JP5767194B2 - Radioactive material processing system and processing method - Google Patents

Description

  The present invention relates to a processing system and a processing method for separating and removing radioactive substances from incineration ash and the like.

The Fukushima Daiichi nuclear power plant accident occurred on March 11, 2011, and radioactive materials including radionuclides such as ¹³¹ I, ¹³⁴ Cs, ¹³⁷ Cs, and ⁹⁰ Sr were released from the nuclear power plant. Has been widely spread. After that, the phenomenon that diffused radioactive material is concentrated in specific areas and facilities has been confirmed in various places, and this phenomenon is called “urban enrichment” and has become a problem. Specifically, the diffused radioactive material tends to collect in specific places in rivers and sewers, or in depressions that become puddles when it rains, and is concentrated in such places. The phenomenon has been confirmed. In addition, it has been confirmed that the radioactive substance is concentrated in the incineration ash when the garbage containing the radioactive substance is incinerated. Incineration ash includes main ash recovered from the bottom of the incinerator and fly ash floating in the incineration exhaust gas, and it is known that radioactive substances tend to be mixed more in fly ash than main ash. ing. Such radioactive sludge, soil, and incineration ash can be stored or landfilled, but the amount of sludge, soil, or incineration ash mixed with radioactive material is enormous, and it must be stored or landfilled. Therefore, there is a problem that it is difficult to secure a site for the purpose. Moreover, since incinerated ash is in the form of powder, there is a concern that radioactive materials may leak around the storage and landfill sites and underground. It should be noted that the half-life of ¹³¹ I is as short as about 8 days, so the effect of ¹³¹ I is considered negligible, but the half-lives of ¹³⁴ Cs, ¹³⁷ Cs, and ⁹⁰ Sr are 2.1 years and 30.1 years, respectively. , About 28.8 years, there is concern over medium- to long-term effects.

  By the way, incineration ash at a garbage incineration plant may contain contaminants such as PCB, asbestos, dioxin, etc. in addition to radioactive materials. As a treatment method for such contaminants, incineration ash is melted and solidified. A method of detoxifying while reducing the volume is known (for example, see Patent Document 1). More specifically, by heating the incineration ash to a high temperature of, for example, 1000 ° C. or more, the incineration ash is melted and contaminants such as PCB, asbestos and dioxin are decomposed or melted and rendered harmless. The molten incinerated ash is called molten slag and is poured into cooling water to solidify into rocky or glassy pebbles. The volume of incinerated ash is reduced to about 1/2 by becoming molten slag. Molten slag is harmless and is used as civil engineering material.

However, radioactive materials containing radionuclides such as ¹³⁴ Cs, ¹³⁷ Cs, and ⁹⁰ Sr have a problem of maintaining radioactivity without being rendered harmless even when heated. For example, even if the incineration ash is heated in the melting furnace, a part of the incineration ash may not be melted but become fine particles called molten fly ash and float in the off-gas. In this case, it is known that more radioactive material tends to be detected in molten fly ash than in molten slag. Although molten fly ash is collected by a dust collector such as a bag filter and is reduced in volume from the original incinerated ash, further volume reduction is desirable for storage and landfill.

  On the other hand, a method has been proposed in which molten fly ash is washed to extract radioactive cesium into water, and the radioactive cesium transferred to water is coagulated and precipitated using Prussian blue to separate and remove (for example, non-patent Reference 1). In addition, a technique has been proposed in which radioactive substances in a liquid are captured by a magnetic composite particle for decontamination and collected by a magnetic force collecting means (see, for example, Patent Document 2).

  In addition, the radioactive material is volatilized by heating the processing object containing the radioactive material containing cesium by a rotary sublimation apparatus instead of a melting furnace, and the off-gas containing the volatilized radioactive material is cooled to convert the radioactive material into a particulate form. There has been proposed a method of returning to a solid and collecting it with a bag filter (see, for example, Non-Patent Document 2).

Japanese Patent No. 4004181 Japanese Patent No. 4932004

“Development of technology for separation and removal of radioactive cesium from molten fly ash” [online], Ataca Daiki Co., Ltd. [searched November 1, 2012], Internet (http: //www.atk-dk. com.xml / docs / ATK_186.pdf) “Press Release 2011, Decontamination Technology Demonstration Project” [online], National Institute of Agriculture, [Searched November 1, 2012], Internet (http://www.naro.affrc.go.jp/ publicity_report / press / laboratory / narc / 027564.html)

  However, the technique of washing molten fly ash with water has a problem that water-soluble radioactive substances can be removed from molten fly ash, but water-insoluble radioactive substances cannot be removed. Moreover, even if it is a water-soluble radioactive substance, if it is adsorbed by fine particles such as molten fly ash, it may be difficult to dissolve in water, and the radioactive substance adsorbed by such fine particles cannot be removed. There is also a problem. Also, there is a problem that handling of the molten fly ash is complicated in order to collect the molten fly ash from a dust collector such as a bag filter and clean it again with a separate device, and in addition, measures against the exposure are required.

  On the other hand, the method of volatilizing radioactive substances containing cesium with a rotary sublimation apparatus can remove most of the radioactive substances from the object to be treated, but this technique also completely removes the radioactive substances from the object to be treated. In the case where the concentration of the radioactive substance in the object to be processed is extremely high, there is a possibility that the radioactive substance having a concentration exceeding a predetermined standard may remain in the object to be processed after the heat treatment. In such a case, even if the concentration of the radioactive substance is lower than that before the treatment, the object to be treated after the heat treatment needs to be disposed of by storage or landfill. Since the object to be treated after the heat treatment is in a powder form, there is a concern that radioactive substances may leak out to the vicinity of the land for storage or landfill or in the basement in the medium to long term. Moreover, when the density | concentration of the radioactive substance of the processing target object after heat processing is high, in order to prevent scattering of a powdery processing target object, conveyance may be restrict | limited. That is, there is a problem that a processing object having a high concentration of radioactive substance is not suitable as a processing object. In addition, depending on the object to be treated, not only radioactive substances but also non-radioactive substances may be volatilized together with radioactive substances and recovered together with radioactive substances. Therefore, a sufficient volume reduction effect may not be obtained depending on the object to be processed.

  The present invention has been made in view of the above problems, and is a radioactive substance that is easy to handle and can handle a processing object containing a radioactive substance that is difficult to dissolve in water or a processing object having a high concentration of radioactive substance. It is an object to provide a processing system and a processing method.

The present invention is for volatilizing and removing a radioactive substance in an off-gas while heating and melting a processing object containing a radioactive substance containing at least one radionuclide of ¹³⁴ Cs, ¹³⁷ Cs and ⁹⁰ Sr at 1300 ° C. or higher. A melting furnace, a smoke cleaning unit for cleaning off-gas discharged from the melting furnace with smoke-washing water, and separating radioactive substances contained in the off-gas from off-gas to smoke-washing water, and off-gas washed with the smoke cleaning unit A dust collection unit for recovering molten fly ash mixed in the dust, a transport unit for reprocessing molten fly ash for transporting the molten fly ash collected in the dust collection unit to a melting furnace for reprocessing, and radioactive The above-mentioned problem is solved by a radioactive substance processing system comprising a radioactive substance recovery unit for recovering a substance from smoke-washed water.

In addition, the present invention provides a radioactive material in an off-gas while melting a processing object in which a radioactive material containing at least one radionuclide of ¹³⁴ Cs, ¹³⁷ Cs and ⁹⁰ Sr is mixed by heating to 1300 ° C. or higher in a melting furnace. A melting step for volatilization removal, a off-gas discharged from the melting furnace is washed with smoke-washing water and a radioactive substance contained in the off-gas is separated from off-gas to smoke-washing water, and remaining in the off-gas A step for recovering the molten fly ash by the dust collecting unit, a step for transporting the recovered molten fly ash to the melting furnace for reprocessing, and a radioactive material for recovering radioactive material from the smoke-washed water The above-mentioned problem is solved by a radioactive substance processing method comprising a recovery step.

  In this treatment system and treatment method, the radioactive substance is volatilized and removed into the off-gas instead of washing the processing object such as molten fly ash and extracting the radioactive substance into water, so even a water-soluble radioactive substance is not water-soluble. Even radioactive materials can be separated and removed from the object to be treated. In addition, radioactive materials that are adsorbed by fine particles such as molten fly ash and are not easily dissolved in water can be separated and removed from the object to be treated. Moreover, the radioactive substance contained in offgas can be cooled and separated from offgas into smokewashing water by washing offgas containing the volatilized radioactive substance with smokewashing water. Further, the radioactive substance can be recovered from the smoke-washed water by adsorbing the radioactive substance on the adsorbent or coagulating and precipitating the radioactive substance. Also, in this treatment system and treatment method, handling and exposure measures for recovering molten fly ash from a dust collector such as a bag filter and washing it again with a separate device like the method of washing molten fly ash Is not necessary. In addition, even if the radioactive material concentration of the object to be treated is high and the radioactive material with a concentration exceeding the specified standard remains in the molten slag, the radioactive material is melted because the molten slag is a rocky or glassy pebbles. It is held in a stable state in the slag. Furthermore, the molten slag which is a pebble-like lump has a small surface area. Therefore, even if molten slag containing radioactive material is disposed of by storage or landfill, the radioactive material does not leak around the storage or landfill site or underground. Moreover, if it is a rocky or glassy pebbled molten slag, even if it contains a radioactive substance, the problem of scattering of the radioactive substance during conveyance does not arise. Moreover, the volume reduction effect is also acquired because a process target object turns into molten slag.

  The melting furnace used in the present processing system and processing method may be an emulsion burner type surface melting furnace. An emulsion burner type surface melting furnace does not generate molten fly ash, or even if molten fly ash is generated, the amount of molten fly ash generated is extremely small. Therefore, the radioactive substance contained in the object to be treated can be efficiently volatilized and removed in the off-gas as a gas, not in the form adsorbed by the molten fly ash. Even if non-radioactive contaminants such as PCB, dioxin, and asbestos are mixed in addition to radioactive substances in the object to be treated, an emulsion burner type surface melting furnace is harmless to these non-radioactive contaminants. It is also suitable for conversion.

  The present processing system may be configured to circulate the smoke-washed water so that the smoke-washed water treated in the radioactive substance recovery unit is reused in the smoke-washing unit. As described above, the smoke washing water circulates and is repeatedly used in the smoke washing unit, thereby realizing a treatment system that does not discharge the smoke washing water to the outside as a whole.

  The treatment system may further include a heat exchange unit for cooling off-gas between the melting furnace and the smoke washing unit, and the smoke washing unit may be installed adjacent to the heat exchange unit. When the off-gas is cooled in the heat exchange unit, some of the radioactive material in the off-gas may solidify and adhere to the piping between the heat exchange unit and the smoke washing unit, but may not reach the smoke washing unit. If the smoke unit is installed adjacent to the heat exchange unit, the radioactive material in the off-gas can be reliably sent to the smoke cleaning unit.

  Even when molten fly ash is generated from the melting furnace, the molten fly ash is transported to the melting furnace and reprocessed, and as a whole, the processing system (or processing method) does not discharge molten fly ash mixed with radioactive substances to the outside. Can be realized.

  In addition, the present processing system (or processing method) includes a dross recovery unit (or dross recovery step) for recovering dross in smoke-washed water, and dross recovered in the dross recovery unit (or dross recovery step). A dross reprocessing transport unit (or a dross reprocessing transport step) for transporting to the melting furnace for reprocessing may be further provided.

  Even if dross containing radioactive material is mixed in the smoke-washed water, the dross containing radioactive material is not discharged to the outside as a whole by transporting the dross to the melting furnace and reprocessing it (or processing method) Can be realized.

  The treatment system may further include a pH adjustment unit for adjusting the pH of the smoke-washed water. Adsorbents that have the property of adsorbing radioactive substances have a high ability to adsorb radioactive substances when the smoke-washing water is nearly neutral, and adsorb radioactive substances when the smoke-washing water exhibits strong acidity or alkalinity. Tend to be low. For example, when the object to be treated contains potassium, sodium, or calcium, the smoke-washed water may show strong alkalinity. Even in such a case, the adsorbent can efficiently adsorb the radioactive substance by adjusting the pH of the smoke-washed water (for example, a value close to 7).

The present processing system (or processing method) further includes a volatilization accelerator addition unit (or a volatilization accelerator addition step) for adding a volatilization accelerator to the object to be processed, and the volatilization accelerators are CaCl ₂ , FeCl _3. , CaCO ₃ , CaI ₂ , B ₂ O ₃ and Na ₂ B ₄ O ₇ may be included. CaCl ₂ , FeCl ₃ , CaCO ₃ , and CaI ₂ are highly effective in promoting volatilization of radioactive materials including ¹³⁴ Cs and ¹³⁷ Cs. B ₂ O ₃ and Na ₂ B ₄ O ₇ have the effect of lowering the melting point of the object to be treated and the effect of improving the fluidity of the molten slag.

  ADVANTAGE OF THE INVENTION According to this invention, the processing system and processing method of a radioactive substance with easy handling which can process the processing target object with which the radioactive substance which is hard to melt | dissolve in water, and the high concentration of a radioactive substance can be processed are realizable.

The side view which shows typically schematic structure of the processing system of the radioactive substance which concerns on 1st Embodiment of this invention Flow chart showing the outline of the radioactive material processing method by the processing system The side view which shows typically schematic structure of the radioactive substance recovery unit which concerns on 2nd Embodiment of this invention

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the radioactive substance processing system 10 according to the first embodiment of the present invention is a processing object 12 in which a radioactive substance containing at least one radionuclide of ¹³⁴ Cs, ¹³⁷ Cs, and ⁹⁰ Sr is mixed. A melting furnace 14 for volatilizing and removing radioactive substances in the off-gas while being heated to 1300 ° C. or higher, and a radioactive substance contained in the off-gas by washing the off-gas discharged from the melting furnace 14 with the smoking water 16 Is provided with a smoke washing unit 18 for separating the gas from the off-gas into the smoke washing water 16 and a radioactive substance recovery unit 20 for collecting the radioactive substance from the smoke washing water 16.

  The radioactive substance processing system 10 includes a dust collection unit 22 for collecting molten fly ash remaining in the off-gas washed by the smoke washing unit 18, and a reprocessing of the molten fly ash collected in the dust collection unit 22. Therefore, a molten fly ash reprocessing transport unit 24 for transporting to the melting furnace 14 is further provided.

  The radioactive material processing system 10 also has a dross recovery unit 26 for recovering the dross in the smoke-washed water, and for transporting the dross recovered in the dross recovery unit 26 to the melting furnace 14 for reprocessing. The dross reprocessing transport unit 28 is further provided.

  The radioactive substance treatment system 10 further includes a pH adjustment unit 30 for adjusting the pH of the smoke-washed water. The radioactive substance processing system 10 further includes a volatilization accelerator addition unit 32 for adding a volatilization accelerator to the object 12 to be processed.

The processing object 12 is, for example, incineration ash such as main ash and fly ash obtained by incineration of garbage at a waste incineration site, or molten fly ash obtained from a melting furnace (different from the melting furnace 14 of the first embodiment). The sludge obtained by sewage treatment, sludge incineration ash, soil, and the like. In the first embodiment, the processing object 12 is accommodated in a container such as a flexible container bag. The radioactive substance is, for example, a compound such as chloride, oxide or hydroxide of ¹³⁴ Cs, ¹³⁷ Cs, ⁹⁰ Sr. Specific examples of the radioactive substance include Cs, CsCl, CsOH, Cs ₂ CO ₃ , CsI, Sr, SrCl ₂ , Sr (OH) ₂ , SrO, SrI ₂ , SrCO _{3 and the} like. Table 1 shows melting points and boiling points of these radioactive substances. “Decomposition” in Table 1 means that the radioactive substance decomposes and changes to other compounds at a temperature higher than the melting point and lower than 1300 ° C.

  The melting furnace 14 is an emulsion burner type surface melting furnace, and a main burner 34 installed at the upper part of the combustion chamber radiates a flame toward the hearth 36 of the combustion chamber. The main burner 34 is supplied with emulsion fuel from a service tank 38. The service tank 38 mixes fuels such as heavy oil, light oil, kerosene, waste oil, alcohol, dimethyl ether and the like supplied from the fuel tank 40 with reducing water supplied from the reducing water generator 42 so as to generate emulsion fuel. It has become. The reduced water generator 42 generates reduced water by electrolyzing clean water. The reduced water generator 42 may be omitted, and the emulsion fuel may be generated by mixing clean water and fuel instead of the reduced water. As tap water, tap water, well water, reprocessed water, or the like can be used. An ignition burner 44 is installed in the vicinity of the main burner 34. The ignition burner 44 is supplied with gaseous fuel such as propane gas from a gas cylinder 46.

As described above, the heating temperature of the melting furnace 14 is 1300 ° C. or higher, and the heating temperature of the melting furnace 14 is more preferably 1350 ° C. or higher. If the heating temperature is 1300 ° C. or higher, radioactive materials containing ¹³⁴ Cs, ¹³⁷ Cs, and ⁹⁰ Sr can be volatilized and removed from the object to be treated, and asbestos can be made harmless by dissolving a asbestos. If the heating temperature of the melting furnace 14 is 1250 ° C. or higher, all SrCl ₂ can be volatilized instantaneously. If the heating temperature is 1277 ° C. or higher, all CsI can be volatilized instantaneously. If the heating temperature is 1295 ° C. or higher, all CsCl can be volatilized instantaneously. If the heating temperature is 1382 ° C. or higher, all Sr (metal) can be volatilized instantaneously. Therefore, the heating temperature of the melting furnace 14 is more preferably 1400 ° C. or higher. If the heating temperature is 1400 ° C. or higher, tea asbestos can be dissolved to make it harmless. If the heating temperature is 1450 ° C. or higher, the PCB can be decomposed with a margin. Further, if the heating temperature is 1500 ° C. or higher, asbestos can be made harmless by dissolving white asbestos, and metallic iron containing iron oxide can be dissolved. Further, if the heating temperature is 1773 ° C. or higher, all SrI ₂ can be volatilized instantaneously. The upper limit value of the heating temperature of the melting furnace 14 is, for example, 1800 ° C. or 2000 ° C. The upper limit of the heating temperature is preferably 1800 ° C. in terms of preventing breakage of castables constituting the furnace wall of the melting furnace 14.

Further, when the object to be treated is soil containing Cs, it is reported that when the object to be treated is heated to 1000 to 1200 ° C., CsAlSi ₂ O ₆ is generated and Cs is less likely to volatilize ( For example, refer to JAEA-Research-2011-026 “Examination of possibility of removing radioactive cesium by in-situ heating of soil”). It has also been reported that CsAlSi ₂ O ₆ is produced when a reagent-like Cs ₂ CO ₃ , Al ₂ O ₃ , and SiO ₂ are mixed and reacted in a high temperature environment of about 1000 ° C. Therefore, when the treatment object is incinerated ash or soil containing a large amount of SiO ₂ or Al, the melting furnace 14 melts the incinerated ash or soil at a heating temperature of 1400 to 1500 ° C., which greatly exceeds 1000 to 1200 ° C., and CsAlSi ₂ than the rate of formation of O ₆ containing Cs (except CsAlSi ₂ O ₆₎ as volatilization rate of the radioactive materials is increased it is necessary to promote the volatilization of radioactive material including Cs.

  The hearth part 36 is inclined, and the object 12 to be treated is pushed into the combustion chamber by being pushed by the pusher 48 from the upper entrance of the hearth part 36. The processing object 12 is conveyed by the conveyor 50 up to the entrance of the combustion chamber.

The volatilization accelerator addition unit 32 is provided on the upstream side of the melting furnace 14, and is configured to add the volatilization accelerator to the processing object 12 before being charged into the melting furnace 14. Examples of the volatilization promoter include chlorides such as CaCl ₂ and FeCl ₃ , CaCO ₃ and CaI ₂ , B ₂ O ₃ and Na ₂ B ₄ O having an effect of lowering the melting point and improving the fluidity of the molten slag. ₇ mag. In addition, the structure containing only any one of these components may be sufficient as a volatilization promoter, and the structure containing two or more components may be sufficient as it. The volatilization accelerator may be in the form of powder, tablet, or liquid (aqueous solution).

  In addition, a slag dropping port is formed on the lower side of the hearth part 36, and the processing object 12 (molten slag) heated and melted on the hearth part 36 passes through the slag conveyor 52. To fall. The slag conveyor 52 is connected to the granulated water tank 56 through pipes 54A and 54B, and water is circulated between the slag conveyor 52 and the granulated water tank 56. The molten slag is cooled with water in the slag conveyor 52 and solidified, and then is transported to the outside. The outer wall of the melting furnace 14 is connected to the cooling water tank 60 through the pipes 58A and 58B, and the outer wall of the melting furnace 14 is cooled by circulating water between them. ing.

  The smoke washing unit 18 includes an impeller-like member (not shown) inside, and the impeller-like member rotates to suck off gas from the melting furnace 14. The smoke washing unit 18 is connected to the smoke washing water tank 64 via the pipes 62A and 62B, and the smoke washing water 16 is circulated between the smoke washing unit 18 and the smoke washing water tank 64. The smoke washing unit 18 mixes off gas and the smoke washing water 16 and agitates them. As the smoke-washing water 16, the above-mentioned clean water can be used. The water granulated water tank 56, the cooling water tank 60, and the smoke washing water tank 64 are appropriately supplemented with clean water. The smoke cleaning unit 18 may be a scrubber.

  A heat exchange unit 66 for cooling off-gas is provided between the melting furnace 14 and the smoke washing unit 18. The smoke washing unit 18 is installed adjacent to the heat exchange unit 66. The heat exchange unit 66 and the smoke cleaning unit 18 may be directly connected via, for example, a heat insulating flange. Moreover, the heat exchange unit 66 and the smoke washing unit 18 may be connected via a bellows. The off-gas discharged from the melting furnace 14 is supplied to the smoke washing unit 18 after being reduced in temperature to about 400 to 800 ° C. in the heat exchange unit 66. The heat exchange unit 66 is configured to cool off-gas with air, and the air heated as the off-gas is cooled is supplied to the main burner 34 of the melting furnace 14 as combustion air. In addition, since the temperature of the off-gas cleaned in the smoke cleaning unit 18 is lowered to about room temperature, there is a possibility that condensation occurs in the dust collecting unit 22. In the heat exchange unit 66, the air heated as the off-gas is cooled is also supplied to the inlet side of the dust collection unit 22 in order to prevent condensation in the dust collection unit 22.

  The pH adjustment unit 30 adjusts the pH of the smoke-washed water 16 to a value close to 7 in the range of 6.7 to 7, for example, by introducing a neutralizing agent into the smoke-washed water tank 64. As the neutralizing agent, when the smoke-washed water 16 is acidic, for example, water-soluble caustic soda can be used. Further, when the smoke-washing water 16 is alkaline, for example, hydrochloric acid or the like can be used. In addition, when the smoke cleaning unit is a scrubber that supplies smoke contact water by spraying or spraying and absorbs and collects it, it is possible to mix a neutralizing agent in advance in the smoke wash water.

  The off gas cleaned in the smoke cleaning unit 18 is discharged from the smoke cleaning unit 18 to the outside through the draining unit 68, the dust collecting unit 22, and the chimney 72. The draining unit 68 is configured to separate the smoke washing water 16 mixed in the off gas from the off gas by centrifugation. The pipe 62B is also connected to a draining unit 68, and the smoke-washed water 16 separated from the off-gas in the drainer unit 68 is collected in the smoke-washing water tank 64 via the pipe 62B.

  The dust collection unit 22 is a bag filter. The off gas is heated to 100 ° C. or higher by the heated air supplied from the heat exchange unit 66 on the entrance side of the dust collection unit 22, so that condensation in the dust collection unit 22 is prevented. It has become. In addition, powder or liquid (for example, slaked lime or an aqueous solution thereof) is sprayed in the form of a mist on the inlet side of the dust collection unit 22 (not shown). Fine dust in the off-gas is adsorbed by these powders and liquids and captured by the dust collection unit 22. In addition, reduced water or clean water generated by the reduced water generator 42 is sprayed on the outlet side of the dust collection unit 22 in the form of a mist.

  Note that, for example, if the dust collection capability of the dust collection unit 22 alone does not provide a sufficient dust collection effect because of the high concentration of the radioactive substance contained in the processing object 12, the dust collection unit 22 and the chimney 72. A HEPA filter may be further installed between the two. The HEPA filter is an apparatus configured to separate fine dust that has passed through the dust collection unit 22 from off-gas using an adsorption effect of filter paper.

  The molten fly ash reprocessing transport unit 24 includes a conveyor, and directly melts the dust 14 such as molten fly ash filtered in the dust collection unit 22 in a container such as a flexible container bag. Or indirectly through the conveyor 50 to the melting furnace 14.

The radioactive substance recovery unit 20 includes a pump 74, a primary filter 76, a secondary filter 78, a cesium adsorption tower 80, and an activated carbon adsorption tower 82. The primary filter 76, the secondary filter 78, the cesium adsorption tower 80, and the activated carbon adsorption tower 82 are provided two each, and are arranged in parallel. The pump 74 sucks the smoke washed water 16 from the smoke washed water tank 64 and supplies the sucked smoke washed water 16 to the cesium adsorption tower 80 and the activated carbon adsorption tower 82 through the primary filter 76 and the secondary filter 78. Yes. The cesium adsorption tower 80 has a structure in which an adsorbent such as iron ferrocyanide (also called bitumen or Prussian blue) or cobalt ferrocyanide having a property of adsorbing cesium is contained in a tank or a can-like container. When the smoke water 16 passes through the cesium adsorption tower 80, the radioactive material containing ¹³⁴ Cs and ¹³⁷ Cs in the smoke wash water 16 is adsorbed by the adsorbent in the cesium adsorption tower 80 and separated from the smoke wash water 16. It has become. In the cesium adsorption tower 80, cyanide is generated by adsorbing a radioactive substance containing ¹³⁴ Cs or ¹³⁷ Cs by iron ferrocyanide or cobalt ferrocyanide. The cesium adsorption tower 80 can be exchanged. For example, the cesium adsorption tower 80 is exchanged every time a predetermined time elapses or every time a predetermined amount of radioactive material is adsorbed. The activated carbon adsorption tower 82 has a structure in which activated carbon is accommodated as an adsorbent in a container similar to the container of the cesium adsorption tower 80, and when the smoke washing water 16 passes through the activated carbon adsorption tower 82, Radioactive substances other than cesium (radioactive substances not adsorbed by the adsorbent in the cesium adsorption tower 80) and non-radioactive impurities are adsorbed by the activated carbon in the activated carbon adsorption tower 82 and separated from the smoke-washed water 16. ing. The activated carbon adsorption tower 82 can also be exchanged. For example, the activated carbon adsorption tower 82 is exchanged every time a predetermined time elapses or every time a predetermined amount of cyanide, radioactive substance, or the like is adsorbed. The smoke-washed water 16 that has passed through the activated carbon adsorption tower 78 is stored in a reclaimed water storage tank 84. The smoke-washed water 16 that has passed through the activated carbon adsorption tower 78 is supplied to the smoke-washed water tank 64 as reused water and reused. That is, the radioactive substance processing system 10 is configured such that the smoke cleaning water 16 circulates so that the smoke cleaning water 16 processed in the radioactive substance recovery unit 20 is reused in the smoke cleaning unit 18.

  The dross recovery unit 26 collects the dross at the bottom of the smoke-washing water tank 64 by sucking it from the upper part of the smoke-washing water tank 64 with a vacuum pump (not shown). The smoke washing water tank 64 may have a thickener structure in which dross is precipitated by a flocculant and collected. Moreover, you may have the thickener structure which isolate | separates dross from the smoke-washing water 16 by gravity sedimentation or centrifugation. That is, the smoke-washing water tank 64 may constitute a dross recovery unit. The recovered dross is dried by sunlight or a heating device (not shown). In addition, the dross may be dried using air heated by the off-gas cooling in the heat exchange unit 66. The dross reprocessing transport unit 28 is configured to have a conveyor similar to the molten fly ash reprocessing transport unit 24, and the dross recovered by the dross recovery unit 26 is accommodated in a container such as a flexible container bag. Thus, it is conveyed directly to the melting furnace 14 or indirectly via the conveyor 50 to the melting furnace 14.

  Next, the radioactive substance processing method by the radioactive substance processing system 10 will be described with reference to the flowchart of FIG. First, a volatilization accelerator is added to the processing object 12 (S102: volatilization accelerator addition step). Specifically, the volatilization promoter addition unit 32 adds the above-described volatilization promoter to the processing object 12 before being charged into the melting furnace 14 at a predetermined ratio with respect to the amount of the processing object 12.

Next, the radioactive material is volatilized and removed in the off-gas while the object 12 to which the volatilization accelerator is added is heated to 1300 ° C. or higher in the melting furnace 14 and melted (S104: melting step). As a result, most of the radioactive material containing ¹³⁴ Cs, ¹³⁷ Cs, and ⁹⁰ Sr mixed in the processing object 12 is volatilized and moves into the off-gas. At this time, volatilization of a radioactive substance including ¹³⁴ Cs and ¹³⁷ Cs is promoted by a volatilization accelerator such as CaCl ₂ , FeCl ₃ , CaCO ₃ , and CaI ₂ . Further, if the _{B 2 O 3, Na 2 B} 4 O 7 is added it is effective for improving the fluidity of the effect and molten slag to lower the melting point are obtained. Rather than washing the processing object such as molten fly ash and extracting the radioactive substance into water, the radioactive substance is volatilized and removed into the off-gas, so that both the water-soluble radioactive substance and the water-insoluble radioactive substance 12 Can be separated and removed. Further, even when there is a radioactive substance adsorbed by fine particles such as molten fly ash and hardly dissolved in water, such a radioactive substance can be separated and removed from the object to be treated. Further, since the melting furnace 14 is an emulsion burner type surface melting furnace, the amount of molten fly ash generated is extremely small even if molten fly ash is not generated or molten fly ash is generated. Therefore, the radioactive substance contained in the processing object 12 can be efficiently volatilized and removed in the off-gas as a gas, not in the form adsorbed by the molten fly ash. The processing object 12 (molten slag) heated and melted in the melting furnace 14 falls to the slag conveyor 52 through the slag dropping port. Since the radioactive substance is volatilized and removed, the molten slag does not contain a radioactive substance, or even if it contains a radioactive substance, it is a trace amount. Moreover, the volume reduction effect is also acquired because the process target object 12 turns into molten slag. In addition, if the amount of radioactivity of molten slag is, for example, 3.000 Bq / kg or less, it can be used as a construction or civil engineering material (for example, a concrete aggregate, a roadbed material, a backfill material such as a dike). It is done. For example, when the processing object is incineration ash, a volume reduction effect of 1/100 or less can be obtained by using molten slag as construction and civil engineering materials. On the other hand, when the concentration of the radioactive substance contained in the processing object 12 before being melted by heating is extremely high, the radioactive substance having a concentration exceeding a predetermined standard may remain in the molten slag. Even in such a case, the molten slag is a rocky or glassy pebble-like lump, so that the radioactive material is stably held in the molten slag, and the pebble-like lump molten slag has a small surface area. Therefore, even if molten slag containing radioactive material is disposed of by storage or landfill, the radioactive material does not leak around the site or underground. In addition, if the amount of radioactivity of molten slag is, for example, 100.000 Bq / kg or less, it is considered possible to embed it in a general waste final disposal site. Further, if the molten slag is a rocky or glassy pebble-like lump, even if it contains a radioactive substance, the problem of scattering of the radioactive substance during transportation does not occur.

  Next, the off-gas discharged from the melting furnace 14 is washed with the smoke-washing water 16 to separate radioactive substances contained in the off-gas from the off-gas into the smoke-washing water 16 (S106: smoke washing step). Specifically, the off-gas is discharged from the melting furnace 14 while being sucked into the smoke washing unit 18 and is reduced in temperature to, for example, about 400 to 800 ° C. in the heat exchange unit 66 before being supplied to the smoke washing unit 18. In 18, it is mixed with the smoke-washing water 16 and stirred. When the off-gas is cooled in the heat exchange unit 66, a part of the radioactive substance in the off-gas may solidify and adhere to the pipe between the heat exchange unit 66 and the smoke washing unit 18 and may not reach the smoke washing unit. However, since the smoke cleaning unit 18 is installed adjacent to the heat exchange unit 66, the radioactive substance in the off-gas is reliably sent to the smoke cleaning unit 18. The off-gas containing the volatilized radioactive material is agitated with the smoke-washing water 16, whereby the radioactive material contained in the off-gas is cooled and solidified by the smoke-washing water 16 and separated from the off-gas into the smoke-washing water 16. When fine particles such as molten fly ash and dust are mixed in the off gas, such fine particles are also separated from the off gas into the smoke washing water 16. The smoke washing water 16 to which the radioactive substance has been transferred is sent from the smoke washing unit 18 to the smoke washing water tank 64. The off gas is washed in the smoke washing unit 18 and then discharged to the outside through the draining unit 68, the dust collecting unit 22, and the chimney 72. Note that powder such as slaked lime or liquid such as water in which slaked lime is dissolved is sprayed on the off gas in the pipe in the form of a mist on the inlet side of the dust collection unit 22. Further, on the outlet side of the dust collection unit 22, the reduced water or clean water generated by the reduced water generator 42 is sprayed on the off gas in the pipe in a mist form. The smoke-washed water 16 separated from the off-gas by the draining unit 68 is collected in the smoke-wash water tank 64. Even when dust such as molten fly ash remains in the off-gas washed in the smoke-washed water 16, such dust is adsorbed by the powder sprayed on the inlet side of the dust collection unit 22 and becomes powder. It is removed from the off-gas in the dust collection unit 22 together with the body and the like. Even if fine dust that passes through the dust collection unit 22 is mixed, if a HEPA filter is installed between the dust collection unit 22 and the chimney 72, such fine dust will be removed from the HEPA. It is removed from the offgas in the filter.

Next, the radioactive substance is recovered from the smoke-washed water 16 by the adsorbent having the property of adsorbing the radioactive substance (S108: radioactive substance recovery step). Specifically, the smoke-washed water 16 stored in the smoke-washing water tank 64 is sucked by the pump 74 of the radioactive substance recovery unit 20 and supplied to the cesium adsorption tower 80 through the primary filter 76 and the secondary filter 78. . The radioactive material containing ¹³⁴ Cs and ¹³⁷ Cs transferred to the smoke washing water 16 is adsorbed by an adsorbent such as ferrocyanide and cobalt ferrocyanide in the cesium adsorption tower 80 and separated from the smoke washing water 16. Note that cyanide is generated by adsorbing a radioactive substance containing ¹³⁴ Cs or ¹³⁷ Cs by iron ferrocyanide or cobalt ferrocyanide. The smoke washing water 16 from which the radioactive material containing ¹³⁴ Cs and ¹³⁷ Cs has been separated and removed in the cesium adsorption tower 80 is then supplied to the activated carbon adsorption tower 82. Radioactive substances other than cyan and cesium or non-radioactive impurities contained in the smoke-washed water 16 are adsorbed by the activated carbon in the activated carbon adsorption tower 70 and separated and removed from the smoke-washed water 16. The smoke water 16 from which cyan, radioactive contaminants, and non-radioactive impurities are separated and removed in this manner is sent to the reclaimed water storage tank 84 and then supplied to the smoke water tank 64 and the like as reused water for reuse. . The cesium adsorption tower 80 is replaced every time a predetermined time elapses or every time a predetermined amount of radioactive material is adsorbed. The activated carbon adsorption tower 82 is also replaced every time a predetermined time elapses or every time a predetermined amount of radioactive material is adsorbed.

  In addition, the pH of the smoke-washed water 16 is appropriately adjusted (for example, constantly or periodically) by the pH adjustment unit 30 (for example, a value close to 7 in the range of 6.7 to 7). By adjusting the pH of the smoke-washing water 16 in this manner, the ability of the cesium adsorption tower 80 to adsorb the radioactive substance, such as ferrous ferrocyanide and iron ferrocyanide, can be improved, so that the radioactive substance can be efficiently recovered. be able to.

  By the way, molten fly ash may remain in the off-gas washed by the smoke washing unit 18 as described above. In such a case, the molten fly ash is separated and collected from the off-gas in the dust collecting unit 22. (S202: Molten fly ash recovery step). The molten fly ash collected in the dust collecting unit 22 is transferred to the melting furnace 14 by the molten fly ash reprocessing transport unit 24 for reprocessing (S204: transport step for molten fly ash reprocessing). Even when molten fly ash remains in the off-gas washed by the smoke washing unit 18, the molten fly ash is transported to the melting furnace 14 and reprocessed in this manner, so that it contains radioactive substances as a whole. A processing system and a processing method that do not discharge molten fly ash to the outside are realized.

  In addition, dross containing radioactive material may be mixed in the smoke-washed water 16. In this case, the dross is recovered from the smoke-washed water 16 by the dross recovery unit 26 (S302: Dross recovery step). The dross recovered in the dross recovery unit 26 is transported to the melting furnace 14 by the dross reprocessing transport unit 28 for reprocessing (S304: transporting step for dross reprocessing). By carrying the dross to the melting furnace 14 and reprocessing in this way, a treatment system and a treatment method that do not discharge dross containing radioactive materials to the outside are realized as a whole.

  Next, a second embodiment of the present invention will be described. The radioactive substance recovery unit 20 according to the first embodiment includes a cesium adsorption tower 80 and the like, and is configured to adsorb the radioactive substance to the adsorbent and collect it from the smoke-washed water 16, whereas this second In the embodiment, as shown in FIG. 3, the radioactive substance recovery unit 90 is configured to recover the particulate radioactive substance from the smoke-washed water 16 by coagulating and precipitating the particulate radioactive substance. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  The radioactive substance recovery unit 90 includes a first thickener 92 and a second thickener 94, which are connected in series. The smoke-washed water 16 in the smoke-washing water tank 64 is first sent to the first thickener 92.

The first medicine is introduced into the first thickener 92. The first drug is, for example, a mixture of K ₄ [Fe (CN) ₆ ] (ferrocyan compound) and a flocculant. The flocculant is, for example, a non-ion mainly composed of polyacrylamide or an anionic mixed flocculant. The smoke-washed water 16 treated by the first thickener 92 is sent to the second thickener 94.

The second medicine is introduced into the second thickener 94. The second drug is, for example, a mixture of UDD (highly dispersed carbon material) and K ₄ [Fe (CN) ₆ ] (ferrocyan compound). The second drug may be a mixture of UDD (highly dispersed carbon material), K ₄ [Fe (CN) ₆ ] (ferrocyan compound), and the above flocculant.

  The smoke-washed water 16 processed in the second thickener 94 is sent to the reclaimed water storage tank 84 and then supplied to the smoke-wash tank 64 and the like as reused water for reuse. In addition, the aggregated sediment containing radioactive material separated from the smoke-washed water 16 in the first thickener 92 and the second thickener 94 is dehydrated by a dehydrator (not shown) and then dried by a heat dryer (not shown). After that, it is sealed in a predetermined container and carried outside.

^When the concentration of the radioactive substance containing ⁹⁰ Sr is high, a phosphorous compound such as H ₂ PO ₄ , NaOH, KOH or the like is administered together with one or both of the first drug and the second drug, and the radioactive substance containing ⁹⁰ Sr It may be separated from the smoke-washed water 16 by coagulating sedimentation.

  In the first and second embodiments, the melting furnace 14 is an emulsion burner type surface melting furnace. However, the radioactive substance is volatilized in the off-gas while heating and melting the processing object 12 containing the radioactive substance. Other types of melting furnaces may be used as long as they can be removed. For example, an electric melting furnace such as an induction heating furnace, a resistance heating furnace, an arc heating furnace, a plasma heating furnace, or a burner type heating furnace may be used.

  In the first embodiment, the radioactive substance recovery unit 20 includes the cesium adsorption tower 80 having a structure in which an adsorbent having a property of adsorbing cesium is accommodated in a container and the activated carbon having a structure in which the activated carbon is accommodated in the container. Although it is a structure provided with the adsorption tower 82, if a radioactive substance can be collect | recovered from the smoke-washed water 16, the structure of a radioactive substance collection | recovery unit will not be specifically limited. For example, you may use the radioactive substance collection | recovery unit of a structure provided with 3 or more types of adsorption towers of the structure which accommodated the adsorbent of a respectively different kind in a container. Moreover, you may use the radioactive substance collection | recovery unit of a structure provided with only one kind of adsorption tower of the structure which accommodated the adsorbent of 2 types, or 3 or more types in the container.

  In the first embodiment, the cesium adsorption tower 80 and the activated carbon adsorption tower 82 are replaced every time a predetermined time elapses or every time a predetermined amount of radioactive material is adsorbed. However, only the adsorbent in the container may be replaced.

  In the first embodiment, iron ferrocyanide and cobalt ferrocyanide are exemplified as the cesium adsorbent, but other adsorbents such as zeolite are used as the adsorbent for cesium adsorption. Also good.

  In addition, the radioactive substance recovery unit 20 according to the first embodiment is configured to include a cesium adsorption tower 80 and the like, and the radioactive substance recovery unit 90 according to the second embodiment performs coagulation and precipitation of the radioactive substance. Although it is comprised so that it may collect | recover from the smoke-washing water 16, using the magnetic adsorbent of the structure which combined adsorbents, such as ferrocyanide iron, ferrocyanide cobalt, and zeolite, and magnetic powder, a radioactive substance recovery unit is For example, a magnetic adsorbent may be added to a water tank that stores the smoke-washed water 16, and the magnetic adsorbent that has adsorbed the radioactive substance may be collected by a magnetic force and separated from the smoke-washed water 16 and removed.

  In the first and second embodiments, the radioactive substance processing system 10 includes the molten fly ash reprocessing transport unit 24. For example, the amount of molten fly ash collected in the dust collection unit 22 is small. In such a case, the molten fly ash may be transported to the melting furnace 14 manually or by a semi-automatic transport device.

  In the first and second embodiments, the radioactive material processing system 10 includes the dross recovery unit 26 and the dross reprocessing transport unit 28. For example, the amount of dross recovered in the dross recovery unit 26 is as follows. In such a case, the dross may be transferred to the melting furnace 14 manually or by a semi-automatic transfer device. The dross may be collected manually or by a semi-automatic collection device. Further, for example, the smoke washing water 16 in the smoke washing water tank 64 is stirred and the dross at the bottom of the smoke washing water tank 64 is sent together with the smoke washing water 16 to the radioactive substance recovery unit 20 (90), and is contained in the dross or it. The radioactive substance may be recovered in the radioactive substance recovery unit 20 (90).

In the first and second embodiments, CaCl ₂ , FeCl ₃ , CaCO ₃ , CaI ₂ , B ₂ O ₃ , and Na ₂ B ₄ O ₇ are exemplified as volatilization promoters. Other volatilization promoters may be used as long as they have the effect of promoting the melting point, the effect of lowering the melting point, or the effect of improving the fluidity of the molten slag.

  In the first and second embodiments, the radioactive substance processing system 10 includes the volatilization accelerator addition unit 32. For example, before the radioactive substance processing system 10 is carried into the radioactive substance processing system 10, the radioactive substance is preliminarily attached to the processing object 12. When the volatilization accelerator is added or when the radioactive substance can be sufficiently volatilized and removed in the off-gas without using the volatilization accelerator, the radioactive substance processing system 10 does not include the volatilization accelerator addition unit 32. It may be configured.

  Moreover, in the said 1st and 2nd embodiment, although the process target 12 is carried in the melting furnace 14 in the state accommodated in containers, such as a flexible container bag, it is molten fly ash, sludge incineration ash. In the case where the processing object such as soil is automatically transported without human intervention, it may be carried into the melting furnace 14 without being stored in a container.

  Similarly, the molten fly ash and dross recovered in the dust collection unit 22 are also stored in the melting furnace 14 without being accommodated in a container when they are automatically transported to the melting furnace 14 without manual operation. It may come in. On the other hand, when the molten fly ash and dross recovered in the dust collection unit 22 are manually transported, they need to be transported in a state of being accommodated in a container.

[Experimental Example 1]
Simulated ash containing non-radioactive Cs was heated and melted in a test furnace to confirm the Cs removal effect. Specifically, three samples each containing two types of non-radioactive CsOH added as a chemical tracer to incinerated fly ash (about 20 g) and molten fly ash (about 20 g) in the Kansai area that do not contain radioactive cesium. Prepared. In addition, two types of samples were prepared, each of which was prepared by adding about 1000 ppm of non-radioactive CsCl as a chemical tracer to the same incinerated fly ash (about 20 g) and molten fly ash (about 20 g). CaCl ₂ , FeCl ₂ , and CaCO ₃ were added to the _three samples of the same type as volatilization promoters, respectively, and a total of 12 types of samples were prepared. Each of these 12 types of samples was heated in a commercially available test furnace (quartz tube atmospheric pressure furnace) at a temperature of about 1350 ° C. for about 1 hour, and the amount of Cs remaining in the resulting 12 types of molten slag was determined. The Cs removal effect was confirmed by analysis.

The Cs removal rate of 12 types of samples was 98.2 to 98.7%. That is, in any sample, the Cs removal rate was 98% or more (DF (decontamination coefficient) = 50 or more). In addition, the weight of incineration fly ash was reduced by 20 to 45%. Moreover, the weight of the molten fly ash was reduced by about 90%. This is presumably because volatile components such as Na, Ca and Cl contained in the incineration fly ash and the molten fly ash were volatilized at a high temperature. In this experiment, no difference was observed in the Cs removal rate between the sample added with CsOH as a chemical tracer and the sample added with CsCl. In this experiment, no difference was observed in the Cs removal rate between the sample added with CaCl ₂ as a volatilization accelerator, the sample added with FeCl _2, and the sample added with CaCO ₃ . On the other hand, the volatile promoter of the sample reduction rate in weight of the incineration fly ash was maximal (45%) was CaCl _2.

[Experiment 2]
Simulated ash containing non-radioactive Cs was heated and melted in a full-scale melting furnace to confirm the effect of Cs transfer to slag and smoke-washed water. Specifically, a sample was prepared by adding non-radioactive CsOH (about 500 g) as a chemical tracer to incineration ash (main ash: about 500 kg) not containing radioactive cesium. Separately from this sample, a sample was prepared by adding non-radioactive CsCl (about 500 g) to the same incinerated ash (main ash: about 500 kg) as this sample as a chemical tracer that also serves as a volatilization accelerator. Each of these two samples was heated in an emulsion burner type surface melting furnace (manufactured by Nippon Environmental Conservation Co., Ltd., NK-500) at a temperature of about 1500 ° C. for about 4 hours (intermittently 6 to 7 hours). The amount of Cs remaining in the two types of molten slag and the amount of Cs transferred to the smoke-washed water were analyzed by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer). The analysis results are shown in Table 2. The Cs concentration (mg / kg) of the incinerated ash in Table 2 is not the mass of CsCl or CsOH, but the ratio of the mass of Cs (relative to the mass of incinerated ash).

  As shown in Table 2, the amount (concentration) of Cs remaining in the molten slag was less than the measurement limit of 100 mg / kg for any sample. That is, it was confirmed that about 90% or more of Cs contained in the incinerated ash was volatilized and removed.

[Experiment 3]
Incinerated ash containing radioactive Cs was heated and melted in a test furnace to confirm the Cs removal effect. Specifically, five types of samples S1 to S5 of incineration ash (main ash, fly ash, main ash + fly ash) in the Kanto region containing ¹³⁴ Cs and ¹³⁷ Cs are heated at a temperature of about 1350 ° C. for about 1 hour, By analyzing the amount of ¹³⁴ Cs and ¹³⁷ Cs before and after heating, the removal effect of ¹³⁴ Cs and ¹³⁷ C was confirmed. Moreover, the weight reduction effect was confirmed by measuring the mass before and behind the heating of sample S1-S5. Samples S1 to S3 are incinerated ash collected in the same area. Samples S4 to S5 are incinerated ash collected in other same areas. The analysis results are shown in Table 3.

  S1 had a Cs volatility value close to 90%, and Samples S2 to S3 had a Cs volatility rate of 90% or more, which was good. On the other hand, in sample S4, the volatility of Cs was about 74%. This is probably because the area where the sample S4 was collected was different from the area where the samples S1 to S3 were collected, and the difference between the components of the sample S4 and the samples S1 to S3 was large. On the other hand, the volatility of Cs of sample S5 collected in the same area as sample S4 was 90% or more. This is probably because the volatilization accelerator CaI2 was added to the sample S5.

[Experimental Example 4]
Incinerated ash containing radioactive Cs was heated and melted in a full-scale melting furnace to confirm the Cs removal effect. Specifically, a sample L1 of incineration ash (main ash) in the same Kanto area as sample S4 of Experimental Example 3 containing ¹³⁴ Cs and ¹³⁷ Cs is heated at a temperature of about 1400 ° C. for about 3.5 hours, and before and after heating. It confirmed the effect of removing ^{134 Cs, 137} C by analyzing the amount of ^{134 Cs, 137} Cs. Moreover, the weight reduction effect was confirmed by measuring the mass before and behind the heating of the sample L1. The analysis results are shown in Table 4. The analysis result of the sample S4 of Experimental Example 3 is also described with reference. Note that the total radioactivity (Bq) of the sample L1 is a value obtained by converting the radioactivity concentration (Bq / kg). Samples S1 to S5 in Experimental Example 3 were previously dried and then measured for total radioactivity (Bq) and mass, and then heated and melted. Sample L1 in Experimental Example 4 was dried. Processing is not performed.

As shown in Table 4, it was confirmed that the removal effect of ¹³⁴ Cs and ¹³⁷ C similar to that of the test furnace can be obtained even in a full-scale melting furnace.

  The present invention can be used, for example, to separate and remove radioactive substances from incineration ash, sludge, and soil.

DESCRIPTION OF SYMBOLS 10 ... Radioactive substance processing system 12 ... Processing object 14 ... Melting furnace 16 ... Smoke washing water 18 ... Smoke washing unit 20, 90 ... Radioactive substance collection unit 22 ... Dust collection unit 24 ... Transport unit for molten fly ash reprocessing 26 ... Dross recovery unit 28 ... Dross reprocessing transport unit 30 ... pH adjustment unit 32 ... Volatilization accelerator addition unit S102 ... Volatilization accelerator addition step S104 ... Melting step S106 ... Smoke washing step S108 ... Radioactive substance recovery step S202 ... Melting flying Ash recovery step S204 ... transport step for molten fly ash reprocessing S302 ... dross recovery step S304 ... transport step for dross reprocessing

Claims (9)

A melting furnace for volatilizing and removing the radioactive substance in off-gas while heating and melting a processing object containing a radioactive substance containing at least one radionuclide of ¹³⁴ Cs, ¹³⁷ Cs, and ⁹⁰ Sr at 1300 ° C. or higher; ,
A smoke washing unit for washing off-gas discharged from the melting furnace with smoke-washing water and separating a radioactive substance contained in the off-gas from the off-gas into the smoke-washing water;
A dust collection unit for recovering molten fly ash remaining in the off-gas washed by the smoke washing unit;
A transport unit for molten fly ash reprocessing for transporting molten fly ash collected in the dust collection unit to the melting furnace for reprocessing;
And a radioactive substance recovery unit for recovering the radioactive substance from the smoke-washed water. In claim 1,
2. The radioactive material processing system according to claim 1, wherein the melting furnace is an emulsion burner type surface melting furnace. In claim 1 or 2,
The radioactive substance processing system, wherein the smoke cleaning water is circulated so that the smoke cleaning water processed in the radioactive substance recovery unit is reused in the smoke cleaning unit. In any one of Claims 1 thru | or 3,
A radioactive material further comprising a heat exchange unit for cooling the off-gas between the melting furnace and the smoke washing unit, wherein the smoke washing unit is installed adjacent to the heat exchange unit Processing system. In any one of Claims 1 thru | or 4 ,
A dross recovery unit for recovering the dross in the smoke-washed water, and a dross reprocessing transport unit for transporting the dross recovered in the dross recovery unit to the melting furnace for reprocessing. A radioactive material processing system, further comprising: In any one of Claims 1 thru | or 5 ,
The radioactive substance processing system further comprising a pH adjusting unit for adjusting the pH of the smoke washed water. In any one of Claims 1 thru | or 6 .
A volatilization accelerator addition unit for adding a volatilization accelerator to the object to be treated is further provided, and the volatilization accelerator includes CaCl ₂ , FeCl ₃ , CaCO ₃ , CaI ₂ , B ₂ O ₃ and Na ₂ B ₄ O _7. A radioactive material processing system comprising at least one component of: A process for mixing a radioactive material containing at least one radionuclide of ¹³⁴ Cs, ¹³⁷ Cs and ⁹⁰ Sr by heating to 1300 ° C. or higher in a melting furnace to melt and remove the radioactive material into off-gas. A melting step;
A smoke washing step for washing off-gas discharged from the melting furnace with smoke-washing water to separate a radioactive substance contained in the off-gas from the off-gas into the smoke-washing water;
A step for recovering molten fly ash remaining in the off-gas by a dust collection unit;
Transporting the recovered molten fly ash to the melting furnace for reprocessing;
And a radioactive substance recovery step for recovering the radioactive substance from the smoke-washed water. In claim 8,
A dross recovery step for recovering the dross in the smoke-washed water, and a dross reprocessing transport step for transporting the dross recovered in the dross recovery step to the melting furnace for reprocessing. A method for treating a radioactive substance, further comprising:

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