JPH1053888A - Method for recovering metallic material to be recovered of fused salt electrolytic device and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain the improvement in recovery efficiency by simplification of recovery operation with the improvement in the precipitation rate of metal uranium. SOLUTION: An anode basket 3 and cathode drums 4 are arranged in the fused salt 2 injected into an electrolytic cell 1. Nearly the lower half parts of the cathode drums 4 are held immersed in the fused salt 2 and the drums have revolving shafts in a horizontal direction. The metal uranium precipitated on the outer peripheral surfaces of the cathode drums 4 by an electrolysis is scraped by scrapers 6 existing above the liquid surface of the fused salt 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electrolytically refining spent metal uranium fuel and impure metal uranium, and for recovering a metal material to be recovered such as metal uranium in a molten salt electrolysis apparatus for electrowinning metal uranium and the like. Method and apparatus.

[0002]

2. Description of the Related Art In a conventional method for recovering metallic uranium and the like in a molten salt electrolytic refining apparatus for dry reprocessing of metallic uranium and the like, a round bar having a rotating shaft in a vertical direction is used to deposit a dendritic metal. Uranium has been recovered in a state where it is adhered to the solid cathode, or metal uranium deposited on the surface of the solid cathode has been scraped off in a molten salt using a cylindrical solid cathode.

[0003]

When a round bar-shaped solid cathode having a rotation mechanism having a rotation axis in the vertical direction is used, it is necessary to increase the cathode area due to structural restrictions of the electrolytic cell. Therefore, it was almost impossible to increase the deposition rate of metallic uranium and the like.

On the other hand, if a cylindrical solid cathode is used, it is relatively easy to increase the area of the cathode, and it is therefore possible to increase the deposition rate of uranium metal and the like. In this case, the metallic uranium and the like are recovered by being scraped in the molten salt, but the scraping of the metallic uranium and the like in the molten salt requires a complicated operation, and thus the recovery efficiency of the metallic uranium and the like is not necessarily improved. I didn't. As described above, in the conventional metal purification by molten salt electrolysis, there is a relationship in which the improvement of the deposition rate of uranium metal and the like and the simplicity of the operation of recovering uranium metal and the like cannot be compatible.

The present invention has been made in view of such problems in the conventional metal refining by molten salt electrolysis, and improves the rate of precipitation of metal uranium and the like and improves the recovery efficiency by simplifying the recovery operation. An object of the present invention is to provide a method and an apparatus for recovering a metal substance to be recovered in a molten salt electrolysis apparatus that can achieve both improvements.

[0006]

In order to achieve this object, an apparatus according to the present invention comprises an electrolytic cell containing a molten salt solution in which a metal substance to be recovered is dissolved; At least one cathode drum disposed in the electrolytic cell so as to be immersed therein and having a rotation axis in the horizontal direction, an anode immersed in the molten salt solution, and deposited on the surface of the cathode drum A scraping device for scraping the metal material to be recovered above the liquid level of the molten salt solution.

Further, the method according to the present invention is arranged such that at least a part of the surface is immersed in the molten salt solution in the electrolytic cell containing the molten salt solution in which the metal substance to be recovered is dissolved; Rotating the cathode drum so that the rotation axis is horizontal; and electrolyzing the molten salt solution by energizing an anode immersed in the molten salt solution; and Scraping the deposited metal substance to be recovered above the liquid level of the molten salt solution.

[0008]

1 and 2 show one embodiment of a molten salt electrolysis apparatus according to the present invention. The illustrated molten salt electrolysis apparatus includes an electrolytic cell 1 having a hermetically sealed structure, and a predetermined amount of molten salt 2 is filled in the electrolytic cell 1. The upper portion of the molten salt 2 is filled with argon.
That is, the electrolytic cell 1 is kept airtight in an argon atmosphere.

[0009] A plurality of anode baskets 3 are arranged substantially at the center of the electrolytic cell 1 (see FIG. 2). Each anode basket 3 is configured to be movable in the vertical direction and between the inside and outside of the electrolytic cell 1. After a spent fuel containing uranium as a metal material to be recovered is put into the anode basket 3 outside the electrolytic cell 1, the anode basket 3 is lowered and immersed in the molten salt 2.

On both sides of the anode basket 3, metal cathode drums 4 are arranged. As shown in FIG. 2, the cathode drum 4 has a cylindrical shape and is rotatably supported so that the rotation axis is horizontal. Each cathode drum 4 receives power from a motor 5 and rotates at a low speed. One cathode drum 4 (the cathode drum located on the left side in FIG. 1) rotates counterclockwise, and the other cathode drum 4 (the cathode drum located on the right side in FIG. 1) rotates clockwise.

The rotation axis of each cathode drum 4 is located slightly above the liquid level of the molten salt 2. For this reason, substantially the lower half of each cathode drum 4 is immersed in the molten salt 2. In addition,
In order to keep the voltage used for electrolysis low, the distance between the anode basket 3 and each cathode drum 4 is preferably as small as possible without contact. A metal scraping device is provided for each cathode drum 4. This metal scraping device includes a scraper 6 having substantially the same length as the horizontal length of the cathode drum 4, a tray 7 for receiving the metal scraped by the scraper 6, and a vertically extending scraper 6 and tray 7.
In addition, it comprises an elevating device 8 that moves up and down between the inside and outside of the electrolytic cell 1.

When the metal scraping device is in the upper position A (see FIG. 1), the metal scraping device is located outside and above the electrolytic cell 1, and the metal scraping device is lowered to the lower position. B (see FIG. 1), the scraper 6 contacts the outer peripheral surface of each cathode drum 4 at a position above the liquid level of the molten salt 2 inside the electrolytic cell 1. A heating wire 9 is buried in the bottom of the electrolytic bath 1, and when the heating wire 9 is energized, the electrolytic bath 1 and thus the molten salt 2 inside the electrolytic bath 1 can be heated. .

The present molten salt electrolysis apparatus having the above configuration operates as follows. At the initial stage, the anode basket 3 is positioned above the electrolytic cell 1 and the metal scraping device is positioned at the upper position A. First, the heating wire 9 is energized to heat the molten salt 2 to a temperature suitable for electrolysis. Next, after the spent uranium fuel is put into the anode basket 3, the anode basket 3 is lowered and immersed in the molten salt 2 in the electrolytic cell 1. Next, the motor 5 is operated to rotate each cathode drum 4. Thereafter, the anode basket 3 is energized,
The molten salt 2 is electrolyzed.

By these series of operations, each cathode drum 4
Metal uranium is uniformly deposited on the surface of the substrate. After the metal uranium has been deposited to some extent, the metal scraping device is lowered to the lower position B, and the scraper 6 is brought into contact with the outer peripheral surface of each cathode drum 4. The deposited uranium moves toward the scraper 6 of the metal scraping device with the rotation of the cathode drum 4 and is scraped by the scraper 6. The scraped uranium pieces are collected in a tray 7 located immediately below the scraper 6.

When the tray 7 is full of uranium fragments, the metal scraping device is raised from the lower position B to the upper position A,
The uranium piece is taken out and the metal scraping device is lowered to the lower position B again. Thus, in the molten salt electrolysis apparatus according to the present embodiment, uranium metal can be continuously recovered.

In the embodiment described above, two cathode drums 4 are used, but the number of cathode drums 4 is not limited to two. At least one cathode drum 4 may be provided, and three or more cathode drums 4 may be provided. In addition,
In the above embodiment, the number of the cathode drums 4 is set to two in consideration of the symmetry of the potential and the voltage distribution in the molten salt 2.

One of the features of the molten salt electrolysis apparatus according to the present embodiment is that, unlike the conventional apparatus, the cathode area can be easily increased. The cathode area can be increased by, for example, increasing the horizontal length of each cathode drum 4 or increasing the number of cathode drums 4. If the horizontal length of the cathode drums 4 cannot be increased due to the limitation on the size of the electrolytic cell 1, the diameter of each cathode drum 4 may be increased. Further, in the above-described embodiment, the used uranium fuel is used, but the present molten salt electrolysis apparatus can be used not only for uranium but also for other radioactive metal substances.

[0018]

EXAMPLE An example of an experiment conducted using the molten salt electrolysis apparatus according to the present embodiment shown in FIGS. 1 and 2 will be described below. The cathode drum 4 has a diameter of 20 cm and a length of 20 cm, and the anode basket 3 has a width of 2 cm, a length of 6 cm and a height of 10 cm. 4 and anode basket 3
Was placed.

As a simulated fuel pin, U-3 wt% Fe
1.5 pellets of alloy (about 1 cm in diameter x 1 cm in thickness)
kg used. As the electrolytic bath, a KCl-LiCl eutectic salt (uranium concentration: 4% by weight) was used, and the inside of the molten salt electrolyzer was kept in an argon atmosphere. The electrolyzer 1 was heated to 500 ° C. with the heating wire 9 and preparation for the experiment was started after about 30 minutes. First, the anode basket 3 was immersed in the molten salt 2 and rotated at a speed of 20 rpm. Next, each cathode drum 4 was rotated at 0.5 rpm.

The liquid level of the molten salt 2 was adjusted by adding the molten salt 2 so that the liquid level of the molten salt 2 was located about 1 cm below the rotation axis of each cathode drum 4. Also,
Two sets of DC power supplies were prepared and wired so that current could be independently controlled for each cathode drum 4. After the above preparations, electrolysis was started. 1 for each cathode drum 4
A constant current of 00 amps (cathode current density: 0.16
(Ampere / cm ² , potential fluctuation range: 1.5 to 2.0 volts) and electrolysis. The metal scraping device was lowered to the lower position B once every 30 minutes, the scraper 6 was brought into contact with the outer peripheral surface of each cathode drum 4, and the deposited metal uranium was scraped and collected in the tray 7.

After about 2 hours, the electrolysis was stopped (total electricity: 400 AHr), and the anode basket 3 and the tray 7 were pulled up to above the electrolytic cell 1. Thereafter, the heating of the electrolytic cell 1 by the heating wire 9 was stopped, and the electrolytic cell 1 was cooled. next day,
After confirming that the electrolytic cell 1 is cooled to room temperature,
The upper lid of the molten salt electrolysis apparatus was opened, and the tray 7 was recovered. Take out the massive mixture of metal uranium and salt from saucer 7,
The weight was measured. The weight was 1,240 grams.

The mass mixture was immersed in cold water to dissolve the salt, and the weight was measured again. As a result, the weight of the metal uranium was 1,110 g. Therefore, the weight of the salt contained was 130 grams, which proved to be relatively small. From the above measurement results, the obtained current efficiency was as high as 94%. By this method, it was confirmed that solid uranium metal can be recovered with high current efficiency even though the operation is simple. Further, the obtained metal uranium fragments had a small content of salt, and it was expected that the burden on the separation step as a post-process performed after the electrolytic purification would be reduced.

[0023]

As described above, according to the present invention, it is possible to simplify the operation of recovering uranium metal and other metal materials to be recovered, and increase the cathode area by enlarging or increasing the number of cathode drums. Thus, it is possible to improve the deposition rate of the metal substance to be recovered. In particular, in the molten salt electrolysis apparatus according to the present invention, since a continuous electrolysis operation is possible, the deposition rate can be further increased.

Furthermore, according to the present invention, unlike the conventional electrolysis apparatus, the metal material to be recovered such as metallic uranium is recovered in a gas, unlike the recovery of the metal material in a liquid. For example, the collection operation can be visually confirmed through a viewing window, and the reliability of the process control can be improved.
In addition, since the amount of salt contained in the metal pieces recovered by the molten salt electrolysis apparatus is extremely small, the separation step after electrolytic purification can be simplified.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of a molten salt electrolysis apparatus according to the present invention.

FIG. 2 is a plan view of the molten salt electrolysis device shown in FIG. 1 as viewed from above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrolyzer 2 Molten salt 3 Anode basket 4 Cathode drum 5 Motor 6 Scraper 7 Receiving tray 8 Lifting device 9 Heating wire

Continued on the front page (72) Inventor Yoshio Kijima 2-12-23 Imagawa, Suginami-ku, Tokyo (72) Inventor Tatsuya Futami 311-1-105, Soyodo-cho, Kohoku-ku, Yokohama, Kanagawa, Japan 105 (72) Inventor Keiji Toritanibe Ibaraki 547-12 Funashikawa, Tokai-mura, Naka-gun (72) Inventor Kuniaki Kobayashi 1-16-23-703, Zenpukuji, Suginami-ku, Tokyo (72) Inventor Junichi Takahashi 1220-14, Muramatsu, Tokai-mura, Naka-gun, Ibaraki Prefecture (72) Inventor Takafumi Shimizu 1-1-7-1105 Minamimachi, Mito City, Ibaraki Prefecture

Claims (2)

[Claims] 1. An electrolytic cell containing a molten salt solution in which a metal substance to be recovered is dissolved; and an electrolytic cell disposed in the electrolytic cell so that at least a part of its surface is immersed in the molten salt solution; At least one cathode drum having a rotating shaft, an anode immersed in the molten salt solution, and a metal substance to be recovered deposited on the surface of the cathode drum scraped above the liquid surface of the molten salt solution. An apparatus for recovering a metal substance to be recovered in a molten salt electrolysis apparatus, comprising: a scraping device for removing. 2. In a sealed electrolytic cell containing a molten salt solution in which a metal substance to be recovered is dissolved, at least a part of the surface is immersed in the molten salt solution, and the rotating shaft is The cathode drum is rotated so as to be horizontal, and the molten salt solution is electrolyzed by applying an electric current to the anode immersed in the molten salt solution, and the metal material to be recovered deposited on the surface of the cathode drum is removed. A method for recovering a metal material to be recovered in a molten salt electrolysis apparatus, wherein the metal salt is scraped above the liquid level of the molten salt solution.