JP2006064442A - Manufacturing device of hollow fuel compact for high-temperature gas furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a high-quality hollow fuel compact in size, by pressing molding of all weighed raw materials (coated fuel particles and graphite matrix material). <P>SOLUTION: The hollow fuel compact is manufactured, by pressing raw material particles 20 of the fuel compact between upper and lower punches 12 and 14 around a core rod 18 in a metal mold 16. A conical surface 22CO is provided on a raw material input-side end part of the core rod 18 for guiding the raw material 20 so that all of these drop around the core rod 18. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for producing a hollow fuel compact for a high temperature gas reactor, for example, and more particularly to an apparatus capable of producing a high quality hollow fuel compact.

  The HTGR consists of graphite that has a large heat capacity and maintains soundness at high temperatures, and uses helium gas that does not cause chemical reactions at high temperatures as a cooling gas. Therefore, inherent safety is high, and helium gas having a high outlet temperature of about 900 ° C. can be recovered, and this high-temperature heat can be used in a wide range of fields such as power generation, hydrogen production, and chemical plants.

The fuel in this HTGR is formed by coating four layers around a fuel core having a diameter of about 350-650 microns obtained by sintering uranium dioxide into a ceramic. 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 500-1000 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 sealed with plugs to form fuel rods. The 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 biuranate. These particles are roasted in the atmosphere to become uranium trioxide particles, and further reduced and sintered to become fuel nuclei of high-density ceramic uranium dioxide.

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 (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 for a HTGR is generally manufactured by press-molding or molding these coated fuel particles into a hollow cylindrical shape or a cylindrical shape together with a graphite matrix material made of graphite powder, caking, or the like, and then firing it.

  Among these, when a hollow fuel compact is formed by press molding, a mixture of coated fuel particles and graphite matrix material, which are raw materials for the fuel compact, is pressed around the core rod by upper and lower punches in order to make the compact into a hollow cylindrical shape. is doing. That is, the raw material is put around the core rod on the lower punch of the mold, and then the upper punch is pressurized to produce a hollow cylindrical fuel compact.

  In the prior art, the raw material particles are loaded around the core rod by pouring the raw material particles weighed in advance into the mold by gravity using an appropriate type of feeder.

  However, as shown by reference numeral 18E in FIG. 2, the core rod input side end portion has a flat shape, so that the raw material (see reference numeral 20) does not enter the mold 16 and enters the flat end portion 18E of the core rod 18. ) May be left with a part of it remaining, and the press will be molded with a portion of the weighed raw material missing. There was a drawback that it was not possible to obtain a hollow fuel compact having a stable quality that deviated from the set value.

  The problem to be solved by the present invention is to provide an apparatus capable of producing a high-quality hollow fuel compact by press-molding all the weighed raw materials.

  The problem solving means of the present invention is to provide a hollow fuel compact manufacturing apparatus for a high temperature gas reactor in which fuel compact raw material particles are pressed between upper and lower punches around a core rod in a mold to produce a hollow fuel compact. It is an object of the present invention to provide an apparatus for manufacturing a hollow fuel compact for a high temperature gas reactor, characterized in that a guide inclined surface for guiding the raw material to fall around a core rod is provided at the raw material charging side end.

  In the problem-solving means of the present invention, the guide inclined surface of the raw material charging side end of the core rod can be typically a conical surface, but the raw material does not remain at the raw material charging side end of the core rod. An inclined surface other than the conical surface may be used as long as it can be guided around.

  According to the present invention, a part of the weighed raw material does not remain at the raw material input side end of the core rod, and all the raw material is guided to the press space, so that the uranium amount and the compact density are not affected. A high quality hollow fuel compact can be obtained.

  An embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a manufacturing apparatus 10 for a hollow fuel compact for a HTGR according to the present invention. The core rod 18 is arranged at the center of the mold 16. The core rod 18 is inserted into and supported by the rod support hole 14H of the lower punch 14, and the upper punch 12 has a rod through hole 12H through which the core rod 18 passes.

  The fuel compact raw material 20 is weighed at a value required to obtain a predetermined amount of uranium and a compact density, and is loaded into a press space around the core rod 18 in the mold 16 by a feeder not shown.

  In the illustrated form, the raw material 20 consists only of overcoat particles 20P formed by overcoating a graphite matrix material on the coated fuel particles, but is a mixture of the coated fuel particles and the graphite matrix material. Alternatively, it may be a mixture of overcoat particles and a graphite matrix material.

  The manufacturing apparatus 10 of the present invention has a guide inclined surface 22 that guides the raw material 20 to fall around the core rod 18 at the raw material charging side end of the core rod 18. In the illustrated embodiment, the guide inclined surface 22 is shown to be a conical surface 22CO. However, the raw material 20 does not remain at the raw material charging side end of the core rod 18 and the inside of the mold around the core rod 18 As long as it can be guided to the space, for example, an oblique cut surface 22IN as shown in FIG. 2 and other arbitrary forms can be used.

  In this way, the raw material charged into the mold 16 does not remain at the end of the core rod 18 and is all charged into the mold 16, so that all of the weighed raw materials are press-molded, and the amount of uranium In addition, a high-quality hollow fuel compact can be obtained without affecting the compact density.

  According to the present invention, since all the weighed raw materials are press-molded, a high-quality hollow fuel compact can be manufactured, and therefore, it can be suitably used for manufacturing a high-temperature gas reactor fuel compact.

It is sectional drawing of the manufacturing apparatus of the hollow fuel compact for high temperature gas reactors of this invention. It is a side view of a part of another form of core rod used in the present invention. It is a partial side view of the core rod used by the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Manufacturing apparatus of hollow fuel compact for HTGR 12 Upper punch 12H Rod through-hole 14 Lower punch 14H Rod support hole 16 Mold 18 Core rod 20 Raw material 20P Overcoat particle 22 Guide inclined surface 22CO Conical surface 22IN Oblique cut surface

Claims (2)

In a high-temperature gas reactor hollow fuel compact manufacturing apparatus for manufacturing a hollow fuel compact by pressing fuel compact raw material particles between upper and lower punches around a core rod in a mold, An apparatus for producing a hollow fuel compact for a high temperature gas reactor, comprising a guide inclined surface for guiding the raw material to fall around a core rod. The hollow fuel compact for a HTGR according to claim 1, wherein the guide inclined surface of the raw material charging side end portion of the core rod is a conical surface. Manufacturing equipment.

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