating, only by ultrasonic irradiation, or by high-frequency dielectric heating and ultrasonic. It can be switched to combined use of irradiation.

  In the first embodiment, the above-described high-frequency dielectric heating and / or ultrasonic irradiation can be performed under normal pressure or reduced pressure, depending on the components and properties of the soil to be decontaminated. When the salt aqueous solution into which contaminated soil is introduced under reduced pressure is heated, the boiling point drops, so that the substitution of adsorbed radioactive cesium and cations can be promoted without destroying the soil microstructure.

  In FIG. 1, a potassium salt is illustrated as being used. However, in the first embodiment, any salt in which an alkali metal is combined with an anion as a cation can be applied. Preferably, it is a fertilizer compound that has been conventionally used and whose action has been clarified, and more preferred is potassium silicate or potassium chloride that has been proven in actual contaminated farmland. Depending on the nature of the soil to be treated, ammonium salts such as ammonium sulfate or ammonium nitrate are also applicable.

  In this way, when radioactive cesium adsorbed on the fine particles by high frequency dielectric heating and / or ultrasonic irradiation is replaced with potassium ions and released, the radioactive cesium is ionized and eluted in the aqueous solution. The fine particle suspension after decontamination and treatment is allowed to stand for a certain period of time to precipitate decontaminated fine particles.

Fine grain precipitation takes a longer time than the coarse grain precipitation described above, but in order to recover to the farmland, it is important to leave it until all the submicron sized fine grains settle.
Of course, separation means such as a hydrocyclone can be applied to accelerate the separation.

It takes 2-3 months or several months or more for the radioactive cesium ions dissolved in water to be adsorbed on the soil clay (Non-patent Document 7).
Therefore, the contaminated soil can be immersed in water and allowed to stand for several days to separate the precipitated decontaminated fine particle fraction 10 and the radioactive cesium-containing supernatant fraction 9.
In the first embodiment, although it varies greatly depending on the components or properties of the target soil, the standard time required for sedimentation of fine particles is set to be within a few days.

The fine-grained fraction 10 that has been decontaminated can be returned to the collection site together with the coarse-grained sediment fraction 4 separated in the previous step, and can be restored.
As a result, the fine clay particles return to the original soil and can be reused as agricultural soil.
Moreover, since the salt applied for the substitution and release of radioactive cesium ions is a potash fertilizer commonly used for agriculture, it does not cause irreversible denaturation in the agricultural soil.

  The high-concentration radioactive cesium ions present in the contaminated supernatant fraction 9 separated by standing within a few days are double-chlorinated and hardly soluble, and are aggregated and recovered by a known means such as the addition of theolite.

  In the first embodiment, radioactive cesium-contaminated soil is poured into water, stirred, and left to stand to precipitate coarse particles, which are separated into a coarse-grained precipitate fraction and a contaminated fine-particle floating fraction. Salt is added to the floating particle fraction, and radioactive cesium adsorbed on the floating contaminated fine particles is replaced by cations in the salt solution and released by dielectric heating and / or ultrasonic irradiation to decontaminate the clay fine particles. Therefore, decontaminated clay can be restored to the local area and reused as farmland.

In the second embodiment of the present invention, as shown in FIG. 2, first, radioactive cesium-contaminated soil 11 is accommodated in a container (not shown), water 12 is injected, and after stirring, allowed to stand for a certain period of time. Then, the coarse particles are precipitated and separated into a coarse-grained precipitate fraction 14 and an upper fine-grained floating fraction 13 accumulated in the lower part of the container.
The coarse precipitate fraction 14 thus separated is mainly composed of gravel and sand having a particle diameter of 2 millimeters or more, and hardly adsorbs radioactive cesium, so that it can be reused as agricultural soil (Non-patent Document 5).

Next, the fine-grained floating fraction 13 and the coarse-grained precipitated fraction 14 are accommodated in their respective dedicated containers (not shown), and potassium salt 15 is added to the fine-grained floating fraction 13.
The salt to be added is preferably a commonly used salt compound for fertilizer because it is convenient for recycling the fine-grained floating fraction to agricultural soil after the treatment. More preferable compounds include potassium silicate or potassium chloride. Can be used.

  In the radioactive cesium-contaminated soil, about 70% of cesium 137 forms a strong bond with the clay fraction (Non-patent Document 6). According to a recent announcement, 16,530 Bq / kg of radioactive cesium-contaminated soil In the soil, most of the radioactive cesium is present in the clay fraction having a particle size of 2 microns or less and the silt fraction having a particle size of 2 to 20 microns (Non-Patent Document 5).

  The second embodiment of the present invention includes either a high-frequency induction heating device or a low-frequency induction heating device as an electromagnetic induction device 17 and an ultrasonic generator 18, and is an environment in which the pressure is reduced by a normal pressure environment or a pressure reduction device 16. Below, heating by high-frequency induction or low-frequency induction and / or ultrasonic irradiation is performed, and substitution of cesium ions and cations (potassium ions) in salt aqueous solution is promoted by a temperature rising action and / or shaking action, and radioactive Releases cesium ions into aqueous solution.

In the second embodiment, in the case of high-frequency induction heating, the fine particle floating fraction 13 charged with salt is heated to promote the substitution of radioactive cesium adsorbed on the fine particles with the cation of the salt.
A preferable frequency range of the high frequency induction heating in the second embodiment is 3 kHz to 10 MHz.

In the second embodiment, in the case of low-frequency induction heating, the fine floating fraction 13 into which salt is added is heated to promote the substitution of the radioactive cesium salt adsorbed by the fine particles with cations. .
A preferable frequency range of the low frequency induction heating in the second embodiment is 50 Hz to 1 kHz.

The ultrasonic load according to the second embodiment causes the cavitation to occur by shaking the fine-grained floating fraction 13 into which the salt has been added, and promotes the replacement of the radioactive cesium salt adsorbed by the fine-grain with a cation.
A preferable ultrasonic frequency range in the second embodiment is 20 kHz to 1 GHz.

  In the second embodiment, the physical action given according to the components and properties of the soil to be decontaminated is controlled only by high frequency induction heating, only ultrasonic waves, or a combination of high frequency induction heating and ultrasonic waves by a control device (not shown). You can switch to Moreover, it is possible to switch to only low frequency induction heating, only ultrasonic waves, or a combination of low frequency induction heating and ultrasonic waves.

  In the second embodiment, the combined load of the above-described physical actions can be performed under normal pressure or reduced pressure, depending on the components and properties of the soil to be decontaminated. When the salt aqueous solution into which contaminated soil is introduced under reduced pressure is heated, the boiling point drops, so that the substitution of adsorbed radioactive cesium and cations can be promoted without destroying the soil microstructure.

  In FIG. 2, the potassium salt is illustrated as being used, but in the second embodiment, any salt in which an alkali metal is used as a cation and an anion is combined can be applied. Preferably, it is a fertilizer compound that has been conventionally used and whose action has been clarified, and more preferred is potassium silicate or potassium chloride that has been proven in actual contaminated farmland. Depending on the nature of the soil to be treated, ammonium salts such as ammonium sulfate or ammonium nitrate are also applicable.

  In this way, when radioactive cesium adsorbed on the fine particles by heating by electromagnetic induction and / or ultrasonic irradiation is replaced with potassium ions and released, the radioactive cesium is ionized and eluted in the aqueous solution. Is decontaminated, and the fine particle suspension after treatment is allowed to stand for a certain period of time to precipitate the decontaminated fine particles.

Fine-grained sedimentation requires a longer time than the coarse-grained sedimentation described above, but in order to recover to farmland, it is important to leave it until all the submicron-sized fine granules settle. .
Of course, separation means such as a hydrocyclone can be applied to accelerate the separation.

It takes 2-3 months or several months or more for the radioactive cesium ions dissolved in water to be adsorbed on the soil clay (Non-patent Document 7).
Therefore, the contaminated soil can be immersed in water and allowed to stand for several days to separate the precipitated decontaminated fine-grain fraction 20 and the radioactive cesium-containing supernatant fraction 19.
In the second embodiment, although it varies greatly depending on the components or properties of the target soil, the standard time required for sedimentation of fine particles is set to be within several days.

The fine-grained fraction 20 that has been decontaminated can be returned to the collection site together with the coarse-grained sediment fraction 14 separated in the previous step, and can be restored.
As a result, fine clay particles are restored to the original soil, and can be reused as agricultural soil.
Moreover, since the salt applied for the substitution and release of radioactive cesium ions is a potash fertilizer commonly used for agriculture, it does not cause irreversible denaturation in the agricultural soil.

  High-concentration radioactive cesium ions present in the supernatant fraction 19 separated by standing for several days or less are double-chlorinated and hardly soluble, and are aggregated and collected by a known means such as the addition of theolite.

  In the second embodiment, radioactive cesium-contaminated soil is poured into water, stirred, and left to settle coarse particles, separating the coarse-grained sediment fraction and the contaminated fine-particle floating fraction, Salt is added to the granule fraction, and radioactive cesium adsorbed on the contaminated fine particles is released by substitution with cations in the aqueous salt solution by induction heating and / or ultrasonic irradiation to decontaminate the clay fine particles. Therefore, decontaminated clay can be restored to the local area and reused as agricultural soil.

  Next, in the third embodiment of the present invention, as shown in FIG. 3, first, radioactive cesium-contaminated incineration 21 is accommodated in a container (not shown), water 22 is injected, and potassium salt 23 is added. Add.

  The third embodiment of the present invention includes a high-frequency dielectric heating device 25 and an ultrasonic generator 26, and is heated and / or ultrasonically generated by high-frequency dielectric under an atmospheric pressure environment or an environment decompressed by the decompression device 24. Irradiation is performed to promote the replacement of cesium ions and cations in the aqueous salt solution, that is, potassium ions, by heating and / or shaking action, thereby releasing radioactive cesium ions into the aqueous solution.

The high-frequency dielectric heating of the third embodiment is not only the generation of frictional heat caused by the molecular motion of polarizable molecules, mainly water molecules, but also the molecular motion itself, particularly in the case of microwave dielectric heating. This promotes the replacement of radioactive cesium salts adsorbed on contaminated incineration ash with cations.
A preferable frequency range of the high frequency dielectric heating in the third embodiment is 1 MHz to 5 GHz.

The ultrasonic load according to the third embodiment causes cavitation by shaking the contaminated incineration ash liquid charged with salt, and promotes the replacement of the radioactive cesium salt adsorbed on the contaminated incineration ash with cations.
A preferable frequency range of the ultrasonic load in the third embodiment is 20 kHz to 1 GHz.

  In the third embodiment, the physical action given according to the components and properties of the contaminated incineration ash is controlled by a high-frequency dielectric heating only, ultrasonic irradiation only, or high-frequency dielectric heating and ultrasonic irradiation. Can be switched to combined use.

  In the third embodiment, the above-described high-frequency dielectric heating and / or ultrasonic irradiation can be performed under normal pressure or reduced pressure according to the components and properties of the contaminated incineration ash. When the salt aqueous solution charged with contaminated incineration ash is heated under reduced pressure, the boiling point drops, so that the substitution of adsorbed radioactive cesium and cations can be accelerated.

  In this way, when radioactive cesium adsorbed on contaminated incineration ash by high-frequency dielectric heating and / or ultrasonic irradiation is replaced with potassium ions and liberated, radioactive cesium is ionized and eluted into the aqueous solution. Is decontaminated, and the incinerated ash suspension after treatment is allowed to stand for a certain period of time to precipitate.

  Of course, separation means such as a hydrocyclone can be applied to accelerate the sedimentation of the incineration ash.

  The decontaminated incineration ash (solid fraction 28) melts and can be used for cement aggregate and the like.

  Since high concentration of radioactive cesium ions is present in the liquid fraction 27, this is double-chlorinated to make it hardly soluble, and is aggregated and recovered by a known means such as theorite.

  In the third embodiment, water and salt are added to radioactive cesium-contaminated incineration ash, and the radioactive cesium adhering to the incineration ash by dielectric heating and / or ultrasonic irradiation is replaced with a cation of the salt to release the incineration ash. Therefore, it is possible to decontaminate any fine contaminated fly ash.

  In the fourth embodiment of the present invention, as shown in FIG. 4, first, radioactive cesium-contaminated incineration ash is placed in a container, water 33 is injected, and potassium salt 34 is added.

  The fourth embodiment of the present invention includes either a high-frequency induction heating device or a low-frequency induction heating device as an electromagnetic induction device 35 and an ultrasonic generator 36, and the pressure is reduced in a normal pressure environment or a decompression device 34. In the environment, high-frequency induction or low-frequency induction heating and / or ultrasonic irradiation is performed, and by the temperature raising action and / or shaking action, the replacement of cesium ions and cations in the salt solution, that is, potassium ions is promoted. Releases radioactive cesium ions into aqueous solution.

In the fourth embodiment, in the case of high frequency induction heating, the temperature of the contaminated incineration ash aqueous solution charged with salt is raised to promote the substitution of the radioactive cesium salt adsorbed on the contaminated incineration ash with cations.
A preferable frequency range of the high frequency induction heating in the fourth embodiment is 3 kHz to 10 MHz.

In the fourth embodiment, in the case of low-frequency induction heating, the temperature of the contaminated incinerated ash aqueous solution charged with salt is increased to promote the replacement of the radioactive cesium salt adsorbed on the contaminated incinerated ash with cations.
A preferable frequency range of the low frequency induction heating in the fourth embodiment is 50 Hz to 1 kHz.

The ultrasonic load of the fourth embodiment shakes the contaminated incineration ash aqueous solution into which salt is added to cause cavitation, and promotes substitution of the radioactive cesium salt adsorbed on the fine particles with a cation.
A preferable frequency range of the ultrasonic load in the fourth embodiment is 20 kHz to 1 GHz.

  In the fourth embodiment, the physical action to be given according to the components and properties of the contaminated incineration ash is applied only to high-frequency induction heating, only ultrasonic waves, or a combination of high-frequency induction heating and ultrasonic waves by a control device (not shown). Can be switched. Moreover, it is possible to switch to only low frequency induction heating, only ultrasonic waves, or a combination of low frequency induction heating and ultrasonic waves.

  Further, in the fourth embodiment, the combined load of the above-described physical actions can be performed under normal pressure or reduced pressure, depending on the components and properties of the contaminated incineration ash. When the salt aqueous solution charged with contaminated incineration ash is heated under reduced pressure, the boiling point drops, so that the substitution of adsorbed radioactive cesium and cations can be accelerated.

  In this way, when radioactive cesium adsorbed on contaminated incineration ash is replaced by potassium ions and released by heating by electromagnetic induction and / or ultrasonic irradiation, the radioactive cesium ionizes and elutes into the aqueous solution. Incinerated ash is decontaminated, and the incinerated ash suspension after treatment is allowed to stand for a certain period of time, decontaminated and incinerated ash is precipitated.

  Of course, separation means such as a hydrocyclone can be applied to accelerate the sedimentation of the incineration ash.

  The decontaminated incineration ash (solid fraction 38) melts and can be used for cement aggregate and the like.

  The liquid fraction 37 contains a high concentration of radioactive cesium ions, which are double-chlorinated to be hardly soluble, and are aggregated and collected by a known means such as seolite.

  In the fourth embodiment, water and salt are added to radioactive cesium-contaminated incineration ash, and the radioactive cesium adhering to the incineration ash by induction heating and / or ultrasonic irradiation is replaced with a cation of the salt to release the incineration ash. Therefore, it is possible to decontaminate any fine contaminated fly ash.

By decontaminating radioactive cesium-contaminated soil without losing, destroying, or denaturing clay granules, it can be applied to the use of decontamination soil on site.
Moreover, it can apply to the use which decontaminates radioactive cesium contamination incineration ash, without leaking the radioactive cesium adhering to any minute fly ash.

DESCRIPTION OF SYMBOLS 1 Radiocesium contaminated soil 2 Water 3 Contaminated fine particle floating fraction 4 Coarse-grained sediment fraction 5 Potassium salt 6 Decompression device 7 High frequency dielectric device 8 Ultrasonic generator 9 Contaminated supernatant fraction 10 Fine particle fraction

Claims (4)

A method for ionizing and decontaminating radioactive cesium in soil contaminated with radioactive cesium,
Put radioactive cesium-contaminated soil into water and let it stand,
Separating the coarse fraction formed by coarse sedimentation and the contaminated fine suspended fraction at the top,
After adding salt to the contaminated fine floating fraction,
After ionizing radioactive cesium adsorbed on contaminated fine particles by performing either high frequency dielectric heating or electromagnetic induction heating alone or in combination with ultrasonic irradiation or only ultrasonic irradiation in an atmospheric pressure environment or a reduced pressure environment,
The fine floating fraction after treatment is separated into a fine-grained fraction after decontamination and a supernatant fraction containing radioactive cesium,
By making the radioactive cesium in the supernatant fraction containing radioactive cesium insoluble and aggregating and collecting it,
A decontamination method by ionization of radioactive cesium, which makes it possible to reuse agricultural soil of decontaminated clay-like fine grains. A method of ionizing and decontaminating radioactive cesium from radioactive cesium-contaminated incineration ash,
Add radioactive cesium-contaminated incineration ash to water, add salt,
After ionizing radioactive cesium adsorbed on the incineration ash by performing either high frequency dielectric heating or electromagnetic induction heating alone or in combination with ultrasonic irradiation or only ultrasonic irradiation in an atmospheric pressure environment or a reduced pressure environment,
Separated into incinerated ash fraction and radioactive cesium-containing liquid fraction after decontamination
A decontamination method by ionization of radioactive cesium, wherein the radioactive cesium in the liquid fraction containing radioactive cesium is slightly soluble, aggregated and collected.   3. The decontamination method by ionization of radioactive cesium according to claim 1 or 2, wherein the salt is a potassium salt compound for fertilizer.   The frequency range of the high frequency dielectric heating is 1 MHz to 5 GHz, the frequency range of the high frequency induction heating of the electromagnetic induction heating is 3 kHz to 10 MHz, and the frequency of the low frequency induction heating of the electromagnetic induction heating. 3. The decontamination method by ionization of radioactive cesium according to claim 1, wherein the range is 50 Hz to 1 kHz, and the frequency range of the ultrasonic waves is 20 kHz to 1 GHz.

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