JPS62284100A - Electropolishing decontamination device - Google Patents

Abstract

PURPOSE:To surely electropolish and decontaminate the upper and lower faces of a material to be decontaminated by loading the material to be decontaminated on an upward-expanding conical anode, providing cathodes on the inside and outside of the material to be decontaminated, and impressing a voltage between both electrodes. CONSTITUTION:The material 3 to be decontaminated such as pieces of a cut pipe is loaded on the upward-expanding conical anode 6 to secure the contact with the anode 6. The material 3 is dipped in an electrolyte 2. The cathode 4 for the internal face is set on the inside of the material 3 to be decontaminated, and the cathode 5 for the external face is set on the outside of the material to be decontaminated. An insulator 7 is provided under the anode 6 to fix the anode 6. A voltage is impressed between the anode 6 and the cathodes 4 and 5 to pass a current, and the material 3 to be decontaminated is electropolished. The positioning of the material 3 to be decontaminated is facilitated by this method, and the decontamination efficiency is improved.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to an electrolytic polishing method used to remove radioactive materials from metal articles contaminated with radioactive materials (hereinafter referred to as decontamination). Regarding dyeing equipment.

[Technical Background of the Invention] For example, electrolytic polishing decontamination equipment is generally used to decontaminate metal articles that are used in nuclear power plants and are contaminated with radioactive substances. This is because, according to the electrolytic polishing decontamination equipment, it is possible to remove not only radioactive substances deposited on the metal surface, but also radioactive substances stuck to the metal surface or radioactive substances that have entered the metal crystal. This is because it is easy to control minute polishing thickness. This electrolytic polishing decontamination apparatus will be explained below. In other words, a contaminated metal article (hereinafter referred to as the object to be decontaminated) is immersed in an electrolytic solution stored in an electrolytic cell, and a voltage is applied between the cathode provided in the electrolytic cell and the object to be decontaminated. The structure is such that the object to be decontaminated is decontaminated by electrolytically polishing the object to be decontaminated.

[Problems with Background Art] In general, cut pipe pieces account for a large proportion of the objects to be decontaminated. In the case of this pipe cut piece, the outer surface is also contaminated by 2Y contamination during cutting, but it is the inner surface that was in direct contact with the reactor subsystem cooling water that is mainly contaminated. Therefore, an electrolytic polishing decontamination device must be able to decontaminate not only the outer surface of the object to be decontaminated, but also the inner surface. However, conventional electrolytic polishing decontamination equipment is not configured to realize such a function, and there has been a demand for its realization.

[Purpose of the invention]

The present invention has been made based on the above points, and an object of the present invention is to provide an electrolytic polishing decontamination device that can reliably decontaminate not only the outer surface of an object to be decontaminated, but also the inner surface.

[Summary of the invention]

That is, in the electrolytic polishing decontamination apparatus according to the present invention, an object to be decontaminated is immersed in an electrolytic solution stored in an electrolytic tank, a cathode is disposed in the electrolytic tank, and a conductor is placed between the cathode and the object to be decontaminated. In an electropolishing decontamination device that decontaminates the object to be decontaminated by applying a voltage and flowing current to electrolytically polish the object to be decontaminated; The structure includes an external cathode disposed on the outside, and an anode that comes into contact with the objects to be decontaminated by loading the objects to be decontaminated, and has a conical shape that expands upward.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a longitudinal cross-sectional view of the electrolytic polishing apparatus according to this embodiment, and FIG. 2 is a cross-sectional view taken along the line -■ in FIG. Reference numeral 1 in the figure indicates an electrolytic cell, and this electrolytic cell 1 contains an electrolytic solution 2.
is stored.

An object to be decontaminated 3 is housed in the electrolytic solution 2, and an inner surface cathode 4 is installed inside the object to be decontaminated.

On the other hand, an external cathode 5 is installed outside the object 3 to be decontaminated. Further, an anode 6 is installed at the bottom of the electrolytic cell 1. The object to be decontaminated 3 is placed on this anode 6, thereby ensuring contact with the anode 6.

The anode 6 has an upwardly expanding conical shape, ie, a cone shape. The reason why the anode 6 is formed into a pincushion shape is as follows. First, simply by placing the object 3 on the anode 6, it is possible to center the object 3 with respect to the inner surface cathode 4 below the object 3, regardless of the diameter of the object. Moreover, by forming the dome shape, the inner surface of the object to be decontaminated 3 entirely faces the inner surface cathode 4, so that the flow of current is not partially obstructed. An insulating material 7 is installed below the anode 6, and the anode 6 is fixed by this insulating material 7. Further, the insulating material 7 includes the anode 6, the inner surface cathode 4,
It also has the function of electrically insulating the inner surface gap electrode bus bar 8 and the outer surface cathode 5 which are connected to the inner surface cathode 4 below. A weight 9 is placed on the object 3 to be decontaminated. This weight 9 has a conical recess 9 on its bottom side.
A is formed, and a through hole 9B communicating with the recess 9A in the vertical direction is formed.

The inner surface cathode 4 is disposed passing through this through hole 9B. By placing the weight 9, it is possible to ensure the contact between the anode 6 and the object 3 to be decontaminated, and also to facilitate centering of the upper part of the object 3 to be decontaminated with respect to the inner surface cathode 3. The upper opening 1A of the electrolytic cell 1 is closed by a lid 10. This structure is designed to prevent electrolyte droplets from scattering due to bubble bursting during electrolytic polishing.

The operation will be explained based on the above configuration. First, the lid 10 is removed and the inner surface cathode 4 is placed. And object to be decontaminated 3
is immersed in electrolyte 2 and placed on anode 6. As a result, centering is performed for the inner surface cathode 4 at the bottom of the object 3 to be decontaminated. After placing the object 3 to be decontaminated on the anode 6, a weight 9 is placed on the object 3 to be decontaminated. Weight 9
By placing the , the contact between the object 3 to be decontaminated and the anode 6 is ensured. At the same time, the upper part of the object 3 to be decontaminated relative to the inner surface cathode 4 is centered, and thereby the entire object 3 to be decontaminated is centered. After placing the weight 9 on the object 3 to be decontaminated, the upper opening 1A of the electrolytic cell 1 is opened from the lid 10.
occlude. Next, a voltage is applied between the anode 6, the inner surface cathode 4, and the outer surface cathode 5 to cause current to flow, and the object 3 to be decontaminated is subjected to electrolytic polishing. Note that if it is not necessary to decontaminate both the inner and outer surfaces of the object 3 to be decontaminated, there is no need to apply voltage to the unnecessary cathode, but only to one of the cathodes. do it. After a preset time has elapsed, the voltage application is stopped and the electrolytic polishing is completed. Then, the lid 10 is removed, and the object 3 to be decontaminated is taken out from the electrolytic cell 1 and transferred to the next step, for example, a cleaning step.

Then, the next object 3 to be decontaminated is placed in the electrolytic cell 1, and the same operations as described above are repeated.

Here, an example in which decontamination was actually performed using the electrolytic polishing apparatus according to this embodiment will be described. The objects to be decontaminated used here are:
This is a cut piece of piping that was actually used at a nuclear power plant, and was measured using a NaI scintillation counter for 10 hours.
Then, measure the gamma ray count rate of the object to be decontaminated, and calculate the following formula (
Relative count rate (RC) was calculated according to I).

RC=(specimen γ-ray count rate)/(background γ-ray count rate)...(I> Also, the relative standard deviation of the background γ-ray count rate (R
C) was calculated using the following formula (II).

Rσ=(background γ-ray count rate standard deviation)...
(I[) The measurement results are shown in Table 1 below.

Table 1 As is clear from Table 1, it can be seen that in this example, the metal articles were completely decontaminated and the radioactivity level was reduced to the background level.

As described above, according to the electrolytic polishing decontamination method according to the present embodiment, not only the outer surface of the object 3 to be decontaminated, but also the inner surface can be reliably decontaminated, and the decontamination efficiency can be improved.

By simply immersing the object 3 in the electrolyte 2, the object 3 comes into contact with the anode 6 and voltage can be applied, making the operation easy and improving the efficiency of decontamination work. It becomes possible to aim for. In particular, the anode 6 of this embodiment has an upwardly expanding conical shape, that is, a dome shape, so that the entire inner surface of the object 3 to be decontaminated faces the inner surface cathode 4.
As a result, it is possible to prevent a situation where current stops flowing partially, and it is possible to effectively improve decontamination efficiency. Furthermore, by making the anode 6 into a conical shape and by making the bottom side of the weight 9 placed above the object 3 to be decontaminated into a conical shape, the object to be decontaminated can be removed regardless of the diameter of the object 3 to be decontaminated. It becomes easy to center the inner surface cathode 4 of No. 3, and this also makes it possible to improve the efficiency of decontamination work.

〔Effect of the invention〕

As detailed above, the electrolytic polishing decontamination apparatus according to the present invention has
An object to be decontaminated is immersed in an electrolytic solution stored in an electrolytic tank, a cathode is placed in the electrolytic tank, a voltage is applied between the cathode and the object to be decontaminated, and a current is applied to cause the object to be decontaminated. In electrolytic polishing decontamination equipment that decontaminates decontaminated objects by electropolishing,
A cathode for the inner surface inserted into the object to be decontaminated, a cathode for the outer surface arranged to surround the object to be decontaminated, and a conical shape that spreads upward and comes into contact with the object to be decontaminated by loading the object to be decontaminated. It has a configuration including an anode that has a shape.

Therefore, it is possible to effectively decontaminate not only the outer side of the object to be decontaminated, but also the inner side, making it possible to greatly improve the decontamination efficiency. The object to be decontaminated can be positioned simply by placing the object on the anode, making it possible to improve the efficiency of decontamination work. In addition, by making the anode a conical shape that spreads upward, the entire inner surface of the object to be decontaminated faces the inner surface cathode, making it possible to prevent the situation where current flow is partially blocked. It is extremely effective in improving efficiency.

[Brief explanation of drawings]

1 and 2 are diagrams showing one embodiment of the present invention, in which FIG. 1 is a longitudinal sectional view of an electrolytic polishing decontamination device, and FIG.
It is a sectional view taken along ■-■ in the figure. 1... Electrolytic cell, 2... Electrolyte, 3... Decontaminated object,
4... Cathode for inner surface, 5... Cathode for outer surface, 6... Anode. Applicant's agent Patent attorney Takehiko Suzue = 11- Figure 1, Factor 2

Claims (1)

[Claims] An object to be decontaminated is immersed in an electrolytic solution stored in an electrolytic tank, a cathode is placed in the electrolytic tank, a voltage is applied between the cathode and the object to be decontaminated, and a current is applied to the object. An electrolytic polishing decontamination device that decontaminates by electrolytically polishing the object, an inner surface cathode inserted into the object to be decontaminated, an outer cathode arranged to surround the object to be decontaminated, and an object to be decontaminated. An electrolytic polishing decontamination device characterized by comprising: an anode having an upwardly expanding conical shape that contacts an object to be decontaminated by loading an anode;