JPH0372917A - Metal vapor generator - Google Patents

Abstract

PURPOSE:To enhance the evaporation efficiency of a metal raw material by arranging a plurality of convection preventing plates to the receiving recessed part of a evaporation crucible in parallel at a required interval, and forming each of the convection preventing plates from a heating body for heating the metal raw material in order to separate an isotope in the receiving recessed part. CONSTITUTION:A plurality of convection preventing plates 16 are arranged in the receiving recessed part 14 of an evaporation crucible 13 in parallel at a required interval and formed from heating bodies for heating the metal raw material 15 for separating an isotope in the receiving recessed part 14 and the metal raw material is heated, melted and evaporated by the beating bodies. As a result, the generation of a convection in the evaporation crucible is effectively suppressed and the evaporation efficiency of the metal raw material is enhanced.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a metal vapor generator applied to an isotope separation device, and particularly relates to a metal vapor generator that efficiently evaporates metal raw materials. .

(Prior technology) Isotope separation equipment for metal atoms using a laser beam is
Compared to conventional isotope separation devices using gas diffusion methods or centrifugation methods, the isotope separation efficiency is extremely high and superior.

For this reason, isotope separation equipment that uses the atomic laser method is
There is no need to repeat the same separation process in multiple stages in a cascade system until a specific isotope reaches a predetermined concentration level, and the entire separation device is compact and economical.

A conventional isotope separation apparatus for metal atoms using a laser method is constructed as conceptually shown in FIG. A thermochemically resistant evaporation crucible 3 is installed. In the evaporation crucible 3, a metal raw material 4 to be isotopically separated is accommodated in an upwardly opened storage recess.

An electron beam a emitted from an electron gun 5 is deflected by a deflecting magnetic field 6 and is irradiated into the evaporation crucible 3. By irradiating the electron beam a, the metal raw material 4 is heated to a high temperature of, for example, 3,000 ℃, and is melted. The metal is then evaporated, producing a metal vapor stream.

This metal vapor stream rises inside the vapor enclosure container 2, and the selective excitation laser beam C is irradiated onto this rising metal vapor stream. By this laser light irradiation, specific isotope metal atoms (metal vapor) d, which are characterized by recovery, are selectively excited and ionized (ionized). When the ionized isotope d passes between the positive electrodes 7a and the negative electrodes 7b, which are arranged alternately, only the ionized isotope d is attracted to the surface of the negative electrode, which is a collection plate for voltage application. It is adsorbed and recovered.

On the other hand, isotope metal atoms (metal vapor) that are not ionized pass through between the electrodes without being affected by the electric field between the electrodes as neutral atoms, and are recovered by a neutral atom collection device placed on the secondary side of the electrodes. It is sucked into the plate 8 and collected.

(Problems to be Solved by the Invention) In a metal vapor generator included in a conventional isotope separation apparatus, an electron beam a emitted from an electron gun 5 is irradiated onto a metal raw material 4, and the metal raw material 4 is heated to a temperature of, for example, 3000K.
Heat to high temperature and melt. At this time, the metal raw material 4 is heated and melted to generate vapor flow from the surface of the evaporation crucible 3, and convection of the molten liquid metal occurs inside the crucible as shown by the symbol e in FIG. 6.

The convection of the liquid metal 4 occurring in the evaporation crucible 3 basically forms a loop on each side with the center line of the cross section of the crucible as the border, and if we focus on the right side of FIG. The convection e of the molten gold chips is heated at the center and rises, flows toward the side wall of the evaporation crucible 3 at the surface, is cooled at the crucible side wall, descends, and passes through the bottom of the evaporation crucible 3. You will be guided back to the center.

In order to increase the flow of metal vapor evaporated from the evaporation crucible 3, it is necessary to heat the metal raw material 4 to a high temperature.

On the other hand, since the crucible material in the evaporation crucible 3 needs to be cooled, even if the metal raw material 4 is heated to a high temperature, it must be cooled on the side wall surface of the crucible, especially on the side wall surface of the cross section of the crucible, and this cooling is energy efficient. In addition, there was a fear that the evaporation efficiency of the metal raw material would be deteriorated.

There is a large difference in the evaporation efficiency of the metal raw material, for example, about 10 times, between when convection is generated in the evaporation crucible and when it is not, and the generation of convection has been a cause of deteriorating the evaporation efficiency of the metal raw material.

The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a metal vapor generating device that effectively suppresses the generation of convection within an evaporation crucible and improves the evaporation efficiency of metal raw materials. With the goal.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the problems of the prior art described above, the metal vapor generator according to the present invention provides a metal vapor generator in which a metal raw material for isotope separation is accommodated in a storage recess of an evaporation crucible. In the steam generator, a plurality of convection prevention plates are arranged in parallel at required intervals in the storage recess of the evaporation crucible, the convection prevention plates are formed as heating elements that heat the metal raw materials, and the heating elements heat the metal raw materials. It is heated, melted, and evaporated.

Further, in order to solve the above-mentioned problems, the metal vapor generator according to the present invention has a convection prevention plate that partitions the storage recess of the evaporation crucible into a multilayer structure, and a notch is formed at the top of the convection prevention plate. , the notch formation positions are formed so that adjacent convection prevention plates are not aligned with each other,
Furthermore, the convection prevention plate is formed of a porous material such as porous tungsten material.

(Function) This metal vapor generator has a plurality of convection prevention plates placed side by side in the storage recess of the evaporation crucible to partition the interior into a multilayer structure, and the convection prevention plates are configured as a heating element to heat the metal raw material. Therefore, the metal raw material stored in the storage recess of the evaporation crucible is effectively heated and melted by the heating element, and convection is prevented by the convection prevention plate, so that the metal raw material is efficiently evaporated from the evaporation crucible. Evaporation efficiency can be improved.

(Example) An example of a metal vapor generator according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an example in which the present invention is applied to an isotope separation apparatus 10. This isotope separation apparatus 10 houses a steam enclosure 12 within a vacuum vessel 11, and an evaporation crucible 13 is installed below this vapor enclosure 12. Evaporation crucible 13
has a storage recess 14 that opens upward, and this storage recess 1
A metal raw material 15, which is an isotope metal, is housed in the chamber 4.

In the storage recess 14 of the evaporation crucible 13, as shown in FIGS. 2 and 3, a plurality of convection prevention plates 16 are arranged side by side with required intervals, for example, about 5 nm, so as to face the longitudinal direction. The inside of the four storage parts 14 is partitioned into a multilayer structure by the convection prevention plate 16.

The convection prevention plate 16 is usually made of a rectangular plate with excellent heat resistance such as tungsten or porous tungsten, and is held in the storage recess 14 of the evaporation crucible 13 by fixed holding means such as screws or coils. The distance between each convection prevention plate 16 is maintained by a distance maintaining spacer (not shown) or the like.

Further, the convection prevention plate 16 is connected to a power source (not shown) via lead wires 17 drawn out from both ends, and is configured as a heating element by being energized. Due to the heat generated by the convection prevention plate 16, the metal raw material 15, which is an isotope metal, is heated and melted.
evaporated.

A metal vapor flow A generated by heating, melting, and evaporating the metal raw material 15 is guided into the vapor enclosure container 12 and rises.

A selective excitation laser beam 20 is irradiated onto the rising metal vapor flow from a laser device (not shown). This laser beam 20 has a frequency corresponding to the resonance absorption line of the specific isotope in order to selectively excite the metal atoms (metal vapor) of the specific isotope to be separated. Selective excitation excitation laser beam 2
The specific isotope irradiated with zero is ionized and becomes an ionized isotope 21 having a positive charge. When this ionized isotope 21 passes through the electric field space between the positive electrodes 22 and negative electrodes 23 arranged alternately, it is attracted to the negative electrode side, adsorbed, and collected on the surface of the negative electrode.

On the other hand, isotopic metal atoms that are not ionized (metal vapor)
Since they are not affected by the electric field, they pass between the electrodes and are collected and collected by the collection plate 25 for collecting neutral atoms disposed on the secondary side of the electrodes.

By the way, the top of the convection prevention plate 16 disposed in the storage recess 14 of the evaporation crucible (3) is spaced appropriately, as shown in FIG.
Cutouts 26,27 are formed as shown in A) and (B). The positions of the notches 26 and 27 are formed so that adjacent convection prevention plates i6 and 16 are not aligned with each other. These notches 26 and 27 are the liquefied metal raw material (
5 functions as a supply route.

Next, the operation of the metal vapor generator will be explained.

Electricity is applied to the convection prevention plate 16 arranged in parallel to the storage recess 14 of the evaporation crucible 13, and the convection prevention plate 16 is caused to generate heat by Joule heat. The metal raw material 15 is heated and melted by the Joule heat of the convection prevention plate 16. In this way, the metal raw material 15 is heated and melted within the storage recess 14 and evaporated.

At this time, a case is considered in which a porous tungsten material is used for the convection prevention plate 16 and uranium is used as the metal raw material.

The melting point of tungsten is 3683K.

Since the melting point of uranium is 1405, the convection prevention plate 16
When the metal raw material 15 is heated to, for example, 3000K by applying current, the convection prevention plate 16 is maintained in a solid state, the metal raw material 15 is melted and kept in a liquid state, and a temperature corresponding to 3000K is released from the liquid surface of the metal raw material 15. The metal vapor is evaporated.

At this time, since the convection prevention plates 16 are closely arranged at small intervals in the storage recess t4 of the evaporation crucible 13 so as to block the cross section in the transverse direction, the molten metal in the storage recess 14 is Convection is prevented on the liquid level of the raw material 15 by the surface friction of the convection prevention plate 16, and heat loss due to convection is reduced, resulting in a significant improvement in energy efficiency. Figure 2 shows the convection prevention plate 1.
Although an example has been shown in which all of the convection prevention plates 6 are energized, it is also possible to energize only the plurality of convection prevention plates (6) in the center.

In addition, when the convection prevention plate 16 is formed of a porous tungsten material, even if a plurality of convection prevention plates 16 are placed in the storage recess 14 of the evaporation ruppo 13, the convection prevention plate 16 is made of a porous material. The molten metal of the metal raw material 15 can be diffused and permeated, and the substantial evaporation area of the evaporation crucible 13 can be increased. Therefore, the evaporation efficiency of the metal raw material 15 can be increased. Furthermore, the molten metal that has penetrated into the porosity of the convection prevention plate 16 due to diffusion does not come into contact with the side wall of the evaporation crucible 13 and is not cooled by this side wall, thereby improving the evaporation efficiency.

Furthermore, since the notches 26 and 27 forming supply paths are formed at the top of the convection prevention plate 16, the supply of the metal raw material 15 is not subject to any spatial restrictions.

By arranging the convection prevention plate 16 in the longitudinal direction of the storage recess 14 in the evaporation crucible 13, it is possible to block the transverse cross section in the transverse direction, thereby actively preventing the convection of the molten metal of the metal raw material 15. This can significantly improve the evaporation efficiency of the metal raw material 5.

Moreover, the metal raw material 15 accommodated in the evaporation crucible 13 is
Since heating can be performed using electric Joule heat generated by energization, there is no need for an electron gun or a deflection magnetic field for deflecting the electron beam from the electron gun, which is advantageous in terms of cost.

In one embodiment of the present invention, an example was shown in which the metal raw material is heated, melted, and evaporated using a convection prevention plate disposed in the evaporation crucible. Heating may be performed by an electron beam emitted from an electron gun, or heating by the electron beam may be combined with electric Joule heating by a convection prevention plate.

〔Effect of the invention〕

As described above, in the metal vapor generator according to the present invention, a plurality of convection prevention plates are arranged in parallel in the storage recess of the evaporation crucible, the convection prevention plates constitute a heating element, and the metal raw material is heated in joules. Because it is heated, melted, and evaporated by heat, it is possible to prevent the generation of convection by the molten metal in the evaporation crucible.
The evaporation efficiency of metal raw materials can be significantly improved.

In addition, if a notch is formed at the top of the convection prevention plate that partitions the four compartments of the evaporation crucible into a multilayered structure, metal raw materials can be replenished from a desired position through this notch, while the convection prevention plate When the material is made of a porous material, the molten metal of the metal raw material permeates and diffuses into the porous material, and the evaporation area of the evaporation crucible can be increased, so that the evaporation efficiency can be improved.

6 are diagrams for explaining the convection phenomenon of molten metal occurring in the evaporation crucible of a conventional metal vapor generator.

10... Isotope separation device, 11... Vacuum container, 12
... Steam enclosure container, 13... Evaporation crucible, 14.
...Storage recess, 15...Metal raw material, 16...Convection prevention plate, 17...Lead wire, 26.27...Notch.

Claims (1)

[Scope of Claims] 1. In a metal vapor generator in which a metal raw material for isotope separation is stored in a storage recess of an evaporation crucible, a plurality of convection prevention plates are placed at required intervals in the storage recess of the evaporation crucible. A metal vapor generator characterized in that the convection prevention plates are arranged in parallel and are formed as a heating element that heats the metal raw material, and the metal raw material is heated, melted, and evaporated by the heating element. 2. The convection prevention plate partitions the storage recess of the evaporation crucible into a multilayer structure, and a notch is formed at the top of the convection prevention plate, and the notch formation position is formed so that adjacent convection prevention plates are not aligned with each other. The metal vapor generator according to claim 1. 3. The metal vapor generator according to claim 1, wherein the convection prevention plate is formed of a porous material such as porous tungsten material.