JPH0246918B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tritium permeability prevention structure using liquid metal in core structural materials such as the first wall and diverter/limiter of a nuclear fusion reactor.

[Conventional technology]

A nuclear fusion reactor, for example, a tokamak type, in which a current is passed through the plasma created along the circumference, and the force of the poloidal magnetic field generated by this current confines the plasma in a torus shape to cause a nuclear fusion reaction. In a nuclear fusion reactor, as shown in FIG. 1, an inner blanket 2, an outer blanket 2', an inner shield 3, an outer shield 3', a toroidal magnetic field coil 4, a poloidal magnetic field coil 5, etc. are installed around a doughnut-shaped plasma 1. is located. In addition, high energy and electrically neutral particles are added to the plasma 1.
Neutral particle injection heating device (not shown) serves to increase the temperature of plasma 1 by imparting its energy to plasma 1. The exhaust device 7 exhausts impurities such as atoms and molecules out of the system, and the shape of the magnetic field lines around the plasma 1 is devised to prevent the plasma escaping to the outside from directly hitting the wall of the inner blanket 2. A diverter/limiter 6 etc. is installed to guide the flow.

The tokamak-type fusion reactor is roughly constructed as described above, and the inner and outer blankets 2 and 2' react with the lithium compound in the container and neutrons generated by the fusion reaction to react with the neutrons of the fusion reactor. The function of producing tritium (tritium) as fuel, the function of converting the energy of the neutrons into thermal energy, the inner and outer shields 3,
Along with 3', it has the function of shielding neutrons.
It is one of the important pieces of equipment in a tokamak-type fusion reactor.
The surfaces of the core structural materials surrounding the plasma 1, such as the first wall forming the plasma-side walls of the inner and outer blankets 2 and 2' and the diverter/limiter 6, are protected against fast neutrons and helium particles leaking from the plasma 1. Subject to severe particle loads, heat loads, etc. In particular, charged/neutral tritium particles have high permeability in high-temperature core structural materials, are radionuclides, and are normal structural coolants.
Since it is an isotope of H ₂ O and D ₂ O, it is difficult to separate and remove it from the coolant, so it is necessary to prevent it from leaking into the coolant as much as possible.

Conventionally, core structural members such as the first wall are provided with a coolant flow path 10 at the rear of the plasma side wall 8, as shown in _{FIG .} etc., to maintain the material temperature of the plasma side wall 8 below the allowable temperature under the high heat flux of 14 MeV fast neutron flux and charged/neutral tritium flux emitted from the core plasma 1. This is how it was done.

[Problem to be solved by the invention]

By the way, some of the charged/neutral tritium particles incident on the surface of the core structural material diffuse and leak directly into the coolant 9 in the coolant flow path 10.
The tritium concentration inside the vehicle increased as the vehicle was operated, posing a safety problem.

The present invention has been made to solve such problems, and provides a tritium permeation prevention structure for the core structural material of a nuclear fusion reactor, which can prevent the temperature of the core structural material from increasing and reduce the amount of tritium permeated and leaked into the cooling system. We intend to donate the following.

[Means to solve the problem]

In order to solve the above problems, the tritium permeation prevention structure of the core structural material of a nuclear fusion reactor according to the present invention has a narrow fixed space between the front face part on the plasma side of the core structural material and the rear face part having a coolant flow path. and filling the space with liquid metal to form a liquid metal layer,
A large hollow plenum portion for temporarily storing tritium is provided above the liquid metal layer, and a tritium-permeable diaphragm is provided on the open surface of the plenum portion on the plasma side.

[Effect]

According to the tritium permeation prevention structure of the core structure material of a fusion reactor according to the present invention configured as described above, charged/neutral tritium particles incident on the surface of the core structure material are prevented from flowing into the coolant in the coolant flow path. It is captured by the liquid metal layer before it diffuses in. The captured tritium diffuses and moves up in the liquid metal where the tritium solubility is low and the tritium diffusion coefficient is high, and enters the plenum section provided above the liquid metal. Tritium that enters the plenum is temporarily stored, and then passes through a tritium-permeable diaphragm installed on the plasma-side opening and is released to the high-vacuum plasma side. In this way, diffusion and leakage of tritium into the coolant in the coolant flow path is greatly reduced, and an increase in tritium concentration in the coolant is suppressed.

In addition, since liquid metal has high thermal conductivity, the heat removal performance of the core structural material is prevented from deteriorating.

〔Example〕

An embodiment of the tritium permeation prevention structure of the core structural material of a fusion reactor according to the present invention will be described. In FIG. 3, 8' is the first wall or the wall on the plasma side of the core structural material such as the diverter/limiter, and a narrow space is created between the front part and the rear part having the coolant flow path 10. Set up Na, within that space.
Liquid metal layer 11 is filled with liquid metal 12 such as Pb.
is formed. A large hollow plenum part 13 for temporarily storing tritium is provided above the liquid metal layer 11, and the open surface of the plenum part 13 on the plasma side is made of a thin film of Pd, Pd alloy, etc. with a large permeability coefficient. A tritium permeable diaphragm 14 is provided. In the coolant flow path 10, H ₂ O or
A coolant 9 such as D ₂ O is flowing to cool the core structural materials.

The operation of this embodiment configured in this way will be explained. Charged/neutral tritium particles incident from the surface of the plasma-side wall 8' of the core structural material repeatedly collide with atoms of the constituent metals of the core structural material and fly until they lose all of their energy. The tritium that has reached this flight distance diffuses toward the liquid metal layer 11 side where the concentration is lower due to the difference in tritium concentration between the part where the flight distance has been reached and the liquid metal layer 11,
It is captured there. Since the liquid metal 12 has a low tritium solubility and a large tritium diffusion coefficient, the tritium captured in the liquid metal layer 11 diffuses and migrates in the liquid metal 12 and rises to the plenum provided above the liquid metal layer 11. Enter section 13. The tritium that has entered the plenum section 13 is temporarily stored, and then passes through a tritium-permeable diaphragm 14 made of a thin film of Pd, Pd alloy, etc. with a large permeability coefficient and installed on the opening surface on the plasma side, and is kept in a high vacuum. Emitted to the plasma side. Even if the liquid metal 12 undergoes thermal expansion during furnace operation, the load on the permeable diaphragm 14 is reduced by the hollow plenum part 13, and the presence of the plenum part 13 prevents the liquid metal 12 from directly touching the permeable diaphragm. .

In this way, diffusion and leakage of tritium into the coolant 9 in the coolant flow path 10 is significantly reduced, and an increase in tritium concentration in the coolant 9 in the coolant flow path 10 is suppressed.

Furthermore, since the liquid metal 12 has high thermal conductivity, the heat removal performance of the core structural material is prevented from deteriorating.

〔Effect of the invention〕

As described above, according to the tritium permeation prevention structure of the core structural material of a fusion reactor according to the present invention, charged/neutral tritium particles entering the core structural material diffuse and leak into the coolant in the coolant flow path. The captured tritium is captured by the liquid metal layer before it is released, and the captured tritium diffuses through the liquid metal and rises, entering the plenum where it is temporarily stored. Since tritium is released into the high-vacuum plasma side through the diaphragm, the diffusion and leakage of tritium directly into the coolant in the coolant flow path is significantly reduced, and the tritium concentration in the coolant during reactor operation is reduced. In addition, since the liquid metal has high thermal conductivity, the heat removal performance of the core structural material is prevented from deteriorating, and as a result, a core structural material that is superior in terms of functionality and safety can be obtained.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view schematically showing a tokamak-type fusion reactor, Fig. 2 is a schematic cross-sectional view of a conventional reactor core structural material, and Fig. 3 is an example of the tritium permeation prevention structure of the core structural material of the present invention. FIG. 8'...Wall on the plasma side of the core structural material, 9...
Coolant, 10... Coolant channel, 11... Liquid metal layer, 12... Liquid metal, 13... Plenum part, 1
4...Permeable diaphragm.

Claims (1)

[Claims] 1. A narrow space is provided between the front surface of the core structural material on the plasma side and the rear surface having a coolant flow path, and the space is filled with liquid metal to form a liquid metal layer. Prevention of tritium permeation in a core structural material of a nuclear fusion reactor, characterized in that a large hollow plenum part for temporarily storing tritium is provided above the layer, and a tritium permeable diaphragm is installed on the plasma side opening of the plenum part. structure.