U.S. patent application number 12/574709 was filed with the patent office on 2010-04-08 for continuous electrorefining device for recovering metal uranium.
This patent application is currently assigned to Korea Atomic Energy Research Institute. Invention is credited to SUNG-CHAN HWANG, YOUNG-HO KANG, EUNG-HO KIM, HAN-SOO LEE, JONG-HYEON LEE, JOON-BO SHIM.
Application Number | 20100084265 12/574709 |
Document ID | / |
Family ID | 42074926 |
Filed Date | 2010-04-08 |
United States Patent
Application |
20100084265 |
Kind Code |
A1 |
LEE; JONG-HYEON ; et
al. |
April 8, 2010 |
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.
Inventors: |
LEE; JONG-HYEON; (Daejeon,
KR) ; KANG; YOUNG-HO; (Daejeon, KR) ; HWANG;
SUNG-CHAN; (Daejeon, KR) ; LEE; HAN-SOO;
(Daejeon, KR) ; SHIM; JOON-BO; (Daejeon, KR)
; KIM; EUNG-HO; (Daejeon, KR) |
Correspondence
Address: |
WPAT, PC
2030 Main Street, Suite 1300
Irvine
CA
92614
US
|
Assignee: |
Korea Atomic Energy Research
Institute
Daejeon
KR
Korea Hydro & Nuclear Power Co., Ltd.
Seoul
KR
|
Family ID: |
42074926 |
Appl. No.: |
12/574709 |
Filed: |
October 7, 2009 |
Current U.S.
Class: |
204/273 |
Current CPC
Class: |
C25C 7/08 20130101; C25C
3/34 20130101; C25C 5/04 20130101 |
Class at
Publication: |
204/273 |
International
Class: |
C25C 7/08 20060101
C25C007/08 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 8, 2008 |
KR |
10-2008-0098849 |
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.
Description
[0001] 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
[0002] 1. Field of the Invention
[0003] 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.
[0004] 2. Description of the Related Art
[0005] 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.degree. C. and an iron-based cathode at which pure
uranium is to be deposited
[0006] 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.
[0007] 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.
[0008] To overcome the above drawbacks, other electrorefining
devices for scraping pure metal uranium at a high speed have been
disclosed in the art.
[0009] 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.degree. 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.degree. 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.
[0015] 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.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] 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
[0020] 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.
[0021] 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.
[0022] In accordance with one embodiment of the present invention,
said insulating and vibration absorbing member may be a vibration
absorbing rubber plate.
[0023] 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.
[0024] Preferably, said vibration means is an electric hammer.
[0025] Preferably, said cathode electrode is made of graphite
material or an iron-based cathode including stainless steel
material.
[0026] 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.
[0027] Preferably, said first drawing-out means and said second
drawing-out means are screw conveyor, respectively.
[0028] 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.
[0029] 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.
[0030] 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
[0031] 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:
[0032] 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;
[0033] FIG. 2 is an enlarged sectional view showing the part II of
FIG. 1;
[0034] FIG. 3 is a perspective view showing the partially scraped
state of the cathode unit of FIG. 2;
[0035] FIG. 4 is a partial sectional view showing the shape of the
outlet of the cylindrical basket of FIG. 3;
[0036] 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
[0037] 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
[0038] 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.
[0039] 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.
[0040] 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.
[0041] 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.
[0042] 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.
[0043] In the upper portion inside the electrolytic cell 10 are
installed a plurality of heat radiation fins 15 in parallel to each
other.
[0044] 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.
[0045] FIG. 2 is an enlarged sectional view showing the part II of
FIG. 1.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] 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.
[0052] 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.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] 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.
[0057] 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.
[0058] 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.
[0059] 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.
[0060] 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.
[0061] 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.
[0062] The anode unit 40 consists of anode frames 41 and an anode
basket 45.
[0063] FIG. 3 is a perspective view showing the partially scraped
state of the cathode unit of FIG. 2.
[0064] 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.
[0065] 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.
[0066] 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.
[0067] 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.
[0068] 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.
[0069] 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.
[0070] 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.
[0071] FIG. 4 is a partial sectional view showing the shape of the
outlet of the cylindrical basket of FIG. 3.
[0072] 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.
[0073] 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.degree.
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.
[0074] 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.
[0075] 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.
[0076] For example, it is preferable that the inner anode basket
45b be formed of a stainless mesh of approximately 100 to 325
meshes.
[0077] 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.
[0078] 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.
[0079] 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.
[0080] 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.
[0081] 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.
[0082] 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.
[0083] 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.
[0084] 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.
[0085] 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.
[0086] 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.
[0087] 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.
[0088] 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.
[0089] 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.
[0090] 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.
[0091] 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
[0092] In Example 1, an iron-based cathode was used to perform
experiments on the vibration scraping characteristics of uranium
electrodeposits.
[0093] 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.
[0094] Under the general electrorefining conditions of LiCl--KCl
molten salt with UC13 of 9% by weight at temperature of 500.degree.
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.
Sticking coefficient = Quantity of electrodeposits remaining on
cathode surface ( g ) Theoretical quantity of electrodeposits ( g )
##EQU00001##
[0095] 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-US-00001 TABLE 1 Current density of Vibration applied stroke,
Sticking coefficient current 720C One time Two times Three times
(A/m.sup.2) 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
[0096] 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.
[0097] 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.
[0098] 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
[0099] In Example 2, we experimented on the vibration scraping
characteristics of uranium electrodeposits using a graphite
cathode.
[0100] FIG. 6 is photographs showing the shape of uranium
electrodeposits using a graphite cathode and the graphite cathode
after vibration scraping.
[0101] 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-US-00002 TABLE 2 Initial Uranium Total salt concentration
loadings in Applied weight of UCl.sub.3 anode baskets current 50 kg
4.8% by weight 17.3 kg 200 A hr
[0102] 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.
[0103] 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.
[0104] 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).
[0105] 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.
* * * * *