JP4331121B2 - Ammonium uranate particle production equipment - Google Patents

Description

  The present invention relates to an ammonium heavy uranate particle manufacturing apparatus, and more particularly to an ammonium heavy uranate particle manufacturing apparatus capable of manufacturing ammonium uranate ammonium particles having good sphericity.

  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 to a viscosity, and then dropped into an aqueous ammonia solution using a small-diameter dropping nozzle.

  The droplets dropped onto 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 composed of graphite powder, a 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, when the size of the storage facility that stores uranium having a concentration of 10% or less is a cylindrical shape, the diameter of the storage facility is 19.8 cm or less, and the shape of the storage facility is a flat plate. In this case, the thickness of the flat plate is 8.3 cm or less.

  The size of the storage facility for storing uranium with a concentration of 20% or less is 17.4 cm or less in the diameter of the cylinder when the shape of the storage facility is a cylindrical shape, and the shape of the storage facility is a flat plate shape. In this case, 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, since the ADU particles are accumulated on the upper side of the generated ADU particles, the lower ADU particles are deformed. Therefore, there is a problem that the sphericity of ADU particles is deteriorated.

  Moreover, when the prepared uranyl nitrate-containing stock solution is dropped into an aqueous ammonia solution stored in a thin disk-shaped reaction chamber, the distance that the droplet of the uranyl nitrate-containing stock solution passes from the liquid surface of the aqueous ammonia solution to the bottom of the reaction chamber In addition, it is not possible to obtain particles that are made of ammonium deuterated uranate from the short to the inside. In addition, the surface is composed of ammonium deuterated uranate but the core remains uranyl nitrate. There is a problem that particles that are not formed are piled up to obtain particles with good sphericity.

  The present invention eliminates such conventional problems, can handle highly enriched uranium as a raw material, and can produce ammonium heavy uranate particles having good sphericity. It is an object of the present invention to provide a particle manufacturing apparatus.

As means for solving the problems,
Claim 1 comprises a dropping device for dropping a uranyl nitrate-containing stock solution containing uranyl nitrate, and a reaction vessel that rotates around a central axis and that can contain an aqueous ammonia solution and has a circular internal planar shape. It is an ammonium heavy uranate particle production apparatus characterized by:
A second aspect of the present invention is the apparatus for producing ammonium deuterated uranium particles according to claim 1, wherein the dropping position of the uranyl nitrate-containing stock solution is a region including the central axis.
3. The ammonium heavy uranate particles according to claim 1, wherein a plate-like member containing a neutron absorbing material is provided at an upper part and a lower part of the reaction tank. Manufacturing equipment,
Claim 4 is the ammonium heavy uranate particle production apparatus according to any one of claims 1 to 3, wherein the rotational speed of the reaction vessel is variable,
A fifth aspect of the present invention is the ammonium heavy uranate particle producing apparatus according to any one of the first to fourth aspects, wherein the reaction vessel is formed so as to have a shape restriction.

  According to the present invention, the reaction is performed by providing a reaction tank that rotates around the central axis and can contain an aqueous ammonia solution that reacts with the dripping uranyl nitrate-containing stock solution and has a circular inner plane shape. As the tank rotates, the aqueous ammonia solution itself also forms a rotating flow. The rotating flow causes the ammonium heavy uranate particles generated in the aqueous ammonia solution to circulate and the ammonium heavy uranate particles are less likely to overlap each other, so that the ammonium heavy uranate particles are less likely to be deformed. Therefore, it is possible to produce ammonium biuranate particles having good sphericity.

  Furthermore, according to the present invention, the dropping position of the uranyl nitrate-containing stock solution is a region including the central axis. Here, since the droplet of the uranyl nitrate-containing stock solution has a specific gravity smaller than the ammonium heavy uranate particles generated in the aqueous ammonia solution, the droplet of the uranyl nitrate-containing stock solution dropped when the reaction vessel was rotated. Although initially gathered near the central axis, the droplets move while circulating around the peripheral wall of the reaction tank by centrifugal force in the ammonia aqueous solution rotating with the rotation of the reaction tank. While moving around the aqueous ammonia solution, uranyl nitrate in the droplets changes to ammonium deuterated uranate. As a result, it is possible to produce ammonium heavy uranate particles having a good sphericity and having become ammonium heavy uranate to the core.

  Further, according to the present invention, the upper and lower portions of the reaction vessel are provided with plate-like members containing a neutron absorbing material, so that neutrons or the like that cause a critical state are introduced into the reaction vessel main body. Invasion can be prevented, and ammonium heavy uranate particles can be produced safely.

  Furthermore, according to the present invention, the rotation speed of the reaction vessel is variable, and the rotation speed is changed according to the amount of particles in the reaction vessel. That is, when the number of particles is small, the rotation speed is decreased, and when the dropping proceeds and the number of particles increases, the rotation speed is increased. In addition, since the height (thickness) of the reaction vessel is determined so that the shape of the reaction vessel is limited, according to the present invention, the radial dimension of the reaction vessel main body itself can be formed large, and therefore “mass restriction” Compared with the production method according to the method, it is possible to produce a large amount of ammonium uranate particles at a time.

  Hereinafter, an ammonium heavy uranate particle manufacturing apparatus (hereinafter, also referred to as “ADU particle manufacturing apparatus”) according to an embodiment of the present invention will be described with reference to FIG. However, the ADU particle manufacturing apparatus illustrated in FIG. 1 is an example of the present invention, and the ADU particle manufacturing apparatus according to the present invention is not limited to the ADU particle manufacturing apparatus illustrated in FIG.

  The ADU particle manufacturing apparatus 1 includes a reaction tank 2 and a dropping device 3.

  The reaction tank 2 has an internal space for storing the aqueous ammonia solution 13, that is, an internal storage chamber. The internal storage chamber has a circular planar shape, and more specifically, a circular bottom surface 5, an inner peripheral surface 6, and a central portion. It is formed with the ceiling part 7 provided with the dripping opening part 4. FIG. The reaction tank 2 is formed by the rotating means 8 so as to be rotatable in a horizontal plane around the central axis.

  The internal space of the internal storage chamber in the reaction tank 2 is usually formed in a disk shape having a circular bottom surface 5. In the disk-shaped internal space, the passing length in the diametric direction is usually set larger than the axial length (which can also be regarded as height). When the internal storage chamber in the reaction tank 2 is disc-shaped, when the reaction tank 2 is rotated in a horizontal plane, the aqueous ammonia solution 13 itself is also rotated in the horizontal plane due to the viscosity of the aqueous ammonia solution 13 in contact with the bottom surface, the inner peripheral surface and the ceiling surface. To do.

  A suitable rotation speed in the horizontal plane of the reaction tank 2 differs depending on the scale of the reaction tank 2 and cannot be determined uniquely, but a rotation angle of 45 to 180 degrees / second is suitable. Further, the rotation speed is preferably changed according to the amount of particles in the reaction vessel 2. That is, when the number of particles is small, the rotation speed is decreased, and when the dropping proceeds and the number of particles increases, the rotation speed is increased.

  When the reaction chamber 2 has an internal storage chamber formed in a disk shape, in order to limit the shape of the internal storage chamber, a disk having an axial height of 8.3 cm is used for a solution of uranium having a concentration of 10%. As for a solution having a uranium concentration with a concentration of 20%, a disk shape having an axial height of 6.7 cm can be mentioned. In general, the disk-shaped internal storage chamber whose shape is limited tends to have a lower axial line height as the uranium concentration increases.

  Various means can be adopted as the rotation means 8 as long as the reaction tank 2 can be rotated around the central axis in a horizontal plane. For example, as the rotating means 8, (1) a gear formed on the outer periphery of the reaction tank 2 so as to go around the outer periphery, a speed reducer meshing with the gear, and a rotation for transmitting a rotational force to the speed reducer Rotating means comprising a drive source such as a motor, (2) a rotating shaft formed so as to protrude from the center of the bottom of the reaction tank 2, power transmitting means such as a belt and a chain for transmitting power to the rotating shaft, A rotational drive source for supplying rotational force to the transmission means, for example, a rotational means composed of a motor or the like, in short, includes a rotational force transmission means for transmitting rotational force to the reaction tank 2, a speed reduction means, a rotational drive source, and the like.

  A plate-like member 9 including a neutron absorbing material is provided on the upper surface and the lower surface of the internal storage chamber in the reaction tank 2. Here, the substance constituting the neutron absorber may contain boron, cadmium, xenon, gadolinium, hafnium, or the like. In the present invention, “upper surface” and “lower surface” of the reaction tank 2 indicate an upper position and a lower position with respect to the internal storage chamber.

  In the present invention, as long as the plate member is installed, a member formed of a neutron absorbing material is disposed above and below the reaction tank 2, and a specific example of this embodiment is, for example, (1) internal A plate-like member made of neutron absorbing material is installed on the ceiling surface 7 of the containing chamber so as to cover the entire ceiling surface, and a plate-like member made of neutron absorbing material covers the whole bottom surface 5 of the inner containing chamber. (2) on the outer surface of the lid member of the reaction tank formed by, for example, a bottomed cylindrical body and a lid member that can cover the upper opening and has a dripping opening at the center. A plate-like member made of neutron absorber is installed so as to cover this, and a plate-like member made of neutron absorber is installed so as to cover the bottom side surface of the bottomed cylindrical body. (3) in a member constituting the upper surface portion of the disc-shaped reaction tank body A plate member made of neutron absorbing material is embedded so that it is not exposed to the outside, and the plate member made of neutron absorbing material is embedded in the member constituting the lower surface portion of the reaction vessel body so as not to be exposed to the outside. An embodiment of embedding can be mentioned.

  The dropping device 3 is formed so that a uranyl nitrate-containing stock solution containing uranyl nitrate can be dropped into the aqueous ammonia solution 13 in the reaction tank 2 through the dropping opening 4 in the reaction tank 2. The dropping device 3 shown in FIG. 1 has a cylindrical case 10 installed in the dropping opening 4 of the reaction tank 2 and is installed in the upper part of the cylindrical case 10. Ammonia gas is introduced into the cylindrical case 10 from its lower part, and ammonia gas is led out from its upper part.

  The dripping device 3 includes a plurality of, for example, four dripping nozzles (not shown) and a vibrator that vibrates the dripping nozzles in the vertical direction and / or the horizontal direction, and is stored in the storage tank 11. The uranyl nitrate-containing stock solution is supplied to the dropping nozzle, and the droplet of the uranyl nitrate-containing stock solution can be dropped into the cylindrical case 10 from the dropping nozzle while vibrating the dropping nozzle.

  The usage method and operation of the above ADU particle production apparatus will be described below. The uranyl nitrate-containing stock solution used when producing ADU particles with the ADU particle production apparatus of the present invention is obtained by adding a water-soluble polymer to uranyl nitrate obtained by mixing uranium oxide and nitric acid, and then adding pure water. It is prepared by adjusting the viscosity by adding.

  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 13 are stored in the reaction tank 2. Next, a predetermined uranyl nitrate-containing stock solution is circulated through the dropping device 3, and a droplet 12 of the uranyl nitrate-containing stock solution is dropped from the dropping device 3.

  Ammonia gas is sprayed in the cylindrical case 10 to each dropped droplet. Then, a reaction in which uranyl nitrate changes to ammonium heavy uranate proceeds from the surface of the droplet falling in the cylindrical case 10, and as a result, a film or shell made of ammonium heavy uranate is formed on the surface of the droplet. The Even if a droplet having such a coating or shell made of ammonium heavy uranate falls and collides with the liquid surface of the aqueous ammonia solution 13, the droplet is prevented from being deformed or ruptured by impact.

  Each droplet falls into an aqueous ammonia solution 13 accommodated in the reaction tank 2. Since the reaction tank 2 rotates in the horizontal plane around its central axis, the ammonia aqueous solution 13 in the reaction tank 2 also rotates in the horizontal plane due to the viscosity of the ammonia aqueous solution 13. Here, since the droplet of the uranyl nitrate-containing stock solution has a specific gravity smaller than that of the ammonium heavy uranate particles generated in the aqueous ammonia solution 13, the droplet is once near the central axis of the rotating reaction tank 2. get together. However, when the specific gravity of the droplet immediately after dropping into the aqueous ammonia solution 13 is increased due to an increase in the amount of ammonium heavy uranate produced in the dropping droplet by the ammonia gas sprayed in the cylindrical case 10. In the ammonia aqueous solution 13 rotating in the horizontal plane, a droplet having a large specific gravity may move from the center to the outside.

  When the reaction of converting uranyl nitrate into ammonium heavy uranate proceeds in the droplets that have gathered near the center of the reaction tank 2, and the specific gravity of the droplets is increased thereby, the droplets are rotated with the aqueous ammonia solution 13. It moves from the central part to the peripheral wall by drawing an arc due to the centrifugal force. Even during this movement, a reaction that changes from uranyl nitrate to ammonium heavy uranate proceeds in the droplet.

  A droplet submerged in the rotating aqueous ammonia solution 13 moves in the aqueous ammonia solution 13 as the aqueous ammonia solution 13 rotates. During movement, the reaction proceeds from uranyl nitrate to ammonium deuterated uranate in the droplet.

  And when the reaction tank 2 rotates, the produced | generated heavy ammonium uranate particle will gather on the outer peripheral side of the reaction tank 2 with a centrifugal force. Therefore, as described above, by dropping the uranyl nitrate-containing stock solution, ammonium heavy uranate particles can be efficiently generated.

  After a predetermined time, the reaction proceeds, and ADU particles precipitated in the lower part of the reaction tank 2 are discharged to the outside of the reaction tank 2 from an outlet of the reaction tank 2 (not shown).

  The ADU particles discharged to the outside of the reaction tank 2 are dried, and then are baked, reduced, and sintered under predetermined conditions to become uranium dioxide particles.

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications and improvements within a scope that can achieve the object of the present invention are included in the present invention.

FIG. 1 is a schematic view showing an apparatus for producing ammonium heavy uranate particles according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ADU particle manufacturing apparatus 2 Reaction tank 3 Dropping apparatus 4 Dropping opening part 5 Bottom face 6 Inner peripheral surface 7 Ceiling surface 8 Rotating means 9 Plate member 10 Cylindrical case 11 Reservoir 12 Droplet 13 Aqueous ammonia solution

Claims (5)

  A dripping device for dripping a uranyl nitrate-containing stock solution containing uranyl nitrate, and a reaction vessel that rotates around a central axis and that can contain an aqueous ammonia solution and has a circular inner plane shape. An ammonium heavy uranate particle manufacturing apparatus.   The apparatus for producing ammonium heavy uranate particles according to claim 1, wherein the dropping position of the uranyl nitrate-containing stock solution is a region including the central axis.   The apparatus for producing ammonium deuterated uranium particles according to claim 1 or 2, wherein a plate-like member containing a neutron absorbing material is provided at an upper part and a lower part of the reaction tank.   The apparatus for producing ammonium heavy uranate particles according to any one of claims 1 to 3, wherein a rotational speed of the reaction vessel is variable. The apparatus for producing ammonium heavy uranate particles according to any one of claims 1 to 4, wherein the reaction tank is formed so as to have a shape restriction.

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