JP2017181029A - Removal method and removal device of radioactive cesium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a removal method of radioactive cesium, which can reduce the volume of waste containing the radioactive cesium, while the concentration of the radioactive cesium of a heating-derived product generated during the volume reduction of the radioactive cesium-containing waste is suppressed to low level.SOLUTION: A removal device of radioactive cesium includes: a mixing device 2 for mixing waste W contaminated by the radioactive cesium, a calcium oxide source and/or a magnesium oxide source, and a chlorine source; a heating furnace 8 for heating a mixture M from the mixing device; a cooling tower 11 for cooling an exhaust gas from the heating furnace; a classifier 12 for classifying dust contained in an exhaust gas G2 from the cooling tower into coarse powder C and fine powder; a measurement device 13 for measuring the concentration of the radioactive cesium of the coarse powder separated by the classifier; first conveyance routes 15A to 15E for returning the coarse powder to the heating furnace; second conveyance routes 15F, 15G for discharging the coarse powder outside the system; and a switching device 14 for switching conveyance routes of the coarse powder to either the first conveyance routes or the second conveyance routes on the basis of measurement result by the measurement device.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method and apparatus for removing radioactive cesium from waste containing radioactive cesium, and in particular, a method for reducing the volume of radioactive cesium-containing waste and reducing the concentration of radioactive cesium in a heated product. About.

  In order to remove the radioactive cesium taken into the soil, for example, in Patent Document 1, the soil contaminated with radioactive cesium is heated with a rotary kiln, the kiln exhaust gas is cooled to produce fine powder containing radioactive cesium, and the kiln exhaust gas is produced. The technology which collects the coarse powder inside, returns to a rotary kiln, and collects fine powder from kiln exhaust gas is described. By this technology, radioactive cesium is concentrated to a high concentration as a fine powder, volume reduction is achieved, the burden of intermediate storage or final disposal can be reduced, and a heated product with reduced radioactive cesium concentration can be obtained. it can.

JP 2013-19734 A

  In the above radioactive cesium removal technology, since the coarse powder is recovered after the kiln exhaust gas is cooled, solidified chloride adheres to the coarse powder, and the radioactive powder has a higher concentration than the soil contaminated with the radioactive cesium before treatment. Cesium will be included. And if this coarse powder is returned to a rotary kiln, radioactive cesium will circulate and concentrate, and there exists a possibility that the radioactive cesium density | concentration of a heating product may increase.

  In addition, since the coarse powder contains alkali at a high concentration, when the coarse powder is returned to the rotary kiln, the melting point of the raw material in the kiln decreases, the firing temperature tends to decrease, and the volatility of radioactive cesium decreases. As a result, the radioactive cesium concentration of the heated product increases.

  In order to avoid the above problem, if the coarse powder is recovered together with the fine powder without returning to the rotary kiln, the radioactive cesium concentration of the heated product can be reduced, but the radioactive material recovered from the kiln exhaust gas (fine powder and coarse powder) The concentration of cesium decreases, which is against the intention of reducing the volume of radioactive cesium-containing waste.

  Therefore, the present invention has been made in view of the above-mentioned problem, while maintaining the radioactive cesium concentration of the heated product generated at the time of volume reduction of the waste containing radioactive cesium at a low level, The purpose is to reduce the volume of radioactive cesium-containing waste.

  In order to achieve the above object, the present invention provides a method for removing radioactive cesium, comprising mixing a waste contaminated with radioactive cesium, a calcium oxide source and / or a magnesium oxide source, and a chlorine source. Is heated to volatilize radioactive cesium in the waste, cool the gas generated by heating the preparation, classify the dust contained in the cooled gas into coarse powder and fine powder, The radioactive cesium concentration of the powder is measured, and based on the measurement result, it is determined whether the coarse powder is heated again or discarded.

  According to the present invention, in order to determine the treatment method of the coarse powder according to the radioactive cesium concentration of the coarse powder obtained by classifying the cooled gas, circulating concentration of the radioactive cesium concentration is prevented, and the heating product The volume of radioactive cesium-containing waste can be reduced while maintaining the radioactive cesium concentration at a low level. Here, the discarding process means performing intermediate storage and final disposal.

  In the method for removing radioactive cesium, in heating the coarse powder again, the coarse powder is heated as it is with the preparation, or the coarse powder is washed with water and solid-liquid separated and then heated with the preparation, Either the calcium source is added to the coarse powder and granulated, and then heated together with the preparation, or the calcium source is added to the coarse powder and then heated separately from the preparation. By performing an appropriate treatment according to the radioactive cesium concentration of the coarse powder, the volume of the radioactive cesium-containing waste can be reduced, and a heating product having a low radioactive cesium concentration can be stably obtained.

  In heating the coarse powder again, when the radioactive cesium concentration of the coarse powder is 20 times or less of the radioactive cesium concentration of the waste, the coarse powder can be heated as it is with the preparation. Thereby, the radioactive cesium density | concentration of the heating product obtained can be restrained low.

  Furthermore, the present invention is an apparatus for removing radioactive cesium, which comprises a waste contaminated with radioactive cesium, a calcium oxide source and / or a magnesium oxide source, and a chlorine source, A heating furnace that heats the mixture, a cooling tower that cools the exhaust gas of the heating furnace, a classifier that classifies dust contained in the exhaust gas of the cooling tower into coarse powder and fine powder, and the classifier A measuring device for measuring the radioactive cesium concentration of the coarse powder, a first transport route for returning the coarse powder to the heating furnace, a second transport route for discharging the coarse powder out of the system, and a measurement result of the measuring device And a switching device for switching the coarse powder conveyance route to either the first conveyance route or the second conveyance route.

  According to the present invention, among the coarse powders classified by the classifier, in order to determine the treatment method of the coarse powder according to the radioactive cesium concentration of the coarse powder, the circulating concentration of the radioactive cesium concentration is prevented, and the heating product The volume of radioactive cesium-containing waste can be reduced while maintaining the radioactive cesium concentration at a low level.

  As described above, according to the present invention, it is possible to reduce the volume of radioactive cesium-containing waste while maintaining the radioactive cesium concentration of the heated product generated during volume reduction of the waste containing radioactive cesium at a low level. Can be achieved.

It is the schematic which shows one Embodiment of the removal apparatus of the radioactive cesium which concerns on this invention. It is the schematic for demonstrating operation | movement of the radioactive cesium removal apparatus which concerns on this invention. It is the schematic for demonstrating operation | movement of the radioactive cesium removal apparatus which concerns on this invention. It is the schematic for demonstrating operation | movement of the radioactive cesium removal apparatus which concerns on this invention. It is the schematic for demonstrating operation | movement of the radioactive cesium removal apparatus which concerns on this invention. It is the schematic for demonstrating operation | movement of the radioactive cesium removal apparatus which concerns on this invention. It is the schematic for demonstrating operation | movement of the radioactive cesium removal apparatus which concerns on this invention.

  Next, an embodiment for carrying out the present invention will be described in detail with reference to the drawings. In the following description, radioactive cesium refers to cesium 134 and cesium 137, which are radioactive isotopes of cesium.

  FIG. 1 shows an embodiment of a radioactive cesium removal apparatus according to the present invention, and this radioactive cesium removal apparatus 1 includes a blending device 2, a firing device 7, and an exhaust gas treatment device 10.

  The mixing device 2 includes a storage tank 3 for storing waste W such as soil contaminated with radioactive cesium and incinerated ash, and a storage tank 4 for storing a calcium oxide source (hereinafter referred to as “CaO source”) as a reaction accelerator. , A storage tank 5 for storing a chlorine source (hereinafter referred to as “Cl source”) as a reaction accelerator, and a quantitative feeder for extracting and preparing the waste W, CaO source and Cl source stored in the storage tanks 3 to 5 (Not shown) and a storage tank 6 for storing the preparation M.

As said CaO source, what contains limestone powder, calcium carbonate, quicklime, slaked lime, limestone, dolomite, blast furnace slag, etc. can be used. In addition, the Cl source is used to promote the volatilization and volatilization of radioactive cesium, and to reduce the volume of the volatile recovery, and calcium chloride (CaCl ₂ ), potassium chloride (KCl), sodium chloride (NaCl), and chlorine. Among them, there are waste plastics, etc. Among them, CaCl ₂ is preferable because it can effectively remove radioactive cesium.

  The calcining device 7 is composed of a rotary kiln (heating furnace) 8 and a clinker cooler 9. The rotary kiln 8 ejects fossil fuel such as a charging port 8 a to which the preparation M from the preparation device 2 is supplied and pulverized coal. A burner 8b and the like are provided, and the preparation M or the like is fired to obtain a fired product (heated product).

  The exhaust gas treatment device 10 is disposed at the rear stage of the firing device 7, and is recovered by the cooling tower 11 that cools the exhaust gas G <b> 1 discharged from the rotary kiln 8, the cyclone 12 that is disposed at the rear stage of the cooling tower 11, and the cyclone 12. Measuring device 13 for measuring the radioactive cesium concentration of coarse powder C, transport route 15 (15A-15G) for coarse powder C, and switching device 14 for switching the transport route 15 for coarse powder C based on the measurement results of the measurement device 13 The first dust collector 16, the second dust collector 17, the denitration device 18 for denitrating the exhaust gas G5 from which dust such as concentrated cesium salt has been removed by the two dust collectors 16, 17, and the exhaust gas G6 of the denitration device 18 outside the system. It is comprised with the chimney 19 to exhaust.

  The cooling tower 11 is provided for cooling the exhaust gas G1 of the rotary kiln 8 and recovering radioactive cesium and the like volatilized from the waste W as a solid. The exhaust gas G1 is cooled by spraying water from a sprinkler 11a installed at the lower end of the cooling tower 11. In addition, this watering apparatus 11a should just be equipped with the function of the grade which can be made to adhere to the dust contained in the waste gas G1 by volatilizing the cesium chloride volatilized. Instead of cooling with water, cooling may be performed by introducing cooling air into the cooling tower, or water and cooling air may be used in combination.

  The cyclone 12 as a classifier is provided for collecting fine powder containing a high concentration of radioactive cesium by the first dust collector 16 and collecting coarse powder C mainly composed of calcium and silica components.

  The measuring device 13 is, for example, a germanium semiconductor detector or a NaI scintillation detector, and calculates the radioactive concentration of the sample from the surface dose rate in the hopper, or the radioactive concentration measuring device installed so as to surround the hopper. Measure the coarse powder C radioactivity concentration. When measuring from the outside, it is necessary to confirm in advance the relationship (coefficient) between the surface dose rate and the radioactive concentration of the sample. Alternatively, the target sample is filled in a special container or made into a specified shape and then flowed on a conveyor, or after it has been made to a predetermined shape on the conveyor and flowed, and is placed so as to surround the conveyor (consisting of a NaI detector or the like) E) Continuously measure the radioactivity concentration of the sample by passing it through the radioactivity concentration measurement device. Of these, the hopper method is desirable from the viewpoint of preventing leakage of coarse powder to the outside. Since the coarse powder is cooled, the surface can be directly measured, or the detector can be arranged in the coarse powder filled in the hopper.

  As the conveyance route 15, the 1st-5th conveyance route 15A-15E which returns the coarse powder C to the rotary kiln 8, the 6th conveyance route 15F which discharges the coarse powder C out of the system of the radioactive cesium removal apparatus 1, and the 7th conveyance route There are seven 15G transport routes 15A to 15G. Although details will be described later, the first to fifth transport routes 15A to 15E return the coarse powder C directly or indirectly to the rotary kiln 8, or finally return to the rotary kiln 8 through the processing device.

  The sixth transport route 15F and the seventh transport route 15G are for discharging the coarse powder C to the outside of the system of the radioactive cesium removing apparatus 1, and the details will be described later. The seventh transport route 15G is a route for not discharging the coarse powder C directly outside the system but discharging it outside the system without going through the rotary kiln 8.

  The first dust collector 16 is provided to collect the dust D1 containing the cesium salt concentrated as described above from the exhaust gas G3 of the cyclone 12, and a bag filter or the like is used.

  The 2nd dust collector 17 is provided in order to remove the acidic gas etc. which are contained in exhaust gas G4 after removing a cesium salt etc., and neutralizer N which contains a calcium component is neutralizer addition device (not shown) The dust D2 adsorbed with acid gas and the like is recovered. A bag filter or the like is also used for the second dust collector 17.

The denitration device 18 is provided to inject ammonia gas (NH ₃ ) into the exhaust gas G5 of the second dust collector 17 to reduce NOx to nitrogen and render it harmless.

  Next, the operation of the radioactive cesium removal apparatus 1 having the above configuration will be described with reference to FIG.

In the blending device 2, the waste W contaminated with radioactive cesium, the CaO source and the Cl source as reaction accelerators are drawn from the storage tanks 3 to 5 and blended to obtain a blend M. The composition M is made of a earthwork material that does not produce C ₃ S (alite) when fired or a cement clinker composition containing C ₃ S.

When manufacturing the earthwork material, the waste W and the waste W so that the relationship between CaO, SiO ₂ and MgO in the preparation M satisfies (CaO + 1.39 × MgO) / SiO ₂ = 1.0 to 2.7. It is preferable to prepare the CaO source after determining its kind and blending ratio. In the formula, CaO, MgO, and SiO ₂ represent a mass in terms of calcium oxide, a mass in terms of oxide of magnesium, and a mass in terms of oxide of silicon, respectively. The value (mass ratio) on the right side of the above formula calculated by the mass of each of the above formulas CaO, MgO, and SiO ₂ is preferably 1.8 to 2.5, more preferably 1.9 to 2.4. is there. In the above relational expression, the mass of 1 mol of CaO corresponds to the mass of 1.39 mol of MgO, so the mass of MgO is multiplied by 1.39.

  When the mass ratio is less than 1.0, a liquid phase is likely to be generated as the firing temperature is increased, and the volatilization amount of radioactive cesium may be reduced. When the mass ratio exceeds 2.7, the total amount of volatilization of potassium and sodium in the waste W and the preparation M contaminated with radioactive cesium increases, and the alkali component in the coarse powder C increases. There is a possibility that the amount of dust obtained by cooling the exhaust gas G2 may increase.

On the other hand, when producing a cement clinker, the waste is set so that the relationship between CaO, SiO ₂ and MgO in the preparation M satisfies (CaO + 1.39 × MgO) / SiO ₂ = 2.7 to 3.7. It is preferable to blend W and CaO sources after determining their types and blending ratios.

  When the mass ratio is 2.7 or more, the preparation M is difficult to melt, so that more radioactive cesium can be volatilized. On the other hand, if the mass ratio exceeds 3.7, the free lime (free lime) contained in the cement clinker increases, so that the quality of the cement may be deteriorated. In order to prevent these more reliably, it is preferable that the mass ratio satisfies 2.8 to 3.5. Furthermore, the desired cement clinker is prepared by adjusting the silicic acid ratio (SM) of the preparation M to 1.3 to 3.0 and the iron ratio (IM) to 1.3 to 2.8. Can be manufactured.

  Moreover, it is preferable to mix | blend the quantity of the said Cl source so that it may become an equivalent or more with respect to the radioactive cesium contained in the waste W, even when manufacturing both earthwork materials and a cement clinker. The upper limit of the amount of the Cl source is such that the molar ratio Cl / (Cs + K) between chlorine, cesium and potassium is preferably 1.5 or less, more preferably 1.0 or less. When this molar ratio is 1.0 or less, radioactive cesium volatilizes while suppressing the volatilization amount of potassium and sodium, so that the volume of radioactive cesium-containing waste can be reduced.

  In addition, when manufacturing earthwork material, it is preferable to perform the said preparation and the following baking so that the calcium oxide density | concentration of earthwork material (baked material B) may be 50 mass% or more. Thereby, since sulfur content is hold | maintained in earthwork materials, or it collects as dust D1 of exhaust gas G3 as a sulfur compound in the 1st dust collector 16 mentioned later, the circulation of sulfur content can be suppressed and the load of exhaust gas treatment is reduced. Increase and increase in coaching can be reduced.

  The preparation M is charged from the storage tank 6 into the rotary kiln 8 through the charging port 8a and fired at 1200 ° C. or higher and 1550 ° C. or lower to obtain a fired product B. Here, the oxygen partial pressure in the rotary kiln 8 is 3% or more, preferably 5% or more. Thereby, since decomposition | disassembly of the sulfur compound in the rotary kiln 8 is suppressed and the circulation of sulfur content is suppressed, the increase in the usage-amount of a neutralizing agent and the increase in the coating amount of coating to the rotary kiln 8 and the cooling tower 11 are suppressed. be able to.

  On the other hand, the radioactive cesium contained in the waste W of the preparation M reacts with chlorine generated from the Cl source in the rotary kiln 8 to volatilize as cesium chloride and is contained in the exhaust gas G1 in the state where the cyclone 12 is contained. To be introduced.

  The exhaust gas G1 is rapidly cooled by the water sprayed from the sprinkler 11a in the cooling tower 11, and the cesium chloride contained in the exhaust gas G1 becomes a solid cesium salt. And although most cesium salts are collect | recovered as dust D1 with fine powder, a part adheres to coarse powder dust.

  The dust contained in the exhaust gas G2 of the cooling tower 11 is classified by the cyclone 12, and the coarse powder C obtained by classification is supplied to the measuring device 13. The measuring device 13 measures the radioactive cesium concentration of the coarse powder C.

  Here, when the radioactive cesium density | concentration of the coarse powder C measured by the measuring apparatus 13 is comparatively low, it switches to any of the 1st-5th conveyance routes 15A-15E with the switching apparatus 14, and the coarse powder C is turned into a rotary kiln. When the concentration is relatively high, the switching device 14 switches to either the sixth transport route 15F or the seventh transport route 15G and discharges the coarse powder C out of the system of the radioactive cesium removing device 1. .

  The radioactive cesium concentration that determines whether the coarse powder C is returned to the rotary kiln 8 or discharged out of the system is 200,000 Bq / kg or less, which is a compatible concentration when only earthwork materials are manufactured. In the case of manufacturing aggregate and cement, or only cement, the concentration should be 1 million Bq / kg or less, which can be handled by the cement composition. The reason why the numerical value of cement is high is that cement is more difficult to melt even at high temperatures due to the larger amount of Ca, and the volatilization rate of cesium by firing becomes higher. Therefore, the coarse powder C exceeding 200,000 Bq / kg and not more than 1,000,000 Bq / kg is adapted to be heated as the composition of the cement clinker, and the coarse powder C exceeding 1 million Bq / kg is discharged out of the system. .

  Next, switching of the transport route by the switching device 14 will be described in detail.

  When the radioactive cesium concentration of the coarse powder C measured by the measuring device 13 is 20 times or less, preferably 10 times or less that of the waste W, as shown in FIG. Switch to the conveyance route 15A and return the coarse powder C directly to the rotary kiln 8. The amount of the coarse powder is usually 2% of the input raw material by mass ratio and at most 5% in a short period, so if it is 20 times or less, the radioactive Cs of the fired product is not greatly affected. If it becomes more than that, the frequency with which the radioactive Cs density | concentration of a baked product will be 100 Bq / kg or more will become high.

  Further, as shown in FIG. 3, the coarse powder C is not directly returned to the rotary kiln 8, but the transfer route is switched to the second transfer route 15 </ b> B by the switching device 14, and the waste W is returned to the storage tank 3. Mixing with the stored CaO source or Cl source can also be performed.

  On the other hand, when the radioactive cesium concentration of the coarse powder C measured by the measuring device 13 is 40 times or less, preferably 20 times or less that of the waste W, as shown in FIG. Switching to the third transport route 15 </ b> C, the coarse powder C is washed with water by the water washing device 21, the slurry S from the water washing device 21 is dehydrated by the solid-liquid separator 22, and the obtained dewatered cake DC is returned to the rotary kiln 8. Thereby, a part of radioactive cesium and alkali contained in the coarse powder C are removed, and an increase in the radioactive cesium concentration of the fired product B can be prevented. The dewatered cake DC may be returned to the storage tank 6, and in this case, the storage tank 6 needs to be provided with a drying means.

  It is preferable to use a filter press as the solid-liquid separator 22 because the dehydrated cake DC becomes a lump and a granulated product can be obtained simply by crushing it. Separately, a granulator such as a pug mill, a dish-type pelletizer, a drum granulator, or an extrusion molding machine may be used. The particle size of the granulated product is preferably 10 to 100 mm. The specific surface area is reduced by granulation to prevent the granulated material from melting and promote volatilization of radioactive cesium contained in the granulated material. Moreover, since the dust generation in the rotary kiln 8 is reduced, the amount of generated radioactive cesium-containing waste is also reduced. Here, if the particle size is larger than 100 mm, the granulator becomes excessive and the apparatus and the operating cost increase. On the other hand, if the particle size is less than 10 mm, the specific surface area increases and the effect of granulation is reduced, which is not preferable. .

  In addition, it is not necessary to perform the solid-liquid separation in the solid-liquid separator 22 strictly. For example, a part of the filtrate F is mixed in the dehydrated cake DC and is in a slurry state, such as centrifugal separation or sedimentation separation. It may be. Conversely, the filtrate F may contain some coarse powder.

  On the other hand, the filtrate F from the solid-liquid separator 22 is sprayed by the cooling tower 11 via the water sprinkler 11a, thereby evaporating the moisture of the filtrate F, and the first dust collector 16 to be described later with solid radioactive cesium. To collect as dust D1.

  The filtrate F may be added to the exhaust gas G3 of the cyclone 12. When the filtrate F is supplied to the cooling tower 11, radioactive cesium contained in the filtrate F may adhere to the coarse powder C side of the cyclone 12 and circulate, but by adding it to the exhaust gas G3, the radioactive cesium is circulated. Can be reliably prevented. In this case, it is not always necessary to cool the radioactive cesium to a solid temperature in the cooling tower 11, and the first dust collector 16 may cool the radioactive cesium to a solid temperature. As a result, the radioactive cesium concentration of the coarse powder C1 becomes low, and more radioactive cesium can be concentrated in the dust D1.

  Furthermore, when the radioactive cesium concentration of the coarse powder C measured by the measuring device 13 is 100 times or less, preferably 50 times or less that of the waste W, as shown in FIG. It switches to the 4th conveyance route 15D, and after adding CaO source to the coarse powder C, the coarse powder C is granulated by the granulator 23, and the obtained granulated product GR can be returned to the rotary kiln 8. By this granulation, the specific surface area can be reduced to prevent the granulated product GR from melting, and the volatilization of radioactive cesium contained in the granulated product GR can be promoted.

The amount of CaO source, and C ₃ S (alite) is produced composition when fired. By using a cement clinker containing C ₃ S, it is possible to produce a cement having the same quality as commercially available Portland cement. Here, the relationship between CaO, SiO ₂ and MgO in the granulated product GR satisfies (CaO + 1.39 × MgO) / SiO ₂ = 2.7 to 3.7, more preferably 2.8 to 3.5. Thus, it is preferable to add a CaO source.

When the value (mass ratio) on the right side of the above formula calculated by the mass of each of CaO, MgO, and SiO ₂ is 2.7 or more, the granulated product GR is difficult to melt, so that the radioactive cesium is more Volatilizes a lot. On the other hand, when the mass ratio exceeds 3.7, free lime (free lime) contained in the obtained cement clinker CL increases, so that the quality of the obtained cement may be deteriorated. In the electric furnace test, when the value of the above formula is 2.96, the Cs removal rate is 99.995%, but in the case of 2.0, it is 99.955%. Moreover, the desired cement is obtained by adjusting the silicic acid ratio (SM) of the granulated product GR to 1.3 to 3.0 and the iron ratio (IM) to 1.3 to 2.8. Clinker CL is manufactured.

Further, calcium chloride (CaCl ₂ ) may be added as a Cl source for the purpose of promoting the volatilization of radioactive cesium by chlorination and reducing the volume of the volatile recovery product. The upper limit of the amount of the Cl source is such an amount that the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is preferably 1.0 or less, more preferably 0.5 or less. When the molar ratio is 1.0 or less, a large amount of radioactive cesium is volatilized while suppressing the volatilization amount of potassium, sodium, and the like, so that the volume of radioactive material-containing waste can be reduced.

  Examples of the granulator 23 include a pug mill, a dish type pelletizer, a drum type granulator, and an extrusion molding machine. The particle size of the granulated product GR is preferably 10 to 100 mm. Here, when the particle size is larger than 100 mm, the granulator 23 is excessively increased and the apparatus and the operating cost are increased. On the other hand, when the particle size is less than 10 mm, the specific surface area is increased and the effect of granulation is reduced. Absent. In addition, you may granulate the coarse powder C1 after Ca source addition after the water washing and solid-liquid separation which were shown in FIG.

  Further, when the radioactive cesium concentration of the coarse powder C measured by the measuring device 13 is 200 times or less, preferably 100 times or less that of the waste W, as shown in FIG. It switches to the 5th conveyance route 15E, a CaO source is added to the coarse powder C, it stores temporarily in the storage tank 24, the coarse powder C1 from the storage tank 24 is returned to the rotary kiln 8, and is baked separately from the preparation M.

  In order to bake the coarse powder C1 separately from the preparation M, the coarse powder C1 is stored, and the baking dates of the coarse powder C1 and the preparation M are shifted, or the baking timing is shifted. Since the coarse powder C1 is baked alone, it does not affect the baking of the mixed raw material M (volatilization of radioactive cesium). Since the firing is carried out independently, the firing product B having a low radioactive C cesium concentration can be obtained by adjusting the firing time and the firing amount even if the radiation concentration of the coarse powder C1 is high. In addition, the addition method of CaO source and the composition adjustment method are the same as the case where the granulator 23 of FIG. 5 is installed. Can be obtained.

  On the other hand, when the radioactive cesium concentration of the coarse powder C measured by the measurement device 13 exceeds 200 times the waste W, the transfer route is switched to the sixth transfer route 15F by the switching device 14 as shown in FIG. The dust D1 of the first dust collector 16 can be merged and directly discharged out of the system of the radioactive cesium removing apparatus 1. Alternatively, the coarse powder C may not be directly discharged out of the system of the radioactive cesium removing device 1, and the transfer route may be switched to the seventh transfer route 15 </ b> G by the switching device 14 and merged with the exhaust gas G <b> 3 of the cyclone 12.

  This is the end of the description of the switching of the transport routes (15A to 15G) by the switching device 14, and the subsequent processing of the cyclone 12 will be described.

  The dust contained in the exhaust gas G3 of the cyclone 12 in FIG. 1 is recovered as dust D1 by the first dust collector 16. The recovered dust D1 can be stored in a sealed container such as concrete after being further reduced in volume by compression, washing, adsorption, etc. as necessary. Waste containing radioactive cesium can be stored outside. The volume can be reduced and stored without leakage. Moreover, it can be buried in the ground as a final disposal.

  The exhaust gas G4 after recovering the concentrated cesium salt contains a harmful gas such as an acid gas. Therefore, after adding the neutralizing agent N to the exhaust gas G4 from the neutralizer addition device, the exhaust gas G4 is exhausted by the second dust collector 17. Dust D2 adsorbing acid gas or the like is recovered from G4. Here, as the neutralizing agent N, one containing at least one selected from the group consisting of slaked lime, quicklime, dolomite, light-burned dolomite and hydroxylated dolomite can be used.

  Since the dust D2 collected by the second dust collector 17 is mainly composed of slaked lime, gypsum, and calcium chloride, it is returned to the blending device 2 as a CaO source or a Cl source and added to the waste W for reuse.

  When the exhaust gas G5 of the second dust collector 17 contains NOx, the NOx removal device 18 removes it. The cleaned exhaust gas G6 is exhausted outside the system through the chimney 19.

  As described above, according to the present embodiment, when the dust D1 enriched with radioactive cesium is obtained and the waste W contaminated with the radioactive cesium is reduced in volume, the exhaust gas of the rotary kiln 8 is classified. The radioactive cesium concentration of the resulting coarse powder C is measured, and the coarse powder C is returned to the rotary kiln 8 or disposed of in accordance with the measurement result. Can be maintained at a level.

  In addition, as waste W contaminated with radioactive cesium, soil and incineration ash contaminated with radioactive cesium are illustrated, but besides these, felled trees, waste-derived molten slag, sewage sludge, sewage sludge dry powder, purified water It is possible to cover all wastes such as sludge, construction sludge, sewage slag, shells, vegetation, and debris that contain radioactive cesium. One type in these groups can be used alone, or two or more types Can be combined. Further, an intermediate treatment product enriched with radioactive cesium obtained by removing in advance a portion containing almost no radioactive cesium (sand or stone in the case of soil) is also a waste W contaminated with radioactive cesium in the present invention. include.

In the above embodiment, the CaO source is supplied from the storage tank 4, but a magnesium oxide source (MgO source) can be supplied instead of the CaO source or together with the CaO source. As the MgO source, one containing magnesium carbonate (MgCO ₃ ), magnesium hydroxide (Mg (OH) ₂ ), dolomite, serpentine, ferronickel alloy slag, or the like can be used.

  Moreover, in heating the preparation M, the baking apparatus 7 provided with the rotary kiln 8 and the clinker cooler 9 was used, but other heating furnaces and the like can also be used.

  Furthermore, the obtained earthwork materials are crushed and crushed as necessary, and used as cement mixed materials, aggregates (aggregates for concrete, aggregates for asphalt), backfill materials, embankment materials, roadbed materials, etc. can do. On the other hand, the obtained cement clinker can obtain cement by mixing and crushing gypsum and other materials blended as necessary.

DESCRIPTION OF SYMBOLS 1 Radiocesium removal apparatus 2 Preparation apparatus 3-6 Storage tank 7 Baking apparatus 8 Rotary kiln 8a Input port 8b Burner 9 Clinker cooler 10 Exhaust gas treatment apparatus 11 Cooling tower 11a Sprinkling apparatus 12 Cyclone 13 Measuring apparatus 14 Switching apparatus 15 (15A-15G) Conveyance Route 16 1st dust collector 17 2nd dust collector 18 Denitration device 19 Chimney 21 Flushing device 22 Solid-liquid separator 23 Granulator 24 Storage tank B Burned product C, C1 Coarse powder D1, D2 Dust DC Dehydrated cake F Filtrate G1-G6 Exhaust gas GR Granulated M Formulation N Neutralizing agent S Slurry W (Contaminated with radioactive cesium) Waste

Claims (4)

Mixing waste contaminated with radioactive cesium, calcium oxide source or / and magnesium oxide source, and chlorine source,
Heating the formulation to volatilize the radioactive cesium in the waste,
Cooling the gas generated by heating the formulation;
The dust contained in the gas after cooling is classified into coarse powder and fine powder,
Measure the radioactive cesium concentration of coarse powder after classification,
A method for removing radioactive cesium, comprising determining whether the coarse powder is heated again or disposed of based on a measurement result. In heating the coarse powder again,
Heating the coarse powder with the formulation as it is,
The coarse powder is washed with water and solid-liquid separated and then heated together with the preparation,
After adding a calcium source to the coarse powder and granulating, heat with the formulation,
The method for removing radioactive cesium according to claim 1, wherein either heating is performed separately from the preparation after adding a calcium source to the coarse powder.   3. The radioactive cesium removal according to claim 2, wherein when the radioactive cesium concentration of the coarse powder is 20 times or less of the radioactive cesium concentration of the waste, the coarse powder is heated as it is together with the preparation. Method. A compounding device for preparing a waste contaminated with radioactive cesium, a calcium oxide source or / and a magnesium oxide source, and a chlorine source;
A heating furnace for heating the preparation from the preparation device;
A cooling tower for cooling the exhaust gas of the heating furnace;
A classifier for classifying dust contained in the exhaust gas of the cooling tower into coarse powder and fine powder;
A measuring device for measuring the radioactive cesium concentration of the coarse powder classified by the classifier;
A first transport route for returning the coarse powder to the heating furnace;
A second transport route for discharging the coarse powder out of the system;
An apparatus for removing radioactive cesium, comprising: a switching device that switches the coarse powder conveyance route to either the first conveyance route or the second conveyance route based on a measurement result of the measurement device.

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