JP3006142B2 - Pellet injection device for fusion devices - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pellet injection device for a nuclear fusion device, and more particularly to a device for preventing the dissolution of solid hydrogen and pellets during a pellet injection operation and improving the pellet repetition injection performance of the injection device.

[0002]

2. Description of the Related Art A pellet injection device of a nuclear fusion device cools and solidifies a hydrogen isotope fuel of a fusion plasma to an extremely low temperature of about 10 K to produce a solid hydrogen pellet. This is a device that controls the density of plasma by repeatedly emitting it to the center of the fusion device.

At present, an air gun system for injecting pellets with a high-pressure gas is being actively developed. Pages 1113 to 1117 (J. Vac. Sci. Technol. A4 (3), 19
86, PP1113-1117). FIG. 2 shows a state in which the pellet is accelerated in the solid hydrogen generation / injection unit of the pellet injection device shown in the above-mentioned document. The nozzle 8 and the solid hydrogen generator 5 are cooled to an extremely low temperature of about 10 K in absolute temperature, and generate solid hydrogen 4 at the center of the nozzle 8. The accelerating gas 17 accelerates the pellets 3 punched and manufactured by the punching pipe 11, and the pellets 3 are accelerated in the punching pipe 11 and fly toward the fusion device at a speed of several km / s.

[0004]

However, in the prior art, the accelerating gas supply pipe 1 and the punching pipe 11 shown in FIG.
Since the heat of the pellet accelerating gas 17 flowing through the inside was not taken into consideration to enter into the cryogenic part such as the nozzle 8 and the solid hydrogen generating part 5, the temperature of the cryogenic part increased. By repeating the injection operation, the temperature rise is integrated, and eventually the temperature of the extremely low temperature portion reaches the liquefaction point (14K) of the solid hydrogen 4, the solid hydrogen 4 dissolves, and the injection operation of the pellet cannot be continued.

An object of the present invention is to prevent dissolution of solid hydrogen.
To improve the repetitive injection performance of solid hydrogen pellets
In Rukoto provide a pellet injection apparatus of a nuclear fusion device.

[0006]

In order to achieve the object of the present onset to achieve the above purpose
The feature of Ming is that the punched pipe is installed in the solid hydrogen generator.
An annular space is provided between the first tubular body and the first tubular body.
The gas supply pipe is arranged so as to form a space between the solid hydrogen
A second tubular body attached to the generator,
Are arranged so as to form an annular space between them.
You .

[0007]

An annular space is provided between the punched pipe and the first tubular body.
Is formed, and an annular space is provided between the gas supply pipe and the second tubular body.
Is used during injection of solid hydrogen pellets.
The amount of heat transferred from the accelerating gas to the solid hydrogen generator is
Is suppressed by the presence of Therefore, the solid hydrogen generator
Dissolution of the solid hydrogen generated in
The repetitive injection frequency of the kit can be increased.

[0008]

Embodiments of the present invention will be described below.

FIG. 10 shows how the density of the nuclear fusion device 25 is controlled by the pellet injection device 27. The hydrogen isotope plasma 26 undergoes a nuclear fusion reaction inside the nuclear fusion device 25, and as the reaction proceeds, the fuel density of the plasma 26 decreases, and new fuel supply is required. Then, the fuel gas is sent from the fuel gas storage device 28 to the pellet injection device 27 to form the solid hydrogen pellets 3, and the acceleration gas is sent from the acceleration gas storage device 29 to eject the pellets 3 at high speed. The pellet 3 ejected from the injector 27 is connected to the connecting pipe 3.
The fuel passes through the fusion device 25 and becomes new fuel for the plasma 26.

[0010] Figure 1 shows the structure of an embodiment of a solid hydrogen generation and injection of the pellet injection device according to the present invention, Ru der moment emitted pellets 3. Insulation performance of accelerating the gas supply pipe 1 and an injection pipe 2 and the gas exhaust unit 20 is enhanced.

[0011] Solid hydrogen 4 is generated inside a nozzle 8 at the center of the apparatus. Heat exchanger 9 and solid hydrogen generator 5
Keeps the cryogenic state by flowing liquid helium into the cooling pipe 6. The solenoid valve 7 is a high-speed opening / closing valve for sending the pellet accelerating gas 17 accumulated in the reservoir 10 to the accelerating gas supply pipe 1. Further, the punched pipe 11 has both a role of a mold for forming the pellets 3 and a role of a barrel for injecting the pellets 3. The gas exhaust part 20 is a part for exhausting the residual portion 22 of the accelerating gas remaining after the pellet injection operation to the outside of the apparatus. An inner pipe 13 is provided inside the acceleration gas supply pipe 1. The outer pipe 31 is made of a metal such as stainless steel, and maintains the mechanical strength of the acceleration gas supply pipe 1. On the other hand, the inner tube 13 is made of one tenth or less of a low heat conductive material such as a polyimide resin or a fiber reinforced resin, and flows an accelerating gas 17 into the internal space. Inner tube 13 and outer tube 3
1 is not in direct contact, and a heat insulating space is provided between the two. Similarly, the punched pipe 11 and the injection pipe 2 have a structure that does not directly contact. Further, the gas exhaust unit 20
Also, the surface in contact with the residual gas 22 is covered with a heat shield 19 made of a low thermal conductive material.

The operation of injecting pellets in this embodiment will be described below.

First, fuel hydrogen gas is fed into the nozzle 8. Next, the temperature of the heat exchanger 9 is adjusted to cool the nozzle 8 below the solidification temperature of hydrogen (absolute temperature 14 K), and the hydrogen gas filled therein is solidified by cooling. Further, the generated solid hydrogen 4 is pushed down by the piston 18 and pushed out to the connection portion of the acceleration gas supply pipe 1 and the pellet injection pipe 4 while being deformed in cross section to the size of the pellet at the lower part of the nozzle 8. The punched pipe 11 is slid to the left in the extruded solid hydrogen 4 to punch and produce a cylindrical pellet having a diameter of 1 to 5 mm and a length of 1 to 5 mm in the pipe 11. After the pellets are punched out, the electromagnetic valve 7 is opened and the high-pressure gas 17 stored in the reservoir 10 is sent to the accelerating gas supply pipe 1. The pellet 3 is accelerated in the punching pipe 11 and flies toward the fusion device at a speed of several km / s. After the completion of the pellet injection, the punched pipe 11 is slid to the right again to return to the original position. The residual gas 22 remaining in the accelerating gas supply pipe 1 and the punching pipe 11 is exhausted to the outside through the gas exhaust part 20, and the solid hydrogen 4 is pushed out again by the piston 18 so as to be ready for the next injection operation.

By repeating the above series of operations, the pellets 3 are repeatedly injected.

The state of heat penetration of the accelerating gas 17 during the pellet injection operation using this embodiment will be described with reference to FIG. FIG. 3 is an enlarged view of the central portion of FIG.

First, heat penetration during pellet injection will be described.

In FIG. 3, the accelerating gas 17 is supplied to the nozzle 8
And the inner pipe 13 not directly in contact with the solid hydrogen generator 5
And into the punched pipe 11 to accelerate the pellet 3. While the pellet 3 is accelerating, the inner pipe 13 and the punched pipe 11 receive heat from the accelerating gas 17 passing therethrough. However, since the inner tube 13 is made of a low heat conductive material, the heat conduction phenomenon from the heat receiving portion of the inner tube 13 to the extremely low temperature portion such as the nozzle 8 and the solid hydrogen generator 5 is suppressed. In the prior art, the outer tube 31 of the accelerating gas supply tube 1 is a portion through which the gas 17 passes and at the same time, a portion that maintains the mechanical strength of the tube. Therefore, the material is stainless steel or the like to maintain the mechanical strength. Needed. In the present embodiment, since the inner tube 13 has enough strength to withstand the pressure of the gas 17, a fiber reinforced resin (FRP) of stainless steel having only one-tenth of the thermal conductivity is sufficient.
Alternatively, a polyimide resin or the like having a low thermal conductivity of 1/100 or less can be used. That is, as compared with the related art, it is possible to enhance the heat insulation in accordance with the thermal conductivity of each of the materials used. Further, by providing the heat insulating gap portion 14 between the inner tube 13 and the outer tube 31, the heat conduction phenomenon to the cryogenic portion is structurally suppressed. The same effect can be obtained by providing the heat insulating gap 14 between the punched pipe 11 and the injection pipe 2.

In the present embodiment, the temperature of the inner pipe 13 of the accelerating gas supply pipe 1 and the heat receiving portion of the punching pipe 11 rise because the heat of the accelerating gas 17 is hard to escape.
However, since the inner tube 13 is not a portion that is in direct contact with the solid hydrogen 4, even if the temperature rises due to the heat of the acceleration gas 17, it does not cause the solid hydrogen 4 to dissolve. Further, with respect to the punched pipe 11 as well, the time required for the pellet 3 to pass is usually as short as about 1 ms, and during the passage, the pellet 3 in contact with the punched pipe 11 evaporates to form a heat insulating layer. For this reason, the temperature rise of the punched pipe 11 does not cause the pellet 3 to be dissolved. That is, heat is applied to the inner pipe 13 and the punched pipe 1
Even if it stays at 1, there is no problem in the injection operation of the pellet.

As described above, in this embodiment, it is possible to reduce the amount of heat that the accelerating gas 17 incurs during the injection of pellets from the heat energy receiving portion to the cryogenic portion. By reducing the amount of heat penetration, heat can be removed from the cryogenic part within the range of the conventional cooling capacity or a slight improvement in performance, and therefore, the temperature rise of the solid hydrogen 4 can be prevented.

Next, the heat penetration after the completion of the pellet injection will be described.

The punched pipe 11 returns to its original position,
The residual gas 22 fills the gas exhaust unit 20. Also in this case, since the heat shield 19 serves as a heat receiving unit, the amount of heat entering the solid hydrogen generation unit 5 is reduced. Compared to the prior art in which the surface of the heat receiving portion is made of copper and a copper alloy, the heat conductivity of the surface of the heat receiving portion of the heat shield 19 according to the present embodiment is:
When the fiber reinforced resin is used, it can be reduced to 1/100, and when it is a polyimide resin, it can be reduced to 1/1000 or less. Therefore, the amount of heat penetration due to the residual gas 22 can be prevented to a negligible level as compared with the conventional case, and the heat penetration can be removed by the conventional cooling technique as in the case of pellet injection.

From the above effects, by using the present embodiment in the pellet injection device, it is possible to suppress the temperature rise of the solid hydrogen generator 5 during the entire pellet injection operation and prevent the solid hydrogen 4 from being dissolved. As a result, it is possible to achieve an improvement in the frequency of repeated injections and the number of injections as compared with the related art.

The structure of an acceleration gas supply pipe 1 and a pellet 2 injection pipe according to another embodiment of the present invention will be described with reference to FIGS.

In FIG. 4, in addition to forming the inner tube 13 from a low heat conductive material, the heat insulating gap portion 14 is further evacuated or filled with a low heat conductive material or filled with a refrigerant such as liquid helium. By doing so, the heat insulating effect of the acceleration gas supply pipe 1 can be enhanced.
The heat conduction from the inner tube 13 to the outer tube 31 can be almost completely prevented by positively setting the heat insulating gap portion 14 to a vacuum state. Further, even if a low heat conductive material is filled or a space is simply provided, a heat insulating performance of one tenth or less than that of conventional metal heat conduction can be achieved. Further, heat can be removed by charging a refrigerant such as liquid helium or circulating the refrigerant with the outside world. As a result, the path through which the heat received from the accelerating gas 17 by the inner pipe 13 of the accelerating gas supply pipe 1 enters the cryogenic portion is limited to the portion of the pipe stopper 12 in FIG. It is possible. By using a low thermal conductive material for the stopper 12, it is possible to further enhance the heat insulating effect. As a result, heat intrusion from the accelerating gas supply pipe 1 to the cryogenic parts such as the solid hydrogen generator 5 and the nozzle 8 can be prevented. It can be further suppressed.

Also in FIG. 5, the heat insulating effect can be enhanced by forming the punched pipe 11 from a low heat conductive material. As a result, the intrusion path through which the heat received from the gas is transmitted to the cryogenic portion is limited to the tip end for punching out the solid hydrogen 4, and the same heat insulating effect as the accelerating gas supply pipe 1 can be achieved.

From the above results, the combination of the two embodiments can prevent the solid hydrogen 4 from dissolving due to heat penetration from the accelerating gas 17.

FIG. 6 shows another embodiment of the present invention. This embodiment aims to prevent the heat obtained by the inner tube 13 from entering the cryogenic portion via the stopper 12 in addition to the embodiment of FIG. In the figure, the stopper 12 is the inner tube 1
3 and not in contact with the outer pipe 31 of the acceleration gas supply pipe 1. A heat insulating gap 14 is also provided between the stopper 12 and the outer tube 31. Therefore, the heat that has entered from the heat receiving portion of the inner tube 13 stays in the stopper 12, and heat conduction to the outer tube 31 and the cryogenic portion can be prevented. With this structure, it is impossible to fill the heat insulation gap with the refrigerant, but it is possible to apply vacuum heat insulation, so that heat can enter the cryogenic part by combining vacuum heat insulation with the above-mentioned heat retention effect. Can be further suppressed as compared with FIG.

FIG. 7 shows another embodiment of the present invention. In this embodiment, in addition to the structure shown in FIG. 3, by providing the outer heat insulating gap 23 between the acceleration gas supply pipe 1 and the pellet injection pipe 2, the nozzle 8, and the solid hydrogen generator 5,
The heat penetration of the acceleration gas 17 is further suppressed. The outer heat insulating gap portion 23 has a sufficient heat conductivity between the outer tube 31 and the pellet injection tube 2 and the cryogenic portion in the prior art, even if it is simply a vacuum heat insulating space or is filled with a low heat conductive material. It can be reduced to one or less. That is, heat that has entered the outer pipe of the acceleration gas supply pipe 1 and the injection pipe 2 can be retained without being sent to the cryogenic part. Further, for example, by filling the heat insulating gap portion 14 with a refrigerant, not only the heat of the inner tube 13 but also the heat of the stopper 12 and the outer tube 31 joined to the stopper 12 are removed before entering the cryogenic portion. be able to.

FIG. 8 shows another embodiment of the present invention. The purpose of this embodiment is to remove not only the heat obtained from the acceleration gas supply pipe 1 but also the heat obtained by the punching pipe 11 by flowing a refrigerant from the outside. In addition to the structure shown in FIG. 8, a cooling pipe 6 is provided outside the acceleration gas pipe 1 and the injection pipe 2. The tip of the accelerating gas supply pipe 1 directly joins the inner pipe 13 and the outer pipe 31 to improve heat conduction. Further, the punched pipe 11 and the injection pipe 2 are also brought into direct contact to improve heat conduction. With this structure, even if the temperature of the accelerating gas pipe 1, the stopper 12, and the punched pipe 11 rise during injection of the pellet, the coolant flows through the cooling pipe 6 to take advantage of the good thermal conductivity of the solid. It has a structure that can be cooled. According to the present embodiment, most of the heat from the heat receiving section to the cryogenic section can be removed.

FIG. 9 shows another embodiment of the present invention. The purpose of this embodiment is to also remove the heat of the residual gas 22 that has entered the heat shield 19 to the outside. A coolant reservoir 24 is provided between the heat shield 19 made of a low thermal conductivity material and the solid hydrogen generator 5. The refrigerant sump 24 has a structure that can store liquid helium and the like and can be injected from the outside. By circulating the refrigerant during the pellet injection operation, the heat of the heat shield 19 received from the residual gas 22 can be removed to the outside.

[0031]

According to the present invention, heat penetration of the accelerating gas into the solid hydrogen generation section can be suppressed, and dissolution of solid hydrogen during the pellet injection operation can be prevented. Therefore, it is possible to repeatedly inject hundreds to thousands of pellets required for a practical furnace having an operation time of several hundred seconds. In addition, it is possible to increase the total amount of gas release required for injection, thereby realizing higher-speed injection of pellets. Furthermore, since the number of repeated injections can be increased,
Small pellets can be supplied to the furnace with high frequency, and more stable plasma density control than in the past can be achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a solid hydrogen generation / injection section showing one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a solid hydrogen generation / injection section of a conventional pellet injection device.

FIG. 3 is a sectional view of an embodiment of the pellet injection device of the present invention.

FIG. 4 is a sectional view of an accelerating gas pipe according to an embodiment of the present invention.

FIG. 5 is a sectional view of an injection tube according to an embodiment of the present invention.

FIG. 6 is a sectional view of a second embodiment of the pellet injection device of the present invention.

FIG. 7 is a sectional view of a third embodiment of the pellet injection device of the present invention.

FIG. 8 is a sectional view of a fourth embodiment of the pellet injection device of the present invention.

FIG. 9 is a sectional view of a fifth embodiment of the pellet injection device of the present invention.

FIG. 10 is an explanatory diagram showing a state of plasma density control of a nuclear fusion device by a pellet injection device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Acceleration gas supply pipe, 2 ... Pellet injection pipe, 5 ... Solid hydrogen generation part, 8 ... Nozzle, 12 ... Stopper, 13 ... Inner pipe,
14: adiabatic gap, 17: accelerating gas, 19: heat shield, 20: gas exhaust, 23: outer adiabatic gap.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model 2-110897 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G21B 1/00

Claims (1)

(57) [Claims] 1. A solid hydrogen generator cooled by a refrigerant and solid hydrogen pellets produced by punching out the solid hydrogen generated by the solid hydrogen generator, and the solid hydrogen pellets are guided to the nuclear fusion device during injection. A punching pipe, a gas supply pipe for supplying an accelerating gas into the punching pipe during injection of the solid hydrogen pellets, and a gas exhaust unit for discharging the accelerating gas remaining in the solid hydrogen generator after the injection of the solid hydrogen pellets In the pellet injection device for a nuclear fusion device, the punched pipe is disposed in a first tubular body attached to the solid hydrogen generator, so as to form an annular space with the first tubular body. The gas supply pipe is arranged in a second tubular body attached to the solid hydrogen generating section so as to form an annular space between the gas supply pipe and the second tubular body. And a pellet injection device for a fusion device.