JP2013170290A - Molten salt electrolysis apparatus and molten salt electrolysis method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that heating for a long time is necessary to evaporate and remove a salt, in a salt removing process in a spent fuel reprocessing step.SOLUTION: A molten salt electrolysis apparatus 20 includes: a crucible 14 for accommodating a molten salt 2; a heating means 5 for heating the crucible; an electrode device 10 which is accommodated in the crucible and has an anode 3 and a cathode 4; a power circuit 11 for electrolysis, for supplying a power source between the both electrodes of the electrode device; an electrode driving device for ascendably/descendably and rotatably driving a movable electrode of the electrode device; and a recovery device 21 for recovering electrolytic deposits deposited on a cathode side by the supply of the power source to the both electrodes. The recovery device is connected to a rotating mechanism 23 or a swinging mechanism, and the separation of a recovery metal 24 and the molten salt 2 is carried out by a force by rotation or swing of the rotating mechanism or the swinging mechanism.

Description

  The present invention relates to a dry reprocessing technique for reprocessing spent fuel, and more particularly to a molten salt electrolysis apparatus and a molten salt electrolysis method for collecting active components from spent fuel by electrolysis and collecting them on an electrode.

  As a reprocessing device using the molten salt electrolysis method of spent fuel generated from nuclear power plants, the fission product (FP) contained in the spent fuel is removed by applying a potential using the spent fuel as an anode, Technology that deposits the metal required for fuel production on the cathode, scrapes it off using mechanical means, collects it in a recovery container, removes the salt in the subsequent salt removal process, and forms and manufactures it as metal fuel Is established.

  FIG. 6 is a longitudinal sectional view schematically showing a conventional molten salt electrolysis apparatus for processing spent fuel.

  In FIG. 6, the molten salt electrolysis apparatus 1 has a crucible 14 made of metal, a molten salt 2 is accommodated in the crucible 14, and an anode basket 3 as an anode and a movable electrode as a cathode in the molten salt 2. 4 is immersed. The molten salt 2 is formed of an alkali metal chloride such as sodium chloride or potassium chloride. A heater 5 is provided on the outer peripheral side of the crucible 14 as a heating means. The heater 5 may be provided on the outer peripheral side of the crucible 14 via a protective container. The heater 5 heats the crucible 14 to a high temperature of, for example, 500 ° C to 700 ° C.

  The top of the crucible 14 is covered with the upper lid 6 and the inside of the crucible 14 is closed. The upper lid 6 is provided with an anode basket 3 via a cylindrical or sleeve-like heat insulating member 7. The heat insulating member 7 has a cylindrical shape or a bar shape and functions as a support member of the anode basket 3.

  The anode basket 3 is formed by assembling a mesh member or an opening member such as a wire mesh or punching metal into a cylindrical, sleeve-like or torus-like basket shape. Yes. A movable electrode 4 having a reverse truncated cone shape is provided inside the anode basket 3 as the other electrode (cathode). The electrode device 10 is constituted by both the electrodes 3 and 4.

  The anode basket 3 is a torus-shaped, annular, or cylindrical fixed electrode provided along the circumferential direction in the crucible 14, and the spent cutting fuel 8 with a cladding tube is accommodated inside the basket. The other electrode 4 constitutes a movable electrode that can be arranged concentrically inside the fixed electrode 3.

  A voltage is applied to both electrodes 3 and 4 via an electrolysis power supply circuit by an electrolysis power supply 11, and one fixed electrode 3 is configured as an anode and the other movable electrode 4 is configured as a cathode and functions.

  Further, a support member 13 extends downward from the bottom of the anode basket 3 provided in the crucible 14, and a deposit collection container 12 is provided at the tip of the support member 13. The support member 13 may be a sleeve-shaped or cylindrical member, or may be a member in which a plurality of rod-shaped members are arranged in the circumferential direction. The support member 11 is provided with a cutter 9 for scraping off precipitates.

  Then, the electrodes 3 and 4 are electrolyzed, the metal is deposited on the movable electrode 4 serving as the cathode, the metal deposited on the scraping cutter 9 is scraped off, and is received by the collection container 12 installed under the cathode. ,to recover. The recovery container containing the recovered metal has an elevating mechanism, and after completion of electrolysis, the metal is recovered by pulling up from the molten salt 2. The spent fuel 8 is dissolved by electrolysis to deposit metals U, Pu, minor actinides and the like, and the deposited metals are collected.

JP 2006-314958 A

  In the molten salt electrolysis apparatus for processing the spent fuel described above, when the recovery container containing scraped metal that has been scraped and recovered is pulled from the molten salt, the molten salt flows into the recovery container. In addition, an unnecessary large amount of salt adhering to the metal is also recovered at the same time. For this reason, in the salt removal process in the used reprocessing step, heating for a long time is required for evaporating and removing the salt, and the amount of recovered metal contained in the processing unit is reduced, resulting in processing time, cost, and efficiency. There is a problem.

  The present invention has been made to solve the above-described problems, and provides a molten salt electrolysis apparatus and a molten salt electrolysis method having a mechanism capable of efficiently supplying a metal to a subsequent salt removal process. It is an object.

  The molten salt electrolysis apparatus according to the present invention includes a crucible for storing molten salt, a heating means for heating the crucible, an anode stored in the crucible for storing an electrolytic raw material and flowing the molten salt, and the molten salt An electrode device having a cathode that contacts and deposits electrolytic deposits, an electrolysis power supply circuit that supplies power between both electrodes of the electrode device, and an electrode that drives the movable electrode of the electrode device to be movable up and down and rotatable A drive device and a recovery device for recovering electrolytic deposits deposited on the cathode side by supplying power to the electrodes, and the recovery device is connected to a rotation mechanism or a vibration mechanism. The recovered metal is separated from the molten salt by the force of rotation or vibration of the vibration mechanism.

  Further, the molten salt electrolysis method according to the present invention includes a crucible for storing molten salt, a heating means for heating the crucible, an anode stored in the crucible for storing an electrolytic raw material and flowing the molten salt, and the molten salt An electrode device having a cathode in contact with the electrode for depositing electrolytic deposits, an electrolysis power supply circuit for supplying power between both electrodes of the electrode device, and a movable electrode of the electrode device being driven to be movable up and down and rotatable In an electrolysis apparatus having an electrode drive device and a recovery device that recovers electrolytic deposits deposited on the cathode side by supplying power to both electrodes, the recovery device is a rotating mechanism connected to the recovery device or The recovered metal is separated from the molten salt by the force of rotation or vibration of the vibration mechanism.

  According to the molten salt electrolysis apparatus and the molten salt electrolysis method of the present invention, in the subsequent salt removal process in which the recovered metal is taken out by electrolysis in the used reprocessing step, the salt can be efficiently removed and treated. The amount of metal supply per unit can be increased, and the productivity of metal fuel production can be improved.

1 is a schematic longitudinal sectional view showing a first embodiment of a molten salt electrolysis apparatus according to the present invention. The schematic longitudinal cross-sectional view which shows the drive state of the 1st Example of the molten salt electrolysis apparatus which concerns on this invention. The schematic longitudinal cross-sectional view which shows the 2nd Example of the molten salt electrolysis apparatus which concerns on this invention. The schematic longitudinal cross-sectional view which shows the modification of the 2nd Example of the molten salt electrolysis apparatus which concerns on this invention. The schematic longitudinal cross-sectional view which shows the 3rd Example of the molten salt electrolysis apparatus which concerns on this invention. The schematic longitudinal cross-sectional view which shows the prior art example of a molten salt electrolysis apparatus.

  Hereinafter, embodiments of a molten salt electrolysis apparatus and a molten salt electrolysis method according to the present invention will be described with reference to the accompanying drawings.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. In FIG. 1 and FIG. 2, the same parts as those in FIG.

  FIG. 1 shows the configuration of the molten salt electrolysis apparatus according to the first embodiment of the present invention, and FIG. 2 shows the driving state of the molten salt electrolysis apparatus shown in FIG.

  The molten salt electrolysis apparatus 20 in the first embodiment of the present invention has a crucible 14 that can be heated from room temperature to about 700 ° C. by the heater 5, and the molten salt 2 is accommodated in the crucible 14. The anode 3 and the cathode 4 that can be moved up and down are immersed in the molten salt 2.

  The molten salt 2 is formed of an alkali metal chloride such as sodium chloride, calcium chloride, lithium chloride or potassium chloride, or a mixed salt thereof. The anode 3 has a basket shape such as a mesh member, and spent fuel 8 is accommodated inside the basket. The metal recovery container 21 immersed in the molten salt 2 is supported by a support member 22 independently of the electrodes 3 and 4 and connected to a rotation drive motor 23 so as to be able to rotate at high speed. Yes.

  In the first embodiment of the present invention configured as described above, the collection container 21 is connected to the rotation drive motor 23 via the support member 22, so that the electrolytic treatment is stopped as shown in FIG. By pulling up the recovery container 21 from the molten salt 2 and rotating the recovery container 21 at a high speed in the direction of arrow A in the figure, the recovery container 21 is attached to the periphery of the movable electrode 4 by the scraping cutter shown in FIG. Most of the salt adhering to the recovered metal 24 accommodated in the container can be removed by being discharged from the recovery container 21 to the crucible 14 by centrifugal force.

  Therefore, in the subsequent salt removal process in which the recovered metal is removed by electrolysis in the used reprocessing step, it is possible to efficiently remove the salt and increase the amount of metal supplied to the processing unit, thereby producing metal fuel. Productivity can be improved.

  In addition, as a method for separating the recovered metal and the attached salt, the recovery container 21 is not provided with the rotation mechanism 23. The bottom and side surfaces of the recovery container 21 are made of fine mesh members or punching metal, etc., and the recovery container 21 moves up and down (vibrates) in small increments to largely separate the salt adhering to the recovery metal. It is also good.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIGS. 3 and 4, the same parts as those in FIG. 1 are denoted by the same reference numerals, and description of the structure of those parts is omitted.

  In the first embodiment, in order to separate the recovered metal 24 and the salt 2 adhering thereto, separation is performed by providing the recovery container 21 with a rotation mechanism 23 or an elevating mechanism. However, as the second embodiment, As a method for separating the recovered metal 24 and the salt 2, a method for separating the recovered metal 24 and the salt 2 attached thereto by heating the recovery container 21 is shown in FIGS. 3 and 4.

The molten salt electrolysis apparatus 30 in FIG. 3 has a heat insulating material 18 attached to the top of the crucible 14 when the anode 3 and the cathode 4 after the electrolysis is stopped, and is suspended by a suspension member 17 provided through the heat insulating material 18. The provided collection container heater 19 is attached to the opening of the collection container 21. The recovery container heater 19 raises the temperature of the recovery container 21 to about 800 ° C. to 1000 ° C. at which only the salt 2 evaporates, and releases the salt 2 from the discharge hole 16 formed in the recovery container heater 19. It can be vaporized and removed from the collection container 21.

  In addition, as a heating method of the recovery container 21 described above, instead of the recovery container heater 19, for example, a microwave application device 31 is provided as shown in FIG. 4 as a modification of the second embodiment to guide the recovery container 21. By applying microwave B from the wave tube 32 through the connector 33, the molten salt 2 is heated and evaporated, and discharged from the discharge hole 16, thereby separating the recovered metal 24 and a large amount of the salt 2 attached thereto. A possible molten salt electrolysis apparatus 30 is also possible.

  Therefore, in the subsequent salt removal process in which the recovered metal is removed by electrolysis in the used reprocessing step, it is possible to efficiently remove the salt and increase the amount of metal supplied to the processing unit, thereby producing metal fuel. Productivity can be improved. Furthermore, by reducing the number of drive parts, a highly reliable molten salt electrolyzer with a low probability of failure can be obtained.

(Third embodiment)
A third embodiment of the present invention will be described with reference to FIG. In FIG. 5, the same parts as those in FIG. 1 are denoted by the same reference numerals, and description of the structure of those parts is omitted.

In the molten salt electrolyzer 40 of FIG. 5, the support bar 41 of the anode basket 3 shown in the first embodiment has a hollow structure, and the valve 42 disposed on the hollow support bar 41 is opened. Thus, the spent fuel 8 can be supplied from the spent fuel storage tank 43 installed in the upper part of the main body of the molten salt electrolyzer 40.

  In the molten salt electrolyzer 40 configured as described above, electrolysis is performed, and the spent fuel 8 initially placed in the anode basket 3 is deposited on the cathode 4, and as the electrolysis proceeds, the spent fuel 8 in the anode basket 3 is When the rate of electrolysis decreases, the valve 42 above the anode basket 3 is opened, and the unprocessed spent fuel 8 can be supplied.

  As a result, the spent fuel can be electrolyzed with the electrolysis rate kept substantially constant. Therefore, electrolytic efficiency and productivity can be improved.

  Note that, in the spent fuel reprocessing process using the molten salt electrolysis method, spent fuel generated from a light water reactor or the like is in the form of an oxide. There is an electrolytic reduction process that reduces the metal to metal. The spent fuel supply mechanism shown in the present embodiment is not limited to the metal refining process, and can be similarly installed in an apparatus used in the electrolytic reduction process, and can exhibit the effect of improving productivity. .

DESCRIPTION OF SYMBOLS 1,20,30,40 ... Molten salt electrolysis apparatus, 2 ... Molten salt, 3 ... Anode basket (anode), 4 ... Movable electrode (cathode), 5 ... Heating heater (heating means), 6 ... Top cover, 7 ... Thermal insulation 8: Used cutting fuel with a cladding tube (spent fuel), 9: Cutter for scraping, 10 ... Electrode device, 11 ... Power supply for electrolysis, 12, 21 ... Recovery container, 13 ... Support member, 14 ... Crucible , 16 ... discharge hole, 17 ... suspension member, 18 ... heat insulating material, 19 ... heater for recovery container, 22 ... support member, 23 ... motor for rotation drive (rotation mechanism), 24 ... recovery metal, 31 ... microwave application device 32 ... Waveguide, 33 ... Connector, 41 ... Support rod, 42 ... Valve, 43 ... Spent fuel storage tank.

Claims (7)

A crucible for storing molten salt;
Heating means for heating the crucible;
An electrode device housed in the crucible, containing an electrolytic raw material and through which the molten salt flows, and a cathode in contact with the molten salt to deposit electrolytic deposits;
An electrolysis power supply circuit for supplying power between both electrodes of the electrode device;
An electrode driving device for driving the movable electrode of the electrode device to be movable up and down and rotatable;
A recovery device for recovering electrolytic deposits deposited on the cathode side by supplying power to both electrodes;
The recovery apparatus is connected to a rotation mechanism or a vibration mechanism, and the recovered metal and the molten salt are separated by a force generated by the rotation or vibration of the rotation mechanism or the vibration mechanism.   2. The molten salt electrolysis apparatus according to claim 1, wherein the bottom and side surfaces of the recovery container are formed of a net member or punching metal.   In place of the rotating mechanism, when the collection container is pulled up, it has a heater that can cover the collection container from the top separately from the heating means, and this heater evaporates only the salt in the collection container in the crucible. The molten salt electrolysis apparatus according to claim 1, wherein the evaporated salt is exhausted out of the recovery container through the opening of the recovery container. In place of the rotating mechanism, when the collection container is pulled up, it has a microwave heating device that can cover the collection container from the top separately from the heating means, and the microwave heating apparatus is used in the crucible to collect the collection container. 2. The molten salt electrolysis device according to claim 1, wherein the temperature of the container is raised to a temperature at which only the salt is evaporated, and the vaporized salt is exhausted out of the recovery container through the opening of the recovery container.   4. The molten salt electrolysis apparatus according to claim 1, wherein the anode is supplied with an electrolytic raw material from a storage tank that stores the electrolytic raw material. 5. A crucible for storing molten salt;
Heating means for heating the crucible;
An electrode device housed in the crucible, containing an electrolytic raw material and through which the molten salt flows, and a cathode in contact with the molten salt to deposit electrolytic deposits;
An electrolysis power supply circuit for supplying power between both electrodes of the electrode device;
An electrode driving device for driving the movable electrode of the electrode device to be movable up and down and rotatable;
In an electrolytic device having a recovery device for recovering electrolytic deposits deposited on the cathode side by supplying power to both electrodes,
This recovery apparatus is a molten salt electrolysis method characterized in that the recovered metal and the molten salt are separated by a force generated by rotation or vibration of a rotation mechanism or a vibration mechanism connected to the recovery apparatus. A crucible for storing molten salt;
Heating means for heating the crucible;
An electrode device housed in the crucible, containing an electrolytic raw material and through which the molten salt flows, and a cathode in contact with the molten salt to deposit electrolytic deposits;
An electrolysis power supply circuit for supplying power between both electrodes of the electrode device;
An electrode driving device for driving the movable electrode of the electrode device to be movable up and down and rotatable;
In an electrolytic device having a recovery device for recovering electrolytic deposits deposited on the cathode side by supplying power to both electrodes,
The recovery apparatus electrolyzes the molten salt by evaporating the molten salt by a heating device that covers an upper portion of the recovery apparatus to separate the recovered metal and the molten salt.

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