JP2014181931A - Treatment method and treatment device for radioactive silicone oil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment method and a treatment device that enables radioactive silicone oil to be mineralized and melted and solidified, stably without blocking an exhaust gas system.SOLUTION: First, radioactive silicone oil is decomposed by microorganisms in a decomposition vessel 12. Then, residues discharged by decomposition of the radioactive silicone oil are melted and solidified in a melting furnace 30.

Description

  The technique disclosed in this specification relates to a technique for treating radioactive silicon oil.

  A technique for treating silicon oil containing radioactive substances generated in a nuclear power plant has been developed (for example, Patent Document 1). In the technique of Patent Document 1, an oil coagulant is added to radioactive silicon oil, stirred to form an oil coagulated product, and stored and managed as an oil coagulated product.

JP 2001-129390 A

  In the technique of Patent Document 1, since radioactive silicon oil is used as an oil coagulated product, handling becomes easier as compared with the case where it is stored in a liquid state. However, since the oil coagulated product is a combustible material, it must be stored in the combustible material storage area as a combustible hazardous material. This specification discloses the technique which can mineralize radioactive silicon oil and can process appropriately.

In addition, as a process which mineralizes radioactive silicone oil, the process which incinerates radioactive silicone oil can be considered. However, when radioactive silicon oil is incinerated, a large amount of fine silicon oxide particles (SiO ₂ particles) are generated, which causes a problem of blocking an exhaust gas treatment system of an incineration facility.

  The method for treating radioactive silicon oil disclosed in the present specification includes a decomposition step of decomposing radioactive silicon oil by microorganisms, and a melt-solidifying step of melting and solidifying residues discharged in the decomposition step.

In the above treatment method, first, radioactive silicon oil is decomposed by microorganisms. For this reason, radioactive silicon oil can be mineralized without generating fine silicon oxide particles (SiO ₂ particles). And the residue of the radioactive silicon oil after decomposing | disassembling with microorganisms is melted and solidified. For this reason, in said processing method, without producing problems, such as obstruction | occlusion of an exhaust gas processing system, radioactive silicon oil can be mineralized and it can be set as the form suitable for disposal by melt-solidification.

  Moreover, the apparatus which processes radioactive silicon oil which this specification discloses has a melting tank which melts and solidifies the decomposition tank to which radioactive silicon oil and microorganisms are supplied, and the residue of the silicon oil discharged | emitted from a decomposition tank. According to this processing apparatus, the processing method disclosed in this specification can be suitably implemented.

  Details of the technology disclosed in this specification and further improvements will be described in detail in the detailed description and examples.

The whole block diagram of the processing system concerning a present Example. The figure for demonstrating schematic structure of the decomposition tank which concerns on a present Example. Schematic of the high frequency melting apparatus which concerns on a present Example.

  The main features of the embodiments described below are listed. The technical elements described below are independent technical elements and exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Absent.

In Feature 1 method for treating a radioactive silicone oil herein is disclosed, the microorganisms decompose the carbon component and hydrogen component of radioactive silicone oil, may contain SiO ₂ in the residue. According to such a structure, the combustible component of silicon oil can be decomposed | disassembled by microorganisms, and an inorganic substance can be made into a form suitable for disposal by a melt-solidification process.

(Characteristic 2) In the radioactive silicon oil processing method disclosed in this specification, the decomposition step may be performed in a state where the silicon oil is adsorbed on the adsorbent. In this case, the adsorbent may be formed of a material that can be decomposed by microorganisms. According to such a configuration, since the silicon oil is adsorbed on the adsorbent, the silicon oil can be held on the adsorbent while the silicon oil is decomposed by microorganisms. Moreover, since the adsorbent can also be decomposed by microorganisms, the adsorbent can be easily treated.

(Characteristic 3) The radioactive silicon oil processing method disclosed in the present specification further includes an incineration step of incinerating the silicon oil decomposed in the decomposition step and the adsorbent residue between the decomposition step and the melt solidification step. It may be. In this case, the incineration step may be performed after the microorganism completely decomposes the silicon oil in the decomposition step and before the microorganism completely decomposes the adsorbent. And a melt-solidification process may melt-solidify the residue discharged | emitted by an incineration process. According to such a configuration, since the incineration process is performed after the silicon oil is completely decomposed by the microorganisms, it is possible to avoid problems such as the exhaust gas treatment system being blocked by fine silica particles during the incineration. On the other hand, since the incineration process is performed before the adsorbent is completely decomposed by the microorganisms, the decomposition process can be shortened and the processing period can be shortened.

  Hereinafter, the processing apparatus 10 of the radioactive silicon oil which concerns on a present Example, and the processing method of the radioactive silicon oil using the processing apparatus 10 are demonstrated. As shown in FIG. 1, the processing apparatus 10 includes a decomposition tank 12 that decomposes radioactive silicon oil, and a melting furnace 30 that melts the residue discharged from the decomposition tank 12.

  As shown in FIG. 2, the decomposition tank 12 includes a tank 14 for storing radioactive silicon oil and microorganisms. To the tank 14, a silicon oil supply unit 16, a microorganism supply unit 18, a water supply unit 24, an air supply unit 26, an exhaust gas processing unit 28, and a melting furnace 30 are connected.

  The silicon oil supply unit 16 supplies radioactive silicon oil generated at the nuclear power plant to the tank 14. The silicon oil supply unit 16 can be configured by, for example, a storage tank (not shown) that stores radioactive silicon oil, and a supply pump (not shown) that supplies the radioactive silicon oil in the storage tank to the tank 14. In this case, the radioactive silicon oil in the storage tank is supplied to the tank 14 by operating the supply pump. The amount of radioactive silicon oil supplied to the tank 14 can be controlled by a supply pump.

The microorganism supply unit 18 supplies microorganisms to the tank 14. The microorganism supply unit 18 may be, for example, a supply device (for example, a screw feeder) that supplies an adsorbent containing microorganisms to the tank 14. In this case, the supply amount of the adsorbent supplied to the tank 14 is controlled by controlling the supply device. The adsorbent is made of a material capable of adsorbing oil (for example, natural plant-based materials (for example, wood-based materials (sawdust, etc.), regenerated cotton, nuts, etc.)). The adsorbent contains microorganisms that decompose silicon oil and nutrients that serve as nutrients for the microorganisms. Microorganisms that decompose silicon oil decompose carbon components (C components) and hydrogen components (H components) of radioactive silicon oil to produce carbon dioxide (CO ₂ ) and water (H ₂ O). As the microorganism, bacteria capable of decomposing a carbon component and a hydrogen component contained in oil can be used. In this embodiment, the adsorbent is a natural plant material, and the microorganism can decompose the adsorbent itself. For this reason, as will be described later, since the adsorbent itself is decomposed by microorganisms, the residue after the silicon oil decomposition can be easily processed. As such an adsorbent, for example, Ecot Sponge (registered trademark) manufactured and sold by Kaji Trading Co., Ltd. can be used.

  The water supply unit 24 supplies water to the tank 14. The water supply unit 24 can be configured by, for example, a water storage tank (not shown) for storing water and a pump (not shown) for supplying water in the water storage tank to the tank 14. A water pipe 24b is connected to the pump, and a water nozzle 24a is provided in the water pipe 24b. The watering nozzle 24 a is disposed in the tank 14. For this reason, the water discharged from the pump is jetted into the tank 14 from the watering nozzle 24a through the water distribution pipe 24b. As a result, water is supplied into the tank 14. The amount of water supplied into the tank 14 is controlled by a pump.

  The air supply unit 26 supplies air (oxygen) to the microorganisms in the tank 14. The air supply unit 26 can be configured by, for example, an air tank (not shown) that stores air (oxygen) and a pump (not shown) that supplies air in the air tank to the tank 14. Air supplied from the pump is supplied into the tank 14. Air (oxygen) supplied into the tank 14 is used by microorganisms contained in the adsorbent. The amount of air supplied into the tank 14 is controlled by a pump.

The exhaust gas processing unit 28 processes gas exhausted from the tank 14 (that is, carbon dioxide (CO ₂ ) generated by decomposing silicon oil by microorganisms). The exhaust gas processing unit 28 can be, for example, a filter (for example, a HEPA filter) that removes minute solids contained in the exhaust gas. By being processed by the exhaust gas processing unit 28, the harmless gas is discharged to the atmosphere.

  As described above, radioactive silicon oil is supplied from the silicon oil supply unit 16 to the tank 14, and an adsorbent containing microorganisms is supplied from the microorganism supply unit 18. For this reason, the mixed liquid of radioactive silicon oil and adsorbent is stationed in the tank 14. The water content of the mixed solution is measured by a moisture meter (not shown). The water supply unit 24 supplies water into the tank 14 according to the amount of moisture measured by the moisture meter, and the amount of moisture in the mixed solution is maintained at a moisture amount suitable for the activity of the microorganism. Moreover, the temperature of the liquid mixture of radioactive silicon oil and adsorbent is measured with a thermometer (not shown). By controlling a heater (not shown) based on the temperature measured by the thermometer, the temperature of the mixed solution is maintained at a temperature at which microorganisms can easily act. By these, the action of microorganisms in the mixed solution is activated.

  In the tank 14, a stirring blade 22 b for stirring the mixed liquid (mixed liquid of radioactive silicon oil and adsorbent) in the tank 14 is disposed. The stirring blade 22b is connected to the motor 20 by a drive shaft 22b. When the stirring blade 22b is rotated by the motor 20, the liquid mixture is stirred and air (oxygen) is supplied to the microorganisms. This promotes the decomposition of radioactive silicon oil by microorganisms. Note that a discharge port 14 is provided at the bottom of the tank 14 for discharging residues after decomposition by microorganisms. Moisture is removed from the residue discharged from the discharge port 14 and supplied to a melting furnace 30 described below.

  Next, the melting furnace 30 will be described with reference to FIG. In this embodiment, a high frequency melting apparatus is used as the melting furnace 30. As shown in FIG. 3, the high-frequency melting apparatus 30 includes a furnace body 58, a lid body 64 attached to the upper end of the furnace body 58, and an elevating device 44 disposed below the furnace body 58. The furnace body 58 includes a furnace body 54, a cooling nozzle 42, and an induction heating coil 40 disposed along the outer peripheral surface of the furnace body 54. The furnace body 54 is formed in a cylindrical shape with an upper end and a lower end opened, and an accommodation space 56 is provided therein. In the accommodation space 56, the melting container 38 can be accommodated. A charging port 60 is provided at the upper end of the furnace body 54, and an opening 50 is provided at the lower end of the furnace body 54. The input port 60 and the opening 50 communicate with the accommodation space 56. The opening 50 is formed in a size that allows the melting container 38 to pass therethrough. The charging port 60 is formed to be smaller than the opening 50 and has a size that the melting container 38 cannot pass through. The cooling nozzle 42 is disposed in the lower part of the furnace body 54 so as to penetrate the outer wall of the furnace body 58 and the furnace body 54. A space is formed between the outer wall of the furnace body 58 and the furnace body 54. The induction heating coil 40 is held in the cavity by a holding arm (not shown). The induction heating coil 40 is disposed so as to cover the side surface of the melting vessel 38 through the furnace body 54. The induction heating coil 40 is connected to a high-frequency power source (50 to 3000 Hz) (not shown).

  The lid body 64 is attached to the upper end of the furnace body 58. When the lid body 64 is attached to the furnace body 58, the charging port 60 at the upper end of the furnace body 54 is closed. A charging machine 32 is installed on the lid 64. The charging machine 32 is disposed above the charging port 60 (that is, the accommodation space 56) of the furnace body 54. The input machine 32 inputs solid waste into the melting container 38. The residue discharged from the tank 14 (residue after decomposition of radioactive silicon oil) can be put in the melting container 38 in advance. The lid 64 is provided with a nozzle 62. The nozzle 62 communicates with the accommodation space 56 of the furnace body 54. The nozzle 62 is used when melting liquid waste. The lid 64 is provided with an exhaust gas outlet 34. The exhaust gas outlet 34 communicates with the accommodation space 56 of the furnace body 54. The exhaust gas outlet 34 discharges gas generated during the melting process. An exhaust gas treatment device (for example, a HEPA filter) (not shown) is connected to the exhaust gas outlet 34. The exhaust gas discharged from the exhaust gas outlet 34 is rendered harmless by the exhaust gas treatment device and discharged to the atmosphere.

  The lifting device 44 includes a flat table 48 and a lifting mechanism (not shown) that lifts and lowers the flat table 48. The abutment 52 is placed on the flat table 48, and the melting container 38 is placed on the abutment 52. When the flat table 48 is raised to the upper end position (position indicated by the solid line in FIG. 3) by the lifting mechanism, the lower end of the accommodation space 56 is closed. When the plane table 48 is lowered to the lower end position (position indicated by the two-dot chain line in FIG. 3) by the lifting mechanism, the lower end of the accommodation space 56 is opened.

  The melting vessel 38 is a bottomed vessel and is made of a conductive ceramic containing carbon. When a high frequency power source is applied to the induction heating coil 40, an eddy current flows in the melting vessel 38, and the melting vessel 38 can be suitably heated. The temperature of the melting container 38 can be controlled by adjusting the electrical resistivity and thickness of the melting container 38.

  Next, a method for processing silicon oil by the processing apparatus 10 according to the present embodiment will be described. In this embodiment, first, radioactive silicon oil is decomposed by microorganisms in the decomposition tank 12, and the residue after the decomposition treatment by microorganisms is melted in the melting furnace 30. First, a process for decomposing radioactive silicon oil with microorganisms in the decomposition tank 12 will be described.

  First, radioactive silicon oil is supplied to the tank 14 from the silicon oil supply unit 16, and an adsorbent containing microorganisms is supplied from the microorganism supply unit 18. As a result, the mixed liquid of radioactive silicon oil and adsorbent is stored in the tank 14. In the mixed solution, the radioactive silicon oil is adsorbed by the adsorbent, and in this state, the decomposition treatment by microorganisms is performed. When the microorganisms are decomposed, water is supplied from the water supply unit 24, and the temperature in the tank 14 is maintained at an appropriate temperature by a heater (not shown). Air (oxygen) is supplied from the air supply unit 26 into the tank 14. The supplied air is supplied to the microorganisms in the mixed solution by the stirring blade 22b stirring the mixed solution. This promotes the decomposition of radioactive silicon oil by microorganisms.

When microorganisms decompose the radioactive silicon oil, the carbon component of the radioactive silicon oil becomes carbon dioxide (CO ₂ ), and the hydrogen component of the radioactive silicon oil becomes water (H ₂ O). Thereby, radioactive silicon oil is mineralized and silicon oxide (SiO ₂ ) is generated as a residue. The particle size (about several tens of μm) of silicon oxide (SiO ₂ ) contained in the residue is larger than the particle size of silicon oxide (SiO ₂ ) (1 μm or less is about 65% or more) that is generated when radioactive silicon oil is incinerated. growing. The reason why the particle size of silicon oxide (SiO ₂ ) is large is assumed to be due to the following reason. That is, when radioactive silicon oil is decomposed by microorganisms, siloxane molecules (CH ₃ —Si—O—Si...) In the radioactive silicon oil do not volatilize / diffuse, and contain organic components (ie, carbon components (C components)). ), Hydrogen component (H component)) is slowly decomposed. Therefore, it is inferred that the particle size of silicon oxide in the residue (SiO ₂₎ is increased.

  Further, as described above, the adsorbent can be decomposed by microorganisms, and the organic components of the adsorbent introduced into the tank 14 are also decomposed by microorganisms. For this reason, the organic component is not contained in the residue discharged | emitted from the decomposition tank 12, and problems, such as an organic component burning in a melt process, do not arise. The exhaust gas generated by decomposing the radioactive silicon oil and the adsorbent with microorganisms is rendered harmless by the exhaust gas processing unit 28 and released to the atmosphere.

  Residue (mainly silicon oxide) generated by being decomposed by microorganisms in the decomposition tank 12 is discharged from the discharge port 14 a of the tank 14. Moisture is removed from the residue discharged from the decomposition tank 12 and is transported to the melting furnace 30. The residue conveyed to the melting furnace 30 is melted and solidified in the melting furnace 30. In order to melt and solidify the residue, first, the elevating device 44 is driven to position the flat table 48 at the lower end position (position indicated by the two-dot chain line in FIG. 3). Next, the abutment 52 is placed on the flat table 48, and the melting container 38 is placed on the abutment 52. The melting vessel 38 is loaded with the residue discharged from the decomposition tank 12 in advance. Next, the elevating device 44 is raised until the flat table 48 contacts the lower surface of the furnace body 58. As a result, the melting container 38 disposed on the abutment 52 is accommodated in the accommodating space 56 of the furnace body 54.

Next, a high frequency power source is applied to the induction heating coil 40. As a result, an eddy current is generated in the melting container 38 and the melting container 38 generates heat. When the temperature of the melting container 38 rises, the residue (that is, mainly silicon oxide (SiO ₂ )) charged inside the melting container 38 is melted. The gas generated during the melting process is discharged from the exhaust gas outlet 34 and processed in the exhaust gas processing apparatus. When the melting process is completed, the melting container 38 is unloaded from the high-frequency melting device 30. Next, the unloaded melting vessel 38 is moved to the cooling chamber 46, and the molten metal inside is cooled and solidified. The molten container 38 obtained by cooling and solidifying the molten metal is discarded in a predetermined storage facility. In the present embodiment, the melting container 38 is discarded, but the melting container 38 may be loaded into a predetermined container and then discarded.

Here, silicon oxide (SiO ₂ ) contained in the residue melted in the melting furnace 30 has a relatively large particle size. For this reason, scattering in the gas exhausted from the melting furnace 30 is suppressed, and problems such as blockage of the exhaust gas processing device are suppressed. Thereby, most of the residue discharged from the decomposition tank 12 can be appropriately melted and solidified.

In the processing apparatus 10 of the present embodiment, the particle size of silicon oxide (SiO ₂ ) contained in the residue after decomposing the radioactive silicon oil can be made relatively large by decomposing the radioactive silicon oil with microorganisms. . For this reason, in the subsequent melting process, the residue after the decomposition process can be appropriately melted and solidified.

  As mentioned above, although one Example of the technique disclosed by this specification was described in detail, this is only an illustration and does not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

  In the embodiment described above, the adsorbent that adsorbs the radioactive silicon oil is completely decomposed by microorganisms, and then the melting treatment is performed. However, the technique of the present specification is not limited to such a form. For example, the decomposition process may be terminated at a timing when all or most of the radioactive silicon oil is decomposed by microorganisms and the adsorbent is not completely decomposed by microorganisms. Since the decomposition process is stopped before the adsorbent is completely decomposed by microorganisms, the period required for the decomposition process can be greatly shortened.

  If the decomposition treatment is stopped before the adsorbent is completely decomposed by microorganisms, the residue contains organic components (C component, H component) of the adsorbent. For this reason, it is preferable to melt the residue discharged by the decomposition treatment after incineration. Since the residue after the decomposition treatment is mineralized and then melted, the melting treatment can be appropriately performed.

Here, even if the residue discharged by the decomposition treatment is incinerated, problems such as blockage of the exhaust gas treatment system do not occur. In other words, when radioactive silicon oil is incinerated as it is, the exhaust gas treatment system is blocked by fine silicon oxide (SiO ₂ ) particles. The problem does not occur. The reason why the exhaust gas treatment system is not blocked is assumed to be due to the following reason. That is, when radioactive silicon oil is incinerated at a high temperature (for example, about 800 ° C.) as it is, the siloxane molecules (CH ₃ —Si—O—Si...) Forming the silicon oil are rapidly volatilized, diffused, and oxidized. , C component and H component become CO ₂ and H ₂ O, and fine particles of silicon oxide (SiO ₂ ) are formed. For this reason, the fine particles of silicon oxide (SiO ₂ ) formed have a particle size of 10 μm or less of about 80% or more (1 μm or less is about 65%), and clog the exhaust gas treatment system (for example, a ceramic filter). On the other hand, when radioactive silicon oil is decomposed by microorganisms, the siloxane molecules forming the silicon oil do not volatilize and diffuse, and the contained organic components (C and H components) are slowly decomposed. Since there is no rapid volatilization / diffusion of siloxane molecules, the formed silicon oxide (SiO ₂ ) does not become fine particles but a residue having a large particle size (residue of several tens of microns or more). For this reason, it is presumed that even if the residue (silicon oxide (SiO ₂ )) and the adsorbent are incinerated, the silicon oxide does not become fine particles and the blockage of the exhaust gas treatment system is suppressed.

  Moreover, the structure of the decomposition tank 12 for decomposing | disassembling radioactive silicon oil can be suitably changed according to the property of the microorganisms used for decomposition | disassembly of radioactive silicon oil. Moreover, about the structure of the melting furnace which melt | dissolves the residue after a decomposition process, melting furnaces other than a high frequency melting furnace can be used.

  The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

10 Processing device 12 Decomposition tank 30 Melting furnace

Claims (5)

A method of treating radioactive silicon oil,
A decomposition step of decomposing the radioactive silicon oil by microorganisms;
And a melting and solidifying step of melting and solidifying the residue discharged in the decomposition step. The microorganism decomposes the carbon component and hydrogen component of the radioactive silicon oil,
The method for treating radioactive silicon oil according to claim 1, wherein the residue contains SiO ₂ . The decomposition step is performed in a state where the silicon oil is adsorbed on an adsorbent,
The silicon adsorbent treatment method according to claim 1, wherein the adsorbent is formed of a material that can be decomposed by the microorganism. Between the decomposition step and the melt-solidification step, further comprises an incineration step of incinerating the silicon oil decomposed in the decomposition step and the adsorbent residue,
The incineration step is performed after the microorganism completely decomposes the silicone oil in the decomposition step and before the microorganism completely decomposes the adsorbent,
The silicon oil treatment method according to claim 3, wherein the melting and solidifying step melts and solidifies the residue discharged in the incineration step. It is a device that processes radioactive silicon oil,
A decomposition tank to which the radioactive silicon oil and microorganisms are supplied;
A processing device for radioactive silicon oil, comprising: a melting and solidifying device for melting and solidifying the residue of the silicon oil discharged from the decomposition tank.

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