JP2013160659A - Method for removing radioactive cesium and hydrophilic resin composition for removing radioactive cesium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple and inexpensive novel method for removing radioactive cesium, solving problems of conventional techniques and dispensing with an energy source such as electric power.SOLUTION: In a method for removing radioactive cesium the radioactive cesium in radioactive waste and/or in radioactive solids is removed using a hydrophilic resin composition containing a hydrophilic resin and a zeolite. The hydrophilic resin composition includes at least one type of hydrophilic resins selected from a group having a hydrophilic segment and consisting of hydrophilic polyurethane resin, hydrophilic polyurea resin, hydrophilic polyurethane-polyurea resin, and is formed by dispersing at least 1 to 200 pts.mass of zeolite relative to 100 pts.mass of the hydrophilic resin. The hydrophilic resin composition for removing the radioactive cesium is also provided.

Description

  The present invention relates to a method for removing radioactive cesium present in radioactive liquid waste and / or radioactive solids generated from nuclear power plants and spent nuclear fuel facilities, and a hydrophilic resin having a function of immobilizing radioactive cesium suitable for the method. Relates to the composition.

  Currently, widely used nuclear power plants involve the production of significant amounts of radioactive byproducts from nuclear fission in nuclear reactors. The main ones of these radioactive atoms are fission products and active elements containing extremely dangerous radioactive isotopes such as radioactive iodine, radioactive cesium, radioactive strontium and radioactive cerium. Among these, radioactive cesium is one of metals that have a melting point of 28.4 ° C. and is in a liquid state at room temperature, and is very easily released to the outside. Cesium 134 having a relatively short half-life (half-life) : 2 years) and a long half-life of cesium 137 (half-life: 30 years). In particular, cesium 137 not only has a long half-life, but also emits high-energy radiation, and is an alkali metal, and thus has a property of being highly soluble in water. Furthermore, since radioactive cesium is easily absorbed by the human body through respiration and skin, and is dispersed almost uniformly throughout the body, the health damage to humans when released is serious.

  For this reason, when radioactive cesium is accidentally released from reactors operating around the world due to unforeseen reasons, it is not only radioactively contaminated by workers working in the reactor and neighboring residents, but also by air. There is concern that a wider range of radioactive contamination will be caused to humans and animals through food and water contaminated with radioactive cesium. The danger in this regard has been clearly demonstrated by the Chernobyl nuclear power plant accident.

  On the other hand, as a method of removing radioactive cesium produced by nuclear fission in a nuclear reactor, an adsorption method using an inorganic ion exchanger or a selective ion exchange resin, or a coprecipitation using a heavy metal and a soluble ferrocyanide or ferrocyanide salt in combination. And a chemical treatment method using a cesium precipitation reagent are known (for example, see Patent Document 1).

  However, all of the above-described processing methods require large facilities such as a circulation pump, a septic tank, and a filling tank containing each adsorbent, and a large amount of energy for operating them. Furthermore, as the Fukushima Daiichi nuclear power plant accident that occurred on March 11, 2011, when the power supply is cut off, these facilities cannot be operated. The risk of contamination increases. And there is a concern that the removal method for radioactive cesium diffused to the surrounding area due to the runaway accident of the nuclear reactor will fall into a very difficult situation, and the situation that may expand radioactive contamination. Therefore, it is desired to develop the radioactive cesium removal technology that can cope with such a situation where the power supply is cut off, and it is extremely useful if it is developed.

JP-A-4-118596

  Therefore, the object of the present invention is to solve the problems of the prior art, is simple and low cost, does not require an energy source such as electric power, and is stable by incorporating the removed radioactive cesium into the solid. It is an object of the present invention to provide a novel radioactive cesium removal technique that can be immobilized on a radioactive waste and can reduce the volume of radioactive waste as required. Another object of the present invention is to provide a novel hydrophilic resin composition that has a function of immobilizing radioactive cesium, which is particularly useful for the above-described technique, and that can be easily removed. It is in.

  The above object is achieved by the present invention described below. That is, the present invention is a radioactive cesium removal method for removing radioactive cesium in a radioactive liquid waste and / or radioactive solid using a hydrophilic resin composition comprising a hydrophilic resin and zeolite, The hydrophilic resin composition includes at least one hydrophilic resin selected from the group consisting of a hydrophilic polyurethane resin, a hydrophilic polyurea resin, a hydrophilic polyurethane-polyurea resin having a hydrophilic segment, and the hydrophilic resin composition. Provided is a method for removing radioactive cesium, characterized in that at least zeolite is dispersed at a ratio of 1 to 200 parts by mass with respect to 100 parts by mass of the conductive resin.

［但し、式（１）中、Ｍ²⁺は、Ｃａ²⁺、Ｍｎ²⁺、Ｂａ²⁺又はＭｇ²⁺のいずれかであり、Ｍ⁺は、Ｎａ⁺、Ｋ⁺又はＬｉ⁺のいずれかであり、ｍは１〜１８のいずれかの数、ｎは１〜７０のいずれかの数である。］ The following are mentioned as a preferable form of this invention. The hydrophilic segment is a polyethylene oxide segment; the zeolite is a compound represented by the following general formula (1).

[In the formula (1), M ²⁺ is, Ca ^2+, Mn ^2+, is either Ba ²⁺ or Mg ^2+, M ⁺ is, Na ^+, K ⁺ or Li ⁺ either M is any number from 1 to 18, and n is any number from 1 to 70. ]

  In the present invention, as another embodiment, a hydrophilic resin composition having a function capable of fixing radioactive cesium in a liquid and / or a solid material, which includes a hydrophilic resin and a zeolite, and the hydrophilic resin , A resin having a hydrophilic segment, insoluble in water and warm water, and at least zeolite is dispersed at a ratio of 1 to 200 parts by mass with respect to 100 parts by mass of the hydrophilic resin. A hydrophilic resin composition for removing radioactive cesium is provided.

  Furthermore, in the present invention, as another embodiment, a hydrophilic resin composition having a function capable of fixing radioactive cesium in a liquid and / or a solid material, which includes a hydrophilic resin and a zeolite, the hydrophilic resin Is a hydrophilic polyurethane resin, hydrophilic polyurea resin, hydrophilic polyurethane having a hydrophilic segment obtained by reacting an organic polyisocyanate with a hydrophilic polyol and / or polyamine having a high molecular weight as a hydrophilic component. A radioactive cesium characterized in that it is at least one selected from the group consisting of polyurea resins, and at least zeolite is dispersed at a ratio of 1 to 200 parts by mass with respect to 100 parts by mass of the hydrophilic resin. A hydrophilic resin composition for removal is provided.

［但し、式（１）中、Ｍ²⁺は、Ｃａ²⁺、Ｍｎ²⁺、Ｂａ²⁺又はＭｇ²⁺のいずれかであり、Ｍ⁺は、Ｎａ⁺、Ｋ⁺又はＬｉ⁺のいずれかであり、ｍは１〜１８のいずれかの数、ｎは１〜７０のいずれかの数である。］ The following is mentioned as a preferable form of one of the above-described hydrophilic resin compositions of the present invention. It is mentioned that the hydrophilic segment of the hydrophilic resin is a polyethylene oxide segment; the zeolite is any one of compounds represented by the following general formula (1).

[In the formula (1), M ²⁺ is, Ca ^2+, Mn ^2+, is either Ba ²⁺ or Mg ^2+, M ⁺ is, Na ^+, K ⁺ or Li ⁺ either M is any number from 1 to 18, and n is any number from 1 to 70. ]

  According to the present invention, radioactive cesium present in a liquid or a solid can be treated easily and at low cost, and further, an energy source such as electric power is not required, and the removed radioactive cesium can be removed. Provided is a novel radioactive cesium removal technique that can be stably fixed by working inside a solid, and can reduce the volume of radioactive waste as required. According to the present invention, it has a function capable of immobilizing radioactive cesium, and it can be realized to remove it, and since its main component is a resin composition, the radioactive waste can be reduced as necessary. Provided is a novel hydrophilic resin composition that can be tolerated. The remarkable effect of the present invention is achieved by an extremely simple method of using a hydrophilic resin composition in which zeolite is dispersed in a hydrophilic resin having a hydrophilic segment in its structure. The above-mentioned hydrophilic resin is obtained, for example, by reacting an organic polyisocyanate with a high molecular weight hydrophilic polyol and / or polyamine (hereinafter referred to as “hydrophilic component”), and more specifically, hydrophilic polyurethane. Examples thereof include at least one selected from the group consisting of a resin, a hydrophilic polyurea resin, and a hydrophilic polyurethane-polyurea resin.

The figure which shows the relationship between the cesium density | concentration in aqueous solution, and the immersion time of the film which consists of the hydrophilic resin composition of Examples 1-3. The figure which shows the relationship between the cesium density | concentration in aqueous solution, and the immersion time of the film which consists of the non-hydrophilic resin composition of Comparative Examples 1-2.

Next, the present invention will be described in more detail with reference to preferred embodiments.
The hydrophilic resin composition used in the present invention comprises a composition in which a zeolite is dispersed in a hydrophilic resin, and the hydrophilic resin has a hydrophilic segment having a hydrophilic component as a structural unit. Features. That is, the hydrophilic resin used in the present invention only needs to have a hydrophilic segment having a hydrophilic component as a structural unit in its structure. Specific examples include a hydrophilic polyurethane resin having a hydrophilic segment, a hydrophilic polyurea resin, and a hydrophilic resin selected from the group consisting of a hydrophilic polyurethane-polyurea resin. The hydrophilic segments in these resins are bonded at random by urethane bonds, urea bonds, urethane-urea bonds or the like when a chain extender is not used during the synthesis of the hydrophilic resin. In addition, when chain extension is used during the synthesis of the hydrophilic resin, a structure in which a short chain that is a residue of the chain extender exists between these bonds is provided.

  “Hydrophilic resin” in the present invention means a resin having a hydrophilic group in its molecule but insoluble in water, hot water, etc., and includes polyvinyl alcohol, polyvinyl pyrrolidone, and polyacrylic. It is distinguished from water-soluble resins such as acids and cellulose derivatives. Details thereof will be described later.

  The hydrophilic resin composition of the present invention comprises the above-described specific hydrophilic resin and zeolite, and the present inventors have explained why the radioactive cesium can be removed by using the composition. I think as follows. First, since the hydrophilic resin used in the present invention exhibits excellent water absorption due to the hydrophilic segment present in the structure, it is considered that ionized radioactive cesium to be treated is quickly taken into the resin. .

  And in the present invention, since the hydrophilic resin composition of the present invention in which zeolite is dispersed and contained in the hydrophilic resin having such a function is used, the dispersed zeolite is more quickly and It is considered that radioactive cesium is efficiently fixed and fixed.

  The zeolite used in the present invention can be synthesized artificially, but is a naturally occurring crystalline compound having fine pores at the molecular level, consisting of silicon, aluminum, and oxygen, and various crystals. Those having a structure are known. Zeolite has a unique crystal structure with pores with a very large surface area, so it exhibits a high adsorption capacity for gases and ions, a catalytic ability to assist various chemical reactions, and the size of the pores. It is also used in a wide range of fields because it is possible to screen molecules by.

［但し、式（１）中、Ｍ²⁺は、Ｃａ²⁺、Ｍｎ²⁺、Ｂａ²⁺又はＭｇ²⁺のいずれかであり、Ｍ⁺は、Ｎａ⁺、Ｋ⁺又はＬｉ⁺のいずれかであり、ｍは１〜１８のいずれかの数、ｎは１〜７０のいずれかの数である。］ Natural zeolite is a mineral having a void (pore) as described above in the crystal structure among aluminosilicates represented by the following general formula (1), any of which can be used in the present invention.

[In the formula (1), M ²⁺ is, Ca ^2+, Mn ^2+, is either Ba ²⁺ or Mg ^2+, M ⁺ is, Na ^+, K ⁺ or Li ⁺ either M is any number from 1 to 18, and n is any number from 1 to 70. ]

Zeolite is widely used as a catalyst and adsorbing material as described above, but in addition to these, the positive ions contained in the zeolite can be easily exchanged for other ions, thus exhibiting high ion exchange properties. Since it can be used even under conditions such as high temperatures unsuitable for resins, it is also useful as an ion exchange material. In the present invention, in addition to the above-described high adsorption function of zeolite, in particular, by utilizing the ion exchange property of zeolite, radioactive cesium present in the liquid and / or solid matter is removed. Here, the ion exchange property of zeolite will be specifically described. The ion exchange property of zeolite is expressed due to the crystal structure forming the framework of the zeolite, as described below. Since silicon (Si), which is one of the components that form the framework (crystal lattice) of zeolite, is tetravalent, oxygen, which is a divalent negative ion, can be balanced in charge with a composition of SiO _2. Since aluminum (Al), which is one component, is trivalent, when Al enters the skeleton instead of Si, one positive charge is deficient and a cation deficiency is generated. Therefore, the zeolite contains another cation, and the cation such as sodium (Na), calcium (Ca), potassium (K), etc. is taken into the generated defect portion to balance the charge. Yes. Since the cation contained in the taken-in zeolite has the property of being interchanged with other cations in the aqueous solution, the zeolite exhibits high ion exchange properties. Here, the priority order of cation exchange possessed by zeolite is as follows.

<Ion exchange order>
Cesium (Cs)> Rubidium (Rb)> NH ₄ > Barium (Ba)> Strontium (Sr)>Na>Ca> Iron (Fe)>Al> Magnesium (Mg)> Lithium (Li)

  As described above, since the ion exchange order of cesium and strontium is high, it is said that the ion exchange property of zeolite can be used for the removal of radioactive substances such as radioactive cesium, and this point is publicly known. In the present invention, by using a hydrophilic resin composition containing the above-mentioned zeolite dispersed in a hydrophilic resin, a technique capable of removing radioactive cesium more efficiently, simply and economically is provided.

  The hydrophilic resin composition characterizing the present invention comprises a hydrophilic resin, which is characterized in that it has a hydrophilic segment having a hydrophilic component as a structural unit, as described above. Furthermore, it is insoluble in water and warm water. Specific examples include at least one selected from the group consisting of a hydrophilic polyurethane resin, a hydrophilic polyurea resin, and a hydrophilic polyurethane-polyurea resin having a hydrophilic segment.

  These hydrophilic resins having a hydrophilic segment are obtained by reacting an organic polyisocyanate with a compound having a high molecular weight hydrophilic polyol and / or polyamine which is a hydrophilic component. Hereinafter, the compound used for the synthesis of the hydrophilic resin characterizing the present invention will be described.

  Examples of the hydrophilic component used for the synthesis of the hydrophilic resin used in the present invention include, for example, a terminal group having a hydrophilic group such as a hydroxyl group, an amino group, or a carboxyl group, and a weight average molecular weight (converted to standard polystyrene measured by GPC). A high molecular weight hydrophilic polyol and / or polyamine having a value of 400 to 8,000 is preferred. More specifically, for example, as a polyol having a hydroxyl group at the end and having hydrophilicity, for example, polyethylene glycol, polyethylene glycol / polytetramethylene glycol copolymer polyol, polyethylene glycol / polypropylene glycol copolymer polyol, polyethylene glycol adipate polyol Polyethylene glycol succinate polyol, polyethylene glycol / polyε-lactone copolymer polyol, polyethylene glycol / polyvalerolactone copolymer polyol, and the like.

  Moreover, the terminal is an amino group and is a polyamine which has hydrophilicity, for example, a polyethylene oxide diamine, a polyethylene oxide propylene oxide diamine, a polyethylene oxide triamine, a polyethylene oxide propylene oxide triamine, etc. are mentioned. Examples of other hydrophilic components include an ethylene oxide adduct having a carboxyl group or a vinyl group.

  In the present invention, in order to impart water resistance to the hydrophilic resin to be used, it is also possible to use other polyols, polyamines, polycarboxylic acids and the like having no hydrophilic chain together with the above hydrophilic component.

  As the organic polyisocyanate used for the synthesis of the hydrophilic resin used in the present invention, any known ones in the synthesis of conventional polyurethane resins can be used and are not particularly limited. Preferable examples include 4,4′-diphenylmethane diisocyanate (hereinafter abbreviated as MDI), hydrogenated MDI, isophorone diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 2,4-trilylene. It is also possible to use a range of isocyanates, m-phenylene diisocyanates, p-phenylene diisocyanates, etc., or polyurethane prepolymers obtained by reacting these organic polyisocyanates with low molecular weight polyols or polyamines to form terminal isocyanates.

  In addition, as the chain extender used as necessary when synthesizing the hydrophilic resin used in the present invention, for example, any conventionally known chain extender such as a low molecular diol or diamine can be used. It is not limited. Specific examples include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, ethylenediamine, hexamethylenediamine, and the like.

  The hydrophilic resin obtained by reacting the raw material components as described above and having a hydrophilic segment used in the present invention in the molecular chain has a weight average molecular weight (standard polystyrene conversion value measured by GPC, hereinafter the same). , Preferably in the range of 3,000 to 800,000. A more preferred weight average molecular weight is in the range of 5,000 to 500,000.

  Further, the content of the hydrophilic segment in the hydrophilic resin particularly suitable for the method for removing radioactive cesium of the present invention is preferably in the range of 20 to 80% by mass, more preferably in the range of 30 to 70% by mass. When a resin having a hydrophilic segment content of less than 20% by mass is used, the water absorption performance is inferior, and the removability of radioactive cesium tends to decrease. On the other hand, when a resin exceeding 80% by mass is used, the water resistance becomes inferior.

  The hydrophilic resin composition of the present invention suitable for the method for removing radioactive cesium of the present invention can be obtained by dispersing zeolite in the above-described hydrophilic resin. Specifically, it can be produced by adding a zeolite and a dispersion solvent to the hydrophilic resin as described above and performing a dispersion operation with a predetermined disperser. As the disperser used for the dispersion, any disperser that is usually used for pigment dispersion can be used without any problem. For example, paint conditioner (manufactured by Red Devil), ball mill, pearl mill (manufactured by Eirich), sand mill, visco mill, attritor mill, basket mill, wet jet mill (manufactured by Genus), etc., but dispersibility It is preferable to set in view of the economy. Further, as the media, glass beads, zirconia beads, alumina beads, magnetic beads, stainless beads, etc. can be used.

  As the dispersion ratio of the hydrophilic resin and the zeolite in the hydrophilic resin composition of the present invention, a mixture of zeolite in a ratio of 1 to 200 parts by mass with respect to 100 parts by mass of the hydrophilic resin is used. If the amount of zeolite is less than 1 part by mass, removal of radioactive cesium may be insufficient. If the amount exceeds 200 parts by mass, the mechanical properties of the composition become weak and the water resistance becomes inferior. This is not preferable because there is a risk that it will not be possible to maintain the value.

  In carrying out the method for removing radioactive cesium of the present invention, it is preferable to use the hydrophilic resin composition of the present invention having the above-described configuration in the following form. That is, the hydrophilic resin composition solution is obtained by applying the solution on a release paper, a release film or the like so that the thickness after drying is 5 to 100 μm, preferably 10 to 50 μm, and drying in a drying furnace. What was made into the film form is mentioned. In this case, it is peeled off from the release paper / film during use and used as a radioactive cesium removal film. In addition, various base materials may be used by applying or impregnating the composition solution obtained from the raw materials described above. As the base material, metal, glass, wood, fiber, various plastics, etc. are used. it can.

  Soaking the film made of the hydrophilic resin composition of the present invention or a sheet coated on various substrates obtained as described above in a radioactive waste liquid or a waste liquid in which radioactive solids have been decontaminated in advance with water. Thus, radioactive cesium present in these liquids can be removed. Moreover, the solid substance etc. which were contaminated with the radioactivity can prevent diffusion of radioactive cesium by covering the solid substance with the film or sheet of the present invention.

  Since the film or sheet of the hydrophilic resin composition of the present invention does not dissolve in water, it can be easily taken out from the waste liquid after decontamination. In this way, no special equipment or electric power is required to remove radioactive cesium, and decontamination can be performed easily and at low cost. Furthermore, if the absorbed water is dried and heated to 100 to 170 ° C., the resin is softened, the volume shrinks, and the effect of reducing the volume of radioactive waste can be expected.

  Next, the present invention will be described in more detail with reference to specific production examples, examples and comparative examples, but the present invention is not limited to these examples. Further, “parts” and “%” in the following examples are based on mass unless otherwise specified.

[Production Example 1] (Synthesis of hydrophilic polyurethane resin)
A reaction vessel equipped with a stirrer, a thermometer, a gas introduction tube and a reflux condenser was replaced with nitrogen, 150 parts of polyethylene glycol (molecular weight 2,040), 20 parts of 1,4 butanediol, 150 parts of methyl ethyl ketone (hereinafter, It was dissolved in a mixed solvent of 200 parts of dimethylformamide (hereinafter abbreviated as DMF) and stirred well at 60 ° C. And the solution which melt | dissolved 77 parts hydrogenation MDI in 50 parts MEK was dripped gradually, stirring. After the completion of dropping, the mixture was reacted at 80 ° C. for 7 hours, and then 60 parts of MEK was added to obtain a hydrophilic resin solution defined in the present invention.
This resin solution had a solid content of 35% and a viscosity of 280 dPa · s (25 ° C.). The hydrophilic resin film formed from this solution had a breaking strength of 32.5 MPa, a breaking elongation of 450%, a thermal softening temperature of 115 ° C., and a weight average molecular weight of 78,000.

[Production Example 2] (Synthesis of hydrophilic polyurea resin)
In a reaction vessel similar to that used in Production Example 1, 150 parts of polyethylene oxide diamine (“Jeffamine ED” (trade name) manufactured by Huntsman; molecular weight 2,000) and 18 parts of 1,4-diaminobutane were added to DMF250. The inner temperature was well stirred at 20-30 ° C. While stirring, a solution prepared by dissolving 73 parts of hydrogenated MDI in 100 parts of DMF was gradually added dropwise to cause reaction. After completion of the dropwise addition, the internal temperature was gradually raised, and when the temperature reached 50 ° C., the reaction was further continued for 6 hours, and then 97 parts of DMF was added to obtain a hydrophilic resin solution defined in the present invention.
This resin solution had a solid content of 35% and a viscosity of 210 dPa · s (25 ° C.). The hydrophilic resin film formed from this resin solution had a breaking strength of 18.3 MPa, a breaking elongation of 310%, a thermal softening temperature of 145 ° C., and a weight average molecular weight of 67,000.

[Production Example 3] (Synthesis of hydrophilic polyurethane-polyurea resin)
150 parts of polyethylene oxide diamine (manufactured by Huntsman “Jeffamine ED” (trade name); molecular weight 2,000) and 15 parts of ethylene glycol were dissolved in 250 parts of DMF in the same reaction vessel used in Production Example 1. The internal temperature was well stirred at 20-30 ° C. And the solution which melt | dissolved 83 parts hydrogenation MDI in 100 parts MEK was dripped gradually, stirring. After completion of the dropwise addition, the mixture was reacted at 80 ° C. for 6 hours, and then 110 parts of MEK was added to obtain a hydrophilic resin solution defined in the present invention.
This resin solution had a solid content of 35% and a viscosity of 250 dPa · s (25 ° C.). The hydrophilic resin film formed from this resin solution had a breaking strength of 14.7 MPa, a breaking elongation of 450%, a thermal softening temperature of 121 ° C., and a weight average molecular weight of 71,000.

[Production Example 4] (Synthesis of non-hydrophilic polyurethane resin used in Comparative Example)
A reaction vessel similar to that used in Production Example 1 was purged with nitrogen, 150 parts of polybutylene adipate having an average molecular weight of about 2,000 and 15 parts of 1,4-butanediol were dissolved in 250 parts of DMF. Stir well at ° C. Then, with stirring, 62 parts of hydrogenated MDI dissolved in 100 parts of MEK were gradually added dropwise. After completion of the dropwise addition, the mixture was reacted at 80 ° C. for 6 hours, and then 71 parts of MEK was added to obtain a non-hydrophilic resin solution used in this comparative example.
This resin solution had a viscosity of 320 dPa · s (25 ° C.) at a solid content of 35%. The non-hydrophilic resin film obtained from this solution had a breaking strength of 45 MPa, a breaking elongation of 480%, a thermal softening temperature of 110 ° C., and a weight average molecular weight of 82,000.

[Production Example 5] (Synthesis of non-hydrophilic polyurethane-polyurea resin used in Comparative Example)
In a reaction vessel similar to that used in Production Example 1, 150 parts of polybutylene adipate having an average molecular weight of about 2,000 and 18 parts of hexamethylenediamine are dissolved in 200 parts of DMF, and the internal temperature is well stirred at 20-30 ° C. did. And the solution which melt | dissolved 60 parts hydrogenation MDI in 100 parts MEK was dripped gradually, stirring. After completion of the dropwise addition, the mixture was reacted at 80 ° C. for 6 hours, and then 123 parts of MEK was added to obtain a non-hydrophilic resin solution used in this comparative example.
This resin solution had a solid content of 35% and a viscosity of 250 dPa · s (25 ° C.). The non-hydrophilic resin film formed from this resin solution had a breaking strength of 14.7 MPa, a breaking elongation of 450%, a thermal softening temperature of 121 ° C., and a weight average molecular weight of 68,000.

<Examples 1-3, Comparative Examples 1-2>
Each resin solution of Production Examples 1 to 5 and zeolite (manufactured by Sun Zeolite Industry Co., Ltd.) are blended in high density alumina balls (3.5 g / ml) with each formulation shown in Table 1 (displayed on a mass basis). ) For 24 hours by ball mill dispersion. The dispersed contents were taken out through a 100-mesh sieve made of polyester resin to obtain liquid resin compositions containing a resin solution and zeolite.

[Evaluation]
(Production of resin film)
Using the liquid resin compositions of Examples 1 to 3 and Comparative Examples 1 and 2, the resin films were prepared as follows. Specifically, after each of the above resin compositions was applied onto a release paper, the solvent was evaporated by heating and drying at 110 ° C. for 3 minutes to prepare each resin film having a thickness of about 20 μm. Next, each resin film thus obtained was used to evaluate the effect on the removal of cesium ions by the following method.

(Preparation of cesium solution for evaluation test)
The cesium solution for the evaluation test was prepared by dissolving cesium chloride in ion-exchanged pure water so that the cesium ion concentration was 100 mg / L (100 ppm). If cesium ions can be removed, naturally radioactive cesium can be removed.

<The evaluation result about the resin composition of Example 1>
20 g of a resin film prepared using the hydrophilic resin composition of Example 1 was immersed in 100 ml of a cesium solution having an ion concentration of 100 ppm prepared for the evaluation test previously (25 ° C.), and in the solution every elapsed time. Was measured with an ion chromatograph (manufactured by Tosoh; IC2001). In Table 2, the removal rate of cesium ions in the solution for each elapsed time is also described. Further, the results of the change over time obtained are shown in FIG.

<Evaluation results for resin compositions of Examples 2 and 3>
The cesium ion concentration in the solution was measured for each elapsed time in the same manner as in Example 1 except that 20 g of the resin film prepared with each hydrophilic resin composition of Example 2 or Example 3 was used. The obtained results are shown in Table 2 and FIG. 1 in the same manner as in Example 1 described above.

<Evaluation results for the resin compositions of Comparative Examples 1 and 2>
The cesium ion concentration in the solution was measured for each elapsed time in the same manner as in Example 1 except that 20 g of the resin film prepared with each non-hydrophilic resin composition of Comparative Examples 1 and 2 was used. The obtained results are shown in Table 3 and FIG. 2 in the same manner as in Example 1 described above.

  As an application example of the present invention, radioactive cesium in liquids and / or solids can be processed easily and at low cost, and furthermore, it can be removed without requiring an energy source such as electric power. By implementing this removal method, it has become possible to easily and economically remove radioactive substances present in liquids and solids that have recently become problematic, and its practical value is Extremely expensive. Furthermore, in the technique of the present invention, the hydrophilic resin having a hydrophilic segment, and the hydrophilic resin composition comprising zeolite, can quickly take in the removed radioactive cesium and stably fix it, Furthermore, since the main component is a resin composition, it is also possible to reduce the volume of radioactive waste as necessary. It can be reduced and its use is expected.

Claims (7)

A method for removing radioactive cesium, wherein radioactive cesium in a radioactive liquid waste and / or radioactive solid is removed using a hydrophilic resin composition comprising a hydrophilic resin and zeolite,
The hydrophilic resin composition includes a hydrophilic segment, and includes at least one hydrophilic resin selected from the group consisting of a hydrophilic polyurethane resin, a hydrophilic polyurea resin, and a hydrophilic polyurethane-polyurea resin, and
A method for removing radioactive cesium, wherein at least zeolite is dispersed at a ratio of 1 to 200 parts by mass with respect to 100 parts by mass of the hydrophilic resin.   The method for removing radioactive cesium according to claim 1, wherein the hydrophilic segment is a polyethylene oxide segment. The method for removing radioactive cesium according to claim 1 or 2, wherein the zeolite is a compound represented by the following general formula (1).

[In the formula (1), M ²⁺ is, Ca ^2+, Mn ^2+, is either Ba ²⁺ or Mg ^2+, M ⁺ is, Na ^+, K ⁺ or Li ⁺ either M is any number from 1 to 18, and n is any number from 1 to 70. ] A hydrophilic resin composition having a function of fixing radioactive cesium in a liquid and / or a solid,
Including a hydrophilic resin and zeolite,
The hydrophilic resin has a hydrophilic segment and is insoluble in water and warm water, and at least 1 to 200 parts by mass of zeolite with respect to 100 parts by mass of the hydrophilic resin. A hydrophilic resin composition for removing radioactive cesium, which is dispersed in a proportion. A hydrophilic resin composition having a function of fixing radioactive cesium in a liquid and / or a solid,
Including a hydrophilic resin and zeolite,
The hydrophilic resin is obtained by reacting an organic polyisocyanate with a high molecular weight hydrophilic polyol and / or polyamine which is a hydrophilic component, and has a hydrophilic segment, a hydrophilic polyurethane resin, a hydrophilic polyurea resin, At least one selected from the group consisting of a hydrophilic polyurethane-polyurea resin, and
A hydrophilic resin composition for removing radioactive cesium, wherein at least zeolite is dispersed at a ratio of 1 to 200 parts by mass with respect to 100 parts by mass of the hydrophilic resin.   The hydrophilic resin composition for removing radioactive cesium according to claim 4 or 5, wherein the hydrophilic segment of the hydrophilic resin is a polyethylene oxide segment. The hydrophilic resin composition for removing radioactive cesium according to any one of claims 4 to 6, wherein the zeolite is a compound represented by the following general formula (1).

[In the formula (1), M ²⁺ is, Ca ^2+, Mn ^2+, is either Ba ²⁺ or Mg ^2+, M ⁺ is, Na ^+, K ⁺ or Li ⁺ either M is any number from 1 to 18, and n is any number from 1 to 70. ]

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