JP2006133063A - Device for manufacturing coated fuel particle for high-temperature gas-cooled reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve maintainability of a fluidized bed by facilitating access in the fluidized bed. <P>SOLUTION: This device is equipped with a chamber 18 having a heater 16 and a heat insulating material 16 enclosing the periphery of a reaction tube 12 wherein pyrolysis gas is reacted with a fuel kernel. The chamber 18 comprises a chamber body 20 having an opening on a part of the peripheral wall, and a front door 22 formed so as to close the opening 21 of the chamber body 20 and fitted openably/closably to the chamber body 20. The chamber 18 has a configuration wherein the heater 14 and the heat insulating material 16 are fitted dividedly in the chamber body 20 and the front door 22, and a heat insulating material 16A on the chamber body 20 side and a heat insulating material 16B on the front door 22 side are brought into close contact with each other while the front door 22 is closed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for producing coated fuel particles used in, for example, a high-temperature gas furnace, and more particularly to an apparatus for producing coated fuel particles for a high-temperature gas furnace that can improve the handling of a fluidized bed.

  The HTGR is composed of graphite that has a large heat capacity and maintains its soundness at high temperatures, and the helium gas that does not cause a chemical reaction even at high temperatures is used as a cooling gas to cool the core. Therefore, helium gas having a high exit temperature of about 900 ° C. is 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 the HTGR is formed by applying four layers of coating around a fuel core having a diameter of about 350-650 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 silicon carbide (SiC) coating having a density of about 3.2 g / cm 3, which has a function of holding the solid FP and a function 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 fuel compact shape having a fixed shape. A fixed amount of the fuel compact is placed in a graphite tube, and the top and bottom are sealed with stoppers to form fuel rods. Is done. 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 into a fluidized bed, and a reaction gas (coating gas) is supplied in the fluidized bed and thermally decomposed to be coated. 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. A general fuel compact is obtained by press-molding or molding coated fuel particles into a hollow cylindrical shape or a cylindrical shape together with a graphite matrix material made of graphite powder, a binder or the like, and then sintering.

  The conventional apparatus for producing coated fuel particles can be opened and closed at the ceiling of the chamber (see Patent Document 1), and therefore, the inside of the fluidized bed can only be accessed from the ceiling of the chamber. For this reason, the attachment and detachment of the reaction tube and the cleaning of the fluidized bed are performed on the ceiling of the chamber. Therefore, the handling of the fluidized bed is troublesome and its maintenance is very low.

Japanese Patent Application Laid-Open No. 5-287285

  The problem to be solved by the present invention is to provide an apparatus for producing coated fuel particles for a HTGR that can easily access in the fluidized bed and thus can improve the maintainability of the fluidized bed. is there.

  The problem-solving means of the present invention includes a reaction tube for reacting a pyrolysis gas while fluidizing fuel nuclei in a high-temperature state, and a high-temperature gas furnace having a chamber having a heater and a heat insulating material surrounding the reaction tube In the coated fuel particle manufacturing apparatus, the chamber is composed of a chamber main body having a part of the peripheral wall opened and a front door formed to close the opening of the chamber main body and attached to the chamber main body so as to be opened and closed. The heater and the heat insulating material are divided and attached to the chamber main body and the front door, and the heat insulating material on the chamber main body side and the heat insulating material on the front door side are in close contact with the front door closed. An object of the present invention is to provide an apparatus for producing coated fuel particles for a HTGR characterized by the above.

  In the problem-solving means of the present invention, the front door may be hinged to the chamber main body, or may be slidably attached to the upper or lower side of the chamber main body. The apparatus includes sliding opening / closing operation means for opening / closing the front door.

  According to the present invention, the fluidized bed can be easily accessed by opening and closing the front door, and therefore, the reaction tube can be easily attached and detached, and the fluidized bed can be easily cleaned.

  An embodiment of the present invention will be described in detail with reference to the drawings. FIGS. 1 to 3 show one embodiment of a manufacturing apparatus 10 for coated fuel particles for a high temperature gas reactor according to the present invention. Accommodates a reaction tube 12 that reacts a reaction gas with a fuel nucleus and coats the surface thereof, and a chamber (outer wall) having a heater 14 and a heat insulating material 16 attached so as to surround the reaction tube 12. 18 is provided.

  The chamber 18 includes a chamber main body 20 that is opened by cutting a part of its peripheral wall, and a front door 22 that is formed to close the opening of the chamber main body 20 and is attached to the chamber main body 20 so as to be openable and closable. (See FIG. 3), the heater 14 and the heat insulating material 16 are divided into the chamber body 20 and the front door 22 as shown by reference numerals 14A and 16A (main body side) and reference numerals 14B and 16B (front door side). Installed. In the state where the front door 22 is closed, the heat insulating material 16A on the chamber body 20 side and the heat insulating material 16B on the front door 22 side are in close contact with each other, so that a reaction occurs between the chamber main body 20 and the front door 22. The heat insulation in the fluidized bed of the pipe 12 is not deteriorated.

  1 and 2, the front door 22 is attached to the edge of the opening 21 of the chamber body 20 by a hinge 24 so as to be freely opened and closed, and the opening degree is 180 ° as shown in FIG. However, it can be set appropriately in consideration of the work space and workability.

  Further, the front door 22 includes a front door fixing means 28 including a plurality of fastening fittings 26 that keep the opening 21 of the chamber body 20 closed. This fastening metal fitting 26 can be in an appropriate form for fixing them so as to be in close contact with each other across the edge of the chamber body 20 and the edge of the front door 22. As can be seen from FIG. 3, these fastening fittings 26 are fastened between the peripheral rib 20 r of the chamber body 20 and the peripheral rib 22 r of the front door 22.

  The chamber 18 is supported on the base 30 via the leg member 32, and the reaction tube 12 is provided between the base 30 and the chamber body 20 and connected to a reaction gas supply source (not shown). The gas supply pipe 34 communicates with the reaction pipe 12.

  4 and 5 show an apparatus 10 for producing coated fuel particles for a HTGR according to another embodiment of the present invention. In the apparatus 10 of this embodiment, the front door 22 is not a front opening, and the chamber body 20 3 is the same as that shown in FIGS. 1 to 3 except that it is attached so as to open and close by sliding up and down. The same parts as those in FIGS. 1 to 3 are denoted by the same reference numerals.

  4 and 5, the sliding opening / closing operation means 36 for opening / closing the front door 22 is provided. The sliding opening / closing operation means 36 is engaged with the front door 22 to guide the front door 22 up and down. A pair of ball screws 38, 38 ′ and a rotation drive source 40 such as a step motor for rotating these ball screws 38, 38 ′ are driven. The rotation drive source 40 is driven to turn the ball screws 38, 38 ′ By rotating, the front door 22 can be moved between the closed raised position shown in FIG. 4 and the opened lowered position shown in FIG.

  The coated fuel particle manufacturing apparatus 10 of the present invention can open the front door 22 and take out the reaction tube 12 to clean the reaction tube 12. The reaction tube 12 is then connected to the chamber body 20. The front door 22 is closed and the original state is maintained again. If it does in this way, the heat insulating material 16A by the side of the chamber main body 20 and the heat insulating material 16B by the side of the front door 22 will closely_contact | adhere, and it will be in the state where the chamber main body 20 and the front door 22 were integrated.

  In this state, after fuel nuclei are introduced into the reaction tube 12 from the ceiling of the apparatus, various fuel gases are sequentially supplied into the reaction tube 12 through the gas supply tube 34, and the fuel is generated in the fluidized bed of the reaction tube 12. It is possible to sequentially coat the first layer to the fourth layer by reacting the reaction gas with the nucleus. FIG. 6 shows the coated fuel particles produced and recovered in this manner.

1 to 3, the chamber 18 has an outer diameter of about 700 mm and a height of about 2200 mm, and the reaction tube 12 made of graphite has an outer diameter of about 700 mm. It had an inner diameter of 200 mm and a height of about 1000 mm. About 3.8 kg of uranium dioxide fuel core having an average diameter of 0.6 mm is introduced into the reaction tube 12, and acetylene gas C ₂ H ₂ (reaction for coating the first layer) at a temperature of about 1400 ° C. from the gas supply tube 34. Gas) to form a first layer of low density carbon coating, and then at a temperature of about 1400 ° C., propylene gas C ₂ H ₆ (reactive gas for second layer coating) is flowed to A high density carbon coating is formed and methyltrichlorosilane CH ₂ SiCl ₂ (reactive gas for third layer coating) is introduced at a temperature of about 1600 ° C. to form a third layer silicon carbide coating, and finally Then, propylene gas C ₂ H ₆ (reaction gas for coating the fourth layer) was introduced at a temperature of about 1400 ° C. to form a fourth layer of high-density carbon coating. The average diameter of the coated fuel particles thus obtained was 0.93 mm. The thickness of each layer was 0.06 mm for the first layer, 0.03 mm for the second layer, and 0.03 mm for the third layer. 03 mm and 0.045 mm for the fourth layer.

  When the front door 22 is opened, the reaction tube 12 can be attached and detached, so that the attachment / detachment work is easy, and foreign matter such as graphite powder and soot adhering to the fluidized bed can be easily removed with a vacuum cleaner or the like. Can be eliminated.

  According to the present invention, since the fluidized bed can be easily accessed by opening and closing the front door, the reaction tube can be easily attached and detached, and the fluidized bed can be easily cleaned. improves.

It is a front view of the manufacturing apparatus of the covering fuel particle for high temperature gas reactors by one form of this invention. It is a front view of the state which opened the front door with the manufacturing apparatus of FIG. FIG. 3 is a horizontal sectional view of the apparatus of FIGS. 1 and 2. It is a front view of the manufacturing apparatus of the coating fuel particle for high temperature gas reactors by the other form of this invention. It is a front view of the state which opened the front door with the manufacturing apparatus of FIG. It is a top view of the deposition state of the covering fuel particle obtained by the manufacturing apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Coated fuel particle manufacturing apparatus 12 Reaction tube 14, 14A, 14B Heater 16, 16A, 16B Heat insulating material 18 Chamber 20 Chamber main body 20r Peripheral rib 21 Opening 22 Front door 22r Peripheral rib 24 Hinge 26 Fastening fitting 28 Front door fixing means 30 Base 32 Leg member 34 Gas supply pipe 36 Front door opening / closing operation means 38 Ball screw 40 Rotation drive source

Claims (3)

In an apparatus for producing coated fuel particles for a high temperature gas furnace, comprising a chamber having a heater and a heat insulating material that encloses a reaction tube for reacting a pyrolysis gas while fluidizing a fuel nucleus at a high temperature, and surrounding the reaction tube, The chamber includes a chamber body having a part of a peripheral wall opened, and a front door that is formed to close the opening of the chamber body and is attached to the chamber body so as to be openable and closable. Is divided and attached to the chamber main body and the front door, and is configured such that the heat insulating material on the chamber main body side and the heat insulating material on the front door side are in close contact with the front door closed. An apparatus for producing coated fuel particles for a HTGR, 2. The apparatus for producing coated fuel particles for a high temperature gas reactor according to claim 1, wherein the front door is hinged to the chamber body. 2. The apparatus for producing coated fuel particles for a HTGR according to claim 1, wherein the front door is slidably attached to the chamber body upward or downward, and opens and closes the front door. An apparatus for producing coated fuel particles for a HTGR characterized by comprising dynamic opening / closing operation means.

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