JP5308252B2 - Solidifying agent and solidification processing method - Google Patents

Description

  The present invention relates to a solidifying agent used for solidifying a nitrate solution, a method for solidifying a nitrate solution, and a solidified body treated using the solidifying agent.

Radioactive liquid waste containing nitrates from nuclear facilities such as nuclear power plants and nuclear fuel reprocessing plants is filled into drums, mixed with cement, solidified, and then buried in a dedicated facility. The cement solidification treatment method includes, for example, a method in which radioactive waste is treated with alkali and then solidified by mixing blast furnace slag, granulated blast furnace slag and / or converter slag, ultrafine powder material, and dispersant. There is known a method of solidifying using a solidified material, a method of solidifying using a solidified material consisting of blast furnace granulated slag, silica fume, wollastonite, slaked lime (Non-patent Document 1, Patent Document 1, (See Patent Document 2 and Patent Document 3). It is said that the fluidity of the cement solid body is required to be 250 mm or more at a 15-point flow value, and the compressive strength is 10 N / mm ² or more at a material age of 28 days (see Non-Patent Document 1).

Tadashi Sasaki, Mamoru Numata, Yasuyasu Suzuki, Miwa Kubo, Comparative evaluation test of cement solidified material, Nuclear Fuel Cycle Development Organization Contract Report, JNC TJ8430 2002-002 (2003.2)

JP 63-205600 A JP-A-62-238499 Japanese Patent Laid-Open No. 8-179095

  However, the features of the present invention are not described below. Since the present invention does not use sodium hydroxide or slaked lime that exhibits strong alkalinity, there is no risk that an operator touches sodium hydroxide or slaked lime during handling to cause chemical injury. In the present invention, since it is not necessary to add water when preparing an aqueous solution, it is not necessary to install a dedicated tank, and the processing capacity of radioactive waste is improved. In particular, sodium hydroxide is difficult to store for a long time because it exhibits deliquescence, and it is difficult to use it as a solidifying agent because it is used in advance as an aqueous solution.

The present invention is a solidifying agent having the following features (1) to (4):
(1) The solidifying agent contains a cement composition containing 100 parts of a hydraulic composition, 0.5-8 parts of a polycarboxylate-based water reducing agent, and 0.05-0.5 parts of sucrose .
(2) The cement composition contains calcium aluminosilicate.
(3) the chemical composition of the calcium aluminosilicate, CaO, in the sum of Al ₂ O _3, SiO _2, CaO is 35-55 parts Al ₂ O ₃ is 20 to 45 parts of a SiO ₂ 5 to 30 parts about.
(4) The solidifying agent is used for solidifying nitrate solution.
(2) The cement composition is the solidifying agent containing 1 to 30 parts of silica fume with respect to 100 parts of calcium aluminosilicate , and (2) the cement composition is 50 to 300 with respect to 100 parts of calcium aluminosilicate. a solidifying agent comprising a part of the slag, the solid concentration of the nitrate solution is 15 to 40% water powder ratio of the cement composition is a solid agent is 30 to 120%, more water It is the solidifying agent containing 0.05 to 45 parts of a curing agent in terms of solid content with respect to 100 parts of the hard composition , and the chemical composition is CaO, Al ₂ O ₃ , SiO _{2 in} the total, CaO is 35 to 55 part, Al ₂ O ₃ is 20 to 45 parts, hydraulic composition 100 parts of SiO ₂ contains calcium aluminosilicate 5 to 30 parts of polycarboxylate-based water reducing agent 0.5-8 parts sucrose 0.05 the cement composition containing 0.5 parts of mixed nitrates solution, a solidification method comprising solidified, chemical group But, CaO, in the sum of _{Al 2 O 3, SiO 2,} CaO is 35-55 parts, Al ₂ O ₃ is 20 to 45 parts, SiO ₂ is hydraulic composition containing calcium aluminosilicate 5 to 30 parts A cement composition containing 100 parts of a product, polycarboxylate-based water reducing agent 0.5-8 parts and 0.05-0.5 parts of sucrose and a curing agent, mixed with a nitrate solution and solidified, The cement composition is the solidification method containing 1 to 30 parts of silica fume with respect to 100 parts of calcium aluminosilicate , and the cement composition contains 50 to 300 parts of slag with respect to 100 parts of calcium aluminosilicate. The solid content concentration of the nitrate solution is 15 to 40%, the water-powder ratio of the cement composition is 30 to 120%, and the amount of the curing agent used is the hydraulic composition 100. a solid treatment method is 0.05 to 45 parts in terms of solid content relative to the parts, the calcium a A vitrification ratio of amino silicate is 70% or more solid processing method, Blaine specific surface area of the calcium aluminosilicate is solid treatment method is 2000 cm ² / g or more, and solidified by solid treatment method It is a solidified body.

  The effect of the present invention is to provide a solidifying agent having a large treatment capacity for radioactive liquid waste containing nitrate. The effect of the present invention is to provide a cement solidification treatment method for radioactive waste having a large treatment capacity for radioactive waste liquid containing nitrate.

  Hereinafter, the present invention will be described in detail. In the present invention, “parts” and “%” are based on mass unless otherwise specified.

  The solidifying agent of the present invention contains a cement composition. The solidifying agent of the present invention may contain a curing agent and a curing agent solution as necessary. The cement composition of the present invention contains a hydraulic composition. The cement composition of this invention may also contain a dispersing agent and saccharides as needed. The hydraulic composition of the present invention contains calcium aluminosilicate. The hydraulic composition of the present invention may contain slag and silica fume as necessary.

The term “calcium aluminosilicate” as used in the present invention is a general term for self-hardening substances that are mainly composed of CaO, Al ₂ O ₃ , and SiO ₂ and are obtained by heat treatment in a kiln or an electric furnace. Next, a method for producing calcium aluminosilicate will be described.

The CaO raw material used for the production of calcium aluminosilicate is not particularly limited, and examples thereof include quick lime (CaO), slaked lime (Ca (OH) ₂ ), limestone (CaCO ₃ ) and the like.

The Al ₂ O ₃ raw material is not particularly limited, and examples thereof include alumina, bauxite, diaspore, feldspar, and clay.

The SiO ₂ raw material is not particularly limited, and examples thereof include quartzite, quartz sand, quartz, diatomaceous earth, and the like.

  After blending these raw materials in a predetermined ratio, calcium aluminosilicate is produced by melting in an electric furnace, a high-frequency furnace, a kiln furnace, etc., rapidly cooling, and vitrifying. The melting temperature is preferably 1500 ° C. or higher, and more preferably 1600 to 1800 ° C. If it is lower than 1500 ° C, the raw material may not be sufficiently melted or vitrification may not be possible due to rapid cooling.

  The vitrification rate of calcium aluminosilicate is preferably 70% or more, more preferably 80% or more, and most preferably 90% or more. If the vitrification rate is less than 70%, sufficient hydration activity may not be obtained. The vitrification rate was measured by the X-ray diffraction Rietveld method shown below. A predetermined amount of an internal standard substance such as aluminum oxide or magnesium oxide is added to the crushed sample, and after sufficient mixing in an agate mortar, powder X-ray diffraction measurement is performed. Analyze the measurement results with quantitative software to determine the vitrification rate. As the quantitative software, “SIROQUANT” manufactured by Sietronics can be used.

The calcium aluminosilicate of the present invention is produced by grinding a clinker. Calcium aluminosilicate has a chemical composition of CaO, Al ₂ O ₃ , SiO ₂ total 100 parts, CaO 35-55 parts, Al ₂ O ₃ 20-45 parts, SiO ₂ 5-30 parts Preferably, CaO contains 38 to 52 parts, Al ₂ O ₃ contains 25 to 41 parts, and SiO ₂ contains 10 to 25 parts. Outside this range, sufficient fluidity, strength development, and dimensional stability may not be obtained, or hydration exotherm may increase.

As long as the properties of the calcium aluminosilicate of the present invention are not impaired, unreacted CaO (free calcium oxide), unreacted Al ₂ O ₃ , dicalcium silicate (2CaO · SiO ₂ ), gehlenite (2CaO · Al ₂ O) It is also possible to contain a small amount of ₃ · SiO ₂ ).

  The method for pulverizing the calcium aluminosilicate clinker is not particularly limited, and examples thereof include a method using a pulverizer such as a roller mill, a jet mill, a tube mill, a ball mill, and a vibration mill.

The particle size of the calcium aluminosilicate obtained by pulverizing these mills is preferably from 2000 cm ² / g or more in Blaine specific surface area, more preferably at least ^{4000cm 2 / g, 6000cm 2 /} g being most preferred. If it is less than 2000 cm ² / g, the hydration activity may be insufficient and the strength may be insufficient, or breathing may occur when a kneaded product is prepared.

  The present invention can also contain slag in terms of improving strength and fluidity.

Slag refers to a non-metallic substance produced by melting mineral raw materials. Examples of the slag include blast furnace slag and converter slag. Among these, blast furnace slag is preferable because of its great effect. The particle size of the slag, preferably 2000 cm ² / g or more in Blaine specific surface area, more preferably at least ^{4000cm 2 / g, 6000cm 2 /} g being most preferred. If it is less than 2000 cm ² / g, the hydration activity may be insufficient and the strength may be insufficient, or breathing may occur when a kneaded product is prepared.

  The amount of slag used is preferably 50 to 300 parts, more preferably 40 to 250 parts, and most preferably 80 to 150 parts with respect to 100 parts of calcium aluminosilicate. If it is less than 50 parts, the setting time may be shortened depending on the composition of the calcium aluminosilicate, and if it exceeds 300 parts, the setting time may be long, or the long-term strength may not be improved.

  The present invention can contain silica fume in that the long-term strength is improved.

Silica fume refers to spherical ultrafine particles of vitreous silica contained in waste gas generated in the process of producing silicon, ferrosilicon, silicon alloy and the like. The particle size of the silica fume is preferably 100000 ² / g or more in BET specific surface area, 130000cm ² / g or more is more preferable. If it is less than 100000 cm ² / g, the hydration activity may be insufficient and the strength may be insufficient, or breathing may occur when a kneaded product is prepared.

  The amount of silica fume used is preferably 1 to 30 parts, more preferably 5 to 15 parts, per 100 parts of calcium aluminosilicate. If the amount is less than 1 part, the strength may not be increased. If the amount exceeds 30 parts, the initial strength may be reduced.

  In the present invention, a dispersant can be used in that the dispersibility of calcium aluminosilicate, slag, and silica fume is improved in a waste liquid containing nitric acid.

  A dispersing agent refers to an agent that acts to individually disperse particles in water. Examples of the dispersant include a naphthalene-based dispersant, a melamine-based dispersant, an aminosulfonic acid-based dispersant, a polycarboxylic acid-based dispersant, and a polyether-based dispersant. In these, a polycarboxylate type water reducing agent is preferable at a point with a big effect.

  The amount of the dispersant used is preferably 0.1 to 8 parts, more preferably 0.5 to 5 parts, and more preferably 1 to 2 parts with respect to 100 parts of the hydraulic composition. If it is less than 0.1 part, the dispersibility may not be improved and the filling rate may decrease, and if it exceeds 8 parts, the setting may be delayed.

  In the present invention, saccharides can be used in terms of adjusting the setting time.

  Saccharides are carbohydrates and refer to monosaccharides, disaccharides, polysaccharides, and the like. Examples of the saccharide include monosaccharide fructose, glucose, brain sugar, disaccharide sucrose, maltose, and lactose. Among these, sucrose is preferable because of its great effect.

  The amount of saccharide used is preferably 0.05 to 0.5 part, more preferably 0.1 to 0.3 part with respect to 100 parts of the hydraulic composition. If it is less than 0.05 part, the setting may be accelerated, and if it exceeds 0.5 part, the setting may be delayed.

  The present invention can contain a curing agent in that the strength is improved.

  Examples of the curing agent include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide. Among these, alkali metal hydroxides are preferable because they are highly effective.

  The curing agent can be used as a curing agent solution dissolved in water. For example, a premixed hardener solution is mixed with the cement composition. The solid content concentration of the curing agent solution is preferably 5 to 15%, more preferably 8 to 12%. If it is less than 5%, the filling rate may decrease, and if it exceeds 15%, there may be a momentary setting during kneading.

  The amount of the curing agent used is preferably 0.05 to 45 parts, more preferably 0.5 to 10 parts, further preferably 0.8 to 5.0 parts, and most preferably 1.5 to 3.0 parts in terms of solid content with respect to 100 parts of the hydraulic composition. . If it is less than 0.05 parts, the compression strength may not be improved, and if it exceeds 45 parts, there may be a momentary setting.

  In the present invention, a cement composition, a nitrate solution, and a curing agent are mixed as necessary. By mixing these, the nitrate solution can be solidified.

  The nitrate solution refers to a solution containing nitrate. Examples of the nitrate solution include a radioactive waste solution containing nitrate, a nitric acid waste solution generated from a semiconductor manufacturing factory, and the like. Examples of the nitrate include alkali metal nitrates such as sodium nitrate and potassium nitrate. Among these, alkali metal nitrates are preferable because they are highly effective.

  The solid concentration of the nitrate solution is preferably 15 to 40%, and more preferably 17 to 37%. If it is less than 15%, there are cases where there is a lot of breathing and the compression strength is low, and if it exceeds 40%, the flow value may be low.

  The water-powder ratio of the cement composition is preferably 120% or less, more preferably 100% or less, and most preferably 85% or less from the viewpoint of great effect. The lower limit of the water powder ratio is preferably 30% or more, more preferably 45% or more, and most preferably 60%. Here, water contains the water in nitrate solution. Here, the powder refers to a hydraulic composition. The water / powder ratio water contains water derived from the curing agent solution.

  The solidification treatment method of the present invention includes Portland cement, water reducing agent, high performance water reducing agent, AE water reducing agent, fluidizing agent, thickening agent, rust preventive agent, antifreezing agent, shrinkage reducing agent, setting modifier, silica, alumina , Limestone fine powder, colemanite, zirconia, boron carbide, bentonite and other clay minerals, hydrotalcite and other anion exchangers, vinylon fiber, acrylic fiber, carbon fiber and other fibrous materials such as one or more of the present invention Can be used as long as the purpose of the above is not impaired.

  Calcium aluminosilicates having the compositions shown in Table 1 were prepared. A cement composition was prepared by mixing calcium aluminosilicate, slag, silica fume, dispersant, and sugar in the amounts shown in Table 2. A cement solidified body was prepared by mixing the cement composition and the hardener solution having the composition shown in Table 2. The hardener solution was prepared by mixing a hardener and water in advance with a cement composition. The results are shown in Table 2.

(Materials used)
Calcium aluminosilicates a1 to c6: After mixing and crushing CaO raw material, Al ₂ O ₃ raw material and SiO ₂ raw material so as to have the composition of a1 to c6 in Table 1, put them in a platinum dish at 1650 ° C for 1 hour Melted. After melting, the platinum dish containing the sample was placed on a water bath and rapidly cooled to prepare a sample. The sample was pulverized to a brain specific surface area of 6000 cm ² / g using a pulverizer.
CaO raw material: CaO, manufactured by Kanto Chemical Co., Ltd., reagent grade
Al ₂ O ₃ raw material: Al ₂ O ₃ , manufactured by Kanto Chemical Co., Ltd., reagent grade
SiO ₂ raw materials: SiO _2, manufactured by Kanto Chemical Co., Inc., special grade reagent slag: blast furnace slag, a commercially available product, Blaine specific surface area of 6000cm ² / g, granulated blast furnace slag silica fume: a commercially available product, Blaine specific surface area 130000cm ² / g
Hardener: Sodium hydroxide, manufactured by Kanto Chemical Co., Ltd., reagent grade dispersant: Polycarboxylate-based water reducing agent, commercially available saccharides: manufactured by Kanto Chemical Co., Inc., reagent, sucrose simulated waste liquid: 100 parts of pure water and 45 parts of sodium nitrate Simulated waste liquid sodium nitrate prepared by mixing and dissolving: Kanto Chemical Co., reagent grade

(Measuring method)
Blaine specific surface area: measured using a Blaine air permeation device specified in JIS R 5201.
Flow test: A kneaded material was prepared according to JIS R 5201-1997 “Cement physical test method”, and the 15-point flow value immediately after kneading was measured.
Compressive strength test: According to JIS R 5201-1997 “Cement physics test method”, a 40 mm x 40 mm x 160 mm molar specimen was prepared, sealed in a plastic bag, cured at 90 ° C for 1 day, and 28 Cured at 20 ° C until day. Thereafter, the compressive strength on the 28th day was measured.
Filling ratio: A mixture of cement composition, hardener solution and simulated waste liquid was filled into a cylindrical container having an inner diameter of 5 cm and a depth of 10 cm. According to the following formula, a value obtained by dividing the mass of the mixture by the volume of the cylindrical container as a percentage was defined as a filling rate.
Filling rate (%) = (mass part of simulated waste liquid) / (mass part of cement composition + mass part of curing agent solution + mass part of simulated waste liquid) × 100 (%)

  As shown in Table 1, when the solidifying agent of the present invention is used, even if the amount of sodium hydroxide used is reduced by setting the chemical composition of the calcium aluminosilicate to an appropriate range, sodium hydroxide is used. Even without this, it can be seen that a solidified cement having excellent fluidity and strength can be obtained.

  In Experiment No. 1-1 in Table 2, a solidified body was produced in the same manner as in Example 1 except that the type of calcium aluminosilicate and the vitrification rate were changed. The results are shown in Table 3.

  As shown in Table 3, when the solidifying agent of the present invention is used, by making the vitrification rate of calcium aluminosilicate within an appropriate range, it is excellent in fluidity and strength development without using sodium hydroxide. It turns out that a cement solidified body is obtained.

  A solidified body was produced in the same manner as in Example 1 except that the vitrification rate of calcium aluminosilicate was changed in Experiment No. 1-1 in Table 2. The results are shown in Table 4.

  As shown in Table 4, when the solidifying agent of the present invention is used, it is excellent in fluidity and strength development without using sodium hydroxide by adjusting the Blaine specific surface area of calcium aluminosilicate to an appropriate range. It turns out that a cement solidified body is obtained.

  The solidifying agent of the present invention can be used for a cement solidification treatment method of radioactive liquid waste containing nitrate and a cement solidified body treated using the method. The solidifying agent of the present invention has an effect even if, for example, the amount of sodium hydroxide or slaked lime showing strong alkalinity is reduced, or sodium hydroxide or slaked lime showing strong alkalinity is not used. Is expensive.

Claims (13)

A solidifying agent having the following features (1) to (4).
(1) The solidifying agent contains a cement composition containing 100 parts of a hydraulic composition, 0.5-8 parts of a polycarboxylate-based water reducing agent, and 0.05-0.5 parts of sucrose .
(2) The cement composition contains calcium aluminosilicate.
(3) the chemical composition of the calcium aluminosilicate, CaO, in the sum of Al ₂ O _3, SiO _2, CaO is 35-55 parts Al ₂ O ₃ is 20 to 45 parts of a SiO ₂ 5 to 30 parts about.
(4) The solidifying agent is used for solidifying nitrate solution. (2) The solidifying agent according to claim 1, wherein the cement composition contains 1 to 30 parts of silica fume with respect to 100 parts of calcium aluminosilicate . (2) The solidifying agent according to claim 1 or 2, wherein the cement composition contains 50 to 300 parts of slag with respect to 100 parts of calcium aluminosilicate . The solidifying agent according to any one of claims 1 to 3, wherein a solid content concentration of the nitrate solution is 15 to 40%, and a water powder ratio of the cement composition is 30 to 120%. Furthermore, the hardening | curing agent of any one of Claims 1-4 which contains 0.05-45 parts hardening | curing agent in conversion of solid content with respect to 100 parts of hydraulic compositions . Water containing calcium aluminosilicate having a chemical composition of CaO, Al ₂ O ₃ , SiO ₂ , CaO 35-55 parts, Al ₂ O ₃ 20-45 parts, SiO ₂ 5-30 parts A solidification method comprising solidifying a cement composition containing 100 parts of a hard composition, 0.5-8 parts of a polycarboxylate-based water reducing agent and 0.05-0.5 parts of sucrose with a nitrate solution. Water containing calcium aluminosilicate having a chemical composition of CaO, Al ₂ O ₃ , SiO ₂ , CaO 35-55 parts, Al ₂ O ₃ 20-45 parts, SiO ₂ 5-30 parts A solidification method comprising solidifying a cement composition containing 100 parts of a hard composition, 0.5 to 8 parts of a polycarboxylate-based water reducing agent and 0.05 to 0.5 part of sucrose and a nitrate solution. The solidification processing method according to claim 6 or 7, wherein the cement composition contains 1 to 30 parts of silica fume with respect to 100 parts of calcium aluminosilicate . The solidification processing method according to any one of claims 6 to 8, wherein the cement composition contains 50 to 300 parts of slag with respect to 100 parts of calcium aluminosilicate . The solid content concentration of the nitrate solution is 15 to 40%, the water-powder ratio of the cement composition is 30 to 120%, and the use amount of the curing agent is in terms of solid content with respect to 100 parts of the hydraulic composition. It is 0.05-45 parts, The solidification processing method of any one of Claims 7-9. The vitrification rate of calcium aluminosilicate is 70% or more, The solidification processing method of any one of Claims 6-10. The solidification processing method according to any one of claims 6 to 11, wherein the calcium aluminosilicate has a specific surface area of 2000 cm ² / g or more. Ri Na solidified by solidification method according to any one of claims 6-12, fluidity 250mm or more 15 RBI flow value, the compressive strength is solidified showing a 10 N / mm ² or more at an age of 28 days body.