JP2014228360A - Decontamination device and decontamination method of radioactive contamination soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply place/remove a decontamination device in a short time and efficiently accumulate a radioactive substance without being stayed at a decontaminated site to decontaminate radioactive contaminated soil.SOLUTION: A decontamination device 1 includes an AC power supply 2, positive/negative electrode members 3 and 4 connected to the power supply 2 and a water supply device 5. Two or more pairs of the positive/negative electrode members 3 and 4 are alternately mounted nearly in parallel on a soil surface having a range covering an area to be decontaminated. The electrode members 3 and 4 are formed by sticking a radioactive substance adsorbent to an ordinary electrode material. A decontamination method comprises: wetting a contaminated soil by the water supply device 5; applying voltage between the electrode members 3 and 4 by the power supply 2; ionizing a radioactive substance penetrated into a soil surface layer part; adsorbing the radioactive substance to the electrode member 3 by an electrokinetic phenomenon (electrolysis, electrophoresis and electro-osmosis, etc.); and accelerating the adsorption by the radioactive substance adsorbent to accumulate the radioactive substance to the electrode member 3.

Description

  The present invention relates to an apparatus and method for decontaminating soil by adsorbing and collecting soil contaminants contaminated with radioactive substances.

There is an urgent need to take measures against soil contamination caused by radioactive materials released in large quantities from the Fukushima Daiichi Nuclear Power Station due to the Tohoku Earthquake. As a decontamination measure for contaminated soil, the excavated and removed soil is stored in a flexible container bag, etc., and stored in a temporary storage area for a specified period of time, or classified by washing and separating fine particles containing a large amount of radioactive material from contaminated soil Cleaning methods are mainstream.
On the other hand, an electrode rod connected to the anode of the DC power supply is inserted into the contaminated area of the ground, and an electrode body connected to the cathode of the DC power supply is inserted into the well drilled outside the contaminated area. There is a method for remediating contaminated soil by applying a DC voltage to the body to cause forced drainage into the groundwater well due to electroosmosis, and removing the contaminant from the well by pumping it up with the groundwater (patent) Reference 1).

Japanese Patent Laid-Open No. 10-309562

In any of the above conventional methods, it is difficult to reliably reduce the volume of contaminated soil in a short period of time. Therefore, the exposure risk of workers during collection and transportation of contaminated soil, and the isolation of a large amount of contaminated soil・ There are problems such as securing a storage location, occupation of the storage location for a long period of time, risk of secondary contamination around the storage location, and expansion of groundwater contamination due to long-term storage until decontamination activities. In forests, slopes and other rough terrain, it is difficult to continue the decontamination work depending on the site environment.
Therefore, the present invention is a simple installation work in a short time, and an operator efficiently collects radioactive materials without staying at the site to be decontaminated for a long time. The present invention provides a decontamination apparatus and a decontamination method for radioactively contaminated soil, which is effective for decontamination in an area where the risk of secondary contamination and the spread of contamination are reduced and where continuous work is difficult.

  A decontamination apparatus 1 for radioactively contaminated soil that adsorbs and collects radioactive substances from a soil surface layer contaminated with radioactive substances, and places electrode members 3 and 4 containing radioactive substance adsorbents on the soil surface of the decontamination target area. The radioactive material in the soil is adsorbed and recovered by the electrokinetic phenomenon caused by the electric field formed by the electrode members 3 and 4.

  In the present invention, since the electrode member mounting and collection operations are simple and completed in a short time, it is not necessary to stay at the decontamination site for a long time, the exposure risk can be reduced, and radioactive substances can be efficiently recovered, It has the effect of reducing the labor for transportation and storage, eliminating the need for a vast storage location, and preventing the risk of secondary contamination and the spread of contamination to the surrounding environment.

It is a schematic perspective view of the installation state of the decontamination apparatus which concerns on 1st Example of this invention. It is a front view of the installation state of an electrode member. It is principle explanatory drawing of the decontamination apparatus of FIG. It is a front view of the modification of the decontamination apparatus of FIG. It is a front view of the other modification of the decontamination apparatus of FIG. It is a front view of the installation state of the decontamination apparatus concerning 2nd Example of this invention. It is a top view of the installation state of the decontamination apparatus of FIG. It is principle explanatory drawing of the decontamination apparatus of FIG. It is principle explanatory drawing of the decontamination apparatus concerning 3rd Example of this invention. It is principle explanatory drawing of the modification of the decontamination apparatus of FIG.

Embodiments of the present invention will be described with reference to the drawings.
1 to 3, a radioactively contaminated soil decontamination apparatus 1 according to a first embodiment of the present invention includes a DC power source 2, positive and negative electrode members 3 and 4 connected to the power source 2, and a water supply device. And 5. The power source 2 uses a power line near the installation position or a separately installed fuel generator, storage battery, solar cell, electric double layer capacitor, etc., while reversing the polarity continuously or intermittently or at predetermined intervals. It is thrown.

  The electrode members 3 and 4 are placed on a soil surface in a range covering the decontamination target region in a plurality of pairs arranged alternately in parallel with each other in a positive and negative manner. The electrode members 3 and 4 have a long bar shape, and are configured by attaching a radioactive substance adsorbent to a general electrode material such as metal or carbon. As the radioactive material adsorbent, a known material such as zeolite, layered clay mineral or ferrocyanide-based adsorbent having the ability to adsorb radioactive materials may be used, and a plurality of these may be mixed. The electrode members 3 and 4 may be formed by mixing a powdered electrode material such as carbon powder, sludge incineration ash, peat (peat) or iron powder and a radioactive substance adsorbent. In addition, the electrode members 3 and 4 are formed in a bag-like casing made of a water-permeable material having strength and flexibility that does not easily break, and a powder or granular electrode material, and also a powder or granular radioactive material adsorbent. May be configured. Furthermore, the electrode members 3 and 4 may be configured in a tape shape by attaching a powdery or granular electrode material and a radioactive substance adsorbent to the tape base material, or metal plating or a metal thin film on one surface of the tape base material. Alternatively, a conductive layer may be formed by sticking, and a radioactive substance adsorbent may be attached to the conductive layer. Thus, if the electrode members 3 and 4 are formed in a tape shape and can be wound up, handling, installation and recovery can be easily performed.

  In order to promote the electrokinetic phenomenon, the water supply device 5 is provided with a water distribution pipe 5a having a large number of drip water supply holes between the electrode members 3 and 4, and supplies water as necessary to keep the soil surface layer moist. Do. The water supply device 5 can be applied to water tanks, agricultural waterways, rivers, rainwater storage tanks, etc. in addition to tanks installed separately, and salt, oxalic acid, etc. for promoting electrokinetic phenomena are added to the water supply as electrolysis auxiliary agents May be.

  The decontamination apparatus 1 of this embodiment places a plurality of electrode members 3 and 4 alternately on the surface of the contaminated soil in the decontamination target area on the land contaminated with radioactive substances at almost equal intervals. If the power supply 2 is turned on using the fixing means accordingly, the installation work is completed. In addition, the mutual space | interval of the electrode members 3 and 4 shall be about several to several dozen centimeters. As shown in FIG. 3, the radioactive material contained in the soil surface layer is ionized by the electric field generated between the electrode members 3 and 4 connected to the power source 2, and electrokinetic phenomena (electrolysis, electrophoresis, electroosmosis, etc.) ), The radioactive material that has become cations is eluted, adsorbed on the radioactive material adsorbent, and gradually accumulated in the negative electrode member 3. Therefore, the contaminated soil can be decontaminated if the radioactive material is collected and removed together with the removal of the electrode members 3 and 4. In particular, soil contamination resulting from the Fukushima Daiichi nuclear accident is effective in the efficient recovery of radioactive materials with a shallow penetration depth, since radioactive materials penetrate into a relatively shallow soil surface of about 5 cm from the surface. It is.

  As shown in FIG. 4, the electrode members 3 and 4 are installed by forming a groove S formed on the surface of the contaminated soil in the decontamination target region, and disposing the electrode members 3 and 4 in the groove S. Increases the efficiency of pollutant adsorption. The groove S can be used for agricultural plows, and is particularly convenient for agricultural land.

  In addition, as shown in FIG. 5, the decontamination apparatus 1 can be installed on an inclined surface, and it is difficult to continue the decontamination work depending on the field environment such as a mountain forest, a slope of a built-up land, and rough terrain. It is also effective for the areas involved.

  The decontamination apparatus 6 of 2nd Example is shown in FIGS. 6-8. 6 and 7, the decontamination device 6 includes the above-described water supply device 5 as necessary, and the electrode member 7 has a sheet shape covering the contaminated soil surface of the decontamination target region, and the solar cells are integrated. Prepare for. As shown in FIG. 8, the electrode member 7 includes a sheet base material 8, a solar cell film 9 bonded to the surface of the sheet base material 8, a conductive layer 10 formed on the back surface of the sheet base material 8, A radioactive substance adsorbing layer 11 in which a radioactive substance adsorbing agent is attached to the conductive layer 10 and a space projecting from the conductive layer 10 and the radioactive substance adsorbing layer 11 which are implanted on the back surface of the sheet substrate 8 are spaced apart from each other. It is comprised from the some anode pile 12 arrange | positioned.

  The sheet | seat base material 8 consists of a raw material which has the water | permeable permeability which can ensure the intensity | strength which is not damaged easily, the penetration | invasion of rainwater to object soil, and the foldable softness | flexibility.

  The solar cell film 9 is detachably bonded to the sheet substrate 8 by a hook-and-loop fastener or other known bonding means. As the solar cell film 9, a dye-sensitized solar cell that can be thinned is applied. The solar cell film 9 is stacked in such a manner that the sheet base material 8 is partially exposed to ensure water permeability.

  The conductive layer 10 is formed on the sheet base 8 by metal plating or metal thin film sticking. The conductive layer 10 is electrically connected to the negative electrode of the solar cell film 9. The conductive layer 10 may have a configuration in which the above-described electrode material in powder or granular form is attached to the sheet substrate 8.

  The radioactive substance adsorbing layer 11 is formed by adhering the above-mentioned radioactive substance adsorbent in powder or granular form to the conductive layer 10, or adhering to the sheet substrate 8 integrally with the above-mentioned electrode substance in powder or granular form.

  The anode pile 12 is electrically connected to the positive electrode of the solar cell film 9 via a covered electric wire, fixed so as to rise from the sheet base material 8, and inserted into the contaminated soil surface layer. The anode pile 12 is made of metal or carbon that does not contain harmful heavy metals such as chromium, lead, arsenic, cadmium, etc., which cause soil contamination, and is covered with a material that is resistant to oxidation damage due to application of positive voltage. May be.

  In the decontamination apparatus 6 of this embodiment, similarly to the previous embodiment, the electrode members 7 are spread while inserting the anode piles 12 so as to cover the soil surface of the decontamination target area in the land contaminated with the radioactive material. As shown in FIG. 8, in the electrode member 7, the solar cell film 9 generates power upon receiving sunlight indicated by an arrow, and the electric field is applied to the surface-contaminated soil between the periphery of the anode pile 12 with the conductive layer 10 serving as a cathode. As a result of causing electrokinetic phenomena, promoting ionization of radioactive substances contained in the surface layer of the soil by electrolysis, and attracting radioactive substances ionized by electrophoresis or electroosmotic flow to the conductive layer 10, Since the radioactive substance is adsorbed on the radioactive substance adsorption layer 11 and gradually accumulates, the contaminated soil can be decontaminated by removing the electrode member 7 and collecting the radioactive substance.

  A decontamination apparatus 13 of the third embodiment is shown in FIG. In the figure, the decontamination device 13 includes the above-described water supply device (not shown) as necessary, and the electrode member 14 is formed in a long bar shape, and a plurality of pairs are arranged substantially parallel to the soil surface in a range covering the decontamination target region. It is to be placed. The electrode member 14 includes the above-described mixture of the powdery or granular electrode material, the powdery or granular electron supply material, and the powdery or granular radioactive substance adsorbent described above, and the long bag described above. The cylindrical casing 15 is filled. As the electron supply material, a known material such as a reducing agent or a dye sensitizer that supplies electrons to the soil surface when the electrode member 14 comes into contact with the soil surface and generates a redox potential difference is used.

  In the decontamination apparatus 13 of this embodiment, in the same manner as in the previous embodiment, the electrode members 14 are arranged almost parallel to each other on the contaminated soil surface in the decontamination target area in the land contaminated with radioactive substances, If necessary, take measures that do not move easily using fixing means. The installation interval of the electrode member 14 is about several to several tens of centimeters. As shown in FIG. 9, the electrode member 14 that has supplied electrons to the soil by the electron supply material generates an oxidation-reduction potential difference, and makes the soil surface layer portion relatively anodic, thereby expressing an electrokinetic phenomenon, Thereby, if a radioactive substance adsorb | sucks to a radioactive substance adsorbent and is gradually accumulate | stored and a radioactive substance is collect | recovered with the removal of the electrode member 14, a contaminated soil will be decontaminated.

  As shown in FIG. 10, the electrode member 14 is electrically connected to the anode pile 18 inserted into the contaminated soil in the decontamination target region via the electric resistance 17, so that electrons between the electrode member 14 and the electrode member 14 can be electrically connected. The transfer can be performed smoothly, and the contact potential difference can be increased to promote the electrokinetic phenomenon.

  Note that the electrode member 14 may be disposed in a groove formed in the midway surface as in the first embodiment. The electrode member 14 may be configured in a sheet shape or a tape shape by adhering a powdery or granular electrode material, an electron supply material, and a radioactive substance adsorbent to a sheet base material or a tape base material. A conductive layer may be formed on one surface of the material by applying metal plating or a metal thin film, and an electron supply material and a radioactive substance adsorbent may be attached to the conductive layer.

DESCRIPTION OF SYMBOLS 1 Decontamination apparatus 2 Power supply 3 Electrode member 4 Electrode member 5 Water supply apparatus 5a Water distribution pipe 6 Decontamination apparatus 7 Electrode member 8 Sheet base material 9 Solar cell film 10 Conductive layer 11 Radioactive substance adsorption layer 12 Anode pile 13 Decontamination apparatus 14 Electrode Member 15 Casing 16 Mixture 17 Electric resistance 18 Anode pile

Claims (13)

In decontamination equipment for radioactively contaminated soil that absorbs and recovers radioactive material from surface soil contaminated with radioactive material,
It is placed on the soil surface of the decontamination target area and comprises an electrode member containing a radioactive substance adsorbent,
A decontamination apparatus for radioactively contaminated soil, characterized in that radioactive substances in the soil are adsorbed to an electrode member by electrokinetic phenomenon and recovered and disposed of.   A power source to which the electrode member is connected is provided, and a plurality of electrode members are alternately placed on the soil surface of the decontamination target area in parallel in a positive and negative manner, and an electrokinetic phenomenon is generated by the voltage between the electrode members. The decontamination apparatus for radioactively contaminated soil according to claim 1, wherein   The said power supply is a solar cell, The decontamination apparatus of the radioactive contamination soil of Claim 2 characterized by the above-mentioned.   The electrode member includes a water-permeable sheet base material, a dye-sensitized solar cell film that is detachably attached to the surface of the water-permeable sheet base material, and a radioactive substance adhering to the back surface of the water-permeable sheet base material The decontamination apparatus for radioactively contaminated soil according to claim 3, comprising an agent and an anode pile electrically connected to the solar cell film and inserted into the soil.   2. The radioactively contaminated soil according to claim 1, wherein the electrode member includes an electron supply material, and a soil surface with which the electrode member contacts has a relatively negative polarity to cause the electrokinetic phenomenon. Decontamination equipment.   6. The radioactively contaminated soil decontamination apparatus according to claim 1, further comprising water supply means for moistening the soil in order to promote an electrokinetic phenomenon due to the electric field of the electrode member.   The decontamination apparatus for radioactively contaminated soil according to any one of claims 1 to 6, wherein the electrode member is in the form of a windable tape or a foldable sheet.   The electrode member is characterized in that a conductive layer is formed on at least one surface of a water-permeable sheet substrate or a tape substrate by metal plating or metal thin film adhesion, and the radioactive substance adsorbent is attached to the conductive layer. The decontamination apparatus for radioactively contaminated soil according to claim 7.   The decontamination apparatus for radioactively contaminated soil according to any one of claims 1 to 8, wherein the radioactive substance adsorbent contains at least one of zeolite, a layered clay mineral, or an iron ferrocyanide compound.   The electrode member is filled in a water-permeable casing by mixing a powder or granular electrode material and the powder or granular radioactive material adsorbent. The decontamination apparatus for radioactively contaminated soil according to 6 or 8.   The electrode member is placed on the soil surface of the decontamination target area, and radioactive material in the soil is adsorbed by an electrokinetic phenomenon caused by the electric field formed by the electrode member, and recovered and disposed of. A decontamination method using the decontamination apparatus according to claim 1, wherein the decontamination apparatus is used.   The said electrode member is arrange | positioned in the groove | channel formed in the soil surface, The decontamination method using the decontamination apparatus of the radioactive contamination soil characterized by the above-mentioned.   A decontamination method using a decontamination apparatus for radioactively contaminated soil, wherein the groove is formed with an agricultural plow.

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