JP2006315055A - Method and device for manufacturing fuel compact - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for manufacturing a fuel compact, which needs no large space, easily sets the temperatures of a die and a punch, and easily sets the drive of the punch. <P>SOLUTION: A raw material M of the fuel compact, which contains coated fuel particles, is charged into die cavities 20V of a die 20 and subjected to press molding by pressing punches 30 into the die cavities 20V to manufacture a fuel compact F. The die cavities 20V have the shapes of notches, which are provided so as to be opened toward the peripheral face of the disk-like die 20 at some intervals in the peripheral direction. After the raw material M is sequentially charged into each of the die cavities 20V, the corresponding punches 30 are inserted into the die cavities 20V. The punches 30 are pressed into the die cavities 20V by the relative rotation of the die 20 and a punch press 40, which is provided closely to the peripheral face of the die 20 and has a circular arc face 40S with a cam 40SA. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method and apparatus for manufacturing a fuel compact used in a HTGR, and more particularly to a method and apparatus capable of manufacturing a large number of fuel compacts in succession.

  The high temperature gas reactor is composed of graphite that has a large heat capacity and good high temperature integrity, and helium gas that does not cause chemical reaction even at high temperatures. Therefore, helium gas having a high outlet temperature of about 900 ° C. can be taken out, and the high-temperature heat of this helium gas can be used in a wide range of fields such as power generation, hydrogen production, and chemical plants.

The fuel of this HTGR is formed by coating four layers around a fuel core having a diameter of about 350 to 650 microns obtained by sintering uranium dioxide into a ceramic form. The first layer is a coating of low density pyrolytic carbon with a density of about 1 g / cm ³ , which absorbs the function of the gaseous fission product (FP) as a reservoir and fuel nuclear swelling. It also has a function as a buffer. The second layer is a coating of high density pyrolytic carbon having a density of about 1.8 g / cm ³ , which has a retention function for gaseous FP. The third layer is a coating of silicon carbide (SiC) having a density of about 3.2 g / cm ³ , which has a function of holding solid FP and functioning as a main reinforcing member of the coating. Finally, the fourth layer, like the second layer, is a high-density pyrolytic carbon coating with a density of about 1.8 g / cm ³ , which is a gaseous FP retention function and third layer protection. It functions as a layer.

  Typical coated fuel particles have a diameter of about 500 to 1000 microns. The coated fuel particles are dispersed in a graphite matrix, and then molded into a fixed fuel compact shape. A fixed amount of the fuel compact is placed in a graphite tube, and the top and bottom are closed with plugs to form fuel rods. . This fuel rod is inserted into a plurality of insertion ports of the hexagonal column type graphite block and becomes fuel for the high temperature gas furnace. A large number of hexagonal columnar graphite blocks are stacked in multiple stages on a honeycomb array to constitute a core.

  Generally, the fuel for the HTGR is manufactured as follows. First, uranium oxide powder is dissolved in nitric acid to form a uranyl nitrate stock solution, and pure water and a thickener are added to the uranyl nitrate stock solution and stirred to prepare a dropping stock solution. The thickener acts so that the dropped solution of the uranyl nitrate stock solution dropped into a spherical shape with its own surface tension during dropping. As such a thickener, a resin having a property of solidifying under an alkaline condition, for example, a polyvinyl alcohol resin, polyethylene glycol, or metroise can be used. The dripping stock solution prepared in this manner is cooled to a predetermined temperature and the viscosity is adjusted, and then dropped into ammonia water using a method of vibrating a small-diameter dropping nozzle.

  The droplet liquid is prevented from being deformed at the time of landing by spraying ammonia gas in a space until it reaches the surface of the aqueous ammonia solution to gel the surface. Uranyl nitrate is sufficiently reacted with ammonia in ammonia water to form particles of ammonium heavy uranate (hereinafter referred to as ADU particles). After drying, the ADU particles are roasted in the atmosphere to become uranium trioxide particles, and further reduced and sintered to become high-density ceramic uranium dioxide particles. The particles are sieved to obtain fuel nuclei with a predetermined particle size.

The fuel nuclei are loaded on the fluidized bed, and the reaction gas (coating gas) supplied into the fluidized bed is thermally decomposed to coat the fuel nuclei. The first layer of low density pyrolytic carbon is coated by pyrolyzing acetylene (C ₂ H ₂ ) at about 1400 ° C. The high density pyrolytic carbon of the second and fourth layers is coated by pyrolyzing propylene (C ₃ H ₆ ) at about 1400 ° C. The third layer of SiC is coated by pyrolyzing methyltrichlorosilane (MTS) (CH ₃ SiCl ₃ ) at about 1600 ° C. In this way, four layers of coating are applied to obtain a coated particle fuel.

  The fuel compact is manufactured by pressure molding the coated fuel particles. In this case, the coated fuel particles are pressure molded in a state dispersed in the graphite matrix, or the coated fuel particles are overcoated with the graphite matrix and the overcoated particles are dispersed in the graphite matrix alone. Or press molding.

  In the prior art, the raw material is pressure-molded using the apparatus shown in FIG. This apparatus includes a die 20 having a mold recess 20V and upper and lower punches 30U and 30D which are inserted into the mold recess 20V and pressurize a raw material. After the raw material containing the coated fuel particles is loaded into the mold cavity 20V, the upper or lower punches 30U and 30D are slowly pushed in and molded by pressure, but the phenol resin contained in the graphite matrix is softened and molded. In order to facilitate, the raw material, the die and the punch are heated to the softening temperature of the phenolic resin.

  In this prior art, since the punch must be moved at a low speed, it is necessary to continuously mold using a plurality of sets of dies and punches in order to improve productivity. In addition to a large space for installing the dies and punches, it is necessary to provide means for simultaneously driving a plurality of sets of dies and punches and a means for adjusting the temperature of the plurality of dies and punches. However, there is a drawback that it is complicated and large.

  One problem to be solved by the present invention is to provide a method for manufacturing a fuel compact that does not require a large space, and that can easily set the temperature of the die and punch and the simultaneous driving of the punch. is there.

  Another problem to be solved by the present invention is to provide a fuel compact manufacturing apparatus that can easily set the temperature of the die and punch and the simultaneous driving of the punch without requiring a large space. is there.

  A first problem-solving means of the present invention is a method for manufacturing a fuel compact by loading a fuel compact material containing coated fuel particles into a die cavity of a die, and pressing and pressing the punch into the mold cavity. The mold recesses are provided at intervals in the circumferential direction so as to open to the peripheral surface of the disk-shaped die, and after sequentially loading the raw materials into each mold recess, the corresponding punches are inserted into the mold recesses, It is an object of the present invention to provide a method for manufacturing a fuel compact characterized in that a punch is pushed in by relative rotation between a die and a punch press having a circular arc surface with a cam provided close to the peripheral surface of the die.

  In the first problem solving means of the present invention, it is preferable that the punch press is fixed and the die is rotated so that the peripheral surface of the die moves along the arc surface of the punch presser. In this case, the die rotates around the horizontal rotation axis, and when the mold recess is in the upper position, the die is loaded, and when passing through the punch press and the mold recess is in the lower position, the fuel compact is taken out by its own weight. Can be.

  According to a second means for solving the problems of the present invention, a die having a mold recess into which a fuel compact material containing coated fuel particles is to be loaded in a die cavity of the die, and being pressed into the mold cavity to press-mold the material. In the fuel compact manufacturing apparatus comprising a punch, the die has a disk shape having a plurality of notch-shaped recesses provided at intervals in the circumferential direction so as to open on the peripheral surface thereof, The fuel further comprises a punch press having a circular arc surface with a cam that is provided close to the peripheral surface of the die and presses the punch inserted into the mold cavity by a rotational movement relative to the die. The object is to provide a compact manufacturing apparatus.

  In the second problem-solving means of the present invention, it is preferable that the punch press is fixed and a die rotating means for rotating the die so that the peripheral surface of the die moves along the arc surface of the punch press is provided. In this case, the die rotating means is configured to rotate the die about the horizontal rotation axis, and is loaded with the raw material when the die recess is in the upper position, passes through the punch press, and the die recess is in the lower position. Sometimes the fuel compact can be removed by its own weight.

  As described above, the present invention has a plurality of mold recesses in one disk-shaped die, and it is only necessary to correspond one punch to each mold recess. Since it can be manufactured, and therefore the installation space of the apparatus is small, and a plurality of punches can be pushed in with one simple punch press, the apparatus is not complicated, and the apparatus is small and simple. The fuel compact can be mass-produced and the device can be easily managed.

  Since the movement of the apparatus is simple and the apparatus can be continuously operated by inserting the punch into the die again after the molding is completed, the apparatus can be easily automated.

  When the mold cavity is in the upper position during the rotation of the die, the material is loaded into the mold cavity, and when the mold recess reaches the lower position after passing through the punch holder, the fuel compact is removed from the mold cavity with its own weight. Since it is possible to take out the fuel compact by letting it fall naturally, it is advantageous because it does not require any special removal operation and means for it.

  An embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a manufacturing apparatus 10 suitable for carrying out a method for manufacturing a fuel compact according to the present invention. It comprises a die 20 having a mold recess 20V to be loaded with a fuel compact material M containing fuel particles, and a punch 30 for pressing the material M into the mold recess 20V.

  The die 20 has a disk-like form having a plurality of notched mold recesses 20V provided at intervals in the circumferential direction so as to open to the peripheral surface, and the punch 30 has a plurality of these mold recesses. It is prepared for 20V. In the illustrated form, eight mold recesses 20V are provided at an angular interval of 45 degrees, but the number of mold recesses is set as appropriate.

  The manufacturing apparatus 10 of the present invention has a cam-equipped arc surface 40S that is provided close to the peripheral surface of the die 20 and that pushes the punch 30 inserted into the mold recess 20V by a relative rotational movement with the die 20. A presser 40 is further provided. The cam 40SA of the circular arc surface 40S of the punch presser 40 has a large distance from the peripheral surface of the die 20 at the portion (inlet) where the punch 30 enters due to the relative rotational movement of the die 20 and the punch press punch 30. It is formed so that the distance from the peripheral surface of the die 20 becomes smaller as it enters, and the punch 30 is guided to be gradually pushed deeply into the mold recess 20V.

  In the form shown in the figure, the punch presser 40 is disposed and fixed so as to cover a substantially half of the peripheral surface of the die 20, and the peripheral surface of the die 20 moves along the arc surface 40 </ b> S of the punch presser 40. A die rotating means (not shown) for rotating the die 20 is provided.

  The die rotating means is configured to rotate around the horizontal rotation axis X (see FIG. 1) provided at the center of the die 20. The fuel compact material M is loaded into the mold cavity 20 when each mold cavity 20 is in the vicinity of the upper position (in the illustrated example, the position slightly above the left (I)). After 20V passes through the punch presser 40 and a predetermined fuel compact F is molded, when the mold recess 20 is removed from the punch presser 40 and is in a lower position (position (III) immediately below in the illustrated example) The corresponding punch 30 and the fuel compact F are taken out of the mold cavity 20 by their own weight. In FIG. 2, the position (II) is a position where the punch 30 inserted into each mold recess 20 </ b> V starts to engage with the cam 40 SA of the punch presser 40.

  Next, a method for manufacturing a fuel compact according to the present invention will be described with reference to FIG. 1. First, a fuel compact material M is loaded into a mold recess 20V at position (I) in FIG. The punch 30 corresponding to is inserted. The raw material M is loaded in the same manner into the mold recess 20V that sequentially reaches the position (I) by the rotation of the die 20. As already mentioned, the raw material M can be a mixture of coated fuel particles and graphite matrix, a mixture of overcoat particles and graphite matrix or overcoat particles only.

  After the raw material M is loaded into each mold recess 20V, the punch 30 is inserted into each mold recess 20V. The punch 30 engages with the cam 40SA of the punch presser 40 at position (II) as the die 20 rotates. start. Since the cam 40SA of the arc surface 40S is formed so as to gradually approach the die peripheral surface, the punch 30 is guided by the cam 40SA so as to be gradually pushed into the mold recess 20V to pressurize and mold the material M. . After passing through the cam 40SA, the arc surface 40S extends at the same interval as the peripheral surface of the die, so that the punch 30 is not pushed further into the mold recess 20V and excessively pressurizes the raw material M. There is no.

  When each mold recess 20V in which the punch 30 is inserted passes through the last part of the arc surface 40S of the punch retainer 40 and reaches the position (III), the mold recess 20V opens downward. The fuel compact F is naturally dropped from the mold cavity 20V and taken out.

  A number of fuel compacts F can be manufactured sequentially by repeating the above operations. In this method, since one die 20 and one punch press (punch driving means) are used, all pressure molding is performed at the same die temperature and the same punch pressure, and these controls and management are easy. It becomes.

  In the above embodiment, the punch press 40 is fixed and the die 20 is rotated. Instead of rotating the die 20, the punch press 40 may be rotated along the peripheral surface of the die 20. Even in this case, at least when the raw material M is loaded, it is necessary to be able to rotationally displace the die 20 so that the mold recess 20V opens upward or obliquely upward.

  Further, the depth of the notch of the die recess 20V of the die 20, the shape of the bottom of the notch, the length of the punch 30, and the shape of the tip head of the punch 30 are inserted into the die recess 20V of the die 20. In this case, the space formed by the two is determined so as to coincide with the outer diameter of the fuel compact.

  When the raw material is a mixture of overcoat particles and graphite matrix, as described above, from the viewpoint of compressibility of the overcoat particles, the temperature of the overcoat particles themselves is set in the graphite matrix before loading into the die 20. It is preferable to raise to the softening temperature of the phenol resin. The overcoat particles heated to the softening temperature of the phenol resin are naturally cooled while being compressed by the punch 30, and the phenol resin is cured when taken out at the position (III), so that the shape is maintained. The subsequent processing can be performed as it is.

  In one embodiment of the present invention, the die 20, the punch 30, and the punch presser 40 were each made of alloy tool steel. The surface of the notch which is the mold recess 20V of the die 20, the surface of the punch 30, and the contact surface of the punch presser 40 with the punch 30 were lapped. It is more effective to improve the wear resistance by subjecting these surfaces to surface treatment such as hard chrome plating. The radius of the die 20 was 130 mm, and eight notch-shaped mold recesses 20V were uniformly formed on the peripheral surface. Further, the notch depth of the mold recess 20V (the length of the straight portion) and the height of the punch 30 (the length of the straight portion) are 40 mm, and the shape of the bottom portion of the notch and the tip head portion of the punch 30 is a radius of 13 mm. R shape (see FIG. 2). Further, the shape of the surface of the punch 30 that contacts the punch retainer 40 was a spherical shape with a radius of 20 mm, and the gap G between the punch 30 and the arcuate surface 40S of the punch retainer 40 was 5 mm (see FIG. 2). The die 20 was rotated clockwise in FIG. 1 at a rotation speed per rotation of 20 minutes.

  In the above embodiment, the number of the mold recesses 20V and the punches 30 is eight, but it goes without saying that these numbers can be changed as necessary. That is, when the outer diameter of the die 20 cannot be increased so much due to the limitation of the installation space or when it is not necessary to mold a large amount of fuel compact, the die recess 20V is reduced by making the radius of the die 20 smaller than 130 mm. The number of punches 30 may be reduced. If the installation space is not limited, if it is necessary to mold a large amount of fuel compact, or if it is necessary to take out the fuel compact F after it has been sufficiently cooled, the die 20 has a radius larger than 130 mm, The number of notches and punches 30 that are the recesses 20V can be increased. Further, the depth of the notch 20V and the height of the punch 30 vary depending on the characteristics of the graphite powder used, the firing conditions after molding, and the fuel compact size standard, and should be changed according to each condition. It is. Further, the spherical dimension of the head of the punch 30 and the gap G between the punch 30 and the arcuate surface 40S of the punch retainer 40 have an effect on friction such as the material, surface roughness, surface treatment state, etc. of the punch 30 and punch retainer 40. It is good to change appropriately considering the above.

  According to the present invention, a plurality of notch-shaped mold depressions are provided on the peripheral surface of one disk-shaped die, and a punch for pressing the raw material placed in each mold depression of the die is brought close to the peripheral surface of the die. Since the raw material is pressurized by being pushed into the mold recess by the relative rotational movement of the punch press provided, a large number of fuel compacts can be manufactured sequentially with a small space and a simple configuration, and the temperature can be easily set. Management settings can be made, and industrial applicability is improved.

It is a schematic explanatory drawing of the fuel compact manufacturing apparatus of this invention. It is a figure explaining the dimensional relationship of one mold depression, a punch, and a punch press. It is sectional drawing before pressurization (A) and after pressurization (B) of the fuel compact manufacturing apparatus by a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel compact manufacturing apparatus 20 Dice 20V Type recess 30 Punch 40 Punch presser 40S Circular surface 40SA Cam X axis G Gap M Raw material F Fuel compact

Claims (6)

In a method for manufacturing a fuel compact by loading a fuel compact raw material containing coated fuel particles into a die recess of a die and pressing a punch into the mold recess to produce a fuel compact, the mold recess is a peripheral surface of a disk-shaped die Are opened at intervals in the circumferential direction, and after the raw material is loaded into the mold recess, the punch is inserted into the mold recess and approaches the die and the peripheral surface of the die. A method for producing a fuel compact, wherein the punch is pushed in by relative rotation with a punch press having a circular arc surface with a cam provided. 2. The fuel compact manufacturing method according to claim 1, wherein the punch press is fixed, and the die is rotated so that a peripheral surface of the die moves along an arc surface of the punch presser. A method for manufacturing a fuel compact. 3. The method of manufacturing a fuel compact according to claim 2, wherein the die rotates about a horizontal rotation axis, and the raw material is loaded when the mold recess is at an upper position, and passes through the punch presser. A method of manufacturing a fuel compact, wherein the fuel compact is taken out by its own weight when the mold cavity is in a lower position. In a fuel compact manufacturing apparatus comprising a die having a mold recess to be filled with a fuel compact raw material containing coated fuel particles, and a punch for pressing the raw material into the mold recess, the die comprises: It has a disk-like form having a plurality of notch-shaped recesses provided at intervals in the circumferential direction so as to open to the peripheral surface, and is provided close to the peripheral surface of the die. An apparatus for manufacturing a fuel compact, further comprising a punch press having a circular arc surface with a cam for pressing the punch inserted into the mold cavity by a rotational movement relative to a die. 5. The fuel compact manufacturing apparatus according to claim 4, wherein the punch press is fixed, and the die rotating means is configured to rotate the die so that a peripheral surface of the die moves along an arc surface of the punch press. An apparatus for manufacturing a fuel compact, comprising: 6. The fuel compact manufacturing apparatus according to claim 5, wherein the dice rotating means is configured to rotate the dice around a horizontal rotation axis, and the raw material is supplied when the mold recess is in an upper position. An apparatus for manufacturing a fuel compact, wherein the fuel compact is taken out by its own weight when loaded and passed through the punch press and the mold recess is in a lower position.

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