JP2939529B2 - Boron isotope separating agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel boron isotope separating agent, and more particularly, to a method for efficiently and economically producing a boron isotope having a mass number of 10 and a boron isotope having a mass number of 11 from a mixture of boron isotopes. TECHNICAL FIELD The present invention relates to a boron isotope separating agent having an excellent resolving power that can be separated.

[0002]

2. Description of the Related Art In recent years, boron has a high neutron absorption cross section (a 759 burn in a natural isotope mixture). Have been.
Naturally, as boron isotopes, mass numbers 10 and 11
Are present in a ratio of 1: 4 ( ¹⁰ B and ¹¹ B). Among these isotopes, the boron isotope having a mass number of 10 is particularly large in neutron absorption cross section (3
813 burn), it is extremely useful as a compact shielding material for thermal neutrons, a control material for fast neutron reactors, and a neutron capture material in radiotherapy. On the other hand, a boron isotope having a mass number of 11 is attracting attention as an alloy additive for a core structure material of a nuclear reactor, a raw material of a thermofluorescence dose element, etc., utilizing the fact that neutron absorption does not occur. Under such circumstances, there is a strong demand for establishing a technique for efficiently separating boron isotopes having a mass number of 10 and 11 from a mixture of boron isotopes.

Conventionally, as a method for separating boron isotopes, for example, a distillation method and an adsorption method are known. Among them, it is said that the most suitable distillation method is, for example, a method of equilibrium distillation of a complex compound of boron trifluoride and dimethyl ether [BF _3. (CH ₃ ) ₂ O]. This method utilizes an isotope exchange equilibrium established between the complex and BF ₃ generated by partial decomposition, and has a high overall separation coefficient of 1.016, but consumes a large amount of energy for heating. Since a highly corrosive and water-free system is required, the apparatus has the disadvantage that the apparatus is complicated and the separation cost is high.

On the other hand, the adsorption method is a method for separating isotopes utilizing an adsorption reaction from an aqueous solution to a solid phase by an ion exchange reaction. The method can be operated at room temperature and the apparatus is simple. Although it is an appropriate method, it is necessary to use an adsorbent having a high ability to separate boron isotopes, and thus far a strong basic anion exchange resin, a weak basic anion exchange resin and an amino polyol type An anion exchange resin or the like has been used.

Meanwhile, the separation of boron isotopes based on the ion exchange reaction, boric acid (H ₃ BO ₃₎ and boric anions [B (OH) ₄ ^-] between equilibrium

Embedded image The equilibrium constant in this case is 1.019 (at 300 K) [see Bulletin of the Research Laboratory.
For Nuclear Reactors (Bulletin
of the Research Laborator
y for Nuclear Reactors) ",
Volume 2, pages 1 to 12 (1977)]. And
As can be seen from this equilibrium equation, since ¹⁰ B is abundantly present as a borate anion and ¹¹ B is abundantly present as boric acid, in strongly basic anion exchange resins and weakly basic anion exchange resins, B (OH) ₄ ^- for incorporation into the resin by the ion exchange, the concentrated ¹⁰ B in the resin, ¹¹ B is concentrated in the liquid phase. The isotope separation coefficient S at this time is given by the following equation.

(Equation 1) And its value is 1.007 to 1.019 [“Bull. Chem. Soc. Jpn.”, No. 50
Vol. 1, No. 158-163 (1977)
Year)], the upper limit of the isotope separation coefficient S of the boron isotope separating agent based on the anion exchange mechanism is the equilibrium constant in the isotope exchange reaction between boric acid and borate anion represented by the above formula (I). 1.019.

On the other hand, in the case of the aminopolyol type anion exchange resin, the adsorption mechanism is unknown, so that a detailed study cannot be conducted. However, the isotope separation coefficient S is about 1.015 to 1.020 (Japanese Patent Publication No. -68980, Japanese Patent Publication No. 4-6
No. 8981).

As described above, at present, the upper limit of the boron isotope separation coefficient is about 1.019. However, in order to efficiently separate boron isotopes by the adsorption method, an adsorption mechanism completely different from the anion adsorption mechanism is required. The mechanism requires the development of boron isotope separating agents with even higher isotope separation coefficients.

[0008]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides a method for efficiently and economically converting a boron isotope having a mass number of 10 and a boron isotope having a mass number of 11 from a boron isotope mixture. An object of the present invention is to provide a novel boron isotope separating agent having an excellent resolving power that can be easily separated.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to develop a novel boron isotope separating agent having excellent separation ability, and as a result, the boric acid represented by the above formula (I) From the equilibrium equation for the isotope separation between borate anions, ¹⁰ B is enriched in borate anion, while ¹¹ B is enriched in borate, borate has a planar triangular structure, borate anion since taking tetrahedral structure, ¹¹ B is the species planar triangular structure, whereas ¹⁰ B it is concentrated chemical species tetrahedral structure, also, the separation of boron isotopes, carried out in an aqueous system Is efficient and economical, and therefore, if boric acid having a planar triangular structure in an aqueous solution is incorporated into the separating agent resin as a boron species having a tetrahedral structure, ¹⁰ B is concentrated in the resin, and the aqueous solution is concentrated. ¹¹ that the B is concentrated in the, and such tetrahedral structure Capture of the retained boron resin,
It has been found that a chelating functional group having a specific structure can achieve this efficiently. The present invention has been completed based on such findings.

That is, the present invention provides a compound represented by the general formula:

Embedded image (R ¹ and R ² in the formula each represent a hydrogen atom or a carbon atom 1
-3 alkyl groups, which may be the same or different, and m and n are each 0 or 1). It is intended to provide a boron isotope separating agent comprising a molecular polymer.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer used as the separating agent of the present invention is a water-insoluble polymer having an aminodiol group represented by the above general formula (III) as a side chain in a water-insoluble polymer. In R ¹ and R ² in the formula (III), examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. R ¹ and R ² may be mutually identical or different, and m and n may be the identical to each other, may be different, in particular, R ¹ And R ²
And m and n are preferably the same.

Examples of the aminodiol group represented by the general formula (III) include a bis (2-hydroxyethyl) amino group, a bis (2-hydroxypropyl) amino group, a bis (2-hydroxybutyl) amino group, Screw (2
-Hydroxypentyl) amino group, bis (3-hydroxypropyl) amino group, bis (3-hydroxybutyl)
An amino group, a bis (3-hydroxypentyl) amino group,
Examples thereof include a 2-hydroxyethyl-2-hydroxypropylamino group and a 2-hydroxyethyl-3-hydroxypropylamino group. Among these, especially the screw (2
-Hydroxyethyl) amino and bis (2-hydroxypropyl) amino are preferred. One of these aminodiol groups may be introduced into the polymer, or two or more thereof may be introduced.

The basic skeleton of the high molecular polymer into which these side chains are introduced is not particularly limited, and can be arbitrarily selected from water-insoluble polymers known so far. It may be a copolymer.

The polymer having an aminodiol group represented by the general formula (III) can be produced by a known method. For example, in a suitable solvent such as dioxane and dimethylformamide, the general formula

Embedded image (Wherein R ¹ , R ² , m and n have the same meaning as described above)
Is reacted with a polymer having a chloromethyl group or an epoxypropyl group to produce a polymer having an aminodiol group represented by the general formula (III).

As the high molecular polymer having a chloromethyl group to be used at this time, for example, a polymer obtained by suspension polymerization of styrene and a crosslinking agent such as divinylbenzene is subjected to chloromethylation according to a conventional method. Can be used. Examples of the high-molecular polymer having an epoxypropyl group include, for example,
And those obtained by suspension polymerization of epoxy-1-propyl methacrylate and a crosslinking agent such as divinylbenzene, ethylene glycol dimethacrylate, and trimethylolpropane trimethacrylate.

The thus obtained general formula (III)
The high molecular weight polymer having an aminodiol group represented by the formula (1) is characterized in that two oxygen atoms of a hydroxyl group at the 2- or 3-position of the aminodiol group and a nitrogen atom of the amino group form a bicyclo ring with boron, and a hydroxide ion Is coordinated with boron, thereby maintaining a tetrahedral structure, and
Form one complex. Therefore, ¹⁰ B
Can be efficiently concentrated. In addition, this boron complex is formed in the range of pH 6 to 11 without being influenced by the composition ratio and concentration of boron and aminodiol group. Further, the boron isotope separation coefficient S of the polymer having an aminodiol group represented by the general formula (III) is usually in the range of 1.024 to 1.028, and is based on the conventional anion exchange. Upper limit of boron isotope separation coefficient S in boron isotope separating agent (1.019)
And has excellent boron isotope separation ability.

The boron isotope separating agent of the present invention comprises a water-insoluble polymer having an aminodiol group, and is used to separate a boron isotope mixture having a mass number of 10 from the boron isotope mixture. In order to separate the isotope ( ¹⁰ B) and the boron isotope ( ¹¹ B) having a mass number of 11 respectively, for example, an aqueous solution containing a boron isotope mixture and having a pH of about 6 to 11 and the boron isotope separating agent of the present invention are used. , Usually at room temperature. As a result, ¹⁰ B is concentrated in the separating agent, and ¹¹ B is concentrated in the aqueous solution. ^The separation agent that has adsorbed boron containing a large amount of ¹⁰ B can easily desorb the adsorbed boron by treating with a mineral acid.
As the mineral acid, usually, hydrochloric acid having a concentration of 0.05 to 2 mol / liter is preferably used. The separating agent thus treated with the mineral acid and from which the adsorbed boron has been desorbed can be used again for separating boron isotopes.

[0018]

Industrial Applicability The boron isotope separating agent of the present invention has an excellent separation ability as compared with a conventional ion isotope-based boron isotope separating agent. , ¹⁰ B and ¹¹ B can be separated efficiently and economically, respectively.

[0019]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 21.5 g of a chloromethylated styrene-divinylbenzene copolymer having a chloromethyl group content of 3.6 mmol / g
And 3.4 equivalents of bis (2-hydroxyethyl) amine with respect to the chloromethyl group of the copolymer were reacted in 100 ml of dimethylformamide at 100 ° C. for 4 hours to obtain bis (2-hydroxyethyl). A boron isotope separating agent comprising a styrene-divinylbenzene copolymer having an amino group [bis (2-hydroxyethyl) amino group content: 1.5 mmol / g] was produced.

1.71 g of this boron isotope separating agent was added to an aqueous solution (pH 6.8) containing 100 ppm of boron.
It was poured into milliliters and shaken at 25 ° C. for 7 days.
The boron adsorption after shaking was 0.17 mg / g.
The ¹⁰ B / ¹¹ B isotope molar ratio in the undiluted solution and the supernatant after the adsorption experiment was 0.2526 and 0.2505, respectively, as measured by a surface ionization mass spectrometer.

The isotope separation coefficient S is expressed by the following equation.

(Equation 2) (However, α and α ₀ are the isotope molar ratio ( ¹⁰ B / ¹¹ B) of the supernatant and stock solution after the adsorption experiment, and C and C ₀ , respectively)
Is the boron concentration of the supernatant and the stock solution after the adsorption experiment, respectively.) From these results, it is clear that the boron isotope separating agent of the present invention has a higher isotope separating ability than a conventional anion exchange resin.

Example 2 20.5 g of a chloromethylated styrene-divinylbenzene copolymer having a chloromethyl group content of 3.6 mmol / g
And 3.1 equivalents of bis (2-hydroxypropyl) amine with respect to the chloromethyl group of this copolymer were reacted in 100 ml of dimethylformamide at 100 ° C. for 4 hours to obtain bis (2-hydroxypropyl) amine. Styrene-divinylbenzene copolymer having amino groups [bis (2-hydroxypropyl) amino group content 1.2 mmol /
g] was prepared.

1.94 g of this boron isotope separating agent was added to an aqueous solution (pH 6.8) containing 100 ppm of boron.
It was poured into milliliters and shaken at 25 ° C. for 7 days.
The boron adsorption after shaking was 0.20 mg / g.
The ¹⁰ B / ¹¹ B isotope molar ratio in the undiluted solution and the supernatant after the adsorption experiment was 0.2526 and 0.2500, respectively, as measured by a surface ionization mass spectrometer.
When the isotope separation coefficient S was determined in the same manner as in Example 1, it was 1.027.

From these results, it is apparent that the boron isotope separating agent of the present invention has a higher isotope separating ability than a conventional anion exchange resin.

Continuing on the front page (72) Inventor Norio Takagi 2217-14 Hayashi-cho, Takamatsu-shi, Kagawa Prefecture Within the Institute of Industrial Technology, Shikoku Institute of Industrial Technology (72) Inventor Kenta Oi 22217-14, Hayashi-cho, Takamatsu-shi, Kagawa Prefecture (56) References JP-A-60-102948 (JP, A) JP-A-60-102946 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C07B 63/00 B01D 59/26 C01B 35/02 B01J 41/12

Claims (2)

(57) [Claims] 1. The functional group represented by the general formula: (R ¹ and R ² in the formula each represent a hydrogen atom or a carbon atom 1
-3 alkyl groups, which may be the same or different, and m and n are each 0 or 1). Boron isotope separating agent consisting of molecular polymer. 2. The method according to claim 1, wherein the functional group is bis (2-hydroxyethyl).
The boron isotope separating agent according to claim 1, which is an amino group or a bis (2-hydroxypropyl) amino group.