JPH04254798A - Apparatus for immobilization treatment of radioactive gas - Google Patents

Abstract

PURPOSE:To enhance the reliability of the title apparatus by providing sufficient strength and sealing function to an immobilizing container not only during operation but also at the time of an earthquake. CONSTITUTION:Insulators 20a, 20b are interposed between the body flanges 2a, 2b formed to the end parts of a body plate 2 formed as an ion injection electrode and the lid bodies 4,18 facing to the end surfaces of the body flanges to close the opening parts of the body plate 2. Sealing materials are arranged to both surfaces of the insulators and the body plate and the lid bodies are clamped by bolts 23,27 to which insulating treatment is applied to constitute an immobilizing container.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a radioactive gas immobilization processing device that ionizes radioactive gas generated in a nuclear fuel reprocessing plant, etc., and injects the gas ions into a metal structure for immobilization. The present invention relates to improvements in immobilization containers used in the device.

0002

[Prior Art] In nuclear 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, compared to other general industries. There is a strict obligation to ensure safety. For example, in a nuclear fuel reprocessing plant that recovers uranium and plutonium from spent nuclear fuel, radioactive gases containing fission products are generated during the spent nuclear fuel shearing and melting processes. Among these, the radioactive gas that is most likely to cause problems is krypton-85 (hereinafter abbreviated as Kr-85), which has a half-life of approximately 10
．． Seven years is a very long time, so efforts are being made to develop technology that will allow it to be stored safely for a long period of time.

[0003] The radioactive gas storage methods that have been developed to date include the high-pressure cylinder storage method in which the radioactive gas is stored in a pressure container such as a high-pressure cylinder, and the Kr-8 storage method.
Generally known methods include a zeolite adsorption method in which 5 is adsorbed on zeolite, an ion implantation method in which a radioactive gas is ionized and injected into the metal structure, and the like.

[0004] However, in the high-pressure cylinder storage method, since it is mandatory to periodically conduct a pressure test of the storage container storing the radioactive gas, it is necessary to transfer the stored gas to a different container each time. Requires complicated work. Furthermore, since the zeolite adsorption method requires processing of Kr-85 at high temperature and high pressure, there are many problems before it can be put to practical use. On the other hand, ion implantation method
Since treatment can be performed at room temperature and low pressure, it can be said to be advantageous in terms of economy and stability compared to the above-mentioned high-pressure cylinder storage method and zeolite adsorption method.

FIG. 3 is a sectional view showing a conventional general radioactive gas immobilization processing apparatus that immobilizes radioactive gas by the above-mentioned ion implantation method.

In the figure, reference numeral 1 denotes a solidification container with a closed structure for immobilizing radioactive gas, and this immobilization container 1 has the following features:
An ion implantation electrode 2 constituting a cylindrical body plate, an anode bottom (lid) 4 connected to the lower part of the ion implantation electrode 2 via a ring-shaped insulator 3a, and an upper part of the ion implantation electrode 2. an anode flange 5 for connection coupled to the anode flange 5 via an insulator 3b, and an anode lid (lid body) 6 fastened to the upper surface of the anode flange 5 with bolts and nuts (not shown).
It is composed of.

The anode cover 6 has an intake pipe 7 and an exhaust pipe 8.
is connected, and radioactive gas is introduced into the immobilization container 1 through the intake pipe 7 using a vacuum pump (not shown) connected to the exhaust pipe 8. A cylindrical sputter electrode 9 is provided in the immobilization container 1, and a voltage of 1 KV or more is applied to the sputter electrode 9 from a sputter power source 10.
In addition, an ion implantation power source 1 is connected to the ion implantation electrode (body plate) 2.
The radioactive gas introduced into the immobilization container 1 is immobilized by applying a voltage of 1 to 1 KV or less.

A water-cooled tube 12 is connected to the upper part of the sputtering electrode 9 through an insulator 13 having a hermetic seal provided in the central opening of the anode cover 6.

In the radioactive gas immobilization processing apparatus configured as described above, immobilization occurs when the gas pressure in the immobilization container 1 and the voltage applied to the ion implantation electrode 2 and the sputtering electrode 9 satisfy appropriate conditions. It is known that a glow discharge occurs within the container 1 and that the radioactive gas within the immobilization container 1 is ionized by this glow discharge.

For example, the gas pressure inside the immobilization container 1 is set to 10
When a voltage of 1 KV or less is continuously applied to the ion implantation electrode 2 and a voltage of 1 KV or more to the sputtering electrode 9 while maintaining the setting at -1 to 10-3 Torr, the radioactive gas in the immobilization container 1 glows. The gas is ionized by the discharge, becomes gas ions 14, is accelerated toward the sputter electrode 9, and collides with the surface of the sputter electrode 9, as shown in FIG. At this time, the sputtered metal 1 is transferred from the sputtered electrode 9.
5 fly out and collide with the surface of the opposing ion implantation electrode 2 to form a metal accumulation layer 16. Further, some of the gas ions 14 are accelerated toward the ion implantation electrode 2 and injected into the metal accumulation layer 16 formed on the surface of the ion implantation electrode 2, as shown in FIG.

[0011] Therefore, by performing such operations until the radioactive gas in the immobilization container 1 is exhausted, Kr-
A radioactive gas such as Kr-85 can be injected and fixed into the metal cumulative layer 16 of the sputtered metal 15 formed on the surface of the ion implantation electrode 2, making it possible to safely store Kr-85 for a long period of time.

Note that reference numeral 17 is a water cooling tank that surrounds the ion implantation electrode 2 and cools it.

By the way, the immobilization container 1 in which the radioactive gas is immobilized needs to be maintained in a vacuum state in order to generate glow discharge, and for this reason, it cannot function as a tensile strength member as a pressure container. I need to have it. Moreover, it is necessary to insulate between the body plate forming the ion implantation electrode 2 and the anode flange 5 for connecting the anode bottom (cover) 4 and the anode cover (cover) 6 adjacent to this body plate 2. As described above, insulators 3a and 3b are interposed between the body plate 2 and the anode bottom 4, and between the body plate 2 and the anode flange 5.

[0014] Details of the connecting portion of one insulator 3b are shown in FIG. 6 (the other insulator 3a is shown in parentheses).
.

That is, since ceramic is generally used as the insulator 3b (3a), this insulator 3b (3a)
In order to prevent cracking due to thermal expansion in a), insulator 3
b (3a) cannot be directly welded to the body plate 2 or the anode flange 5 (anode lid 4). For this reason, a ceramic sealing metal 3c made of an Fe, Ni alloy called Kovar is used.
The body plate 2 and the insulator 3b, and the insulator 3b and the anode flange 5 (the anode cover 4 and the insulator 3a, and the insulator 3a and the body plate 2) are connected through the .

That is, the insulator 3b (3a) and the ceramic sealing metal 3c are connected by brazing with silver solder 3d, and the ceramic sealing metal 3d, the body plate 2 and the anode flange 5 (anode lid 4) ) are connected to each other by welding 3e.

[0017]

However, although ceramics (insulators 3a, 3b) are generally strong against compressive force, they do not have sufficient strength against tensile force. Further, since the insulators 3a, 3b and the ceramic sealing metal 3c are brazed with silver solder 3d, it is often not possible to expect such strength.

Therefore, as in the conventional example, the anode bottom 4 and the anode flange 5 are connected to the body plate 2 with the insulators 3a and 3b interposed therebetween, and the anode lid 6 is further covered to form a fixed container with a sealed structure. 1, the ceramic insulators 3a and 3b themselves and the silver solder portion 3d do not have sufficient strength, making it unsuitable for use as the immobilization container 1 as a pressure container. There was a problem that when a lateral load was applied to the immobilization container 1 during an earthquake, the insulators 3a, 3b and the silver solder 3d did not have sufficient strength.

The present invention has been made in view of these points, and it provides the immobilization container with sufficient tensile strength and sealing function not only during operation but also during earthquakes, thereby preventing radioactive The purpose of the present invention is to provide a gas fixation processing device with improved reliability.

[0020]

[Means for Solving the Problems] In order to achieve the above object, the present invention introduces a radioactive gas into an immobilization container having a closed structure, and introduces a radioactive gas into an ion implantation electrode and a sputtering electrode provided in the immobilization container. A high voltage is applied to generate a glow discharge, the radioactive gas is ionized by the glow discharge, and the gas ions are injected and fixed into a metal cumulative layer of sputtered metal formed on the surface of the ion implantation electrode. In the radioactive gas immobilization processing apparatus, an insulator is provided between a body flange formed at the end of the body plate constituting the ion implantation electrode and a lid that faces the end face of the body flange and closes the opening of the body plate. The immobilized container is constructed by placing a sealing material on both the front and back surfaces of the insulator, and tightening the body flange and the lid with insulating bolts.

[0021]

[Operation] According to the present invention configured as described above, the tensile force generated between the body plate and the lid body is counteracted by the insulating bolts that tighten and fix both at the body flange. This prevents a tensile load from acting on the insulator interposed between the body plate and the lid, allowing the insulator to be used as a non-tensile strength member, and also allows the insulator to be This allows the immobilization container to have sufficient tensile strength and sealing function not only during operation but also during an earthquake.

[0022]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the same parts as those shown in FIG. 3 are given the same reference numerals, and explanations of those parts will be omitted.

FIG. 1 is a sectional view of a radioactive gas fixation processing apparatus showing an embodiment of the present invention, and FIG. 2 is an enlarged view of section A in FIG.

In the figure, reference numeral 18 denotes a flanged anode lid (lid body) constructed by integrating the anode flange 5 and anode lid 6 in the conventional example, and the peripheral edge of the flanged anode lid 18 is the flange portion 18a. Furthermore, body flanges 2a and 2b are formed at both upper and lower ends of the body plate (ion implantation electrode) 2, respectively.

A ceramic insulator 20a is placed between the upper surface of the peripheral edge of the anode bottom (lid) 4 and the lower end surface of the lower body flange 2a, and between the lower surface of the flange portion 18a of the flanged anode lid 18 and the upper surface of the lower body flange 2a. A ceramic insulator 20b is also interposed between the upper end surface of the body flange 2b.

Here, in the mounting portion of the insulator 20b, as shown in FIG.
In order to achieve a sufficient sealing function even when the body flange 2b and the anode lid 1 with flanges
An O-ring groove 21 is provided around the surface of each of the flange portions 18a of 8, and an O-ring 22 as a sealing material is fitted into each O-ring groove 21, respectively.

Each of these O-rings 22 is inserted into each O-ring groove 2.
The flanged anode cover 18 is connected to the upper end of the body plate 2 by tightening them into the bolts 23 and 1.
This is done by tightening the nut 24. When the bolt 23 and nut 24 are used to tighten the body flange 2a and the flange portion 18a of the flanged anode cover 18, a flanged insulator is provided around the bolt 23 to prevent electrical conduction between both 2a and 18a. The bolt 23 is provided with insulation in the body 25. Further, a flat washer 26 is inserted under the bolt 23 in order to prevent the flanged insulator 25 from being damaged when the bolt 23 is tightened.

[0028] Also, in the mounting portion of the insulator 20a,
The anode bottom 4 is connected to the lower end of the body plate 2 by tightening bolts 27 which are provided with a configuration substantially similar to that described above and which are insulated.

That is, an anode bottom (cover) 4 is placed at the lower end of the body plate (ion implantation electrode) 2, and an insulator 2 is placed at the body flange 2a.
By tightening the bolts 27 while interposing
8 are connected to each other by tightening bolts 23 with an insulator 20b and an O-ring 21 interposed at the body flange 2b, thereby forming a fixed container 1 having a closed structure.

In this way, the ceramic insulator 20b is interposed between the body flange 2b of the body plate 2 and the flange portion 18a of the flanged anode cover (cover body) 18, and
By installing O-rings 22 on both sides of this insulator 20b and further tightening them with bolts 23 that take insulation measures to form the immobilization container 1, it is possible to prevent a tensile load from acting on this insulator 20b. Moreover, since the sealing function can be maintained, the immobilization container 1 configured in this way
By using this, a radioactive gas fixation processing device can be made which is highly reliable in terms of both strength and sealing performance.

[0031]

[Effects of the Invention] As explained above, according to the present invention,
This prevents tensile loads from acting on the insulators that make up the immobilization container and maintains the sealing function. A radioactive gas immobilization processing device with high sealing performance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention.

FIG. 2 is an enlarged view of part A in FIG. 1.

FIG. 3 is a sectional view showing a conventional radioactive gas fixation processing apparatus.

FIG. 4 is a cross-sectional view illustrating the operation of the radioactive gas fixation processing device.

FIG. 5 is a cross-sectional view illustrating the operation of the radioactive gas fixation processing device.

FIG. 6 is an enlarged view of the insulator mounting part in FIG. 3.

[Explanation of symbols]

1 Immobilization container 2 Ion implantation electrode (body plate) 2a, 2b Body flange 4 Anode bottom (lid) 9 Sputter electrode 14 Gas ions 15 Sputtered metal 16 Metal cumulative layer 18 Anode lid with flange (lid body) 18a Flange part 20a, 20b Insulator 22 O-ring (sealing material) 23, 27 bolts 25 Flange insulator

Claims (1)

[Claims] 1. A radioactive gas is introduced into an immobilization container having a sealed structure, and a high voltage is applied to an ion implantation electrode and a sputtering electrode provided in the immobilization container to generate a glow discharge. In a radioactive gas immobilization processing apparatus, the gas ions are ionized by glow discharge and are injected and immobilized into a metal cumulative layer of sputtered metal formed on the surface of the ion implantation electrode, which forms the ion implantation electrode. An insulator is interposed between the body flange formed at the end of the body plate and a lid that faces the end face of the body flange and closes the opening of the body plate, and a sealing material is applied to both the front and back surfaces of this insulator. 1. A radioactive gas immobilization treatment device, characterized in that the immobilization container is constructed by installing the body flange and the lid together with bolts provided with insulation.