JP2006225242A - Apparatus for manufacturing ammonium diuranate particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for manufacturing ammonium diuranate particles, with which the ammonium diuranate particles each having high sphericity can be manufactured. <P>SOLUTION: The apparatus for manufacturing the ammonium diuranate particles is equipped with: a storage tank for storing an aqueous ammonia solution; a dropping device having a dropping nozzle capable of dropping a uranyl nitrate-containing raw liquid, which is arranged at the upper part of the storage tank; and an overflow device provided at the peripheral edge of the liquid surface of the aqueous ammonia solution. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for producing ammonium heavy uranate particles, and more particularly to an apparatus for producing ammonium heavy uranate particles that can produce ammonium heavy uranate particles with good sphericity.

  In the high temperature gas reactor, the core structure into which the fuel for the high temperature gas reactor is charged is made of graphite having a large heat capacity and good high-temperature soundness. In this high-temperature gas furnace, by using a gas such as helium gas that does not cause a chemical reaction even at a high temperature as the cooling gas, the safety is high and the cooling gas can be taken out even when the outlet temperature is high. . For this reason, even if the temperature rises to about 900 ° C. in the core, it is possible to use heat safely in a wide range of fields such as hydrogen production and chemical plants as well as power generation.

  On the other hand, the fuel for a HTGR to be charged into the HTGR generally includes a fuel nucleus and a coating layer coated around the fuel nucleus. 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 includes a first layer, a second layer, a third layer, and a fourth layer from the fuel core surface side. The diameter of the coated particles constituting the coating layer is, for example, about 500 to 1000 μm.

The first layer is made of low-density pyrolytic carbon having a density of about 1 g / cm ³ , functions as a gas reservoir for gaseous fission products (hereinafter sometimes referred to as “FP”), and fuel nucleus. It has a function as a buffer that absorbs swelling. The second layer is made of high-density pyrolytic carbon having a density of about 1.8 g / cm ³ and has a function of holding the gaseous FP.

The third layer is made of carbon silicon having a density of about 3.2 g / cm ³ (hereinafter sometimes abbreviated as “SiC”) and has a function to be held by the solid FP. It is a strength material. The fourth layer is made of high-density pyrolytic carbon having a density of about 1.8 g / cm ³ similar to that of the second layer, and has a function of holding the gaseous FP and also functions as a protective layer of the third layer. It is what you have.

  The HTGR fuel as described above is generally manufactured through the following steps. First, uranium oxide powder is dissolved in nitric acid to obtain a uranyl nitrate stock solution. Next, pure water and a thickener are added to this uranyl nitrate stock solution, and stirred to obtain a dropping stock solution. The prepared dripping stock solution is cooled to a predetermined temperature to adjust the viscosity, and then dropped into an aqueous ammonia solution using a small-diameter dropping nozzle.

  The droplets dropped on the aqueous ammonia solution pass through the ammonia gas atmosphere before reaching the surface of the aqueous ammonia solution. Since the liquid droplets pass through the ammonia gas atmosphere, the surface of the liquid droplets is gelled, so that deformation when reaching the surface of the aqueous ammonia solution can be prevented. Uranyl nitrate in the aqueous ammonia solution sufficiently reacts with ammonia to form ammonium heavy uranate particles (hereinafter sometimes referred to as “ADU particles”).

  The ammonium heavy uranate particles are dried and then baked in the air to form uranium trioxide particles. Further, the uranium trioxide particles are reduced and sintered to become high-density ceramic uranium dioxide particles. The uranium dioxide particles are screened, that is, classified to obtain fuel core particles having a predetermined particle size.

  The fuel core particles are loaded onto the fluidized bed, and the gas for forming the coating layer is pyrolyzed to form the coating layer on the surface of the fuel core particles. In the case of the low-density pyrolytic carbon of the first layer of the coating layer, acetylene is pyrolyzed at about 1300 ° C. In the case of the high-density pyrolytic carbon of the second layer and the fourth layer of the coating layer, propylene is pyrolyzed at about 1400 ° C. Furthermore, when the third layer of the coating layer is SiC, methyltrichlorosilane is thermally decomposed at about 1500 ° C.

  After the coating layer is formed and the coated fuel particles are formed, the HTGR fuel is formed as a general fuel compact. This fuel compact is obtained by press-molding or molding a HTGR fuel into a hollow cylindrical shape together with a graphite matrix material made of graphite powder, a binder, etc., and then firing (Non-Patent Documents 1 to 5). reference).

S. Kato "Fabrication of HTTR First Loading fuel", IAEA-TECCDOC-1210, 187 (2001) N. Kitamura "Present status of initial core fuel fabrication for the HTTR" IAEA-TECCDOC-988, 373 (1997) Kimio Hayashi, “High Temperature Engineering Test Reactor Design Policy, Manufacturability and Comprehensive Soundness Evaluation” JAERI-M 89-162 (1989) Kazuo Tsuji, “Development of Advanced Technology for HTGR Fuel Production” JAERI-Research 98-070 (1998) Hasegawa Masayoshi, Mishima Yoshimi supervision "Reactor Material Handbook", published on October 31, 1977, pages 221-247, Nikkan Kogyo Shimbun

  In the procedure for producing ammonium heavy uranate particles, as described above, first, a dropping stock solution containing uranyl nitrate is dropped into a storage tank for storing an aqueous ammonia solution. The dripping stock solution becomes gel-like ammonium biuranate particles in an aqueous ammonia solution. During this work, usually a dripping stock solution containing a certain amount of uranium is dropped, but by the ammonium heavy uranate particles produced, the liquid level of the aqueous ammonia solution is increased compared to before the dripping work, There is a situation in which the dropping conditions are different at the start of dropping and at the end of dropping.

  When dropping the dropping stock solution, the distance between the tip of the dropping nozzle used and the liquid level of the aqueous ammonia solution is important in order to make the shape of the gelled ammonium heavy uranate particles appropriate. For example, if this distance is too large, the impact of the droplets of the undiluted solution upon landing on the liquid surface of the aqueous ammonia solution increases, so that the gel-like ammonium uranate particles do not become spherical and the heavy uranium produced The sphericity of the ammonium acid particles may deteriorate. Also, if this distance is too close, due to the vaporization of ammonia in the aqueous ammonia solution, the dropping undiluted solution in the dropping nozzle and ammonia react to cause gelation of the dropping undiluted solution in the dropping nozzle. There may be a problem in dropping the dropping solution.

  That is, if the distance between the tip of the dropping nozzle used and the liquid level of the aqueous ammonia solution is not constant, the dripping conditions will change, and the sphericity of the produced ammonium heavy uranate particles will deteriorate. There is a problem.

  It is an object of the present invention to provide an ammonium heavy uranate particle production apparatus that can solve such conventional problems and produce ammonium heavy uranate particles with good sphericity.

As means for solving the problems,
The first aspect of the present invention is provided in a storage tank that stores an aqueous ammonia solution, a dropping device that is disposed above the storage tank and has a dropping nozzle that can drop a uranyl nitrate-containing stock solution, and a liquid surface periphery of the aqueous ammonia solution. An apparatus for producing ammonium heavy uranate particles, comprising an overflow device.

  According to the present invention, the uranyl nitrate-containing stock solution dropped from the tip portion of the dropping nozzle reaches the liquid surface of the aqueous ammonia solution. The droplets of the uranyl nitrate-containing stock solution reaching the liquid level react with ammonia to produce gel-like ammonium uranate particles. The liquid level of the aqueous ammonia solution rises by the volume of the produced ammonium heavy uranate particles. The amount of the ammonia aqueous solution that has risen overflows from the peripheral surface of the ammonia aqueous solution to the overflow device. Therefore, the liquid level of the aqueous ammonia solution is always maintained at a constant height during the droplet dropping period. By keeping the liquid level constant, the distance between the tip of the dropping nozzle used and the liquid level of the aqueous ammonia solution can be made constant. By making this distance constant, the conditions for dropping droplets can be kept constant, so that it is possible to produce ammonium heavy uranate particles with good sphericity.

  Hereinafter, an apparatus for producing ammonium heavy uranate particles (hereinafter sometimes referred to as “ADU particle production apparatus”) according to the present invention will be described with reference to the drawings. Further, the ammonium heavy uranate particles may be hereinafter referred to as ADU particles.

  As shown in FIG. 1, the ADU particle manufacturing apparatus 1 includes a storage tank 2, a dropping device 3, and an overflow device 5.

  The storage tank 2 stores an aqueous ammonia solution. The storage tank 2 may be a tank having heat resistance and corrosion resistance. There is no restriction | limiting in particular in the shape of the storage tank 2, What is necessary is just to be formed in the cylinder shape which has cylindrical shape or polygonal shape. The storage tank 2 has an opening 2A at the top thereof.

  As shown in FIG. 1, the dropping device 3 includes a dropping nozzle 4 that is disposed above the storage tank 2 and can drop a uranyl nitrate-containing stock solution. The tip opening 4 </ b> A of the dripping nozzle 4 is disposed so as to face the liquid surface of the aqueous ammonia solution stored in the storage tank 2. Moreover, the dripping nozzle 4 may be one or plural. When dropping the uranyl nitrate-containing stock solution, a vibrator (not shown) is attached to the dropping nozzle 4 so that the dropping nozzle 4 is vibrated in the dropping direction of the uranyl nitrate-containing stock solution and / or in the direction orthogonal to the dropping direction. You can also.

  As shown in FIG. 1, the other end of the dropping nozzle 4 is connected to a stock solution supply path 6, and the stock solution supply path 6 is connected to a stock solution storage tank (not shown). The uranyl nitrate-containing stock solution stored in the stock solution storage tank (not shown) reaches the dropping nozzle 4 through the stock solution supply path 6 and is dropped into the ammonia aqueous solution from the tip opening 4A of the dropping nozzle 4.

  As shown in FIG. 1, the overflow device 5 is provided at the periphery of the liquid surface of the aqueous ammonia solution. In FIG. 1, the overflow device 5 is formed below the opening 2 </ b> A of the storage tank 2 and protruding from the side wall surface of the storage tank 2. The overflow device 5 is formed in a box shape around the storage tank 2.

  Using the ADU particle production apparatus 1 according to the present invention, ammonium heavy uranate particles can be produced as follows.

  First, a uranyl nitrate-containing stock solution is put into a stock solution storage tank (not shown).

  The uranyl nitrate-containing stock solution is prepared by adjusting the viscosity by adding a water-soluble polymer to uranyl nitrate obtained by mixing uranium oxide and nitric acid, and then adding pure water.

  Examples of the uranium oxide include uranium dioxide, uranium trioxide, and triuranium octoxide, and uranium trioxide is particularly preferable.

  Examples of the water-soluble polymer include synthetic polymers such as polyvinyl alcohol, sodium polyacrylate and polyethylene oxide, cellulose polymers such as carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, and ethyl cellulose, starch-based polymers such as soluble starch, and carboxymethyl starch. And water-soluble natural polymers such as dextrin and galactan.

  One of these various water-soluble polymers may be used alone, or two or more thereof may be used in combination. Among these, the synthetic polymer is preferable as the water-soluble polymer, and polyvinyl alcohol is particularly preferable.

  First, a predetermined concentration and a predetermined amount of aqueous ammonia solution are stored in the storage tank 2. At this time, the aqueous ammonia solution is stored up to the opening 2 </ b> A of the storage tank 2. Next, a predetermined uranyl nitrate-containing stock solution is circulated through the dropping nozzle 4, and a droplet of the uranyl nitrate-containing stock solution is dropped from the dropping nozzle 4 into the aqueous ammonia solution in the storage tank 2.

  Each droplet dropped in the aqueous ammonia solution floats in the aqueous ammonia solution in the storage tank 2, and absorbs ammonia from the aqueous ammonia solution. Each droplet is gelled not only on the surface but also on the inside, and the reaction proceeds to ADU particles.

  Here, the uranyl nitrate-containing stock solution dropped from the tip opening 4A of the dropping nozzle 4 is landed on the surface of the aqueous ammonia solution. A droplet of the uranyl nitrate-containing stock solution that has reached the liquid level reacts with ammonia to generate gel-like ADU particles. The liquid level of the aqueous ammonia solution in the storage tank 2 rises by the volume of the generated ADU particles. The amount of the ammonia aqueous solution that has risen overflows to the peripheral surface of the ammonia aqueous solution, specifically, the overflow device 5 provided below the opening 2A.

  Therefore, the liquid level of the aqueous ammonia solution is maintained at a constant height, specifically, the height of the opening 2A. By keeping the liquid level constant, the distance between the tip opening 4A of the dropping nozzle 4 used and the liquid level of the aqueous ammonia solution can be made constant. By making this distance constant, the conditions for dropping droplets can be kept constant, so that it is possible to produce ammonium heavy uranate particles with good sphericity.

  The ADU particles discharged from the storage tank 2 and separated from the aqueous ammonia solution are dried, and then are baked, reduced, and sintered under predetermined conditions to become uranium dioxide particles.

  The ADU particle production apparatus according to the present invention is not limited to the apparatus shown in FIG. 1, and the design can be changed as appropriate as long as the object of the present invention can be achieved.

  For example, as shown in FIG. 2, an ADU particle manufacturing apparatus 11 as a modification of the ADU particle manufacturing apparatus according to the present invention includes a storage tank 12, a dropping device 3, and an overflow device 15. In addition, in this ADU particle manufacturing apparatus 11, about the same member or component in above-mentioned ADU particle manufacturing apparatus 1, description is abbreviate | omitted using the same code | symbol.

  As shown in FIG. 2, the storage tank 12 stores an aqueous ammonia solution. The storage tank 12 may be a tank having heat resistance and corrosion resistance. There is no restriction | limiting in particular in the shape of the storage tank 12, What is necessary is just to be formed in the cylinder shape which has cylindrical shape or polygonal shape. The storage tank 12 has an opening 12A at the top thereof. Moreover, the storage tank 12 has the overflow port 12B in the position higher than the overflow apparatus 15 mentioned later. The overflow port 12 </ b> B is formed on the side wall surface of the storage tank 12. The shape of the overflow port 12B is not particularly limited, and may be a polygonal shape or a circular shape in addition to a rectangular shape. Further, the size of the overflow port 12B only needs to be large enough to overflow the aqueous ammonia solution as the liquid level rises.

  Further, as shown in FIG. 2, the overflow device 15 is provided at the liquid surface periphery of the aqueous ammonia solution. In FIG. 2, the overflow device 15 is formed below the overflow port 12 </ b> B of the storage tank 2 and protruding from the side wall surface of the storage tank 2. The overflow device 15 is formed in a box shape around the storage tank 12.

  Using the ADU particle production apparatus 11 according to the present invention, ammonium heavy uranate particles can be produced as follows. When the ADU particle manufacturing apparatus 11 is used, the same dropping conditions and dropping operations as those when the ADU particle manufacturing apparatus 1 is used to manufacture ADU particles are performed.

  First, a predetermined concentration and a predetermined amount of aqueous ammonia solution are stored in the storage tank 2. At this time, the aqueous ammonia solution is stored up to the overflow port 12 </ b> B of the storage tank 2. Next, a predetermined uranyl nitrate-containing stock solution is circulated through the dropping nozzle 4, and a droplet of the uranyl nitrate-containing stock solution is dropped from the dropping nozzle 4 into the aqueous ammonia solution in the storage tank 12.

  Here, the uranyl nitrate-containing stock solution dropped from the tip opening 4A of the dropping nozzle 4 is landed on the surface of the aqueous ammonia solution. A droplet of the uranyl nitrate-containing stock solution that has reached the liquid level reacts with ammonia to generate gel-like ADU particles. The liquid level of the aqueous ammonia solution in the storage tank 12 rises by the volume of the generated ADU particles. The amount of the ammonia aqueous solution that has risen overflows from the peripheral surface of the ammonia aqueous solution, specifically, from the overflow port 12B to the overflow device 15 provided below.

  Therefore, the liquid level of the aqueous ammonia solution is kept at a constant height, specifically, the height of the overflow port 12B. By keeping the liquid level constant, the distance between the tip opening 4A of the dropping nozzle 4 used and the liquid level of the aqueous ammonia solution can be made constant. By making this distance constant, the conditions for dropping droplets can be kept constant, so that it is possible to produce ammonium heavy uranate particles with good sphericity.

  The ADU particles discharged from the storage tank 12 and separated from the aqueous ammonia solution are dried, and then are baked, reduced, and sintered under predetermined conditions to become uranium dioxide particles.

FIG. 1 is a schematic view showing an embodiment of an apparatus for producing ammonium heavy uranate particles according to the present invention. FIG. 2 is a schematic diagram showing a modification of the ammonium biuranium particle production apparatus according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ADU particle manufacturing apparatus 2 Storage tank 2A Opening part 3 Dripping apparatus 4 Dripping nozzle 4A Tip opening part 5 Overflow apparatus 6 Stock solution supply path 11 ADU particle manufacturing apparatus 12 Reservoir tank 12A Opening part 12B Overflow port 15 Overflow apparatus

Claims (1)

A storage tank for storing an aqueous ammonia solution, a dropping device that is disposed above the storage tank and has a dropping nozzle capable of dropping a uranyl nitrate-containing stock solution, and an overflow device provided at the liquid surface periphery of the aqueous ammonia solution An apparatus for producing ammonium heavy uranate particles.

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