JPH06100676B2 - Pebble for tritium production and tritium production equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention uses a solid lithium compound such as lithium oxide to produce tritium for use in a nuclear fusion reactor, a nuclear fission reactor, or a test device for these, etc. Pebble and tritium production equipment for

[Technical background] Tritium, which is a fuel for a fusion reactor, is produced by the reaction of lithium and neutrons. ⁶ Li for natural lithium
7.4% ⁷ Li is 92.6%, but to generate a tritium together react with neutrons, ⁶ Li If and nuclear producing tritium using nuclear fission reactor because it is easy to generate a tritium when neutron energy is low Neutron multiplication in the fusion reactor
It is mainly used in tritium production, such as when producing tritium using a blanket with a moderator installed on the plasma side, and is of high importance. FIG. 5 shows a schematic diagram of an apparatus for producing tritium using a conventional nuclear fission reactor. 41 in the figure
Is a tritium production device, and 42 is a nuclear fission reactor. The tritium production device 41 is provided with a lithium storage container 44 filled with a breeding material in the form of fine pebble lithium compounds such as lithium oxide (Li ₂ O). The container 44 is inserted into the position of the core 43, and neutrons are irradiated to generate tritium. The generated tritium is diffused in the purge gas such as helium sent through the sweep gas supply pipe 45, and is recovered by the tritium recovery device 47 through the sweep gas discharge pipe 46. As shown in FIG. 6, the container 44 has a cooling water pipe.
53 penetrates and removes the heat generated during the tritium production reaction. In FIG. 6, 52 is a pebble of a lithium compound,
54 is a spacer tube.

7 and 8 are explanatory views of an apparatus for producing tritium using a conventionally proposed nuclear fusion reactor, FIG. 7 is a schematic sectional view of the nuclear fusion reactor, and FIG. 8 is tritium breeding. It is a fragmentary sectional view of a blanket. In the fusion reactor 61, a tritium breeding blanket placed around the plasma 62.
Tritium is produced by 63. The tritium breeding blanket 63 has a neutron multiplier / moderator 65 inside the outer wall 64, and a pebble made of a fine-grained lithium compound inside.
It has a composite structure containing a lithium storage container 69 filled with 68. Neutrons incident from the plasma 62 side are decelerated by the neutron multiplication / moderation material 65 and react with ⁶ Li in the pebbles 68 to generate tritium. The produced tritium is recovered by the helium purge gas flowing around the pebble 68. A cooling pipe 67 penetrates the lithium container 69 and absorbs heat generated during the tritium generation reaction to cool the lithium container.

[Problems of the prior art] When trying to generate tritium by the reaction between ⁶ Li and thermal neutrons as described above, there is a problem that the reaction mainly occurs in the vicinity of the surface on which the neutron is incident. . As shown in FIG. 6, when the container 44 is filled with the pebble 52 and irradiated with thermal neutrons from the surroundings, a very high tritium production rate and a high heat generation rate are exhibited in the vicinity of the surface on which thermal neutrons are incident. At the same time, a rapid decay occurs, and the tritium production rate and heat generation rate are extremely low near the center of the figure. For example, when a small spherical pebble of lithium oxide (Li ₂ O) using natural lithium is filled in a container at a filling rate of 60% and irradiated with thermal neutrons, thermal neutrons are one digit at a depth of 10 mm from the incident surface. It will be attenuated more. Such a phenomenon similarly occurs in the tritium breeding blanket shown in FIG. 8, and there is a problem that the tritium production reaction and heat generation are concentrated in the vicinity of the surface of the neutron incident direction shown by the arrow.

In the tritium production reaction, the pebbles made of a lithium compound undergo a chemical reaction when the temperature becomes too high and the quality is altered.If the temperature is too low, the generated tritium does not diffuse into the purge gas and it becomes difficult to recover it.
It is necessary to keep in the range of ℃ ~ 1000 ℃, but if the reaction is biased near the incident surface of neutrons as described above, it becomes difficult to remove heat near the incident surface and the entire pebble is kept at a constant temperature. It becomes difficult to control.

In addition, there are many problems such that the reaction of only ⁶ Li near the incident surface progresses, the characteristics of the pebble in the portion change, and the interior with a low reaction rate is practically wasted.

For such problems, ⁶ L near the neutron incident surface
lowering the atomic number density of i, an attempt to achieve flattening of tritium production rate and heat generation rate in the lithium filling container by raising the atomic number density of ⁶ Li inside, in the vicinity of neutrons incident surface ⁶ Li It has been proposed to place a depleted solid lithium compound and a lithium compound enriched with ⁶ Li inside. However, in this method the concentration step of the impairment process and ⁶ Li of ⁶ Li is essential, there is also a drawback in terms of time-consuming after expenses can not be used lithium present naturally.

The present invention has been made in view of the above circumstances, and provides a tritium production pebble and a tritium production apparatus that flatten the tritium production rate and the heat generation rate in a lithium-filled container with a simple configuration. Has an aim.

[Means for Solving Problems] The above object is achieved by a tritium production pebble and a tritium production apparatus described in the claims. That is, (1) a tritium production pebble for producing tritium for use in a fusion reactor, which is a small molded body of a solid lithium compound, wherein a hollow portion is formed inside the small molded body, and Pebbles that change the content of the lithium compound in the small compact by changing the ratio, and a mixture of silicon oxide and the like and a lithium compound are mixed to form a small sphere, and a mixture of silicon oxide and the like. A pebble for producing tritium, which comprises a small sphere in which the content of the lithium compound is changed by changing the mixing ratio with the lithium compound.

(2) A device for producing tritium for use in a fusion reactor, which is a small molded body of a solid lithium compound, wherein a hollow portion is formed inside the small molded body, and the ratio of the hollow portion is changed. By mixing a pebble that changes the content rate of the lithium compound in the small compact with a mixture of a silicon oxide and a lithium compound to form a small sphere, and mixing a mixture of the silicon oxide and a lithium compound. Using the tritium production pebbles consisting of small spherical pebbles that change the content of the lithium compound by changing the ratio, in the pebble layer closest to the neutron incident surface side among the pebble layers provided inside the tritium production device. An apparatus for producing tritium, characterized by being filled with a pebble for producing tritium having the smallest content rate of a lithium compound.

(3) For the production of tritium having the highest lithium compound content in each pebble layer, the pebble layer having the highest lithium compound content is filled in each pebble layer as the distance from the neutron incidence surface increases. The tritium production apparatus according to (2), wherein the pebble is filled.

[Examples] FIG. 1 is a diagram showing an example of a pebble for producing tritium of the invention described in claim 1, (a) is a hollow in the center of a cylindrical molded body 1 made of a lithium compound. Part 2 is provided, (b) is the same size as (a), but an example of a molded body in which the diameter of the hollow part is reduced to increase the amount of the lithium compound, (c) shows the shape of the hollow part. Another example is different.
FIG. 3D shows a mixture of a lithium compound and silicon oxide (SiO ₂ ), which is molded into a small spherical shape. The content ratio of the lithium compound can be adjusted by changing the mixing ratio of the two. is there. An example of the above-mentioned lithium compound is Li
Ceramic-like sintered bodies such as ₂ O, LiAlO ₂ and Li ₂ SiO ₃ can be mentioned. As the substance to be mixed with the lithium compound as shown in FIG. 1 (d), other than SiO ₂ Al ₂ O ₃ (alumina) And metal aluminum (Al).

FIG. 2 is a partially cutaway perspective view showing an embodiment of the tritium producing apparatus according to the invention as set forth in claim 2. Reference numeral 3 is a tritium production device for a nuclear fission reactor, and as described with reference to FIG. 1, a pebble layer 5 using a pebble with a reduced amount of a lithium compound is provided in the lithium storage container 4. Reference numeral 8 is a sweep gas supply pipe, 9 is a sweep gas discharge pipe, and 10 is a cooling water pipe. When the tritium production apparatus 3 configured as described above is inserted into the core of a nuclear fission reactor and helium gas is delivered from the sweep gas supply pipe 8, the helium gas permeates into the pebble layer from the lower portion of the lithium storage container 4. Neutrons from the nuclear fission reactor enter from the outer peripheral direction of the lithium storage container 4.

In FIG. 2, the pebble layer 5 is shown to be composed of one type of pebble in which the amount of the lithium compound is reduced, but the content of the lithium compound on the neutron incident surface side is higher than that of the conventional tritium producing device. By using a tritium-producing pebble with a low helium content and a small number of ⁶ Li atoms, the tritium production reaction can be extended to the inside without being biased toward the neutron incident surface side. The generated tritium diffuses in the helium gas and is collected through the sweep gas discharge pipe 9.

FIG. 3 is a partially cutaway perspective view showing an embodiment of the tritium producing apparatus according to claim 3. In the figure, 3 is a tritium production device for a nuclear fission reactor, 4 is a lithium containment vessel, 5, 6 and 7 are pebble layers composed of a lithium compound, 5 is a pebble layer containing the smallest amount of lithium compound, and 6 is lithium. A pebble layer having a compound content higher than that of the pebble layer 5 and a pebble layer 7 having the highest lithium compound content (including a case of only a lithium compound). For example, when the lithium compound content is ⁶ Li: 1: 7: 3
The pebble is laminated so that the ratio becomes 0. As for the content rate of the lithium compound, as described in the first invention, the size of the hollow portion of the pebble is changed or the mixing ratio of the mixed substance such as silicon oxide is changed. It can be easily adjusted by combining a pebble of a lithium compound that does not contain other substances.

When the tritium production apparatus configured as described above is inserted into the core of a fusion reactor and helium gas is sent out from the sweep gas supply pipe 8, the helium gas permeates into the pebble layers 5, 6, 7 from the lower part of the lithium storage container. Neutrons from the nuclear fission reactor enter the lithium containment vessel from the outer peripheral direction, but the outermost pebble layer 5 has a low lithium compound content of ⁶ L.
The number of atoms of i is small, and the content of the lithium compound increases in order to reach the inner layers 6 and 7, and the number of atoms of ⁶ Li increases. Therefore, the tritium formation reaction does not concentrate only in the outermost layer, and a flattened reaction occurs also in the pebble layers inside 6,7. The generated tritium diffuses in the helium gas, and the sweep gas exhaust pipe 9
Through a tritium recovery device (not shown). Since the heat generated in each pebble layer is averaged in each layer and is not concentrated in the outermost layer, heat is effectively removed by the cooling water pipe 10, and partial alteration of the pebble is also prevented.

FIG. 4 is a partially cutaway perspective view showing another example of the blanket for producing tritium used in the nuclear fusion reactor, which is another embodiment of the invention described in claim 3. FIG. 31 is a tritium breeding blanket, 32 is an outer wall, 33 is a neutron multiplier / moderator (Be), 34 is a cooling water pipe, 35 is a pebble layer with the smallest lithium compound content, and 36 is a lithium compound content. The pebble layer more than the pebble layer 35, 37 is the pebble layer having the highest content of the lithium compound (including the case of only the lithium compound). The white arrow indicates the incident direction of neutrons, the layer having a small lithium compound content is arranged on the surface side in the incident direction, and the layer having a large lithium compound content is arranged on the deep side.

Therefore, similar to the above, the tritium generation reaction is flattened over the entire pebble layers 35, 36, 37 without being concentrated only in the pebble layer of the surface layer, and the reaction does not occur efficiently in the entire pebble layer and no waste occurs in the deep portion. . Since the heat generation is not concentrated on the neutron incident surface side, heat is efficiently removed by the cooling water pipe 34, and it is not necessary to arrange a large number of cooling water pipes on the incident surface side, and the structure is simple.

In the above examples, the example in which the pebble layer is one layer or three layers is shown, but the reaction may be performed by forming two layers or more layers, or by mixing pebbles having different lithium compound contents as required. It is also possible to achieve a flatter rate.

According to [Effects of the Invention] patented invention in the range first claim of claim, concentration of ⁶ Li, was adjusted atom number of ⁶ Li with a conventional lithium compound without requiring any special process such as impairment It is possible to supply a pebble for producing tritium, and according to the inventions of claims 2 and 3, it is possible to effectively prevent concentration of the tritium producing reaction in the vicinity of the neutron incident surface, and to fill the filled lithium compound. Has a number of advantages such as enabling efficient use in deep areas, preventing partial alteration of the lithium compound, providing a flat heat distribution and facilitating heat removal.

[Brief description of drawings]

FIG. 1 (a) to (d) are enlarged perspective views of a tritium-producing pebble according to an embodiment of the invention described in claim 1.
FIG. 2 is a partially cutaway perspective view of a tritium production apparatus for a nuclear fission reactor in an embodiment of the invention described in claim 2;
The figure is an embodiment of the invention described in claim 3, and is a partially cutaway perspective view of a tritium production device for a nuclear fission reactor. FIG. 4 is an embodiment of the invention described in claim 3. FIG. 5 is a partially cutaway perspective view of a tritium breeding blanket for a nuclear reactor, FIG. 5 is a schematic sectional view of a conventional tritium production apparatus for a nuclear fission reactor, and FIG. 6 is a partially cutaway perspective view of the tritium production apparatus of FIG. Is a schematic cross-sectional view showing a conventional tritium production apparatus using a nuclear fusion reactor, and FIG. 8 is a partially cutaway perspective view of the tritium breeding blanket of FIG. 7. 1 ... Tritium production pebble, 2 ... Hollow part, 3 ...
Tritium production equipment, 4 ... Lithium storage container, 5,6,7
...... Pebble layer, 31 …… Tritium breeding blanket, 3
5,36,37 …… Pebble layer.

Claims (3)

[Claims] 1. A tritium-producing pebble for producing tritium for use in a fusion reactor, which is a small molded body of a solid lithium compound, wherein a hollow portion is formed inside the small molded body, and Pebbles that change the content of the lithium compound in the small compact by changing the ratio, and a mixture of silicon oxide and the like and a lithium compound are mixed to form a small sphere, and a mixture of silicon oxide and the like. A pebble for producing tritium, characterized in that the pebble is composed of small spheres in which the content of the lithium compound is changed by changing the mixing ratio with the lithium compound. 2. An apparatus for producing tritium for use in a fusion reactor, which is a small molded body of a solid lithium compound, wherein a hollow portion is formed inside the small molded body, and the ratio of the hollow portion is changed. Pebbles that change the content of the lithium compound in the small compact by mixing the mixture with a lithium compound and a lithium compound and molded into a small spherical shape, and a mixture of the silicon oxide and the lithium compound. Among the pebble layers provided inside the tritium production device, the pebble layer closest to the neutron incident surface side was used, which was a small spherical pebble for changing the lithium compound content by changing the mixing ratio of A tritium production apparatus characterized in that a pebble for producing tritium having the smallest content of a lithium compound is filled therein. 3. A pebble for producing tritium having a large lithium compound content is sequentially filled in each pebble layer as it moves away from the neutron incidence surface side, and a tritium having a highest lithium compound content content in the pebble layer farthest from the neutron incidence surface. The tritium production apparatus according to claim (2), wherein the production pebble is filled.