JPH0545680B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement of an apparatus for electropolishing the inner surface of a tube, and more specifically, a method and apparatus for setting a tube in an apparatus for electropolishing the inner surface of a tube. Regarding.

(Prior Art) A fuel assembly in a nuclear reactor plant is constructed by vertically arranging a large number of cladding tubes (fuel pins) in which the fuel is sealed.

A phenomenon called swelling occurs in this cladding tube, in which the volume increases due to irradiation with fast neutrons in a nuclear reactor. However, since the spacing between the cladding tubes of the fuel assembly is narrow, there is a risk that the coolant flow path may be blocked due to swelling. For this reason, understanding the swelling of the cladding tube is important in evaluating the life of the cladding tube.

To calculate the swelling of the cladding, the density of the cladding is measured. The density of a cladding tube is measured using the immersion method, which uses the buoyancy of an object. In other words, the cladding tube is immersed in a liquid (pure water) to determine its volume, and the density is determined by dividing the weight by that volume value. ing.

Previously, prior to measuring the density of the cladding, the fuel was simply separated from the cladding by scraping and melting.

(Problem to be solved by the invention) However, in the past, there has been considerable variation in the data values of density measurements, which makes the measured values unreliable and requires an increase in the number of measurements to obtain accurate values. I didn't get it.

The reason for the variation in data values is corrosion on the inner surface of the cladding tube due to fission products produced by nuclear fission in the reactor and high heat (referred to as FCCI).
This is because the surface becomes rough and the permeability of liquid to the cladding tube deteriorates.

Therefore, the present inventor focused on surface treatment of the inner surface of the cladding tube by inner surface polishing before density measurement. On the other hand, since the cladding tube after irradiation is a highly radioactive substance, it is impossible to polish it directly by hand, and it is necessary to polish it in a cell box by remote control using a manipulator or the like. However, conventional electrolytic polishing equipment has problems in that remote control is difficult in practical terms, such as attaching the anode to the tube and arranging the tube so that the cathode is located at the center of the tube.

An object of the present invention is to provide an electrolysis device for the inner surface of a tube that can easily and reliably perform electrolytic polishing of the inner surface of the tube by remote control using a manipulator or the like.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a polishing table comprising an upper polishing table and a lower polishing table, the upper polishing table is provided with a tube holding section, and the tube holding section The upper polishing table is provided with an anode that comes into contact with the tube while it is held therein, and the lower polishing table is provided with an anode that is located inside the tube when the upper polishing table holding the tube is set on the lower polishing table. The polishing table is provided with a cathode, and the tube is first set on the upper polishing table, and then the upper polishing table is set on the lower polishing table.

(Example) An example of the present invention will be described below with reference to the drawings.

Density measurement is performed through the following steps.

After cutting the used cladding tube into small pieces, the fuel inside the cladding tube is roughly scraped off with a drill, and the remaining fuel is dissolved with heated nitric acid or the like to separate the fuel from the cladding tube. Next, the inner surface of the cladding tube is polished to remove surface roughness, and then the density is measured by an immersion method. The electrolytic polishing apparatus according to this embodiment is used for polishing the inner surface of a cladding tube.

The overall outline of the electrolyzer will be explained with reference to FIG.

Since the cladding is radioactive, the electrolyzer is placed in a cell box 1 for radiation shielding.
The electrolytic cell 2 is provided with a heater 3 that heats the electrolytic solution to a temperature suitable for electrolysis.

The electrolytic cell 2 and the external tank 4 made of synthetic resin are connected to the piping 5.
have been contacted through. The external tank 4 is used to supply new electrolyte and return waste liquid after electrolysis. The piping 5 is composed of two pipings 5a and 5b that open to the electrolytic cell 2 and the external tank 4, and a piping 5c that connects the piping 5a and the piping 5b in the middle. A pump 6 is provided in the pipe 5c, and flow path switching valves 8a, 8b are provided in the connecting portions 7 of the pipes 5a, 5b with the pipe 5c.

During electrolysis, the switching valves 8a and 8b are in the state shown in FIG. 1, and the electrolytic solution circulates between the electrolytic cell 2 and the pump 6. The reason for circulating the electrolyte will be described later. Before electrolysis, the switching valve 8b is switched to the opposite side from the illustrated state, and the electrolytic solution is sent from the external tank 4 to the electrolytic tank 2. After electrolysis, the switching valve 8a is switched to the opposite side from the illustrated state, and the electrolytic solution is returned from the electrolytic cell 2 to the external cell 4.

A polishing table 9 is arranged inside the electrolytic bath 2 . The polishing table 9 includes an upper polishing table 9a and a lower polishing table 9.
A lower polishing table 9b is placed at the bottom of the electrolytic cell 2, and an upper polishing table 9a is set above it. The lower polishing table 9b is provided with a guide column 10 for slidingly guiding the upper polishing table 9a.

A frame-shaped grip 11 is provided on the upper polishing table 9a, and the grip 11 is lifted and moved by a manipulator or crane (not shown).
Further, the upper polishing table 9a includes a storage hole 12 passing through the storage hole 12 vertically and a step portion 1 projecting circumferentially below the storage hole 12.
3 constitutes a tube holding section 14. A stainless steel cladding tube 15 is vertically held in this tube holding portion 14 . Furthermore, on the upper polishing table 9a,
An anode 16 is provided and contacts the outer surface 17 of the cladding tube 15 held in the tube holder 14 .

A pipe 5a for supplying an electrolytic solution to the electrolytic cell 2 is connected to the lower polishing table 9b, and a communication path 19 is provided that communicates from the opening 18 of the pipe 5a to the lower opening of the storage hole 12 of the upper polishing table 9a. There is. In the opening 20 of the communication path 19 in the lower polishing table 9b,
A rod-shaped cathode 21 is provided vertically, and this cathode 21
is located at the center inside the cladding tube 15.

The anode 16 and the cathode 21 are connected to a cord 23 to a DC power source 22 located outside the cell box 1.
connected via.

The electrolytic solution is continuously discharged upward from the communication path 19 inside the cladding tube 15 and circulates between the pump 6 and the electrolytic cell 3.

The reason for creating a continuous flow inside the cladding tube 15 in this way is as follows.

During electrolysis, bubbles of oxygen, hydrogen, etc. are generated at the anode and cathode, and metal ions (anolyte) are dissolved from the anode. In conventional electrolytic polishing devices for the inner surface of tubes, air bubbles remain in the tube, causing changes in current density and uneven polishing.
Further, there was a problem in that the anolyte accumulated around the anode (inner surface of the cladding tube), making it difficult for current to flow, and forming grooves on the inner surface of the tube due to the anolyte flowing up and down.

In this embodiment, bubbles and anolyte can be continuously removed by the continuous flow of the electrolytic solution, so that the inner surface 24 of the cladding tube 15 can be evenly polished.

Next, the structure of the upper polishing table 9a and the lower polishing table 9b will be described in detail with reference to FIGS. 2 and 3.

In FIGS. 2A and 2B, the upper polishing table 9a is shown. The main body 25 of the upper polishing table 9a is made of an insulator such as hard vinyl chloride, and has a plurality of storage holes 12 in two rows in its length direction. It is being A guide groove 27 is formed in the upper part of the upper polishing table 9a in a concave shape so as to gradually become narrower from the side end 26 toward the storage hole 12. Since the cladding tube 15 is guided to the storage hole 12 along this guide groove 27, the operability with the manipulator becomes better. Storage hole 1
A stepped portion 13 on which a cladding tube 15 is placed is provided below the cladding tube 2 .

A support rod 28 erected near the storage hole 12 is provided with an anode 16 made of stainless steel or the like. The anode 16 is made up of two pieces with widened tips, which are spread apart by the outer surface 17 of the cladding tube 15 housed in the storage hole 12 and come into contact with each other across the outer surface 17 due to the spring back action (Fig. 1, (See Figure 3 B).

A guided portion 29 having a rectangular cross section is provided on the side end 26 side at the four corners of the upper polishing table 9a, and this guided portion 29 is connected to the guide column 10 of the lower polishing table 9b.
and is guided by sliding. The grip portion 11 is provided on the longitudinal centerline of the lower polishing table 9a. The storage hole 12 is provided on both sides thereof, and the cladding tube 15 is put in and taken out along the guide groove 27 open to the side end 26 side, so the grip part 11 does not get in the way when the cladding tube 15 is put in and taken out.

The lower polishing table 9b is shown in FIGS. 3A and 3B. The main body 30 of the lower polishing table 9b is the upper polishing table 9
Like a, it is made of an insulator such as hard vinyl chloride. This main body 30 is provided with a pipe connection part 31, and the pipe connection part 31 is formed with a female thread 32 for screwing the pipe 5a. A flow path branches from the piping connection portion 31 to the communication path 19, and the opening 20
A cathode 21 made of platinum or the like is provided.
Guide columns 10 having an L-shaped cross section are provided at the four corners of the lower polishing table 9b.

Next, the operation of this embodiment will be explained.

The grip portion 11 of the upper polishing table 9a is gripped by a manipulator, lifted from the lower polishing table 9b, and moved to the outside of the electrolytic cell 2. On the other hand, the switching valve 8b is switched to the opposite side from the state shown in FIG. 1 to supply the electrolytic solution from the external tank 4 to the electrolytic cell 2, and the electrolytic solution in the electrolytic cell 2 is heated to about 60° C. by the heater 2. .

The cladding tube 15 from which the fuel has been separated by cutting and melting is gripped by a manipulator, and the tube holder 14 is held along the guide groove 27 of the upper polishing table 9a.
into the storage hole 12. At this time, the anode 16 comes into contact with the cladding tube 15 across the outer surface thereof.

The guided portion 28 of the upper polishing table 9a containing the cladding tube 15 is slidably guided to the guide column 10 of the lower polishing table 9b and set on the lower polishing table 9b. At this time, the lower polishing table 9 is placed at the center of the cladding tube 15.
The cathode 21 provided at b is located.

In this invention, by simply storing the cladding tube 15 in the upper polishing table 9a, the anode 16 comes into contact with the cladding tube 15.
On the other hand, simply by setting the upper polishing table 9a to the lower polishing table 9b, the cathode 21 is located at the center of the cladding tube 15, so remote control using a manipulator is easy.
and reliable. Particularly in this embodiment, efficiency is significantly improved because a plurality of cladding tubes 15 are simultaneously positioned and electrodes are attached.

The switching valves 8a and 8b are set to the state shown in FIG. 1, the pump 6 is operated, and the electrolyte is circulated between the pump 6 and the electrolytic cell 2 via the pipes 5a and 5b. Then, a direct current of 30 A/dm ² is supplied from the power source 20 to electrolytically polish the inner surface of the cladding tube.

The electrolyte is discharged upward through the inside of the cladding tube 15 via the communication passage 19 of the lower polishing table 9b. This eliminates the accumulation of air bubbles and anolyte, and prevents uneven polishing and formation of grooves.

After electropolishing, the switching valve 8a is switched to the opposite side from the state shown in FIG. 1, and the electrolyte is returned to the external tank 4. be measured.

The invention is not limited to the embodiments described above. For example, the object of electrolytic polishing is not limited to cladding tubes that constitute fuel assemblies of nuclear reactors, but any other type of tube may be used.

(Effects of the Invention) In this invention, when the tube is stored in the upper polishing table, the anode comes into contact with the tube, and when the upper polishing table with the tube placed thereon is set in the lower polishing table, the cathode is located inside the tube. Therefore, since there is no need to pass the cathode through the center of the tube for positioning or to attach the anode to the tube, remote control using a manipulator can be performed easily and reliably.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic diagram of an embodiment of the present invention. Figures 2A and 2B show the upper polishing table 9a according to this embodiment, of which Figure 2A is a plan view and Figure 2B is a front view. 3A and 3B show the lower polishing table 9b according to this embodiment, of which A is a plan view and FIG. 3B is a front view. 2: Electrolytic bath, 9: Polishing table, 9a: Upper polishing table,
9b: lower polishing table, 14: tube holding section, 15: cladding tube, 16: anode, 21: cathode.

Claims (1)

[Scope of Claims] 1. An interior of the tube in which the inner surface of the tube is electrolytically polished in an electrolytic solution, with the tube serving as one pole and the other pole disposed inside the tube, and the tube being held on a polishing stand. A method for setting a tube in a surface electrolytic polishing apparatus includes an upper polishing table and a lower polishing table, the upper polishing table is provided with a tube holding part, and the tube holding part contacts the tube while holding the tube. A polishing table is used in which the one pole is provided on the upper polishing table and the other pole located inside the tube is provided on the lower polishing table, and the 1. A method of setting a tube in an apparatus for electrolytic polishing of an inner surface of a tube, characterized in that an electrode is located inside the tube by holding the tube and then setting the upper polishing table on the lower polishing table. 2. In an electrolytic polishing device for the inner surface of a tube, in which the inner surface of the tube is electrolytically polished in an electrolytic solution with a tube as one pole and the other pole placed inside the tube, the polishing table has an upper polishing table and a lower polishing table. a polishing table, the upper polishing table is provided with a tube holding part, and the upper polishing table is provided with the one pole that contacts the tube while holding the tube in the tube holding part, and the tube is held in the tube holding part. In an apparatus for electropolishing a tube inner surface, the other pole located inside the tube is provided on the lower polishing table when the upper polishing table is set on the lower polishing table. Set device.