JPS5816035A - Back extraction method for uranium - Google Patents

Abstract

PURPOSE:To improve back extraction rate considerably by using a centrifugal extractor for a back extractor, and an aq. ammonium carbonate for back extracting liq., and regulating the temps. of an org. solvent and the aq. ammonium carbonate soln. to specific temps. or above. CONSTITUTION:In the neighborhood of the outside circumference of a rotating body 2 under high speed revolution around the axial center of a revolving shaft 1, an org. solvent wherein amine type chemicals are dissolved in a diluting agent such as kerosene extracted with uranium is heated to about >=40 deg.C and is introduced on the outside circumferential side of the body 2 through an introduction passage 3, and an aq. ammonium carbonate soln. heated to the same temp. is introduced to the inside circumferential side of the body 2 through a back extracting liq. introducing passage 4. In the body 2, the continuous layer 6a on the org.solvent side is formed on the inside circumferential side of the body 2 with a main interface as a boundary and the continuous layer 6b of the aq. ammonium carbonate layer is formed on the outside circumferential side on account of a difference in specific gravity. The respective dispersed liquid drops 7a, 7b flow to the continuous layers 6a, b facing each other and collide against each other at the main interface 5, by which back extraction is progressed. The aq. ammonium carbonate wherein uranium is extracted is discharged through a discharge port 9.

Description

[Detailed Description of the Invention] The present invention relates to a method for back-extracting uranium in the process of smelting uranium by extraction operation], and in particular, a method for back-extracting uranium using an aqueous ammonium carbonate solution as a back-extraction liquid. This paper relates to a uranium back-extraction method suitable for

There are many methods for smelting uranium, such as the extraction method and the precipitation method. Among them, the 0-extraction method is widely used because the extraction method can obtain high-purity uranium. It consists of a process and a back extraction process. In the extraction process, uranium in the ore is extracted from an aqueous solution of uranium dissolved in a liquid such as sulfuric acid into an organic solvent that is sparingly soluble in water. This organic solvent, kerosene, or other solvent is used as a diluent, and in this diluent, an amine-based chemical that is an extractant for uranium,
For example, tri-normal octylamine (hereinafter referred to as Ta
In the back-extraction process, the organic solvent from which uranium was extracted is transferred from the uranium aqueous solution into an organic solvent and extracted by reacting with uranium and amines. The uranium moves from the uranium into the back extraction solution and is back extracted.

Conventionally, the back extraction solution was mainly a sodium carbonate aqueous solution, and
The back extractor used was a Michusu Shichito 2 type extractor. When a sodium carbonate aqueous solution is used as the back extraction solution, the pH of the sodium carbonate aqueous solution is stable, so the uranium back extraction (hereinafter abbreviated as "reverse extraction") operation is easy, and the uranium removal process is easy. While it has the advantage of not producing any process margins during production, it has the disadvantage of requiring many steps to remove impurities such as sodium during refining for use as nuclear reactor fuel. For this reason, recently, the application of ammonium carbonate aqueous solution as a back-extraction liquid, from which impurities can be easily removed in the repurification process, has been attracting attention. However, because the pH of the ammonium carbonate aqueous solution is high, when it comes into contact with ToOA, for example, fine droplets of the ammonium carbonate aqueous solution are dispersed in the organic solvent, causing wlo
It is said that an emulsion of m is generated. On the other hand, it is said that because it dissolves in an aqueous ammonium carbonate solution and forms a stable complex with the carbonate radical, it dissolves in the solution and does not generate precipitation, allowing for stable back extraction operations.

On the other hand, TnOA is weakly alkaline and P of the back extract.
If H is high, uranium is released and the uranium compound returns to the simple substance. In other words, as the back extraction progresses, as shown in Figure 1,
For example, when the pH of the back extraction liquid is 5 or higher, a back extraction rate of nearly 100 can be obtained.

The ammonium carbonate aqueous solution has a buffering effect, so even if a small amount of acid is mixed in, there is little change in pH, making it easy to carry out back extraction operations.Also, it does not cause uranium precipitation and allows for stable back extraction operations. Furthermore, since its pH is as high as 9.5,
As long as emulsilone does not occur, ammonium carbonate aqueous solution can be said to be an ideal back extraction solution.

Therefore, assuming a mixer settler type extractor conventionally applied to p back extraction, a 5000C bee force equipped with a hot water jacket equipped with stirring blades was used, and uranium was added to the experimental liquid.
fl/l containing organic solvent and ammonium carbonate 111
A person who performs a back extraction experiment using a mixture of ammonium carbonate aqueous solution with a concentration of 1 a.f.//l (quantity ratio 1:1.PH=9.5). Among the experimental conditions, the temperature of the experimental solution was 20°C and 30°C.
C. and 40.degree. C., a maximum total amount of 200 pprn of Emulsilon Breaker, which is soluble in the organic solvent and ammonium carbonate aqueous solution, was added separately or simultaneously to the organic solvent and the ammonium carbonate aqueous solution. In this case, the experimental solution was vigorously stirred with a stirring blade for 15 minutes, and after being allowed to cool for 10 to 40 minutes, the status of uranium back-extraction was checked. As a result, as has been said before, W/Q! An emulsion of It was generated, and uranium was back-extracted into this emulsion, but no back-extraction occurred in the aqueous ammonium carbonate solution. Therefore, when we further increased the standing time to about 3 hours, back extraction proceeded into the ammonium carbonate aqueous solution for the first time when the temperature of the experimental solution was 40°C. When back-extracting using a mixer-settler type extractor and an aqueous ammonium carbonate solution for the back-extracting liquid, after stirring,
It is necessary to leave the sample still for a long time, making reverse extraction extremely uneconomical in practice.

The present invention aims to solve the above problem, and uses a centrifugal extractor as the back extractor, an ammonium carbonate aqueous solution as the back extractant, and the temperature of the ammonium carbonate aqueous solution and the organic solvent is adjusted to around 40°C. It is an object of the present invention to provide a method for back-extracting uranium, which is characterized by adding soluble emulsilon breaker to an organic solvent and an aqueous ammonium carbonate solution separately or simultaneously.

An embodiment of the present invention will be explained with reference to FIG. 2 and experimental data. In addition, the centrifugal extractor is equivalent to the one commonly used, and the explanation will be omitted. An organic solvent is introduced through the organic solvent introduction path 3, and an aqueous ammonium carbonate solution is introduced into the vicinity of the inner circumferential side of the rotating body 2 through the back extraction liquid introduction path 4. Inside the rotating body 2, due to the difference in specific gravity, an organic solvent-side continuous layer 61 is formed near the inner circumferential side of the rotating body 2 with the p main interface 5 as a boundary;
A continuous layer 6b on the ammonium carbonate aqueous solution side is formed near the outer circumferential side, and the respective dispersed droplets ja, 7b flow to the opposing continuous layers 6g, 6b and collide at the main interface 5, so that back extraction proceeds. Thereafter, the aqueous ammonium carbonate solution from which uranium has been extracted is led out of the machine through a back-extraction liquid outlet 8, and the organic solvent from which uranium has been extracted is led out through an organic solvent outlet 9.

When performing back extraction using an ammonium carbonate aqueous solution as the back extraction liquid, a particularly important point is how to break down the generated emulsilone. It is necessary to successfully coalesce the 7 m of dispersed droplets that are dispersed and suspended in the continuous layer 6b on the ammonium carbonate aqueous solution side. In this method, the dispersed droplets 7a
, 7b to collide with each other to increase their size so that they flow easily toward the respective continuous layers 6m and 6b facing each other, and the dispersed droplets 7a
There is a method of applying force to the ammonium carbonate aqueous solution to make it easier to flow toward the continuous layer 6b on the ammonium carbonate aqueous solution side.

Adding Emulsilon Breaker is the former method.
This has the effect of promoting enlargement of the dispersed droplets 7a, 7b due to collision. However, the dispersed droplets 7a.

If 7b is a fine line, there is little chance of collision, and even if an emulsion breaker is added, the dispersed droplet is 7 m.

It takes a long time for 7b to increase in size, making it difficult for Emulsilon to disintegrate. This corresponds to the case using the conventional Michuset 2 type extractor. On the other hand, in the case of using a centrifugal extractor, which corresponds to the latter method, centrifugal force is applied to the dispersed droplets 7m + 7b, making them easier to flow toward the opposing continuous layers 6m and 6b, so that the dispersed droplets 7m and 7b collide. Therefore, it becomes easy to coalesce the dispersed droplets 7m into the continuous layer 6b on the ammonium carbonate aqueous solution side. However, even in the case of using a centrifugal extractor, if the dispersed droplets 7m and 7b are extremely fine, there is less chance of collision), and the dispersed droplets 7a coalesce into the continuous layer 6b on the ammonium carbonate aqueous solution side and separate. However, when performing back extraction using a centrifugal extractor, it is necessary to select operating conditions that facilitate the coalescence of 7 m of dispersed droplets to the ammonium carbonate aqueous solution side.

Therefore, a centrifugal extractor with a throughput of 31/jlL was used as the back extractor, and the experimental solution was an organic solvent containing e9/l of uranium and an ammonium carbonate aqueous solution with a concentration of xaof// of ammonium carbonate (1:1 ratio). 1. Using PH=9.5),
The temperature of the experimental solution was 20°C and 30°C.

Four conditions were used: 35°C and 40°C, and a maximum total amount of 200 pp of emulsion breaker soluble in an organic solvent and an ammonium carbonate aqueous solution, either separately or simultaneously, was used.
m was added and a back extraction experiment was performed.

As a result of the experiment, when the emulsion breaker was not added, Emulsilone did not collapse and back extraction did not proceed when the temperature of the experimental solution was 20°C, 30°C, and 35°C, but when the temperature of the experimental solution was 40°C, , within the residence time of the organic solvent and ammonium carbonate aqueous solution in the centrifugal extractor (from several seconds to 1 to 2
The back extraction proceeded in about 1 minute), and a back extraction rate of 999G was obtained. In addition, in the case of adding emulsion breaker, back extraction proceeded within a short residence time of the organic solvent and ammonium carbonate aqueous solution in the centrifugal extractor, regardless of the temperature of the experimental solution, and a back extraction rate of 99% was obtained. . However, if the total amount of emulsine breaker added was less than 5 ppm, it was not effective in disintegrating emulsine, and if the total amount added was 200 ppm, the addition of emulsine breaker had the opposite effect.Emulsillone was generated in the continuous layer on the ammonium carbonate aqueous solution side.

As explained above, the present invention uses a centrifugal extractor as a back extractor, an ammonium carbonate aqueous solution as a back extractant, and regulates the temperature of the organic solvent and ammonium carbonate aqueous solution to around 40°C or higher, or Add soluble emulsilon breaker to the solvent and ammonium carbonate aqueous solution separately or simultaneously. ,
This has the effect of being able to disintegrate emulsilon in an extremely short period of time and allowing uranium to be back-extracted with an extremely high back-extraction rate.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the back extraction 1iPH and the back extraction rate obtained in the Mixamoto type 2 extractor phase determination experiment, and Fig. 2 is a diagram illustrating an embodiment of the present invention. It is a diagram of the reverse extraction situation of uranium. l... Rotating shaft, 2... Rotating body, 3...
... Organic solvent introduction path, 4 ... Reverse extraction liquid introduction path, 5 ... Main interface, 6a ... Organic solvent side continuous layer, 6b ... ...Continuous layer on ammonium carbonate aqueous solution side, 1 field, 7b...Dispersed droplets, 8...
・Reverse extraction liquid outlet path, 9...Organic solvent outlet path v'
10 al

Claims (1)

[Claims] 1. In a method of back-extracting uranium extracted into an organic solvent in which an amine-based chemical is dissolved in a diluent such as kerosene using an aqueous ammonium carbonate solution as a back-extracting liquid, Use a type extractor to control the temperature of the organic solvent and ammonium carbonate aqueous solution to around 40°C or higher during the back extraction of uranium! A method for reverse extraction of uranium as an image. 2. In a method of back-extracting uranium extracted into an organic solvent in which an amine-based chemical is dissolved in a diluent such as kerosene using an ammonium carbonate aqueous solution as a back-extracting liquid, a centrifugal extraction tank is used as the back-extracting machine and the method described above is used. At the time of back-extraction of uranium, adding a soluble industrial carbonate solution to the organic solvent and the ammonium carbonate aqueous solution separately or simultaneously.
Reverse extraction method of uranium as mold. 3. The total amount of the emulsion sprayer added is 5 to 2.
The method for back-extracting uranium according to claim 2, wherein the uranium concentration is 00 ppm.