CONTINUOUS ELECTROREFINING DEVICE FOR RECOVERING METAL URANIUM

Abstract

Disclosed is a continuous electrorefining device for recovering metal uranium. The electrorefining device comprises an electrolytic cell 10 having an internal accommodating space filled with electrolyte; a cathode unit 20 including a top plate 22, connecting rods 21 whose top ends are joined to the top plate 22, and cathode electrodes 24 whose top end is joined to lower plates; an anode unit 40 which is placed in a cylinder shape surrounding the cathode electrodes 24; a uranium recovery unit 50 for drawing out the uranium metal by a first drawing-out means; and a transition metal recovery unit 60 for drawing out the metal particles by a second drawing-out means. The cathode unit 20 further comprises an insulating and vibration absorbing member that is interposed between the top plate 22 and the cover plate 12; and a vibration means which is mounted on the top plate 22 to transmit vibration and impact force to the cathode electrode 24 through the connecting rods 21.

Description

This application claims priority to Korean Patent Application No. 10-2008-0098849, filed on Oct. 8, 2008, in the Korean Intellectual Property Office, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a continuous electrorefining device for recovering metal uranium, and more specifically to a continuous electrorefining device for recovering metal uranium which can continuously recover metal uranium by scraping uranium electrodeposits deposited at a cathode by applying vibration or impact force to the cathode using vibrating means.

2. Description of the Related Art

As well-known to the public, a conventional electrorefining device comprises an anode basket that contains segments of spent metal fuel in a melted salt containing molten uranium chloride at about 500° C. and an iron-based cathode at which pure uranium is to be deposited

During the refining process of the metal uranium using the conventional electrorefining device for recovering metal uranium, when applying the current to the device, the uranium ion in the uranium chloride in the molten salt is reduced to uranium, which is deposited at the cathode, and the chlorine ion scraped by the reaction selectively dissolves the metal uranium at the anode. Thus, pure uranium can be obtained at the cathode, while consequently enabling the separation of uranium from the composite metal by repeating the electrorefining processes of metal uranium.

However, the electrorefining process of metal uranium using the conventional electrorefining device for recovering metal uranium has drawbacks that an electrolytic reaction must be stopped to periodically collect metal uranium deposited on the cathode, as well as needs a long recovery time to collect electrodeposits, thereby it is impossible to do a continuous operation. Therefore a large quantity of products cannot be obtained in a predetermined time.

To overcome the above drawbacks, other electrorefining devices for scraping pure metal uranium at a high speed have been disclosed in the art.

For example, U.S. Pat. No. 5,650,053 (Jul. 22, 1997) discloses an electrorefining device comprising a combination of anodes and cathodes, wherein segments of spent metal fuel in a molten salt at about 500° C. are put in a plurality of inner anode baskets and outer anode baskets of a porous plate, and the plurality of inner and outer anode baskets are placed between an inner cylindrical cathode and an outer cylindrical cathode. According to the above patent, when applying the current to the device with rotating the anode baskets, molten metal uranium from the anode baskets is deposited onto the cathodes and the deposited metal uranium is scrapped by ceramic plates which are attached on the outside of the anodes, then the scrapped metal uranium is collected in a reservoir arranged at the lower portion of the device.

However, the electrorefining device disclosed in the above patent has problems that only a part of the metal uranium deposited on the cathodes is detached, and the remnant electrodeposits keep sticking on the surface of the cathodes, thereby the remnant electrodeposits are gradually changed into a dense tissue which is difficult to detach.

Accordingly, since it is impossible to detach electrodeposits whose tissue becomes dense with the ceramic plates provided at the anodes, the electrorefining operation is stopped after a predetermined time has passed and then electricity is inversely applied to return the electrodeposits to the anodes to be stripped. The surface of the cathodes becomes clean and the deposition is operated again from the beginning.

The above stripping process has drawbacks that a lot of electricity is consumed, the deposition efficiency is deteriorated and that the structure of the device becomes complicated. Furthermore, the device has a problem that the electrolysis must be stopped in order to collect electrodeposits in the lower part and that the entire electrode module should be lifted.

In addition, the reservoir for collecting uranium electrodeposits is disposed at the lower section of the anode baskets to mix the undissolved transition atom particles generated from the anodes with uranium, thus there is a limitation in obtaining high purity uranium electrodeposits.

Japanese Patent Laid-Open No. H10-332880 (Dec. 18, 1998) discloses an electrorefining device, wherein metal nuclear fuel components are dissolved in cadmium at 500° C. and are deposited on an iron-based cathode again, and uranium electrodeposits are collected through a mechanical scrapping process. The collected uranium electrodeposits are transferred to an individual uranium/salt separator and treated therein to separate the salt from the electrodeposits.

Therefore, the electrorefining device disclosed in the above patent can do a continuous operation without stopping the electrolysis reaction in order to collect uranium electrodeposits, thus increasing the processing speed.

However, since the electrorefining device disclosed in the above patent also uses an iron-based cathode, it has a disadvantage accompanied with a mechanical scrapping process.

Moreover, it has drawbacks that since a pump is employed to transfer electrodeposits, a quantity of salts and cadmium are simultaneously transferred, thereby an additional distillation process for collecting uranium electrodeposits should be passed.

In addition, Japanese Patent Laid-Open No. H10-53889 discloses an electrorefining device, wherein a drum-type cathode whose a part is deposited in a molten salt in order to easily collect uranium deposited on the cathode is rotated to separate uranium electrodeposits by a scraper and argon gas is sprayed to the uranium surface deposited on the surface of the cathode drum to remove the remnant salt.

However, the electrorefining device disclosed in the above patent also needs continuous supplying of argon and needs a mechanical scrapping process. The problems of the conventional devices are not fundamentally solved.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a continuous electrorefining device for recovering metal uranium which can continuously recover metal uranium by scraping uranium electrodeposits deposited at a cathode by applying vibration or impact force to the cathode using vibrating means.

In order to accomplish the above object, there is provided a continuous electrorefining device for recovering metal uranium comprising: an electrolytic cell including an internal housing space which is filled with electrolyte; a cathode unit in which cathode electrodes are fixed below the radiation fin in said electrolytic cell by connecting rods that pass through the central portion of a cover plate covering said electrolytic cell; an anode unit including an internal housing space for housing spent nuclear fuel therein, wherein the anode unit is made in a cylinder shape so as to surround and face said cathode electrodes, and is rotatably installed on the edge of said cover plate; an uranium recovery unit for drawing out of the electrolytic cell the metal uranium scraped and collected from said cathode electrode by a first drawing-out means connected to the bottom of the uranium recovery cell provided below said cathode electrode; and a transition metal recovery unit form drawing out the transition metal particles collected in the lower portion of said electrolytic cell by a second drawing-out means connected to the bottom of said electrolytic cell, wherein said cathode unit further comprises an insulating and vibration absorbing member for scraping and fixing the top plate fixed at the top end of said connecting rods on said cover plate in such a way that insulation and vibration absorbing are possible; and a vibration means which is provided on said top plate to transmit exciting force to said cathode electrode through said connecting rods.

In accordance with one embodiment of the present invention, said insulating and vibration absorbing member may be a vibration absorbing rubber plate.

In accordance with another embodiment of the present invention, said insulating and vibration absorbing member may consist of ceramic plates that are respectively in contact with said cover plate isolated at a predetermined interval and said top plate; and a coil spring interposed between said ceramic plates.

Preferably, said vibration means is an electric hammer.

Preferably, said cathode electrode is made of graphite material or an iron-based cathode including stainless steel material.

The continuous electrorefining device for recovering metal uranium may further comprise a screw-type agitator which passes through the cover plate and is fixed rotatably on the center of said cathode electrodes.

Preferably, said first drawing-out means and said second drawing-out means are screw conveyor, respectively.

According to the continuous electrorefining device for recovering metal uranium of the present invention, it is possible to recover electrodeposits continuously by scraping uranium electrodeposits deposited at a cathode by applying vibration or impact force to the cathode using vibrating means.

And, according to the continuous electrorefining device for recovering metal uranium of the present invention, it is possible to recover metal uranium continuously and uniformly without mechanical scraping from an iron-based cathode including stainless steel, besides a graphite electrode where uranium electrodeposits are self-scraped.

Also, according to the continuous electrorefining device for recovering metal uranium of the present invention, it is possible to recover uranium electrodeposits uniformly by adjusting the scraping point of time and cycle of uranium electrodeposits using a vibrating means.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features, aspects, and advantages of the present invention will be more fully described in the following detailed description of preferred embodiments and examples, taken in conjunction with the accompanying drawings. In the drawings:

FIG. 1 is a longitudinal sectional view showing a continuous electrorefining device for recovering metal uranium according to a first embodiment of the present invention;

FIG. 2 is an enlarged sectional view showing the part II of FIG. 1;

FIG. 3 is a perspective view showing the partially scraped state of the cathode unit of FIG. 2;

FIG. 4 is a partial sectional view showing the shape of the outlet of the cylindrical basket of FIG. 3;

FIG. 5 is an enlarged sectional view corresponding to the part II of FIG. 1 for showing a continuous electrorefining device for recovering metal uranium according to a second embodiment of the present invention; and

FIG. 6 is photographs showing the shape of uranium electrodeposits using graphite cathode and the graphite cathode after vibration scraping.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention should not be construed as limited to the embodiments set forth herein. Rather, it is intended that the present invention covers all modifications and variations within the scope of the appended claims. To make the present invention clear, the portions not related to the present invention are omitted from the drawings for simplicity, and the same or similar components are shown and described with the same reference numerals throughout the drawings and detailed description.

FIG. 1 is a longitudinal sectional view showing a continuous electrorefining device for recovering metal uranium according to a first embodiment of the present invention.

Referring to FIG. 1, the continuous electrorefining device 1 for recovering metal uranium according to the first embodiment of the present invention comprises an electrolytic cell 10, cathode unit 20, screw agitator 30, anode unit 40, uranium recovery unit 50, and transition metal recovery unit 60.

The electrolytic cell 10 consists of an opened upper portion which has a cylinder shape and provides an internal accommodating space, and a bottom portion which has a funnel shape. The internal accommodating space provided inside of the electrolytic cell 10 is filled with electrolyte so that the cathode of the cathode unit 20 and the anode basket of the anode unit 40 are immersed.

On the top of the electrolytic cell 10 is provided a cover plate 10 to cover the opened upper portion, and under this cover plate 12 are placed the cathode unit 20, screw agitator 30 and anode unit 40.

In the upper portion inside the electrolytic cell 10 are installed a plurality of heat radiation fins 15 in parallel to each other.

The cathode unit 20 includes connecting rods 21, a top plate 22, lower plates 23, cathode electrodes 24, insulating and vibration absorbing members 25 and vibrating means 26.

FIG. 2 is an enlarged sectional view showing the part II of FIG. 1.

Referring to FIG. 2, on the top of the cover plate 12 is placed the top plate 22 at a predetermined interval, and on opposite sides of the top plate 22 are joined top ends of the connecting rods 21. At the lower ends of the connecting rods 21 are joined cathode electrodes 24 through the lower plates 23. And between the top plate 22 and the cover plate are interposed the insulating and vibration absorbing members 25 and on the top side of the top plate 22 are mounted the vibrating means 26.

On the cover plate 12 are formed a plurality of though holes 12a at equal intervals circumferentially from the central portion, so that the connecting rods 21 are penetrated the through holes 12a and, then fixed on the edge of the top plate 22. Thus, the top end of the connecting rod that has passed through the through holes 12a of the cover plate 12 is fixed on the edge of the top plate 22.

The top plate 22 is made in a hollow disk shape and is placed on the top of the cover plate 12 through the insulating and vibration absorbing members 25 in a state scraped at a predetermined interval.

The lower plate 23 is made in a hollow disk shape in the same fashion as the aforementioned top plate 22, and after it passes through the heat radiation fins 15 installed in the upper portion inside the electrolytic cell 10, it is fixed on the lower ends of the connecting rods 21.

The cathode electrode 24 is made in a bar shape, and the top end is fixed to the lower plate 23 and the lower end is extended downward from the lower plate 23 to be placed in the lower portion inside the electrolytic cell 10. In this embodiment is embodied a structure in which the cathode electrodes 24 are arranged at equal intervals in two rows along the circumference of the lower plates 23 so as to increase the area facing the anode unit 40 that is formed surrounding the cathode electrodes 24.

By the insulating and vibration absorbing members 25 interposed between the top plate 22 and the cover plate 12, the top plate 22 is fixed on the cover plate 12 in a condition in which insulating and vibration absorbing are possible.

In this embodiment, an insulating rubber plate 25a is embodied as an example of the insulating and vibration absorbing member 25. Accordingly, the insulating rubber plates 25a not only electrically insulates the top plate 22 and the cover plate 12 on which the connecting rods 21 of the aforementioned cathode unit 20 are fixed, but also they absorb the vibration and impact generated by the vibrating means 26 so as to prevent them from being transmitted to the cover plate 12.

And the vibrating means 26 mounted on the top side of the top plate 22 plays a role of transmitting vibration and impact to the cathode electrodes 24 through the connecting rods 21.

In this embodiment, an electric hammer 26a is embodied as an example of the vibrating means 26. The vibration and impact force generated from the electric hammer 26a is transmitted to the cathode electrodes 24 through the connecting rods 21 that pass through the cover plate 12 and the heat radiating fins 15. Accordingly, in the process that spent nuclear fuel is electrolytically refined into uranium from molten salt, the uranium electrodeposits deposited on the cathode electrodes 24 are continuously scraped by vibration and impact from the electric hammers 26a and are gathered in the reservoir of the uranium recovery unit 50, and the gathered uranium can be drawn out of the electrolytic cell 10 by a drawing-out means.

As mentioned above, the uranium electrodeposits deposited by the cathode electrodes 24 in this embodiment are continuously scraped by the vibrating means 26, so it is possible to use iron-based cathodes including stainless steel besides a graphite cathode where uranium electrodeposits are self-scraped. Therefore, the continuous electrorefining device provided with the vibrating means of the present invention can electrolytically refine metal uranium continuously in the case of using iron-based cathodes as well as a graphite cathode.

Namely, in the case of using the graphite cathode it is possible to recover electrodeposits continuously and uniformly by the uranium recovery unit 50 without being congested or clogged even if a large quantity of uranium electrodeposits flow in momentarily, because the self-scraping of uranium electrodeposits from the graphite cathode is expedited by vibration and impact transmitted from the electric hammers 26a.

And also in the case of using the iron-based cathode including stainless steel, it is possible to electrolytically refine metal uranium continuously without a mechanical scraping process because uranium electrodeposits are uniformly scraped at a desired point of time by vibration or impact force transmitted from the electric hammers 26a.

The aforementioned screw agitator 30 located in the center of cathode electrodes 24 is rotatably installed to the cover plate 12 after it has passed through the heat radiating fins 15, and its top end is operatively joined to a first motor 32.

Referring to FIG. 1 again, the screw agitator 30 agitates the molten salt inside the electrolytic cell 10 while it is rotated by the first motor 32 installed on the fixed bracket 13 placed above the cover plate 12. At this time, the molten salt is agitated flowing from bottom to top while it is rotated in the center of the cathode electrodes 24 by the screw-shaped agitator 30.

Accordingly, the screw agitator 30 flows upward the molten salts that were circulated and flowed downward of the cathode electrodes 24, so that the metal uranium melted in the molten salt can be deposited on the cathode electrodes 24 more easily.

At this time, it is preferable to configure the screw agitator 30 in interlock with the anode unit 40 to be described later, so as to prevent turbulence from occurring during the agitation of molten salt.

The anode unit 40 consists of anode frames 41 and an anode basket 45.

FIG. 3 is a perspective view showing the partially scraped state of the cathode unit of FIG. 2.

Referring to FIG. 3, the anode unit 40 includes anode frames 41 rotatably fixed to the lower side of the cover plate 12, and anode baskets 45 fixed to the anode frames 41.

As shown in FIG. 1, the top end of the anode frames 41 is operatively connected to the second motor 42 installed on the fixed bracket 13 placed above the cover plate 12, so it rotates around the cathode electrodes 24 according to the operation of the second motor 42.

The anode basket 45 is formed in a cylinder shape so as to be opposite to the cathode electrodes 24 with encompassing the surroundings thereof.

The anode basket 45 includes an outer anode basket 45a and an inner anode basket 45b which are formed with a distance from each other in order to provide a receiving space for receiving the spent nuclear fuel inside thereof.

Moreover, it is preferred that the anode basket 45 be dividedly formed into a plurality of arc-shaped baskets 46 along the circumferential direction of the anode frames 41. The arc-shaped baskets 46 are coupled to the anode frames 41 without additional connecting members in order to easily do an individual replacement operation.

Accordingly, the arc-shaped baskets 46 can individually replace only the arc-shaped baskets 46 where the received nuclear fuel is completely dissolved by electrolytes. Therefore, it is possible to perform a continuous electrorefining process without withdrawing the entire anode unit 40 to the outside of the electrolytic cell 10.

Hereinafter, the anode basket 45 refers to each arc-shaped basket 46 constituting itself. The anode basket 45 is arranged and elongated along the vertical direction of the outer anode basket 45a and the inner anode basket 45b and a plurality of outlets 45c are formed in parallel to the circumferential direction.

FIG. 4 is a partial sectional view showing the shape of the outlet of the cylindrical basket of FIG. 3.

Referring to FIG. 4, the outlets 45c can be formed on both the outer anode basket 45a and the inner anode basket 45b of the anode basket 45, and it is formed so that the molten salt is flown from the inside to the outside of the anode unit 40 when the anode unit 40 is rotated.

Moreover, the outlet 45c is formed slanted to the central line L of the cross-sections of each anode basket 45. In this embodiment, the outlets 45c are formed slantingly at 45° from the central lines L of the anode basket 45, and furthermore, are formed on the slant in the direction where a pathway through which the molten salt is flown and in the direction opposite to the direction of the rotation of the anode unit 40.

Therefore, in the electrolysis reaction process of nuclear fuel, transition metal sludge less than the predetermined sizes, which is not dissolved by electrolytes to remain in the anode basket 45 is discharged through the outlets 45c of the outer anode basket 45a by the flow of the molten salt.

In addition, the inner anode basket 45b of the anode basket 45 may be formed of a mesh less than a preset mesh in order to prevent transition metal sludge from being flown into the anode unit 40.

For example, it is preferable that the inner anode basket 45b be formed of a stainless mesh of approximately 100 to 325 meshes.

Accordingly, the molten salt inside the electrolytic cell 10 is agitated, flowing without occurrence of turbulence, by the anode unit 40 and the screw agitator 30 that rotates in interlock with it.

The anode unit 40 rotates to flow the molten salt inside the cathode unit 20 to outside, so that the nuclear fuel contained in the anode basket 45 is melted more easily. And the transition metal sludge that is not melted and remaining is discharged out through a plurality of outlets 45c formed in the anode basket 45.

At this time, the discharged transition metal sludge is collected in the lower portion of the electrolytic cell 40 by a specific gravity difference with molten salt.

Referring to FIG. 1 again, the metal uranium recovery unit 50 consists of a uranium reservoir 51 placed below the cathode electrodes 24 and a first drawing-out means 52 which is placed below the reservoir 51 to draw the collected metal uranium out of the electrolytic cell 10.

The reservoir 51 made in a funnel shape along the lower shape of the electrolytic cell 10 is placed below the cathode unit 20, and in the reservoir 51 is collected metal uranium electrodeposits that are scraped after being deposited on the cathode electrode 24.

Meanwhile, in this embodiment a first screw conveyor 52a is embodied as an example of a first drawing-out means 52. This first screw conveyor 52a is constructed in such a way that the metal uranium collected in the lower portion of the reservoir 51 can be drawn continuously out of the electrolytic cell 10.

And the transition metal recovery unit 60 consists of a second drawing-out means 62 connected to the lower portion of the electrolytic cell 10. In this embodiment a second screw conveyor 62a is embodied as an example of the second drawing-out means 62. Thus, the transition metal sludge collected in the lower portion of the electrolytic cell 10 is continuously drawn out of the electrolytic cell 10 by the second screw conveyor 62a.

Meanwhile, the second screw conveyor 62a can be utilized as a conveying means for exchanging molten salts, besides using it for recovering the transition metal sludge.

Thus, in the continuous electrorefining device for recovering metal uranium, the metal uranium which is scraped from the cathode electrodes 24 by applying vibration or impact force to the graphite or cathode using the electric hammers 26a, then collected in the reservoir 51 can be drawn continuously out by the first screw conveyor 52a, and the transition metal sludge collected in the lower portion of the electrolytic cell 10 is continuously drawn out by the second screw conveyor 62a.

Next, a continuous electrorefining device for recovering metal uranium according to a second embodiment of the present invention will be described with reference to the accompanying drawings. The parts that have a same or similar configuration to the aforementioned first embodiments of the present invention will be applied to the same reference numerals, and the description thereof will be omitted.

FIG. 5 is an enlarged sectional view corresponding to the part II of FIG. 1 for showing a continuous electrorefining device for recovering metal uranium according to a second embodiment of the present invention.

Referring to FIG. 5, the continuous electrorefining device 1 for recovering metal uranium of this embodiment has a configuration generally similar to the aforementioned first embodiment, except for ceramic plates 25b mounted on the cover plate 12, and insulating and vibration absorbing members 25 made of a coil spring 25c.

Here, the ceramic plates 25b are installed so as to be in contact with the top side of the cover plate 12 and the bottom side of the top plate 22 respectively to electrically insulate the top plate 22 from the cover plate 12. The top ends of the connecting rod 21 that have passed through the cover plate 12 are joined to the top plate 22, and to the lower ends of the connecting rods 21 are fixed cathode electrodes 24 by the lower plates 23.

The coil springs 25c interposed between ceramic plates 25b absorb the vibration and impact force generated by the electric hammers 26a to prevent them from being transmitted to the cover plate 12. At this time, the vibration generated from the electric hammers 26a is transmitted to the cathode electrodes 24 through the connecting rods 21.

Below will be described examples in which the iron-based cathode is replaced with a graphite cathode in the continuous electrorefining device 1 for recovering metal uranium according to the first embodiment of the present invention to compare the vibration scraping characteristics of uranium electrodeposits.

Example 1

In Example 1, an iron-based cathode was used to perform experiments on the vibration scraping characteristics of uranium electrodeposits.

In this example, a cathode made of stainless steel of iron-based cathodes was used, and the stainless steel cathode was used to observe the scraping behavior of uranium electrodeposits according to the vibration stroke of the electric hammer 24 and the results were shown in Table 1.

Under the general electrorefining conditions of LiCl—KCl molten salt with UC13 of 9% by weight at temperature of 500° C., the sticking coefficient according to the change of current density and vibration stroke were measured. Here, the sticking coefficient can be defined as follows.

$\mathrm{Sticking}\mathrm{coefficient}=\frac{\mathrm{Quantity}\mathrm{of}\mathrm{electrodeposits}\mathrm{remaining}\mathrm{on}\mathrm{cathode}\mathrm{surface}\left(g\right)}{\mathrm{Theoretical}\mathrm{quantity}\mathrm{of}\mathrm{electrodeposits}\left(g\right)}$

Thus, if the sticking coefficient is great, it means the uranium electrodeposits are not scraped and remaining on the cathode surface; if it is near to zero (0), it shows that most of the electrodeposits were scraped.

TABLE 1
Current
density of	Vibration
applied	stroke,	Sticking coefficient
current	720C	One time	Two times	Three times
(A/m2)	stroke/min)	use	use	use
4.5	0.5	0.005	0.005	0.061
4.5	2	0.021	0.035	0.001
4.5	0.5	0.175	0.48	0.075
7	2	0.02	0.01	0
9	0.2	0.089	0	0.029
9	2	0.084	0	0

As can be confirmed by Table 1, we can see that uranium electrodeposits are scraped by vibration under most conditions regardless of current density. And since it is defined that self-scraping predominantly occurs in the graphite cathode if the sticking coefficient is 0.05 or less, we can see that scraping behavior on the level of graphite cathode is shown by applying vibration in most conditions.

Especially the results of experiments on six kinds of current density showed that the average sticking coefficient of the stainless steel cathode used three times in repetition was 0.028, from which we can see that it showed self-scraping characteristics continuously.

This means that a clean cathode surface is maintained by applying vibration even during long-time operation and uranium electrodeposits can be recovered, because the sticking coefficient is not greatly affected under most of the conditions even if the cathode is used three times repeatedly without an extra cleaning process.

Example 2

In Example 2, we experimented on the vibration scraping characteristics of uranium electrodeposits using a graphite cathode.

FIG. 6 is photographs showing the shape of uranium electrodeposits using a graphite cathode and the graphite cathode after vibration scraping.

FIG. 6 (a) shows the shape of uranium electrodeposits before self-scraping during electrorefining of uranium using a graphite cathode module under the electrorefining conditions of Table 2 below.

	TABLE 2
		Initial	Uranium
	Total salt	concentration	loadings in	Applied
	weight	of UCl3	anode baskets	current
	50 kg	4.8% by weight	17.3 kg	200 A · hr

For self-scraping to occur during uranium electrodeposition by graphite cathode, more than a certain quantity of uranium should be deposited to make the load of electrodeposits greater than the bond strength of electrodeposits on the graphite cathode surface. But if electrodeposits are scraped all at once in this way, electrodeposits are congested at the entrance of the first screw conveyor 52a to hamper the rotary motion of the screw, so work may not be done smoothly.

Therefore, if a certain quantity of uranium is deposited at the graphite cathode, it should be scraped by force, so that a controlled quantity of uranium electrodeposits can be brought to the entrance of the first screw conveyor 52a.

As shown in FIG. 6 (b), before self-scraping occurs, it could be observed the phenomenon that electrodeposits are bonded on the electrode surface. If this is reloaded in the electrolytic cell 10 and vibration is applied by the top vibrator, it could be seen that all the electrodeposits are scraped by vibration even before self-scraping as shown in FIG. 6 (b).

While the present invention has been described with reference to preferred embodiments, it will be understood by those skilled in the art that various modifications and variations may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A continuous electrorefining device for recovering metal uranium comprising:

an electrolytic cell including an internal housing space which is filled with electrolyte;

a cathode unit in which cathode electrodes are fixed below the radiation fin in said electrolytic cell by connecting rods that pass through the central portion of a cover plate covering said electrolytic cell;

an anode unit including an internal housing space for housing spent nuclear fuel therein, wherein the anode unit is made in a cylinder shape so as to surround and face said cathode electrodes, and is rotatably installed on the edge of said cover plate;

an uranium recovery unit for drawing out of the electrolytic cell the uranium metal scraped and collected from said cathode electrode by a first drawing-out means connected to the bottom of the uranium recovery cell provided below said cathode electrode; and

a transition metal recovery unit form drawing out the transition metal particles collected in the lower portion of said electrolytic cell by a second drawing-out means connected to the bottom of said electrolytic cell,

wherein said cathode unit further comprises an insulating and vibration absorbing member for scraping and fixing the top plate fixed at the top end of said connecting rods on said cover plate in such a way that insulation and vibration absorbing are possible; and

a vibration means which is provided on said top plate to transmit exciting force to said cathode electrode through said connecting rods.

2. The device according to claim 1, wherein said insulating and vibration absorbing member is a vibration absorbing rubber plate.

3. The device according to claim 1, wherein said insulating and vibration absorbing member consists of ceramic plates that are respectively in contact with said cover plate isolated at a predetermined interval and said top plate; and

a coil spring interposed between said ceramic plates.

4. The device according to claim 1, wherein said vibration means is an electric hammer.

5. The device according to claim 1, wherein said cathode electrode is made of graphite material.

6. The device according to claim 1, wherein said cathode electrode is an iron-based cathode including stainless steel material.

7. The device according to claim 1, further comprising a screw-type agitator which passes through said cover plate and is fixed rotatably on the center of said cathode electrodes.

8. The device according to claim 1, wherein said first drawing-out means and said second drawing-out means are a first screw conveyor and a second screw conveyor, respectively.