JPH0460239B2 - - 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 a radioactive gas in a fission product gas and injects the ionized radioactive gas into a metal substrate.

[Technical background of the invention and its problems]

At nuclear power facilities such as nuclear fuel reprocessing plants, if a harmful amount of radioactivity is released into the environment, the effects may be wide-ranging and long-lasting, so ensuring safety is more important than in other general industries. We are required to make the rules even stricter.

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, the only gaseous waste is krypton-85 (hereinafter referred to as Kr-85), which has a long half-life of 10.7 years, so it is expected that nuclear power generation will increase in the future. , which could lead to global pollution in the future. Therefore, in addition to recovery technology, the important issue is the recovery of Kr-85.
How to store and dispose of it safely. Conventionally, methods have been considered to permanently preserve radioactive waste gas by sealing it in pressure-resistant pressure containers such as cylinders.

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 transferring stored gas each time.

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, a method of adsorbing it on zeolite, a method of fixing by ionization injection, etc. have been proposed.

However, the bomb storage method and the zeolite adsorption method have many problems that need to be improved before they can be put to practical use.

The ion implantation method not only enables disposal at room temperature and low pressure, but is also considered to be superior to other methods in terms of long-term safety.

FIG. 4 is a sectional view showing an outline of a conventional implantation apparatus for ionizing and implanting radioactive gas, and FIGS. 5 and 6 are cross-sectional views of the apparatus shown in FIG. 4.

Hereinafter, a conventional radioactive gas immobilization processing apparatus will be explained with reference to FIGS. 4 to 6.

In an ionization chamber 2 provided in a cylindrical container 1, a cylindrical electrode 5 to which a cooling pipe 3 and a lead wire 4 are attached is arranged at the center thereof. The cooling pipe 3 and lead wires 4 are insulated and sealed with an upper lid 7 by an insulator 6 such as a hermetic seal. In addition, the upper lid 7 of the container 1 is equipped with Kr.
A pipe 9 for introducing -85 gas is connected via a valve 8, and a pipe 11 for exhausting the inside of the container 1 is connected via a valve 10. Further, a cooling pipe is wound around the outer peripheral surface of the container 1. Note that the reference numeral 14 is a cumulative layer consisting of an ion-implanted Kr-85 ion layer and a coating layer sputtered with an electrode.
In FIGS. 5 and 6, reference numeral 15 indicates Kr-85 ions, and reference numeral 16 indicates sputter ions ejected from the electrode 5, respectively.

Next, a method for fixing and disposing Kr-85 gas in the above apparatus will be explained.

That is, in FIG. 4, the inside of the container 1 is heated to a desired degree of vacuum, e.g., 5×10 ^-7 by an evacuation device (not shown), such as an ion pump, an axial flow molecular pump, or an oil diffusion pump, which is connected to an evacuation pipe 11. After being exhausted to about Torr, valve 10 is closed to maintain a constant pressure inside container 1, valve 8 is opened and pipe 9
Kr from a cylinder, etc. (not shown) connected to
−85 gas and maintain a constant pressure in container 1, e.g.
When Kr-85 gas of about 0.1 Torr is filled, valve 8 is closed.

Further, a cooling medium such as water is caused to flow through the cooling pipe and 12 to cool the nickel electrode 5 and the container 1, for example. The Kr-85 is injected between the container 1 and the lead wire 4 connected to the nickel electrode 5, and can be impacted with enough energy to implant it, for example, 2 to 5 kV.
is applied to the nickel electrode 5 by a DC high voltage power supply (not shown) whose polarity can be alternately exchanged. When a positive high voltage of 2 to 5 kV is applied to the nickel electrode 5, the ionized Kr-85 ions 15 are injected and planted into the inner surface of the container 1 as shown in FIG. When a negative high voltage of 2 to 5 kV is applied to the nickel electrode 5, as shown in FIG. Ion is container 1
The 15 surfaces of Kr-85 ions planted on the inner surface of the glass are coated.

In this way, by applying a positive high voltage and a negative high voltage of 2 to 5 kV to the nickel electrode 5 at regular intervals, for example, for 5 seconds when coating, and for 1 second when implanting Kr-85 ions 15, the cylindrical A metal coating layer of a Kr-85 ion layer and a nickel ion layer is accumulated on the inner surface of the shaped container 1 to form a cumulative layer.

However, with conventional radioactive gas ionization implantation and fixation devices, the ionization and fixation treatment device is operated regardless of whether the amount of radioactive gas to be treated is large or small, and the device is stopped once the immobilization process is completed. become. When an ionization fixation processing device is brought online, it is undesirable to repeatedly start and stop the device from the viewpoint of device maintenance, power consumption, and labor savings, and if anything, it is preferable to operate the device continuously. .

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to increase the ionization throughput, that is, throughput capacity, of the ionization fixation processing equipment in response to the throughput of radioactive gas, such as Kr-85, generated during nuclear fuel reprocessing. An object of the present invention is to provide a radioactive gas immobilization processing device that can be adjusted.

[Summary of the invention]

In the radioactive gas immobilization processing apparatus according to the present invention, a cylindrical electrode is arranged in a cylindrical container into which the radioactive gas to be processed is introduced, and a high voltage of, for example, 2 to 5 kV with a different polarity is applied between the cylindrical electrode and the container. The radioactive gas is ionized to cause a glow discharge, and a negative high voltage of -2 to -5 kV is applied to the electrode, and the ions are bombarded to generate sputtering ions from the electrode surface. A coating layer is formed on the inner surface of the container.

After that, a negative high voltage of -2 to -5 kV is applied to the cylindrical container to implant the ions into the inner surface of the container to form an ionized layer, and the coated layer and the ionized layer are alternately accumulated. It is a device that captures images. The inside of the cylindrical container of this device forms an electrically insulated ionization chamber divided into multiple parts.
Each ionization chamber is provided with a member for selectively or simultaneously implanting ionization.

[Embodiments of the invention]

Hereinafter, the radioactive gas immobilization processing apparatus of the present invention will be described in detail with reference to FIGS. 1 to 3.

That is, FIG. 1 is a cross-sectional view showing a first embodiment of the radioactive gas fixation processing apparatus of the present invention, and the same parts as in FIG. 4 are designated by the same reference numerals, and the explanation of the overlapping parts will be omitted.

An electrode 20 arranged in the center of the cylindrical container 1,
21 and 22 are divided into three equal parts along the axial direction,
An insulator 23 is interposed in each divided portion. These electrodes 20, 21, and 22 are then electrically insulated to form a first ionization chamber 12, a second ionization chamber 33, and a third ionization chamber 34, respectively. Further, three insulators 24 made of, for example, hermetic seals are provided on the side surface of the container 1 facing each electrode 20, 21, 22, and lead wires 25, 2 are connected independently through the insulators 24.
6, 27, and these lead wires 25, 2
Switches 28, 29, and 30 are attached to switches 6 and 27. These switches 28, 29, 3
The other end of 0 changes the polarity at regular intervals, for example, 2.
It is connected to a high voltage supply power source 31 that applies a high voltage of ~5 kV, and the other end of the power source 31 is connected to the container 1 . In this way, the first embodiment has the same configuration as that in FIG. 1 (same reference numerals) except that it is divided into a first ionization chamber 32, a second ionization chamber 33, and a third ionization chamber 34. There is.

Next, a method for actually ionizing Kr-85 gas as an example of a radioactive gas to be processed using the processing apparatus in the first embodiment will be described in detail.
In this example, nickel is used as the material for the electrodes 20, 1, and 22. If the amount of Kr-85 gas is relatively small, the ionization chamber 3 in the part corresponding to the electrode 20
In step 2, the Kr-85 gas is ionized and fixed, and the switch 28 is closed (switches 29 and 30 are closed).
(open state) High voltages of different polarities, for example, 2 to 5 kV, are applied at regular intervals between the container 1 and the electrodes 20 by a high voltage power source 31. 5 and 6, by repeatedly forming a coating layer on the inner wall of the container 1 by sputtering the electrode 20 and forming an ionization layer in the first ionization chamber 32. An ion layer 14 is formed and Kr-85 is ion implanted and fixed.

In addition, when processing a large amount of Kr-85 gas,
By also closing switches 29 and 30, the second
In the ionization chamber 33 and the third ionization chamber 34, the ion implantation and immobilization process can be performed simultaneously using the same method.

In this way, by adjusting the processing capacity in response to fluctuations in the amount of Kr-85 gas being processed, that is, fluctuations in the processing amount, it is possible to perform continuous operation with the aim of averaging the processing equipment. can.

FIG. 2 is a sectional view showing a second embodiment of the radioactive gas immobilization processing apparatus of the present invention. In Figure 2,
Components that are the same as those in FIG. 1 are designated by the same reference numerals, and explanations of overlapping components will be omitted.

This embodiment differs from the embodiment shown in FIG. 1 by using a common hollow cylindrical electrode 5, dividing the cylindrical container 1 into three parts, and interposing an insulator 23 between the divided surfaces to electrically insulate the first part. An ionization chamber 32, a second ionization chamber 33, and a third ionization chamber 34 are formed. Further, an insulator is provided on the bottom surface of the container 1, and the electrode 5 is connected to one end of a high voltage power supply 31 through the insulator 24. Further, lead wires are connected from the other end of the high voltage power supply 31 to the containers 1 of the first, second and third ionization chambers 32, 33 and 34 via switches 35, 36 and 37. The other configurations are the same as in FIG. 1.

In the apparatus having such a configuration, the switch 28 is closed, the switches 29 and 30 are left open, and Kr-85 ions are implanted in the first ionization chamber 32 by the same method as explained in FIG. Immobilization treatment can be performed.

FIG. 3 shows a third embodiment of the invention. This third embodiment has substantially the same structure as the apparatus shown in FIGS. 1 and 2, except that the container and the electrodes are shown separately. This embodiment also makes it possible to implement the ion implantation fixation treatment of Kr-85.

In the above embodiments, an example was explained in which nickel was used as the cylindrical electrode material, but the invention is not limited to this, and alloys of nickel and lanthanum, lanthanum,
Any metal that tends to cause sputtering, such as copper, copper alloy, gold, silver, aluminum, or aluminum alloy, can be applied to the present invention.

Furthermore, although the ionization treatment of Kr-85 gas has been described as an example of the gas to be treated, the present invention is also applicable to other radioactive gases or toxic gases, and the ionization chamber is not limited to being divided into three.

Note that the cooling medium is not limited to water, and it goes without saying that the high voltage applied between the cylindrical electrode and the container will vary depending on the size of the container and electrode.
Not limited to 5kV. Furthermore, the pressure of the gas introduced into the container is not limited to the values described above.

〔Effect of the invention〕

As explained above, according to the radioactive gas immobilization processing apparatus of the present invention, the ion implantation immobilization processing capacity can be adjusted depending on the amount of radioactive gas, such as Kr-85 gas, recovered at the fuel reprocessing plant. This makes it possible to continuously operate an online ion implantation and immobilization processing device. Therefore, there is no need to repeatedly start and stop the device, and maintenance of the device is easy.
It has great practical effects such as low power consumption and labor saving.

[Brief explanation of the drawing]

1 to 3 are vertical sectional views showing first to third embodiments of a radioactive gas immobilization device according to the present invention, and FIG. 4 is an outline of a conventional injection device for ionizing and injecting radioactive gas. FIGS. 5 and 6 are cross-sectional views of the apparatus shown in FIG. 1. 1... Cylindrical container, 3... Cooling pipe, 6, 23,
24... Insulator, 8, 10... Valve, 9, 11
... Pipe, 12 ... Cooling pipe, 14 ... Ion layer, 20, 21, 22 ... Cylindrical electrode, 25,
26, 27... Lead wire, 28, 29, 30...
Switch, 31...High voltage supply power supply, 32,3
3, 34...Ionization chamber.

Claims (1)

[Claims] 1. A cylindrical container into which a radioactive gas to be treated is introduced;
An electrode disposed within the container, a DC voltage power source that applies high voltages of different polarities between the electrode and the container, and a plurality of ionizers electrically insulated and divided into digits within the container. A radioactive gas immobilization processing device characterized by comprising a chamber. 2. The radioactive gas immobilization processing apparatus according to claim 1, wherein the electrode is a hollow cylindrical body that is divided into a plurality of parts via an insulator and is provided with a cooling pipe. 3 Between the container and the electrode, there are two to
A high voltage of 5 kV is applied, and 2 to 5 kV is applied to the electrode.
A negative voltage of 5 kV is applied to the vessel, and a voltage of 2 to
A radioactive gas immobilization process according to claim 1, characterized in that a negative voltage of 5 is applied and an ionized layer and a sputtered ion coating layer are alternately accumulated on the inner surface of the container. Device.