JPH054930B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for separating and purifying uranium and rare earth elements, and more specifically, to efficiently separate uranium and rare earth elements with simple operations. The present invention relates to a method for separating and refining uranium and rare earth elements, which can be suitably used, for example, in the field of nuclear fuel production.

[Prior art and its problems] For example, in the field of manufacturing nuclear fuel using uranium and rare earth elements, such as uranium and gadolinium mixed pellets, residual materials and inspection residues due to pellet breakage or mixing errors during the manufacturing process occur. Sample regeneration is essential.

Conventional separation and purification methods for uranium and rare earth elements include precipitation methods that utilize purification effects such as hydrogen peroxide precipitation and oxalic acid precipitation, ion exchange methods that use cation exchange resins or anion exchange resins, and tributyl Solvent extraction methods using solvents such as phosphate (TBP) have been used.

However, all of these conventional methods are extremely complicated to operate, use a large amount of acid or alkali, and require equipment comparable to the original separation process for the purpose of preventing environmental pollution and post-processing. As a result, there was a problem in that the entire equipment became larger.

In addition, these conventional methods have had the problem that it is difficult to separate rare earth elements in trace amounts of about ppm.

[Objective of the Invention] The object of the present invention is to solve the above-mentioned problems, to be able to efficiently separate uranium and rare earth elements with a simple operation, to eliminate the need for large-scale equipment, and to separate trace amounts of rare earth elements. Another object of the present invention is to provide a method for separating and purifying uranium and rare earth elements, which can also be separated.

[Means for achieving the above-mentioned object] In order to achieve the above-mentioned object, the present inventor has made extensive studies and found that if a specific wet treatment is carried out, it is possible to achieve the above-mentioned object without the need for large-scale equipment. The present invention was achieved by discovering that uranium and rare earth elements can be easily and efficiently separated, and even trace amounts of rare earth elements can be separated.

That is, the outline of this invention is that after adding aminopolycarboxylic acid to an acidic solution containing uranium and rare earth elements, uranium is converted into ammonium deuterate (ADU) by further adding aqueous ammonia and/or ammonia gas.
This is a method for separating and purifying uranium and rare earth elements, which is characterized by precipitation of uranium and rare earth elements.

Examples of the acidic solution include nitric acid, hydrochloric acid,
Oxidizing or non-oxidizing inorganic acid solutions such as sulfuric acid, hydrogen sulfide, carbonic acid, chloric acid, phosphoric acid, perchloric acid, chlorous acid, hypochlorous acid, nitrous acid, and sulfurous acid, and mixed solutions thereof, acetic acid, Examples include solutions of organic acids such as carboxylic acids, oxycarboxylic acids, and dicarboxylic acids, such as formic acid, citric acid, and tartaric acid, and mixed solutions thereof.

These may be used alone or in combination of two or more.

The acidic solution is used after adjusting its pH to 4 to 6, preferably 5.2±0.1. When the pH is outside this range, it may become difficult to mask the rare earth element by forming a selective chelate between the rare earth element and the aminopolycarboxylic acid.

Examples of the aminopolycarboxylic acids include ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), trans-1,2
- cyclohexanediaminepentaacetic acid (CyDTA),
Examples include ethylene glycol bis(2-aminoethyl)etherdiaminetetraacetic acid (GEDTA), triethylenetetraminehexaacetic acid (TTHA), nitrilotriacetic acid (NTA), and hydroxyethylethylenediaminetriacetic acid (EDTA-OH).

In this way, what is collectively called aminopolycarboxylic acids are polyamine compounds that are ethylenediamine derivatives, namely ethylenediamine (En),
A carboxylic acid group (-
COOH), and the polyamine compound is a very limited metal (e.g. Cu, Ni, Co, Zn,
It forms stable chelates with many metals, whereas it only forms stable chelates with other metals (Cd, Hg, etc.).

In addition, the said amino polycarboxylic acid can also be used individually by 1 type, and can also be used in combination of 2 or more types.

Among these, preferred are EDTA,
It is DTPA.

In this invention, the rare earth element is masked by adding the aminopolycarboxylic acid in a small excess relative to the expected rare earth element in the acidic solution.

Specifically, acetate (NaAc, NH ₄ Ac, etc.)
Adjust the pH to 5.2 ± 0.1 by adding EDTA or
Add DTPA, further add excess to 0.001-1.00M, preferably 0.002-0.005M, then add ammonia water or ammonia gas,
causing precipitation of ADU.

When adding the ammonia water and/or ammonia gas, the pH of the solution after addition is 8.
Adjust to ~10, preferably 9. Although ADU will occur even if the pH is higher than 10, it will contain more salts, so a pH of 9 is best when considering this post-treatment.
Also, due to this treatment, iron, nickel, copper, zinc, aluminum, etc. contained as impurities behave in the same way as rare earth elements.

The generated ADU precipitate can be separated from the solution by conventional methods such as a filter paper method, a suction filtration method, a centrifugation method, and the like.

On the other hand, the rare earth element in the solution can be recovered as an oxide by making it acidic using nitric acid or hydrochloric acid, evaporating it to dryness to volatilize most of the salts, and then sintering it.

ADU separated by the method of this invention can be converted to UO ₃ or U ₃ O ₈ by torrefaction.
This roasting temperature is usually 350 to obtain UO ₃
~550°C, and when obtaining U ₃ O ₈ , the temperature is usually 550°C or higher.

Additionally, depending on the intended use these UO ₃ or
UO ₂ can be obtained by reducing U ₃ O ₈ .

The rare earth elements separated by the method of this invention are
It can be used as it is, for example, as a raw material for producing uranium/rare earth mixed pellets.

[Effects of the invention] According to the invention, (1) operation is extremely simple, (2) the device does not become large, and (3) it is possible to remove trace amounts of rare earth, which was difficult with conventional methods. It is possible to efficiently separate similar elements,
It is possible to provide a method for separating and purifying uranium and rare earth elements, which has various effects such as.

[Example] Next, Examples of the present invention will be shown and the present invention will be explained in more detail.

(Example 1) Nitric acid solution containing 96g of uranium and 4g of gadolinium
After adjusting the pH to 5.2, 10 g of diethylenetriaminepentaacetic acid (DTPA) was added to this solution.

Next, 7N ammonia water was added dropwise to adjust the pH to 9 and the total liquid volume to 5. By filtering this, 134 g of ammonium deuterate (ADU) precipitate was obtained. Then, the precipitation of the obtained ADU is
Conversion to U ₃ O ₈ was performed by roasting at a temperature of 850±50° C. to obtain 113 g of U ₃ O ₈ .

When the amount of gadolinium in this U ₃ O ₈ was measured by ion exchange separation - oxine - TTA extraction - emission spectrometry, it was found that the amount of gadolinium had decreased to 0.2 ppm.

(Example 2) 110g of U ₃ O ₈ obtained in Example 1 was added to 7N nitric acid.
Add 1 g of diethylenetriaminepentaacetic acid (DTPA) to this solution after dissolving in 100 ml and adjusting the pH to 5.2.
added.

Next, add ammonia water to adjust the pH to 9.
130 g of ammonium deuterate (ADU) precipitate was obtained by filtration.

Thereafter, ADU was converted in the same manner as in Example 1 to obtain 93 g of U ₃ O ₈ .

When the amount of gadolinium in this U ₃ O ₈ was measured, it was found that the amount of gadolinium had decreased to 0.05 ppm or less.

(Example 3) The procedure was carried out in the same manner as in Example 1, except that ethylenediaminetetraacetic acid (EDTA) was used instead of diethylenetriaminepentaacetic acid (DTPA), and 113 g of U ₃ O ₈ was Obtained.

The amount of gadolinium in the obtained U ₃ O ₈ was reduced to 0.3 ppm.

(Example 4) In Example 4, U ₃ O ₈ obtained in Example 2 was replaced with U ₃ O ₈ obtained in Example 1.
The procedure was carried out in the same manner as in Example 2 except that 113 g of U ₃ O ₈ was obtained.

The amount of gadolinium in the obtained U ₃ O ₈ is 0.03 ppm
It had decreased to

Claims (1)

[Claims] 1 Uranium characterized by adding aminopolycarboxylic acid to an acid solution containing uranium and rare earth elements, and then further adding aqueous ammonia and/or ammonia gas to precipitate uranium as ammonium deuterate. A method for separating and purifying rare earth elements.