JPH10197691A - Solidifying material for radioactive waste liquid and method for solidifying-processing radioactive waste liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable solidification of waste liquid containing sodium sulfate, and establish the solidification processing method of radioactive waste liquid containing sodium sulfate by mixing, heating and enriching radioactive waste liquid containing sodium sulfate and alkali earth metal hydroxide, and kneading, curing and solidifying a solid component except for alkali earth hydroxide. SOLUTION: Solidification material contains alkali earth metal hydroxide of Sr, Ba, Ca and the like, particularly hydroxide of Ba and Ca is preferable. Radioactive waste liquid containing sodium sulfate can be solidified and processed by mixing, kneading, curing and solidifying the solidification material in radioactive waste liquid containing sodium sulfate as it is, but furthermore, at first, alkali earth metal hydroxide is mixed in waste liquid, hydroxide of alkali earth metal is reacted with sodium sulfate, and after reaction, the solidification except for alkali earth metal is charged and kneaded. NaOH is produced by reaction, in the solidification material, and hardening stimulant addition is not needed otherwise. A solidifier can be obtained for 1-2 weeks after the solidification material except alkali earth metal is added, and kneaded, and solidification material excellent in water resistance can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solidifying material and a solidifying method for solidifying a waste liquid containing sodium sulfate discharged from a nuclear power plant or a nuclear research facility.

[0002]

2. Description of the Related Art Most radioactive liquid waste containing sodium sulfate is generated from nuclear power plants. As a method for solidifying this radioactive waste liquid, a cement solidification method and a plastic solidification method are known.

[0003] It is not only important to secure storage space in a facility, but also indispensable to land storage, which is one of final disposal, in order to reduce the volume of radioactive waste generated from a nuclear power plant or the like and solidify it. Factors.

As one of the methods for reducing the volume of radioactive waste, BWR (Boiling Water React) is used.
or) The waste of the concentrated waste liquid (mainly sodium sulfate) and the slurry of the powdery ion exchange resin, which are the main wastes generated from the plant, are dried and powdered to remove water, which occupies most of the volume of radioactive waste, and Pelletization or powdering methods are being studied.

[0005] A typical method for solidifying these pellets or powders is solidification using a plastic or an inorganic material, and a cement solidified material having high nuclide retention performance has attracted attention. However, in the conventional solidification of cement, a solidified body of sodium sulfate undergoes a phenomenon of swelling when immersed in water, so the filling amount is kept low. In order to increase the filling amount and improve the water resistance, a method for improving the physical properties of the solidified body by adding an additive to the solidified material has been studied.

[0006]

The sodium sulfate is 3
Above 2.4 ° C., it is an anhydrous salt and stable, but below 32.4 ° C., it becomes a dehydrate. When the solidified solidified sodium sulfate is immersed in water at a temperature of 32.4 ° C. or less, 10%
When converted to water salt, the volume increases, and as a result, the solidified body expands. Therefore, by changing sodium sulfate to an alkaline earth metal salt that does not cause a swelling phenomenon, it is considered that a stable solidified body can be produced. However, when alkaline earth metal sulfate is generated, alkaline NaOH is simultaneously produced. As a result, a quick setting phenomenon occurs in ordinary Portland cement, and there is a problem that a good kneading operation cannot be performed.

[0007]

The present inventors have conducted intensive studies on a solidifying material for a radioactive waste liquid and a solidifying method which do not have the above-mentioned problems, and as a result, have found a solidifying material and a solidifying method capable of solving the above-mentioned problems. The present invention has been completed.

That is, the present invention provides (1) a solidifying material for sodium sulphate-containing radioactive waste liquid containing granulated blast furnace slag and alkaline earth metal hydroxide, (2) a hardening retarder, fine powder, and acicular inorganic powder. A solidifying material for a radioactive waste liquid according to the above (1), comprising one or more selected from dispersants;
(3) The solidifying material for a radioactive waste liquid according to the above (1) or (2), wherein the alkaline earth metal hydroxide is at least one selected from barium hydroxide and calcium hydroxide, (4)
A sodium sulfate-containing radioactive waste liquid and an alkaline earth metal hydroxide are mixed, and the mixture is concentrated by heating, and then the mixture is mixed with the alkaline earth metal hydroxide according to any one of the above (1) to (3). (5) a method for solidifying a sodium sulphate-containing radioactive waste liquid, which comprises kneading and curing a solidifying material component, and (5) a method for solidifying according to the above (4), wherein the temperature for heating and concentrating is 80 ° C. or higher.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The solidified material of the present invention can be obtained by mixing the following components at a predetermined ratio.

The granulated blast furnace slag used in the present invention has a Blaine specific surface area of 2,000 cm ² / g or more and 15,000 cm.
² / g or less is preferable, of which 3000 cm ²
/ G or more is particularly preferred.

The solidifying material of the present invention contains an alkaline earth metal hydroxide such as strontium hydroxide, barium hydroxide or calcium hydroxide. Of these, barium hydroxide or calcium hydroxide is preferably used.

The alkaline earth metal hydroxide is not limited to one kind, and two or more kinds can be used in combination. It is preferable to use a combination of calcium hydroxide and barium hydroxide. When calcium hydroxide and barium hydroxide are used in combination, the proportion used is such that barium hydroxide accounts for 70 to 95% in terms of moles.

The amount of the alkaline earth metal hydroxide used depends on the particle size of the granulated blast furnace slag to be used, the type and amount of various admixtures and fine powders to be added, and the amount of water.
The amount used is preferably 80% or more and equimolar or less of the number of moles of sodium sulfate contained in the waste. Further, the amount is preferably such that the solidification rate of sodium sulfate is 40% by weight or less. Here, the solidification rate of sodium sulfate refers to the weight of anhydrous sodium sulfate relative to the total amount of the solidified material and the radioactive waste liquid.

The solidified material of the present invention can contain a curing retarder, if necessary. Specific examples of curing retarders that can be used include sugar, glucose, sucrose, gypsum,
Examples thereof include zinc oxide, organic carboxylic acids and salts thereof, and sugar is particularly preferred.

The amount of the curing retarder used is 10 granulated blast furnace slag.
It is usually 0.05 to 5 parts by weight, preferably 0.1 to 3 parts by weight based on 0 parts by weight.

The solidified material of the present invention further contains a fine powder if necessary. As the fine powder, those having an average particle size smaller than the average particle size of the granulated blast furnace slag, preferably smaller than the average particle size of the granulated blast furnace slag by one order or more, more preferably smaller than the average particle size by 2 orders or more are used. .

The average particle size of the fine powder is preferably 10 μm or less, more preferably 0.01 to 5 μm, and most preferably 0.05 to 1 μm.

Specific examples of the fine powder that can be used include silica fume, fly ash, silica sand, silica powder, clay, talc, kaolin, calcium carbonate, ground ceramic, ground blast furnace slag ground, titania, zirconia, alumina,
Aerosil, etc., are used, and it is particularly preferable to use silica fume because the effect of improving the fluidity and the like and the mechanical strength of the solidified product after solidification is remarkable. The amount of fine powder used depends on the size (particle size) and type of granulated blast furnace slag and the type and amount of other various admixtures added as necessary.
Usually 2 to 50 parts by weight, preferably 5 to 5 parts by weight,
25 parts by weight.

The solidified material of the present invention also contains an acicular inorganic powder, if necessary. Specific examples of the acicular inorganic powder that can be used include wollastonite, sepiolite, asbestos, chrysotile, amosite, tremolite, and the like.From the viewpoint of improving the strength of the solidified product, improving durability, and the like,
Wollastonite is preferred.

The amount of the acicular inorganic powder used is usually 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the granulated blast furnace slag.

The solidifying material of the present invention optionally contains a dispersant. The dispersant is, for example, a polymer having a carboxylic acid group or a salt thereof in the molecule, such as poly (meth) acrylate, acrylic acid / maleic acid copolymer, acrylic acid / maleic acid / vinyl ether copolymer, acrylic acid・ Itaconic acid ・ styrene copolymer, acrylic acid ・ itaconic acid ・
Methacrylic acid / styrene copolymer, maleic anhydride / C
₅ -C ₈ a-olefin copolymer compound.

In the above, as the C ₅ -C ₈ olefin, 2-methylbutene-1, pentene-1, hexene-
1, cyclopentene, cyclohexene and the like.

When the dispersant has a salt of a carboxylic acid group, examples of the salt include alkali metal salts such as lithium salt, sodium salt and potassium salt, and ammonium salts and amine salts can also be used.

Specifically, sodium salt of acrylic acid / maleic acid copolymer, sodium salt of acrylic acid / itaconic acid / styrene copolymer, and sodium salt of acrylic acid / itaconic acid / methacrylic acid / styrene copolymer Sodium salt,
Sodium salt of acrylic acid / maleic anhydride / isobutyl vinyl ether copolymer, sodium salt of acrylic acid / maleic anhydride / styrene copolymer, sodium salt of maleic anhydride / 2-methylbutene-1 / pentene-1 copolymer And the like can also be used as a dispersant.

The dispersant used in the present invention is not limited to the copolymers listed here. That is, a formalin condensate of naphthalene sulfonic acid, a melamine sulfonic acid formalin condensate, a lignin sulfonic acid condensate, or the like, which is known as a water reducing agent for cement and concrete, can also be used in combination. These water reducing agents can be used alone or in combination of two or more.

The amount of the dispersant used depends on the required characteristics of the solidified product obtained by solidifying the solidified material of the present invention, the method of treating radioactive waste liquid, and the like, but the total amount of granulated blast furnace slag and fine powder (optional component) Usually 0.05 to 100 parts by weight
It is 10 parts by weight, preferably 0.1 to 6 parts by weight, particularly preferably 0.2 to 3 parts by weight.

Further, fibers and the like can be added for the purpose of further improving the water resistance of the obtained solidified product. Specific examples of fibers that can be used include glass fiber, carbon fiber, vinylon, nylon, aramid, polypropylene,
Fibers such as acrylic and polyester, cellulose fibers,
Examples include steel and alumina fibers. The amount of fiber used is usually 0.1 parts per 100 parts by weight of granulated blast furnace slag.
To 10 parts by weight.

The solidified material of the present invention obtained as described above is directly mixed with a sodium sulfate-containing radioactive waste liquid, kneaded, and cured to solidify, whereby the sodium sulfate-containing radioactive waste liquid can be solidified. It is preferably used as in the solidification treatment method of the present invention described in detail above.

Hereinafter, the processing method of the present invention will be described in detail.

In the treatment method of the present invention, an alkaline earth metal hydroxide is first mixed with a sodium sulfate-containing radioactive waste liquid. The alkaline earth metal hydroxide and sodium sulfate show the following reaction.

Na ₂ SO ₄ + M (OH) ₂ → MSO ₄ (precipitated) + 2NaOH (I) (M represents an alkaline earth metal; the same applies hereinafter) This reaction is based on the type of alkaline earth metal hydroxide and the reaction temperature. The reaction speed varies depending on To shorten the reaction time, barium hydroxide or a mixture of alkaline earth metal hydroxides containing barium hydroxide as a main component is used as the alkaline earth metal hydroxide. The treatment here is usually 60 ° C. or higher, preferably 70 ° C. or higher, more preferably 8 ° C. or higher.
The reaction is performed at 0 to 120 ° C., and the reaction mixture is concentrated by heating. It is preferable that the concentration is reduced to 50% by weight or less in terms of the concentration assuming that sodium sulfate is not reacted.
After the reaction of (I), the temperature of the reaction mixture is lowered to 40 ° C. or lower, and then a solidifying material other than the alkaline earth metal is charged and kneaded. Depending on the amount of alkaline earth metal hydroxide to be charged or the reaction time, sodium sulfate may remain.
At 4 ° C. or lower, dehydrate is formed, and in such a case, it is preferable to charge and knead the remaining solidified material at 32.4 ° C. or higher in such a case in order to ensure operability.

The granulated blast furnace slag is a latent hydraulic substance,
The hydration reaction does not proceed unless a curing stimulant such as an alkaline substance is added. However, in the solidified material of the present invention, sodium hydroxide is generated by the reaction (I), so that it is not necessary to add a separate curing stimulant. There is an advantage.

The radionuclide ¹⁴ contained in the radioactive waste liquid
C is mainly mixed in the waste liquid as carbonate ion ( ¹⁴ CO ₃ ^2- ), so that it reacts with alkaline earth metal ions to form an insoluble solid (M ²⁺ + CO ₃ ^2- → MCO ₃ (precipitation)), It is solidified stably to the solidified material, and prevents elution of nuclides.

After adding and kneading a solidifying material component other than the alkaline earth metal, a solidified product can be obtained usually at room temperature for 1 day to 2 weeks.

[0036]

The present invention will be described below in detail with reference to examples. Further, the present invention is not limited to these examples.

The flow values in the examples are measured for the composition after kneading according to JIS R5201.

Example 1 In a planetary mixer, 7771 g of a 25% by weight aqueous sodium sulfate solution as a simulated radioactive waste liquid and barium hydroxide 8 were added.
Add 2894 g of water salt and 100 g of calcium hydroxide, and add 9
The mixture was heated and kneaded at 0 ° C. or higher, and concentrated by evaporating water. After about 3 hours, the heating was stopped and the temperature was allowed to cool to 35 ° C. The weight at this time was 5459 g.

Next, a Blaine specific surface area of 10,000 cm ²
/ G blast furnace granulated slag (Nippon Steel Esment) 720
g, silica fume 80 g, wollastonite 80 g,
1 g of sugar was added and kneaded for another 2 minutes (equivalent to a solidification rate of sodium sulfate of 30% by weight). The flow value of the paste composition obtained by these kneadings was 315 mm.
Next, the kneaded material was placed in a cylindrical mold having a diameter of 5 cm and a height of 10 cm, and cured by heating at 60 ° C. for 1 day.

In order to examine the durability of the solidified product, a columnar specimen was immersed in a 10-fold volume of deionized water.
Changes in weight, changes in appearance, and presence or absence of collapse were observed. As a result, the appearance did not change even after March, and the weight loss was 6.5.
% And the increase in volume were as small as 0.23%, indicating that the water resistance was sufficient.

Example 2 In a planetary mixer, 2222 g of a 25% by weight aqueous sodium sulfate solution as a simulated radioactive waste liquid and barium hydroxide 8 were added.
1242 g of water salt was added, heated and kneaded at 90 ° C. or higher, and concentrated by evaporating water. After about 3 hours, the heating was stopped and the temperature was allowed to cool to 35 ° C. The weight at this time was 1776 g. Next, a Blaine specific surface area of 8000
Granulated blast furnace slag of cm ² / g (Nippon Steel Esment) 1
000 g and 1 g of sugar were added and kneaded for another 2 minutes (corresponding to a solidification rate of sodium sulfate of 20% by weight). The flow value of the paste composition obtained by these kneading is 280 mm
Met. Next, the kneaded material was placed in a cylindrical mold having a diameter of 5 cm and a height of 10 cm, and cured by heating at 60 ° C. for 1 day.

In order to examine the durability of the solidified product, a columnar specimen was immersed in 10 times the volume of deionized water.
Changes in weight, changes in appearance, and presence or absence of collapse were observed. As a result, the appearance did not change even after March, and the weight loss was 5.5.
%, And the volume increase was as small as 0.20%, indicating that the water resistance was sufficient.

Example 3 690 g of a 25% by weight aqueous sodium sulfate solution and 385 g of barium hydroxide octahydrate, which are simulated radioactive waste liquid, were placed in a planetary mixer, heated and kneaded at 90 ° C. or higher, and concentrated by evaporating water. . After about 3 hours, the heating was stopped and the temperature was allowed to cool to 35 ° C. The weight at this time is 72
2 g. Next, Blaine specific surface area 10000 cm
² / g granulated blast furnace slag (Nippon Steel Esment) 900
g, wollastonite 100g, sugar 1g and 2 more
Kneading (equivalent to a solidification rate of sodium sulfate of 10%). The flow value of the paste composition obtained by these kneadings was 330 mm. Next, the kneaded material was placed in a cylindrical mold having a diameter of 5 cm and a height of 10 cm, and cured by heating at 60 ° C. for 1 day.

In order to examine the durability of the solidified product, a columnar specimen was immersed in 10 times the volume of deionized water.
Changes in weight, changes in appearance, and presence or absence of collapse were observed. As a result, the appearance did not change even after March, and the weight loss was 3.0.
%, And the volume increase was as small as 0.10%, indicating that the water resistance was sufficient.

[0045]

The solidifying material and the solidifying method of the present invention utilize the chemical change of the above (I) to change the sodium sulfate which causes the solidified material to break down, thereby obtaining a stable solidified material having excellent water resistance. Things. In addition, the dissolution of the radionuclide is suppressed by the fact that the solidified material is not destroyed itself, but a further elution prevention effect can be expected by the alkaline earth metal hydroxide contained in the solidified material.

Further, since sodium hydroxide, which is a hardening stimulant necessary for hardening the granulated blast furnace slag, is produced as a by-product of this reaction, no separate equipment for mixing a hardening stimulant is required, and an economic effect can be expected.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kazunori Suzuki 2205 Narita-cho, Oarai-machi, Higashiibaraki-gun, Ibaraki Pref. Inside the Oarai Nuclear Technology Development Center (72) Inventor Shigeru Mihara Narita-cho, Oarai-cho, Higashiibaraki-gun, Ibaraki 2205 JGC Corporation Oarai Nuclear Technology Development Center (72) Inventor Tadashi Sasaki 2205 JGC Corporation Oarai Nuclear Technology Development Center in Oarai-machi, Higashiibaraki-gun

Claims (5)

[Claims] 1. A solidifying material for radioactive waste liquid containing sodium sulfate, comprising granulated blast furnace slag and alkaline earth metal hydroxide. 2. The solidifying material for radioactive waste liquid according to claim 1, further comprising at least one selected from a curing retarder, a fine powder, an acicular inorganic powder, and a dispersant. 3. The solidifying material for radioactive waste liquid according to claim 1, wherein the alkaline earth metal hydroxide is at least one selected from barium hydroxide and calcium hydroxide. 4. A sodium sulfate-containing radioactive waste liquid and an alkaline earth metal hydroxide are mixed, and the mixture is concentrated by heating, and then the alkaline earth metal hydroxide according to any one of claims 1 to 3. A method for solidifying a sodium sulfate-containing radioactive waste liquid, which comprises kneading a solidifying material component other than a substance and curing and solidifying. 5. The method according to claim 4, wherein the temperature for heat concentration is 80 ° C. or higher.