JPH0225197Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a radioactive gas immobilization and disposal device for injecting and fixing a radioactive gas such as radioactive krypton gas into a base material using a particle accelerator.

[Technical background of the idea and its problems] Nuclear facilities such as nuclear fuel reprocessing plants have the potential to have wide-ranging and long-term effects if harmful amounts of radioactivity are released into the environment. They are required to ensure safety much more strictly than other general industries.

Reprocessing plants recover uranium and plutonium from spent fuel, but at the same time they must properly dispose of accompanying radioactive waste, including fission products.

Among radioactive waste, gaseous waste is krypton.
85 (hereinafter referred to as Kr-85), which has a long half-life of 10.7 years, so if nuclear power generation is expected to increase in the future, there is a risk that it will lead to global pollution in the future. There is.

Therefore, in addition to recovery technology, an important issue is how to safely store or dispose of recovered Kr-85. Conventionally, methods have been considered for permanently preserving radioactive waste gas by sealing it in a pressure vessel such as a cylinder.

However, the method of sealing in a pressure vessel has problems in terms of safe storage over a long period of time. For example, pressure resistance is poor due to gas leakage due to corrosion of the pressure vessel. In addition, pressure vessels are required by law to undergo periodic pressure tests, which have the disadvantage of requiring complicated and dangerous work such as transferring the stored gas each time. An apparatus for implanting and fixing ions into a base material using ion implantation is desired and has been proposed.

The conventionally proposed ion implantation method uses Kr-85 ions accelerated to a constant energy, for example.
Ions are implanted into aluminum foil, etc. at 50 keV, and in this case, the ion implantation layer can only be formed to a depth of about 200 Å from the surface of the aluminum foil.

The foil thickness of metal aluminum that can actually be used industrially is approximately 5 μm, so the metal utilization efficiency is not good when used for ion implantation fixation of Kr-85, and the volume reduction effect of radioactive waste gas is not sufficient. I can't say that.

[Purpose of the invention] The present invention was made in response to the conventional situation, and is used in a radioactive gas immobilization disposal device that ionizes and accelerates radioactive gas and immobilizes it by implantation. The purpose of the present invention is to provide a radioactive gas immobilization disposal device that enables multi-layer injection by forming a new metal film on a plate and implanting ions into the film as well, and which can effectively inject and immobilize gas in a thin metal layer. It is said that

[Summary of the invention] In other words, the invention consists of an ion source container that has an inlet for radioactive gas to be disposed of and is equipped with a cathode electrode and an anode electrode inside, and an ion source container that is connected to the ion source container via an insulating plate. an ion implantation chamber container having an accelerating electrode plate, an ion implantation chamber container provided adjacent to the acceleration electrode plate and having an exhaust port for reducing pressure, an ion implantation target plate disposed within the ion implantation chamber container, the cathode electrode, and the ion implantation chamber container provided adjacent to the acceleration electrode plate; A radioactive material comprising an anode electrode and a power source that applies a voltage to each of the accelerating electrode plates, the accelerating electrode plate having a beam passing hole tapered along the direction of incidence of the ion beam. This is a gas fixation and disposal device.

[Embodiment of the invention] The details of the invention will be described below with reference to an embodiment shown in the drawings.

Reference numeral 1 in the figure is an ion source container, and an inlet 3 is provided on the upper wall surface of the ion source container 1 to allow a radioactive gas containing, for example, Kr-85 to flow into the ion source 2 as a gas to be processed. and insulator 4
A cathode 5, e.g. a filament, is attached via.

Furthermore, an anode 6 made of, for example, a porous plate is fixed to the lower part of the ion source container 1, and an accelerating electrode plate 8 is arranged with an insulating annular plate 7 interposed therebetween.
This accelerating electrode plate 8 is provided with a large number of downwardly tapering beam passing holes 9, and these beam passing holes 9 are arranged at positions facing the ion emitting holes 10 of the anode 6.

An ion implantation chamber container 11 is provided on the lower surface of the accelerating electrode plate 8.
is provided. The ion implantation chamber container 11 has an exhaust port 12 for reducing the pressure inside the ion implantation chamber container 11, and an ion implantation target plate 14 is arranged on a bottom plate 13 on the bottom surface of the ion implantation chamber container 11. .

Further, the cathode power supply 15 applies voltage to both poles of the cathode 5, the anode power supply 16 applies voltage to the cathode 5 and the anode 6, and the acceleration voltage is applied to the anode 6 and the acceleration electrode plate 8. A power source 17 is provided respectively.

In the above device, the target gas to be disposed of is:
Thermionic electrons are introduced into the ion source 2 from the gas inlet 3, are maintained at a constant pressure in the space between the cathode 5 and the anode 6, and are emitted from the cathode 5, and a direct current is applied between the cathode 5 and the anode 6. Voltage
Arc discharge occurs due to the action of V _AND .

A plurality of ion emitting holes 10 are formed in the anode 6, and positive ions in the plasma generated by arc discharge are emitted from the ion emitting holes 10 of the anode 6 by the gas flow accompanying the exhaust from the exhaust port 12. and is accelerated by the action of the negative potential applied to the accelerating electrode plate 8.

Since the accelerating electrode plate 8 is provided with inverted cone-shaped beam passing holes 9 as shown in the figure at positions corresponding to each ion emitting hole 10 of the anode 6, a part of the accelerated gas ions i pass through this beam. The ions pass through the passage hole 9 and reach the ion-implanted plate 14, where they are implanted to a surface depth that corresponds to the acceleration energy.

However, the remainder of the accelerated gas ions i impact the vicinity of the beam passage hole 9 of the accelerating electrode plate 8, sputtering the metal or alloy constituting the accelerating electrode plate 8. The sputtered atoms S emitted from the accelerating electrode plate 8 by sputtering form a film on the surface of the ion-implanted plate 14.

In this way, film formation and ion implantation proceed simultaneously, and as a result, the film grown on the ion-implanted plate 14 comes to contain a large amount of ion-implanted gas atoms.

Such means make it possible to retain gaseous atoms in the sputter coating very efficiently and stably for a long period of time. This operation must be carried out in an optimized vacuum atmosphere, and the exhaust port 12
It is evacuated in a controlled manner through the

Note that it is also possible to set a potential gradient between the accelerating electrode and the target, as is done in conventional ion implanters. In this case, as shown in FIG. 2, an insulator 100 is interposed between the acceleration electrode plate 8 and the bottom plate 13 (ion implantation target plate 14), and the acceleration electrode plate 8 and the bottom plate 13 (ion implantation target plate 14) are connected to each other. During this period, a voltage is applied from the ion implantation power source 101.

[Effects of the invention] As explained above, according to the radioactive gas immobilization and disposal apparatus of the invention, some of the ions in the gas to be disposed of sputter on the ion accelerating electrode, thereby forming a new metal coating on the implanted plate. can be formed to enable multilayer ion implantation.

In addition, since the ion accelerating electrode itself is used as the sputter source, the mechanism is simple, and since ions are implanted into the sputter layer, there is no need for significant high-energy acceleration of ions, resulting in smaller equipment and reduced power consumption. It is effective for

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view partially showing an embodiment of the radioactive gas immobilization and disposal device according to the present invention;
FIG. 2 is a longitudinal cross-sectional view showing another radioactive gas immobilization and disposal device partially in block form. 1...Ion source container, 2...Ion source, 3...
Inflow port, 4... Insulator, 5... Cathode, 6...
Anode, 7... Insulating annular plate, 8... Accelerating electrode plate, 9... Beam passing hole, 10... Ion release hole, 11... Ion implantation chamber container, 12... Exhaust port, 13... Bottom plate, 14...Ion implantation plate, 1
5...Cathode power supply, 16...Anode power supply, 1
7... Acceleration power source.

Claims (1)

[Scope of utility model registration request] An ion source container having an inlet for the radioactive gas to be disposed of and equipped with a cathode electrode and an anode electrode therein, an accelerating electrode plate provided on the ion source vessel via an insulating plate, and an accelerating electrode plate adjacent to the accelerating electrode plate. A voltage is applied to an ion implantation chamber container having an exhaust port for reducing pressure, an ion implantation target plate disposed within the ion implantation chamber container, the cathode electrode, the anode electrode, and the acceleration electrode plate. 1. An apparatus for immobilizing and disposing of radioactive gas, characterized in that the accelerating electrode plate has a tapered beam passing hole formed along the direction of incidence of the ion beam.