JPS61194389A - Blanket for nuclear fusion device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a blanket for a nuclear fusion device, and particularly to a blanket capable of producing tritium in plasma in an amount greater than the amount of tritium consumed in a nuclear fusion reaction.

[Background of the invention]

Various types of nuclear fusion devices have been considered depending on the plasma confinement method, and one of the most commonly used nuclear fusion devices is a tokamak type fusion device.

The tokamak type nuclear fusion device is constructed as shown in FIG. That is, the plasma 1 is connected to the toroidal coil 6
It is configured to be confined within the vacuum vessel by magnetic fields such as a toroidal magnetic field, a perpendicular magnetic field, and a quadrupole magnetic field generated by the voloidal fill 7, and on the outside of the plasma 1, so as to surround it, There is a third wall 2 which directly receives the thermal radiation from the plasma 1 and collisions of particles, and also plays the role of extracting the energy of these thermal radiations and particles. Outside, surrounding it, is the production of tritium, one of the fuels for nuclear fusion reactions,
Blanket 3 has the role of converting the kinetic energy of neutrons released from the plasma into thermal energy with 80% of the energy generated by the fusion reaction.
is installed. A shield 5 is installed outside the blanket 3 to surround it and prevent leakage of neutrons and gamma rays. In addition, a diverter 4 is installed in the opening of the blanket 6 to neutralize ionized particles in order to remove impurities from the plasma 1.

The neutralized particles containing impurities collected by the diverter 4 are exhausted to the outside from the exhaust duct 8. Since the plasma 1 having a non-circular cross-sectional shape as shown in the figure is unstable with respect to its vertical position, the vertical position of the plasma 1 must be controlled. A shell coil 9 is installed in order to control the growth rate to a speed that allows plasma position control, such as a growth rate that is unstable in the vertical direction.

The inside of the blanket 3 is filled with a tritium breeder material made of lithium or a lithium compound, and tritium is produced by reacting neutrons with an energy of 14.1 MgV generated by a nuclear fusion reaction from the plasma 1 with lithium. do. In a nuclear fusion reaction, when one tritium is consumed, one neutron is generated.
The number of tritium that can be produced by reacting with one 14.1 MgV neutron lithium is called the "tritium breeding ratio".
It can be defined as The tritium breeding ratio is used as a quantity that indicates the tritium production capacity of the blanket.

In a nuclear fusion device that extracts energy through a nuclear fusion reaction between deuterium and tritium, tritium is a nuclide that does not exist in nature, so it is necessary to produce at least the same amount of tritium in a blanket as is consumed.

That is, it is necessary to provide a blanket e that can exceed 1.0 as a tritium breeding ratio. As lithium, which is a tritium breeder, natural lithium contains '
It contains 92.6% Ls and 74% 'Li, the former contains neutrons and 'Li (n, n'a) 'l', and the latter contains 'Li(s.

α) Reacts with T. Here, % y n' is a neutron with different energy, α is an alpha particle, and T is not tritium. In the former reaction, one tritium is produced and at the same time one neutron is produced.

Since these neutrons undergo Li k reaction again to generate tritium, there is a possibility that the tritium breeding ratio will exceed 1.0. In other words, the 7Li reaction may cause the tritium breeding ratio to exceed 1.0. The latter reaction has a large reaction cross section for thermal neutrons, and the more the neutron is slowed down,
-Handle r-Kin1 →1 threshold approximately 2 M
Since the reaction has 6 V, the 1 generated in the nuclear fusion reaction
4.1 MgV neutrons are released by the protective material of the first wall 2, such as silicon carbide (810), the structural material such as stainless steel (SUS), and the coolant such as light water (H2O). When the reaction rate is slowed down, the reaction rate decreases, making it difficult for the tritium breeding ratio to exceed 1.0.

Therefore, in the blanket of a conventional fusion device,
Before reacting neutrons generated in a nuclear fusion reaction with lithium, they are reacted with a substance such as lead or beryllium that has a large cross section for (n + 2n) reactions and a relatively small neutron absorption cross section, and the neutrons are By reacting with lithium after multiplication, the tritium multiplication ratio is 1.
A method is adopted that aims to exceed 0. (K, Mα
kiand 'I'.

0kazaki i Effect of Blank
et 5structure on Tritium Br
eeding Ratio in Fusion Re
actors.

Nuclear Technology / Fusi
on, Vol. 4 (Nov.

1983) P468).

In this method, the (n, 2n) reaction depends on the threshold, which is 1.8 MgV for beryllium and 8 MgV for other nuclides.
Since it has a threshold value of MeV to more than ten M m V , the neutron multiplication layer 11 is installed in a region close to the plasma 1, as shown in FIG. In addition, in the spectrum of neutrons generated by the (n, 2s) reaction in the neutron multiplication layer 11 and 4-star neutrons that undergo elastic or inelastic scattering, the energy above the threshold of the 'Ls (n + 2 n) reaction The proportion of neutrons with neutrons is reduced to a fraction of that in the case where the neutron multiplication layer 11 is not installed. Therefore, the contribution of 'Ls to the tritium breeding ratio is reduced from more than 20 to If'% in the absence of a neutron multiplication layer.

Therefore, in order to increase the tritium production reaction rate of 6Li, it is better to use natural lithium as it is as a tritium breeder (by concentrating LS to 50% to 90% and increasing the so-called "enrichment"). Lithium is used alone or in the form of a lithium compound (for example, Li20).

In addition, in FIG. 7, the blanket container 10 is made of a structural material such as stainless steel, and has a tritium breeding region 12.
is made of a tritium breeding material such as Li2O. In this region, the heat generated by the moderation of neutrons and the tritium production reaction between neutrons and lithium is cooled by the tritium breeding region cooling channel 16, and is then transferred from the tritium breeding region cooling header 14. , through the coolant outlet nozzle 16 to the outside. Light water (Hz O) or the like is used as the coolant, and it flows in from the coolant inlet nozzle 15. Further, tritium generated in the tritium breeding region 12 is carried outside using helium gas as a carrier gas. Helium gas flows in from the helium gas inlet nozzle 79, passes through the space between the lower blanket container 10 and the helium gas can 17, and enters the tritium breeding region 12 from the helium gas inlet hole of the lower helium gas can 17. ,
The pellet-like tritium breeder material passes through the gap between the tritium breeder materials, mixes with the tritium gas generated in the tritium breeder region 12, passes through the helium gas outlet hole 18 of the helium gas can 17, and connects to the upper blanket container 10 and the helium gas can 17. through the space of helium gas outlet nozzle 2
0 and is carried outside.

For such a blanket, the calculation results of the tritium breeding ratio using a one-dimensional cylinder model show that the neutron multiplication layer 1
When lead is used as 1, the maximum tritium breeding ratio is 1.60 when the thickness is 10 mm, and when beryllium is used, the maximum tritium breeding ratio is 1.27 when the thickness is 6 mm. becomes.

Here, the one-dimensional cylindrical model is a model of the core of a fusion reactor as follows. That is, in FIG. 6, an R coordinate is taken in the radial direction of the plasma with the center of the plasma 1 as the origin, and two axes are taken in the torus direction of the center of the plasma 1. A one-dimensional cylindrical model is an approximation of a torus by a right circular cylinder, assuming rotational symmetry around two axes. Therefore, in this model, the cross section of the plasma 1 is circular with its equivalent radius, and around it the -th wall 2
, the neutron multiplication layer 11, the tritium breeding region 12, and the shield 5 exist concentrically with uniform thickness, and in the core of an actual fusion device, a diverter is formed as shown in FIG. In the portion 4, the blanket 6 for tritium breeding cannot be installed, or even if it can be installed, the thickness of the blanket needs to be reduced to about half. If it cannot be installed, the tritium breeding ratio will decrease by 0.09, and even if it can be installed, the thickness will be about half, and since the diverter 4 is present between the blanket 3 and the plasma 1, the tritium breeding ratio will be 0.0.
It decreases by about 4. Further, as shown in FIG. 6, a shelf file 9 partially exists between the plasma 1 and the blanket 6. The shell coil 9 includes an aluminum alloy with a thickness of about 4J in a stainless steel container with a thickness of about 1 cm, and has a structure with cooling channels inside, and there are one on the top and one on the top.
Each width is about 1.8? FI partially covers the blanket 6 around the torus. The tritium breeding ratio thus reduced is approximately 0.11. The total of the above is approximately 0
．． 15 to 0.20 decrease. In addition, there are differences in the nuclear constants related to neutrons used to calculate the tritium breeding ratio, which causes differences in the tritium breeding ratio.
It is necessary to allow a margin of 0.05 for the tritium breeding ratio. Furthermore, the amount of tritium contained in a fusion device during steady operation is estimated to be 30~, and in order to produce this amount in 5 years, a margin of 0.05 is required for the tritium breeding ratio. be. Summarizing the above, the guide value for tritium breeding ratio based on one-dimensional cylinder calculation is 1.
25 to 1.30, and a blanket that can achieve this value or higher must be developed.

As mentioned above, the tritium breeding ratio according to the one-dimensional cylinder model in the conventional blanket shown in Fig. 7 has a maximum value when lead or beryllium is used in the neutron multiplication layer.
This value is close to the guide value of the tritium breeding ratio in a one-dimensional cylindrical model. However, in a blanket, so-called nuclear heating occurs due to the deceleration of neutrons and the interaction between gamma rays generated during the interaction between neutrons and matter and the matter. The nuclear heat generation density in the neutron multiplier layer is 6 to 8 W/cd with an average peak value of 2 to 3 W/4. The temperature of the neutron multiplier must be designed so that it does not exceed a certain value in order to ensure that the neutron multiplier does not melt or undergo chemical changes. Therefore, a cooling structure is required to remove the above-mentioned nuclear heat generation. When the neutron multiplication layer is thin, a few tens of meters thick, it is possible to keep the temperature below a predetermined temperature by cooling the neutron multiplication layer from both sides.

However, if the neutron multiplication layer is as thick as the enemy's country, sufficient neutron multiplication effect cannot be obtained, and the tritium multiplication ratio is 1.
It is difficult to exceed the guide value of the dimensional cylindrical model.

Therefore, as described above, a neutron multiplication layer having a thickness that maximizes the tritium breeding ratio is used. With such a thickness of the neutron multiplication layer, it is difficult to suppress the temperature of the neutron multiplication layer to a predetermined temperature by cooling from both sides. Therefore, as shown in FIG. 8, a neutron multiplication layer cooling channel 21 must be installed inside the neutron multiplication layer 11.

As shown in FIG. 9, the cross section of the neutron multiplier layer cooling channel 21 includes a cooling pipe 26 made of stainless steel or the like, and a light water (
HzO) or the like. However, the energy spectrum of neutrons generated by neutron multiplication reactions and moderated neutrons has a large proportion in the low energy region, so the low energy absorption region of stainless steel, etc., which is the structural material of the cooling pipe 23, Neutrons are absorbed, canceling out the neutron multiplication effect. Therefore, there is a drawback that it is difficult to design a tritium breeding ratio that exceeds the guide value of the one-dimensional model.

[Purpose of the invention]

An object of the present invention is to provide a blanket for a nuclear fusion device that can produce a large quantity of tritium, which is consumed in a nuclear fusion reaction.

[Summary of the invention]

To achieve such an objective, in the present invention, the cooling channel is configured by covering the cooling channel provided in the neutron multiplication layer disposed close to the plasma in the blanket with a tritium breeding layer. It is characterized by preventing the absorption of neutrons by structural materials and increasing the efficiency of using neutrons for tritium production, making it possible to produce nuclear tritium.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a diagram showing the concept of a blanket of a nuclear fusion device that is an embodiment of the present invention, and FIG.
It is an A sectional view. In the figure, 2 is the third wall facing the plasma, and 10 is a blanket container. In a region close to the plasma, there is a neutron multiplication layer 11 made of a material with a large neutron multiplication effect, such as lead or beryllium.

The neutron multiplication layer 11 has neutron multiplication layer cooling channels 21 for removing heat generated by nuclear heating.

The energy spectrum of neutrons and decelerated neutrons generated by a neutron multiplication reaction in the neutron multiplication layer 11 occupies a large proportion of the low energy portion. Therefore, the cooling pipe 23 constituting the neutron multiplier cooling channel 21
The neutrons are absorbed in the low energy absorption region of the material such as stainless steel, and the neutron multiplication effect is offset. In order to prevent this, in this embodiment, the neutron multiplier cooling channel 2
By surrounding the outside of the neutron multiplication layer cooling channel 21 with a tritium breeding layer 25, neutrons are is reacted with lithium in the tritium breeding layer 25 surrounding the neutron multiplication layer cooling channel, and is effectively used to generate tritium. Therefore, even if the cooling channel 21 is provided in the neutron multiplier layer 11, the tritium breeding ratio will not be reduced thereby. Note that since the energy spectrum of the neutrons generated and decelerated in the neutron multiplication layer 11 is low as described above, 'Lj(
s, α) The one-dimensional cross-sectional area becomes a region of several tens of barns or more, and the tritium breeding layer 25 surrounding the neutron multiplication layer cooling channel
The mean free path of the neutrons inside becomes small, about 0.5 distance. Therefore, the thickness of this layer 25 may be about 0.5j.

Bg (
s, 2n) The moderation cross section of high-energy neutrons above the IK response threshold j8MgV is less than 1 burn in lithium oxide (LjzO), which is a tritium breeder material, so the neutron increaser with a thickness of about 0.53 The tritium breeding layer 25 surrounding the double-layer cooling channel has the above-mentioned 1,8 MgV
It does not slow down most of the high-energy neutrons mentioned above, and has almost no effect on neutron multiplication reactions.

Tritium generated in the tritium breeding layer surrounding the neutron multiplication layer cooling channel is carried out to the outside as follows. That is, a portion of the helium gas that has flowed into the space between the lower blanket container 10 and the helium gas can 17 from the helium gas inlet nozzle 19 flows into the tritium breeding layer from the helium gas inlet hole of the lower helium gas can 17. It penetrates into the tritium breeding layer 25 and passes through the gaps in the pellet-like tritium breeding material, where it becomes mixed with tritium produced in the tritium breeding layer 25. This mixed gas flows out from the helium gas outflow hole 26 of the upper helium gas can 17 into the space between the upper blanket container 10 and the helium gas can 17, and flows out from the helium gas outflow hole 18 mentioned above, into the tritium breeding region. Together with the mixed gas of tritium and helium gas generated in step 12, the helium gas is carried out from the helium gas outlet nozzle 20.

The blanket shown in FIG. 1 which is an embodiment of the present invention having the configuration described above, the blanket shown in FIG. 7 which is a conventional example, and the cooling channel in the neutron multiplier layer of the blanket shown in FIG. 7 which is a conventional example. The tritium breeding ratio was determined using the one-dimensional cylindrical model described above for the blanket shown in FIG. As a calculation system, the total thickness of beryllium in the neutron multiplication layer was 63 cm, and the blanket thickness was 46 cm. The coolant in the neutron multiplication layer is light water, with an effective thickness of 0.5 c+a, and the cooling pipe material is stainless steel, with an effective thickness of 0.2 c+a.
It was set as 2. ×2 means that the light water layer is sandwiched from both sides. In addition, the effective thickness of the tritium breeding layer surrounding the cooling channel, which is a feature of the present invention, is 0.5 cs.
It was set to X2. The meaning of ×2 is above) - rfRJl 7
' , fI;A, The calculation results are summarized as follows.

Blanket according to an embodiment of the invention in FIG. 1: Tritium breeding ratio -1,32 FIG. 7 Conventional blanket without cooling channels in the multiplication layer: Tritium breeding ratio -1,24 FIG. 8 Multiplication layer Conventional blanket with medium cooling channels: Tritium breeding ratio -1.06 As shown by the above calculation results, the blanket of the fusion device according to one embodiment of the present invention has cooling channels in the neutron multiplier layer. However, the tritium breeding ratio is not reduced thereby, and a 25% higher breeding ratio is obtained compared to the case with cooling channels.

Another embodiment of the invention is shown in FIGS. 3 and 4. In the blanket of the fusion device shown in FIG. 3, unlike the embodiment shown in FIG. 1, the tritium breeding layer 25 surrounding the neutron multiplier layer cooling channels is integrated for all the neutron multiplier layer cooling channels. It is. In this example as well, the same effect as in the case shown in FIG. 1 can be obtained.

The first blanket which is the blanket of each embodiment of the present invention described above
In the figure and Figure 3, the calculated value of the tritium breeding ratio for the one-dimensional cylindrical model is 1.62, which is slightly lower than the guide value of 1.25 to 1.30 for the one-dimensional cylindrical model mentioned earlier. It's just more than that.

Therefore, in order to obtain a high tritium breeding ratio, a blanket is being considered in which a front breeding layer is installed just before the plasma side of the neutron multiplication layer. Examples in which the present invention is applied to such a blanket with a front growth layer will be described below.

FIG. 5 shows an example in which the present invention is applied to a blanket with a front proliferation layer. 27 is a front multiplication layer i. Surrounding the neutron multiplication layer cooling channel 21 in the neutron multiplication layer 11 is a tritium multiplication layer 25 surrounding four neutron multiplication layer cooling channels, which is a feature of the present invention. be. It was confirmed by one-dimensional cylinder calculation results that the same effect as described above can be obtained in this case as well. The conditions of the calculation system were that the thickness of the front breeding layer was 1 css, beryllium was used as the neutron multiplication layer, and the thickness was 10 css, giving the maximum tritium breeding ratio of 20 css. The neutron multiplication layer cooling channel and its surrounding tritium multiplication layer were the same as the calculation system shown in FIG. 1 described above, and were installed in the center of the neutron multiplication layer. The calculation results for the tritium breeding ratio are shown in Table 1.

Table 1 In Table 1, ■ is the proliferation ratio when the present invention is applied to a blanket with a front proliferation layer, and ■ is the conventional example of a blanket with a front proliferation layer, that is, in FIG. The breeding ratio when there is no tritium breeding layer, ■ is the breeding ratio of a reference example without a neutron multiplication layer cooling channel in a conventional blanket with a front breeding layer. From the results of ■ and ■ in Table 1, according to the example of the present invention shown in FIG. 5, the tritium breeding ratio is 20 to 25%.
It turns out that the same is true. Also, comparing the results of ■ and ■,
The tritium breeding ratios are approximately the same, indicating that by surrounding the cooling channels with tritium breeding material, the cooling channels can eliminate the negative effects of reducing the tritium breeding ratio.

Next, we will discuss the heat removal characteristics of the neutron multiplication layer by surrounding the cooling channels in the neutron multiplication layer with tritium breeder material. Li2O, an enclosed tritium breeder
The average nuclear heat generation density in beryllium neutron multipliers is 10 W/cd, and about 2 W/cd in beryllium neutron multipliers. In addition, the thermal conductivity is 0.02 W/CIIK and 2.18 W, respectively.
/csK. It is assumed that a cooling channel exists in the center of the beryllium neutron multiplier layer, and that a portion of half the thickness of the multiplier layer near the surface of the multiplier layer is cooled from the surface. Then, the neutron multiplier layer thickness in Table 1 is 10cm, 20cm
m, the temperature difference at 0.5 thickness of the tritium breeding layer surrounding the cooling channel is 180 m, respectively.
It becomes 310°. Since the lower limit allowable temperature during operation of Li2O is 400°C, the temperatures at the points where the beryllium multiplication layer and the cooling channel surrounding tritium breeding layer contact are 580°C and 710°C, respectively, which is the maximum temperature of Li2O. becomes. Further, the difference between the temperature at this point and the peak temperature in beryllium is 10° and 50°, respectively. Therefore, the peak temperature of beryllium is approximately 600°C.
, 760°C, both of which are sufficiently lower than the melting point of beryllium, 1283°C. Note that the allowable operating temperature range of Li2O is 400 to 1000°C, and there is no particular problem with the temperature determined above. From the above, there is no problem in terms of thermal characteristics, and even if the present invention is implemented, sufficient heat removal is possible.

According to this example, since the cooling channel of the neutron multiplication layer is surrounded by the tritium breeding layer, the tritium breeding ratio can be improved by 20 to 25%, so the amount of tritium consumed in the fusion reaction can be increased. More tritium can be produced.

〔Effect of the invention〕

As explained above, according to the present invention, in the blanket of a fusion device, the cooling channels present in the neutron multiplication layer are covered with the tritium multiplication layer, thereby preventing absorption of neutrons by the structural material of the cooling channel. By increasing the efficiency with which neutrons are used to produce tritium, it is possible to produce more tritium than is consumed in the fusion reaction.

[Brief explanation of drawings]

#! Fig. 1 is a conceptual diagram showing a blanket of a nuclear fusion device according to an embodiment of the present invention, Fig. 2 is a sectional view taken along line AA in Fig. 1,
FIG. 3 is a conceptual diagram showing a blanket of a nuclear fusion device according to another embodiment of the present invention, FIG. 4 is a sectional view taken along line BB in FIG. 3,
FIG. 5 is a conceptual diagram showing a blanket of a nuclear fusion device according to yet another embodiment of the present invention, FIG. 6 is a meloidal sectional view showing a tokamak type nuclear fusion device to which the present invention is applied, and FIG.
8 and 8 are conceptual diagrams showing blankets of different conventional nuclear fusion devices, respectively, and FIG. 9 is an OC@ plane view of FIG. 8. DESCRIPTION OF SYMBOLS 10... Blanket container, 11... Neutron multiplication layer, 12... Tritium breeding region, 16... Tritium breeding region cooling channel, 19... Helium gas inlet nozzle, 20... Helium gas outlet Nozzle, 21...
- Neutron multiplication layer cooling channel, 25... neutron multiplication layer cooling channel surrounding tritium multiplication layer. Sixth! ! ! 1

Claims (1)

[Claims] 1. A blanket container, a neutron multiplication layer disposed in a region close to the plasma within the blanket container, and tritium disposed on the anti-plasma side of the neutron multiplication layer within the plasma container. a tritium breeding region made of a breeding material; a neutron multiplication layer cooling channel for cooling the neutron multiplication layer; a tritium breeding region cooling channel for cooling the tritium breeding region; 1. A blanket for a nuclear fusion device, characterized in that said neutron multiplication layer cooling channel is covered with a tritium multiplication layer, said blanket comprising a carrier gas flow path for extracting tritium to the outside. 2. A nuclear fusion device according to claim 1, characterized in that a carrier gas flow path is provided for extracting tritium produced in the tritium breeding layer covering the neutron multiplication layer cooling channel to the outside. blanket. 3. In claim 2, the carrier gas flow path includes two spaces formed between the blanket container and both side surfaces of the neutron multiplier layer, and the tritium gas flow path communicating with these spaces. A blanket for a nuclear fusion device, comprising a gap in a proliferation layer.