JP2006199547A - Method and apparatus for producing ammonium diuranate particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for producing ammonium diuranate particles useful for producing the fuel nuclei of fuel for a high temperature gas furnace capable of producing ammonium diuranate particles free from deformation or the like. <P>SOLUTION: The method and an apparatus for producing ammonium diuranate particles are characterized in that, in a batch type method for producing ammonium diuranate particles where a raw liquid comprising uranyl nitrate and a thickener is dropped into an ammonia aqueous solution as being in contact with ammonia vapor, so as to produce ammonium diuranate particles, the raw liquid used in the previous batch production and left in raw liquid transfer piping arranged for dropping the raw liquid into the ammonia aqueous solution is subjected to cooling treatment. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for producing ammonium heavy uranate particles, and more particularly, useful for producing a fuel core of a HTGR fuel capable of producing ammonium heavy uranate particles without deformation. The present invention relates to a method and an apparatus for producing ammonium biuranate particles.

  The core into which the fuel of the high-temperature gas reactor is charged is formed of graphite having a large heat capacity and excellent high-temperature soundness. In this high-temperature gas furnace, a gas such as helium gas that does not cause a chemical reaction even at a high temperature and has high safety is used as a cooling gas, so that the cooling gas can be safely taken out even when the outlet temperature is high. be able to. Therefore, even if the temperature of the core rises to about 900 ° C, the cooling gas heated to a high temperature can be used safely in a wide range of fields, including power generation, hydrogen production equipment, and other chemical plants. It is said.

  Moreover, the fuel for a high temperature gas reactor to be charged into the high temperature gas reactor generally includes a fuel core and a coating layer that covers the periphery of the fuel core. The fuel core is, for example, fine particles having a diameter of about 350 to 650 μm formed by sintering uranium dioxide into a ceramic form.

The coating layer has a four-layer structure, and has a first layer, a second layer, a third layer, and a fourth layer from the fuel core surface side. The first layer is formed of low-density pyrolytic carbon having a density of about 1 g / cm ³ , functions as a gas reservoir for gaseous fission products (FP), and serves as a buffer for absorbing fuel nuclear swelling. It also has the function of The second layer is formed of high-density pyrolytic carbon having a density of about 1.8 g / cm ³ and has a function of holding a gaseous FP. The third layer is formed of silicon carbide (SiC) having a density of about 3.2 g / cm ³ , has a function of holding a solid FP, and is a main strength member of the coating layer. The fourth layer is formed of high-density pyrolytic carbon having a density of about 1.8 g / cm ³ and has a function of holding a gaseous FP and also a function of a protective layer of the third layer. . The diameter of the coated particles forming these coating layers is usually about 500 to 1000 μm.

  The fuel nuclei (coated fuel particles) covered with the four coating layers are dispersed in a graphite matrix and molded into a fixed fuel compact shape. The fuel compact is a cylinder made of graphite. A certain amount is put into the tank and plugged up and down to form a fuel rod. Ultimately, this fuel rod is inserted into a plurality of insertion holes of the hexagonal column type graphite block, and a core is formed by arranging a plurality of the hexagonal column type graphite blocks in a honeycomb shape and stacking a plurality of stages. The

  Such a HTGR fuel can generally be manufactured through the following steps. First, a uranium nitrate solution is prepared by dissolving uranium oxide powder in nitric acid. Next, pure water and a thickening agent are added to this uranyl nitrate solution and mixed with stirring to prepare a stock solution for producing ammonium biuranate particles. A thickener is a substance added so that droplets of uranyl nitrate, which is a stock solution dropped in an aqueous ammonia solution described later, become spherical due to its surface tension during dropping.

  Examples of the thickener include polyvinyl alcohol, tetrahydrofurfuryl alcohol, a resin having a property of solidifying under alkaline conditions, polyethylene glycol, and metroses. The stock solution prepared in this manner is cooled to a predetermined temperature to obtain a drop stock solution whose viscosity is adjusted, and then ammonia is produced by vibrating the nozzle from a small-sized stock droplet lower nozzle of the stock droplet lowering device. It is dripped in the aqueous ammonia solution in the aqueous solution storage tank.

  The droplets dropped into the aqueous ammonia solution are sprayed with ammonia gas in the space up to the surface of the aqueous ammonia solution. Since the surface of the droplet gels by this ammonia gas and a film is formed, the droplet particles on which the gel film is formed are prevented from being deformed by impact when falling onto the surface of the aqueous ammonia solution, and the ammonia in the aqueous ammonia solution storage tank To form ammonium deuterated uranate particles. The formed ammonium heavy uranate particles are deposited in the lower part of the ammonia aqueous solution storage tank. If the formed ammonium heavy uranate particles are left in the deposited state, the lower ammonium heavy uranate particles are deformed by the load of the ammonium heavy uranate particles located in the upper part of the deposition of ammonium heavy uranate particles. End up. Therefore, the aqueous ammonia solution in the aqueous ammonia solution storage tank is so formed that the ammonium heavy uranate particles are not deformed by the deposition of ammonium heavy uranate particles, in other words, the ammonium heavy uranate particles do not remain deposited. , A liquid flow is formed from the lower side to the upper side of the ammonia aqueous solution storage tank.

  The ammonium heavy uranate particles formed in the ammonia aqueous solution storage tank are transferred to a post-treatment device that is connected to the ammonia aqueous solution storage tank. The transfer of the heavy ammonium uranate particles to the post-treatment device is normally performed by opening a valve of a pipe connecting the ammonia aqueous solution storage tank and the post-treatment device and dropping it together with the aqueous ammonia solution by its own weight. In this post-treatment device, while rotating the post-treatment tank, by heating, the uranyl nitrate and ammonia are completely reacted to the center of the particles to produce ammonium heavy uranate (ripening treatment), heavy uranic acid with hot water, etc. It is an apparatus that performs a process for cleaning ammonium particles (cleaning process) and a process for drying (drying process).

  Aged, washed and dried ammonium heavy uranate particles are roasted in air to form uranium trioxide particles. Further, the uranium trioxide particles are reduced and sintered to become high-density ceramic-like uranium dioxide particles. The uranium dioxide particles thus formed are classified and obtained as fuel core particles having a predetermined particle size.

The fuel core particles obtained in this way are loaded onto a fluidized bed and coated by thermally decomposing the coating gas. For example, the first layer can be formed by pyrolyzing acetylene at about 1400 ° C., and the second and fourth layers can be formed by pyrolyzing propylene at about 1400 ° C. it can. For example, the third layer can be formed by thermally decomposing methyltrichlorosilane at about 1600 ° C. A normal fuel compact can be manufactured by press-molding or molding coated fuel particles into a hollow cylindrical shape or a medium-density cylindrical shape together with a graphite matrix material composed of graphite powder, a binder, and the like, followed by firing. (See Non-Patent Documents 1 and 2).
"Reactor Material Handbook" p221-p247, published October 31, 1977, published by Nikkan Kogyo Shimbun "Nuclear Power Handbook" p161-p169, issued on December 20, 1995, Ohm Corporation

  By the way, in the manufacturing process of such a high temperature gas reactor fuel, in the process of manufacturing ammonium heavy uranate particles by dripping a stock solution containing uranyl nitrate and a thickener into an aqueous ammonia solution, An apparatus for producing ammonium heavy uranate particles as shown in FIG. 2 has been adopted, and a production method of ammonium heavy uranate particles by a batch method has been mainstream.

  The conventional apparatus 1 for producing ammonium heavy uranate particles includes a stock solution tank 3 for storing a stock solution 2 containing uranyl nitrate and a thickener, and a stock solution lower nozzle 6 for dropping the stock solution 2 into an aqueous ammonia solution 9. A stock solution transfer pipe 5 for transferring to the dropping device 7 and an aqueous ammonia solution storage tank 10 for storing an aqueous ammonia solution 9 are formed. Reference numeral 4 denotes a stock solution feed pump, 8 denotes a dropping stock solution dropped from the dropping nozzle 6, and 11 denotes ammonium heavy uranate particles.

  In order to produce ammonium heavy uranate particles by the production apparatus 1 for ammonium heavy uranate particles, first, a uranium nitrate solution is prepared by dissolving uranium oxide powder in nitric acid. Subsequently, pure water and a thickener are added to this uranyl nitrate solution and mixed by stirring to prepare a stock solution 2. The prepared stock solution 2 is transferred to a raw liquid drop lower device 7 through a stock solution feed pump 4 through a stock solution transfer pipe 5. Subsequently, the stock solution 2 transferred to the original droplet lowering device 7 is dropped from the original droplet lowering nozzle 6 to be dropped into the aqueous ammonia solution 9 as a dripping stock solution 8. Ammonia gas is sprayed onto the droplet 8 that is dropped into the aqueous ammonia solution 9 in a space that reaches the surface of the aqueous ammonia solution 9. In this way, uranyl nitrate and ammonia react in the aqueous ammonia storage tank 10 to form ammonium heavy uranate particles 11.

  However, in the production of ammonium heavy uranate particles by such a batch method, the stock solution 2 used in the previous batch production remains in the stock solution transfer pipe 5 (indicated by a bold line in FIG. 2). Hereinafter, the stock solution remaining in the stock solution transfer pipe may be referred to as “residual stock solution”.) When starting the dropping of the stock solution, this remaining stock solution must not be dropped into the aqueous ammonia solution 9 from the nozzle 6 below the stock droplet. Did not get. That is, when trying to transfer the stock solution 2 used for the new batch production to the stock droplet lowering device 7 by the stock solution transfer pipe 5, the remaining stock solution is pushed out when the stock solution is dropped by the transfer of the new stock solution 2, and the remaining stock solution is That is, it is dropped from the original droplet lower nozzle 6 to the aqueous ammonia solution 9.

  The remaining stock solution usually has different properties or properties from the new stock solution 2 whose temperature is controlled in the stock solution storage tank 3 at 5 to 15 ° C. For this reason, the ammonium heavy uranate particles 11 formed when the remaining stock solution is dropped into the aqueous ammonia solution 9 are easily deformed, and the ammonium heavy uranate particles 11 are aged, washed, dried, roasted, reduced and sintered. There is a problem that specifications such as sphericity, outer diameter, and internal structure of uranium dioxide particles produced through each process cannot be satisfied, which leads to a decrease in yield of uranium dioxide particles produced. The problem is presumed to be caused by the temperature of the remaining stock solution becoming room temperature, higher than the temperature of the new stock solution 2, and the viscosity of the stock solution being lowered.

  This invention eliminates such conventional problems, and can produce ammonium heavy uranate particles that are free from deformation, and can be used to produce fuel nuclei for HTGR fuel. It is an object of the present invention to provide a method and a manufacturing apparatus.

  As a result of various studies on the stock solution remaining in the stock solution transfer pipe in the previous batch manufacturing process in order to solve the above problem, the present inventor said that the above problem can be solved by cooling and using this remaining stock solution. As a result, the present invention has been completed based on this finding.

That is, the first means for solving the problems of the present invention is as follows:
(1) A batch-type production method of ammonium heavy uranate particles in which a stock solution containing uranyl nitrate and a thickener is dropped into an aqueous ammonia solution, and the stock solution is converted into an aqueous ammonia solution in the previous batch production. A method for producing ammonium heavy uranate particles, comprising cooling the stock solution remaining in a stock solution transfer pipe arranged for dripping.

As a preferable aspect in the first means of the present invention,
A method for producing ammonium biuranate particles having means for preventing contact between the stock solution remaining in the stock solution transfer pipe and ammonia vapor volatilized from the aqueous ammonia solution can be given.

The second means for solving the above-mentioned problem of the present invention is as follows:
(2) A stock solution storage tank for storing a stock solution containing uranyl nitrate and uranyl nitrate and a thickener; a stock solution transfer pipe for transporting the stock solution to a stock drop lower device; Is a batch-type ammonium heavy uranate particle storage device in which ammonia aqueous solution storage tanks are arranged in that order, and the stock solution remaining in the stock solution transfer pipe in the previous batch production is cooled to the stock solution transfer pipe. An apparatus for producing ammonium deuterated uranate particles, characterized by comprising means.

As a preferable aspect in the second means of the present invention,
Ammonium deuterated uranate comprising a partition plate between the raw droplet lowering device and the aqueous ammonia solution storage tank for preventing contact between the undiluted solution remaining in the undiluted solution transfer pipe and ammonia vapor volatilized from the aqueous ammonia solution. Mention may be made of an apparatus for producing particles.

  According to the present invention, after the stock solution containing uranyl nitrate which is not temperature-controlled and remained in the stock solution transfer pipe in the previous batch production process is cooled to obtain a stock solution used for new batch production, an aqueous ammonia solution A method and an apparatus for producing batch-type ammonium heavy uranate particles that are produced by dripping onto an aqueous solution are provided. When ammonium heavy uranate particles are produced by the production method and production apparatus, aging and washing of the ammonium heavy uranate particles are performed. To produce ammonium heavy uranate particles that do not cause deformation in the sphericity, outer diameter, internal structure, etc. of uranium dioxide particles produced through the steps of drying, roasting, reduction and sintering. be able to. Therefore, there is a great deal of contribution to the field of manufacturing high temperature gas reactor fuels.

  (1) The method for producing ammonium heavy uranate particles according to the present invention is a batch method for producing ammonium heavy uranate particles in which a stock solution containing uranyl nitrate and a thickener is dropped into an aqueous ammonia solution. In the previous batch production, the raw solution remaining in the raw solution transfer pipe arranged for dripping the raw solution into the aqueous ammonia solution is cooled.

  Further, (2) an apparatus for producing ammonium biuranium particles according to the present invention comprises a stock solution storage tank for storing a stock solution containing uranyl nitrate and a thickener, a stock solution transfer pipe for transporting the stock solution to a stock drop lower, and the stock solution Is a batch type ammonium heavy uranate particle production apparatus in which an aqueous ammonia storage tank for storing an ammonia aqueous solution and an ammonia aqueous solution storage tank for storing the ammonia aqueous solution are arranged in that order. It is a manufacturing apparatus formed by performing a treatment for cooling the stock solution remaining in the stock solution transfer pipe.

  A method and apparatus for producing ammonium biuranium particles according to the present invention will be described with reference to FIGS.

  FIG. 1 is a diagram showing an example of an apparatus for producing ammonium heavy uranate particles according to the present invention. An apparatus for producing ammonium heavy uranate particles 1 according to the present invention comprises a stock solution storage tank 3 for storing a stock solution 2 containing uranyl nitrate and a thickener, and a stock droplet lower nozzle 6 for dropping the stock solution 2 into an aqueous ammonia solution 9. A batch system in which a stock solution transfer pipe 5 for transporting to a dropping device 7, a stock droplet lower device 7 having a stock droplet lower nozzle 6 for dropping the stock solution 2 onto an aqueous ammonia solution 9, and an aqueous ammonia solution storage tank 10 for storing the aqueous ammonia solution 9 are arranged in that order. In the apparatus for producing ammonium heavy uranate particles, the stock solution transfer pipe 5 has means for cooling the stock solution remaining in the stock solution transfer pipe 5 in the previous batch production.

  The means for cooling the stock solution remaining in the stock solution transfer pipe 5 (indicated by a thick line in FIG. 1) is a means capable of cooling the remaining stock solution at room temperature to 5 to 15 ° C. As long as there is no particular limitation, for example, as shown in FIG. 1, a means for winding a cooling water pipe 14 around the stock solution transfer pipe 5 can be mentioned. Cooling water is supplied to the wound cooling water pipe 14 by a water supply device 12 through a water supply pipe 13 connected to the cooling water pipe 14. When the cooling water passes through the cooling water pipe 14, the remaining stock solution is cooled, and the cooling water that has reached a low temperature state is returned to the water feeding device 12 through the return water pipe 15 connected to the cooling water pipe 14. If necessary, the water feeding, cooling and returning water may be repeated.

  As a means for cooling the remaining stock solution, a double tube comprising an inner tube and an outer tube can be used as the stock solution transfer pipe 5. In this case, the inner pipe can be used for stock solution transfer and the outer pipe for passing water. Water is optimal as a medium for cooling the remaining stock solution, but is not limited to water, and ammonia, methyl chloride, freon, or the like may be used.

  In the production apparatus 1 for ammonium heavy uranate particles, it is preferable that a partition plate 16 is installed between the original droplet lower 7 and the aqueous ammonia storage tank 10. The partition plate 16 is fixedly supported by a partition plate support 17, and the undiluted solution remaining in the undiluted solution transfer pipe 5 contacts ammonia vapor volatilized from the aqueous ammonia solution 9 stored in the aqueous ammonia solution storage tank 10. It is the board provided in order to prevent doing. This partition plate 16 is attached as a detachable partition plate after the completion of dropping the original droplet. Alternatively, the original droplet lowering device 7 may be moved upward while the partition plate 16 is fixed to achieve the intended purpose.

  As long as the shape of the partition plate 16 is a plate shape that does not contact the undiluted solution remaining in the undiluted solution transfer pipe 5 and the ammonia vapor volatilized from the ammonia aqueous solution 9 stored in the ammonia aqueous solution storage tank 10, There is no particular limitation. For example, as shown in FIG. 1, the flat plate installed so that the upper end part whole surface of the ammonia aqueous solution storage tank 10 which stores the ammonia aqueous solution 9 may be mentioned.

The method for producing ammonium heavy uranate particles of the present invention is as follows.
First, a uranyl nitrate solution is prepared by dissolving uranium oxide powder in nitric acid using the conventional batch production apparatus 1 of ammonium heavy uranate particles shown in FIG. Subsequently, pure water and a thickener are added to this uranyl nitrate solution and mixed by stirring to prepare a stock solution 2.

  The prepared stock solution 2 is transferred via a stock solution feed pump 4 to a stock droplet lowering device 7 having a stock droplet lower nozzle 6 through a stock solution transfer pipe 5. Subsequently, the stock solution 2 transferred to the original droplet lowering device 7 is dropped from the original droplet lowering nozzle 6 to be dropped into the aqueous ammonia solution 9 as a dripping stock solution 8. In this way, uranyl nitrate and ammonia react in the aqueous ammonia storage tank 10 to form ammonium heavy uranate particles 11.

  As described above, ammonium heavy uranate particles 11 are manufactured, and subsequently, production of ammonium heavy uranate particles 11 is started with a new batch. Prior to the start of the production of the ammonium heavy uranate particles 11, a cooling water pipe 15 is wound around the stock solution transfer pipe 5 in the ammonium heavy uranate particle production apparatus 1 shown in FIG. A partition plate 16 is installed between the aqueous solution storage tank 10 and the apparatus for producing ammonium biuranate particles shown in FIG.

  In order to explain the present invention, for convenience, a cooling water pipe 15 is wound around the stock solution transfer pipe 5 in the conventional ammonium heavy uranate particle production apparatus 1 shown in FIG. 2, and the ammonium uranate shown in FIG. Although the apparatus for producing particles is practically used, in the apparatus for producing ammonium heavy uranate particles 1 shown in FIG. 1, a production apparatus in a state in which cooling water is not fed to the cooling water pipe 15 is shown in FIG. This is an apparatus 1 for producing ammonium biuranate particles. However, the partition plate 16 is installed prior to the start of production of new ammonium heavy uranate particles 11.

  Using the apparatus 1 for producing ammonium heavy uranate particles shown in FIG. 1, the stock solution 2 (indicated by a thick line in FIG. 1) remaining in the stock solution transfer pipe 5 in the previous batch production is cooled. Therefore, the cooling water is supplied to the cooling water pipe 15 by the water supply device 12 through the water supply pipe 13 connected to the cooling water pipe 15. During this time, ammonia vapor volatilized from the aqueous ammonia solution 9 stored in the aqueous ammonia storage tank 10 is mixed into the lower part of the lower nozzle 6 of the original liquid droplets by the partition plate 16, and the undiluted solution remaining in the undiluted solution transfer pipe 5 and the ammonia vapor. And are not in contact. While the stock solution 2 remaining in the stock solution transfer pipe 5 is cooled, the remaining stock solution 2 remains in the stock solution transfer pipe 5.

  The production of the ammonium heavy uranate particles 11 by a new batch is carried out by transferring the newly prepared stock solution through the stock solution transfer pipe 5 so as to send the remaining stock solution cooled to 5 to 15 ° C. The transferred remaining stock solution is transferred to the original droplet lowering device 7 having the original droplet lower nozzle 6 in the ammonium heavy uranate particle manufacturing apparatus 1 of the present invention shown in FIG. The remaining dripping stock solution 8 falls and the uranyl nitrate and ammonia react in the aqueous ammonia storage tank 10 to form ammonium heavy uranate particles 11.

  In this way, after producing ammonium deuterated uranate particles by the first batch method, ammonium deuterated uranate particles by the second batch method were produced, and then the third and fourth times were repeated. Ammonium biuranate particles can be produced.

  The apparatus for producing ammonium heavy uranate particles of the present invention is produced using a metal material or glass, and as this metal material, stainless steel excellent in mechanical strength and rust prevention properties is preferable. In addition, the overall capacity or size of the production apparatus is appropriately determined depending on the production scale of ammonium uranate particles, the viewpoint of critical safety measures, and the like.

  The method and apparatus for producing ammonium heavy uranate particles according to the present invention, after cooling the stock solution containing uranyl nitrate that is not temperature-controlled and remained in the stock solution transfer pipe in the previous batch production process, was then added dropwise to the aqueous ammonia solution. Therefore, when ammonium heavy uranate particles are produced by this production method and production apparatus, aging, washing, drying, roasting of the ammonium heavy uranate particles, It is possible to produce ammonium heavy uranate particles that are free from deformation in the sphericity, outer shape, internal structure, etc. of the uranium dioxide particles produced through the reduction and sintering processes. For this reason, it is very useful for the manufacture of fuel for HTGR.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the examples.
(Example)〕

Uranyl nitrate solution was prepared by dissolving 5 kg of U ₃ O ₈ powder in 3.3 L of 60% by mass nitric acid and water. In 7.5 L of this uranyl nitrate solution, a polyvinyl alcohol aqueous solution [polyvinyl alcohol powder amount 75 g / (polyvinyl alcohol + water) L] and tetrahydrofurfuryl alcohol are used as a thickener in a ratio of 43% by volume with respect to the dropping stock solution. Thus, a stock solution 24L was prepared. The uranium concentration of this stock solution after 120 minutes was 180 g / L, the temperature was 12 ° C., and the viscosity was 56 × 10 ⁻³ Pa · s (56 cP).

The stock solution prepared as described above is produced by using the ammonium heavy uranate particle manufacturing apparatus 1 shown in FIG. It was stored as a stock solution 2 in a stock solution storage tank 3). This stock solution 2 was transferred to a stock drop lower device 7 having a stock drop lower nozzle 6 by way of a stock solution transfer pipe 5 via a stock solution feed pump 4. Next, while spraying ammonia gas to the stock solution 2, the stock solution 2 is dropped from the nozzle 6 under the original droplets into an ammonia aqueous solution storage tank 10 storing 28% by mass ammonia aqueous solution 9 to react uranyl nitrate and ammonia, thereby deuterating uranic acid. Ammonium particles 11 were produced. At this time, the amount of the stock solution 2 (indicated by a thick line in FIG. 2) remaining in the stock solution transfer pipe 5 was 750 mL. Further, the temperature after the lapse of 8 hours from the end of the original droplet was 24 ° C., and the viscosity was 37 × 10 ⁻³ Pa · s (37 cP).

  As described above, after the ammonium heavy uranate particles 11 are manufactured, the partition plate 16 is attached as shown in FIG. 1 and cooled to the cooling water pipe 15 via the water supply pipe 13 connected to the cooling water pipe 15. Water was fed by the water feeding device 12 and the temperature of the stock solution 2 remaining in the stock solution transfer pipe 5 was maintained at 12 ° C.

  Thereafter, after 2 days, stock solution 2 was prepared again in the same manner as described above. This undiluted solution had a uranium concentration of 180 g / l, a temperature of about 13 ° C., and a viscosity of 55 cP. Next, the partition plate 16 is removed, and the stock solution 2 maintained at 12 ° C. remaining in the stock solution transfer pipe 5 is transferred by transferring the stock solution 2 prepared again as the stock solution 2 through the stock solution transfer pipe 5. did.

  The transferred remaining stock solution is transferred to the original drop lower device 7 having the original droplet lower nozzle 6 and falls as the remaining dropped stock solution 12 from the original droplet lower nozzle 6, and the ammonium heavy uranate particles 11 are again formed in the same manner as described above. Manufactured. At this time, no deformation was observed in the ammonium heavy uranate particles 11 formed in the aqueous ammonia solution 9.

  The ammonium heavy uranate particles 11 produced in this manner are reacted with uranyl nitrate and ammonia to the center of the particles by heating to produce ammonium heavy uranate, and the ammonium heavy uranate particles are washed with warm water. Washing treatment, drying treatment and roasting treatment in the atmosphere are performed to form uranium trioxide particles. Further, the uranium trioxide particles are subjected to reduction treatment and sintering treatment to form a high-density ceramic-like material. Uranium dioxide particles were obtained.

In addition, each said process is as follows.
Aging treatment: Ammonium deuterated uranium particles were placed in a drying tank together with the aqueous ammonia solution used and aged while rotating at 80 ° C. for 1 hour.
Washing treatment: Washing treatment was performed 3 times with 30 L of 80 ° C. water and then with 20 L of ethyl alcohol for 30 minutes in a drying bath.
Drying treatment: The drying treatment was performed while rotating at 100 ° C. for 1 hour while maintaining a slight negative pressure.
Roasting treatment: roasting treatment was performed at 550 ° C. for 1 hour in the air.
Reduction treatment: Reduction treatment was performed at 500 ° C. for 2 hours in a hydrogen-nitrogen mixed gas atmosphere.
Sintering: Sintering was performed at 1550 ° C. for 30 minutes in a hydrogen-nitrogen mixed gas atmosphere.

The uranium dioxide particles thus obtained were subjected to outer diameter sorting using a sieve and sphericity sorting using a sphericity sorter, and the yield was examined. As a result, 19 g of defective products were found. .
(Comparative example)

Uranyl nitrate solution was prepared by dissolving 5 kg of U ₃ O ₈ powder in 3.3 L of 60% by mass nitric acid. In 7.5 L of this uranyl nitrate solution, a polyvinyl alcohol aqueous solution [polyvinyl alcohol powder amount 75 g / (polyvinyl alcohol + water) L] and tetrahydrofurfuryl alcohol are used as a thickener in a ratio of 43% by volume with respect to the dropping stock solution. Thus, a stock solution 24L was prepared. After 120 minutes, the stock solution had a uranium concentration of 180 g / L, a temperature of 13 ° C., and a viscosity of 55 × 10 ⁻³ Pa · s (55 cP).

  The stock solution prepared as described above was stored as a stock solution 2 in the stock solution storage tank 3 of the ammonium biuranate particle production apparatus 1 shown in FIG. This stock solution 2 was transferred to a stock drop lower device 7 having a stock drop lower nozzle 6 by way of a stock solution transfer pipe 5 via a stock solution feed pump 4. Next, while blowing ammonia gas to the stock solution 2, the stock solution 2 is dropped from the nozzle 6 under the original droplets into an ammonia aqueous solution storage tank 10 storing 28 mass% ammonia aqueous solution 9 to react uranyl nitrate and ammonia, thereby deuterating uranic acid. Ammonium particles 11 were produced. At this time, the amount of the stock solution 2 (indicated by a thick line in FIG. 2) remaining in the stock solution transfer pipe 5 was 750 mL.

  As described above, after the ammonium heavy uranate particles 11 were produced, a stock solution was prepared again in the same manner as described above after two days. This undiluted solution had a uranium concentration of 180 g / L, a temperature of 13 ° C., and a viscosity of 55 cP. The temperature of the stock solution 2 remaining in the stock solution transfer pipe 5 was 22 ° C., and the viscosity was 39 cP. Thereafter, ammonium heavy uranate particles 11 were produced in the same manner as described above with the stock solution 2 remaining in the stock solution transfer pipe 5. At this time, in the initial stage in which the stock solution 2 was dropped into the ammonia aqueous solution storage tank 10 to produce ammonium heavy uranate particles 11, a distorted shape was visually recognized in the ammonium heavy uranate particles 11 formed in the ammonia aqueous solution 9.

  The thus produced ammonium heavy uranate particles 11 were subjected to the same ripening treatment, washing treatment, drying treatment and roasting treatment as described above to form uranium trioxide particles. Further, the uranium trioxide particles The same reduction treatment and sintering treatment as described above were performed to obtain high-density ceramic-like uranium dioxide particles.

  The uranium dioxide particles thus obtained were subjected to outer diameter sorting using a sieve and sphericity sorting using a sphericity sorter, and the yield was examined. As a result, 156 g of defective products were found. . The generation of a relatively large amount of defective products is presumed to be caused by the distorted ammonium heavy uranate particles 11.

FIG. 1 is a diagram showing an example of an apparatus for producing ammonium heavy uranate particles according to the present invention. FIG. 2 is a diagram showing a conventional apparatus for producing ammonium heavy uranate particles.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus of ammonium heavy uranate particle 2 Stock solution 3 Stock solution storage tank 4 Stock solution feed pump 5 Stock solution transfer pipe 6 Stock droplet lower nozzle 7 Stock drop lowering device 8 Dripping stock solution 9 Ammonia aqueous solution 10 Ammonia aqueous solution storage 11 Heavy ammonium uranate particle 12 Water delivery device 13 Water supply pipe 14 Cooling water pipe 15 Return water pipe 16 Partition plate 17 Partition plate support

Claims (4)

  A batch-type production method of ammonium heavy uranate particles in which a stock solution containing uranyl nitrate and a thickener is dropped into an aqueous ammonia solution, and the stock solution is dropped into the aqueous ammonia solution in the previous batch production. A method for producing ammonium heavy uranate particles, comprising cooling the stock solution remaining in the stock solution transfer pipe disposed in the vessel.   The method for producing ammonium biuranate particles according to claim 1, further comprising means for preventing contact between the stock solution remaining in the stock solution transfer pipe and ammonia vapor volatilized from the aqueous ammonia solution.   A stock solution storage tank for storing a stock solution containing uranyl nitrate and a thickener, a stock solution transfer pipe for transporting the stock solution to a stock drop lower device, a stock drop lower for dropping the stock solution into an aqueous ammonia solution, and an aqueous ammonia solution storage tank for storing the aqueous ammonia solution Are arranged in that order in a batch-type ammonium heavy uranate particle production apparatus, the stock solution transfer pipe having means for cooling the stock solution remaining in the stock solution transfer pipe in the previous batch production An apparatus for producing ammonium heavy uranate particles, comprising: The partition plate for preventing contact between the stock solution remaining in the stock solution transfer pipe and the ammonia vapor volatilized from the ammonia solution is installed between the stock droplet lowering device and the ammonia solution storage tank. An apparatus for producing ammonium heavy uranate particles as described.

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