JP2007084375A - Dissolving and mixing tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dissolving and mixing tank with which a raw liquid containing uranyl nitrate can be easily prepared. <P>SOLUTION: The dissolving and mixing tank comprises a rotary shaft whose axis line is directed in a substantially horizontal direction and a dissolving and mixing tank main body which is formed so as to be rotated together with the rotary shaft and whose cross section orthogonal to the horizontal direction is a polygonal shape. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a dissolution and mixing tank, and more particularly to a dissolution and mixing tank in which a uranyl nitrate-containing stock solution can be easily prepared.

  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 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 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 makes the amount of uranium handled less than the critical mass, Regardless of the shape and dimensions that do not cause criticality, the “shape restriction” for handling uranium is raised.

  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 manufacturing equipment for uranium with a concentration of 10% or less is a cylindrical shape, the diameter of the cylinder is 19.8 cm or less, and the shape of the manufacturing equipment is a flat plate, The thickness of the flat plate is 8.3 cm or less.

  In addition, when the size of the manufacturing equipment for uranium with a concentration of 20% or less is a cylindrical shape, the diameter of the cylinder is 17.4 cm or less, and the shape of the manufacturing equipment is a flat plate, 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 production 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 dissolving uranium oxide in nitric acid, rotary stirring is performed with a propeller or the like in order to dissolve uranium oxide which is difficult to dissolve by so-called “mass restriction”. Further, in the case of so-called “shape restriction”, the equipment to be housed is an elongated cylindrical shape or a thin flat plate shape. As a result, undissolved uranium oxide is generated, a solution having a predetermined concentration cannot be obtained, causing internal defects, and in turn causing variations in the quality of fuel nuclei.

  Also, in the process of adding pure water or a thickener to the prepared uranyl nitrate-containing stock solution, stirring, and producing a stock solution dropped into an aqueous ammonia solution, in the case of so-called “shape restriction”, the equipment to be stored is elongated. Since it becomes a cylindrical shape or a thin flat plate shape, the stirring effect by a propeller or the like is limited to a part of the region. Therefore, uranyl nitrate, pure water, and a thickener are not uniformly mixed, and as a result, there is a problem that the concentration and viscosity of the dripping stock solution are not uniform.

  If the concentration and viscosity of the dripping stock solution are not uniform, there is a problem that it is difficult to make the particle size and density uniform when dropping into an aqueous ammonia solution to produce ammonium deuterated uranate particles. As a result, there are problems that the particle diameters of the fuel nuclei are varied, the density of the fuel nuclei after sintering is varied, and defects are generated inside the fuel nuclei.

  An object of the present invention is to solve such conventional problems and to provide a dissolution and mixing tank capable of easily preparing a uranyl nitrate-containing stock solution.

As means for solving the above-mentioned problems,
The first aspect of the present invention is a dissolution and mixing tank that is formed so as to be able to rotate together with a rotating shaft body whose axis is oriented substantially in the horizontal direction and the rotating shaft body, and has a polygonal cross-sectional shape perpendicular to the horizontal direction. A dissolution mixing tank characterized by comprising a main body,
According to a second aspect of the present invention, the rotating shaft body includes a supply path for supplying the raw material into the dissolution and mixing tank body and a discharge path for discharging the contents in the dissolution and mixing tank body. The dissolution mixing tank according to claim 1,
According to a third aspect of the present invention, the outer peripheral surface of the dissolution and mixing tank main body is provided with temperature adjusting means for adjusting the temperature in the dissolution and mixing tank main body. Dissolution and mixing tank,
According to a fourth aspect of the present invention, a plate-like member including a neutron absorbing material is provided on each of the opposing outer peripheral surfaces of the dissolution and mixing tank main body. The dissolution and mixing tank according to Item 1.

  According to the present invention, the rotating shaft body and the dissolution / mixing tank main body are provided so as to be accommodated in the dissolution / mixing tank main body in a stationary state, for example, uranium oxide, nitric acid, pure water, thickener, etc. The raw material is accumulated on the apex side of the polygonal shape located on the lowermost side of the dissolution and mixing tank main body. Next, together with the rotating shaft body, when the dissolution and mixing tank main body rotates around the axis of the rotating shaft body, the contents accumulated on the inner wall surface are along the inner wall surface on the lower side of the dissolving and mixing tank body. ,Moving. And, as the dissolution and mixing tank main body rotates, the other apex of the polygonal shape comes to be located on the lowest side of the dissolution and mixing tank main body. Therefore, the contents of the dissolution and mixing tank main body exhibit the same action as the stirring action by repeating the above-described operation, so that a uranyl nitrate-containing stock solution can be easily prepared.

  Further, according to the present invention, the rotary shaft body includes a supply path and a discharge path, so that the supply and discharge can be performed while the dissolution and mixing tank main body rotates and operates. Therefore, work efficiency can be improved.

  Further, according to the present invention, the temperature adjusting means is provided on the outer peripheral surface of the dissolution and mixing tank main body, so that, for example, the temperature of the liquid stored in the inside is changed, and the predetermined concentration and viscosity are changed. Solution.

  And according to this invention, since the plate-shaped member which contains a neutron absorber is provided in the outer peripheral surface which the said melt | dissolution mixing tank main body opposes, since the neutron which produces a critical state is absorbed, Thus, the dimension limit value in so-called “shape limitation” can be increased. Accordingly, the size of the dissolution / mixing tank body itself can be formed large, so that productivity can be improved.

  Hereinafter, a dissolution and mixing tank according to an embodiment of the present invention will be described with reference to FIG. The dissolution / mixing tank 2 includes a rotating shaft body 3 and a dissolution / mixing tank body 4.

  The rotary shaft 3 has an axis line oriented in the horizontal direction, and includes a supply path 5 for supplying the raw material into the dissolution and mixing tank body 4 and a discharge path 6 for discharging the contents in the dissolution and mixing tank body 4. Prepare. In the present embodiment, the rotating shaft body 3 has a double tube structure. Here, the inside of the inner pipe forms the supply path 5. A space surrounded by the inner pipe outer wall and the outer pipe inner wall forms a discharge path 6.

  The supply path 5 supplies uranium oxide, nitric acid, water, a thickener, and the like, which are raw materials for the uranyl nitrate-containing stock solution, into the dissolution and mixing tank body 4. The raw material supplied from the supply path 5 into the dissolution and mixing tank main body 4 and the product obtained by the reaction of these raw materials become the contents present in the dissolution and mixing tank main body 4. Moreover, the pump 6A is connected to the discharge path 6, for example. This pump 6A can discharge the contents present in the dissolution and mixing tank main body 4 by suction. In particular, NOx gas generated by the reaction of uranium oxide and nitric acid can be discharged out of the dissolution and mixing tank body 4 from the discharge path 6.

  The dissolution / mixing tank body 4 is formed so as to be rotatable together with the rotating shaft 3, and the cross-sectional shape orthogonal to the horizontal direction is a polygonal shape. In the present embodiment, the cross-sectional shape is a quadrangle. In addition, this cross-sectional shape is good also as polygonal shapes, such as a pentagon, a hexagon, a heptagon, and an octagon other than a rectangle. Among these, since it is easy to manufacture the dissolution and mixing tank main body 4, a quadrangular or octagonal shape is preferable.

  Further, a discharge port 4 </ b> A for discharging the uranyl nitrate-containing stock solution present in the dissolution / mixing tank body 4 is provided on the outer peripheral surface of the dissolution / mixing tank body 4, for example, at a corner portion. The discharge port 4A is formed in a slide type or a hinge type so that it can be opened only when the uranyl nitrate-containing stock solution is discharged. The position where the discharge port 4A is provided is merely an example, and may be provided at another location.

  On the outer peripheral surface of the dissolution / mixing tank body 4, temperature adjusting means 7 for adjusting the temperature in the dissolution / mixing tank body 4 to a predetermined value is provided. Examples of the temperature adjusting means 7 include means comprising a combination of a known electric heater and a thermocouple.

  On the opposing outer peripheral surface side of the dissolution and mixing tank body 4, plate-like members 8 each containing a neutron absorbing material are provided. Here, the substance constituting the neutron absorber may be any substance containing boron, cadmium, xenon, gadolinium, hafnium, or the like.

[Use and action of dissolution and mixing tank]
The use method and operation of the above-described dissolution and mixing tank will be described below. According to the dissolution and mixing tank of the present invention, a uranium nitrate-containing stock solution whose viscosity is adjusted by mixing uranium oxide and nitric acid, optionally adding a water-soluble polymer as a thickener, and then adding pure water. Is prepared.

  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.

  Here, specifically, dissolution and mixing will be described. As shown in FIG. 1, the temperature in the dissolution and mixing tank body 4 is adjusted to a predetermined temperature by the temperature adjusting means 7 in advance. First, uranium oxide and nitric acid are supplied from the supply path 5 into the dissolution and mixing tank main body 4. In the dissolution / mixing tank body 4, as shown in FIG. 2, in a stationary state, the vertex A located on the lowermost side of the dissolution / mixing tank body 4 among the respective vertexes of the quadrangle when viewed from the vertical side surface. The contents accumulate in the mixing dissolution tank main body 4 in a state where the value is lowered.

  Next, as shown in FIG. 3, together with the rotating shaft body 3, the dissolution and mixing tank body 4 rotates about 30 degrees counterclockwise from the state of FIG. The contents move along the inner wall surface in the vicinity of the vertex A located on the lower side of the dissolution and mixing tank main body 4.

  Further, as shown in FIG. 4, together with the rotating shaft body 3, when the dissolution and mixing tank body 4 rotates about the rotating shaft about 45 degrees from the state of FIG. And vertex D comes to be located in the lowermost part. In this case, the contents are accumulated between the vertex A and the vertex D.

  Further, as shown in FIG. 5, when the dissolution and mixing vessel main body 4 together with the rotating shaft body 3 is rotated about the rotating shaft about 90 degrees counterclockwise from the state of FIG. A thing moves along the inner wall surface in the vicinity of the vertex D located on the lower side of the dissolution and mixing tank main body 4, and the contents accumulate in a state where the vertex D is lowered.

  Therefore, this solution exhibits the same action as the stirring action by repeating the above operation, the reaction between nitric acid and uranium oxide proceeds, and a uranyl nitrate-containing stock solution is prepared.

  After the dissolution of uranium oxide and nitric acid is completed, the uranyl nitrate solution is cooled by the temperature adjusting means 7, and the water-soluble polymer and then pure water are supplied from the supply path 5 into the dissolution and mixing tank body 4. Thereafter, as shown in FIGS. 2 to 5, the dissolution and mixing tank main body 4 is rotated, and a uranyl nitrate-containing stock solution is prepared by the same stirring action.

  As shown in FIG. 2, after the rotation of the dissolution and mixing tank body 4 is stopped, the prepared uranyl nitrate-containing stock solution is stored in a container (not shown) by opening the discharge port 4A.

  Thereafter, an ammonia aqueous solution having a predetermined concentration and a predetermined amount is accommodated in a reaction tank (not shown). Next, the uranyl nitrate-containing stock solution stored in the container is circulated through a dropping device (not shown), and droplets of the uranyl nitrate-containing stock solution are dropped from the dropping device (not shown) into the aqueous ammonia solution. Thereafter, ammonium biuranate particles are produced by a known method.

According to this embodiment as described above, the following effects are obtained.
(1) A uranyl nitrate-containing stock solution can be easily prepared.

(2) The rotary shaft body 3 includes the supply path 5 and the discharge path 6 so that the raw material can be supplied while the dissolution and mixing tank body 4 rotates and operates. Moreover, since the contents in the dissolution and mixing tank main body 4 can be discharged, the working efficiency can be improved.

(3) Since the temperature adjusting means 7 is provided on the outer peripheral surface of the dissolution and mixing tank main body 4, for example, the temperature of the liquid stored in the inside is changed, and a solution having a predetermined concentration or viscosity is applied. Obtainable.

(4) Since the plate-like member 8 is provided to prevent the entry of neutrons or the like causing a critical state into the dissolution and mixing tank body, the size limit value in the so-called “shape limit” can be increased. it can. Accordingly, the size of the dissolution / mixing tank main body 4 itself can be formed large, so that the productivity can be improved.

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

  Moreover, in the said embodiment, although the rotating shaft body 3 had a double tube structure, it is not restricted to this, For example, as FIG. 6 shows, the external insertion tube 9 with a large internal diameter is shown. It is good also as a structure which provides the two internal intubation tubes 10 whose outer diameter is smaller than the external intubation tube 9 inside. Here, one of the intubation tubes 10 may form a supply path, and the other of the intubation tubes 10 may form a discharge path.

FIG. 1 is a schematic view showing a dissolution and mixing tank according to the present invention. FIG. 2 is a schematic view showing the operation of the dissolution and mixing tank according to the present invention. FIG. 3 is a schematic view showing the operation of the dissolution and mixing tank according to the present invention. FIG. 4 is a schematic view showing the operation of the dissolution and mixing tank according to the present invention. FIG. 5 is a schematic view showing the operation of the dissolution and mixing tank according to the present invention. FIG. 6 is a schematic view showing a modification of the rotating shaft.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Melting | mixing mixing tank 3 Rotating shaft body 4 Dissolving mixing tank main body 4A Discharge port 5 Supply path 6 Discharge path 6A Pump 7 Temperature control means 8 Plate-shaped member 9 Outer tube 10 Inner tube

Claims (4)

  A rotating shaft body having an axis substantially oriented in the horizontal direction, and a dissolution and mixing tank main body formed so as to be rotatable together with the rotating shaft body and having a polygonal cross-sectional shape perpendicular to the horizontal direction. A dissolution and mixing tank characterized by comprising:   The said rotating shaft body is equipped with the supply path which supplies a raw material in the said dissolution mixing tank main body, and the discharge path which discharges the contents in the said dissolution mixing tank main body, The said Claim 1 characterized by the above-mentioned. Dissolution and mixing tank.   The dissolution / mixing tank according to claim 1 or 2, wherein a temperature adjusting means for adjusting a temperature in the dissolution / mixing tank body is provided on an outer peripheral surface of the dissolution / mixing tank body. The plate-like member which respectively contains a neutron absorber is provided in the outer peripheral surface which the said melt | dissolution mixing tank main body opposes, The said any one of the Claims 1-3 characterized by the above-mentioned. Dissolving mixing tank.

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