JP2022038828A - Waste - Google Patents

Abstract

To provide waste that has sufficient barrier properties to a radioactive element or a metal element and prevents these elements from eluting even when exposed to water and a method for producing the same.SOLUTION: The present invention discloses: amorphous waste that includes a porous body predominantly composed of an aluminosilicate with an Al/Si molar ratio of 0.3-1 and a radioactive element or a metal element immobilized to the porous body, where the portion of the porous body having the radioactive element or the metal element immobilized thereto has a density of 2.2 g/cm3 or more; and a method for producing the same.SELECTED DRAWING: None

Description

The present invention relates to a waste body. The present invention particularly relates to low-level radioactive waste and toxic substances whose emissions are regulated, particularly wastes on which solutions, dry residues, incinerated ash, sludge, ion exchange resins and the like are immobilized, and methods for producing the same. Regarding.

Waste liquid, sludge, and low-level radioactive waste of ion-exchange resin generated from operating nuclear power plants are removed from the solvent, incinerated, melted and reduced in volume, and then kneaded and solidified with cement and asphalt in a drum can to form waste. After that, after storing it in the storage facility in the power plant for a certain period of time, it is supposed to be buried in shallow ground or disposed of at medium depth depending on the radioactivity level. After a management period of 300 to 400 years after the burial disposal, the disposal site can be used for general land use.

The disposal of waste with relatively low radioactive levels in shallow ground has been commercialized, and disposal facilities equivalent to 610,000 drums of 200L drums (six low-level radioactive waste burial centers) are in operation. At the end of 2016, about 680,000 units were stored in the nuclear power plant, which is less than the storage capacity of about 960,000 units, but low-level radioactive waste will increase due to the restart of the power plant in the future. Therefore, the storage capacity will be tight. In addition, as of November 2018, the decommissioning of 23 nuclear reactors has been decided, and a large amount of unreducable low-level radioactive waste such as metal structural materials and concrete will be generated. Therefore, the capacity of the current buried disposal facility is expected to expand. The transfer of radioactive waste elements from the buried disposal facility to the environment is designed to be restrained by the triple barriers of the waste, the cement-based filler around the waste, and the soil around the filler. The amount of nuclides that can be disposed of is fixed for the entire burial facility, and the partition coefficient is set for each nuclide. If the elution inhibitory property of radioactive waste from the waste itself, that is, the barrier property is high, the barrier property of the cement-based filler and the surrounding soil may be low, so that the burial facility as a whole has a margin. Therefore, it is desirable that the barrier property of the waste itself is high.

Blast furnace cement and Portland cement, which are approved as solidifying materials for radioactive waste, harden by Ca hydration reaction when kneaded with water and become solid. Cement is used as a solidifying material because of its low price and low cost of solidifying equipment, which makes it safe during storage and transportation. However, the cement waste tends to elute alkali metals when exposed to water, and its cesium confinement performance is particularly low. Therefore, the barrier property of the waste itself is not expected, and the conventional burial facility is designed to suppress the transfer of radioactive materials to the environment by the barrier property of the filler and soil around the cement waste. There is.

There is known a technique for improving the barrier property by heating a waste body composed of boron and cement and performing vitrification following the porosification by dehydration (see, for example, Patent Document 1). In this technology, boric acid contained in the waste liquid discharged from the primary cooling water of a pressurized water reactor is insolubilized by adding calcium, and then heated at 700 to 1000 ° C. together with the cement component, and Na _{2OB 2} O ₃ -It is characterized by using SiO ₂ type glass (borosilicate glass).

By kneading the ferrocyanide used for fixing Cs with the geopolymer and heating it at 400 to 500 ° C, which is higher than the decomposition temperature of the organic matter, the formation of highly toxic cyanide is prevented and the Cs is inside the geopolymer. (For example, see Patent Document 2). Geopolymer is a porous aluminosilicate formed by a dehydration condensation reaction between water glass and a dissolving component of an alkaline active filler containing a silica component such as metacaolin and blast furnace slag, and has high heat resistance unlike cement.

Japanese Unexamined Patent Publication No. 60-257398 Japanese Patent Application Laid-Open No. 2015-138000

With respect to the technique disclosed in Patent Document 1, boric acid generally reacts with calcium, which is the main component of cement, to become insoluble CaB ₂ O ₄ , which lowers the calcium concentration and thus hinders the solidification of cement. Therefore, in this method, it is necessary to add extra calcium, and if the waste liquid does not contain boric acid, it is necessary to further add boric acid. By adding boric acid, CsBO ₂ (melting point = 716 ° C.) is generated from Cs in the waste liquid, so that Cs may volatilize during firing. Further, in the technique disclosed in Patent Document 2, the Cs elution rate from the heated waste is 2 to 5% when exposed to water, and it is necessary to further reduce the elution rate.

Metallic structural materials generated by the decommissioning of nuclear power plants, waste liquids and sludge generated during operation, incinerator waste and cement waste solidified with ion exchange resin have the problem of low barrier properties against cations. be. In addition, it may be necessary to contain radioactive elements and toxic or highly dangerous elements with high barrier properties. It has sufficient barrier properties against cationic radioactive elements such as Cs ions or metal elements such as emission-controlled metal elements, and radioactive or toxic substances are eluted even when exposed to water. No waste is required.

As a result of diligent studies, the present inventors have found that the non-crystalline waste obtained by heating a porous body in which a radioactive element or a metal element is immobilized on a geopolymer at a high temperature dissolves the radioactive element or the metal element. We have found that the above can be suppressed to an extremely low level, and have completed the present invention. That is, according to one embodiment, the present invention is a waste body, which is a porous body containing aluminosilicate having an Al / Si molar ratio of 0.3 to 1 as a main component and fixed to the porous body. The present invention relates to an amorphous waste body containing an amorphized radioactive element or a metal element and having a density of a porous body portion on which the radioactive element or the metal element is immobilized is 2.2 g / cm ³ or more.

It is preferable that the waste is a heated waste.

It is preferable that the waste contains 80% by weight or more of an amorphous component.

According to another embodiment, the present invention is a coated waste, and the waste according to any one of the above, and a cement, mortar, geopolymer, which covers the periphery of the waste. With respect to a coating waste containing one or more coatings selected from asphalt, resin, or metal.

According to another embodiment of the present invention, in a metal container, the waste according to any one of the above items and one or more selected from cement, mortar, geopolymer, asphalt, resin, or metal. The present invention relates to a container-filled waste body filled with a covering body.

According to another embodiment, the present invention is a method for producing a waste product.
A step of preparing a mixture containing an alkali silicate, an alkaline active filler, water, and a radioactive element or a metal element.
The step of curing the mixture to obtain a solid substance, and
A step of heating the solid matter at a first heating temperature of 100 to 250 ° C.
The present invention relates to a method for producing a waste product, which comprises a step of further heating the heated solid matter at a second heating temperature of 800 to 1000 ° C.

In the method for producing the waste, it is preferable to raise the temperature from the first heating temperature to the second heating temperature within 8 hours.

In the method for producing the waste, it is preferable that the alkaline active filler contains 80% by weight or more of an amorphous component.

The present invention relates to a waste product produced by the production method according to any one of the above, according to another embodiment.

The waste according to the present invention is volume-shrinked and densified by heating for a short time, and can suppress volatilization of radioactive elements and metal elements, for example, Cs due to heating. The densified waste has almost no elution of radioactive elements or metal elements when exposed to water, and there is a margin in the design of the buried disposal facility, so that the disposal cost can be reduced.

Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the embodiments described below.

[First Embodiment: Waste and its manufacturing method]
According to the first embodiment, the present invention relates to a waste body and a method for producing the same. The waste according to the present embodiment contains a porous body containing aluminosilicate having an Al / Si molar ratio of 0.3 to 1 as a main component, and a radioactive element or a metal element immobilized on the porous body. The density of the porous body portion on which the radioactive element or the metal element is immobilized is 2.2 g / cm ³ or more.

The porous body containing aluminosilicate as a main component is also called a geopolymer, and is mainly a polymerization product of water, an alkali silicate, and an alkaline active filler. The production method will be described in detail later, but when an alkaline active filler and an alkali silicate are mixed, silicon and aluminum are dissolved as silicic acid and tetrahydroxoaluminic acid, and dehydration condensation is performed between the hydroxyl groups to polymerize. When the polymerization progresses sufficiently, the strength develops and the solidified body becomes porous. The waste according to the present embodiment contains aluminosilicate in a state of being a porous solidified body (porous body), and a radioactive element or a metal element is immobilized on the porous body.

Radioactive or metallic elements contained in the waste are toxic or dangerous and are desirable to be disposed of by a predetermined method. For example, it may be an element that should be disposed of by a predetermined method based on the law, and generally may be a radioactive element or a non-radioactive metal element whose emission is regulated. The radioactive element may be an element containing a radionuclide, and may be either a metallic or non-metallic radioactive element. Examples of the radioactive element include H-3, C-14, Cl-36, Ca-41, Co-60, Ni-63, Sr-90, Cs-137, Eu-152, and Eu-154. , Not limited to them. Examples of metal elements other than radioactive metal elements include highly toxic Cd, Pb, Hg, Cr, As, Sn, Be, and Al. However, metal elements other than these, particularly heavy metal elements, may be used for immobilization on a porous body and discarded, and in the present invention, by immobilizing on a porous body made of a geopolymer, it can be safely disposed of. can. Hereinafter, a radioactive element or a metal element that is immobilized on a waste body and should be discarded may be referred to as an element to be discarded. The content of the radioactive element or the metal element in the waste is preferably about 0.1% by weight or less when the total mass of the waste is 100%. However, as long as the compressive strength of the waste does not become 1.47 MPa or less, there is no problem even if 0.1% by weight or more of radioactive elements and metal elements are contained. In addition to the above radioactive elements and metal elements, the waste may contain other metal elements and non-metal elements derived from the waste.

In addition to the above components, the waste according to the present embodiment may contain waste liquid, components that generate waste liquid, elements to be discarded and compounds, filter sludge, ion exchange resin, etc., which are difficult to separate from the elements to be discarded. .. Of these, filter sludge containing cellulose as a main component and ion exchange resin containing an organic polymer compound as a main component are usually contained in the waste in a carbonized state due to the production method described later. .. In addition, elements other than the elements to be discarded, inorganic compounds, etc. may be included.

In the waste body according to the present embodiment, the density of the porous body portion on which the radioactive element or the metal element is immobilized is 2.2 g / cm ³ or more. If it is 2.2 g / cm ³ or more, the upper limit is not particularly limited, but it is usually 2.2 g / cm ³ or more and about 3 g / cm ³ or less. Here, the "density of the porous body portion on which the radioactive element or the metal element is immobilized" means the density in the portion that does not contain the carbonized organic component that can be contained in the waste body. The density of the porous body portion can be measured by separating the portions that do not constitute the porous body. For example, in the waste containing the ion exchange resin, the resin shape is maintained even after heating, so that the waste can be crushed in a mortar and the ion exchange resin and the porous portion can be separated by a sieve. The density of the separated porous portion can be measured by the Archimedes method. In the case of waste containing organic matter such as filter sludge, the organic matter is carbonized by heating and the waste is partially blackened, but the carbonized (blackened) part is removed from the crushed waste under microscopic observation. , It can be carried out by measuring the density of the remaining porous body portion in the same manner.

The waste according to the present embodiment is a waste heated at a high temperature of 800 to 1000 ° C. This waste is amorphous. In the present invention, the fact that the waste is amorphous means that it contains 80% by weight or more of an amorphous component when measured by an X-ray crystal diffraction method. The waste according to the present invention more preferably contains 85% by weight or more of an amorphous component, more preferably 90% by weight or more of an amorphous component, and further preferably 95% by weight or more of an amorphous component. ing.

The waste according to the present invention is a solid material that has been heated and solidified, and may have a predetermined shape such as a plate shape, a rod shape, a prismatic shape (block shape), or a columnar shape. The size thereof is not particularly limited, but the characteristic length may be about 2 to 90 cm. In the present specification, the characteristic length means the length of the longest side constituting the waste body.

Next, the waste according to the present embodiment will be described from the viewpoint of the manufacturing method. The manufacturing method according to this embodiment includes the following steps.
(1) A step of preparing a mixture containing an alkali silicate, an alkaline active filler, water, and a radioactive element or a metal element (2) A step of curing the mixture to obtain a solid (3) A step of obtaining the solid , Step of heating at the first heating temperature of 100 to 200 ° C. (4) Step of further heating the heated solid substance at the second heating temperature of 800 to 1000 ° C.

(1) Step of preparing a mixture The first step is a step of mixing and kneading a raw material of a porous body constituting a waste body and an element to be discarded to prepare a mixture. The material of the porous body (geopolymer) constituting the waste body contains water, an alkali silicate, and an alkaline active filler. As the alkali silicate, an aqueous solution of sodium silicate (water glass) can be used. As the alkaline active filler, for example, a powder containing metakaolin as a main component can be used, and metacaolin, fly ash, blast furnace slag, or a mixture thereof may be used, and anhydrous sodium metasilicate or silica powder may be further added thereto. good. The alkaline active filler is preferably amorphous. Here, the fact that the alkaline active filler is amorphous means that the amorphous component in the alkaline active filler is 80% by weight or more. The proportion of the amorphous component can be obtained by the X-ray crystal diffraction method. The amorphous component in the alkaline active filler is more preferably 85% by weight or more, and further preferably 90% by weight or more. Pure water can be used as the water. In addition to these, sodium hydroxide or potassium hydroxide may be added as an optional component for adjusting the dissolution rate and the polymerization rate of the material.

The mixing ratio of the alkali silicate and the alkaline active filler can be appropriately determined so that the Al / Si molar ratio is 0.3 to 1, preferably 0.5 to 0.9. Also, water can be added in an amount that adjusts the concentration of the mixture.

Radioactive or metallic elements are the elements to be discarded as detailed above. Radioactive elements or metal elements are porous in the state of ions dissolved in waste liquid, the state of powdered solids forming compounds, the state of dry residues, and the state of being attached to solids such as incineration ash, filter sludge, and ion exchange resins. Can be mixed with body materials.

As a more specific procedure, water glass, pure water, and sodium hydroxide or potassium hydroxide, if used, are placed in a container and mixed in advance. Then, the alkaline active filler is added to this mixture and mixed. By this operation, the alkaline active filler is mixed with water glass to form a slurry. The liquid or solid containing the element to be discarded may be mixed in a container before the alkaline active filler is added, or may be added to the container and mixed after the alkaline active filler is sufficiently dispersed. The container is used in this step to uniformly knead the raw material and, in some cases, can be used continuously in the next step to retain its shape until it becomes a solid. The container preferably has a shape without corners, such as a cylindrical shape, for the purpose of uniformly kneading, and for example, a metal, plastic, or ceramic container can be used. When it is continuously used in the next step and used as a waste mold, it is preferably suitable for the shape and size of the waste to be manufactured.

By mixing these materials and preparing a mixture, the curing reaction starts at room temperature and normal pressure. The curing start time is inversely proportional to the amount of water and proportional to the amount of alkali, but it cures in several to a dozen hours. The curing start time is the time from the start of kneading of the raw materials to the start of solidification. The amount of alkali here means the amount of sodium hydroxide or potassium hydroxide that can be used as an optional component. When making a 200L drum size waste, it may take time to knead, so increase the water content or reduce the amount of sodium hydroxide or potassium hydroxide to adjust the curing time as appropriate. Can be adjusted.

(2) Step of obtaining a solid substance In the second step, the mixture obtained in the first step is cured to obtain a solid substance. The second step may include a curing step and a drying step in more detail, and these are collectively referred to as a step of curing to obtain a solid substance in the present invention.

In the curing step, after the start of curing of the mixture obtained in the first step, the mixture is cured in an environment where the temperature and humidity are constant. When curing in a container different from that in the first step, the slurry can be cast into a container for curing before the viscosity of the slurry of the mixture becomes high. When the waste after production has a shape with corners such as a prismatic shape, it is preferable to separate the container for kneading in the first step and the container for shape retention in the second step. There is. Normally, the curing period is about 28 days, but it may be longer than 28 days, and may be about 28 to 35 days. Alternatively, it may be short as long as the strength is high, and it may be about 20 to 28 days. If the mixture (slurry) before solidification is cast and then solidified, it may be demolded and then cured. As for the curing environment, it is preferable to prepare the composition of the raw materials so that the humidity is maintained at a relatively high humidity and the curing environment is cured at room temperature. The term "high humidity" as used herein means an environment in which the relative humidity is 90% to saturated humidity. Curing at high humidity can prevent the surface of the mixture being cured from drying out and being prone to cracking. However, if cracking is not a problem, it may not be necessary to set high humidity conditions.

After the curing process is completed, the process of drying in a lower humidity environment than the curing environment is further included. For example, in the case of curing in a saturated humidity environment, it is preferable that the relative humidity is, for example, 80 to 85%, 50 to 60%, 50% or less, and then dried. This is because cracks are unlikely to occur. Since it takes a long time to dry a solid substance of the size of a drum, it takes a short time to prepare a large number of small homogeneous wastes and dry each of them. For example, when the characteristic length is about 3 cm, each step can be about 48 to 72 hours.

(3) Step of heating at the first heating temperature of 100 to 200 ° C. In the third step, the solid matter obtained in the second step is taken out from the container as needed and at the first heating temperature of 100 to 250 ° C. Heat. The step of heating at the first heating temperature may be performed in two steps, and in this case, a step of heating at 100 to 120 ° C. and a step of heating at 200 to 250 ° C. may be sequentially performed. Since the solid material has pores and may not be sufficiently dried at 100 to 120 ° C., it is preferable to further perform a step of heating at 200 to 250 ° C. Drying may usually be carried out in a heating furnace in the atmosphere or in a heating furnace in an inert atmosphere.

As a more specific example, the solid substance can be put into a heating furnace at room temperature, heated from room temperature to 100 to 120 ° C. in about 1 to 4 hours, and maintained for about 4 to 24 hours. Then, the temperature can be raised from 100 to 120 ° C. to 200 to 250 ° C. in about 1 to 4 hours and maintained for 4 to 24 hours. However, the temperature rise and maintenance time is an example, and the present invention is not limited to such temperature rise and maintenance time.

(4) Step of further heating at a second heating temperature of 800 to 1000 ° C. After the completion of heating in the third step, the solid material is kept in the furnace and the temperature is not lowered from the first heating temperature. In the four steps, the temperature is further raised to a heating temperature of 800 to 1000 ° C. The heating time from the first heating temperature to the second heating temperature is preferably about 8 hours or less, more preferably 4 hours or less, and most preferably about 2 hours. If the waste does not crack, or if it does, it may be rapidly heated for 2 hours or less, for example, about 1 hour. Further, if there is no problem such as volatilization of the element to be discarded, the heating time from the first heating temperature to the second heating temperature may be longer than 8 hours. If the second heating temperature is lower than 800 ° C., the shrinkage may be insufficient during cooling and the density may not increase, and if the temperature exceeds 1000 ° C., the solid matter may be melted. It is preferable to heat the temperature to a predetermined second heating temperature in the range of 800 to 1000 ° C. and then remove the heat in the heating furnace. In particular, in the case of Cs or the like, in which the radioactive element or the metal element is an element that easily volatilizes at the second heating temperature, after the temperature is raised to the second heating temperature, the heating is performed without maintaining the second heating temperature. It is preferable to stop. If there is no problem such as volatilization of the element to be discarded, the temperature can be raised to the second heating temperature and then maintained at the second heating temperature for about 1 to 2 hours.

By performing the above operations of the first to fourth steps and returning to room temperature, the volume is reduced by nearly 50%, and the density, which is about 1.5 g / cm ³ before the drying step, is 2.2 g / cm. Wastes with a high density of ³ or more can be obtained. The elemental elution from the waste body, which has been densified by firing in this way, is below the detection limit, and the leaching of aluminum and silicon, which are the main components of the porous body, is 10 to 1000 times smaller than before firing, and is discarded. Deterioration of the porous body that constitutes the body is unlikely to occur. Further, the concentration of the radioactive element or the metal element does not change before and after heating, and it can be said that the waste body can be produced without volatilizing the radioactive element or the metal element according to the production method according to the present embodiment.

[Second Embodiment: Processed Waste]
According to the second embodiment, the present invention relates to a waste obtained by further processing the waste according to the first embodiment. More specifically, the waste according to the first embodiment includes one or more coatings selected from cement, mortar, geopolymer, asphalt, resin, or metal, which wrap around the waste. Regarding coated waste.

As the covering body according to the present embodiment, cement, mortar, geopolymer, asphalt, resin, or metal usually used for treating radioactive waste or the like can be used. The geopolymer may have the same composition as described as the material of the porous body of the first embodiment. As the cement, for example, Portland cement or the like can be used. As the resin, an unsaturated polyester resin, an epoxy resin, a thermoplastic such as polyethylene, or the like can be used. As the metal, iron-based metals such as carbon steel and stainless steel can be used. The covering body may be used in combination of a plurality of types composed of different materials, and may be provided in a configuration including two layers, three layers, or a plurality of layers for the waste body. The covering body preferably covers the entire surface of the waste body according to the first embodiment. The coating thickness of the covering is not particularly limited, and may be, for example, 0.1 to 1 cm, although it depends on the shape and dimensions of the waste.

The preferred coating can be selected depending on the type of radioactive element or metal element immobilized on the waste body and what kind of compound these elements are immobilized on. For example, cement is effective in coating waste containing radioactive or metallic elements immobilized as part of anions or anionic compounds. Anionic compounds may include, but are not limited to, niobate ions (Nb (OH) _6- ⁾ and carbonic acid (CO _3-2- ) containing the radionuclide C ^- 14. Geopolymers are also effective in coating waste containing elements (including radioactive elements) that exist in the form of cations or cationic compounds. For example, the cationic compound may be an ammonium cation in which one or more hydrogen atoms of NH ₄₊ are substituted with an organic group containing C ^- 14, but the compound is not limited to a specific compound.

The production of coated waste differs depending on the type of coating. For example, in the case of cement, a mold is placed around the waste and filled in the gaps, and in the case of resin, the surface of the waste. A coated body can be manufactured by applying to.

As a modification of the present embodiment, the metal container is filled with the waste according to the first embodiment and one or more coverings selected from cement, mortar, geopolymer, asphalt, resin, or metal. , Container filling waste.

In the modified form, typically, a relatively large metal container such as a 200 L drum can and a first embodiment formed smaller than the metal container, for example, having a characteristic length of about 10 cm or less. Waste can be used. Then, a container-filled waste can be produced by arranging a plurality of wastes in the container and filling the voids with the covering body exemplified above.

The coated waste according to the present embodiment and the container-filled waste according to the modified form can prevent elution and leaching from the surface of the waste by further covering the surface of the waste.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples do not limit the present invention.

[Example 1] Barrier property of simulated waste using Sobueclay metakaolin Water glass whose water content has been adjusted as an alkali silicate (42 g of Fuji Chemical JIS No. 1 mixed with 16 g of water and 0.5 g of sodium hydroxide) Was uniformly mixed. 0.14 g of cesium chloride was added thereto as simulated waste, and the mixture was further mixed. Metakaolin powder (manufactured by Sobueclay, 48 g) was added thereto, and the mixture was stirred for 5 minutes to obtain a uniform solution. The amorphous component of the metakaolin powder used was about 98% by weight. The cesium concentration calculated from the charging ratio was 0.1% by weight. The cesium concentration referred to here is the percentage of the weight of cesium with respect to the portion obtained by excluding the weight of water contained in the water glass and the weight of water to be added from the weight of the raw material. Next, a fixed amount of the solution was filled in a square plastic container with a lid (31 mm x 31 mm x 10 mm) and sealed with a parafilm. After curing for 28 days, the package was opened and dried in an 85% RH environment for 72 hours and in a 55% RH environment for 72 hours.

After measuring the side length and thickness with a micrometer, the dried plate sample is heated to 200 ° C from room temperature for 2 hours (heating by the first heating temperature) in an atmospheric heating furnace, and then rises to 1000 ° C in 2 hours. The heating was stopped by warming (heating by the second heating temperature), and the heat was removed as it was to room temperature. After heat removal, the side length and thickness were measured. The volume shrinkage was 46% due to the volume change before and after heating. The density was 2.3 g / cm ³ . Further, another plate sample before heating was pulverized with a planetary ball mill (P-6, zirconia pot, Fritsch Japan), and after acid dissolution, the Cs concentration was confirmed by ICP-MS and found to be 0.096% by weight. .. The plate sample after heating was also crushed in the same manner, and the Cs concentration was confirmed to be 0.11% by weight. Considering that the powder before heating at 1000 ° C. contains 10 to 20% by weight of water depending on the humidity, it can be said that the Cs concentration before and after firing is almost the same.

After drying for 72 hours, the solidified product before heating at the first heating temperature and the simulated waste after heating at the second heating temperature were pulverized to elute Cs, and the amounts of Al and Si leached were evaluated. The powder was 0.5 to 5 mm, immersed in 248 g of pure water 10 times the powder weight of 24.8 g, and shaken in a nitrogen atmosphere for one week. Fine powder in the shaking liquid was removed by a centrifuge, and the amounts of Cs, Al and Si in the supernatant were measured by ICP-MS / AES. As a result, the elution amount of Cs was below the detection limit (10 ppb). When the elution amounts of Al and Si, which are the main components of the geopolymer, were measured for an elution time of 7 days, the elution amounts were 20 ppb and 180 ppb, respectively. From the composition of Al and Si of the powder, the leaching rates were 0.0003 and 0.0016%, respectively. That is, the elution of Cs was zero, and the leaching of skeletal components was almost zero. The geopolymer using this metacaolin had the smallest amount of leached out of the four raw materials of the examples. This indicates that this geopolymer skeleton is the most stable.

The amount of Cs eluted before calcination was 84 ppb, and the amount of Elution of Al and Si, which are the main components of the geopolymer, was 40,000 ppb and 94,000 ppb. From the composition of Al and Si of the powder, the leaching rates were 0.30 and 0.46%, respectively. Therefore, the leaching rates of Al and Si were improved by 1000 times and 287 times by firing.

A simulated waste was produced in the same manner as above except that cesium chloride was not mixed, and the proportion of amorphous components in the simulated waste was examined by an X-ray crystal diffraction method. The measurement sample was prepared by pulverizing the simulated waste with a planetary ball mill (P-6, zirconia pot, Fritsch Japan) into powder. The measurement was carried out by an internal standard method and Rietveld analysis using an X-ray diffraction analyzer SmartLab (Rigaku) and NIST silicon powder (640c) as an internal standard substance. The amorphous component of the simulated waste (excluding Cs) obtained by using the porous material of Example 1 was 95.9% by weight, and the crystalline component was 4.1% by weight.

[Example 2] Barrier property of solidified body using Poster450 Water glass (42 g of Fuji Chemical JIS No. 1 mixed with 24 g of water and 0.5 g of sodium hydroxide) having an adjusted water content as an alkali silicate is uniformly mixed. Mixed. 0.18 g of cesium chloride was added thereto as simulated waste, and the mixture was further mixed. Metakaolin powder (manufactured by Imerys, 48 g) was added thereto, and the mixture was stirred for 5 minutes to obtain a uniform solution. The amorphous component of the metakaolin powder used was about 98% by weight. The cesium concentration calculated from the charging ratio was 0.1% by weight. Next, a fixed amount of the solution was filled in a square plastic container with a lid (31 mm x 31 mm x 10 mm) and sealed with a parafilm. After curing for 28 days, the package was opened and dried in an 85% RH environment for 72 hours and in a 55% RH environment for 72 hours.

After measuring the side length and thickness with a micrometer, the dried plate sample is heated to 200 ° C from room temperature for 2 hours (heating at the first heating temperature) and then raised to 1000 ° C in 2 hours (depending on the second heating temperature). (Heating), the heating was stopped, and the heat was removed to room temperature. After heat removal, the side length and thickness were measured. The volume shrinkage was 40% due to the volume change before and after heating. The density was 1.47 g / cm ³ . Further, another plate sample before heating was pulverized with a planetary ball mill (P-6, zirconia pot, Fritsch Japan), and after acid dissolution, the Cs concentration was confirmed by ICP-MS and found to be 0.097% by weight. .. The plate sample after heating was also crushed in the same manner, and the Cs concentration was confirmed to be 0.11% by weight. Considering that the powder before heating at 1000 ° C. contains 10 to 20% by weight of water depending on the humidity, it can be said that the Cs concentration before and after firing is almost the same.

After drying for 72 hours, the solidified product before heating at the first heating temperature and the simulated waste after heating at the second heating temperature were pulverized to elute Cs, and the amounts of Al and Si leached were evaluated. The powder was 0.5 to 5 mm, immersed in 206 g of pure water 10 times the powder weight of 20.6 g, and shaken in a nitrogen atmosphere for one week. Fine powder in the shaking liquid was removed by a centrifuge, and the amounts of Cs, Al and Si in the supernatant were measured by ICP-MS / AES. As a result, the elution amount of Cs was below the detection limit (10 ppb). The elution amounts of Al and Si, which are the main components of the geopolymer, were 1200 ppb and 1600 ppb. From the composition of Al and Si of the powder, the elution rates were 0.01 and 0.007%, respectively.

The amount of Cs eluted before calcination was 170 ppb, and the amount of Elution of Al and Si, which are the main components of the geopolymer, was 35,000 ppb and 180,000 ppb. From the composition of Al and Si of the powder, the leaching rates were 0.28 and 0.83%, respectively. Therefore, calcination improved the leaching rates of Al and Si by 28 times and 118 times.

A simulated waste was produced in the same manner as above except that cesium chloride was not mixed, and the ratio of the amorphous component in the simulated waste was examined in the same manner as in Example 1. The amorphous component of the simulated waste (excluding Cs) obtained by using the porous material of Example 2 was 99.1% by weight, and the crystalline component was 0.9% by weight.

[Example 3] Barrier property of solidified body using New Zealand kaolin Uniform water glass (42 g of Fuji Kagaku JIS No. 1 mixed with 16 g of water and 0.5 g of sodium hydroxide) whose water content has been adjusted as an alkali silicate). Was mixed with. 0.14 g of cesium chloride was added thereto as simulated waste, and the mixture was further mixed. Metakaolin powder (NZ kaolin, 48 g) was added thereto, and the mixture was stirred for 5 minutes to obtain a uniform solution. The cesium concentration calculated from the charging ratio was 0.1% by weight. Next, a fixed amount of the solution was filled in a square plastic container with a lid (31 mm x 31 mm x 10 mm) and sealed with a parafilm. After curing for 28 days, the package was opened and dried in an 85% RH environment for 72 hours and in a 55% RH environment for 72 hours.

After measuring the side length and thickness with a micrometer, the dried plate sample is heated to 200 ° C from room temperature for 2 hours (heating at the first heating temperature) and then raised to 1000 ° C in 2 hours (depending on the second heating temperature). (Heating), the heating was stopped, and the heat was removed to room temperature. After heat removal, the side length and thickness were measured. The volume shrinkage was 31% due to the volume change before and after heating. The density was 1.63 g / cm ³ . Further, another plate sample before heating was pulverized with a planetary ball mill (P-6, zirconia pot, Fritsch Japan), and after acid dissolution, the Cs concentration was confirmed by ICP-MS and found to be 0.10% by weight. .. The plate sample after heating was also crushed in the same manner, and the Cs concentration was confirmed to be 0.12% by weight. Considering that the powder before heating at 1000 ° C. contains 10 to 20% by weight of water depending on the humidity, it can be said that the Cs concentration before and after firing is almost the same.

After drying for 72 hours, the solidified product before heating at the first heating temperature and the simulated waste after heating at the second heating temperature were pulverized to elute Cs, and the amounts of Al and Si leached were evaluated. The powder was 0.5 to 5 mm, immersed in 208 g of pure water 10 times the powder weight of 20.8 g, and shaken in a nitrogen atmosphere for one week. Fine powder in the shaking liquid was removed by a centrifuge, and the amounts of Cs, Al and Si in the supernatant were measured by ICP-MS / AES. As a result, the elution amount of Cs was below the detection limit (10 ppb). The elution amounts of Al and Si, which are the main components of the geopolymer, were 1200 ppb and 1200 ppb. From the composition of Al and Si of the powder, the elution rates were 0.015 and 0.008%, respectively.

The amount of Cs eluted before calcination was 59 ppb, and the amount of Elution of Al and Si, which are the main components of the geopolymer, was 21000 ppb and 53000 ppb. From the composition of Al and Si of the powder, the leaching rates were 0.26 and 0.35%, respectively. Therefore, calcination improved the leaching rates of Al and Si by 17 times and 44 times.

A simulated waste was produced in the same manner as above except that cesium chloride was not mixed, and the ratio of the amorphous component in the simulated waste was examined in the same manner as in Examples 1 and 2. The amorphous component of the simulated waste (excluding Cs) obtained by using the porous material of Example 3 was 96.8% by weight, and the crystalline component was 3.2% by weight.

[Example 4] Barrier property of solidified product using Korean kaolin Uniform water glass (42 g of Fuji Chemical JIS No. 1 mixed with 16 g of water and 0.5 g of sodium hydroxide) having an adjusted water content as an alkali silicate is uniformly mixed. Was mixed with. 0.07 g of cesium chloride was added thereto as simulated waste, and the mixture was further mixed. Metakaolin powder (Korean kaolin, 48 g) was added thereto, and the mixture was stirred for 5 minutes to obtain a uniform solution. The cesium concentration calculated from the charging ratio was 0.05% by weight. Next, a fixed amount of the solution was filled in a square plastic container with a lid (31 mm x 31 mm x 10 mm) and sealed with a parafilm. After curing for 28 days, the package was opened and dried in an 85% RH environment for 72 hours and in a 55% RH environment for 72 hours.

After measuring the side length and thickness with a micrometer, the dried plate sample is heated to 200 ° C from room temperature for 2 hours (heating at the first heating temperature) and then raised to 1000 ° C in 2 hours (depending on the second heating temperature). (Heating), the heating was stopped, and the heat was removed to room temperature. After heat removal, the side length and thickness were measured. The volume shrinkage was 45% due to the volume change before and after heating. The density was 2.0 g / cm ³ . Another plate sample before heating was pulverized with a planetary ball mill (P-6, zirconia pot, Fritsch Japan), and after acid dissolution, the Cs concentration was confirmed by ICP-MS and found to be 0.049% by weight. .. The plate sample after heating was also crushed in the same manner, and the Cs concentration was confirmed to be 0.057% by weight. Considering that the powder before heating at 1000 ° C. contains 10 to 20% by weight of water depending on the humidity, it can be said that the Cs concentration before and after firing is almost the same.

After drying for 72 hours, the solidified product before heating at the first heating temperature and the simulated waste after heating at the second heating temperature were pulverized to elute Cs, and the amounts of Al and Si leached were evaluated. The powder was 0.5 to 5 mm, immersed in 248 g of pure water 10 times the powder weight of 24.8 g, and shaken in a nitrogen atmosphere for one week. Fine powder in the shaking liquid was removed by a centrifuge, and the amounts of Cs, Al and Si in the supernatant were measured by ICP-MS / AES. As a result, the elution amount of Cs was below the detection limit (10 ppb). The elution amounts of Al and Si, which are the main components of the geopolymer, were 1500 ppb and 2000 ppb. From the composition of Al and Si of the powder, the leaching rates were 0.023 and 0.015%, respectively.

The amount of Cs eluted before calcination was 85 ppb, and the amount of Elution of Al and Si, which are the main components of the geopolymer, was 28,000 ppb and 120,000 ppb. From the composition of Al and Si of the powder, the elution rates were 0.28 and 0.83%, respectively. Therefore, calcination improved the leaching rates of Al and Si by 12 times and 55 times.

A simulated waste was produced in the same manner as above except that cesium chloride was not mixed, and the ratio of the amorphous component in the simulated waste was examined in the same manner as in Examples 1 to 3. The amorphous component of the simulated waste (excluding Cs) obtained by using the porous material of Example 4 was 83.4% by weight, and the crystalline component was 16.6% by weight.

[Comparative Example] Barrier property of hardened Portland cement To 100 g of ordinary Portland cement (401K, Cement Association), 0.18 g of CsCl and 35 g of pure water were added and kneaded for 5 minutes. The cesium concentration calculated from the charging ratio was 0.1% by weight. Next, a fixed amount of the solution was filled in a square plastic container with a lid (31 mm × 31 mm × 10 mm) and sealed with a parafilm. After curing for 28 days, the package was opened and dried in an 85% RH environment for 72 hours and in a 55% RH environment for 72 hours.

The solidified cement before heating was pulverized to elute Cs, and the amounts of Al and Si leached were evaluated. The powder was set to 0.5 to 5 mm, immersed in 100 g of pure water 10 times the powder weight of 10 g, and shaken in a nitrogen atmosphere for one week. Fine powder in the shaking liquid was removed by a centrifuge, and the amounts of Cs and Ca in the supernatant were measured by ICP-MS / AES. As a result, the amount of Cs eluted was 1,000,000 ppm, and 100% was eluted. The elution amount of Ca, which is the main component, was 650000 ppm. From the amount of Ca in the powder, the leaching rate of the cement skeleton was 1.9%. It can be said that the cement solidified body does not have a barrier property.

The waste according to the present invention can be advantageously used in the treatment of low-level radioactive waste and emission-controlled toxic substances.

Claims (9)

A porous body containing an aluminosilicate having an Al / Si molar ratio of 0.3 to 1 as a main component and a radioactive element or a metal element immobilized on the porous body are contained, and the radioactive element or the metal element is fixed. Amorphous waste body in which the density of the formed porous body portion is 2.2 g / cm ³ or more. The waste according to claim 1, wherein the waste is a heated waste. The waste according to any one of claims 1 or 2, wherein the waste contains 80% by weight or more of an amorphous component. The waste according to any one of claims 1 to 3 and one or more coverings selected from cement, mortar, geopolymer, asphalt, resin, or metal that coat the periphery of the waste. Including, coated waste. A metal container is filled with the waste according to any one of claims 1 to 3 and one or more coverings selected from cement, mortar, geopolymer, asphalt, resin, or metal. Container filling waste. A step of preparing a mixture containing an alkali silicate, an alkaline active filler, water, and a radioactive element or a metal element.
The step of curing the mixture to obtain a solid substance, and
A step of heating the solid matter at a first heating temperature of 100 to 250 ° C.
A method for producing a waste product, which comprises a step of further heating the heated solid matter at a second heating temperature of 800 to 1000 ° C. The production method according to claim 6, wherein the temperature is raised from the first heating temperature to the second heating temperature within 8 hours. The production method according to claim 6 or 7, wherein the alkaline active filler contains 80% by weight or more of an amorphous component. A waste product produced by the production method according to any one of claims 6 to 8.