JPS5815167B2 - Douitainotenkaibunrihouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention improves the separation efficiency by using anion exchange resin particles having a specific particle size in the operation of separating uranium isotopes using an anion exchange resin. This paper relates to a method for separating uranium isotopes.

An operation to separate uranium isotopes by using an anion exchange resin as an adsorbent, oxidizing the uranium adsorption zone in the development column in the front direction in the flow direction, and reducing it in the rear while developing the adsorption zone in a substituted state. The operation of separating uranium isotopes by developing an adsorption zone in a displacement state while reducing the uranium adsorbent in the column at the rear in the flow direction is disclosed in Japanese Patent Application Laid-open No. 49-5.
No. 7297.

As a result of our study and analysis of methods for stably performing separation operations and increasing separation efficiency, the present inventors have found that the oxidizing agent zone, uranium zone, and reducing agent zone can be stably maintained throughout the deployment. It is important to maintain the oxidation and reduction interfaces in a clear state, to ensure that the adsorbed uranium in the uranium zone has a sufficiently large adsorption power compared to the adsorption power of other coexisting anions, and to use a porous adsorbent. I found out that things like being desirable are important.

As a result of considering a more efficient method that satisfies these requirements, the present inventors found that the volume average particle size of all particles of anion exchange resin particles used as an adsorbent is closely related to separation efficiency. We have discovered that particles with a specific range of particle sizes can achieve even higher separation efficiencies.

Anion exchange resins are already widely used industrially, and a large number of granular products are commercially available.

Most of these exchange resin particles have a particle size of 0.2 mm or more and 1 mm or less.

This is because it is widely known that particle sizes within the above range are useful for normal uses.

As a result of investigating the relationship between the efficiency of the substitution expansion separation method for uranium isotopes and particle size, the present inventors found that, firstly, the separation efficiency depends on the volume average particle size, and secondly, the particle size Range is 160
It was discovered that micron to 50 micron is effective.

That is, the present invention provides an interface between (A) a uranium zone and an adjacent reducing agent zone in a system in which an ion exchanger exists; or (B) an interface between a uranium zone and an adjacent oxidizing agent zone. Interface: Or in the uranium isotope separation method that separates isotopes while performing redox at both interfaces (A) and (B), it is used as an anion exchanger in granular form, and the volume average particle size of all particles is from 160 microns. A method for separating uranium isotopes is provided, characterized in that it uses an anion exchange resin of up to 50 microns.

A more preferred particle size range is 90 microns to 50 microns, with the region giving the best efficiency being 75 microns to 50 microns.

Although the theory of systematic separation efficiency in substitution expansion separation methods is not yet complete, the field of separation methods commonly known as elution chromatography has been studied in considerable detail, and it is believed that one of the factors governing separation efficiency is , there is a concept of a virtual molecular disorder region based on the drunk walking theory.

Based on this concept, if we analyze the present invention, as the particle size becomes smaller, the turbulence in the direction of development of the liquid phase and the turbulence of the flow path in the direction perpendicular to the direction of development of the liquid phase become larger, while adsorption increases. The diffusion disturbance of the band becomes smaller.

In the large particle size range, disturbance of the adsorption zone is thought to be the main cause, and extremely effective separation is achieved when the particle size is less than 160 microns.

On the other hand, if smaller particle sizes are used, turbulence of the liquid phase becomes dominant, and below 50 microns no effective separation is achieved.

In addition, for anion exchange resins with particle sizes in this range, it is difficult to synthesize resin particles with a completely uniform particle size distribution, so it is difficult to synthesize resin particles with a completely uniform particle size distribution, so whether the particle size is based on volume, surface area, or diameter is It was determined that it was correct to adopt the volume-based particle size after considering whether the particle size was dominant.

Measurement of resin particle size must be performed using a reliable method.

According to the studies conducted by the present inventors, anion exchange resin particles can be suspended in water or oil because their shape, apparent specific gravity, true specific gravity, liquid composition of solution, temperature, etc. change significantly. Great care must be taken when measuring the particle size distribution.

One way to determine this is to immerse the particle in the liquid used or a very similar liquid, photograph it with a microscope, and analyze the image; another method is to measure the size of each particle. It's a method.

For the former, a general-purpose optical microscope and photomicrograph are sufficient;
For the latter, it is possible to use an electrical conductivity displacement measurement type particle size distribution measuring device that counts each particle passing through the pores and electrically captures the particles.

Examples of preferred specific embodiments of the present invention include (1)
A reducing agent solution is infiltrated into the uranium adsorption zone of the anion exchanger, and an interface is formed between the uranium adsorption zone and the reducing agent zone while reducing hexavalent uranium ions to tetravalent uranium ions,
An operation to perform isotope separation near the interface; (2) A uranium solution is infiltrated into the oxidizer zone of the anion exchanger, and the uranium solution is oxidized into the oxidizer zone and uranium adsorption zone while oxidizing tetravalent uranium ions to hexavalent uranium ions. and (3) a method including both operations described in (1) and (2) above.

Separation of uranium isotopes in these operations begins within the uranium adsorption zone near the reduction interface and/or the oxidation interface with the onset of evolution.

As the uranium adsorption zone develops in a substituted state, separation near the interface progresses, and at the same time, the separated zone advances into the uranium adsorption zone.

After appropriate development, a separated product stream of the desired composition can be obtained by collecting the uranium near the interface or in the entire zone where separation is proceeding.

The uranium used in the present invention is uranium with a mass number of 235 (
(abbreviated as U235) and uranium with a mass number of 238 (U2
It is a mixture of uranium isotopes whose main component is uranium isotope (abbreviated as 38), and the abundance ratio of each is not limited.

The oxidized uranium used in these operations is positively charged uranium in its ionized state, which is usually
Two oxygen atoms are bonded together and exist in the form of UO2 with a positive valence.

This is called uranyl, and in the present invention, a complex in which a negatively charged ligand is coordinated to a uranyl ion is used in order to have adsorption power to an anion exchange resin.

Uranium in a reduced state is ionized uranium with a positive valence, and is called uranium. In the field of use of the present invention, it generally exists as a complex coordinated with a negatively charged ligand.

Both uranyl and uranas exist as a mixture of complexes with different coordination numbers, so it is impossible to accurately determine the solution valency; however, in the area of use of the present invention, uranyl exists as a complex. Exists as an anion.

Since resin particles having a relatively small particle size are used in the practice of the present invention, it is preferable to synthesize the resin particles by the method described below.

A known structure of the anion exchange resin can be used.

Typical resin particles are addition copolymers, condensation polymers, graft polymers, etc. In addition copolymers, styrene, ethylvinylbenzene, chlorostyrene, chloromethylstyrene, styrene derivatives such as trifluorostyrene, acrylonitrile, etc. , acrylic acid, methacrylic acid, dimethylamine ethyl methacrylate, methyl vinyl ketone vinyl chloride, vinyl chloride, acrylamide, epoxybutadiene, vinyl pyridine, vinyl imidazole, N-vinyl succinimide, N-vinylphthalimide, vinyl quinoline diacrylamine, divinyl Benzene, trivinylbenzene, trivinyl isocyanurate, divinylsulfonetriallylamine, etc. are used.

In addition, as the condensation polymer, phenol, formalin, high molecular weight and low molecular weight amines such as polyethyleneimine and hexamethylene diamine, and bifunctional crosslinking agents such as epichlorohydrin, dibromoethane, and jepoxy compounds are used.

In addition, polyethylene, polystyrene, etc. are synthesized and molded using a molding machine, or dispersed in the form of oil droplets to form a matrix, which is then made into an anion exchange resin through crosslinking, polymer reaction, etc.

Furthermore, compounds that have an anion exchange group and can be easily introduced into the base material by a method such as grafting are synthesized to synthesize a compound that has an anion exchange ability on the surface layer,
Resins in which only the surface is changed to exchange groups are also useful.

When synthesizing using oil-soluble monomers or polymers, gum arabic, alginate, methylcellulose, starch, carboxymethylcellulose,
Mucilage substances such as gelatin, synthetic polymers such as polyacrylates, polyvinyl alcohol, and polyvinylpyrrolidone are often used.

In this case, the viscosity increases and it is often difficult to synthesize particles with a uniform and small particle size, so either choose a polymer with a small molecular weight or keep the concentration low to increase the viscosity. You need to be careful not to let this happen.

Under these circumstances, it is often effective to add inorganic salts such as magnesium aluminum silicate, hydrated magnesium silicate, titanium oxide, calcium carbonate, talc, barium sulfate, and calcium phosphate.

In the case of water-soluble monomers, it is preferable to use sorbitan esters, sorbitan ester ethers, fatty acid monoglycerides, etc., while suppressing the use of polymeric suspending agents such as polyvinyl chloride and polymethyl methacrylate.

More preferable compositions of the resin used in these suspension polymerization, emulsion polymerization, and bulk polymerization include styrene, vinyltoluene,
A crosslinked polymer synthesized by addition copolymerization using ethylvinylbenzene and divinylbenzene as main components, chloromethylated and aminated; monomers with active groups such as chloromethylstyrene, methylethylketone, epoxybutadiene, acrylamide, etc. and aminated copolymers containing crosslinking monomers such as divinylbenzene and triallylisocyanurate as main components; N-vinylsuccinimide, N-vinylphthalimide, vinylcarbazole, vinylimidazole, vinylpyridine , vinyltetrazole, vinylquinoline, divinylpyridine, etc. whose main component is a monomer having nitrogen that can be used as an exchange group and copolymerized with a crosslinking monomer as necessary, and their reactants; polyethyleneimine, hexamethylene Examples include anion exchange resins such as condensation polymers of amines such as diamines and polyfunctional compounds.

The ligands and pH adjusters used in the present invention include inorganic acids such as hydrofluoric acid, hydrochloric acid, bromic acid, nitric acid, thiocyanic acid, hydrocyanic acid, phosphoric acid, chloric acid, and hydrobromic acid, and salts thereof. ; formic acid,
Monovalent carboxylic acids such as acetic acid, monochloroacetic acid, dichloroacetic acid, butyric acid, propionic acid, valeric acid; divalent carboxylic acids such as oxalic acid, malonic acid, maleic acid, phthalic acid, fumaric acid; glycolic acid, β- Oxypropionic acid, lactic acid,
Oxyacids such as oxysuccinic acid, tartaric acid, citric acid, and sulfosalcylic acid; glycine, alanine, β-alanine,
Amino acids such as aspartic acid and glutamic acid; organic acids such as amine polycarboxylic acids such as nitrosotriacetic acid and ethylenediaminetetraacetic acid; and salts thereof.

Additives such as various solvents and stabilizers can be used when carrying out the method of the present invention.

For example, acetone, methyl ethyl ketone, dioxane, imidazole, 2-mercaptoethanol, ethylenediamine, thioglycolic acid, methanesulfonic acid, acetonylacetone, sulfamic acid, nitromethane, dimethylacetal, diethylene glycol.

Picolinate, ethylene glycol, propyl alcohol, tetrahydrofuran, pyridine, monoethanolamine, 2-aminopyridine, 3-amino-1,2,4-
1-lysyl, piperazine, methylcellosolve, t-butyl alcohol, dimethylformamide, N-methylformamide, acetonitrile, acetylacetone, urea, oxine.

etc.

The oxidizing agent used in the present invention is not particularly limited, but may include: ■valent copper, ■valent manganese, ■valent iron, ■valent thallium, ■
valence cerium, ■ valence vanadium.

Molybdenum with a valence of 1 is preferred.

The reducing agent used in the present invention is not particularly limited, but it is preferably ``tin'', ``vanadium'', ``titanium'', ``molybdenum'', or ``chromium''.

As the developing medium for the oxidizing agent, reducing agent, uranium compound, etc. of the present invention, water, a polar compound, or a mixture thereof is used, and an oil-soluble liquid is also added if necessary.

The development conditions of the present invention are not limited, but the development temperature is from 5°C to 280°C, the development pressure is from normal pressure to 80 atm, and the fluid gland velocity is:
The speed range is from 5 cm/day to about 80 m/hr.

Reference Example 1 A stirrer, thermometer, and reflux condenser were attached to a 51-sized four-bottle flask, and hydroxypropyl methylcellulose (21% methoxy groups, 8% hydroxypropoxy groups, 2% viscosity when dissolved, 15.000 g, Average molecular weight 1
43,000), 10 g of common salt were dissolved and added, followed by 800 g of styrene in which 12 g of lauroyl peroxide was dissolved, 90 g of ethylvinylbenzene,
110g of divinylbenzene, 800g of methyl benzoate,
Added a mixture of 230g of n-butanol and heated for 120r
Oil droplets were formed while stirring with pl, and polymerization was carried out at 50° C. for 28 hours.

After polymerization, it was washed with methyl alcohol and water and dried, followed by chloromethylation with chloromethyl ether and tin chloride, and then amination with a 30% ethanol solution of diethylamine.

The exchange capacity of this resin is 4.15 mlJ equivalent/g,
The resin number was 001.

Reference Example 2 Using the same equipment, procedure, method, and conditions as in Reference Example 1 (excluding the stirring rotation speed during polymerization), polymerization was performed using a liquid with the following composition, followed by chloromethylation and amination. .

This resin is designated as 002. Reference Example 3 Using the same apparatus, procedure, method, and conditions as in Reference Example 1 (excluding the rotation speed during polymerization), polymerization was carried out using a liquid having the following composition, and chloromethylation and amination were performed.

This resin is called 003.

Reference Example 4 Polymerization and reaction were carried out in the same manner as in Reference Example 1, and resin (004
) was synthesized.

The composition of the polymerization solution is as follows.

Reference Example 5 Polymerization and reaction were carried out in the same manner as in Reference Example 1, and resin (005
) was synthesized.

The composition of the polymerization solution is as follows.

The resins of Reference Examples 1 to 5 were added to 5N hydrochloric acid with 0% uranyl.
．． Uranium was adsorbed by equilibration with a 2M solution, and the particle size was measured by taking an optical microscope photograph to calculate the volume average particle size.

In addition, each resin was separated into two types using a centrifugal sedimentation type general-purpose classifier.
divided into two parts.

Among the resin groups after division, the smaller particle size is given the suffix ``■'', and the larger particle size is given the suffix A.

The results are shown in Table 1. Example 40 ml of each of the resins of Reference Examples 1 to 5 was placed in a pressure-resistant glass developing tower with a cylindrical filter having a diameter of 8 mm and a length of 1200 mm.
Filled.

After adjusting the resin with 5NHC7, 0.5M ferric chloride was supplied and adsorbed to the resin, and 0.2M uranus was added to 30
ml is supplied to form an adsorption zone, and then 0.
Developed by feeding 1M titanium chloride.

The liquid flowing out with the development was divided and collected in 1 ml portions, and the liquid near the oxidation interface and the liquid near the reduction interface were subjected to a mass spectrometer to measure the isotope ratio of uranium-235.

The isotope ratio of the supplied uranium-235 is 0.007.
It was 252.

Claims (1)

[Scope of Claims] 1. (A) an interface between a uranium adsorption zone and an adjacent reducing agent zone in a system where an anion exchanger exists; or (B) an interface between a uranium adsorption zone and an adjacent oxidizing agent zone; interface; or in a uranium isotope separation method in which isotopes are separated while performing redox at both interfaces (A) and (B),
A method for separating uranium isotopes, characterized by using granular anion exchange resin particles having a volume average particle size of all particles in the range of 160 microns to 50 microns.