JP2001066400A - Nuclear spallation container impact force preventing mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent repeated application of a large impact force to a nuclear spallation container in a target for bringing about a nuclear spallation by irradiating a liquid metal with an accelerated proton. SOLUTION: In the nuclear spallation container sealed with a liquid metal and used to bring about a nuclear spallation by irradiating the metal with a large strength proton, a protruding part is formed at its container wall, and a free surface of the metal is generated to absorb an impact force generated in the container by means of vertical movements of the surface, thereby preventing the force received by the container wall. Accordingly, a particular power device is not required.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simple mechanism for preventing a large impact force from being repeatedly applied to a spallation vessel. That is, the present invention relates to a mechanism for preventing a large impact force from being repeatedly applied to a spallation vessel in a target that causes spallation by injecting accelerated protons into liquid metal.

[0002] A proton beam accelerated to a GeV class high energy by an accelerator is converted into a heavy element substance (target).
Can generate a large amount of neutrons. In nuclear physics, the nuclei of the target are separated by incident particles having a large energy, and this phenomenon is called spallation. Accordingly, heavy atoms, strictly speaking, nuclei having a high atomic number density (for example, Ta,
(W, Hg, Pb, Bi, U, etc.) can generate more neutrons by spallation for one incident proton (as a guide, about 20 to 30 neutrons are possible).
In addition, neutrons generate secondary particles such as protons and pions other than neutrons (incident particles are called primary particles).
Occurs.

[0003] Among these, neutrons are used, and are used in the following applications. Structural biology (molecule structure analysis of biological protein molecules), material science (we can see deep into a substance by neutrons as waves), annihilation technology (stable nuclei with a long half-life and stable half-life It is used in waste treatment (1), irradiation of materials, production of radioisotopes (cancer therapy, life science), and basic research on physical properties.

[0004]

2. Description of the Related Art In a target that accelerates high-intensity protons and impinges on liquid metals such as mercury, lead, and bismuth to cause spallation of these metals, thermal energy is introduced into the target by the incident protons. Instantly accumulated. As a result, a shock wave is generated in the target, which propagates through the liquid metal and applies a shocking force to the surrounding spallation vessel enclosing the liquid metal. This shock wave is reflected by the spallation vessel wall, propagates further through the liquid metal, and repeatedly applies force to the vessel.

Various shapes can be considered for a conventional target spalling container, but a basic shape such as a hemispherical head with a tea caddy as shown in FIG. 4 is fundamental. FIG. 2 shows a change in the force applied to a container when a liquid metal is sealed in such a conventional container and high-intensity protons are incident thereon to cause spallation. There, it is shown that a shock wave generated at the center of the container propagates, and after 500 μs after the first wave reaches the container, a larger wave rushes in 500 μs later and the force is again applied to the container.

[0006]

In designing a spallation vessel, it is not desirable to apply repetitive forces to the vessel in this way. When force is repeatedly applied to the container, the service life of the container is shortened, the container needs to be replaced frequently, and the operation efficiency of the spallation facility is reduced economically. Therefore, a mechanism is required to actively and preferably absorb energy and absorb energy due to shock waves applied to the target spallation vessel.

[0007]

According to the present invention, there is provided a mechanism for providing a space in a part of a target spallation container where liquid metal can form a free surface without direct contact with the container. In this way, it is possible to easily reduce the large force that repeatedly acts on the container without requiring any special power or device.

That is, in the target of the present invention, as shown in FIG. 1, a liquid metal such as mercury, lead, bismuth, or the like is sealed in a spallation vessel having a hemispherical head with a tea caddy. In order to prevent the impact force that the container repeatedly receives when high intensity protons are incident on this and cause nuclear spallation, a projection is formed on the container wall on the liquid level of the sealed liquid metal,
By forming a free surface of the liquid metal there, the impact force generated in the container is absorbed by the vertical movement of the free surface to prevent the impact force on the container wall.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the spallation vessel of the present invention,
As shown in FIG. 1, a hemispherical head on which high-intensity protons are incident is provided in a cylindrical container body, and liquid metal is filled and filled in the container body. Then, a projecting portion is formed on the container wall corresponding to the upper surface of the liquid metal sealed in the container, and a space is formed therein to form a free surface where the liquid metal does not directly contact the container.

In the case where high intensity protons are incident on the hemispherical head of the container of the present invention having the above-described structure to cause the liquid metal to spall, as shown in FIG. Thermal energy accumulates in the center along its length,
Then, a shock wave is sequentially generated toward the container wall. Then, the shock wave sequentially propagates in the container along the length direction of the container, and repeatedly applies a destructive force to the inner wall of the container.

Therefore, in the present invention, a projecting portion is formed on at least a part of the container wall corresponding to the upper surface of the liquid metal sealed in the spallation container, and a free surface of the liquid metal is generated there. Thus, the shock wave generated in the container can be absorbed by the vertical movement of the free surface, and the impact force applied to the container wall can be prevented. Hereinafter, the present invention will be described based on examples.

[0012]

FIG. 3 shows the magnitude of impact force per unit area applied to a container when a high-intensity proton is accelerated and incident on liquid metal using the spallation container of the present invention. That is, FIG. 3 shows a change in the force applied to the container when a free surface is formed on the liquid metal in a part of the container as shown in FIG.

Further, using a conventional spallation vessel without a free surface of liquid metal as shown in FIG.
FIG. 2 shows the magnitude of impact force per unit area applied to the container when a high-intensity proton is accelerated and incident on liquid metal.

A comparison between FIG. 2 (conventional example) and FIG. 3 (invention) shows that FIG. 3 shows that the repetition of the large force shown in FIG. 2 disappears. Such a spallation technique is not yet known in the world, and thus there is no example of adding a container to this mechanism.

[0015]

According to the present invention, a space is provided in a part of a target container containing a liquid metal such as mercury, lead and bismuth so that the liquid metal can form a free surface without directly contacting the container. This has a remarkable effect peculiar to the present invention in that a large force acting repeatedly on the container can be easily reduced without requiring any special power or device.

[Brief description of the drawings]

FIG. 1 is a view showing a structure of a nuclear spallation container of the present invention.

FIG. 2 is a diagram showing an impact force applied to a spallation vessel having a structure of the present invention.

FIG. 3 is a view showing an impact force applied to a spallation vessel having a conventional structure.

FIG. 4 is a view showing the structure of a conventional spallation vessel.

Claims (1)

[Claims] 1. A spalling vessel for enclosing a liquid metal and injecting high-intensity protons into the spalling vessel to cause spalling, wherein a projection is formed on the vessel wall, and a liquid metal The container wherein the free surface is generated to absorb the impact force generated in the container by the vertical movement of the free surface, thereby preventing the impact force received by the container wall.