JPH0631838B2 - Radioactive gas storage device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of use) The present invention relates to a radioactive gas storage device for ionizing a radioactive gas to be treated in a fission product gas and injecting it into a metal substrate for storage.

(Prior Art) Generally, in a nuclear facility such as a nuclear fuel reprocessing plant,
When a harmful amount of radioactivity is released to the environment, its effect may be wide-ranging and long-term, so it is obligatory to ensure safety as far as possible compared to other general industries. There is.

In the above-mentioned nuclear fuel reprocessing plant, uranium and plutonium are recovered from the spent nuclear fuel, but at the same time, radioactive waste including the associated fission products must be properly treated. Of the radioactive wastes, a potentially hazardous gaseous waste is krypton 85 (hereinafter referred to as Kr-85), but Kr-85 has a long half-life of 10.7 years and has a long life. Need to be stored.

Therefore, a device for surely storing radioactive gas such as Kr-85 is required, and at present, a device for immobilizing by a high pressure cylinder storage method, a zeolite adsorption method and an ion implantation method has been or is under development. is there.

FIG. 3 shows a conventional radioactive gas storage device using the ion implantation method, and the conventional device will be described with reference to FIG. That is, this radioactive gas storage device includes an outer cathode 1 as a hermetically sealed ion implantation electrode into which a gas to be treated is introduced, a cylindrical inner electrode 2 as a sputter electrode disposed inside the outer cathode 1, and Outer cathode 1
A high voltage is applied to the anode lid 3 for closing the upper end opening of the above, the introduction tube 4 for the gas to be treated attached to the lid 3, the suction tube 5 for decompressing the inside of the outer cathode 1, and the electrode 2. And a positive electrode bottom 12 provided at the bottom of the outer electrode 1. The inside of the outer cathode 1 is kept at a constant low pressure by a vacuum pump (not shown) connected to the suction tube 5. Note that reference numerals 10, 11, and 13 in the figure denote insulating members.

A voltage is applied between the outer cathode 1 and the inner electrode 2 by an external power supply 6.

In such a radioactive gas storage device, when the pressure in the outer cathode 1 and the voltage applied between the outer cathode 1 and the inner cathode 2 satisfy appropriate conditions, discharge may occur in the entire outer cathode 1. well known. This discharge causes K
The r-85 is ionized into an ionic state and discharge plasma is formed.

When a negative voltage of 1 kv or less is continuously applied to the outer cathode 1 and a negative voltage of 1 kv or more is applied to the inner cathode 2 by the power source 6, the Kr-85 ions 7 ionized by the discharge follow the electric field. The inner cathode 2 is accelerated and is incident on and collides with the surface of the inner cathode 2 to sputter the inner cathode 2. The sputtered metal atoms adhere to the inner surface of the opposing container 1 and are laminated to form a coating layer 8.

At the same time, some of the Kr-85 ions 7 are directly accelerated toward the electric field of the container 1 and are implanted and injected into the coating layer 8 described above.

While accumulating the coating layer 8 in this way,
Radioactive waste gas is continuously injected into the cumulative layer for immobilization.

The ion implantation method as described above is suitable as a method for storing radioactive gas, the container is completely sealed to prevent the radioactive gas from flowing out, and the pressure inside the container is kept lower than the external pressure. is doing.

(Problems to be solved by the invention) However, in the above device, the gas injection film is formed directly on the inner surface of the outer cathode. However, the material of the outer cathode and the constituent material of the film are different, and the gas in the film is different. However, since the density of the film is low, the adhesion is weak, and the formed film peels off from the inner surface of the outer cathode and induces abnormal discharge, which causes a problem that long-term operation cannot be performed.

Further, when the radioactive gas is stored, since the adhesion between the outer cathode material and the film is weak for the above reason, the formed film is easily peeled off from the wall by the thermal action and the physical action, and the radioactive gas is again released from the solid. May be released again. as a result,
The pressure inside the outer cathode rises, which may cause damage to the outer cathode, which is not preferable for safety.

The present invention has been made to solve the above problems, preventing peeling off from the inner surface of the outer cathode of the formed film,
Efficient, safe and highly reliable radioactive gas storage device that enables long-term operation, prevents re-emission of radioactive gas during storage, and enables stable long-term storage of radioactive gas Is provided.

[Structure of the Invention] (Means for Solving Problems) An outer cathode into which a gas to be treated is introduced, an inner cathode serving as a sputtering target arranged in the outer cathode, and an upper cathode provided above the outer cathode. In an apparatus for storing radioactive gas, comprising: an anode lid and an anode bottom provided on the bottom, and a DC high-voltage power source for applying a high voltage to each of the outer cathode and the inner cathode, the material of the outer cathode is a metal, and the shape is Is a cylindrical shape, and the gas introduction surface of the outer cathode is provided with an uneven surface composed of a large number of grooves along the circumferential direction in order to improve the adhesion.

(Operation) By forming a concave-convex surface on the inner surface of the outer electrode, the metal that is sputtered on the inner cathode forms a gas-containing film on the outer cathode that adheres to the inner surface of the outer cathode to ensure that gas is contained and preserved. It prevents the peeling of the adhesive film inside.

Therefore, in operation, normal discharge is not induced and continuous operation becomes possible. In addition, it becomes possible to store more stably for a long period of time after the end of operation,
The safety, reliability and efficiency of the device are improved.

(Embodiment) An embodiment of the radioactive gas storage device according to the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 1, the same parts as those in FIG. 3 are designated by the same reference numerals.

In the figure, reference numeral 1 is an outer cathode which serves as a substrate electrode, an inner cathode 2 which serves as a target material is arranged in the outer cathode 1, and an anode lid 3 is provided at an upper end opening of the outer cathode 1. . The lid 3 is attached with a gas introducing pipe 4 and a suction pipe 5 for reducing the pressure inside the outer cathode 1. Further, a DC high voltage power supply 6 is provided between the outer cathode 1 and the inner cathode 2 via lead wires 6a and 6b. In the figure, reference numerals 10, 11, 13 denote insulating members,
Reference numeral 12 indicates the anode bottom.

FIG. 2 is an enlarged cross-sectional view showing the outer cathode 1 in FIG. 1 and a part (A) of the coating film 8 formed by injecting a gas to be treated into the cathode 1.

That is, in the joint portion between the outer cathode 1 and the coating film 8 in FIG. 2, a fine uneven surface 9 is provided on the inner surface of the outer cathode 1.

As a processing method for forming the fine uneven surface 9, for example, parallel grooves of several μm are horizontally formed in a cylindrical shape by mechanical polishing.

When a negative voltage of 1 kv or less is continuously applied to the outer cathode 1 from the power source 6 and a negative voltage of 1 kv or more is continuously applied to the inner cathode 2, the Kr-85 ions 7 ionized by the discharge are accelerated along the electric field. , And collides with the surface of the inner cathode 2 to sputter the inner cathode 2. The sputtered metal atoms adhere to the uneven surface 9 that has been surface-processed on the inner surface of the opposing outer cathode 1 and are laminated to form a coating layer 8.

At the same time, some of the Kr-85 ions 7 are directly accelerated toward the electric field of the outer cathode 1 and implanted into the coating layer 8 described above.

On the other hand, the coating layer 8 adhered to the inner surface-treated uneven surface 9 of the outer cathode 1 has a thickness of several μm.
Due to the increase in the bonding area between the layer 8 and the uneven surface 9 due to the groove of m, the adhesion is strengthened and peeling does not occur due to the increase of frictional force and the relaxation of internal stress, and the abnormal discharge due to peeling is prevented. You can

As described above, the present invention is configured such that abnormal discharge during operation can be prevented and continuous operation can be stably performed for a long time by providing a fine uneven surface on the inner surface of the outer cathode to be the substrate electrode. It is a thing.

EFFECTS OF THE INVENTION According to the radioactive gas storage device of the present invention, abnormal discharge does not occur, so that the operation performance is improved, and the efficiency is improved because stable long-term continuous operation is possible.

Further, since the gas-containing layer is hardly peeled off from the outer cathode serving as the substrate electrode, it is possible to prevent the radioactive gas from being re-emitted from the storage device during storage and ensure safety during storage.

[Brief description of drawings]

FIG. 1 is a structural view showing an embodiment of a radioactive gas storage device according to the present invention in a partial cross section, FIG. 2 is an enlarged cross sectional view showing part A of FIG. 1, and FIG. It is a block diagram which shows a gas storage device by a partial cross section figure. 1 ... Outer cathode 2 ... Inner cathode 3 ... Anode lid 4 ... Gas introduction tube 5 ... Gas suction tube 6 ... Power source 7 ... Krypton 85 gas 8 ... Coating film 9 ... Uneven surface 10, 11 , 13 ... Insulation member 12 ... Anode bottom

Claims (1)

[Claims] 1. An outer cathode into which a gas to be treated is introduced, an inner cathode serving as a sputtering target disposed in the outer cathode, an anode lid provided on the upper portion of the outer cathode and an anode provided on the bottom portion. In a radioactive gas storage device comprising a bottom and a DC high-voltage power source for applying a high voltage to each of the outer cathode and the inner cathode, the material of the outer cathode is a metal, the shape of which is cylindrical, and the gas of the outer cathode. A storage device for radioactive gas, characterized in that an uneven surface composed of a large number of grooves along the circumferential direction is formed on the introduction surface.