JP2017165591A - Method for producing fired product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a fired product that produces a fired product having reduced radioactive cesium concentration by subjecting an object to be treated to an appropriate heating treatment in accordance with a radioactive cesium concentration of a radioactive cesium-contaminated object to be treated so as to produce a fired product usable in an appropriate application.SOLUTION: The method for producing a fired product includes a cesium concentration measurement step of measuring a radioactive cesium concentration contained in an object to be treated and a heating step of adjusting its components of the object to be treated to produce an object to be heated or producing an object to be heated without adjusting its components and then heating the object to be heated and volatilizing the radioactive cesium to produce a fired product. After the cesium concentration measurement step, the application of the fired product is determined by selecting from among a plurality of applications including at least the application to a cement clinker and the application to an earthwork material in accordance with the radioactive cesium concentration and the object to be heated is prepared in accordance with the application of the fired product.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a harmless fired product using a processing object contaminated with radioactive cesium as a raw material.

There is a problem that radioactive cesium released into the external environment due to a major accident at a nuclear power plant may be contained in waste or soil. Radioactive cesium (cesium 137) has a half-life of 30 years and can adversely affect the human body over a long period of time. Therefore, it is required to remove radioactive cesium from wastes and treat it.
Additives to waste contaminated with radioactive cesium, adjust the chemical composition of the waste, etc., then heat treatment to volatilize the radioactive cesium, and the radioactive cesium in the fired product after the heat treatment A technique for using the fired product as various materials after reducing the concentration has been proposed.
For example, Patent Document 1 discloses that waste contaminated with radioactive cesium and a CaO source and / or MgO source are heated at 1,200 to 1,350 ° C. to volatilize radioactive cesium in the waste. A method for producing a baked product including a heating step for obtaining a baked product, wherein, in the heating step, the waste and the CaO source so that each mass of CaO, MgO, and SiO ₂ satisfies a specific formula. And the manufacturing method of the baked product characterized by determining each kind and compounding ratio of MgO source is described.
Patent Document 1 describes that the obtained fired product is used as a cement admixture, an aggregate, or an earthwork material.

Further, Patent Document 2 discloses wastes contaminated with radioactive cesium, CaO source and / or MgO source, chloride, and P ₂ O ₅ source and / or Na ₂ O source from 1,250 to 1,450. A method for producing a calcined product comprising a heating step of heating at 0 ° C. to volatilize radioactive cesium in the waste to obtain a calcined product, wherein each mass of CaO, MgO, and SiO _{2 in} the heating step Satisfy the specific formula and the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) satisfies 0.6 to 2.0, the waste, CaO source and MgO source, chloride As the ratio in 100% by mass of the fired product obtained after the heating step, the ratio of P ₂ O ₅ is 0.3% by mass or more, or the ratio of Na ₂ O is 1. 0% by mass or more and Na ₂ A method for producing a fired product is described in which the types and blending ratios of the P ₂ O ₅ source and the Na ₂ O source are determined so that the O ratio is 5.0% by mass or less.
Patent Document 2 describes that the obtained fired product is used as an aggregate or earthwork material.

Japanese Patent No. 5159971 JP, 2014-106017, A

Wastes and the like contaminated with radioactive cesium are from a relatively low concentration in which the radioactive cesium concentration in the wastes and the like is slightly over 8,000 Bq / kg, and from several million to several billion Bq / There are a wide range of products with high concentration of kg. For this reason, the volatilization rate of the radioactive cesium required in order to make radioactive cesium density | concentration in waste etc. below a clearance level changes with radioactive cesium density | concentrations, such as a waste which is a process target.
In addition, as a technology to reduce the volume of waste contaminated with radioactive cesium, by classifying the waste contaminated with radioactive cesium, etc., parts that do not contain radioactive cesium (for example, stones in soil) The technology to remove is known. Examples of uses of the material obtained by the classification treatment include aggregates, embankment materials, roadbed materials and the like.
When treating waste contaminated with radioactive cesium by the heat treatment and classification treatment described above, it is necessary to perform appropriate treatment in consideration of the concentration of radioactive cesium such as waste and the demand for the fired product obtained. It is conceivable that the radioactive cesium concentration may be insufficiently reduced, or a fired product for a specific application may be produced excessively, resulting in excessive supply.
Accordingly, an object of the present invention is to obtain a fired product having a reduced radioactive cesium concentration by performing an appropriate heat treatment in accordance with the radioactive cesium concentration in the treatment object contaminated with radioactive cesium and the use of the fired product. It is providing the manufacturing method of the baked product which can be performed.

As a result of intensive studies to solve the above problems, the present inventor has performed a cesium concentration measurement step for measuring the concentration of radioactive cesium in a processing object contaminated with radioactive cesium, and the processing object for which the radioactive cesium concentration has been measured. Without adjusting the components or adjusting the components to obtain the heating object, and then heating the heating object to volatilize radioactive cesium to obtain a fired product, including the radioactive material in the processing object The present invention has been completed by finding that the above object can be achieved according to the method for producing a calcined product in which the use of the calcined product is determined by the cesium concentration and the heating object is prepared according to the use of the calcined product in the heating step.
That is, the present invention provides the following [1] to [8].

[1] A method for producing a fired product having a reduced concentration of radioactive cesium by heating a treatment object contaminated with radioactive cesium, wherein the radioactive substance in the treatment object contaminated with the radioactive cesium After the cesium concentration measurement step for measuring the cesium concentration and the processing object for which the radioactive cesium concentration has been measured in the cesium concentration measurement step without adjusting the components or adjusting the components to obtain the heating object, the heating is performed. Heating the object to volatilize radioactive cesium in the object to be treated to obtain a fired product, and after the cesium concentration measurement step, the use of the fired product is determined by the radioactive cesium concentration. When the use of cement clinker and the use of earthwork materials are selected and determined from multiple uses, and the use of the fired product is set for cement clinker, the above In the heating step, the heating object is prepared so that the mass ratio represented by the following formula (1) of CaO, MgO, and SiO ₂ exceeds 2.7, and then heated and used as the cement clinker. In the heating process, when the use of the fired product is determined as an earthwork material (for example, aggregate, embedding agent, roadbed material, backfill material, security gravel, etc.), MgO, and as the mass ratio represented by SiO ₂ of the formula (1) is 1.0 to 2.7, after preparation of the heating object is heated, for use as the earthwork material A method for producing a fired product, comprising obtaining a fired product.
Mass ratio = ((CaO + 1.39 × MgO) / SiO ₂ ) (1)
(In the formula, CaO, MgO, and SiO ₂ represent a mass in terms of oxide of calcium, a mass in terms of oxide of magnesium, and a mass in terms of oxide of silicon, respectively.)
[2] If the radioactive cesium concentration is equal to or higher than a specific value, the application is selected from the plurality of uses as determined by the cement clinker application, and the radioactive cesium concentration is lower than a specific value. The method for producing a fired product according to the above [1], which is determined for the use of earthwork materials.
[3] As a plurality of uses of the fired product, in addition to the use of the cement clinker and the use of earthwork materials, a cement admixture (in other words, a material other than cement, water, aggregate, mortar or concrete In the calculation of blending, the use of a material used in such a large amount that the use amount is taken into account is included, and when the use of the fired product is determined as a cement admixture, , MgO, and SiO ₂ are prepared so that the mass ratio represented by the above formula (1) is 1.0 to 2.2, and then heated and used as the cement admixture. The method for producing a fired product according to [1], wherein a fired product for obtaining the fired product is obtained.
[4] When selecting the use from the plurality of uses, when the radioactive cesium concentration is equal to or higher than a specific value, the use is determined as a cement clinker application, and the radioactive cesium concentration is less than a specific value. The method for producing a fired product according to the above [3], which is determined for use of one or both of earthwork materials and cement admixtures.

[5] When the radioactive cesium concentration is 200,000 Bq / kg or more after the cesium concentration measurement step, the following method (a) is selected in the heating step, and the radioactive cesium concentration is 30,000 Bq. / Kg or more and less than 200,000 Bq / kg, in the heating step, any one of the following methods (a) to (d) is selected, and the radioactive cesium concentration is less than 30,000 Bq / kg In the heating step, by selecting one of the following methods (b) to (f), the use of the fired product can be selected from cement clinker, earthwork material, and cement admixture. The method for producing a fired product according to the above [3] or [4].
(A) The mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ exceeds 2.7, the silicic acid ratio (SM) exceeds 1.3, and chlorine and cesium In order to use as a cement clinker after preparing the heating object so that the molar ratio (Cl / (Cs + K)) to potassium is 1.0 or less, and then heating at 1,400 to 1,550 ° C. (B) The mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ is 1.8 to 2.7, and the silicic acid ratio (SM) is 2. Exceeding 0.0, the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.5 or less, and the ratio of P ₂ O ₅ in 100% by mass of the fired product obtained after heating is 0 After preparing the heating object so as to be 3% by mass or more, 1,250-1,450 In heating, the method of obtaining a calcined product for use as earth moving material (c) CaO, MgO, and mass ratio represented by SiO ₂ in the formula (1) exceeds 2.2, 2.7 or less Yes, the silicic acid ratio (SM) exceeds 2.0, the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.5 or less, and the fired product obtained after heating To prepare the heating object so that the ratio of P ₂ O ₅ in 100% by mass is less than 0.3% by mass, and then heat at 1,250-1450 ° C. for use as an earthwork material (D) The mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ is 1.8 to 2.2, and the silicic acid ratio (SM) is 2. More than 0.0 and the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.5 or less And, as the proportion of _P 2 _{O 5} of calcined product in 100% by mass obtained after heating it is less than 0.3 wt%, after preparation of the heating object, heated at 1,250～1,450 ° C. And (e) a mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ is 1.0 to 1.8, and silicic acid. After preparing the heating object so that the rate (SM) exceeds 2.3 and the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.5 or less Method for obtaining a fired product for use as an earthwork material by heating at 1,200 to 1,400 ° C. (f) The mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ is 1. After preparing the heating object so as to be 0 to 1.8, 1,200 to 1,4 A fired product for use as a cement admixture by heating at 00 ° C. to obtain a fired product, and then pulverizing the fired product to have a Blaine specific surface area of 2,800-4,200 cm ² / g. How to get

[6] In the method (a), when the silicic acid ratio (SM) exceeds 1.3 and is 1.6 or less, the mass ratio represented by the above formula (1) is 3.0 to 3. And when the silicic acid ratio (SM) exceeds 1.6 and is 2.0 or less, the mass ratio represented by the above formula (1) is 2.8 to 3.5, When the silicic acid ratio (SM) exceeds 2.0, the heating object is prepared so that the mass ratio represented by the formula (1) exceeds 2.7 and is 3.3 or less. The method for producing a fired product according to [5].
[7] In the heating step, the heating object includes at least one of a CaO source and an MgO source in addition to the processing object, and at least one type of the CaO source and the MgO source and the above The manufacturing method of the baked product in any one of said [1]-[6] which prepares the said heating target object by defining the mixture ratio with respect to a process target object.
[8] After obtaining a cement clinker by the method for producing a fired product according to any one of [1] to [7], the cement clinker is pulverized, and the obtained cement clinker pulverized product and gypsum are mixed. To obtain cement, a method for producing cement.

  According to the method for producing a fired product of the present invention, a fired product in which the radioactive cesium concentration is reduced by performing an appropriate heat treatment in accordance with the radioactive cesium concentration of the processing object contaminated with radioactive cesium and the use of the fired product. Can be manufactured.

The method for producing a baked product of the present invention is a method for producing a baked product having a reduced concentration of radioactive cesium by heating a processing object contaminated with radioactive cesium and contaminated with radioactive cesium. The cesium concentration measurement process that measures the radioactive cesium concentration in the object to be treated, and the treatment object that has already been measured in the cesium concentration measurement process, without adjusting the ingredients or by adjusting the ingredients, obtain the heating object Then, the heating object is heated to volatilize radioactive cesium in the treatment object to obtain a fired product, and after the cesium concentration measurement step, the use of the fired product is determined by the radioactive cesium concentration. If you select at least several uses including cement clinker and earthwork materials, and set the use of fired products to cement clinker, Te, CaO, MgO, and so mass ratio represented by SiO ₂ of the formula (1) exceeds 2.7, after the heating object is prepared, heated, calcined product for use as a cement clinker In the heating process, the mass ratio represented by the following formula (1) of CaO, MgO, and SiO ₂ is 1.0 to 2.7. The method for producing a fired product obtained by preparing a heated object and then heating to obtain a fired product for use as an earthwork material.
Mass ratio = ((CaO + 1.39 × MgO) / SiO ₂ ) (1)
(In the formula, CaO, MgO, and SiO ₂ represent a mass in terms of oxide of calcium, a mass in terms of oxide of magnesium, and a mass in terms of oxide of silicon, respectively.)
Hereinafter, each step will be described in detail.

[Cesium concentration measurement process]
This step is a step of measuring the concentration of radioactive cesium in the processing object contaminated with radioactive cesium.
In the present invention, radioactive cesium means cesium 134 and cesium 137, which are radioactive isotopes of cesium. These radioactive cesiums are radioactive substances that are released into the external environment by accidents at nuclear power plants, and have half-lives of about 2 years and about 30 years, respectively.
Examples of treatment objects contaminated with radioactive cesium include, for example, soil (including classified sludge), sewage sludge dry powder, sewage sludge incineration ash, municipal waste incineration ash, waste-derived molten slag, shells, vegetation, etc. Agricultural and forestry waste such as waste, pruned leaves, bark, compost, rice straw, grass, rice bran, industrial waste such as sewage sludge, sewage slag, purified water sludge, construction sludge, debris, contaminated water treatment sludge Disaster waste such as those containing radioactive cesium. These may be used individually by 1 type and may be used in combination of 2 or more type. In addition, soil that has been contaminated with radioactive cesium is classified to obtain a radioactive cesium-enriched product (intermediate treatment product) that is obtained by preliminarily removing parts that do not contain radioactive cesium (for example, sand and stone). Are also included in the concept of “processing object contaminated with radioactive cesium” in the present invention.

  A method for measuring the concentration of radioactive cesium in the processing object contaminated with radioactive cesium is not particularly limited, and examples thereof include a measurement method using a germanium semiconductor detector or a NaI scintillation detector.

[Heating process]
In this process, the processing object whose radioactive cesium concentration has been measured in the cesium concentration measurement process is obtained by heating the heating object after obtaining the heating object without adjusting the ingredients or adjusting the ingredients. In this process, radioactive cesium in the product is volatilized to obtain a fired product.
In the present invention, depending on the radioactive cesium concentration in the object to be treated, the use of the fired product is selected and selected from a plurality of uses including at least the use of cement clinker and the use of earthwork materials. Appropriate heat treatment suitable for is performed.
The obtained fired product is used as it is or after being pulverized in accordance with various uses.
Specifically, when the use of the baked product is defined as cement clinker, heating is performed so that the mass ratio represented by the following formula (1) of CaO, MgO, and SiO ₂ exceeds 2.7 in the heating step. After preparing the object, it can be heated to obtain a fired product for use as a cement clinker.
When the use of the fired product is determined as a cement clinker, the heating temperature is preferably 1,400 to 1,550 ° C, more preferably 1,420 to 1,500 ° C.
Mass ratio = ((CaO + 1.39 × MgO) / SiO ₂ ) (1)
(In the formula, CaO, MgO, and SiO ₂ represent a mass in terms of oxide of calcium, a mass in terms of oxide of magnesium, and a mass in terms of oxide of silicon, respectively.)
In addition, since the mass of 1 mol of CaO corresponds to the mass of 1.39 mol of MgO, in the above formula (1), the mass of MgO is multiplied by 1.39.

Moreover, when the use of the fired product is defined as an earthwork material, in the heating step, the mass ratio represented by the following formula (1) of CaO, MgO, and SiO ₂ is 1.0 to 2.7. After preparing a heating object, it can heat and can obtain the baked material for using as an earthwork material.
When the use of the fired product is determined for earthwork materials, the heating temperature is preferably 1,200 to 1,450 ° C, more preferably 1,250 to 1,420 ° C.

As a plurality of uses of the fired product, in addition to the use of cement clinker and the use of earthwork material, the use of cement admixture may be included.
When the use of the fired product is defined as a cement admixture, in the heating step, heating is performed so that the mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ is 1.0 to 2.2. After preparing the object, it can be heated to obtain a fired product for use as the cement admixture.
When the use of the fired product is determined as a cement admixture, the heating temperature is preferably 1,200 to 1,450 ° C, more preferably 1,250 to 1,420 ° C.

When selecting the use of the fired product from multiple uses, the radioactive cesium concentration in the treatment object is determined by the use of the cement clinker when the radioactive cesium concentration in the treatment object is higher than a specific value. Is less than a specific value, it is preferable to determine the use for either or both of earthwork materials and cement admixtures.
A specific value that serves as an index for selecting an application may be appropriately determined in consideration of the concentration of radioactive cesium in the object to be processed, the demand for the fired product, and the like.

In addition, the heat treatment conditions may be more finely determined depending on the radioactive cesium concentration in the object to be treated and the use of the fired product. By more precisely defining the conditions for the heat treatment, it is possible to process the object to be processed more appropriately.
For example, when the radioactive cesium concentration in the object to be treated is 200,000 Bq / kg or more, in this step, the following method (a) can be selected, and the use of the obtained fired product can be determined for the cement clinker. .
When the radioactive cesium concentration in the object to be treated is 30,000 Bq / kg or more and less than 200,000 Bq / kg, in this step, select one of the following methods (a) to (d) Thus, the use of the obtained fired product can be defined as any one of cement clinker, earthwork material, and cement admixture.
When the radioactive cesium concentration in the object to be treated is less than 30,000 Bq / kg, in this step, by selecting any one of the following methods (b) to (f), A use can be defined as either an earthwork material or a cement admixture.

(1) Method (a)
In the method (a), the mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ exceeds 2.7, the silicic acid ratio (SM) exceeds 1.3, and After preparing the object to be heated so that the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.0 or less, it is heated at 1,400 to 1,550 ° C. as a cement clinker. This is a method for obtaining a fired product for use.
When the mass ratio represented by the above formula (1) exceeds 2.7, the obtained fired product can be more suitably used as a cement clinker.
In addition, when the radioactive cesium concentration in the object to be treated is 200,000 Bq / kg or more, if the mass ratio is 2.7 or less, the volatilization rate of the radioactive cesium becomes small, and the radioactive material in the obtained fired product In some cases, the cesium concentration cannot be sufficiently reduced. The upper limit of the mass ratio is not particularly limited, but is preferably 3.7 or less from the viewpoint of physical properties of the obtained cement clinker. In addition, since it becomes difficult to handle and the concentration of radioactive cesium in the fired product obtained may not be sufficiently reduced, the concentration of radioactive cesium in the object to be treated is preferably 100 million Bq / kg or less. .

When the silicic acid ratio (SM) is 1.3 or less, a liquid phase is likely to be formed during heating, and radioactive cesium is hardly volatilized by being incorporated into the liquid phase.
Here, the silicic acid ratio is a mass ratio of SiO ₂ to Al ₂ O ₃ and Fe ₂ O ₃ (SiO ₂ / (Al ₂ O ₃ + Fe ₂ O ₃ )).
In addition, from the viewpoint of obtaining a cement clinker with superior quality, the heating object is prepared so that the mass ratio represented by the above formula (1) falls within a specific numerical range according to the numerical value of the silicic acid ratio. May be.

Specifically, when the silicic acid ratio exceeds 1.3 and is 1.6 or less, the heating object is adjusted so that the mass ratio represented by the above formula (1) is 3.0 to 3.7. It is preferable to prepare. When the ratio is 3.0 or more, the amount of alite (3CaO · SiO ₂ ) in the cement using the obtained cement clinker is increased, and the strength expression of the cement clinker is further improved. If this ratio is 3.7 or less, the remaining amount of free lime is reduced, and the quality of the cement using the resulting cement clinker is further improved.
When the silicic acid ratio exceeds 1.6 and is 2.0 or less, it is preferable to prepare the heating object so that the mass ratio represented by the above formula (1) is 2.8 to 3.5. . When the ratio is 2.8 or more, the amount of alite in the cement using the obtained cement clinker increases, and the strength development of the cement clinker is further improved. If this ratio is 3.5 or less, the residual amount of free lime is reduced, and the quality of the cement using the resulting cement clinker is further improved.
When the silicic acid ratio exceeds 2.0, it is preferable to prepare the heating object so that the mass ratio represented by the above formula (1) exceeds 2.7 and is 3.3 or less. If this ratio exceeds 2.7, the amount of alite in the cement using the resulting cement clinker increases, and the strength development of the cement clinker is further improved. If this ratio is 3.3 or less, the residual amount of free lime is reduced, and the quality of the cement using the resulting cement clinker is further improved.

  The molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.0 or less, preferably 0.1 to 0.8. When the ratio exceeds 1.0, chlorine remains in the obtained fired product, and thus it becomes difficult to use as a cement clinker. If this ratio is 0.1 or more, the volatilization rate of radioactive cesium becomes larger.

  The heating temperature is 1,400 to 1,550 ° C, preferably 1,420 to 1,500 ° C. If the temperature is lower than 1,400 ° C., a large amount of unreacted CaO is generated, and the quality of the cement clinker is deteriorated. Moreover, the volatility rate of radioactive cesium becomes small. When the temperature exceeds 1,550 ° C., a liquid phase is formed, and thus radioactive cesium is taken into the liquid phase and is less likely to volatilize. Therefore, it becomes difficult to use as a cement clinker.

The content of free lime (free lime) in the cement clinker (calcined product obtained by the method (a)) is preferably 0.2 to from the viewpoint of fluidity and strength development of the cement using the cement clinker. It is 1.5 mass%, More preferably, it is 0.4-1.0 mass%.
The total alkali (Na ₂ O + 0.658 × K ₂ O) content in the cement clinker is preferably 0.75% by mass or less from the viewpoint of suppressing the alkali aggregate reaction of concrete using the cement clinker. More preferably, it is 0.65 mass% or less.
The amount of chlorine in the cement clinker is preferably 1,000 mg / kg or less, more preferably 500 mg / kg or less, and particularly preferably 350 mg or less from the viewpoint of preventing rusting of reinforced concrete using the cement clinker.
In addition, from the viewpoint of improving the fluidity and strength development of cement using a cement clinker, it is preferable to rapidly cool after obtaining a fired product.

(2) Method (b)
In the method (b), the mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ is 1.8 to 2.7, and the silicic acid ratio (SM) is 2.0. The molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.5 or less, and the proportion of P ₂ O ₅ in 100% by mass of the fired product obtained after heating is 0.3% by mass. After preparing a heating target so that it may become more than%, it is the method of heating at 1,250-1,450 degreeC, and obtaining the baked product for using as an earthwork material.
When the mass ratio represented by the above formula (1) is less than 1.8, the volatilization rate of radioactive cesium becomes small, and the concentration of radioactive cesium in the obtained fired product cannot be sufficiently reduced. If the mass ratio exceeds 2.7, the fired product may solidify during storage.

When the silicic acid ratio (SM) is 2.0 or less, a liquid phase is likely to be formed during heating, and radioactive cesium is hardly volatilized by being incorporated into the liquid phase.
The molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.5 or less, preferably 0.2 to 1.0. When the ratio exceeds 1.5, chlorine remains in the obtained fired product, so that it becomes difficult to use as an aggregate for concrete. If this ratio is 0.2 or more, the volatilization rate of radioactive cesium becomes larger.
The proportion of P ₂ O ₅ in 100% by mass of the fired product obtained after heating is 0.3% by mass or more, preferably 0.4-20.0% by mass, more preferably 0.5-15.0% by mass. It is.
CaO, MgO, and the mass ratio represented by SiO ₂ in the formula (1) is 1.8 to 2.7, and the amount of _P 2 _{O 5} in the fired product obtained 0.3 mass% If it is less than the range, there may be a phenomenon (dusting) that the fired product becomes powdery when the fired product is cooled. When the fired product is pulverized, the fired product cannot be used as an earthwork material.

The heating temperature is 1,250 to 1,450 ° C., preferably 1,300 to 1,420 ° C. When the temperature is lower than 1,250 ° C., the volatilization rate of radioactive cesium becomes small. When the temperature exceeds 1450 ° C., a liquid phase is formed, so that radioactive cesium is taken into the liquid phase and hardly volatilizes.
From the viewpoint of dimensional stability of the earthwork material, the content of free lime (free lime) in the earthwork material (baked product obtained by the method (b)) is preferably 1.0% by mass or less, more preferably 0.00%. 5% by mass or less.
Specific applications of earthwork materials include aggregates (coarse and fine aggregates for concrete, aggregates for asphalt), embankment materials, roadbed materials, backfill materials, and gravel for crime prevention. Can be mentioned.

(3) Method (c)
In the method (c), the mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ exceeds 2.2 and is 2.7 or less, and the silicic acid ratio (SM) is 2. Exceeding 0.0, the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.5 or less, and the ratio of P ₂ O ₅ in 100% by mass of the fired product obtained after heating is 0 This is a method for obtaining a fired product for use as an earthwork material by preparing a heating object so as to be less than 3% by mass and then heating at 1,250 to 1,450 ° C.
When the mass ratio represented by the above formula (1) is 2.2 or less, a phenomenon (dusting) occurs when the fired product is pulverized when the fired product is cooled. It cannot be used. If the mass ratio exceeds 2.7, the fired product may solidify during storage.

When the silicic acid ratio (SM) is 2.0 or less, a liquid phase is likely to be formed during heating, and radioactive cesium is hardly volatilized by being incorporated into the liquid phase.
The molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.5 or less, preferably 0.2 to 1.0. When the ratio exceeds 1.5, chlorine remains in the obtained fired product, so that it becomes difficult to use as an aggregate for concrete. If this ratio is 0.2 or more, the volatilization rate of radioactive cesium becomes larger.
The proportion of P ₂ O ₅ in 100% by mass of the fired product obtained after heating is less than 0.3% by mass, preferably 0.2% by mass or less, more preferably 0.1% by mass or less. When the ratio is less than 0.3% by mass and the mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ exceeds 2.2 and is 2.7 or less, the fired product Since the phenomenon (dusting) in which the fired product is powdered when cooling is not generated, the fired product can be used as an earthwork material.

The heating temperature is 1,250 to 1,450 ° C., preferably 1,300 to 1,420 ° C. When the temperature is lower than 1,250 ° C., the volatilization rate of radioactive cesium becomes small. When the temperature exceeds 1,450 ° C., a liquid phase is formed, so that radioactive cesium is taken into the liquid phase and hardly volatilizes.
From the viewpoint of dimensional stability of the earthwork material, the content of free lime (free lime) in the earthwork material (baked product obtained by the method (c)) is preferably 1.0% by mass or less, more preferably 0.00%. 5% by mass or less.

(4) Method (d)
In the method (d), the mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ is 1.8 to 2.2, and the silicic acid ratio (SM) is 2.0. The molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.5 or less, and the proportion of P ₂ O ₅ in 100% by mass of the fired product obtained after heating is 0.3% by mass. In this method, the object to be heated is prepared so as to be less than%, and then heated at 1,250 to 1,450 ° C. to obtain a fired product for use as a cement admixture.
When the mass ratio represented by the above formula (1) is less than 1.8, the volatilization rate of radioactive cesium becomes small, and the concentration of radioactive cesium in the obtained fired product cannot be sufficiently reduced. When the mass ratio exceeds 2.2, the phenomenon that the fired product is powdered when the fired product is cooled (dusting) does not occur. Therefore, in order to use the obtained fired product as a cement admixture, It needs to be crushed.

When the silicic acid ratio (SM) is 2.0 or less, a liquid phase is likely to be formed during heating, and radioactive cesium is hardly volatilized by being incorporated into the liquid phase.
The molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.5 or less, preferably 0.2 to 1.0. When the ratio exceeds 1.5, chlorine remains in the obtained fired product, and thus it becomes difficult to use as a cement admixture. If this ratio is 0.2 or more, the volatilization rate of radioactive cesium becomes larger.

The proportion of P ₂ O ₅ in 100% by mass of the fired product obtained after heating is less than 0.3% by mass, preferably 0.2% by mass or less, more preferably 0.1% by mass or less.
The mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ is 1.8 to 2.2, and the proportion of P ₂ O ₅ in 100% by mass of the fired product obtained after heating is If the amount is less than 0.3% by mass, a phenomenon (dusting) that the fired product is pulverized when the fired product is cooled can be obtained, and a cement admixture can be obtained without adjusting the particle size by grinding. it can.
In addition, the preferable brane specific surface area of a cement admixture is 2,800-4,200 cm < ² > / g.

The heating temperature is 1,250 to 1,450 ° C., preferably 1,300 to 1,420 ° C. When the temperature is lower than 1,250 ° C., the volatilization rate of radioactive cesium becomes small. When the temperature exceeds 1,450 ° C., a liquid phase is formed, so that radioactive cesium is taken into the liquid phase and hardly volatilizes.
By mixing the cement admixture obtained by the method (d) or the method (f) described later with the cement, effects such as neutralization suppression, improvement of long-term strength development, reduction of heat of hydration, etc. can be obtained. .

(5) Method (e)
In the method (e), the mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ is 1.0 to 1.8, and the silicic acid ratio (SM) is 2.3. And the heating object is prepared so that the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.5 or less, and then heated at 1,200 to 1,400 ° C. This is a method for obtaining a fired product for use as an earthwork material.
When the mass ratio represented by the above formula (1) is less than 1.0, the volatilization rate of radioactive cesium becomes small, and the concentration of radioactive cesium in the obtained fired product cannot be sufficiently reduced. Moreover, the amount of elution of heavy metals such as arsenic and fluorine in the fired product may exceed the environmental standard value. When the mass ratio exceeds 1.8, the amount of the CaO source and the like used for the preparation of the heating object and the amount of the fired product obtained after the heating increase. Moreover, the cost of the fuel etc. in heating becomes high.

When the silicic acid ratio (SM) is 2.3 or less, a liquid phase is easily formed during heating, and radioactive cesium is hardly volatilized by being taken into the liquid phase.
The molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.5 or less, preferably 0.2 to 1.0. When the ratio exceeds 1.5, chlorine remains in the obtained fired product, so that it becomes difficult to use as an aggregate for concrete. If this ratio is 0.2 or more, the volatilization rate of radioactive cesium becomes larger.

The heating temperature is 1,200 to 1,400 ° C., preferably 1,250 to 1,350 ° C. When the temperature is lower than 1,200 ° C., the volatilization rate of radioactive cesium becomes small. When the temperature exceeds 1,400 ° C., a liquid phase is formed, so that radioactive cesium is taken into the liquid phase and hardly volatilizes.
From the viewpoint of dimensional stability of the earthwork material, the content of free lime (free lime) in the earthwork material (baked product obtained by the method (e)) is preferably 1.0% by mass or less, more preferably 0.00%. 5% by mass or less.

(6) Method (f)
In the method (f), after the heating object is prepared so that the mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ is 1.0 to 1.8, 1,200 to A fired product is obtained by heating at 1,400 ° C., and then the fired product is pulverized so as to have a Blaine specific surface area of 2,800 to 4,200 cm ² / g for use as a cement admixture. This is a method for obtaining a fired product.
When the mass ratio represented by the above formula (1) is less than 1.0, the volatilization rate of radioactive cesium becomes small, and the concentration of radioactive cesium in the obtained fired product cannot be sufficiently reduced. Moreover, the amount of elution of heavy metals such as arsenic and fluorine in the fired product may exceed the environmental standard value. When the mass ratio exceeds 1.8, the amount of the CaO source and the like used for the preparation of the heating object and the amount of the fired product obtained after the heating increase. Moreover, the cost of the fuel etc. in heating becomes high.

The heating temperature is 1,200 to 1,400 ° C., preferably 1,250 to 1,350 ° C. When the temperature is lower than 1,200 ° C., the volatilization rate of radioactive cesium becomes small. When the temperature exceeds 1,400 ° C., a liquid phase is formed, so that radioactive cesium is taken into the liquid phase and hardly volatilizes.
A cement admixture can be obtained by pulverizing the obtained fired product so that the Blaine specific surface area is 2,800 to 4,200 cm ² / g.

In the methods (a) to (f), the preparation of the heating target is a numerical value required for carrying out each method by the mass ratio represented by the above formula (1) of CaO, MgO, and SiO _{2 as} the processing target. If it is within the range, the component of the processing object is not adjusted, and if it is not within the numerical range required for the implementation of each method, the component of the processing object is adjusted.
In the component adjustment of the processing target, the processing target after the component adjustment (heating target) includes at least one of the CaO source and the MgO source in addition to the processing target, and the processing target after the component adjustment ( At least one of the CaO source and the MgO source so that the mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ of the object to be heated is within the numerical range required for the implementation of each method. It is performed by determining the blending ratio with respect to one kind and the processing object.

Examples of the CaO source include calcium carbonate, limestone, quicklime, slaked lime, limestone, dolomite, and blast furnace slag. Examples of the MgO source include magnesium carbonate, magnesium hydroxide, dolomite, serpentine, and ferronickel alloy slag.
These examples may be used individually by 1 type, and may be used in combination of 2 or more type. Moreover, the processing target object containing CaO or MgO among the processing target objects contaminated with the radioactive cesium mentioned above can also be used as a CaO source or a MgO source. By using the processing object contaminated with radioactive cesium as a CaO source or MgO source, the volume of the processing object contaminated with radioactive cesium can be further reduced.
At least one of the CaO source and the MgO source may be used, but it is preferable to mix only the CaO source from the viewpoint of the volatility of radioactive cesium.
The component adjustment may be performed by mixing the object to be processed and at least one of the CaO source and the MgO source before the heating step. In the heating step, the component to be processed, the CaO source, and the MgO source are mixed. You may carry out by throwing at least any one separately.

Moreover, in adjusting the components of the object to be processed, an SiO ₂ source may be used in addition to the CaO source and the MgO source. The component adjustment using the SiO ₂ source is the same as the method for determining the blending ratio with respect to at least one of the above-described CaO source and MgO source and the above-mentioned treatment object. Examples of the SiO ₂ source include silica, silica sand, and foundry sand. These may be used individually by 1 type and may be used in combination of 2 or more type.

Moreover, in the component adjustment of the object to be treated, in order to promote the volatilization of radioactive cesium and reduce the volume of the fired product to be obtained, the object to be treated (heated object) after the component adjustment should contain chloride. Also good.
Examples of the chloride include calcium chloride (CaCl ₂ ), potassium chloride (KCl), sodium chloride (NaCl), and the like. Of these, calcium chloride is preferred from the viewpoint of promoting chlorination.
The component adjustment may be performed by mixing the object to be processed and chloride before the heating step, or may be performed by separately adding the object to be processed and chloride in the heating step.

In the methods (b) to (d), the selection may be made in accordance with the P ₂ O ₅ content of the processing object as a raw material.
Further, in the method (b), for the purpose of setting the ratio of P ₂ O ₅ in 100% by mass of the fired product obtained after heating to 0.3% by mass or more, the processing target after adjusting the component (heating target) is A P ₂ O ₅ source may be included.
Examples of P ₂ O ₅ sources include phosphate ore; reagents such as calcium phosphate; sewage sludge and sewage sludge incinerated ash; compost such as cow dung, chicken dung, and pig dung; incinerated ash such as rice straw and pasture; Is mentioned. In addition, among the processing objects contaminated with the radioactive cesium described above, the processing objects containing phosphorus (for example, sewage sludge containing radioactive cesium, sewage sludge incineration ash, etc.) should be used as the P ₂ O ₅ source. You can also. By using the processing object contaminated with radioactive cesium as the P ₂ O ₅ source, the volume of the processing object contaminated with radioactive cesium can be further reduced.
The component adjustment may be performed by mixing the object to be processed and the P ₂ O ₅ source before the heating step, and is performed by separately supplying the object to be processed and the P ₂ O ₅ source in the heating step. May be.

The heating time in the heating step is preferably 10 minutes or more, more preferably 30 minutes or more from the viewpoint of obtaining a sufficient volatilization amount of radioactive cesium. The upper limit of the heating time is not particularly limited, but is preferably 180 minutes or less, more preferably 120 minutes or less. When the heating time is 180 minutes or less, the cost becomes low and it is economical.
When the raw material rolls, such as a rotary kiln, the contact rate between the gas and radioactive cesium is increased and the thermal conductivity is improved, so that a high volatilization rate can be obtained in a shorter firing time than the standing conditions. it can.
Examples of the heating means include a rotary kiln, a stoker furnace, and an electric furnace.
Among these, a rotary kiln is preferable because it has high processing efficiency and can easily provide a heating temperature suitable for volatilization of radioactive cesium and a residence time of a heating object.

Moreover, when heavy metals, such as chromium, are contained in the processing object contaminated with radioactive cesium, the elution amount of heavy metals, such as hexavalent chromium, in the obtained fired product may exceed the environmental standard value. In particular, when the mass ratio represented by the above formula (1) regarding CaO, MgO, and SiO ₂ decreases, the elution amount of heavy metals tends to increase.
When such baked products are used as earthwork materials (especially when used as embankment materials, roadbed materials, or backfill materials), heavy metals contained in the baked products are eluted, causing water and soil contamination. Etc. may be caused.
Therefore, in the heating step, heating may be performed in a reducing atmosphere. By heating in a reducing atmosphere, the elution amount of heavy metals such as chromium can be suppressed.

Moreover, in order to make the elution amount of the heavy metals of the obtained baked product below an environmental standard value, you may mix the baked product obtained by the heating process, and an elution inhibitor.
Examples of the dissolution inhibitor include reducing agents such as iron (II) sulfate and adsorbents such as magnesium oxide.
These may be used individually by 1 type and may be used in combination of 2 or more type.

Examples of a method for cooling the fired product obtained after the heating step include a method using an air quenching cooler, a rotary cooler, or the like.
When producing a cement admixture in which the fired product is pulverized during cooling (method (d)), it is preferable to use a rotary cooler. Further, from the viewpoint of generating γ-type C ₂ S (belite) and facilitating pulverization, it is more preferable to reduce the cooling rate. For example, the cooling rate can be slowed by increasing the residence time in the rotary cooler or increasing the filling rate.
When producing a cement clinker (method (a)), it is preferable to perform rapid cooling.

Volatile radioactive cesium in the exhaust gas can be recovered by using a bag filter, a hepa filter, an electrostatic precipitator, a cyclone or the like after being cooled and solidified. Among these, it is preferable to use a bag filter or a hepa filter from the viewpoint of preventing dust from being contained in the exhaust gas finally discharged.
The recovered radioactive cesium is subjected to further volume reduction treatment such as washing with water, adsorption, granulation machine such as briquette machine, compression with pressure molding machine such as press machine, etc., and then into concrete containers etc. Can be sealed and stored. As a result, the waste containing the radioactive substance can be stored in a reduced volume without leaking outside.

In the method for producing a baked product of the present invention, considering the radioactive cesium concentration of the object to be treated and the demand for cement clinker, etc., the use of the obtained baked product can be any one of cement clinker, earthwork material, and cement admixture. Can be determined.
For example, the higher the mass ratio represented by the above formula (1), the higher the removal rate of radioactive cesium can be. Therefore, among a plurality of treatment objects contaminated with radioactive cesium that requires treatment, radioactive cesium. What is necessary is just to determine the use of the baking thing of a process target object with high density | concentration to the cement clinker which can make mass ratio represented by said Formula (1) high in a heating process.
In this case, until a desired amount of the fired product (a fired product for use as a cement clinker) can be obtained, among the plurality of treatment objects, the treatment object having a high radioactive cesium concentration is sequentially ordered. After setting the use to cement clinker and obtaining the desired amount of fired product (fired product for use as cement clinker), compare the remaining processing object (processed object of the fired product to the processing object specified for cement clinker) Thus, the use of the fired product having the same or low radioactive cesium concentration may be determined for one or both of the earthwork material and the cement admixture.
From the viewpoint of reducing the concentration of radioactive cesium in the resulting fired product to the desired concentration when the use of the fired product of the remaining treatment object is defined as one or both of earthwork materials and cement admixtures, You may adjust suitably the mass ratio represented by said Formula (1) with the radioactive cesium density | concentration of a process target object. Specifically, when the radioactive cesium concentration is high, the mass ratio represented by the above formula (1) is increased (for example, 1.8 to 2.7), and when the radioactive cesium concentration is low, the above formula (1). The mass ratio represented by the above may be low (for example, 1.0 to 1.8).

In addition, among the processing objects contaminated with radioactive cesium that needs to be processed, the processing object having a high radioactive cesium concentration (for example, 200,000 Bq / kg or more) is a mass represented by the above formula (1). From the viewpoint that the ratio becomes higher and the removal rate of radioactive cesium can be further increased, the use of the obtained fired product is preferably determined to be a cement clinker.
When a large amount of cement is required as a material for reconstruction in the stricken area, if there are no or few treatment objects with high radioactive cesium concentration, the radioactive cesium concentration is low (for example, 30,000 Bq / kg or more and less than 200,000 Bq / kg) The use of the fired product obtained from the object to be treated may be determined to be a cement clinker.
Among the processing objects contaminated with radioactive cesium that needs to be treated, the use of the calcined material obtained from the processing object having a low radioactive cesium concentration (for example, less than 30,000 Bq / kg) is an earthwork material and cement. What is necessary is just to fix to either of admixtures.

Cement clinker, aggregate (earthwork material), and cement admixture used in concrete were all contaminated with radioactive cesium from the viewpoint of promoting the use of fired products made from treated objects contaminated with radioactive cesium. There is a demand for concrete that is made from a material to be treated. ADVANTAGE OF THE INVENTION According to this invention, the cement clinker, the aggregate (earthwork material), or the cement admixture which uses as a raw material the process target contaminated with radioactive cesium can be obtained easily.
In addition, the obtained fired product may be appropriately pulverized to adjust the particle size according to the application.
The pulverization method is not particularly limited, and may be pulverized by a normal method using, for example, a ball mill or an OK mill.

After obtaining the cement clinker by the method for producing a fired product of the present invention, the cement clinker may be pulverized, and the obtained cement clinker pulverized product and gypsum may be mixed to produce cement.
Examples of gypsum include dihydrate gypsum, hemihydrate gypsum, and anhydrous gypsum. These may be used individually by 1 type and may be used in combination of 2 or more type.
The amount of gypsum is such that the total amount of SO ₃ in the cement is preferably 1.0 to 3.5% by mass. When the amount is 1.0% by mass or more, the usable time before hardening of the concrete (the time during which good fluidity can be maintained) increases. When the amount is 3.5% by mass or less, the strength development of the cement is improved.
The cement clinker may be pulverized and then mixed with gypsum, or the cement clinker and gypsum may be mixed and then simultaneously pulverized. The pulverization is preferably performed so that the Blaine specific surface area of the pulverized cement clinker and gypsum is 2,800 to 4,200 cm ² / g from the viewpoint of fluidity, strength development and cost of cement.
Moreover, you may mix blast furnace slag powder, fly ash, limestone fine powder etc. as a cement admixture as needed.

Cement containing cement clinker, concrete aggregate, and cement admixture obtained by the method for producing a baked product of the present invention from the viewpoint of promoting the use of the baked product made of a processing object contaminated with radioactive cesium You may manufacture concrete using.
In addition, concrete is produced using a cement containing a cement clinker obtained by the method for producing a fired product of the present invention, and an aggregate obtained by classifying waste contaminated with radioactive cesium, etc. Also good.
Furthermore, cement containing cement clinker obtained by the method for producing a fired product of the present invention may be mixed with anhydrous gypsum, blast furnace slag, etc., and used as a solidifying material.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
[Example 1]
Commercially available clay was put into an aqueous cesium chloride solution, stirred for 1 hour, and allowed to stand for 1 day. The solid content was recovered by centrifuging the clay after standing, and then the recovered solid content was poured into water to dissolve water-soluble cesium in water. After dissolution, the water-soluble cesium was removed by collecting the solid content by centrifugation. Subsequently, it grind | pulverized using the ball mill so that a 200 micrometer residue might be 5 mass%. The obtained pulverized product was put into a mixed solution of nitric acid, hydrofluoric acid, and perchloric acid for decomposition, and then the cesium (CS) content of the pulverized product was measured using ICP-MS. As a result, the cesium content of the pulverized product was 202 mg / kg.
Limestone powder and calcium chloride powder are added to the pulverized product, and the mass ratio represented by the above formula (1), the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)), and the silicic acid ratio (S .. M.) were adjusted to the numerical values shown in Table 1.

The pulverized product after adjustment of the ingredients (object to be heated) is heated using a kiln having an inner diameter of 450 mm and a length of 8,340 mm at a heating temperature of 1,450 ° C. and a kiln residence time of 2 hours to obtain a baked product (cement clinker). Obtained.
The obtained fired product was put into a mixed solution of nitric acid, hydrofluoric acid, and perchloric acid and decomposed, and then the cesium content of the fired product was measured using ICP-MS. 01 mg / kg) or less.
Further, after the fired product was decomposed with nitric acid, the Cl content of the fired product was measured using a potentiometric titration method.
Moreover, after extracting the free lime of a baked product with ethylene glycol, the free lime content rate of the baked product was measured by the method of titrating an extract with an ammonium acetate-ethanol solution.

  The removal rate of cesium calculated from the cesium content of the pulverized product and the cesium content of the fired product was 99.995% by mass or more. The removal rate means that when a processing object having a radioactive cesium concentration of 2 million Bq / kg is heated under the same conditions, the radioactive cesium concentration of the fired product after heating becomes 100 Bq / kg or less. .

After adding a gypsum by-product from a coal-fired power plant in which the amount of SO ₃ in the cement is 2.0% by mass to the fired product (cement clinker), using a ball mill, the brain specific surface area is 3, Cement was obtained by pulverizing to 300 cm ² / g. With respect to the obtained cement, the mortar compressive strength and setting time at 3 days, 7 days and 28 days were measured by a method based on “JIS R 5201”. As a result, the mortar compressive strength was 3 days of age: 34.2 N / mm ² , 7 days of age: 46.7 N / mm ² , 28 days of age: 59.5 N / mm ² , and the setting time was First start: 1 hour 27 minutes, end: 2 hours 12 minutes.

[Example 2]
Limestone powder, calcium chloride powder, and lime phosphate powder are added to the pulverized product, and the mass ratio represented by the above formula (1), the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)), silica The components were adjusted so that the acid ratio (SM) and the proportion of P ₂ O ₅ in 100% by mass of the fired product obtained after heating were the values shown in Table 1, and the heating temperature was 1,380 ° C. A fired product (aggregate) was obtained in the same manner as in Example 1 except that.
In the same manner as in Example 1, the cesium content, Cl content, and free lime content of the fired product were measured. In addition, the free lime content rate was below the detection limit value.
The removal rate of cesium calculated from the cesium content of the pulverized product and the cesium content of the fired product was 99.960% by mass. The removal rate means that when a processing object having a radioactive cesium concentration of 200,000 Bq / kg is heated under the same conditions, the radioactive cesium concentration of the fired product after heating becomes 79 Bq / kg.

The unit volume mass of the fired product was measured according to “JIS A 1104”. As a result, the unit actual mass was 1.56 kg / liter.
The fired product was classified by a sieve having an opening of 5 mm, and the water absorption and density of the fired product remaining on the sieve having an opening of 5 mm were measured in accordance with “JIS A 1110”. As a result, the water absorption was 1.68%, the absolute dry density was 2.72 cm ³ / g, and the surface dry density was 2.77 cm ³ / g.

[Example 3]
Limestone powder and calcium chloride powder are added to the pulverized product, and the mass ratio represented by the above formula (1), the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)), and the silicic acid ratio (S M.) was adjusted so that the values shown in Table 1 were obtained, and a fired product (cement admixture) was obtained in the same manner as in Example 1 except that the heating temperature was 1,380 ° C. The ratio of _P 2 _{O 5} of the obtained baked product in 100% by mass was 0.1 wt%.
The obtained fired product was pulverized upon cooling to become a powder having a Blaine specific surface area of 2,800 cm ² / g.
In the same manner as in Example 1, the cesium content, Cl content, and free lime content of the fired product were measured.
The removal rate of cesium calculated from the cesium content of the pulverized product and the cesium content of the fired product was 99.955% by mass. The removal rate means that when a processing object having a radioactive cesium concentration of 200,000 Bq / kg is heated under the same conditions, the radioactive cesium concentration of the fired product after heating becomes 89 Bq / kg.

From Examples 1 to 3, it can be seen that the higher the mass ratio represented by the above formula (1), the higher the removal rate of radioactive cesium.
According to the heating method of Example 1, the radioactive cesium density | concentration was fully reduced (100 Bq / kg) according to the heating method of Example 1 about the process target object (for example, 2 million Bq / kg) with a high density | concentration of radioactive cesium. Below) Cement clinker can be obtained. Moreover, according to the heating method of Example 2 for a processing object having a low radioactive cesium concentration (for example, 200,000 Bq / kg), an aggregate in which the radioactive cesium concentration is sufficiently reduced (79 Bq / kg) is obtained. be able to. Moreover, according to the heating method of Example 3, the radioactive cesium concentration was sufficiently reduced (89 Bq) without performing pulverization on the object to be processed (for example, 200,000 Bq / kg) having a low concentration of radioactive cesium. / Kg) A cement admixture can be obtained.
Note that, depending on the use of the fired product, a fired product having a radioactive cesium concentration of 100 Bq / kg or less is not always required. For example, when the fired product is covered with a shield having a thickness of about 30 cm after being used for applications such as earthwork materials, it can be used because there is little adverse effect even if the radioactive cesium concentration in the fired product is about 300 Bq / kg. there is a possibility. For this reason, what is necessary is just to define the use of a baked product, detailed component adjustment in a heating process, heating conditions, etc. according to the upper limit of the radioactive cesium density | concentration in the baked product calculated | required.
In this way, various calcined products (cement clinker, earthwork materials, cement admixtures) whose radiocesium concentration has been sufficiently reduced by performing appropriate heat treatment according to the size of the radioactive cesium concentration and the use of the calcined product Can be obtained.

Claims (8)

A method for producing a fired product having a reduced concentration of radioactive cesium by heating a processing object contaminated with radioactive cesium,
A cesium concentration measuring step for measuring the concentration of radioactive cesium in the processing object contaminated with the radioactive cesium;
The processing object whose radioactive cesium concentration has been measured in the cesium concentration measurement step is not adjusted or component-adjusted to obtain a heating object, and then the heating object is heated to obtain the processing object. A heating step of volatilizing radioactive cesium therein to obtain a fired product,
After the cesium concentration measurement step, the use of the fired product is determined by selecting from a plurality of uses including at least the use of cement clinker and the use of earthwork materials, based on the radioactive cesium concentration,
When the use of the fired product is determined as a cement clinker, in the heating step, the heating object is set so that the mass ratio represented by the following formula (1) of CaO, MgO, and SiO ₂ exceeds 2.7. After preparing, to obtain a fired product for use as the cement clinker,
When the use of the fired product is defined as an earthwork material, in the heating step, the mass ratio represented by the following formula (1) of CaO, MgO, and SiO ₂ is 1.0 to 2.7. A method for producing a fired product, comprising: preparing a fired product for use as the earthwork material after preparing the heating object.
Mass ratio = ((CaO + 1.39 × MgO) / SiO ₂ ) (1)
(In the formula, CaO, MgO, and SiO ₂ represent a mass in terms of oxide of calcium, a mass in terms of oxide of magnesium, and a mass in terms of oxide of silicon, respectively.)   When the radiocesium concentration is equal to or higher than a specific value, the application is selected from the plurality of uses. The cement clinker is used for the application, and when the radiocesium concentration is lower than a specific value, The method for producing a fired product according to claim 1, wherein the method is defined for the use of earthwork materials. As a plurality of uses of the fired product, in addition to the use of the cement clinker and the use of earthwork materials, the use of a cement admixture is included, and when the use of the fired product is defined as a cement admixture, the heating In the process, after preparing the heating object so that the mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ is 1.0 to 2.2, the heating object is heated, and the cement The method for producing a fired product according to claim 1, wherein a fired product for use as an admixture is obtained.   When the radiocesium concentration is equal to or higher than a specific value, the application is selected from the plurality of uses. The cement clinker is used for the application, and when the radiocesium concentration is lower than a specific value, The method for producing a fired product according to claim 3, wherein the method is determined for one or both of earthwork materials and cement admixtures. After the cesium concentration measurement step, when the radioactive cesium concentration is 200,000 Bq / kg or more, in the heating step, the method (a) below is selected,
When the radioactive cesium concentration is 30,000 Bq / kg or more and less than 200,000 Bq / kg, in the heating step, any one of the following methods (a) to (d) is selected,
When the radioactive cesium concentration is less than 30,000 Bq / kg, in the heating step, by selecting any one of the following methods (b) to (f):
The method for producing a fired product according to claim 3 or 4, wherein the use of the fired product is defined as any one of cement clinker, earthwork material, and cement admixture.
(A) The mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ exceeds 2.7, the silicic acid ratio (SM) exceeds 1.3, and chlorine and cesium In order to use as a cement clinker after preparing the heating object so that the molar ratio (Cl / (Cs + K)) to potassium is 1.0 or less, and then heating at 1,400 to 1,550 ° C. (B) The mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ is 1.8 to 2.7, and the silicic acid ratio (SM) is 2. Exceeding 0.0, the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.5 or less, and the ratio of P ₂ O ₅ in 100% by mass of the fired product obtained after heating is 0 After preparing the heating object so as to be 3% by mass or more, 1,250-1,450 In heating, the method of obtaining a calcined product for use as earth moving material (c) CaO, MgO, and mass ratio represented by SiO ₂ in the formula (1) exceeds 2.2, 2.7 or less Yes, the silicic acid ratio (SM) exceeds 2.0, the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.5 or less, and the fired product obtained after heating To prepare the heating object so that the ratio of P ₂ O ₅ in 100% by mass is less than 0.3% by mass, and then heat at 1,250-1450 ° C. for use as an earthwork material (D) The mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ is 1.8 to 2.2, and the silicic acid ratio (SM) is 2. More than 0.0 and the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.5 or less And, as the proportion of _P 2 _{O 5} of calcined product in 100% by mass obtained after heating it is less than 0.3 wt%, after preparation of the heating object, heated at 1,250～1,450 ° C. And (e) a mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ is 1.0 to 1.8, and silicic acid. After preparing the heating object so that the rate (SM) exceeds 2.3 and the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is 1.5 or less Method for obtaining a fired product for use as an earthwork material by heating at 1,200 to 1,400 ° C. (f) The mass ratio represented by the above formula (1) of CaO, MgO, and SiO ₂ is 1. After preparing the heating object so as to be 0 to 1.8, 1,200 to 1,4 A fired product for use as a cement admixture by heating at 00 ° C. to obtain a fired product, and then pulverizing the fired product to have a Blaine specific surface area of 2,800-4,200 cm ² / g. How to get   In the method (a), when the silicic acid ratio (SM) exceeds 1.3 and is 1.6 or less, the mass ratio represented by the above formula (1) is 3.0 to 3.7. Yes, when the silicic acid ratio (SM) exceeds 1.6 and is 2.0 or less, the mass ratio represented by the above formula (1) is 2.8 to 3.5, and the silicic acid ratio When (SM) exceeds 2.0, the heating object is prepared so that the mass ratio represented by the formula (1) exceeds 2.7 and is 3.3 or less. Item 6. A method for producing a fired product according to Item 5.   In the heating step, the heating target includes at least one of a CaO source and an MgO source in addition to the processing target, and at least one of the types of the CaO source and the MgO source and the processing target. The manufacturing method of the baked product of any one of Claims 1-6 which prepares the said heating target object by defining the mixture ratio with respect to.   A cement clinker is obtained by the method for producing a fired product according to any one of claims 1 to 7, the cement clinker is pulverized, and the obtained cement clinker pulverized product and gypsum are mixed to obtain cement. , Manufacturing method of cement.