JP2007285921A - Device for manufacturing coated fuel particle for high-temperature gas-cooled reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device which can manufacture high-quality coated fuel particles by making it possible to manage the gasification and supply of a liquid material in processes for manufacturing coated fuel particles for a high-temperature gas-cooled reactor more stably than ever. <P>SOLUTION: A means for gasifying and supplying the liquid material in the device for manufacturing coated fuel particles for a high-temperature gas-cooled reactor is equipped with an online gas analyzer which, in a predetermined position upstream to a nozzle in a pipe, takes in a portion of a mixed gas of the steam of the liquid material taken into bubbles of a sweep gas released from a nozzle means into the liquid material inside a material tank, recovered as a mixed gas with the sweep gas on the liquid level of the material tank and fed to a gas concentrated pipe to measure the material concentration of it. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus for producing high temperature gas furnace coated fuel particles, for example, and more particularly to a means for gasifying and supplying a liquid raw material to a reaction vessel for forming a coating layer by chemical vapor deposition.

  High-temperature gas reactors have a core structure that contains fuel, made of graphite with a large heat capacity and good high-temperature soundness, and by using a gas coolant that does not cause a chemical reaction even at high temperatures such as helium. Helium gas can be taken out at a high outlet temperature, and the resulting high-temperature heat of about 900 ° C. enables heat utilization in a wide range of fields such as hydrogen production and chemical plants as well as power generation. Is.

  The fuel of such a high temperature gas reactor is generally composed of a spherical particle-shaped fuel nucleus having a diameter of about 350 to 650 μm, which is obtained by sintering uranium dioxide produced from a solution containing uranium as a starting material into a ceramic form, Coated fuel particles formed by forming a plurality of coating layers on the outer surface of the fuel core are used.

The coated fuel particles have a low density of about 1 g / cm ³ for the first coating layer, for example, which has both a function as a gas stopper for gaseous fission products and a function as a buffer for absorbing deformation of the fuel particles. A dense pyrolytic carbon layer is formed, and a high density pyrolytic carbon layer having a density of about 1.8 g / cm ³ is formed in the second coating layer as having a function of holding gaseous fission products. The layer has a function of retaining a solid fission product and has a density of about 3.2 g / cm ³ silicon carbide (SiC) as a main strength member of the coating layer, and the fourth coating layer includes a second coating layer and In general, a coating layer of a total of four layers in which a high-density pyrolytic carbon layer having a density of about 1.8 g / cm ³ is formed as a protective layer of the third coating layer together with the holding function of the similar gaseous fission product is provided. It has become.

  The coated fuel particles obtained in this way have a particle size and sphericity that greatly affect the conditions for producing overcoat particles. To be served. The overcoat particles formed by coating the surface of the coated fuel particles with a graphite matrix material consisting of graphite powder, binder, etc. are further subjected to particle size selection with a sieve, and then in the graphite base material in a compact press process. And is pressed or molded into a fixed shape such as a hollow cylindrical shape or a cylindrical shape and becomes a fuel compact after sintering.

  These fuel compacts are put into a cylinder made of graphite, and are made into fuel rods that are plugged up and down. Finally, the fuel rod is inserted into a plurality of insertion holes of the hexagonal column type graphite block, and a large number of the hexagonal column type graphite blocks are stacked in a honeycomb array to constitute a core.

Conventionally, the above-mentioned coated fuel particles are loaded with spherical fuel nuclei made of high-density ceramic-like uranium dioxide in a reaction vessel consisting of a fluidized bed, and the raw material gas serving as a coating layer in the reaction vessel is heated. It is manufactured by decomposing and forming a coating layer by chemical vapor deposition (see, for example, Patent Document 1). For example, in the case of the low-density carbon layer of the first coating layer, acetylene (C ₂ H ₂ ) is thermally decomposed at about 1400 ° C., and the high-density pyrolytic carbon layer of the second and fourth coating layers. Is carried out by thermally decomposing propylene (C ₃ H ₆ ) at about 1400 ° C. In the case of the SiC layer of the third coating layer, methyltrichlorosilane (CH ₃ SiCl ₃ ) is thermally decomposed at about 1600 ° C. to form the coating layer.

  In addition, the raw material supplied to the reaction vessel using such a fluidized bed is not limited to a gas raw material such as acetylene or propylene, but may be a liquid raw material such as methyltrichlorosilane. is there. In this case, a vaporizer is used which supplies a liquid raw material as a vapor gas by mixing with a sweep gas.

  This vaporizer includes a raw material tank in which a liquid raw material is stored and a nozzle that introduces a sweep gas to a predetermined depth in the liquid raw material and discharges bubbles, and is installed around the raw material tank. While the inside of the tank is heated from the outside with an electric heater or the like, the vapor of the liquid raw material is taken into the bubble of the sweep gas by bubbling the sweep gas in the liquid raw material, and the mixed gas is recovered on the liquid level of the tank The raw material gas is supplied to the reaction vessel through a piping system. At this time, a mixing facility with a high-flowing hydrogen gas called a gas collecting pipe may be provided in the middle of the piping to the reaction vessel.

JP-A-5-273374

  In the gasification supply of the conventional liquid raw material using the vaporizer as described above, characteristics such as the density and thickness of the vapor deposition coating layer to be formed are not only the vapor deposition temperature and the mixed gas flow rate in the reaction vessel, Since the mixing ratio of the raw material vapor gas in the mixed gas determined in the vaporizer also depends delicately, in order to form a coating layer with a uniform film thickness, it is necessary to manage and stabilize the raw material supply. It is inevitable.

  However, the actual supply amount of liquid raw materials such as methyltrichlorosilane is generally controlled by the remaining amount of the tank before and after the work, and fluctuations in the supply amount with respect to the elapsed time are difficult to understand. For this reason, there is a problem that it is difficult to ensure a stable raw material supply state necessary.

  Furthermore, in the vaporizer tank as described above, the temperature of the liquid raw material itself decreases due to the vaporization heat at the time of evaporation of the liquid raw material, and the temperature of the liquid raw material is kept constant even when the raw material tank is heated from the outside. It is difficult to do this, and the amount of vapor also fluctuates due to the temperature change of the liquid source, leading to instability of the source gas supply amount.

  In view of the above problems, an object of the present invention is to provide an apparatus that can manage gasification and supply of a liquid raw material in the production process of coated fuel particles for high-temperature gas reactors more stably than before and can produce high-quality coated fuel particles. It is to provide.

  In order to achieve the above object, a coated fuel particle manufacturing apparatus for a HTGR according to the invention described in claim 1 is provided in a reaction vessel containing a large number of uranium dioxide fuel nuclei formed into spherical particles. By heating and supplying the flowing gas and the coating raw material gas through the nozzle holes of the gas injection nozzle mounted on the bottom, the surface of the fuel core is changed by the thermal decomposition reaction of the coating raw material gas while flowing the fuel core. In the apparatus for producing coated fuel particles for a high temperature gas furnace to be coated with a vapor deposition layer of coated raw material molecules, a means for gasifying and supplying a liquid raw material of the coated raw material gas, a flowing gas from a supply source of the flowing gas, A gas collecting pipe that joins and mixes the raw material gas from the supply source of the coating raw material gas, and a pipe that sends the gas mixed in the gas collecting pipe to the nozzle, and the gasification supply means includes the liquid A raw material tank for containing the raw material, a heating means for heating the liquid raw material in the raw material tank, a nozzle means for discharging the sweep gas in the liquid raw material, and the sweep gas discharged from the nozzle means as a liquid raw material A raw material gas take-out means for collecting the vapor of the liquid raw material taken into the bubble while rising inside the raw material tank as a mixed gas with the sweep gas on the liquid surface in the raw material tank, and sending it to the pipe; The apparatus further includes an on-line gas analyzer that ingests a part of the mixed gas sent from the gas collecting pipe at a predetermined nozzle upstream position and measures the raw material concentration.

  According to a second aspect of the present invention, there is provided a coated fuel particle manufacturing apparatus for a high temperature gas reactor according to the first aspect of the present invention, wherein the coated fuel particle manufacturing apparatus for a high temperature gas reactor is based on a measurement result by the online gas analyzer. And an automatic control unit for controlling the heating operation mechanism of the heating means or the supply amount adjusting mechanism of the sweep gas.

  Moreover, the coated fuel particle manufacturing apparatus for a HTGR according to the invention described in claim 3 is the coated fuel particle manufacturing apparatus for a HTGR according to claim 1, wherein the online gas analyzer is a gas chromatograph device. Is included.

  In the coated fuel particle manufacturing apparatus for a HTGR according to the present invention, as means for gasifying and supplying the liquid raw material, the liquid raw material is vaporized by bubbling the sweep gas into the liquid raw material in the raw material tank, and the sweep gas and It is collected as a mixed gas, sent to a gas collecting pipe, where it is combined with a flowing gas, and sent to the gas ejection nozzle of the reaction vessel via a pipe, and a part of the mixed gas is provided at a predetermined nozzle upstream position of the pipe Because it is equipped with an on-line gas analyzer that ingests and measures the concentration of raw materials, it can adjust the gasification supply amount of the liquid raw material based on the measurement results by this analyzer, and maintain a stable supply amount, There is an effect that a coating layer having a uniform thickness can be formed.

  The coated fuel particle manufacturing apparatus for a HTGR of the present invention is a means for gasifying and supplying a liquid raw material of a coating raw material gas, the gasification supply means includes a raw material tank for containing the liquid raw material, The heating means for heating the liquid raw material in the raw material tank, the nozzle means for discharging the sweep gas in the liquid raw material, and the sweep gas discharged from the nozzle means were taken into the bubbles while rising in the liquid raw material as bubbles. Gas for recovering vapor of liquid raw material as a mixed gas with sweep gas on the liquid level in the raw material tank, and mixing and mixing the fluid gas from the fluid gas supply source and the material gas from the coating material gas supply source And a raw material gas take-out means for sending to the gas collecting pipe, and a predetermined upstream position of the pipe for sending the mixed gas from the gas collecting pipe to the gas jet nozzle at the bottom of the reaction vessel In, those having a line gas analyzer for measuring the material density ingest a portion of the mixed gas.

  Therefore, when gasifying and supplying the liquid raw material, the raw material concentration in the mixed gas sent to the pipe by the online gas analyzer is measured, and if the measured value is different from the desired concentration, the difference By adjusting the heating temperature of the raw material tank and the flow rate of the sweep gas so as to eliminate the above, the gasification supply amount of the liquid raw material can be adjusted to a desired one, and such sampling is performed during the coating layer forming process. If the steps of measurement and feedback control are performed at appropriate time intervals, the gasification supply amount of the liquid raw material can be adjusted to be constant and a uniform coating layer forming state can be ensured.

  That is, in the present invention, when methyltrichlorosilane, which is a liquid raw material for forming the third coating layer, is gasified and supplied, the vapor of the liquid raw material taken into the sweep gas bubble in the raw material tank is recovered on the liquid surface. Is sent to the gas collecting pipe, where it is mixed with the flowing gas, mixed, and sent to the pipe communicating with the reaction vessel. A part of the mixed gas is sampled by an on-line gas analyzer on the way, and methyltrichlorosilane Since the concentration is measured, based on the results, if the concentration is lower than the desired concentration, the heating temperature is increased or the sweep gas flow rate is increased to increase the amount of steam generated by bubbling. Adjustment can be performed to reduce the amount of steam generated by bubbling by lowering the heating temperature or reducing the sweep gas flow rate. Therefore, if these sampling, measurement, and feedback control processes are performed at appropriate time intervals throughout the third coating layer forming process, the gasification supply amount of methyltrichlorosilane is controlled to be constant, and the third coating layer is controlled. Is formed in a uniform film thickness, and high quality coated fuel particles can be obtained.

  Note that the adjustment of the heating temperature and the adjustment of the sweep gas flow rate based on the measurement result by the online gas analyzer as described above can be performed manually, but it is quick to adopt a configuration in which adjustment is performed by automatic control. It is desirable to realize more stable gasification supply of liquid raw material by feedback control. That is, the automatic control unit may control the heating operation mechanism of the heating means or the supply amount adjustment mechanism of the sweep gas based on the measurement result by the analyzer.

  Further, since the same kind of flowing gas as hydrogen gas or the like is usually used as the sweep gas, a part of the flowing gas from the flowing gas supply source to the gas collecting pipe may be branched and used as the sweep gas. . In this case, the sweep gas flow rate may be adjusted by adjusting the flow rate of the branched flow gas.

  As a specific analysis method of an on-line gas analyzer, a gas chromatograph can be mentioned as a simple one, but it is not limited to this, and any mechanism that can measure the concentration of methyltrichlorosilane can be widely used. There are no particular restrictions.

  In the apparatus for producing coated fuel particles for a HTGR according to an embodiment of the present invention, gasification supply for gasifying and supplying methyltrichlorosilane (referred to as MTS) which is a liquid raw material for the third coating layer of the coated fuel particles The means is shown in the schematic configuration diagram of FIG. 1 as an example in which the adjustment of the gas supply amount is performed by automatic control.

  In this apparatus, the acetylene gas supply source 21 as the first coating raw material and the coating raw material gas supplied from the propylene gas supply source 22 as the second and fourth coating raw materials correspond to each other while being switched with each other. In the coating layer forming step, the gas is fed to the gas collecting pipe 5 where it is mixed and mixed with the flowing gas sent from the supply source 3 of the flowing hydrogen gas and sent from the pipe 6 to the reaction vessel 20 side. A gas injection nozzle (not shown) mounted on the inside of the reactor is injected and supplied into the reaction vessel 20 and includes an MTS gasification supply means 1 as a supply source of the coating material gas for the third coating layer.

  The gasification supply means 1 includes a raw material tank 2 in which a liquid raw material MTS is accommodated, and a nozzle 7 that introduces a sweep gas to a predetermined depth position in the liquid raw material MTS and discharges bubbles. In this embodiment, a part of the flowing gas is used as the sweep gas. That is, by introducing a pipe 4x branched from the flowing gas pipe 4 from the flowing hydrogen gas supply source 3 to the gas collecting pipe 5 into the raw material tank 2, and connecting the nozzle 7 to the tip of the branch pipe 4x, the reaction vessel 20 A part of the flowing gas sent to is used as a sweep gas.

  In this gasification supply means 1, the MTS vapor is taken into the bubble of the sweep gas by bubbling the sweep gas in the liquid raw material MTS, and is recovered as MTS vapor gas from the liquid surface in the raw material tank 2 by the recovery pipe 11. And sent to the gas collecting pipe 5. In this gas collecting pipe 5, in the same manner as in the case of other coating raw material gas, it is mixed and mixed with the flowing gas and supplied to the reaction vessel 20 through the pipe 6 as a mixed gas.

  The flow rate of the sweep gas is determined by the opening degree of the on-off valve 8 provided in the branch pipe 4x, and the adjustment is performed by the sweep gas supply amount adjusting mechanism 10 based on the value of the flow meter 9. Further, in the gasification supply means 1 of the present embodiment, the temperature of the liquid material itself is lowered by the heat of vaporization at the time of evaporation of the liquid material MTS. In order to compensate for this, the temperature of the liquid material MTS is kept constant. It is assumed that a temperature adjustment mechanism 12 is provided that heats the inside of the tank 2 with an electric heater 13 installed around the raw material tank 2 while measuring the temperature of the liquid raw material MTS with the measuring device 14.

  Since the supply amount of the MTS gas substantially depends on the amount of steam generated in the tank 2, the MTS gas supply amount also increases or decreases depending on the heating temperature level or the supply flow rate of the sweep gas (fluid gas).

  In this embodiment, an on-line gas analyzer 15 comprising a gas chromatograph device for sampling and analyzing a part of the mixed gas sent from the gas collecting pipe 5 at the nozzle upstream position of the pipe 6 is provided. Therefore, since the difference with respect to the desired raw material concentration can be determined from the MTS concentration measurement result of the MTS mixed gas by the analyzer 15, the temperature adjustment mechanism 12 or the sweep gas supply amount adjustment mechanism 10 is controlled accordingly to generate MTS vapor. The amount can be adjusted up or down to the desired raw material concentration.

  If such an operation of measuring the concentration of the sampling gas and adjusting the amount of MTS vapor generation based on the result is performed at predetermined time intervals during the third coating layer forming step, it can be performed over the step. The MTS gas supply amount can be maintained stably.

  If the above-described series of sampling, measurement, and feedback adjustment operations are performed periodically by automatic control, the MTS gas supply amount can be adjusted quickly and more reliably, and a more stable supply state of the source gas can be secured. it can. In this embodiment, sampling and analysis are performed every predetermined time by an on-line gas analyzer (gas chromatograph) 15 according to a command from an automatic control unit 16 comprising a computer, and measurement data is transmitted.

  The automatic control unit 16 obtains a difference between the measurement data and a raw material concentration in the mixed gas according to a predetermined MTS gas supply amount. When the measured value is lower than the set concentration, the sweep gas supply amount adjustment mechanism 10 to drive and control the on-off valve 8 to increase the opening and increase the supply flow rate of the sweep gas, or to instruct the temperature adjustment mechanism 12 to control the electric heater 13 and The MTS vapor generation amount is increased by increasing the heating temperature of the liquid material MTS.

  On the other hand, when the measured value is higher than the set concentration, the automatic control unit 16 instructs the sweep gas supply amount adjustment mechanism 10 to drive and control the on-off valve 8 to decrease the opening and reduce the supply flow rate of the sweep gas. By reducing, MTS vapor generation amount is reduced.

  As described above, according to the gasification supply means 1 of the liquid raw material in the present embodiment, in the third coating layer forming step, methyltrichlorosilane can be stably gasified while being adjusted to a certain desired concentration. Therefore, high quality coated fuel particles can be obtained with a uniform film thickness.

1 is a schematic partial view showing the configuration of a liquid material gasification supply means of a coated fuel particle manufacturing apparatus for a HTGR according to an embodiment of the present invention.

Explanation of symbols

1: Gasification supply means 2: Raw material tank MTS: Methyltrichlorosilane 3: Fluid hydrogen gas supply source 4: Fluid gas pipe 4x: Branch pipe 5: Gas collecting pipe 6: Pipe 7: Nozzle 8: On-off valve 9: Flow meter 10: Sweep gas supply amount adjustment mechanism 11: Recovery pipe 12: Temperature adjustment mechanism 13: Electric heater 14: Thermometer 15: Online gas analyzer 16: Automatic control unit

Claims (3)

A reaction vessel containing a large number of uranium dioxide fuel nuclei formed into spherical particles is heated while jetting and supplying a flowing gas and a coating material gas through a nozzle hole of a gas jet nozzle mounted on the bottom of the vessel. Thus, in the apparatus for producing coated fuel particles for a high-temperature gas reactor in which the fuel nucleus surface is coated with a vapor deposition layer of each coating material molecule by a thermal decomposition reaction of the coating material gas while flowing the fuel nucleus,
Means for gasifying and supplying the liquid raw material of the coating raw material gas, a gas collecting pipe for joining and mixing the fluid gas from the fluid gas supply source and the raw material gas from the coating raw material gas source, and the gas A pipe for sending the gas mixed in the collecting pipe to the nozzle,
The gasification supply means includes a raw material tank for containing the liquid raw material, a heating means for heating the liquid raw material in the raw material tank, a nozzle means for releasing a sweep gas in the liquid raw material, and a discharge from the nozzle means. The raw material vapor collected in the bubble while the generated sweep gas floats in the liquid raw material as a bubble is recovered as a mixed gas with the sweep gas on the liquid surface in the raw material tank and sent to the gas collecting pipe A gas extraction means,
The high-temperature gas coating further includes an on-line gas analyzer that ingests a part of the mixed gas sent from the gas collecting pipe at a predetermined nozzle upstream position of the pipe and measures a raw material concentration Fuel particle production equipment.   2. The high temperature according to claim 1, further comprising an automatic control unit that controls a heating operation mechanism of the heating unit or a supply amount adjustment mechanism of the sweep gas based on a measurement result by the online gas analyzer. Coated fuel particle manufacturing equipment for gas furnace. The coated gas particle manufacturing apparatus for a HTGR according to claim 1, wherein the online gas analyzer includes a gas chromatograph device.

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