JPS6337909B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a torus-type nuclear fusion device, and in particular to a heat shielding plate provided to protect a bellows portion forming a plasma container that confines high-temperature plasma from the plasma. The present invention relates to a torus-type nuclear fusion device that is suitable for use in equipped devices.

FIG. 1 shows a schematic configuration of a torus-type nuclear fusion device according to the prior art, which uses a magnetic field to confine plasma in a plasma container to cause a fusion reaction and extract thermal energy. As shown in the figure, a high-temperature plasma 26 is confined in a torus-shaped plasma container 12, and a plurality of toroidal coils 14 surround this plasma container 12 and are spaced at predetermined intervals in the torus direction 20. is located. On the other hand, in the center of the torus of the plasma container 12, a current transformer coil 1 constituting a poloidal coil is placed.
Further, in the outer circumferential direction of the toroidal coil 14, a vertical magnetic field coil 18 constituting a poloidal coil is arranged concentrically with the plasma vessel 12. The plasma container 12 is in the torus direction 2
It has bellows parts 22 at appropriate intervals at zero, and has a composite structure of a thick part 24 and a bellows part 22.
Normally, the bellows portion 22 is thinner than the thick portion 24, and has a structure in which the electrical resistance of the plasma container 12 in the torus direction 20 is sufficiently large. The toroidal coil 14 has a strong toroidal magnetic field (hereinafter denoted by symbol B) 28 for confining the high-temperature plasma 26 within the plasma container 12.
The current transformer coil 16 suddenly changes the current flowing through it over time to generate an electric field in the torus direction 20. This electric field causes plasma vessel 12
A plasma current (hereinafter referred to as _I
8 in the torus direction 20. Due to the Joule loss of this plasma current 30, the high temperature plasma 2
Get 6. Therefore, the high temperature plasma 26 needs to be confined as a plasma current 30. At this time, since the plasma current 30 has a torus shape, it is subjected to an electromagnetic force (hereinafter denoted by the symbol F _RP ) that tends to spread in the outer direction of the torus (hereinafter denoted by the symbol R) 31 . Therefore, it is necessary to generate a force in the inward direction of the torus that balances with this electromagnetic force F _RP to confine the high-temperature plasma 26. For this purpose, a vertical magnetic field (hereinafter denoted by the symbol B _ZO ) is applied to the vertical magnetic field coil 18. It is occurring in

On the other hand, as shown in detail in FIG.
This is provided in order to prevent the electric field in the torus direction 20 created by 6 from being electrically short-circuited. plasma container 1
2 confines high-temperature plasma 26 reaching hundreds of millions of degrees, so it is also required to function as a heat container.
In particular, the bellows portion 22 is thinner and is more difficult to cool than the thick portion 24. Furthermore, since the thermal resistance to heat conduction to the thick portion 24 is large, sufficient protection must be provided against heat input from the high temperature plasma 26.

Therefore, as shown in FIG.
The bellows part 22 attached to the high temperature plasma 2
A heat shielding plate 32 is installed to shield from heat from 6. The heat shielding plate 32 has a function of receiving heat input from the high temperature plasma 26 to the bellows portion 22 and quickly transmitting the heat to the thick portion 24. Also,
Since the heat shield plate 32 also comes into contact with the high temperature plasma 26, it must not interact with the high temperature plasma 26 to adversely affect the high temperature plasma 26. For this reason, the heat shield plate 32 is made of a material such as molybdenum, which has a high melting point and high thermal conductivity.

However, various problems arise even when trying to protect the bellows portion 22 using the heat shield plate 32 described above. This point will be explained below.

Figure 4 shows high temperature plasma 26 in plasma vessel 12.
It shows the principle of confinement. Usually, the electromagnetic force F _RP (F _RP ∝T _P ^Z ) due to the plasma current I _P and the electromagnetic force due to the interaction between the vertical magnetic field B _ZO and the plasma current I _P
Since it is in equilibrium with _fR , the high temperature plasma 26 is stably confined. Therefore, the magnitude of the vertical magnetic field B _ZO required for equilibrium is determined by the plasma current I _P , the term λ related to the temperature and pressure of the high-temperature plasma 26, and the main radius R of the high-temperature plasma 26, as shown in equation (1). _O ,
and the minor radius _aO is expressed as the relationship F.

B _ZO = F (I _P , λ, R _O , a _O ) ...(1) In order to keep the above R _O and a _O stable at constant values, B _ZO
must be set to a value that is temporally controlled according to changes in the high temperature plasma 26. Normally, when there is a change in the state of the high-temperature plasma 26 that is so high that it is impossible to follow B _ZO , the high-temperature plasma 26 is displaced toward the outside direction R of the torus or toward the inside direction of the torus, and the wall of the plasma vessel 12 or the heat Shielding plate 3
It collides with 2 and disappears.

Due to the above phenomenon, the distribution of magnetic lines of force around the plasma vessel 12 becomes as shown in FIGS. 5A to 5C. Figure 5 A is the distribution of the vertical magnetic field B _ZO (arrow shown)
, Fig. 5B shows the magnetic field line distribution (arrow shown) due to the plasma current I _P , and Fig. 5C shows the above-mentioned Fig. 5A and B.
The magnetic field distributions (arrows in the figure) are shown when the high-temperature plasma 26 is confined within the plasma container 12 by superimposing the magnetic fields. As is clear from the figure, the lines of magnetic force in the vicinity of the plasma container 12 form a so-called magnetic surface, so there are almost no magnetic field components that perpendicularly cross the wall surface of the plasma container 12. In a state where the plasma current I _P disappears rapidly from this state, the plasma vessel 1
The magnetic field distribution near 2 rapidly changes from the state shown in FIG. 5C to that shown in FIG. 5A. This change is caused by plasma vessel 1
2 When viewed from the wall, the vertical magnetic field B _ZO is the plasma current I _P
It appears to have risen in sync with the disappearance of the. Due to this rapid change in the vertical magnetic field B _ZO , the heat shield plate 3
2, an eddy current _Ie as shown in FIG. 6 is induced. Specifically, an eddy current _{I e} is induced by the interlinkage component B _o of the vertical magnetic field B _ZO with the surface of the heat shield plate. In this case, the component of the vertical magnetic field B _ZO interlinking with the heat shield plate 32
The following equation holds true between B _o and the poloidal angle θ regarding the mounting position of the heat shield plate 32.

B _o = B _ZO sinθ ……(2) I _e = G(B _o ) ……(3) Therefore, from equations (2) and (3), the magnitude of the eddy current I _e due to B _o is Mounting position of plate 32 and heat shield plate 3
It depends on the electrical conductivity of the second material. Also, eddy current
The magnitude of I _e is proportional to the electrical conductivity of the heat shield plate 32, and the orthogonal magnetic field component B _o to the heat shield plate 32 is
The poloidal angle θ shown in the figure is maximum at 90 degrees and 270 degrees, and conversely, the heat input from the plasma to the heat shield plate 32 becomes small. On the other hand, if the poloidal angle θ is 0 degrees,
and 180 degrees, the orthogonal magnetic field component B _o is at its minimum, and conversely, the heat input from the plasma is at its maximum.

For this reason, if the heat shield plate 32 is made of a highly thermally conductive material such as molybdenum as in the past, when the eddy current I _e increases when the plasma current I _P rapidly disappears, the interaction between the eddy current I _e and the toroidal magnetic field B There was a problem in that the electromagnetic force f _e became large, excessive mechanical stress was generated near the attachment part of the heat shield plate 32, and heat input from the plasma could not be effectively removed.

The present invention has been made in view of the above-mentioned points, and its purpose is to protect the bellows part forming the plasma container with a heat shield plate, but the heat shield plate has a large size. The torus-type fusion device is equipped with a heat shield plate that prevents the generation of eddy currents and the application of excessive stress to the mounting part, and that can effectively remove heat input from the plasma. It is on offer.

The present invention provides a plurality of heat shielding plates arranged adjacent to each other in the poloidal direction inside the bellows part forming the plasma container, and the electrical conductivity is Place a non-magnetic alloy with low
The intended purpose is achieved by arranging and forming a high melting point metal having higher electrical conductivity than the nonmagnetic alloy in the other parts. That is, in the present invention, the orthogonal magnetic field component to the heat shield plate, which causes eddy current generation, has a poloidal angle of 90
The heat input from the plasma to the heat shield plate is small when the poloidal angle is 90 degrees and 270 degrees.
The above-mentioned configuration was created by paying attention to the fact that the angle increases near 0 degrees and 180 degrees.

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings. Incidentally, the same reference numerals are used for the same parts as in the past.

FIG. 7 shows one embodiment of the present invention. Since its schematic configuration is almost the same as the conventional one, detailed explanation will be omitted here.

As shown in the figure, the plasma container 1 is also used in this embodiment.
A plurality of heat shielding plates 32 are arranged along the poloidal direction of the inner circumferential surface of the bellows portion forming the bellows portion 2 . In this embodiment, this heat shield plate 32
Two types of materials are used. That is, the larger the magnetic field component perpendicularly crossed by the vertical magnetic field B _ZO in the poloidal cross section of the plasma vessel 12, the greater the poloidal angle θ shown in the figure is 90
The heat shielding plate 32 (indicated by diagonal lines in the figure) near 270 degrees and 270 degrees is made of a high-strength non-magnetic alloy with low electrical conductivity and heat resistance. The heat shield plate 32 located at around 180 degrees is made of a metal with high electrical conductivity and high melting point, such as pure molybdenum. In other words, the magnitude of the eddy current is almost proportional to the electrical conductivity of the heat shield plate 32 and causes mechanical stress, but the orthogonal magnetic field component B _o to the heat shield plate 32 has a poloidal angle θ of 90 degrees and It reaches a maximum at 270 degrees, and the heat input from the plasma to the heat shield plate 32 becomes small. Therefore, as mentioned above, a high-strength nonmagnetic alloy, which is a material with low electrical conductivity, is used for the heat shield plate 32 where the poloidal angle θ is around 90 degrees and 270 degrees to suppress the generation of eddy currents. In addition to reducing the mechanical stress generated in the plasma, the heat removal is commensurate with the plasma heat input. on the other hand,
When the poloidal angle θ is 0 degrees and 180 degrees, the orthogonal magnetic field component B _o is minimum, and conversely, the heat input from the plasma is maximum. Therefore, the poloidal angle θ is 0
pure molybdenum, which is a metal with high electrical conductivity and a high melting point, is used for the heat shielding plate 32 near 180 degrees and 180 degrees.
It receives heat input from the plasma and quickly transfers it to the thick parts, improving heat resistance. The electrical conductivity of high-strength nonmagnetic alloys is several times to several tens of times lower than that of pure molybdenum, and it is desirable that the high-temperature strength be on the same level as pure molybdenum. It is also suitable for use due to its characteristics. In addition, when the electrical conductivity of the material used for the heat shield plate 32 is σ, and the poloidal angle at the mounting position is θ, the materials used for the heat shield plate 32 may be different so that the relationship σ∝1/sinθ is satisfied. However, its electrical conductivity may be changed.

According to this embodiment, the poloidal angle θ at the mounting position
By using a high-strength non-magnetic alloy for the heat shield plate 32 where the angle is around 90 degrees and 270 degrees, and by using pure molybdenum for the heat shield plate 32 where the poloidal angle θ is around 0 degrees and 180 degrees, the effect is improved. Since heat removal can be performed in a consistent manner, heat resistance is not reduced, and since eddy current generation is small, it is effective in reducing mechanical stress applied to the attachment portion of the heat shield plate 32.

According to the torus-type fusion device of the present invention described above, the plurality of heat shield plates arranged adjacently in the poloidal direction inside the bellows part forming the plasma vessel are arranged so that the vertical magnetic field in the poloidal cross section of the plasma vessel is at right angles. A non-magnetic alloy with low electrical conductivity is placed in the area where the magnetic field component crossing the area is large, and a metal with a higher melting point electrical conductivity than the non-magnetic alloy is placed in other areas. Even if the bellows part is protected by a heat shield plate, the generation of eddy current is small, so it is possible to reduce the excessive mechanical stress applied to the attachment part of the heat shield plate, and to reduce the heat input from the plasma. Since the large part acts as a heat shield plate with high thermal conductivity, it can effectively remove heat, and is very effective when used in this type of torus-type nuclear fusion device.

[Brief explanation of drawings]

Fig. 1 is a partially sectional plan view of a conventional torus-type fusion device, Fig. 2 is a plan view of the plasma container shown in Fig. 1, and Fig. 3 is a plan view of the plasma vessel shown in Fig. 1 and 2.
Figure 4 is a poloidal cross-sectional view of the plasma vessel showing the relationship between magnetic force distribution and electromagnetic force around the plasma vessel during plasma confinement; FIG. 5A is a distribution diagram of the vertical magnetic field _BZO acting on the plasma vessel, FIG. 5B is a distribution diagram of magnetic lines of force acting on the plasma vessel due to the plasma current I _P , and FIG. Figure 5B is a distribution diagram of magnetic lines of force when the magnetic fields overlap and high-temperature plasma is confined within the container. Figure 6 is a perspective view showing the eddy current flowing in the heat shield plate, the magnetic flux distribution in this area, and the electromagnetic force. Figure, 7th
The figure is a poloidal cross-sectional view of a plasma vessel showing the arrangement of a heat shield plate of a torus-type fusion device according to the present invention. 12... Plasma vessel, 14... Toroidal coil, 16... Current transformer coil, 18... Vertical magnetic field coil, 20... Torus direction, 22... Bellows part, 24... Thick wall part, 26... High temperature plasma,
28...Toroidal magnetic field, 30...Plasma current, 32...Heat shield plate, B _ZO ...Vertical magnetic field, θ...
...poloidal angle.

Claims (1)

[Scope of Claims] 1. A plasma vessel formed by alternately arranging thick parts and bellows parts in the torus direction and confining plasma therein, and surrounding the plasma vessel, and
a plurality of toroidal coils arranged at predetermined intervals in the torus direction, and arranged approximately concentrically with the plasma vessel outside the toroidal coils,
a torus-type nuclear fusion comprising a vertical magnetic field coil that generates a vertical magnetic field for confining the plasma, and a plurality of heat shielding plates arranged adjacent to each other in a poloidal direction inside a bellows portion of the plasma vessel; In the apparatus, in the heat shielding plate, a non-magnetic alloy with low electrical conductivity is arranged at a location where the vertical magnetic field crosses the poloidal cross section of the plasma vessel at right angles and has a large magnetic field component, and the non-magnetic alloy is disposed at other parts. A torus-type nuclear fusion device characterized by being formed by arranging a high-melting point metal with higher electrical conductivity. 2. The torus-type nuclear fusion device according to claim 1, wherein an austenitic high nickel alloy is used as the non-magnetic alloy, and pure molybdenum is used as the high melting point metal.