JPH0369080B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a radioactive gas immobilization processing apparatus that ionizes radioactive gas in a nuclear fission product gas and injects it into a metal substrate.

[Technical Background of the Invention] Nuclear fuel reprocessing plants and other nuclear facilities require other measures to ensure safety because if harmful amounts of radioactivity are released into the environment, the effects may be wide-ranging and long-lasting. The requirements are much stricter than in general industry. Reprocessing plants recover uranium and plutonium from spent fuel, but at the same time they must properly dispose of radioactive waste, including nuclear fission products. Among radioactive wastes, the only gaseous waste is krypton-85 (hereinafter referred to as Kr-85), which has a long half-life of 107 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. 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 to permanently preserve radioactive waste gas by sealing it in pressure vessels such as cylinders.

[Problems with Background Art] 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 vessels are required by law to undergo periodic pressure tests, which have the disadvantage of requiring complicated and dangerous work such as the need to transfer stored gas.

On the other hand, for the treatment of gaseous waste Kr-85, in addition to the method of storing it in a pressure vessel such as a cylinder, methods of adsorption on zeolite, ionization injection fixing method, etc. have been proposed. However, the cylinder storage method and the zeolite method have many problems that need to be improved before they can be put into practical use. Furthermore, although the ionization implantation method has a high possibility of being put to practical use, it cannot be said that a large amount of radioactive gas is ionized and ionized and implanted into the base material efficiently.

[Object of the Invention] The present invention has been made in view of the above circumstances, and its purpose is to use a cylindrical container containing radioactive gas, such as Kr-85, generated during nuclear fuel reprocessing, to apply an electric current between the nuclear container and the electrodes. A device that injects ion bombardment and coats electrodes by sputtering by alternately switching and applying the polarity of a high voltage at regular intervals, in which a magnet is placed outside or inside the cylindrical container. Increase the ionization density of Kr-85 gas,
The object of the present invention is to improve the efficiency of ionization injection and disposal of the radioactive gas.

[Summary of the Invention] That is, the radioactive gas immobilization processing apparatus of the present invention has a cylindrical electrode disposed in a cylindrical container into which radioactive gas is introduced, and a cylindrical electrode arranged in the cylindrical container into which the radioactive gas is introduced. The radioactive gas is ionized by applying a high voltage of different polarity to the ions, the ions are ionized and implanted into the inner surface of the container, and the surface of the electrode is sputtered with radioactive gas ions to coat the inner surface of the container. In the apparatus for cumulatively trapping ions and the coating layer by performing this action alternately, the ionization density of the radioactive gas is increased by disposing a magnet outside or inside the container. do.

[Embodiment of the Invention] Hereinafter, an embodiment of the radioactive gas immobilization processing apparatus of the present invention will be described in detail with reference to FIG. Ionization chamber 2 provided within the cylindrical container 1
A cylindrical electrode 5 to which a cooling chamber 3 and lead wires 4 are attached is arranged at its center. The cooling pipe 3 and the lead wires 4 are insulated and sealed to the upper lid 7 by a hermetic seal 6. Further, a pipe 9 for introducing Kr-85 gas is connected to the upper lid of the container 1 via a valve 8, and a pipe 11 for exhausting the inside of the container 1 is connected.
are connected via a valve 10. A cooling pipe 12 is wound around the outer peripheral surface of the container 1, and a cylindrical magnet 13 such as a ferrite magnet is arranged on the outer surface of the pipe 12. Note that reference numeral 14 indicates ion-implanted Kr-
This is an accumulation tank consisting of a sputtered coating of an 85 ion layer and an electrode. In FIGS. 2 and 3, reference numeral 15 indicates Kr-85 ions, and 16 indicates sputtered ions flying out from the electrode 5.
Figures 2 and 3 are cross-sectional views of Figure 1. Figure 2 shows an enlarged view of the process of implanting Kr-85 ions, and Figure 3 shows an enlarged view of the process of sputtering electrodes. It is shown schematically. Next, a method for fixing and disposing Kr-85 gas in the above apparatus will be explained. That is, in FIG. 1, the inside of the container 1 was evacuated to a desired degree of vacuum by an exhaust device (not shown) connected to an exhaust pipe 11, and then the valve 10 was closed to maintain the inside of the container 1 at a constant pressure. After that, open the valve 8 and supply Kr-85 gas from a cylinder, etc. (not shown) connected to the pipe 9.
The valve 8, which is filled with Kr-85 gas at a constant pressure, is closed. Further, a coolant such as water is flowed through the cooling pipes 3 and 12 to cool the electrode 5 and the container 1. A DC high voltage power source (not shown) capable of alternating the polarity of the high voltage that can be bombarded with sufficient energy to inject and plant Kr-85 between the container 1 and the lead wire 4 connected to the electrode 5 is used. is applied to the electrode 5. When a positive voltage is applied to the electrode 5, ionized Kr-85 ions 15
is injected into the inner surface of the container 1 and planted as shown in FIG. On the other hand, when a negative voltage is applied to the electrode 5 as shown in Figure 3, Kr-85
The ions 15 were bombarded and sputtered on the surface of the electrode 5, and the sputtered ions were planted on the inner surface of the container 1.
Coated on 15 Kr-85 ion faces.
By applying a positive voltage and a negative voltage to the electrode 5 at regular intervals in this manner, the Kr-85 ion layer and the metal coating layer are accumulated on the inner surface of the cylindrical container 1 to form a cumulative layer. That is, by arranging the magnet 13 according to the present invention on the outer circumferential surface of the container 1, a magnetic field is generated in the ionization chamber, thereby increasing the ionization density of Kr-85 ions, and the Kr-85 ions are more efficiently distributed inside the container 1 than before. 85 ions can be implanted, the sputtering efficiency of the electrode 5 is also increased, and the ion implantation efficiency of Kr-85 gas ions can be increased as a whole. As described above, the apparatus of the present invention can efficiently immobilize a large amount of Kr-85 gas.

Furthermore, when the Kr-85 gas in the container becomes diluted by being injected into the inner surface of the container 1 and captured, 01 gas may be sealed into the container 1 by the method described above.

4 to 6 are longitudinal cross-sectional views showing other embodiments of the present invention, and in each case, the same parts as in FIG. 1 are designated by the same reference numerals, and the explanation of the overlapping parts will be omitted. That is, in FIG. 4, a yoke 19 is arranged at the upper and lower parts of the cylindrical container 1 and a coil 20 is wound around it to form a magnet, and the magnet is energized to generate a magnetic field in the ionization chamber 2 to ionize it. This is an example of increasing the density. Fig. 5 shows that a filament 17 and an anode 18 are installed inside the container 1 through the upper and lower end plates 1a and 1b, and a voltage is applied between the filament and the anode 18 to cause Kr-85 gas discharge and ionization. This is an example in which the ionization density is further increased and the ion implantation amount is increased. 6th
The figure shows an example in which the device shown in FIG. 5 is further energized by a magnet in the vertical direction like the device shown in FIG. 4. Further, FIG. 7 shows an example in which a magnetic field is generated in the ionization chamber 2 by embedding a letter magnet 13 inside the electrode 5. FIG. 8 shows an example in which the device shown in FIG. 7 is further provided with the filament 17 and anode 18 of the device shown in FIG. 5 on both end plates 1a and 1b. In this embodiment, since electrons are emitted, the ionization density can be further increased.

FIG. 9 shows upper and lower end plates 1a and 1b of a cylindrical container 1.
In this example, a pair of cathodes 18 are provided facing each other through the container 1, and an anode 21 is provided inside the container 1 via a lead wire 22, which extends through the center of the side surface of the container 1.

The anode 21 applies a positive potential (for example, +5000V) to the cathode 18. The cathode 18 is a filament that emits hot electrons or a cold cathode that emits electrons. The electrons emitted from the cathode 18 are accelerated toward the center while moving spirally by the electric field generated by the potential of the anode 21 and the axial magnetic field. The electrons that have passed through the center continue their circular motion and move toward the opposing cathode 18, but are decelerated due to the electric field in the opposite direction, and the cathode 1
It will be repulsed just before the point 8, and then it will be accelerated in the opposite direction. Therefore, the electrons emitted from the cathode 18 make a reciprocating spiral motion between the cathode 18 - the anode 21 - the cathode 18, thereby dramatically increasing the ionization density of the gas discharge, thereby increasing the ion implantation and immobilization disposal efficiency. can be improved.

In each of the above-described embodiments, a ferrite magnet is used as the magnet, and in FIGS. 4 and 6, an electromagnet is used. Of course, it is not limited to. Also, the electrodes should be made of metals that are prone to sputtering, e.g.
Amorphous metals such as Ni-La and Ni-Y, Ni,
Single metals such as Cu and Ti or alloys can be used. Furthermore, metals suitable for ion implantation such as metals into which ions can be easily implanted, such as Cu and stainless steel, can be used. In the above example, the case where Kr-85 gas is ionized and fixed is mainly explained, but the gas to be ionized is not limited to Kr-85, and radioactive gases such as tritium, iodine, etc. Of course, this also applies. In addition, although we have explained the case where lead wires are attached to the cylindrical electrode, it goes without saying that the cooling pipe 3 itself can be used as the lead wire, and we have explained the case where water is used as the cooling medium. Of course, it is not limited to water.

[Effects of the Invention] As explained above, according to the radioactive gas immobilization processing apparatus of the present invention, the ionization density of Kr-85 gas can be increased because a magnetic field is generated in the ionization chamber by arranging the magnet. can. Therefore, the efficiency of ion implantation into the inner surface of the container and the sputtering efficiency of the electrode, that is, the coating efficiency, are increased.
The immobilization processing efficiency of Kr-85 gas has been significantly increased,
It has great practical effects.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view for explaining an embodiment of the radioactive gas immobilization processing apparatus of the present invention, and FIGS. 2 and 3 are cross-sectional views for explaining the operation of the apparatus shown in FIG. 1. , FIG. 4 to FIG. 9 are longitudinal sectional views showing other embodiments of the present invention. DESCRIPTION OF SYMBOLS 1...Cylindrical container, 2...Ionization chamber, 3...Cooling pipe, 4...Lead wire, 5...Cylindrical electrode, 6...Hermetic seal, 7...Upper lid, 8...Valve, 9...
Kr-85 introduction pipe, 10...Valve, 11...Exhaust pipe, 12...Cooling pipe, 13...Magnet, 14
...Kr-85 ion cumulative layer, 15...Kr-85 ion,
16...Spatsutaion.

Claims (1)

[Claims] 1. Applying high voltages of different polarities between a cylindrical electrode placed in a cylindrical container into which radioactive gas is introduced and the container, ionizing the radioactive gas, and ionizing and injecting the ions into the inner surface of the container. The surface of the electrode is sputtered with radioactive gas ions to coat the inner surface of the container to form a coating layer, and the ion layer and the coating layer are alternately used to cumulatively trap radioactive gas. An immobilization and disposal device for radioactive gas, characterized in that a magnet is disposed outside or inside the container.