JPH06228602A - Metallic beryllium pebble - Google Patents

Abstract

PURPOSE:To provide a metallic beryllium pebble enhanced in tritium breeding ratio, which is hardly bridged when filled in a closed vessel and with the generation of a cavity liable to form a hot spot reduced in the closed vessel to prevent the local overheating. CONSTITUTION:This metallic beryllium pebble 16 has 0.1-5mm average grain diameter, 0.001-0.05mm sphericity and 0.1-0.4mum surface roughness Ra, Since the pebble has the relatively small average grain diameter, relatively high sphericity and relatively low surface roughness, the pebbles are easily filled in a closed vessel, the pebbles are not bridged, and the filling factor in the closed vessel is increased. Consequently, as a large cavity is not locally formed in the closed vessel packed with the pebbles, the generation of a hot spot is reduced, and local overheating is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to pebble metal beryllium (hereinafter referred to as "metal beryllium pebbles"), and particularly to characteristics such as size, sphericity, surface roughness and the like. .

[0002]

2. Description of the Related Art Conventionally, metal beryllium pebbles have been manufactured by a magnesium reduction method. Metal beryllium pebbles produced by this magnesium reduction method,
The sphericity is, for example, 0.1 to 0.5 mm, and has crater-like irregularities on the surface. The surface of this metal beryllium pebble is rough.

[0003]

According to the metal beryllium pebbles produced by the conventional magnesium reduction method as described above, since the metal beryllium pebbles have crater-like irregularities on the surface, such metal beryllium pebbles are contained in the closed container. When filling the pebble, a trapped state occurs between the metal beryllium pebbles, and a hanging phenomenon occurs in the closed container 5 as shown in FIG. That is, it refers to a phenomenon in which the metal beryllium pebbles 6 are caught by each other and a large void 8 is generated inside. The porosity in the closed container in this case is, for example, 30 to 50% by volume. As a result, it becomes difficult to fill the metal beryllium pebbles 6 in the closed container 5 with high density. Therefore, in a fusion reactor blanket that uses such a sealed container filled with metal beryllium pebbles, there is a problem that the tritium breeding rate is reduced and the efficiency of the fusion reactor fuel cycle is reduced.

Further, regarding the form of the metal beryllium pebbles 6, as shown in the schematic view of FIG. 2A, since the surface 6a of the metal beryllium pebbles 6 is rough, stress concentration occurs at the contact portion between the pebbles, There is a problem that cracks are likely to occur starting from the contact portion between the pebbles 6 and the generation of fine particles of metal beryllium or the reaction (oxidation) between the fine particles and the surrounding atmosphere is easily promoted.

The present invention has been made in order to solve such a problem, and a metal beryllium pebbles to be filled in a hermetically sealed container is less likely to be suspended, and a void is apt to become a hot spot in the hermetically sealed container. An object of the present invention is to provide a metal beryllium pebble whose amount is reduced to prevent local overheating and to increase the tritium breeding rate.

[0006]

The metal beryllium pebbles of the present invention are characterized by having an average particle size of 0.1 to 5 mm and a sphericity of 0.001 to 0.05 mm.
Further, this metal beryllium pebble has a surface roughness Ra of Ra =
It is preferably 0.1 to 0.4 μm.

[0007]

According to the metal beryllium pebbles of the present invention, the metal beryllium pebbles have a relatively small average particle diameter, their sphericity is relatively high, and their surface roughness is relatively smooth. Therefore, the filling work into the closed container becomes easy, the occurrence rate of the hanging phenomenon decreases, and the fill ratio into the closed container increases. For this reason, the occurrence of locally large voids in the closed container filled with metal beryllium pebbles is suppressed, so that the occurrence of hot spots is reduced and local overheating is prevented.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. An apparatus for carrying out the production of metal beryllium pebble is as shown in FIG. The metal beryllium pebbles are manufactured, for example, by a device 27 according to the rotating electrode method shown in FIG. In this method, an electrode composed of an arc melting electrode or a plasma melting electrode and a consumable electrode composed of metal beryllium are provided in a closed container in an inert gas, and arc or plasma is generated between both electrodes to melt the consumable electrode. Meanwhile, metallic beryllium droplets are scattered by centrifugal force and cooled and solidified to obtain spherical particles (pebbles) of metallic beryllium. In FIG. 4, 21 is a closed vessel, 22 is a consumable electrode made of metal beryllium, and 23 is a water-cooled tungsten arc melting electrode or plasma melting electrode. The gas in the closed container 21 is exhausted to the outside through the exhaust hole 4, and the inert gas is introduced into the closed container 21 through the introduction hole 25. The consumable electrode 22 is rotationally driven by the rotating device 26. An arc or plasma is generated between the consumable electrode 22 and the melting electrode 23 to melt the consumable electrode 22 made of metal beryllium. When the dissolved metal beryllium has a certain size, it is scattered in the centrifugal direction by centrifugal force, and is cooled and solidified while passing through an inert gas to form spherical metal beryllium particles. As the inert gas in the closed container 21, for example, argon gas, helium gas, or a mixed gas thereof is used.

The metal beryllium pebbles obtained by the above apparatus 27 have a relatively small particle size, a high sphericity, and a smooth surface roughness. For the average particle size,
It is 0.1 to 5 mm. For sphericity, 0.001
~ 0.05 mm. The metal beryllium pebble obtained by the rotating electrode method has an excellent sphericity,
A large amount of sphericity values within the range of 0.001 to 0.05 are obtained. Therefore, the filling rate in the closed container is increased.

Regarding the surface roughness, Ra = 0.1 to 0.
4 μm and Rmax = 0.9 to 1.4 μm. Therefore, when metal beryllium is filled in the closed container, stress concentration on the metal beryllium pebble surface is avoided, and reaction (oxidation) with the gas flowing in the container at the time of filling is suppressed. In addition, it was possible to significantly reduce the occurrence rate of the hanging phenomenon during filling.

The relationship between the occurrence rate of the hanging phenomenon and the sphericity is shown in FIG. From this figure, the sphericity is 0.05
It can be seen that the rate of occurrence of the hanging phenomenon increases significantly when the value exceeds. A schematic view of the metal beryllium pebble filling state of this example is shown in FIG. FIG. 3 (A) shows a metal beryllium pebble filled state according to a comparative example in which a hanging state occurs in various places in a conventional closed container. According to the embodiment of the present invention, as shown in FIG. 3B, since the metal beryllium pebbles 16 are less likely to be suspended in the closed container 5, the closed container is filled with the metal beryllium pebbles 16 uniformly. It is understood that no large void is generated. The porosity according to this embodiment is 20 to 40% by volume.
On the other hand, the porosity in the closed container for the comparative example shown in FIG. 3 (A) is 30 to 50% by volume.

Therefore, according to the metal beryllium pebbles according to the embodiment of the present invention, when the metal beryllium pebbles are supplied into the closed container, a hanging phenomenon is unlikely to occur in the closed container. There is an effect that. Therefore, the tritium breeding rate during the operation of the fusion reactor is improved, the efficiency of the fuel cycle of the fusion reactor is increased, and the accident due to local overheating is avoided.

Next, FIG. 5 shows a structural example of a fusion blanket filled with metal beryllium pebbles. In FIG. 5, a schematic cross-sectional view of a blanket container provided around the fusion reactor plasma is shown. In FIG. 5, A is a lithium oxide (Li ₂ O) pebble, B is a metal beryllium pebble,
C indicates stainless steel. Further, a portion indicated by reference numeral 1 is a blanket container, a portion indicated by reference numeral 2 is a neutron multiplication region, and a portion indicated by reference numeral 3 is a first wall.

[0014]

As described above, according to the metal beryllium pebbles of the present invention, the average particle size is small, the sphericity is high, and the surface roughness is smooth. Since the hanging phenomenon is unlikely to occur, there is an effect that local overheating is prevented in the void portion and safety is enhanced. In addition, since the surface roughness of the metal beryllium pebbles is smooth, stress concentration at the contact area between the metal beryllium pebbles is avoided, and cracks are less likely to occur, so clogging with fine particles of the metal beryllium pebbles is less likely to occur, and Since the oxidation of beryllium is suppressed, the life of the metal beryllium pebble is extended.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing a relationship between a sphericity and a hanging phenomenon occurrence rate according to an experimental example of the present invention.

FIG. 2A is a schematic view showing a shape of a metal beryllium pebble according to a conventional example. (B) is a schematic diagram showing a metal beryllium pebble according to an embodiment of the present invention.

FIG. 3A is a schematic view showing a state in which a metal beryllium pebble of a conventional example is filled in a closed container. (B)
FIG. 3 is a schematic diagram showing a state in which a metal beryllium pebble according to an embodiment of the present invention is filled in a closed container.

FIG. 4 is a schematic configuration diagram showing an apparatus for producing metal beryllium pebbles.

FIG. 5 is a schematic cross-sectional view showing a cross section of a fusion reactor blanket.

[Explanation of symbols]

 1 Blanket Container 16 Metal Beryllium Pebble

Claims (2)

[Claims] 1. A metal beryllium pebble having an average particle diameter of 0.1 to 5 mm and a sphericity of 0.001 to 0.05 mm. 2. The metal beryllium pebbles according to claim 1, having a surface roughness Ra = 0.1 to 0.4 μm.