JPH1172594A - Solidification method of radioactive waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively and stably solidify a radioactive waste without any danger by adding an inorganic expansion agent to a cement-based compression material increased in fluidity, kneading them, regulating amount of water, and solidifying it. SOLUTION: The solidification is performed with a hydraulic additive composed of a hydraulic inorganic solidifying material, sand, water, a fluidizing agent and inorganic expansion material. The hydraulic inorganic solidifying material is composed of a cement making a main component of calcium silicate or calcium aluminate. The inorganic expansion material is composed of bentonite, silica and one kind or two kinds or more of kaolinite, and 0.5-5 wt.% of the inorganic expansion material is compounded for the hydraulic inorganic solidifying material. A water reducing agent composed of a positive ion surface active agent can be used as the fluidizing agent. The compounding ratio of the hydraulic inorganic solidifying material and water, it and sand is 0.38 or larger and 0.4-1.0 respectively, and after the hydraulic inorganic solidifying material, sand and the fluidizing agent are added and kneaded, the inorganic expansion material is added.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stably solidifying miscellaneous solid radioactive waste generated during operation of a nuclear facility or dismantling of a nuclear facility using an inorganic material represented by cement. In particular, the present invention relates to a method for stably solidifying radioactive waste using a hydraulic admixture obtained by further adding an inorganic expander to a hydraulic inorganic solidifying material, sand, water, and a fluidizing agent.

[0002]

[Prior art branch] In radioactive material handling facilities such as nuclear power plants, various types of radioactive waste are generated during remodeling work to improve the facilities and maintain performance, but this radioactive waste is stabilized in a small space. Various treatment methods for volume reduction and stabilization have been studied.

[0003] Among these radioactive wastes, the waste liquid containing a radionuclide, ion exchange resin and the like are reduced in volume by a known appropriate method, and the reduced volume is mixed with a cement material or mixed with a plastic material. It is kneaded to form a solidified body, which is being buried and disposed. On the other hand, noncombustible miscellaneous solid waste is stored in a drum without being solidified.

By the way, when these facilities are to be dismantled in the future, various radioactive wastes will be generated. Most of these wastes have properties similar to those of the above-mentioned miscellaneous solid wastes. It is expected to be.

[0005] As a method of solidifying the waste, there is a filling and solidifying method in which the waste is stored in a container such as a drum and a cement-based solidifying material is poured into the container to solidify the waste.
A melt solidification method has been proposed in which incombustibles are incinerated, melted and solidified at a high temperature.

In particular, the filling and solidification method has been energetically studied because the process is simple, and is currently in the stage of practical use.

[0007] As such a filling and solidifying method, a method for preparing a waste for disposal of low-level radioactive waste (various solid wastes) (hereinafter referred to as “nuclear power”) issued by the Nuclear Environment Maintenance Center in July 1996 A specific method is proposed in “Environment Improvement Center Creation Technology”).

[0008] The solidifying material proposed by the technology of the Nuclear Environment Improvement Center is a cement-based material. Specifically, sand, water, and admixtures (high-performance water reducing agents and other additives) are mixed with cement. Mortar.

The reason for using such a mortar is that it is frequently used in the civil engineering and construction industries as a stable material for a long period of time and has a long track record. This is because the emission of radionuclides can be reduced. The technology developed by the Nuclear Environmental Management Center is designed to increase the fluidity of solidified materials, prevent material separation due to material density differences, and increase the strength after hardening, especially for the properties required for solidification of waste. It has also been proposed to mix various materials in the mortar besides cement as required. Although the composition of the substance added to such mortar is various, as a standard specification of electric power, Portland cement, blast furnace cement, sand, and the like specified in JIS R5210 and JIS R5211 are used.
High-performance water reducing agent (High-performance AE
Including water reducing agents).

Water is added to these materials and mixed to form a paste, which is used for filling and solidifying miscellaneous solid waste. These materials are combined with water and mostly inorganic particles. Of a homogeneous mixture of

[0011]

However, when the radioactive waste is solidified by the method proposed by the above-mentioned technology for preparing a nuclear environment maintenance center, there are the following problems.

That is, when radioactive wastes of various shapes generated in a nuclear power plant are filled and solidified, the solidified material needs to have high fluidity in order to make the wastes dense and solid. As a method of obtaining a solidified material having high fluidity, in the building and civil engineering industry, a water reducing agent (dispersant: a cationic surfactant, an anionic surfactant, a nonionic surfactant, etc.) is used as a fluidizing agent in mortar. Has been put to practical use.

According to the technology created by the Nuclear Environmental Management Center, the flowability of the solidifying material required for filling radioactive waste into a dense solidified body is determined by adding a high-performance water reducing agent (including a high-performance AE water reducing agent). In the case of the mortar described above, 16 seconds to 50 seconds is considered to be appropriate depending on the P funnel falling time specified by the Japan Society of Civil Engineers.

When a mortar having a high fluidity is used as described above, when the mortar hardens, a phenomenon called surplus water occurs, which is called bleeding, cement and sand, or water separates, and the mortar hardens. At this time, there is a problem that the solidified body shrinks and cracks are generated at the interface between the waste and the mortar due to the shrinkage of the mortar.

For this reason, an organic material having a water-retaining effect is added to the mortar material to reduce breathing, or aluminum is added to the mortar material to react the alkali produced when the cement is hydrated with the aluminum. A method has been developed in which hydrogen gas is generated to prevent shrinkage of the solidified body.

However, organic water retention materials are very expensive, and may be hydrolyzed by the alkali of cement to produce a substance which is liable to react with radionuclides. Careful material selection was required.

In the method of adding aluminum or the like, since powdered aluminum itself has an explosive property due to a thermite reaction, it must be designed very carefully in terms of the equipment configuration for use in a facility for solidifying radioactive waste.

Therefore, there has been a demand for the development of an additive which is safe, low-cost, has low bleeding, has excellent swelling properties, and has no reactivity with radionuclides when a fluidizing agent is used.

When the radioactive waste is stored in a 200-liter drum and the solidified material is filled, if the length of the waste is long, the amount of the waste that can be stored in the 200-liter drum can increases. If the length is too long, cracks may occur on the upper surface of the solidified body, and the problem is how much the solidification material should be filled.

[0020] The quality and properties of cement are specified by JIS, but this rule is provided because a structure originally using cement has predetermined strength characteristics and creep characteristics when cured. For this reason, it has been very difficult to obtain a P funnel falling time proposed by the technology for creating a nuclear environment maintenance center using a fluidizing agent, particularly a high-performance water reducing agent. That is, generally, the fluidity of cement and mortar is adjusted by a technician who fully understands the fluidity of the cement and mortar by evaluating each time the cement manufacturer or lot changes and slightly changing the amount of water. .

However, in the case of a nuclear power plant, the solidification operation is an operation in the radiation control area, and adjusting the fluidity of the solidified material while changing the amount of water reduces the amount of radioactive secondary waste generated. There was a problem and a problem that would lead to an increase in waste disposal costs. That is, it has been desired to develop a method for automatically obtaining a specified fluidity regardless of the cement used by any manufacturer.

The present invention has been made to solve such a conventional problem. The main object of the present invention is to have high fluidity when filling and solidifying various forms of radioactive waste generated in a nuclear power plant, It is an object of the present invention to provide a method of solidifying radioactive waste which has a small shrinkage upon curing, does not cause bleeding after curing, is relatively inexpensive, and is stable and has no danger. Another object of the present invention is to provide a method for solidifying radioactive waste that can automatically obtain a specified fluidity even when hydraulic inorganic solidifying materials having different properties are used.

[0023]

The above object is achieved by the present invention described below.

That is, in the method for solidifying radioactive waste according to claim 1, the radioactive waste is treated with a hydraulic inorganic solidifying material, sand, water,
It is characterized by being solidified by a hydraulic admixture comprising a fluidizing agent and an inorganic expanding material.

The solidification method of radioactive waste according to claim 2 is characterized in that the hydraulic inorganic solidifying material is made of cement containing calcium silicate or calcium aluminate as a main component.

In a third aspect of the present invention, the method for solidifying radioactive waste is characterized in that the inorganic expandable material comprises one or more of bentonite, silica and kaolinite.

According to a fourth aspect of the present invention, there is provided the method for solidifying radioactive waste according to the first or fourth aspect, wherein bentonite and / or
Alternatively, it is characterized in that an inorganic expander made of kaolinite is blended in an amount of 0.5 to 5% by weight with respect to the hydraulic inorganic solidified material.

According to a fifth aspect of the present invention, in the method for solidifying radioactive waste according to the first or third aspect, the inorganic expandable material comprising only silica is used in an amount of 8 to 2 with respect to the hydraulic inorganic solidified material.
It is characterized by being blended at 0% by weight.

According to a sixth aspect of the present invention, in the method for solidifying radioactive waste according to the first or third aspect, the bentonite comprises:
It is characterized in that an inorganic expanding material comprising at least two kinds of silica and kaolinite is blended in an amount of 1 to 15% by weight with respect to the hydraulic inorganic solidifying material.

According to a seventh aspect of the present invention, in the method for solidifying radioactive waste according to any one of the first to sixth aspects, the hydraulic inorganic solidifying material, the sand and the fluidizing agent are added to the water. And then kneading, and then adding the inorganic expanding material.

According to the invention of claim 8, in a container containing radioactive waste, a hydraulic admixture comprising a hydraulic inorganic solidifying material, sand, water, a fluidizing agent and an expanding material is filled and solidified. In this case, the hydraulic mixture is filled with a thickness of at least 2 cm or more from the uppermost end of the radioactive waste.

According to a ninth aspect of the present invention, in the method for solidifying radioactive waste according to any one of the first to eighth aspects, the mixing ratio (weight) of the water and the hydraulic inorganic solidifying material is 0.38.
It is characterized by the above.

According to a tenth aspect of the present invention, in the method for solidifying radioactive waste according to any one of the first to ninth aspects, the mixing ratio of the sand and the hydraulic inorganic solidifying material is 0.4 to 1.0.
It is characterized by the following.

The present inventors have conducted intensive studies, focusing on the fact that inorganic materials used in radionuclide disposal facilities do not adversely affect the migration behavior of radionuclides.
In order to solve the above problems, it has been found that a hydraulic inorganic solidifying material, sand, water, and a hydraulic admixture comprising a fluidizing agent can be solved by adding an inorganic expanding material, and the present invention has been achieved. .

As the hydraulic inorganic solidifying material used in the present invention, portland cement and blast furnace cement specified in JIS R5210 and JIS R5211 can be used.

[0036] Examples of the fluidizing agent useful in the present invention include:
A known water reducing agent composed of a cationic surfactant, an anionic surfactant, a nonionic surfactant or the like can be used. Particularly, a high-performance water reducing agent including a high-performance AE water reducing agent is suitable.

The inorganic expanding material used in the present invention includes:
The type that absorbs water in the crystal structure and expands the crystal, and the type that increases the volume by forming an amorphous hydrate by reacting with the alkali generated when the cement hydrates There is.

When these inorganic expanders are added to the mortar, the inorganic expanders enter into the gaps between the cement and sand when kneading water, cement and sand, and absorb the excess water and shrinkage during hydration of the cement. And, by this,
It functions to suppress the occurrence of breathing and reduce shrinkage. In addition, when the inorganic expander contains water or receives an alkaline stimulus, the inorganic expander is entangled with cement particles and sand, thereby suppressing the separation of the particles and reducing the material separation.

Among the inorganic expanders used in the present invention, bentonite and kaolinite are suitable as the former inorganic expanders which expand by containing water, and the latter are dissolved by alkalinity to take in water. Silica is suitable as an inorganic expanding material that becomes an amorphous substance. These are used in one kind or a combination of two or more kinds.

When bentonite and kaolinite are used alone or in combination as the inorganic expander, the compounding amount is suitably in the range of 0.5 to 5% by weight based on the hydraulic inorganic solidified material.

When silica alone is used as the inorganic expanding material, the amount of the silica is 8 to 10 parts with respect to the hydraulic inorganic solidifying material.
A range of 20% by weight is suitable.

When at least two kinds of bentonite, silica and kaolinite are used as the inorganic expander,
The compounding amount is suitably in the range of 1 to 15% by weight based on the hydraulic inorganic solidifying material.

If the amount of the inorganic expander is less than the above range, bleeding and material separation are likely to occur, and prevention of shrinkage tends to be insufficient. Conversely, if the amount of the inorganic expander is more than the above range, it is difficult to obtain fluidity, and it is likely to be necessary to add a large amount of water. In order to keep the fluidity of the entire mortar constant without variation, it is desirable to mix the inorganic expander in the material in advance as homogeneously as possible when preparing the mortar. For this purpose, a method of uniformly dispersing the inorganic expander under the condition that water is not added in advance is effective. However, this method requires that a powder mixer for mixing the materials be installed in the solidification facility.

According to the present invention, a mortar containing no inorganic expander is prepared and sufficiently fluidized, and then the inorganic expander is added, so that the inorganic expander can be used as a whole without using a powder mixer. And the fluidity is made uniform, and the effect of adding the inorganic expander can be effectively exhibited.

The long radioactive waste is cut into an appropriate length and solidified. According to experiments conducted by the present inventors, at least 2 cm or more from the top end of the radioactive waste. It has been found that if the hydraulic admixture is filled so as to have a thickness of, no problems such as cracking and roughening after solidification occur. This method is effective not only when using an inorganic expander but also when using an organic expander.

Therefore, it is desirable to cut the radioactive waste as long as possible within a range that satisfies this condition, to minimize the amount of solidified waste generated, and to improve workability. As described above, in the present invention, water and sand are added to the hydraulic inorganic solidifying material to obtain basic fluidity, and the fluidity is improved by adding a fluidizing agent. The difference in fluidity of the hydraulic admixture due to, for example, is eliminated, and the use of an inorganic expander reduces the shrinkage during curing, despite the use of a fluidizing agent, and does not cause bleeding after curing. Can be manufactured relatively inexpensively and without danger.

Further, according to the present invention, stable operation of the solidification system is possible, and the cost of treating radioactive waste is reduced.
That is, it can greatly contribute to the improvement of operation time and the reduction of the number of workers involved in solidification.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments.

(First Embodiment) [Corresponding to Claims 1 to 3] Table 1 shows that a hydraulic inorganic solidifying material containing Portland cement or alumina cement as a main component, sand, a fluidizing agent and an inorganic expanding material. Examples 1 to 8 of the invention added,
The composition of Comparative Examples 1 and 2 in which no inorganic expander is added is shown in parts by weight.

With respect to these, the breathing water generated when the hydraulic mixture was cured and the expansion coefficient of the hydraulic mixture during curing were measured.

In both cases, the measuring method was based on the Japan Society of Civil Engineers, "Method of measuring breathing rate and expansion rate of mortar injected with prepacked concrete".

As the index of the fluidity of the hydraulic admixture filled with radioactive waste, the flow down time of a P funnel specified by the Japan Society of Civil Engineers “Testing method for fluidity of injected mortar of prepacked concrete” was used. The fluidity of the hydraulic admixture was adjusted so as to be about 25 to 30 seconds in the flow time of the P funnel. Table 1 also shows the measurement results.

As is clear from Table 1, the breathing rates of Comparative Examples 1 and 2 in which no inorganic expander was added to the hydraulic admixture were 2.6% and 1.6%, and the expansion rate upon curing was -2. .
The breathing rates of Examples 1 to 8 are 0.2% to 0.4% and the expansion rates are -0.2% and -1.1%, respectively.
% To -0.7%.

[0054]

[Table 1] (Second Embodiment) [Corresponding to Claims 4 to 6] A solidified body was produced in the same manner as in Example 1 except that the type and the amount of the inorganic expander were changed as shown in FIGS. .
The figure shows the measurement results of the rate of occurrence of breathing and the rate of expansion. Both formulations are JIS R as hydraulic cement.
Use of B-type blast-furnace cement specified in 5211 (Blast-furnace cement) and mixing of sand, water, and an organic fluidizer such that the fluidity of the hydraulic admixture becomes 25 to 30 seconds in the flow time of the P funnel. It was adjusted.

The addition ratio of the inorganic expanding material in FIGS. 1 to 3 is represented by (weight of inorganic expanding material / weight of hydraulic inorganic solidifying material).

From the results shown in FIGS. 1 to 3, when the inorganic expander is composed of only bentonite and kaolinite, the addition ratio is 0.5% to 5% by weight with respect to the hydraulic inorganic solidified material. In the case of using only silica, the addition ratio is 3% to 20% by weight with respect to the hydraulic inorganic solidifying material, whereby the breathing rate is suppressed to 1% or less, and the expansion rate is -1% (that is, the contraction rate is (1% or less).

FIG. 4 shows the results of the measurement of the rate of bleeding and the rate of expansion when 0.25% of bentonite, 0.25% of kaolinite, and silica were added as the inorganic expander, mixed and solidified. Also in this example, the hydraulic cement used was a Class B blast furnace cement specified in JIS R5211 (blast furnace cement). The flowability of the solidified material was adjusted from 25 seconds to 30 seconds in the flow time of the P funnel.

In the case where a plurality of inorganic expanders are mixed as described above, if the addition ratio of the inorganic expander is in the range of 1% to 15% by weight with respect to the hydraulic inorganic solidified material, the breathing rate is 1%. It can be seen that the pressing and expansion rate can be reduced to -1% (that is, the shrinkage rate is 1% or less). Silica is
If the mixing amount is not increased, the effect of improving the breathing rate and the expansion rate is small, but it can be seen that by adding a small amount of bentonite or kaolinite, these properties can be greatly improved with a small amount of the inorganic expansion material added.

As shown in FIGS. 1 to 4, when the inorganic expander is composed of only bentonite and kaolinite, the addition ratio is 0.5% to 5% by weight based on the hydraulic inorganic solidified material, and the inorganic expander is composed of only silica. In this case, the addition ratio is preferably in the range of 3% to 20% by weight based on the hydraulic inorganic solidifying material.

Further, the inorganic expander is bentonite, silica,
When at least two kinds of kaolinite are used, the addition ratio of the inorganic expanding material is preferably in the range of 1% to 15% by weight based on the hydraulic inorganic solidifying material.

(Third Embodiment) [Corresponding to Claim 7] With respect to the hydraulic admixture composition shown in Formulation 1 in Table 2, a method of adding an inorganic expander was examined.

[0062]

[Table 2] In Example 9, a fluidizer was added to water while the mortar kneader was operating, and then cement, sand, and an inorganic expander were added and kneaded for 5 minutes. In Example 10, after the fluidizing agent was added to water while the mortar kneader was operating, cement and sand were added and kneaded for 5 minutes, and then the inorganic expander was added. The breathing rate and the expansion rate were measured.
Table 3 shows the results.

[0063]

[Table 3] From the results in Table 3, it can be seen that the occurrence of the breathing rate is smaller in Example 10.

From the above, it was confirmed that the addition of the inorganic expander after the addition of the hydraulic inorganic solidifying material, the sand, and the fluidizing agent to water, followed by kneading, was confirmed.

(Fourth Embodiment) [Corresponding to Claim 8] Using a solidifying material composition shown in Table 2, a mortar kneader is operated, and after adding a fluidizing agent to water, cement, sand,
The expanding material was added and kneaded for 5 minutes. In this test, the test was performed by the method of Example 9 in which the occurrence of the breathing rate was large. The prepared hydraulic mixture was filled and solidified in a 200-liter drum containing simulated waste. Using the difference between the filling surface of the hydraulic mixture and the upper end of the simulated waste as a parameter, the roughness of the upper surface of the manufactured solidified body was observed. Table 4 shows the results.

[0066]

[Table 4] It can be seen that if the filling surface of the hydraulic admixture is 2 cm or more from the upper end of the simulated waste, it is possible to prevent the surface of the solidified body from being roughened due to a slight shrinkage when the hydraulic admixture is cured.

From the above results, when the radioactive waste is solidified by filling the container containing the radioactive waste with the hardening inorganic solidifying material, the sand, the water, the fluidizing agent, and the expanding material, It has been confirmed that it is effective to fill the solidification material at least 2 cm or more above the uppermost end of the radioactive waste.

(Fifth Embodiment) [Corresponding to Claims 9 to 10] JIS R5210 (Portland cement) and J
The cement of each company of IS R5211 (blast furnace cement) standard was procured, and a hydraulic admixture of the same composition using the cement of each company was produced. Note that the same lot was used for the sand, the fluidizing agent, and the inorganic expanding material. Using the water-cement ratio (water weight / cement weight) and the sand-cement ratio (sand weight / cement weight) as parameters, the flow down time of the P funnel was measured.

The measurement results are shown in FIG. 5 and FIG. As shown in FIG. 5, there is a marked difference in fluidity depending on the cement supplier even under the same JIS standard. However, if the water-cement ratio is adjusted to about 0.38 or more, regardless of the cement supplier, the target The range of the P funnel flow time (16 seconds to 50
Second). Also, from the results in FIG. 6, if the sand-cement ratio is adjusted to be in the range of 0.4 to 1.0, the target P-rotation time (1
8 seconds to 50 seconds).

From the above results, as a method of obtaining a constant fluidity regardless of the cement supplier, the water-cement ratio was set to 0.1.
It was found that setting the ratio to 38 or more and the ratio of sand cement to 0.4 to 0.8 are effective.

[0071]

As described above, according to the method for solidifying radioactive waste of the present invention, an inorganic expander is added to various cement-based solidified materials having improved fluidity, and the mixture is kneaded and mixed with water. By adjusting the amount of the waste, the radioactive miscellaneous solid waste can be solidified precisely and safely. In addition, by controlling the injection amount of the solidifying material during the solidification operation, a solidified body having a good surface condition can be manufactured. This method provides a stable waste of radioactive waste, and contributes to work efficiency and cost reduction.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between an addition ratio of a bentonite expander as an inorganic expander, a breathing rate and an expansion rate according to a second embodiment of the present invention.

FIG. 2 is a graph showing a relationship between an addition ratio of a kaolinite expander as an inorganic expander, a breathing rate and an expansion rate according to a second embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the addition rate of a silica expander as an inorganic expander according to a second embodiment of the present invention, the breathing rate and the expansion rate.

FIG. 4 is a graph showing a relationship between an addition ratio of an expanding material obtained by mixing bentonite, kaolinite and silica as an inorganic expanding material according to a second embodiment of the present invention, and a breathing rate and an expansion rate.

FIG. 5 is a graph showing a relationship between a water-cement ratio and fluidity when using cements of different manufacturers according to the fifth embodiment of the present invention.

FIG. 6 is a graph showing a relationship between a sand-cement ratio and fluidity when using cements of different manufacturers according to the fifth embodiment of the present invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Noriko Suzuki, Inventor, 8-8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside the Toshiba Yokohama Office (72) Inventor Noriyuki Nankata 8-Shin-Sugitacho, Isogo-ku, Yokohama-shi, Kanagawa, Japan (72) Inventor Tomoharu Ishii 66-2 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside Toshiba Engineering Co., Ltd. (72) Fumio Tomita 66-2 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Engineering Co., Ltd.

Claims (10)

[Claims] 1. A radioactive waste, comprising: a hydraulic inorganic solidifying material;
A method for solidifying radioactive waste, comprising solidifying with a hydraulic admixture comprising sand, water, a fluidizing agent and an inorganic expander. 2. The method for solidifying radioactive waste according to claim 1, wherein said hydraulic inorganic solidifying material is made of cement containing calcium silicate or calcium aluminate as a main component. 3. The method for solidifying radioactive waste according to claim 1, wherein the inorganic expanding material comprises one or more of bentonite, silica, and kaolinite. 4. An inorganic expandable material comprising bentonite and / or kaolinite, wherein said inorganic expandable material is
The method for solidifying radioactive waste according to claim 1 or 3, characterized in that it is contained in an amount of 0.5 to 5% by weight. 5. The solidification of radioactive waste according to claim 1, wherein the inorganic expandable material composed of silica alone is blended in an amount of 8 to 20% by weight based on the hydraulic inorganic solidified material. Method. 6. The method according to claim 1, wherein 1 to 15% by weight of the inorganic expandable material of at least two of bentonite, silica and kaolinite is blended with respect to the hydraulic inorganic solidified material. Or the method for solidifying radioactive waste according to 3. 7. The method according to claim 1, wherein the inorganic expandable material is added to the water after the hydraulic inorganic solidifying material, the sand and the fluidizing agent are added and kneaded. The method for solidifying radioactive waste according to claim 1. 8. Filling a container containing radioactive waste with a hydraulic admixture composed of a hydraulic inorganic solidifying material, sand, water, a fluidizing agent and an expansive material, and solidifying the radioactive waste. A method for solidifying radioactive waste, comprising filling the hydraulic mixture with a thickness of at least 2 cm or more from the top end of the radioactive waste. 9. The method for solidifying radioactive waste according to claim 1, wherein a mixing ratio (weight) of the water and the hydraulic inorganic solidifying material is 0.38 or more. 10. The mixing ratio of the sand and the hydraulic inorganic solidifying material is set to 0.4 to 1.0.
The method for solidifying radioactive waste according to any one of claims 9 to 10.