JP6632064B2 - Method and apparatus for removing radioactive cesium - Google Patents

Description

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

  In order to remove radioactive cesium taken into the soil, for example, in Patent Document 1, a soil contaminated with radioactive cesium is heated in a rotary kiln, and the kiln exhaust gas is cooled to produce fine powder containing radioactive cesium, and the kiln exhaust gas is removed. A technique is described in which coarse powder is collected and returned to a rotary kiln, and fine powder is collected from kiln exhaust gas. By this technology, radioactive cesium is concentrated to a high concentration as fine powder to reduce the volume, it is possible to reduce the burden of intermediate storage or final disposal, and it is possible to obtain a heating product with a reduced radioactive cesium concentration. it can.

JP 2013-19734 A

  In the above-mentioned radioactive cesium removal technology, since the coarse powder is collected after cooling the kiln exhaust gas, solidified chloride adheres to the coarse powder and the radioactive cesium has a higher concentration than the soil contaminated with radioactive cesium before treatment. Cesium will be included. Then, when this coarse powder is returned to the rotary kiln, radioactive cesium is circulated and concentrated, and the radioactive cesium concentration of the heating product may increase.

  Also, since the coarse powder contains a high concentration of alkali, 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. However, the concentration of radioactive cesium in the heating product will increase.

  If the coarse powder is collected together with the fine powder without returning to the rotary kiln to avoid the above problem, the radioactive cesium concentration of the heating product can be reduced, but the radioactivity of the recovered matter (fine powder and coarse powder) from the kiln exhaust gas can be reduced. The cesium concentration decreases, contrary to the intention of reducing the volume of radioactive cesium-containing waste.

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

In order to achieve the above object, the present invention relates to 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, the gas generated by heating the mixture is cooled, and the dust contained in the cooled gas is classified into coarse powder and fine powder. The radioactive cesium concentration of the powder is measured, and according to the measured radioactive cesium concentration, the coarse powder is heated as it is with the composition, or the coarse powder is washed with water and then heated with the composition after solid-liquid separation. or, or heating with the formulation after the granulation by adding calcium source in the coarse powder, either separately heated from the formulation after addition of the calcium source to the coarse powder, the coarse powder discarded Process And determining whether.

According to the present invention, to determine the treatment method of the coarse powder according to the radioactive cesium concentration of the coarse powder obtained by classifying the gas after cooling, to prevent the circulating concentration of the radioactive cesium concentration, the heating product It is possible to reduce the volume of radioactive cesium-containing waste while maintaining the radioactive cesium concentration at a low level. Here, the term “disposal processing” refers to performing intermediate storage or final disposal.
In addition, by performing an appropriate treatment in accordance with the radioactive cesium concentration of the coarse powder, the volume of radioactive cesium-containing waste can be reduced, and a heating product having a low radioactive cesium concentration can be stably obtained.

  When heating the coarse powder again, when the radioactive cesium concentration of the coarse powder is 20 times or less the radioactive cesium concentration of the waste, the coarse powder can be directly heated together with the preparation. Thereby, the radioactive cesium concentration of the obtained heating product can be kept low.

Furthermore, the present invention relates to an apparatus for removing radioactive cesium, comprising: a mixing apparatus for mixing a radioactive cesium-contaminated waste, a calcium oxide source and / or a magnesium oxide source, and a chlorine source; A heating furnace for heating the mixture, 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, and classified by 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 washing the coarse powder with water. A third transportation route for returning to the heating furnace after solid-liquid separation, a fourth transportation route for returning to the heating furnace after adding a calcium source to the coarse powder, and adding a calcium source to the coarse powder. And then fired separately from the mixture A fifth transport route for returning to the furnace in order, in accordance with radioactive cesium concentration measured by the measuring device switches the transfer route of the coarse powder into one of the first conveyance route to fifth transport route And a switching device.

According to the present invention, among the coarse powders classified by the classifier, the processing method of the coarse powders is determined according to the radioactive cesium concentration of the coarse powders, thereby preventing the circulating concentration of the radioactive cesium concentration, It is possible to reduce the volume of radioactive cesium-containing waste while maintaining the radioactive cesium concentration at a low level.
In addition, by performing an appropriate treatment in accordance with the radioactive cesium concentration of the coarse powder, the volume of radioactive cesium-containing waste can be reduced, and a heating product having a low radioactive cesium concentration can be stably obtained.

  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 heating product generated during the volume reduction of radioactive cesium-containing waste 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 a schematic diagram for explaining operation of a radioactive cesium removal device concerning the present invention. It is a schematic diagram for explaining operation of a radioactive cesium removal device concerning the present invention. It is a schematic diagram for explaining operation of a radioactive cesium removal device concerning the present invention. It is a schematic diagram for explaining operation of a radioactive cesium removal device concerning the present invention. It is a schematic diagram for explaining operation of a radioactive cesium removal device concerning the present invention. It is a schematic diagram for explaining operation of a radioactive cesium removal device concerning the present invention.

  Next, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the following description, radioactive cesium is cesium-134 and cesium-137, which are radioisotopes of cesium.

  FIG. 1 shows an embodiment of a radioactive cesium removing device according to the present invention. The radioactive cesium removing device 1 includes a blending device 2, a baking 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 and incinerated ash contaminated with radioactive cesium, and a storage tank 4 for storing a calcium oxide source (hereinafter, referred to as a “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 blending 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 the CaO source, those containing limestone powder, calcium carbonate, quicklime, slaked lime, limestone, dolomite, blast furnace slag, and the like can be used. Also, Cl source is used to volume reduction and promote, and volatiles recovered material chloride volatilization of radioactive cesium, calcium chloride (CaCl _2), potassium chloride (KCl), sodium chloride (NaCl), chlorine Among them, there are waste plastics and the like, of which CaCl ₂ is preferable because it can effectively remove radioactive cesium.

  The baking apparatus 7 includes a rotary kiln (heating furnace) 8 and a clinker cooler 9. The rotary kiln 8 ejects a fossil fuel such as pulverized coal or an input port 8 a to which the preparation M from the preparation apparatus 2 is supplied. And a baked product (heat product) is obtained by baking the preparation M and the like.

  The exhaust gas treatment device 10 is disposed downstream of the firing device 7 and cools the exhaust gas G1 discharged from the rotary kiln 8, a cyclone 12 disposed downstream of the cooling tower 11, and recovered by the cyclone 12. Measuring device 13 for measuring the radioactive cesium concentration of coarse powder C, transport route 15 for coarse powder C (15A-15G), and switching device 14 for switching transport route 15 for coarse powder C based on the measurement result of measuring device 13 A first dust collector 16, a second dust collector 17, a denitration device 18 for denitrifying an exhaust gas G <b> 5 from which dust such as concentrated cesium salt has been removed by the two dust collectors 16 and 17, and an exhaust gas G <b> 6 of the denitration device 18 to the outside of the system. And a chimney 19 for 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 cooling of the exhaust gas G1 is performed by spraying water from a water sprinkling device 11a installed at the lower end of the cooling tower 11. The sprinkler 11a only needs to have a function capable of attaching the volatilized cesium chloride to the dust contained in the exhaust gas G1 as a solid and collecting it. 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 high-concentration radioactive cesium with 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 radioactivity concentration of the sample from the surface dose rate in the hopper, or a radioactivity concentration meter installed so as to surround the hopper. The radioactivity concentration of the coarse powder C is measured at. When measuring from outside, it is necessary to confirm in advance the relationship (coefficient) between the surface dose rate and the radioactivity concentration of the sample. Alternatively, the target sample is filled in a special container or formed into a prescribed shape and then flown on a conveyor, or is flown after being arranged in a predetermined shape on the conveyor, and is set to surround the conveyor (configured with a NaI detector or the like). Also, the sample is continuously measured for the radioactivity concentration by passing through a radioactivity concentration measuring device. Among them, the hopper method is desirable from the viewpoint of preventing the coarse powder from leaking to the outside. Since the coarse powder is cooled, the surface can be measured directly, or the measurement can be performed by arranging a detector in the coarse powder filled in the hopper.

  As the transport route 15, first to fifth transport routes 15A to 15E for returning the coarse powder C to the rotary kiln 8, a sixth transport route 15F and a seventh transport route for discharging the coarse powder C out of the system of the radioactive cesium removing device 1. There are seven transport routes 15A to 15G of 15G. Although the 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 the coarse powder C to the rotary kiln 8 via a processing device.

  The sixth transport route 15F and the seventh transport route 15G are for discharging the coarse powder C out of the system of the radioactive cesium removing device 1, and the details will be described later. Is directly discharged to the outside of the system, and the seventh transport route 15G is a route that does not directly discharge the coarse powder C to the outside of the system but discharges the coarse powder C to the outside of the system without passing through the rotary kiln 8.

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

  The second dust collector 17 is provided for removing an acid gas and the like contained in the exhaust gas G4 after removing the cesium salt and the like, and adds a neutralizing agent N containing a calcium component to a neutralizing agent adding device (not shown). And collects dust D2 adsorbing acid gas and the like. A bag filter or the like is also used for the second dust collector 17.

The denitration device 18 is provided for injecting 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, a waste M contaminated with radioactive cesium, a CaO source and a Cl source as reaction accelerators are drawn out from the storage tanks 3 to 5 and blended to obtain a blend M. Formulation M has a composition of an earthwork material that does not produce C ₃ S (erite) when fired, or a cement clinker containing C ₃ S.

In the case of manufacturing an earthwork material, the waste W and the waste W are mixed 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 mix the CaO source after determining its type and mixing ratio. In the formula, CaO, MgO, and SiO ₂ represent a mass in terms of calcium oxide, a mass in terms of magnesium oxide, and a mass in terms of silicon oxide, respectively. The value (mass ratio) on the right side of the above equation calculated by the mass of each of the above equations 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, since the mass of 1 mol of CaO corresponds to the mass of 1.39 mol of MgO, 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 increases, and the volatilization amount of radioactive cesium may decrease. When the mass ratio exceeds 2.7, the sum of the volatilization amounts 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, The amount of dust obtained by cooling the exhaust gas G2 may increase.

On the other hand, in the case of manufacturing a cement clinker, the waste is adjusted so that the relationship between CaO, SiO ₂ and MgO in the composition M satisfies (CaO + 1.39 × MgO) / SiO ₂ = 2.7 to 3.7. It is preferable to mix W and CaO sources after determining their types and mixing ratios.

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

  In addition, it is preferable that the amount of the Cl source be adjusted so that it is equal to or more than radioactive cesium contained in the waste material W when producing both earthwork materials and cement clinkers. The upper limit of the amount of the Cl source is such that the molar ratio Cl / (Cs + K) of chlorine to cesium and potassium is preferably 1.5 or less, more preferably 1.0 or less. When the 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 an earthwork material, it is preferable to perform the above-mentioned preparation and the following firing so that the calcium oxide concentration of the earthwork material (fired material B) becomes 50% by mass or more. Thereby, the sulfur content is retained in the earthwork material, or is collected as a sulfur compound in the first dust collector 16 described later as the dust D1 of the exhaust gas G3, so that the circulation of the sulfur content can be suppressed and the load of the exhaust gas treatment can be reduced. It is possible to reduce the increase and the increase in coaching.

  Formulation M is charged from storage tank 6 into rotary kiln 8 through charging port 8a, and fired at 1200 ° C. or higher and 1550 ° C. or lower to obtain fired product B. Here, the oxygen partial pressure in the rotary kiln 8 is set to 3% or more, preferably 5% or more. Thereby, decomposition of the sulfur compound in the rotary kiln 8 is suppressed, and the circulation of the sulfur is suppressed. Therefore, an increase in the amount of the neutralizing agent used and an increase in the amount of the coating applied 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 volatilized in the cyclone 12 while being contained in the exhaust gas G1. Is introduced to

  The exhaust gas G1 is rapidly cooled in the cooling tower 11 by water sprayed from the water spray device 11a, and cesium chloride contained in the exhaust gas G1 becomes a solid cesium salt. Most of the cesium salt is recovered as dust D1 as fine powder, but a part of the cesium salt adheres to coarse dust.

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

  Here, when the radioactive cesium concentration of the coarse powder C measured by the measuring device 13 is relatively low, the switching device 14 switches to one of the first to fifth transport routes 15A to 15E, and the coarse powder C is 8, 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 for determining whether to return the coarse powder C to the rotary kiln 8 or to discharge the coarse powder C to the outside of the system is 200,000 Bq / kg or less, which is a concentration that can be handled when only earthwork materials are manufactured. In the case of producing only aggregate and cement, or only cement, the concentration is set to 1,000,000 Bq / kg or less, which is a concentration that can be handled by the cement composition. The reason why the value of cement is higher is that cement has a higher Ca content and therefore is less likely to be melted even at high temperatures, and the cesium volatilization rate by firing becomes higher. Therefore, the coarse powder C exceeding 200,000 Bq / kg and 1,000,000 Bq / kg or less has to be heated as the composition of the cement clinker, and the coarse powder C exceeding 1,000,000 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 of the waste W, as shown in FIG. Switching to the transport route 15A, the coarse powder C is returned directly to the rotary kiln 8. The amount of the coarse powder is usually 2% by mass and 5% at most in a short period of time, so that if it is 20 times or less, it does not significantly affect the radioactive Cs of the fired material. If it is higher than that, the frequency of the radioactive Cs concentration of the fired product being 100 Bq / kg or more increases.

  Further, as shown in FIG. 3, without returning the coarse powder C directly to the rotary kiln 8, the transport route is switched to the second transport route 15 </ b> B by the switching device 14, returned to the storage tank 3 for the waste W, and returned to the storage tanks 4 and 5. Mixing with a 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 of the waste W, as shown in FIG. Switching to the third transport route 15C, the coarse powder C is washed with the washing device 21, the slurry S from the washing device 21 is dewatered by the solid-liquid separator 22, and the obtained dewatered cake DC is returned to the rotary kiln 8. Thereby, radioactive cesium and a part of 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, it is necessary to provide a drying means in the storage tank 6.

  It is preferable to use a filter press as the solid-liquid separator 22 because the dewatered cake DC becomes clumpy and a granulated product can be obtained only by crushing it. Separately, a granulator such as a pug mill, a dish-type pelletizer, a drum-type granulator, and 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 melting of the granulated material and promote volatilization of radioactive cesium contained in the granulated material. In addition, since the amount of dust generated in the rotary kiln 8 is reduced, the amount of radioactive cesium-containing waste generated is also reduced. Here, when the particle size is larger than 100 mm, the granulator becomes excessively large, and the apparatus and operating costs increase. On the other hand, when the particle size is smaller than 10 mm, the specific surface area becomes large, and the effect of granulation is undesirably reduced. .

  It is not necessary to strictly perform the solid-liquid separation in the solid-liquid separator 22. For example, as in the case of centrifugal separation or sedimentation separation, a part of the filtrate F is mixed in the dewatered cake DC to form a slurry. It may be. Conversely, some coarse powder may be mixed into the filtrate F.

  On the other hand, the filtrate F from the solid-liquid separator 22 is sprayed in the cooling tower 11 through the water sprinkler 11a to evaporate the water content of the filtrate F, and the solid radioactive cesium is collected by the first dust collector 16 described later. 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 to the exhaust gas G3, the radioactive cesium circulates. Can be reliably prevented. In this case, it is not always necessary to cool the radioactive cesium to a temperature at which the radioactive cesium becomes solid in the cooling tower 11, but it is sufficient to cool the radioactive cesium to a temperature at which the radioactive cesium becomes solid in the first dust collector 16. As a result, the radiocesium concentration of the coarse powder C1 decreases, and the radioactive cesium can be more concentrated in the dust D1.

  Further, 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 of the waste W, as shown in FIG. After switching to the fourth transport route 15D and adding the CaO source to the coarse powder C, the coarse powder C is granulated by the granulator 23, and the obtained granulated material GR can be returned to the rotary kiln 8. By this granulation, the specific surface area can be reduced, the melting of the granulated material GR can be prevented, and the volatilization of radioactive cesium contained in the granulated material GR can be promoted.

The addition amount of the CaO source is a composition that generates C ₃ S (alite) when fired. By using a cement clinker containing C ₃ S, cement of the same quality as commercially available Portland cement can be manufactured. 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 equation calculated by the mass of each of the above CaO, MgO, and SiO ₂ is 2.7 or more, the granulated material GR becomes difficult to melt, so that the radioactive cesium becomes more Many volatilize. On the other hand, if 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 equation is 2.96, the Cs removal rate is 99.995%, but when the value is 2.0, it is 99.955%. In addition, by adjusting the silicic acid ratio (SM) of the granulated material GR to 1.3 to 3.0 and the iron ratio (IM) to 1.3 to 2.8, a desired cement is obtained. The clinker CL is manufactured.

Further, calcium chloride (CaCl ₂ ) may be further added as a Cl source for the purpose of accelerating the chlorination of radioactive cesium and reducing the volume of the volatile recovery. The upper limit of the amount of the Cl source is such that the molar ratio of chlorine to 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 substance-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, if the particle size is larger than 100 mm, the granulator 23 becomes excessively large, and the equipment and operating costs increase. Absent. The coarse powder C1 after the addition of the Ca source may be granulated after washing with water and solid-liquid separation shown in FIG.

  When the radiocesium concentration of the coarse powder C measured by the measuring device 13 is 200 times or less, preferably 100 times or less of the waste W, as shown in FIG. Switching to the fifth transport route 15E, a CaO source is added to the coarse powder C and temporarily stored in the storage tank 24, and the coarse powder C1 from the storage tank 24 is returned to the rotary kiln 8 and fired 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 firing dates of the coarse powder C1 and the preparation M are shifted or the firing timing is shifted. Since the coarse powder C1 is fired alone, it does not affect the firing of the blended raw material M (volatilization of radioactive cesium). Since the calcination is performed alone, a calcination product B having a low radioactive Cs concentration can be obtained by adjusting the calcination time and the calcination amount, even if the radiation concentration of the coarse powder C1 is high. The method of adding the CaO source and the method of adjusting the composition are the same as those in the case where the granulator 23 of FIG. 5 is installed. Obtainable.

  On the other hand, when the radioactive cesium concentration of the coarse powder C measured by the measuring device 13 exceeds 200 times the waste W, as shown in FIG. 7, the switching device 14 switches the transport route to the sixth transport route 15F. And can be discharged directly to the outside of the system of the radioactive cesium removal device 1 by being combined with the dust D1 of the first dust collector 16. Further, instead of directly discharging the coarse powder C out of the system of the radioactive cesium removing device 1, the transport route may be switched to the seventh transport route 15G by the switching device 14 to join the exhaust gas G3 of the cyclone 12.

  This concludes the description of the switching of the transport routes (15A to 15G) by the switching device 14, and then describes the subsequent processing of the cyclone 12.

  The dust contained in the exhaust gas G3 of the cyclone 12 in FIG. 1 is collected by the first dust collector 16 as dust D1. The collected dust D1 can be further sealed, if necessary, by compressing, washing, adsorbing, etc., and then sealed and stored in a concrete container or the like. The volume can be reduced and stored without leakage. It can also be buried in the ground for final disposal.

  Since the exhaust gas G4 after collecting the concentrated cesium salt contains a harmful gas such as an acid gas, the neutralizer N is added to the exhaust gas G4 from the neutralizer adding device, and then the exhaust gas G4 is discharged by the second dust collector 17. Dust D2 adsorbing an acid gas or the like is collected from G4. Here, as the neutralizing agent N, one containing at least one selected from the group consisting of slaked lime, quicklime, dolomite, lightly burned dolomite, and hydroxide 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 mixing device 2 as a CaO source or a Cl source, added to the waste W and reused.

  If the exhaust gas G5 of the second dust collector 17 contains NOx, it is removed by the denitration device 18. The cleaned exhaust gas G6 is exhausted to the outside of the system through the chimney 19.

  As described above, according to the present embodiment, when dust D1 enriched with radioactive cesium is obtained to reduce the volume of waste W contaminated with radioactive cesium, the exhaust gas from rotary kiln 8 is classified and obtained. The radioactive cesium concentration of the obtained coarse powder C is measured, and the coarse powder C is returned to the rotary kiln 8 or discarded according to the measurement result. Therefore, the radioactive cesium concentration of the calcined product B is reduced by preventing the circulating concentration of the radioactive cesium. Can be maintained at the level.

  In addition, as the waste W contaminated with radioactive cesium, the soil and incineration ash contaminated with radioactive cesium were exemplified, but in addition to these, felled trees, molten slag derived from garbage, sewage sludge, sewage sludge dry powder, water purification Wastes such as sludge, construction sludge, sewage slag, shells, plants, debris, etc. that can contain all radioactive cesium can be targeted. One of these groups alone or two or more Can be combined. Further, an intermediate treatment product enriched with radioactive cesium, which is obtained by previously removing a portion containing little radioactive cesium (in the case of soil, sand or stone), 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) may be supplied instead of the CaO source or together with the CaO source. As the MgO source, those containing magnesium carbonate (MgCO ₃ ), magnesium hydroxide (Mg (OH) ₂ ), dolomite, serpentine, ferronickel alloy slag, and the like can be used.

  In addition, in heating the preparation M, the baking apparatus 7 including the rotary kiln 8 and the clinker cooler 9 was used, but another heating furnace or the like may be used.

  In addition, the obtained earthwork material is crushed or crushed as necessary, and used as cement mixture, aggregate (aggregate for concrete, aggregate for asphalt), backfill material, embankment material, roadbed material, etc. can do. On the other hand, the obtained cement clinker can obtain a cement by mixing gypsum and other materials to be blended as needed and pulverizing the mixture.

REFERENCE SIGNS LIST 1 Radioactive cesium removing device 2 Mixing device 3 to 6 Storage tank 7 Firing device 8 Rotary kiln 8 a Input port 8 b Burner 9 Clinker cooler 10 Exhaust gas treatment device 11 Cooling tower 11 a Sprinkler device 12 Cyclone 13 Measuring device 14 Switching device 15 (15A to 15G) Transportation Route 16 First dust collector 17 Second dust collector 18 Denitration device 19 Chimney 21 Washing device 22 Solid-liquid separator 23 Granulator 24 Storage tank B Burned product C, C1 coarse powder D1, D2 Dust DC Dewatered cake F Filtrate G1 to G6 Exhaust gas GR Granules M Formulation N Neutralizer S Slurry W Waste (contaminated with radioactive cesium)

Claims (3)

Combining radioactive cesium-contaminated waste, a calcium oxide source and / or a magnesium oxide source, and a chlorine source,
Heating the composition to volatilize radioactive cesium in the waste,
Cooling the gas generated by heating the formulation,
Dust contained in the gas after cooling is classified into coarse powder and fine powder,
Measure the radioactive cesium concentration of the coarse powder after classification,
Depending on the measured radiocesium concentration ,
Heating the coarse powder with the formulation as it is,
After the coarse powder is washed with water and separated into solid and liquid, it is heated together with the preparation,
After adding the calcium source to the coarse powder and granulating, heating with the preparation,
After adding the calcium source to the coarse powder, heating separately from the formulation,
Method of removing radioactive cesium, characterized in that to determine the coarse particles to disposal processing. The radioactive cesium removal according to claim 1 , 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 directly heated together with the preparation. Method. A mixing device for mixing a radioactive cesium-contaminated waste, a calcium oxide source and / or a magnesium oxide source, and a chlorine source;
A heating furnace for heating the blend from the blender;
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 directly to the heating furnace,
A second transport route for discharging the coarse powder out of the system;
A third transport route for returning the heating to the heating furnace after the coarse powder is washed with water and solid-liquid separated;
A fourth transport route for returning to the heating furnace after granulation by adding a calcium source to the coarse powder,
A fifth transport route to return to the heating furnace for baking separately from the mixture after adding a calcium source to the coarse powder,
Depending on the radioactive cesium concentration measured by the measuring device, the removal of radioactive cesium, characterized in that the conveying route of the coarse powder and a switching device for switching to either the first conveyance route to fifth transport route apparatus.

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