JP2006225233A - Apparatus for manufacturing ammonium diuranate particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for manufacturing an ammonium diuranate particle which can manufacture an ammonium diuranate particle having high sphericity from a high concentration uranium raw material. <P>SOLUTION: The apparatus for manufacturing an ammonium diuranate particle has: a dropping nozzle for dropping a uranyl nitrate-containing stock solution containing uranyl nitrate in high concentration into an ammonia aqueous solution; a reaction vessel of a criticality-safe geometry, storing the ammonia aqueous solution and provided with a slope part for discharging particles present in the ammonia aqueous solution; and a wave generator provided at a position opposed to the slope part and for generating wave advancing toward the slope part in the ammonia aqueous solution. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for producing ammonium heavy uranate particles.

  According to Non-Patent Documents 1 to 5, HTGR fuel is generally manufactured through the following steps. First, uranium oxide powder is dissolved in nitric acid to form a uranyl nitrate solution. Next, pure water, a thickener and the like are added to the uranyl nitrate solution and stirred to obtain a uranyl nitrate-containing stock solution. The prepared uranyl nitrate-containing stock solution is cooled to a predetermined temperature, adjusted in viscosity, and then dropped into an aqueous ammonia solution using a small-diameter dropping nozzle.

  The droplets dropped on the aqueous ammonia solution are sprayed with ammonia gas before reaching the surface of the aqueous ammonia solution. The surface of the droplet is gelled by the ammonia gas, thereby preventing deformation when reaching the surface of the aqueous ammonia solution. Uranyl nitrate in the aqueous ammonia solution sufficiently reacts with ammonia to form ammonium heavy uranate particles (hereinafter sometimes abbreviated as “ADU particles”).

  The ammonium deuterated uranium particles are dried and then roasted in the atmosphere to contain more oxygen than uranium dioxide, resulting in uranium oxide having an oxygen: uranium molar ratio greater than 2, eg, uranium trioxide, Reduction and sintering result in high-density ceramic-like uranium dioxide particles. The uranium dioxide particles are sieved, that is, classified to obtain fuel nuclei having a predetermined particle size.

The fuel nuclei are loaded onto a fluidized bed, and coating is performed by thermally decomposing the coating gas. The coating layer is formed by coating the first layer, the second layer, the third layer, and the fourth layer from the fuel core surface. In the case of the first layer of low density carbon, it is obtained by pyrolyzing acetylene (C ₂ H ₂ ) at about 1400 ° C. In the case of the high density pyrolytic carbon of the second layer and the fourth layer, it is obtained by pyrolyzing propylene (C ₃ H ₆ ) at about 1400 ° C. In the case of SiC of the third layer, it is obtained by thermally decomposing methyltrichlorosilane (CH ₃ SiCl ₃ ) at about 1600 ° C.

  In general fuel compacts, the coated fuel particles obtained as described above are pressed or molded into a hollow cylindrical shape or cylindrical shape together with a graphite matrix material made of graphite powder, binder, etc., and then fired. Obtained.

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

  On the other hand, when manufacturing nuclear fuel using nuclear fuel materials such as uranium, as a method to prevent criticality accidents, in general, the "mass limit" that the amount of uranium handled is less than the critical mass, and the amount of uranium is Regardless of the shape and dimensions that do not cause criticality, the “shape restriction” handles uranium.

  In the case of “mass restriction”, the maximum handling amount for uranium having a concentration of 10% or less is 9.6 kg, and the maximum handling amount for uranium having a concentration of 20% or less is 4.0 kg. Therefore, the batch size in each manufacturing process needs to be below these values. Further, from the viewpoint of safety, considering the case of double loading by mistake, the batch size in each manufacturing process needs to be 1/2 or less of these values. Therefore, the productivity of nuclear fuel deteriorates and it cannot be said that it is suitable as a criticality management method for mass production facilities.

  On the other hand, in the case of “shape restriction”, the size defined by the enrichment and shape of uranium varies. For example, the size of the storage facility for uranium with a concentration of 10% or less, when the storage facility is cylindrical, the diameter of the cylinder is 19.8 cm or less, and the storage facility is flat, The thickness of the flat plate is 8.3 cm or less.

  In addition, the size of the storage facility for uranium with a concentration of 20% or less is when the shape of the storage facility is a cylindrical shape, the diameter of the cylinder is 17.4 cm or less, and the shape of the storage facility is a flat plate shape, The thickness of the flat plate is 6.7 cm or less.

  Since there is no limit to the amount of uranium handled in these storage facilities, “shape limitation” is preferable as a criticality management method for mass production facilities. However, as described above, since the dimensional limit value in the “shape limit” becomes smaller as the uranium becomes highly enriched, the facility for manufacturing the fuel core must be an elongated cylindrical shape or a thin flat plate shape. Absent.

  For example, in the step of dropping the prepared uranyl nitrate-containing stock solution into an aqueous ammonia solution, ammonia and uranyl nitrate sufficiently react in the aqueous ammonia solution to generate ADU particles. Here, the generated ADU particles are deformed because the ADU particles are stacked on the upper side. Therefore, there is a problem that the sphericity of ADU particles is deteriorated.

  In order to solve the problem that the sphericity of the ADU particles is deteriorated, the ADU particles are caused to flow in the aqueous ammonia solution by generating a circulating flow in the aqueous ammonia solution so that the ADU particles do not overlap each other. Techniques for doing so have been proposed.

  However, when high concentration uranium is used as a raw material, the storage equipment must be in the shape of an elongated cylinder or a thin flat plate. It cannot be flowed. Therefore, the problem that the sphericity deteriorates due to the deformation of the ADU particles has not been solved.

  In addition, the conventional production of ammonium heavy uranate particles has been performed in a batch system. An ADU particle production apparatus capable of continuous operation has not been developed, and it has been difficult to mass-produce ADU particles.

  In order to solve the above problems, an object of the present invention is to provide an apparatus for producing ammonium heavy uranate particles capable of producing ADU particles having high sphericity from a high concentration uranium raw material.

  Means for solving the problems of the present invention are a dropping nozzle for dropping a uranyl nitrate-containing stock solution containing uranyl nitrate at a high concentration into an aqueous ammonia solution, storing the aqueous ammonia solution, and existing in the aqueous ammonia solution. A critically safe reaction tank comprising an inclined portion for discharging particles, and a wave generator that is provided at a position facing the inclined portion and generates a wave traveling in the inclined portion in the aqueous ammonia solution. An ammonium heavy uranate particle producing apparatus characterized by

  The apparatus for producing ammonium heavy uranate particles of the present invention can produce ADU particles with high sphericity from a high concentration of uranium raw material. By providing a wave maker, droplets are moved up and down in an aqueous ammonia solution. The droplet descends in the aqueous ammonia solution while repeating vertical movement and eventually reaches the bottom of the reaction vessel. Therefore, the contact time between the droplet and the aqueous ammonia solution can be increased until the droplet reaches the bottom surface of the reaction vessel, and uranyl nitrate and ammonia can be sufficiently reacted. By providing the inclined portion on the bottom surface of the reaction tank, the amount of the aqueous ammonia solution in the reaction tank can be kept constant.

  Hereinafter, the ammonium heavy uranate particle production apparatus of the present invention (hereinafter sometimes referred to as “ADU particle production apparatus”) will be described with reference to the drawings.

  The ADU particle production apparatus of the present invention is shown in FIG. In addition, the ADU particle manufacturing apparatus of this invention is not restricted to what is shown by FIG.

  The ADU particle manufacturing apparatus 1 shown in FIG. 1 includes a reaction tank 2, a dropping nozzle 3, a wave generator 4, and an aqueous ammonia solution supply unit 5.

  The reaction tank 2 stores an aqueous ammonia solution. A stock solution containing uranyl nitrate is dropped into the aqueous ammonia solution from a dropping nozzle 3 disposed above the reaction tank 2. Ammonia and uranyl nitrate react in the aqueous ammonia solution, and ammonium heavy uranate is gradually formed from the surface of the droplet b dropped into the aqueous ammonia solution toward the inside. The droplet b becomes ADU particles a.

  The reaction tank 2 may be a tank having heat resistance and corrosion resistance, and has a rectangular vertical cross section. The depth dimension of the reaction tank 2 is small, an inclined part 6 is provided on the bottom surface of the reaction tank 2, and a discharge path 7 is provided so as to be continuous with the inclined part 6.

  The reaction tank 2 maintains a critical safety shape by reducing its depth dimension. The depth dimension should be 8.3 cm or less when handling uranium with a concentration of 10% or less, and 6.7 cm or less when handling uranium with a concentration of 20% or less.

  Since the reaction tank 2 has the inclined portion 6, the ADU particles a formed in the aqueous ammonia solution can be easily discharged out of the reaction tank 2 along with the wave of the aqueous ammonia solution and flows out of the reaction tank 2. Since the aqueous ammonia solution is supplied from the aqueous ammonia solution supply unit 5, the amount of the aqueous ammonia solution in the reaction tank 2 can be kept constant.

  In the ADU particle production apparatus 1 shown in FIG. 1, the upper part of the reaction tank 2 is open, but it may be a sealed reaction tank in which only the part corresponding to the place where the dropping nozzle 3 is arranged is opened. .

  The inclination angle θ of the inclined surface 6a in the inclined portion 6 is preferably 5 to 30 degrees. In addition, the height of the apex of the inclined portion 6 with respect to the bottom surface of the reaction tank 2 is less than the dimension limit value determined from the shape limit, and the height necessary for discharging particles out of the reaction tank 2 is considered, for example, 1 cm. And must be determined.

  The dripping nozzle 3 is disposed above the reaction tank 2. One end opening of the dropping nozzle 3 is disposed so as to face the surface of the aqueous ammonia solution stored in the reaction tank 2. The other end opening is connected to a stock solution supply path (not shown), and the stock solution supply path is connected to a stock solution storage tank (not shown). The uranyl nitrate-containing stock solution stored in the stock solution storage tank reaches the dropping nozzle 3 through the stock solution supply path, and is dropped into the aqueous ammonia solution from one end opening of the dropping nozzle 3.

  Although there is no restriction | limiting in particular as a shape and a magnitude | size of the said dripping nozzle 3, Usually, a nozzle with a circular cross section is used. When the cross section of the dropping nozzle 3 is circular, the inner diameter is preferably 0.2 to 3 mm.

  Moreover, the dripping nozzle 3 may be one or plural. When dropping the uranyl nitrate-containing stock solution, a vibrator (not shown) is attached to the dropping nozzle 3, and the dropping nozzle 3 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

  The wave maker 4 is provided at a position facing the inclined portion 6 of the reaction tank 2, and generates a wave traveling to the inclined portion 6 in the aqueous ammonia solution in the reaction tank 2. The amplitude of the wave generated by the wave maker 4 is preferably 50 to 200 cm, and the frequency is preferably 0.5 to 2 Hz.

  By generating such a wave in the aqueous ammonia solution, the droplet dropped in the aqueous ammonia solution gradually moves to the inclined portion 6 of the reaction tank 2 while moving up and down in the aqueous ammonia solution. That is, the contact time between the aqueous ammonia solution and the droplet b can be increased, the ammonia and uranyl nitrate can be sufficiently reacted to the inside of the droplet b, and the ADU particles a are loaded on the upper side. The problem that the ADU particle a on the lower side is deformed by the weight of the ADU particle a and the sphericity is deteriorated can be solved.

  Further, the aqueous ammonia solution discharged from the discharge path 7 and separated and recovered from the ADU particles a is returned to the inside of the reaction tank 2 by the aqueous ammonia solution supply unit 5.

  Here, the aqueous ammonia solution supply unit 5 is connected to the discharge path 7 and the side of the reaction tank 2 where the wave maker 4 is installed so as to be able to supply liquid. Specifically, the aqueous ammonia solution supply unit 5 includes a supply path 5A and a circulation pump 5B. 5 A of supply paths are piping which connects the discharge path 7 and the side in which the wave maker 4 of the reaction tank 2 was installed. The circulation pump 5B is provided in the middle of the supply path 5A, and supplies the aqueous ammonia solution in the supply path 5A from the discharge path 7 to the side of the reactor 2 where the wave generator 4 is installed.

  In this way, the aqueous ammonia solution of the ADU particle manufacturing apparatus 1 can be used effectively, and the amount of the aqueous ammonia solution discharged from the ADU particle manufacturing apparatus 1 can be reduced, thus reducing the burden on the environment. be able to.

  Further, the aqueous ammonia solution supply unit 5 may be provided via an aqueous ammonia solution storage tank (not shown) for storing the aqueous ammonia solution.

  In this way, when the aqueous ammonia solution discharged from the discharge path 7 and separated and recovered from the ADU particles a is returned to the inside of the reaction tank 2 by the aqueous ammonia solution supply unit 5, the aqueous ammonia solution storage tank (FIG. (Not shown), the concentration of the aqueous ammonia solution can be adjusted. Then, the aqueous ammonia solution diluted by the reaction in the reaction tank 2 can be introduced into the reaction tank 2 from the supply path 5A at a predetermined concentration, so that the amount corresponding to the amount of ammonia consumed by the reaction is compensated. This is convenient because the ammonia aqueous solution concentration in the reaction tank 2 can be kept constant.

  The ADU particles a and the aqueous ammonia solution discharged from the discharge path 7 are collected separately. The separately collected ADU particles a become fuel nuclei through a drying process, a roasting process, and a sintering process.

  Using the ADU particle production apparatus 1 of the present invention, ADU particles a can be produced as follows.

  The stock solution containing uranyl nitrate is put into the stock solution storage tank.

  The uranyl nitrate 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 polyvinyl alcohol (hereinafter abbreviated as PVA), synthetic polymers such as sodium polyacrylate and polyethylene oxide, cellulose polymers such as carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, and ethyl cellulose, soluble starch, And starch-based polymers such as carboxymethyl starch, 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 reaction tank 2. Then, the wave maker 4 is operated to cause the ammonia aqueous solution in the reaction tank 2 to flow in the direction of the inclined portion 6. Next, a predetermined uranyl nitrate-containing stock solution is circulated through the dropping nozzle 3, and a droplet b of the uranyl nitrate-containing stock solution is dropped from the dropping nozzle 3 into the aqueous ammonia solution in the reaction tank 2.

  In addition, although illustration is abbreviate | omitted, you may make it spray ammonia gas suitably with respect to each dropped droplet b. In this way, gelation proceeds on the surface of the droplet b, and deformation of the droplet b when colliding with the ammonia aqueous solution surface can be suppressed.

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

  The ADU particles a discharged from the reaction vessel 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 1 in the present invention is not limited to the apparatus shown in FIG. 1, and can be appropriately changed in design within a range in which the object of the present invention can be achieved.

FIG. 1 is a diagram showing an embodiment of an apparatus for producing ammonium heavy uranate particles in the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ADU particle manufacturing apparatus 2 Reaction tank 3 Dripping nozzle 4 Wave generator 5 Ammonia aqueous solution supply part 5A Supply path 5B Circulation pump 6 Inclination part 6a Inclination 7 Discharge path a ADU particle b Droplet

Claims (1)

A critically safe shape comprising a dropping nozzle for dropping a uranyl nitrate-containing stock solution containing uranyl nitrate at a high concentration into an aqueous ammonia solution, and an inclined portion for storing the aqueous ammonia solution and discharging particles present in the aqueous ammonia solution. And a wave generator that is provided at a position facing the inclined portion and generates a wave that travels to the inclined portion in the aqueous ammonia solution.

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