JP2000080492A - Molten electrolytic cell and method for recovering uranium from uranium-iron alloy using the same - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for recovering uranium from a uranium-iron alloy using a simple dry process, and a molten salt electrolytic cell used in the method. [Structure] The molten salt electrolyzer comprises a basket-shaped anode for accommodating a substance to be electrolyzed, a rotating cathode provided with a scraping device arranged opposite to the anode, and a scrape below the rotating cathode. And a tray disposed to receive the dropped electrodeposit. As a method of separating and recovering uranium from a uranium-iron alloy, a low melting point supporting salt such as KCl-LiCl is used as a supporting salt, a concentrated uranium-iron nugget is charged in an anode, and the nugget is dissolved in the anode. Uranium is electrodeposited as metallic uranium on the rotating cathode, the resulting deposit is scraped and collected, and iron is separated and collected as anode slime.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating uranium and iron from enriched uranium-alloy nuggets (thumb-sized chip-like alloys) as products obtained by an atomic laser enrichment method.

[0002]

2. Description of the Related Art An enriched uranium-iron alloy nugget obtained as a product by an atomic laser enrichment method has a large variation in the iron content derived from its manufacturing process, and the uranium amount is calculated and controlled by weight (metric control). Therefore, it was inevitable to dissolve nitric acid, change the form of uranyl nitrate solution, analyze uranium concentration, and manage uranyl nitrate based on this value.

[0003]

As a form in which uranium can be measured and controlled as a nuclear fuel substance, a pure metal or oxide having a small impurity content, a fluoride, a uranyl nitrate solution or the like can be considered. Various methods have been proposed as a method for converting from a uranium-iron alloy nugget having a variable iron composition to these forms. However, all of these methods involve a wet process, which makes the process complicated and low in actual processing. There is a problem that a large amount of concentration pollutants may be generated. In order to solve this problem, a conversion method using a dry method which does not require a complicated process is desired. However, there is no simple method as a dry process, and its development has been required.

Accordingly, it is an object of the present invention to provide a method for recovering uranium from a uranium-iron alloy using a simple dry process, and a molten salt electrolytic cell used in the method.

[0005]

In order to achieve the above object, the present invention provides a basket-shaped anode for containing a substance to be electrolyzed, and a rotating device provided with a scraping device arranged opposite to the anode. The present invention employs a molten salt electrolytic cell having a cathode and a tray disposed below the rotating cathode to receive the electrodeposit scraped off.

The present invention also provides a method of separating and recovering uranium from a uranium-iron alloy using a molten salt electrolytic cell of the type described above, wherein a low melting point supporting salt such as KCl-LiCl is used as a supporting salt. A charged uranium-iron nugget is charged into the anode, the nugget is dissolved in the anode in an inert atmosphere, and uranium is deposited as metal uranium on the rotating cathode, and the resulting deposit is scraped off and collected. Then, a method of separating and recovering uranium from a uranium-iron alloy, which is characterized by separating and recovering iron as anode slime, is adopted.

The present invention further provides a method for separating and recovering uranium from a uranium-iron alloy as described above, wherein the electrodeposit is heated and melted in an inert atmosphere to volatilize and remove coexisting supporting salts, thereby converting uranium to metal. It employs a method of separating and recovering uranium from a uranium-iron alloy, which is characterized in that it is recovered as uranium.

[0008]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, for example, an enriched uranium-iron alloy nugget is charged into an anode basket provided at the end of an electrolytic cell, and a large iron-made round bar having a rotation axis in a vertical direction is provided. Is disposed as a cathode, electrolysis is performed while constantly rotating at a low rotation speed, and metal uranium electrodeposited on the cathode surface is appropriately scraped off with a scraper. Then, the metal uranium scraped off is collected in a tray placed below the cathode. After energizing for a predetermined time, the tray is moved to the upper space of the electrolytic cell by an elevating device and collected. In addition, the iron cathode rod has a minimum distance between the anode basket and the anode basket in order to suppress a rise in voltage, and a diaphragm is provided between the anode and the cathode to prevent diffusion of the anode slime to the cathode.

Since the supporting salt is attached to the surface of the uranium metal thus obtained, pure uranium can be obtained by removing it by means of, for example, a distillation separation method. . On the other hand, a maximum of about 10% of iron contained in the concentrated metal uranium-iron nugget is not electrolytically dissolved due to a potential difference from uranium, and remains in the anode basket or is mixed in the supporting salt as anode slime. It does not migrate to the cathode due to the presence of the diaphragm between the cathode.

As the supporting salt used in the present invention, for example, those having a low melting point and a low boiling point such as KCl-LiCl are preferable from the viewpoint of energy cost. The electrodes used include stainless steel and iron.

Since the washing coefficient by electrolysis is usually about two digits, the iron content can be reduced from several percent to 0.1% in one operation. n%
To a degree. When the iron concentration is further reduced, it can be achieved by repeating electrolysis.

[0012]

Next, the present invention will be further described with reference to examples.

(Embodiment 1) FIG. 1 is a schematic sectional view of a molten salt electrolysis test apparatus used in this embodiment. The cathode of the molten salt electrolysis test apparatus 10 is an iron round bar 12 (diameter 5 cm, length 1).
0 cm) and the anode basket 14 (width 5 cm, length 5
cm and a height of 10 cm). As a simulated material for alloy nuggets, U-10
A 1.5 kg% Fe alloy chip (diameter 2 cm × thickness 1 cm: using natural uranium) was placed in an anode basket.
Then, the electrolytic bath 16 in the electric furnace 18 is constituted by using KCl-LiCl eutectic salt and adjusting the uranium concentration in the salt to 4% by weight,
It was charged in the electrolytic cell 20. While maintaining the inside of the electrolysis apparatus in an argon atmosphere, the temperature of the electrolyzer 20 was raised to 500 ° C. in the electric furnace 18 to dissolve the salt, thereby obtaining a melt. Thereafter, the salt was maintained at 500 ° C. for about 30 minutes to completely melt the salt, after which the electrolytic test was started.

In the electrolytic test, first, the anode basket 14 and the cathode 12 were pushed down, immersed in a molten salt, the cathode was rotated at a speed of 10 rpm, and the anode was rotated at a rotation speed of 20 rpm. After that, energize under the following conditions,
Constant current electrolysis was performed.

Electrolysis conditions: 100 A (potential fluctuation range: 1.5 to 2.
0V) energizing time 4 hours scraping once every 30 minutes

After 4 hours, the energization is stopped (total electricity is 400 AHr), and the anode basket 14 and the pan 22
Was raised to the upper space of the electrolytic cell, the heating of the electric furnace 18 was stopped, and the electric furnace 18 was cooled. The next day, after confirming that the electrolyzer was cooled to room temperature, the upper lid of the electrolyzer 20 was opened, and the anode basket 14 and the tray 22 were collected. The mixture of metal uranium and salt was taken out of the pan 22. The weight of this mixture was 1.330 g.

The mixture contained a considerable amount of salt, which was separated into a graphite crucible 32 coated with yttria and separated by a condenser 34 for condensing volatiles, as shown in FIG. It was placed in a box furnace 30 and heated to 1.330 ° C. in an argon atmosphere (inert atmosphere). The salt was volatilized and recovered in the recovery section, and the separated metal uranium was heated to a melting point or higher to form a crucible-shaped mass. The weight of the obtained massive metallic uranium was 1.150 g, and the current efficiency in the electrolytic purification was found to be 97%.

Impurity iron in the obtained metallic uranium is determined by ICP
As measured by emission spectroscopy, the iron content was 0.2%. When considering the error including the error, it was confirmed that this metal uranium is in a concentration range that can be sufficiently measured and controlled. On the other hand, most of the iron slime remained in the anode basket. Some slime was observed at the bottom of the basket.

From the above test results, it was confirmed that uranium and iron could be easily separated by molten salt electrolytic purification using a rotating cathode with a scraper and an anode basket.

Example 2 An electrolytic test was performed in the same manner as in Example 1 except that a porous ceramic diaphragm (not shown) was provided around the anode basket. The weight of the mixture of metal uranium and salt taken out of the saucer is 1.300 g
Met.

The mixture was 1.100 g of bulk uranium in the same manner as in Example 1, and the current efficiency in electrolytic purification was found to be 93%.

Impurity iron in the obtained metallic uranium is determined by ICP
As determined by emission spectroscopy, the iron content was 0.1%. From these results, the effect of the diaphragm is clear. In addition, most of the iron slime remained in the anode basket as in Example 1, and some slime was observed at the bottom of the basket.

[0023]

As described above, according to the present invention, from a concentrated uranium-iron alloy nugget obtained as a product by an atomic laser enrichment method, by a simple operation of molten salt electrorefining,
Iron can be removed from uranium, and it has become possible to convert it into a form of metallic uranium that can be measured and controlled.

The method of the present invention is applicable not only to enriched products but also to recovery of uranium metal from depleted uranium-iron alloys, and is a basic conversion process for effective utilization of uranium metal in the future. .

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a molten salt electrolysis test apparatus used in Examples of the present invention.

FIG. 2 is a schematic sectional view of a pox furnace having a condenser for condensing volatiles used in an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Electrolyzer 12 Cathode round bar 14 Anode basket 16 Electrolysis bath 22 Receiving tray 24 Scraper

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K001 AA10 AA33 BA23 DA06 DA14 GA19 4K058 AA21 AA28 AA30 BA01 BA40 BB05 CB03 EB04

Claims (5)

[Claims] 1. A basket-shaped anode for accommodating a substance to be electrolyzed, a rotating cathode provided with a scraping device facing the anode, and an electrodeposit scraped down below the rotating cathode. And a saucer arranged to receive the molten salt. 2. The molten salt electrolytic cell according to claim 1,
A molten salt electrolytic cell further comprising a diaphragm provided between the anode and the cathode. 3. The molten salt electrolyzer according to claim 1, wherein the substance to be electrolyzed is a uranium-iron alloy,
A molten salt electrolyzer, wherein the substance deposited on the cathode is uranium. 4. A method for separating and recovering uranium from a uranium-iron alloy using the molten salt electrolytic cell according to claim 1 or 2, wherein a low melting point supporting salt such as KCl-LiCl is used as the supporting salt. Into the enriched uranium-iron nugget is charged, the nugget is anodically dissolved in an inert atmosphere and uranium is deposited on the rotating cathode as metal uranium, and the resulting deposit is scraped and collected, A method for separating and recovering uranium from a uranium-iron alloy, wherein iron is separated and recovered as anode slime. 5. The method for separating and recovering uranium from a uranium-iron alloy according to claim 4, wherein the deposit is heated and melted in an inert atmosphere to volatilize and remove coexisting supporting salts, and the uranium is converted to metallic uranium. A method for separating and recovering uranium from a uranium-iron alloy.