JP2001289993A - Device for manufacturing paste for solidification of radioactive waste including amphoteric metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a paste capable of forming a protective film suppressing hydrogen gas from being produced by the reaction between an amphoteric metal included in radioactive waste and a hydraulic solidifying material. SOLUTION: Cement, water, and a protective film forming agent for forming, on the surface of an amphoteric metal, a protective film suppressing hydrogen gas from producing are fed from a solidifying material storage tank 3, a water tank 5, and a protective film forming chemical tank 7 into a mixer 2, respectively. These substances are mixed in the mixer 2, and the mixture thus obtained is filled into a solidifying container 1 filled with radioactive burned ash including the amphoteric metal. Thus, the paste capable of forming the protective film suppressing hydrogen gas from producing on the surface of the amphoteric metal can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing a paste for solidifying radioactive waste containing amphoteric metal, and more particularly to non-combustible miscellaneous solid waste containing amphoteric metal or amphoteric metal generated from a nuclear power plant. The present invention relates to an apparatus for solidifying a radioactive waste containing an amphoteric metal, which is suitable for being applied to a radioactive waste treatment method for treating incineration ash generated by incineration of radioactive inflammable miscellaneous solids.

[0002]

2. Description of the Related Art In order to finally dispose of radioactive waste generated from a nuclear power plant or the like underground, the radioactive nuclide contained in the waste must be treated so as not to easily diffuse to the outside. It is required to provide an artificial barrier by solidifying into a dedicated container in a stable form. As such solidified materials, hydraulic solidifying materials such as asphalt, plastics and cement, mortar, and concrete are common materials, and are inexpensive materials having excellent physical properties such as strength. It is widely used for solidifying waste materials regardless of non-radioactivity. In particular, cement-based solidification materials are widely used because they are inexpensive and easy to handle and solidify. Since cement is generally highly alkaline and radionuclide such as cobalt-60, nickel-63, transuranium element and the like is fixed as hydroxide precipitate, it is suitable as an artificial barrier material for containing radionuclide. Excellent heat resistance and radiation resistance are also one of the advantages.

[0003] Radioactive waste generated from nuclear power plants includes pipes, valves, and the like generated during on-site work such as periodic inspections.
Metal waste materials, heat insulation materials, concrete pieces, used HEPA
There is non-combustible radioactive miscellaneous solid waste such as filters. Further, there is incineration ash generated when incinerating combustible radioactive miscellaneous solid waste. Radioactive incineration ash after incineration of combustible radioactive solid waste and non-combustible radioactive solid waste often contain metals such as aluminum and zinc. Magn
Aluminum alloy is used for the splitter that constitutes ox fuel, and waste aluminum alloy is generated with spent fuel.

[0004] Accordingly, there is a need for the development of a technique for solidifying these radioactive wastes while maintaining a healthy artificial barrier function for these metals. However, at present, these radioactive wastes are directly packed in drums and stored in a nuclear power plant, and there is a strong demand for solidification into a stable solidified body and disposal underground.

[0005] It has been pointed out that, when non-combustible radioactive miscellaneous solid waste and radioactive incinerated ash are solidified with an alkaline solidifying material such as cement, a solidified material having poor physical properties is often formed. As a cause, these radioactive wastes contain a small amount of metal fragments or metal powders that generate hydrogen gas by reacting with alkali components in cement,
It has become clear that the cement reacts with a metal such as aluminum during the hardening to generate hydrogen, and the hydrogen generates bubbles and cracks in the solidified body. However, metals have similar appearances, and it is physically difficult to separate only relevant metal pieces and metal powder from waste.

An example of a solution to such a problem at the time of solidification is disclosed in Japanese Patent Publication No. 2-62200 and Japanese Patent Laid-Open No. 4-2006.
No. 80 and JP-A-57-51163.

[0007]

[Problems to be Solved by the Invention]
In the publication, when incinerated ash is solidified with cement, incinerated ash and alkali are mixed in advance and the generation of hydrogen gas is terminated to some extent before solidification, and the generation of hydrogen after mixing of cement and incinerated ash is suppressed. A method is disclosed. The publication also discloses that incineration ash, ZnO or PbO, inhibits the progress of the hydration reaction during cement solidification.

However, according to the former method, a pre-treatment step is required for solidifying the incineration ash with cement. When the content of metal such as aluminum is large, the pre-treatment requires a long time. Conversely, wasteful pretreatment is performed on incineration ash that does not contain amphoteric metals. In addition, since the metal is dissolved in this pretreatment step, if the metal is contaminated or activated, the radionuclide is dispersed in the processing solution, and the solidified body secures the isolation performance as an artificial barrier. To do so, new countermeasures are needed. Further, it is not preferable in terms of safety to generate a large amount of hydrogen as a combustible gas in the pretreatment step.

The latter description of hydration only discloses that ZnO or PbO inhibits the progress of the hydration reaction at the time of cement solidification. It has nothing to do with the gist of the present invention that it can be suppressed.

Japanese Patent Application Laid-Open No. 4-200680 discloses a kneaded product obtained by kneading a cement by controlling an alkali component in the cement during the solidification of a non-combustible miscellaneous solid containing aluminum. A method is disclosed in which the pH of a cement paste is reduced to 13 or less to produce a solidified body in which hydrogen generation is suppressed.

However, according to the method disclosed in the publication, the generation of hydrogen can be reduced by lowering the pH of the paste, but the generation amount cannot be reduced to a level that can be regarded as almost zero. In addition, as described above, the high alkalinity means that cobalt-60, nickel-
Since 63 or the like is a requirement to stably solidify, if the pH of the cement is too low, the function of solidifying the radionuclide inherent in the cement is lowered.

The problem that such a metal reacts with an alkaline substance such as cement to generate hydrogen is not necessarily a problem inherent in the treatment of radioactive waste, but is also regarded as a problem in the field of general industrial waste. JP-A-57-51163
In the official gazette, when the incineration ash and industrial waste of municipal garbage are formed by adding an additive or a binder corresponding to a solidifying material, aluminum reacts with alkali to generate hydrogen. Is a method of obtaining a predetermined molded product under stable conditions close to neutral pH 5 to 9 without generating hydrogen gas, and a method of preliminarily reacting all contained aluminum under high alkaline conditions of pH 10 to 12 It discloses that by forming a molded article, a molded article having excellent physical properties can be obtained.

However, in the former method, it is difficult to solidify using a medium having a pH other than 5 to 9 (for example, a cement-based hydraulic solidifying material). In the latter method, a method similar to the method disclosed in Japanese Patent Application No. 62200/1990 involves solidifying radioactive waste containing aluminum after pretreating aluminum in an alkaline atmosphere in advance. Occurs.

An object of the present invention is to provide a paste capable of forming a protective film for suppressing generation of hydrogen gas due to a reaction between an amphoteric metal contained in radioactive waste and a solidifying material.
An object of the present invention is to provide an apparatus for producing a paste for solidifying radioactive waste containing an amphoteric metal.

[0015]

The features of the present invention to achieve the above-mentioned object are as follows: a hydraulic hardening material supply means for supplying a hydraulic hardening material; and a protective film for suppressing hydrogen generation on the surface of the amphoteric metal. A protective film forming agent supplying means for supplying a protective film forming agent to be supplied, a water supplying means, and a kneading device for kneading the hydraulic setting material, the protective film forming agent and water, and discharging the produced paste. It is in.

In the present invention, the amphoteric metal is dissolved and ionized in both the acidic solution and the alkaline solution,
It is a metal having the property of generating hydrogen at the same time, and specifically, aluminum, zinc, tin, lead, alloys containing these metals as main components, and the like are applicable.

Hydrogen is generated based on the reaction between the components of the hydraulic hardening material, the amphoteric metal ions and water (free water). The hydration accelerator accelerates the free water required for the above reaction. That is, the hydration reaction accelerator promotes the hydration reaction of the hydraulic solidifying material, and hydrates free water at an early stage. For this reason, water (free water) runs short, so that the above-described hydrogen generation reaction is suppressed, and the generation of hydrogen is suppressed.

Preferably, in addition to the hydration reaction accelerator, a cement-based hydraulic hardening material having an R ₂ O value of 0.4% or less is used as the hydraulic hardening material. R ₂ O value is 0.4%
By using the following cement-based hydraulic hardening material, the concentration of hydroxyl ions in the hardening material paste is reduced (the pH is lowered). For this reason, the hydrogen generation rate decreases, and the amount of generated hydrogen is suppressed. In addition to the hydration reaction accelerator, the use of a cement-based hydraulic solidification material having an R ₂ O value of 0.4% or less as the hydraulic solidification material can suppress the hydrogen generation by the hydration reaction accelerator, And the effect of suppressing hydrogen generation by the water-curable solidifying material, so that the generation of hydrogen becomes almost zero in the treatment of radioactive waste containing amphoteric metal using a hydraulic hardener. .

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The reaction between an alkaline solidifying material and an amphoteric metal can be schematically represented as follows.

[0022] Three methods that can suppress the generation of hydrogen gas will be described by using amphoteric metal + water + hydroxide ion → metal hydroxide ion + hydrogen (Equation 1). The first method is to form a protective film on the surface of the amphoteric metal to suppress hydrogen generation.
This method reduces the reaction rate of (Equation 1) by acting on the amphoteric metal itself on the left side of (Equation 1) and forming a protective film on the surface of the amphoteric metal, that is, a layer that delays diffusion of ions. That is, the hydrogen generation rate is reduced. To form the above-mentioned protective film, it is desirable to add a chemical. This protective film is roughly classified into three types: (1) oxide film (passive film), (2) precipitated film, and (3) adsorption film. Of these, oxide films of amphoteric metals do not have corrosion resistance in alkalis, and agents that form oxide films are not suitable for use in alkaline solidified materials. Experiments by the inventors have shown that an agent that produces is suitable. Examples of agents that form an insoluble precipitate film on the surface of amphoteric metals include inorganic phosphates and their neutral salts, organic phosphates and their neutral salts (phosphonates), polymerized phosphates and their salts. Salt, silicon polyphosphate, silicate and its neutral salt,
Polymerized silicate and its neutral salts, nitrates, lithium-containing inorganic salts and the like. Examples of chemicals that form a film by electrostatically or chemically adsorbing on metal surfaces include polar groups such as amines, mercaptans and alkylbenzenesulfonic acids, which are electronegative such as nitrogen, oxygen, phosphorus, and sulfur. There are organic compounds containing elements having a high degree, and chelating agents such as hydroxyquinoline. These chemicals are mixed with, for example, a solidifying material and kneaded with water to solidify radioactive waste containing an amphoteric metal. In this solidification, these chemicals dissolve and disperse in water, and act on the surface of the amphoteric metal contained in the radioactive waste to form a protective film.

The appropriate amount of these chemicals to be added is 0.1 to 10% based on the solidified material. Even if a protective film is directly formed on the amphoteric metal before the solidification treatment, the solidified material is kneaded during the solidification. The same effect can be obtained by blending with the solidifying material powder or kneading water before, or adding to the paste after kneading.

Therefore, by using the first method,
In the process of solidifying radioactive waste with an alkaline hydraulic solidifying material, pretreatment of radioactive waste and separation treatment are not required, and the properties of hydraulic solidifying material can be fully exhibited,
The generation of hydrogen gas due to the reaction between the amphoteric metal contained in the radioactive waste and the hydraulic hardening agent can be suppressed.

Next, a second method is to use a hydration reaction accelerator to accelerate the hydration reaction of the hydraulic set material. In this second method, water (free water) contributing to the reaction (free water) is crystallized at an early stage on the left side of (Equation 1), that is, by promoting the hydration reaction of cement, the reaction rate of (Equation 1) is reduced. It has the effect of lowering the hydrogen generation rate. To promote the hydration reaction, it is desirable to add the following agents. Examples of the agent for promoting the hydration reaction include calcium-containing inorganic salts (eg, calcium chloride, calcium nitrate, etc.), sodium silicate (water glass), calcium aluminate which is a sintered body of CaO and Al ₂ O _3. , Alunite, etc. These agents (1) accelerate the hydration reaction of the cement component by increasing the concentration of calcium ions in the solidifying material paste. (2) The additive agent itself reacts with the cement component to form a new hydrate. It has one or both actions, and has the function of hydrating free water at an early stage. further,
The inventors experimentally demonstrated that the above-mentioned calcium-containing inorganic salt and polymerized phosphate have a favorable property of having both an action of forming a protective film on the surface of an amphoteric metal and an action of accelerating a hydration reaction of cement. Revealed.

[0024] The addition of these agents in an amount of 10% or more has an adverse effect on the hardening of the solidified material.
% Is an appropriate amount, and the same effect can be obtained either by mixing it with the solidified material powder before kneading the solidified material or adding it to the paste after kneading.

Therefore, the second method produces the same effect as that obtained by the first method.

Finally, a third method of reducing the alkalinity of the solidified material will be described. In the third method, on the left side of (Equation 1), the action of reducing the hydroxyl ion concentration in the solidified paste (lowering the pH) is
The reaction rate of (Equation 1) is reduced, that is, the hydrogen generation rate is reduced. For example, consider cement as a hydraulic hardening material. Na ₂ O, K ₂ which is an alkaline component in cement
O and CaO show alkalinity by mixing the cement and water by the following reaction.

Na ₂ O + water → 2NaOH K ₂ O + water → 2KOH (Equation 2) CaO + water → Ca (OH) ₂ Therefore, a method of reducing the alkalinity in the solidified material, ie, Na which is an alkali component in the solidified material Methods for reducing the content of ₂ O, K ₂ O, and CaO include (1)
A method using low-alkali cement or white cement having a low content of ₂ O and K ₂ O, and (2) SiO ₂ , Al ₂ O ₃
Is mixed with cement and diluted, that is, the content ratio of Na ₂ O, K ₂ O, and CaO is reduced to SiO ₂ , A
By substituting with an oxide such as l ₂ O _3, Na ₂ O, K
There is a method of reducing the content ratio of ₂ O and CaO. Of course, the method (2) can be applied to the method (1) to further reduce the alkalinity to such an extent that no problem is caused. SiO ₂ ,
Inorganic materials mainly composed of Al ₂ O ₃ include aggregates such as sand and gravel,
By-products in general industries such as blast furnace slag, silica fume, and fly ash are suitable.
Addition of a natural inorganic material having a radionuclide adsorption performance such as vermiculite, clinoptilolite, cristobalite, kaolinite, and the like, has the effect of improving the performance of the solid as an artificial barrier.

The amount of the inorganic material to be added can be selected from a wide range of 5 to 80% based on the total solid content of the cement and the additive, but in consideration of the injectability and strength of the solidified material paste,
A range of 30 to 60% is desirable.

In order to suppress the reaction between the hydraulic hardening material and the amphoteric metal and the generation of hydrogen, a chemical agent is mainly added to (1) to form a protective film on the surface of the amphoteric metal, (2) the hardening material It is effective to use three methods of promoting the hydration reaction of (3) and (3) reducing the alkalinity of the solidified material. Each of these methods has an effect of reducing the amount of generated hydrogen alone, and a greater effect can be obtained by using a plurality of methods in combination. In particular, the agent (1) tends to delay the hydration reaction of the cement, so that it is desirable to use it in combination with (2). Therefore, by using at least two or more of the three methods described above, the generation of hydrogen gas due to the reaction between the amphoteric metal and the hydraulic solidifying material can be made almost zero.

As the alkaline solidifying material used in the present invention, a cement-based hydraulic solidifying material is generally used. CaO, SiO ₂ , Al ₂ O are used as cement-based hydraulic solidifying materials.
Ordinary Portland cement containing ₃ as the main component, early-strength Portland cement, sulfate-resistant Portland cement, blast furnace cement, silica cement, sodium silicate (water glass), fly ash cement, alumina cement,
A paste in which expanded cement, oil well cement or the like is kneaded with water, a mortar in which powdered aggregate such as sand is mixed, and a concrete in which granular coarse aggregate such as gravel is mixed are applicable.

Hereinafter, an embodiment which reflects the above study results will be described.

(Example 1) In the first example, incineration ash generated when paper, wood chips, resin, and the like generated from a nuclear power plant are incinerated is used for forming a protective film on a cement-based hydraulically solidified material. The present invention relates to a case where a drug and a hydration reaction promoting drug are blended and solidified stably in a container.

This embodiment will be described with reference to FIG. First, a predetermined amount of incinerated ash is put into the solidification container 1. The solidification container 1 may be an ordinary drum, but it is desirable that the solidification container 1 be provided with a concrete lining. A predetermined amount of the solidified material is charged from the solidified material storage tank 3 to the kneading machine 2 via the fixed amount supply device 4, and a predetermined amount of the kneading water is injected from the water tank 5 via the electromagnetic valve 6. Further, a predetermined amount of one of the chemicals for forming a protective film on the surface of the amphoteric metal is charged into the kneading machine 2 from the chemical tank 7 for forming the protective film via the quantitative supply device 8. This chemical may be mixed in advance with the solidifying material or kneading water, or the chemical tank 7 for forming the protective film may be arranged in the solidifying material storage tank 3 or the water tank 5 and mixed with the solidifying material or kneading water. It may be. In the former case, the protective film forming chemical tank 7 and the quantitative supply device 8 become unnecessary. It is desirable that the stirring blades of the kneader 2 be operated during these charging. Further, by adding 1 to 5% of a β-naphthalene-based water reducing agent to the solidified material, the water / solidified material ratio can be reduced, and the physical properties of the produced solidified material can be improved. After kneading for a predetermined time, the produced paste is injected into the solidification container 1 through the shutter 9. At this time, a predetermined amount of one selected from the hydration reaction accelerating agents is put into the solidification container 1 from the hydration reaction accelerating agent tank 15 via the quantitative supply device 16. The stirring blade 10 is inserted here, and the incineration ash and the paste of the solidified material are uniformly mixed. The stirring blade 10 has a mechanism that can be separated. After stirring for a certain period of time, the stirring blade is separated, the upper lid is covered, and curing is performed to complete a solidified body. After kneading, the stirring blade 10 can be pulled out without being separated and used repeatedly. The hydration reaction-promoting agent can be added to the solidifying material in advance, but in order to ensure the pot life in the kneader, the solidifying material paste is added when the paste is poured into the solidifying container 1. It is desirable. Cement-based hydraulic hardening material powder is stored in the hardening material storage tank 3. Cement having an alkalinity R ₂ O value of 0.4% or less is desirable. It is also possible to mix the aggregate in advance.

Next, a specific embodiment will be described. Table 1 shows the composition of the solidified incinerated ash.

[0035]

[Table 1]

As shown in Table 1, the incinerated ash contained considerable amounts of aluminum and its oxides, lead and zinc, which react with cement. First, using ordinary Portland cement as a solidifying material, a paste kneaded at a water cement ratio of 0.4 was injected to solidify the incinerated ash. The volume ratio between the incinerated ash and the solidified paste was 1: 1. as a result,
Voids and cracks which appeared to be traces of hydrogen were generated in the formed solid. Thus, as shown in Table 2, under the same conditions, a cement with a slightly low alkalinity resistance as a cement, silicon polyphosphate as a chemical for forming a protective film, and calcium nitrate as a chemical for accelerating a hydration reaction are used. The incinerated ash was solidified.

[0037]

[Table 2]

As a result, no voids or cracks were generated in the solidified solid, and a sound solid could be produced. A test in which the solid was immersed in water was performed, but no change was observed in the appearance, and the soundness was maintained.

In this embodiment, as described above, white cement, silica cement, blast furnace cement, fly ash cement or the like can be used instead of the sulfate resistant cement. Blast furnace slag instead of silica fume,
Fly ash, chamotte, etc. can be used. In place of silicon polyphosphate, lithium salt, nitrate, phosphonic acid and salts thereof, inorganic and organic phosphoric acid and salts thereof, amines, mercaptans and the like can be used as the protective film forming agent. As a hydration reaction promoting agent, calcium chloride, water glass, calcium aluminate and the like can be used instead of calcium nitrate.

Here, the effects of the protective film forming agent and the hydration reaction accelerating agent will be described.

First, in order to examine the effect of the protective film forming agent in cement, a corrosion test was performed on an aluminum piece using the supernatant liquid of cement paste. Since the supernatant liquid can exclude the effect of the hydration reaction of the cement, it is convenient to examine the pure effect of the agent that forms the protective film. The cement used was ordinary Portland cement and the sulfate-resistant cement used in Example 1.
There is a difference in composition such as

[0042]

[Table 3]

That is, in the sulfate-resistant cement, in order to increase the sulfuric acid resistance, Na ₂ O, which is an alkaline component in the cement, is used.
It is a cement having a low K ₂ O content and conforming to the third method described above. The experimental method is described below. First, 100 parts by weight of cement and 100 parts by weight of tap water were sufficiently mixed with a stirrer, and then suction-filtered to prepare a supernatant. The pH of the supernatant at this time was 13.9 with ordinary Portland cement,
It was 13.4 with sulfate resistant cement. This supernatant was added to 10
The test was taken in a 0 cc test tube and 1 g of an aluminum piece was immersed in the test tube. The generated hydrogen gas was collected by displacement on water, and the volume was measured. The chemicals used were silicon polyphosphate, a kind of polymeric phosphate, nitrilotrismethylene phosphonic acid, a kind of organic phosphoric acid, calcium chloride and lithium nitrate. The amount added is 100 parts by weight of the supernatant liquid.
The amount of the added drug was 1 part by weight.

FIG. 2 shows the change over time in the amount of generated hydrogen in this experiment. In the supernatant containing no chemicals, about 120 cc of hydrogen gas was generated in 24 hours for ordinary Portland cement and 40 cc for hydrogen sulfate-resistant cement. However, silicon polyphosphate and nitrilotrismethylene phosphonic acid were added to the supernatant of sulfate-resistant cement. From the aluminum piece added with
It was found that the amount of generation could be reduced to 1/20 of 2 cc from aluminum flakes to which 4 cc of 0 and calcium chloride and lithium nitrate were added. After 24 hours, the aluminum piece after the test was taken out and the surface was observed.As a result, a white, gel-like precipitate was uniformly deposited on the metal surface of the aluminum piece to which silicon polyphosphate and nitrilotrismethylenephosphonic acid were added. A protective film was formed. On the other hand, in the aluminum piece to which calcium chloride and lithium nitrate were added, a denser crystalline precipitate was deposited. This experiment confirmed that the formation of such a precipitation film suppressed the dissolution reaction on the aluminum surface and reduced the amount of generated hydrogen.

Second check of the effect of the protective film forming agent
As an experiment, under the same conditions, NaOH having a pH of 13.5 was used.
The test was also performed on aluminum pieces in an aqueous solution. NaO
In the aqueous H solution, the corrosion reaction of aluminum is remarkable and the amount of generated hydrogen is larger than in the supernatant of the cement. As additive agents, sodium nitrate, potassium nitrate, and lithium nitrate, which are alkali metal nitrates, and lithium chloride as another lithium-containing salt were added at 1 mol / l.

FIG. 3 shows the change over time in the amount of hydrogen generated in the second experiment. About 600 cc of hydrogen gas was generated in 5 hours with no addition of aluminum pieces in an aqueous solution of NaOH having a pH of 13.5. It was found that the aluminum pieces to which sodium nitrate and potassium nitrate were added reduced to 400 cc, lithium chloride to 100 cc, and lithium nitrate to 40 cc. From the results of this experiment, although the effect of nitrate as an additive was also recognized, it was found that the effect of lithium was large. Further, since the curve of the change over time in the amount of generated hydrogen was flat after one hour, it was found that the protective film became complete after a while after the aluminum piece was brought into contact with the alkali solution.

Next, the effect of suppressing the generation of hydrogen due to the reaction between the amphoteric metal and the cement by adding a hydration reaction promoting agent to the solidifying material will be described.

As a standard composition, a paste was prepared by kneading ordinary Portland cement at a water / cement ratio of 0.32. Calcium chloride was used as a cement hydration reaction accelerator, and calcium nitrate used in the first embodiment was used as the cement. 1% by weight with respect to As reference data, calcium hydroxide was also tested. In the experimental procedure, 1 g of an aluminum piece was put into 50 cc of cement paste, the generated gas was collected by displacement on water, and the volume was measured.

FIG. 4 shows the change over time in the amount of generated hydrogen in this experiment. In the normal Portland cement paste without addition, about 30 cc of hydrogen was generated by the lapse of 6 hours from the input of the aluminum piece, and then leveled off. This means that the initial hydration reaction of ordinary Portland cement was completed in 6 hours, and free water contributing to the dissolution reaction of the aluminum pieces was almost eliminated. In the system to which calcium chloride and calcium nitrate were added, the hydration reaction of the cement was promoted, and the hydrogen evolution curve leveled off in about 2 hours. During this period, the amount of hydrogen generated was 1/10 of the case without addition.
Was 3cc. On the other hand, in the system to which calcium hydroxide was added, no effect of promoting the hydration reaction of the cement was observed, and the amount of generated hydrogen was slightly increased. From this, it was found that among the calcium salts, neutral salts having high solubility had a large effect on promoting the hydration reaction, and salts having low solubility had no effect.

Instead of calcium chloride and calcium nitrate, sodium silicate (water glass), CaO, Al ₂ O ₃
Similar effects can be obtained by using calcium aluminates and alunite (alunite) which are sintered bodies of the above. The appropriate amount of these agents to be added is 0.1 to 10%, preferably 0.1 to 5% with respect to the solidified material, and a sufficient effect can be obtained even with 1%.

Finally, in order to examine the effects of both the protective film forming agent and the hydration reaction promoting agent, in addition to the hydration reaction promoting agent used in the previous experiment, chloride was used as an example of the protective film forming agent. The same experiment was performed for a system in which 1% of calcium and 5% of silicon polyphosphate were added. As a result, as shown in FIG. 4, the amount of generated hydrogen was 1/3 of the system to which calcium chloride and calcium nitrate were added. Therefore, it was found that the combined use of an agent that promotes the hydration reaction of cement and an agent that forms a protective film on the surface of the amphoteric metal can significantly reduce the amount of hydrogen generated by the reaction between the cement and aluminum, which is an amphoteric metal.

As described above, according to the present embodiment,
It is not necessary for pre-treatment, and the generation of flammable hydrogen in the solidified product can be greatly reduced.
A stable solidified body, a solidifying method and a solidifying device for obtaining the same can be provided.

In this embodiment, since the incinerated ash, which is radioactive waste, is not charged into the kneader, washing and maintenance of the kneader are easy, and a large amount of washing waste liquid of the kneader is non-radioactive. There is an advantage that processing is unnecessary.

In the above embodiments, low-alkali cement was used as cement. However, similar effects can be obtained by reducing alkalinity by using ordinary cement. Hereinafter, the effect when the alkalinity is reduced will be described.

In this experiment, a method for reducing and adjusting the content of Na ₂ O, K ₂ O, and CaO, which are alkali components in the solidified material, was conducted by using both a protective film forming agent and a hydration reaction promoting agent. The present invention relates to a method of combining addition.

The cement used was a normal white cement having a total content of Portland cement and Na ₂ O, K ₂ O of 0.4%. Na ₂ O, K _{2 of} these cements
In order to further reduce and adjust the content ratio of O and CaO,
River sand and granulated blast furnace slag were added as aggregates for diluting cement. Table 4 shows the paste conditions of the solidified material and the pH of the paste.

[0057]

[Table 4]

[0058] Thus Na ₂ O is an alkali component in a cement paste of cement reducing adjust the content of K ₂ O is has pH becomes lower, was further reduced by the addition of the aggregate. FIG. 5 shows the results of investigating 1 g of zinc granules as an amphoteric metal into 50 cc of these four types of pastes and examining the change over time in the amount of generated hydrogen. Six hours after the end of the initial hydration reaction of the cement for each paste, the hydrogen generation is almost flat, but the total generation depends on the pH of the paste, and the lower the pH, the lower the hydrogen generation. I understand. According to this embodiment, Na ₂ O is an alkali component in a cement to adjust reduce the content of K ₂ O, it was confirmed further method of adding an aggregate is effective in reducing the amount of hydrogen generation .

FIG. 6 shows the relationship between the total content of Na ₂ O and K ₂ O in cement (R ₂ O value) and the relative value of the amount of hydrogen generated from zinc granules. From this relationship, in order to reduce the amount of hydrogen generated by the reaction between the amphoteric metal and the cement, the R ₂ O value should be adjusted to 0.6% or less, preferably 0.4% or less. Next, FIG. 7 shows the relationship between the amount of added aggregate and the amount of hydrogen generated (relative value), the relative strength of the solidified material, and the evaluation function obtained by arithmetic mean of both. The injectability index indicating the ease of injecting the paste shows the same tendency as the phase strength of the solidified body. According to FIG. 7, the more the amount of the aggregate added, the more effective it is for hydrogen generation. However, if it exceeds 80%, the strength as a solidified material becomes insufficient. preferable. As the amount of aggregate added increases, the paste viscosity also increases, and the index of injectability decreases, resulting in poor injectability. Therefore, the desirable amount of the aggregate added was 30 to 60% based on the total weight of the solidified material.

Next, as an agent for forming a protective film on the surface of zinc granules, 1% of sodium alkylbenzenesulfonate was added to the paste of the composition D. The molecule of sodium alkylbenzenesulfonate is composed of a hydrophilic group and a hydrophobic group, and the hydrophilic group is oriented to the metal side and the hydrophobic group is oriented to the cement paste side to protect the metal surface. as a result,
The amount of hydrogen generated was reduced to 1/5 of that of the composition of D. Furthermore, 1% of calcium chloride, which is a hydration accelerator for cement,
The addition further reduced the amount of hydrogen generation by half.

As described above, the amount of hydrogen generated by the reaction with the amphoteric metal can be reduced by the method of reducing the alkalinity of the solidified material. Therefore, by further adding a method for reducing the alkalinity of the solidified material to Example 1, the amount of generated hydrogen can be reduced to a level close to zero.

(Embodiment 2) In the second embodiment, as in the first embodiment, incineration ash generated when paper, wood chips, resin, etc. generated from a nuclear power plant are incinerated is stabilized in a container. The method relates to a method of solidifying into a solid.

A second embodiment will be described with reference to FIG. In this embodiment, a predetermined amount of the solidified material is supplied from the solidified material storage tank 3 to the kneading machine 2 via the fixed amount supply device 4, and a predetermined amount of the kneading water is injected from the water tank 5 via the electromagnetic valve 6. The points of time and kneading are the same. The solidified material storage tank 3 stores a cement-based hydraulically solidified material powder.
A cement having an R ₂ O value indicating the alkalinity of the cement of 0.4% or less is desirable. It is also possible to mix the aggregate in advance. 1 selected from protective film forming agents
The seed and the agent for accelerating the hydration reaction are previously blended into the solidified material. Here, a predetermined amount of the incinerated ash is put into the kneading machine 2 from the incinerated ash storage tank 11 via the fixed amount supply device 12, and kneaded with the solidified material. After kneading for a predetermined time, the produced paste is poured into the solidification container 1 through the shutter 9, and is covered with the upper lid and cured as it is to complete the solidified body.

According to the second embodiment, as in the first embodiment, no pretreatment is required, and the generation of flammable hydrogen in the solidified material can be greatly reduced, so that destruction by hydrogen can be prevented. A stable solidified body, a solidifying method and a solidifying device for obtaining the same can be provided.

Further, according to the second embodiment, since high shearing force and high-speed kneading in the kneading machine 2 are possible, the homogeneity of the solidified body is improved, and the filling amount of the incinerated ash is improved. be able to.

(Embodiment 3) As a third embodiment, a system suitable for solidifying radioactive metal waste generated from a nuclear power plant will be described.

A third embodiment will be described with reference to FIG. First, the solidified container 1 is filled with radioactive metal wastes cut to an appropriate size and placed on the vibration table 13.
The solidification container may be an ordinary drum, but preferably a concrete lining. A predetermined amount of the solidified material is charged from the solidified material storage tank 3 to the kneading machine 2 via the fixed amount supply device 4, and a predetermined amount of the kneading water is injected from the water tank 5 via the electromagnetic valve 6. Further, a predetermined amount of one of the protective film forming chemicals is charged into the kneading machine 2 from the chemical tank 7 via the quantitative supply device 8. If this medicine is previously mixed with the solidifying material, the medicine tank 7, the fixed amount supply device 8
Becomes unnecessary. It is desirable that the stirring blades of the kneader 2 be operated during these charging. Further, by adding 1 to 5% of a β-naphthalene-based water reducing agent to the solidified material, the water / solidified material ratio can be reduced, and the physical properties of the produced solidified material can be improved. It is desirable that the stirring blade of the kneader 2 has a function of evaluating the viscosity of the paste from the load on the drive motor. After kneading for a predetermined time, the prepared paste is poured into the solidification container 1 through the shutter 9. Here, the vibration table 13 is operated to apply vibration to the solidification container 1, whereby penetration of the solidification material into the gap between the wastes can be promoted.

Cement-based hydraulic hardening material powder is stored in the hardening material storage tank 3. Cement having an alkalinity R ₂ O value of 0.4% or less is desirable. It is also possible to reduce alkalinity by blending aggregate in advance. Although the agent for promoting the hydration reaction of cement can be previously added to the solidifying material, in order to secure the pot life in the kneading machine, it is added when the solidifying material paste is poured into the solidifying container 1. It is desirable to do. Therefore, in the present embodiment, similarly to the third embodiment, when injecting the paste, the hydration reaction promoting agent of the present invention is selected from the hydration reaction promoting agent from the hydration reaction promoting agent tank 15 through the quantitative supply device 16. A predetermined amount of the selected one is charged into the solidification container 1.

Further, in the above, the paste for forming the protective film was prepared together with the solidifying material in the paste, but before the metal waste was put into the solidification container 1, the chemical for forming the protective film was directly dissolved and immersed in dissolved water. Thereby, the purpose can be similarly achieved even if a protective film is formed in advance.

Also in the third embodiment, the solidified material having the composition shown in Table 2 used in the first embodiment was used. First, the injectability of the solidified material was evaluated. Evaluation of the filling situation, after hardening of the cement,
The solidified body is cut in the longitudinal direction, and the void area on the cut surface is 1
If it was 0% or less, it was regarded as good. FIG. 10 shows the evaluation results. If the viscosity of the solidified material paste evaluated from the load on the drive motor of the stirring blade of the kneader 2 is 5000 cp or less,
The filling state of the solidified material was good even without vibration. When the viscosity of the solidified material paste was 5000 cp to 8000 cp, good filling was achieved by vibrating. Therefore,
When solidifying metal waste, by controlling the viscosity of the solidification material paste to 8000 cp or less, the solidification material can be easily solidified by the solidification material injection method from the top of the solidification container filled with radioactive metal waste. The kneading operation of the solidifying material is not required, and the solidifying equipment can be simplified.

In the solidified solid according to the third embodiment, no voids or cracks were generated, and a sound solidified solid could be produced. A test in which the solid was immersed in water was performed, but no change was observed in the appearance, and the soundness was maintained.

Therefore, according to the third embodiment, as in the previous two embodiments, there is no need for pretreatment and the generation of flammable hydrogen in the solidified material can be greatly reduced. It is possible to provide a solidified body which can be prevented and is stable, a solidifying method and a solidifying device for obtaining the solidified body.

Further, by forming a protective film on the waste before solidification, the solidification of the waste can suppress the generation of hydrogen gas due to the reaction between the amphoteric metal contained in the waste and the solidifying material in the pretreatment step. It is possible to provide a method, a solidifying device, a solidified radioactive waste, and a solidified material.

(Embodiment 4) Finally, a fourth embodiment will be described with reference to FIG. The fourth embodiment is basically similar to the third embodiment.
This is the same as the embodiment. The different point is that as shown in FIG. 11, non-combustible miscellaneous solid waste is made into a compressed mass 14 which is reduced in volume, non-combustible miscellaneous solid waste is made into a cured product after being melt-processed, or incinerated ash is made. After the pelletization, the cured product is put into the solidification container 1, and the paste is poured and solidified.

In this embodiment, the same effects as in the third embodiment can be expected.

[0076]

According to the present invention, it is possible to obtain a paste capable of forming a protective film for suppressing generation of hydrogen gas due to a reaction between an amphoteric metal contained in radioactive waste and a hydraulic solidifying material.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a radioactive waste treatment method according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an experimental result showing an effect of a protective film forming agent, and showing a temporal change of an amount of generated hydrogen when mixing an amphoteric metal and cement.

FIG. 3 is a characteristic diagram showing an experimental result showing an effect of a protective film forming agent, and showing a temporal change of an amount of generated hydrogen in an NaOH aqueous solution.

FIG. 4 is a characteristic diagram showing experimental results showing the effect of the agent for promoting a hydration reaction, and showing a change over time in the amount of hydrogen generated when an amphoteric metal and cement are mixed.

FIG. 5 is a characteristic diagram showing an influence of alkalinity of a solidifying material and showing a relationship between an alkali component content in cement and an amount of generated hydrogen.

FIG. 6 is a characteristic diagram showing the influence of the alkalinity of the solidified material and showing the relationship between the R ₂ O value and the amount of generated hydrogen.

FIG. 7 is a characteristic diagram showing the effect of alkalinity of the solidified material, and showing the relationship between the amount of added aggregate and the relative strength, evaluation function, and hydrogen generation amount of the solidified material.

FIG. 8 shows a second embodiment of the present invention, and is a configuration diagram of a solidification device suitable for solidifying incineration ash.

FIG. 9 shows a third embodiment of the present invention, and is a configuration diagram of a solidifying apparatus suitable for solidifying non-combustible miscellaneous solid waste.

FIG. 10 is a characteristic diagram showing the relationship between the fluidity of the solidifying material paste and the state of filling of the solidifying material.

FIG. 11 shows a fourth embodiment of the present invention, and is a configuration diagram of a solidifying apparatus suitable for solidifying a cured product such as noncombustible miscellaneous solid waste.

[Explanation of symbols]

1: solidification container, 2: kneading machine, 3: solidification material storage tank,
4, 8, 12, 16 ... fixed amount supply device, 5 ... water tank, 6
... Electromagnetic valve, 7 ... Chemical tank for forming protective film, 9 ... Shutter, 10 ... Stirring blade, 11 ... Incineration ash storage tank, 1
3. Exciting table, 14: Compressed mass, 15: Chemical tank for promoting hydration reaction.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B09B 3/00 C04B 22/16 Z C04B 22/08 24/20 22/16 28/02 24/20 G21F 9 / 36 511F 28/02 C04B 103: 60 G21F 9/36 511 111: 20 // C04B 103: 60 B09B 3/00 ZAB 111: 20 304Z (72) Inventor Masato Matsuda 1168 Moriyamacho, Hitachi City, Hitachi, Ibaraki Stock (72) Inventor Kenji Noshita 1168 Moriyama-cho, Hitachi City, Ibaraki Prefecture In-house Energy Research Laboratory Co., Ltd. (72) Inventor Jun Kikuchi 1168 Moriyama-machi, Hitachi City, Ibaraki Prefecture Nichido Corporation Inside the Energy Laboratory, Ltd. (72) Inventor Tatsuo Izumida 3-1-1, Sachimachi, Hitachi-City, Ibaraki Prefecture Inside the Hitachi Plant, Hitachi, Ltd. (72) Inventor Department Makoto Hitachi City, Ibaraki Prefecture Saiwaicho Third Street No. 1 in the No. 1 stock company Hitachi, Ltd. Hitachi Plant (72) inventor Yoshimasa Kiuchi Hitachi City, Ibaraki Prefecture Saiwaicho Third Street No. 2 No. 2 stock company Hitachi engineering in the service

Claims (3)

[Claims] 1. A hydraulic hardening material supplying means for supplying a hydraulic hardening material, a protective film forming agent supplying means for supplying a protective film forming agent for forming a protective film for suppressing hydrogen generation on the surface of an amphoteric metal, A water supply unit, the hydraulic solidifying material supplied from the hydraulic solidifying material supply unit, the protective film forming agent supplied from the protective film forming agent supplying unit, and water supplied from the water supplying unit. An apparatus for solidifying radioactive waste containing amphoteric metal, comprising: a kneading apparatus for kneading and discharging the produced paste. 2. A protective film forming agent for forming a protective film for suppressing hydrogen generation on the surface of an amphoteric metal, a protective film forming agent / hydraulic solidifying material supplying means for supplying a hydraulic solidifying material, and a water supplying means. Kneading the protective film forming agent and the hydraulic solidifying agent supplied from the protective film forming agent / hydraulic solidifying material supply unit, and the water supplied from the water supplying unit, and discharging the produced paste. An apparatus for producing a paste for solidifying radioactive waste containing amphoteric metal, comprising: a kneading apparatus. 3. The method according to claim 1, wherein the protective film forming agent is selected from inorganic phosphoric acid, neutral salt of inorganic phosphoric acid, organic phosphoric acid, neutral salt of organic phosphoric acid (phosphonate), polymerized phosphoric acid, and polymerized phosphoric acid. Salts, Silicon Polyphosphate, Silicic Acid, Neutral Salts of Silicic Acid, Polymerized Silicic Acid, Neutral Salts of Polymerized Silicic Acid, Nitrate, Inorganic Salts Containing Lithium, Organics Containing Polar Electron with High Electronegativity The method for treating radioactive waste according to claim 1 or 2, wherein the method is a substance selected from a compound and a chelating agent for an amphoteric metal.