JP2005139478A - Plating method to wrapper tube for fuel assembly, and plating electrolytic cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plating method to a wrapper tube for a fuel assembly where hard chromium plating with a fixed thickness can be effectively applied to a spacer pad part with a compact plating electrolytic cell without dipping the whole of the wrapper tube into the plating electrolytic cell, and the subsequent treatment can be facilitated without causing the sticking of an electrolytic solution to the part of the wrapper tube other than the spacer pad part, and to provide a plating electrolytic cell. <P>SOLUTION: In the method, at least one surface part 5S in the spacer pad part 5 of a wrapper tube is covered with a plating electrolytic cell 10, electric current is made to flow between the wrapper tube as the cathode and the anode 16 fixed to the inside of the plating electrolytic cell 10, hard chromium plating is applied to the surface part 5S in the spacer pad part 5 contacted with the plating electrolytic cell 10, and the operation is performed at the other surface part 5S in the spacer pad part 5, thus the hard chromium plating is applied to the whole surface of the spacer pad part 5 in the wrapper tube. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an improved method for plating a spacer pad portion of a trumpet tube of a fast reactor fuel assembly and a plating electrolyzer suitable for use in this improved method.

  As shown in FIG. 3, the fast reactor fuel assembly 1 is composed of a bunch of fuel pins 3 housed in a regular hexagonal trumpet tube 2, and each fuel pin 3 is formed by oxidation of plutonium and uranium. Pellets formed by sintering the mixture are filled and sealed with helium gas. The fuel assembly 1 has an entrance nozzle 4 at the lower part thereof, and the focusing body of the fuel pin 3 has neutron shields at the upper and lower parts thereof. The fuel pins 3 in the trumpet 2 have a dense equilateral triangular lattice arrangement in order to increase the power density of the core and improve the breeding performance. The fuel pins 3 are fixed only at the lower end portion, and the adjacent fuel pins 3 are kept apart from each other by wire spacers wound around each fuel pin. Such a fuel assembly is practically used because it has a simple structure and can respond relatively flexibly to changes in the dimensions of the fuel pin under irradiation of neutrons.

  Further, the trumpet pipe 2 has several spacer pad portions 5 provided at intervals in the vertical direction in order to maintain the interval between the adjacent fuel assemblies 1, and these spacer pad portions 5 are resistant to wear. In order to improve the property, hard chrome plating is applied to the surface.

  In the prior art, in order to perform hard chrome plating on the spacer pad portion 5, masking is performed on the surface of the trumpet tube portion excluding the spacer pad portion 5, and then the entire trumpet tube is immersed in a plating electrolytic cell. A steel plate was placed around, energized using a trumpet tube as a cathode and a steel plate as an anode, and hard chrome plating was applied to the spacer pad portion.

However, this prior art method has the following drawbacks.
・ The trumpet tube has a length of about 2000 mm. In order to immerse the entire long trumpet tube in the plating electrolyzer, a large electrolyzer is required, and therefore the plating work is performed only in the factory. As a result, it was necessary to transport the trumpet tube to the plating factory or to the site after plating.
・ If the entire trumpet tube is immersed in the plating electrolyzer, the plating electrolyte tends to penetrate into the mask layer and the plating electrolyte tends to adhere to the trumpet tube other than the spacer pad. It takes a lot of labor, and in particular, when an electrolyte solution adheres to the inner surface of the trumpet tube, it is very difficult to remove it, and there is a possibility that the masking adhesive remains on the inner surface of the trumpet tube.
・ Since the steel plate that serves as the anode is manually placed around the spacer pad in the plating electrolytic cell, the positional accuracy between the surface of the spacer pad and the anode depends on the skill level of the operator, so it is always specified. It was difficult to obtain a hard chrome plating layer having a thickness of.
・ Normally, six faces of a regular hexagonal trumpet pipe are plated by a single construction operation, but the spacer pad part is about 600 mm away from the end of the trumpet pipe, so it can be inserted through the end opening of the trumpet pipe. Since the thickness measuring instrument does not reach the spacer pad portion, measurement cannot be performed, and there is no measuring instrument that directly measures the thickness of the plating layer at such a deep position. For this reason, the outer dimensions of the hard chrome plating layer are measured between the hexagonal faces of the trumpet tube, and the pre-plating dimension between the hexagonal faces of the trumpet pipe is subtracted from this measured value. The thickness of the hard chrome plating layer on each side of the hexagonal surface is measured from the half value of the difference, but this measurement is the average value of the plating layer on the opposite surface, so it is the actual value. The measurement accuracy is inferior.

    Do not immerse the entire trumpet tube in the plating electrolytic cell, apply the chromic acid solution partially to the surface of the spacer pad, bring the anode of the carbon rod close to this surface portion, and use the trumpet tube as the cathode to supply chromium between them. A method of wearing is proposed.

  However, the chromium layer formed by this method has the disadvantages that the hardness is inferior to that of the plating treatment, so that the wear resistance is low, the workability is inferior, and the practicality is low.

  One problem to be solved by the present invention is that a hard chromium plating can be effectively applied to the spacer pad portion in a small plating electrolytic bath without immersing the entire trumpet tube in the plating electrolytic bath. It is an object of the present invention to provide a method for plating a fuel assembly trumpet tube that can facilitate subsequent processing without attaching an electrolyte solution to a trumpet tube portion other than the portion.

  Another problem to be solved by the present invention is to provide a plating method for a fuel assembly trumpet tube that can be applied with a hard chromium plating layer having a predetermined thickness with a constant anode position with respect to a spacer pad portion. It is in.

  Still another problem to be solved by the present invention is to provide a plating electrolytic cell suitable for use in a method for plating a trumpet tube that solves the above problems.

  According to one aspect of the present invention, there is provided a plating method for a trumpet tube in which a hard chrome plating layer is applied to a spacer pad portion of a trumpet tube that houses a focusing body of fuel pins, and at least one surface portion of the trumpet tube spacer pad portion. Is covered with a plating electrolyzer, and the surface of the spacer pad portion that contacts the plating electrolyzer is plated. Then, the other surface portion of the spacer pad portion is covered with the plating electrolyzer and the spacer pad portion of the trumpet tube is sequentially plated. It is another object of the present invention to provide a method for plating a fuel assembly trumpet tube.

  In the above problem-solving means of the present invention, it is preferable that the anode is arranged in the plating electrolytic cell with a predetermined distance from the surface portion of the spacer pad portion to be plated. Further, these surface portions can be covered in one plating electrolytic cell over a plurality of partial surfaces of the spacer pad portion of the trumpet tube, and the plurality of surface portions of the spacer pad portion can be plated simultaneously under the same conditions. Furthermore, a plurality of surface portions of the spacer pad portion of the trumpet tube are respectively covered with a plurality of plating electrolyzers, and the plurality of surface portions of the spacer pad portion are simultaneously plated by operating these plurality of electrolyzers simultaneously. Can be applied.

  Another problem-solving means of the present invention is a plating electrolytic cell used in the plating method for a fuel assembly trumpet tube according to the above-mentioned problem-solving means, wherein the surface of the trumpet tube spacer pad portion to be plated is liquid-tight. It is intended to provide a plating electrolytic cell characterized in that it comprises a plating tank body having a seal to be contacted while maintaining an opening, and an anode fixed in the plating tank body.

  According to the present invention, at least one surface portion of the spacer pad portion of the trumpet tube is covered with the plating electrolytic bath, the surface portion of the spacer pad portion contacting the plating electrolytic bath is plated, and this operation is performed on the spacer pad portion. Since the spacer pad portion of the trumpet tube is plated by performing on the other surface portion, the spacer pad portion can be hard chrome plated in a small plating electrolyzer without immersing the entire trumpet tube in the electrolyzer. Therefore, it is not necessary to transport the trumpet pipe to the plating factory, and the transportation cost of the trumpet pipe can be reduced and the delivery time can be shortened.

  In addition, when the plating electrolytic bath is downsized, the amount of plating electrolyte used can be reduced to the minimum necessary, and the waste of plating solution can be eliminated. Circulation makes it easy to manage the concentration and temperature of the plating electrolyte.

  Since the hard chrome plating is not formed without masking except for the portion covered with the plating electrolytic bath, the masking operation, its removal, and the cleaning operation become unnecessary, and the workability is improved.

  Since the anode is fixed at a fixed position in the plating electrolytic cell, there is no instability of the electrode position or shape, and there is no influence on the skill level of the operator, and there is always no variation in the predetermined thickness. A layer can be formed.

  Since the chromium plating layer is formed on a part of the surface of the spacer pad portion on the polygonal wrapper tube, the thickness of the hard chromium plating layer can be measured accurately and easily. More specifically, since there is a plating layer on one opposite surface of the spacer pad portion of the polygonal wrapper tube and there is no plating layer on the other surface, the outer diameter dimension including the plating layer on these opposite surfaces is small. By subtracting the outer diameter dimension of the opposite surface before plating from the measurement value, the thickness of only the plating layer is measured, and this measurement value is not the average value of the plating layer of the opposite surface as in the prior art, Since it is an actual measurement value of the plating layer applied to the surface portion, accurate measurement can be performed.

  By covering these surface portions across a plurality of surface portions of the spacer pad portion with one plating electrolytic cell, or by setting a plurality of small plating electrolytic cells on the plurality of surface portions, the spacer pad portion A plurality of surface portions can be plated at the same time, and a reduction in workability due to split plating can be suppressed as much as possible.

  The plating electrolytic cell is composed of a plating tank main body having a seal to be contacted while keeping liquid-tightness on the surface to be plated of the spacer pad portion of the trumpet tube, and an anode fixed in the plating tank main body. Therefore, the plating operation can be performed simply by pressing the plating electrolytic cell against the surface of the spacer pad portion, and high-quality plating can be performed without requiring the skill of the operator.

  An embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a state in which a method for plating a fuel assembly trumpet tube according to the present invention is performed. A small plating electrolytic cell 10 applied to the surface portion of the spacer pad portion 5 of the trumpet tube 1 is used.

  The plating electrolytic cell 10 includes a plating electrolytic cell main body 14 in which a seal 12 to be brought into contact with the surface portion 5S to be plated of the spacer pad portion 5 of the trumpet tube 1 is fixed to the opening surface 14a. It consists of an anode 16 fixed in the plating electrolytic cell main body 14. The seal 12 is made of rubber or elastic plastic and is attached along the entire circumference of the opening surface 14 a of the plating electrolytic cell main body 14. The plating electrolytic cell 10 presses the seal 12 so as to be in close contact with the spacer pad portion 5. Set.

  In the illustrated embodiment, the size of the opening surrounded by the opening surface 14a of the plating electrolytic cell main body 14 is one surface portion of each spacer pad portion 5 that is hexagonal corresponding to the regular hexagonal trumpet tube 1 ( It is possible to cover each one surface portion of the spacer pad portion 5 as the same area as one of the six surface portions forming the hexagonal column). The spacer pad portion 5 may have a size and shape so as to cover two or three adjacent surface portions (see FIG. 2). Conversely, the plating electrolytic cell main body 14 may have an area smaller than the area of each surface portion of each spacer pad portion 5.

  The plating layer main body 14 has a plating electrolyte inlet 18 and a plating electrolyte outlet 20, and the plating electrolyte 22 enters from the inlet 18 and comes into contact with the surface portion 5S of the spacer pad portion 5 to perform the plating process. Is discharged from the outlet 20.

  The anode 16 is composed of a metal plate 16M such as a steel plate fixed to the wall surface 14b opposite to the opening surface 14a of the plating tank body 14 by an appropriate means. The metal plate 16M is a spacer pad portion 5 of the trumpet tube 1. It has an area substantially corresponding to the surface portion 5S to be plated. As described above, when the anode 16 is fixed at a predetermined position in the plating tank body 14, the plating process can be started immediately by simply pressing the plating electrolytic cell 10 to the spacer pad portion 5 and fixing the plating electrolytic cell 10. Since the distance D between the pad portion 5 and the anode 16 is constant, the thickness of the chromium plating layer does not vary.

  A method for performing chromium plating on the spacer pad portion 5 of the trumpet tube 1 using the above-described plating electrolyzer 10 will be described. The seal of the plating electrolyzer 10 is applied to the predetermined surface portion 5S of the spacer pad portion 5 of the trumpet tube 1. 12 is pressed to cover the surface portion 5S surrounded by the seal 12 with the plating electrolytic cell 10. The plating electrolytic cell 10 is fixed to the trumpet tube 1 by an appropriate means (not shown).

  The plating electrolytic solution 22 is supplied from the electrolytic solution inlet 18 into the plating electrolytic bath 10 and led out from the outlet 20 to be circulated. This is to facilitate the management of the concentration and temperature of the plating electrolytic solution. is there. In this state, when the trumpet tube 1 is used as a cathode and current is passed between the anode 16 and the anode 16, a hard chrome plating layer is formed only on the surface portion 5S of the spacer pad portion 5 in contact with the plating electrolyte solution 22.

  After forming the hard chrome plating layer on the surface portion 5S of the spacer pad portion 5 in this way, the plating electrolytic cell 10 is then applied to the other surface portion 5S of the spacer pad portion 5, and the other surface is subjected to the same operation. A hard chrome plating layer is formed on the portion 5S, and thereafter, the same operation is repeated to apply the hard chrome plating layer to all the surface portions 5S of the spacer pad portion 5.

  As already described, since the anode 16 is fixed in advance in the plating electrolytic cell main body 14, the anode steel plate or the like is disposed around the spacer pad portion 5 of the trumpet tube as in the conventional dipping method. Since the distance D between the anode 16 and the surface portion 5S of the spacer pad portion 5 to be plated is constant, there is no variation in the thickness of the plating layer, and the thickness is constant. The plating layer can be obtained.

  Furthermore, the plating electrolyte does not leak to the portion other than the surface portion 5S to be plated of the spacer pad portion 5 by the seal 12, and the masking operation of the trumpet tube, its removal, and the cleaning operation are unnecessary.

  The thickness of the hard chrome plating layer formed on the spacer pad portion 5 can be easily measured from the difference between the facing distance of the trumpet tube before and after the hard chrome plating layer and the facing distance before plating.

  In the embodiment of FIG. 1, the plating electrolytic bath 10 is assigned to each surface portion 5S of the hexagonal spacer pad portion 5 corresponding to the hexagonal column of the trumpet tube 1. By applying the tank 10 to the different surface portions 5S of the spacer pad portion 5 and operating the plurality of plating electrolytic tanks 10 simultaneously, the plating operation can be performed more efficiently.

  Further, as shown in FIG. 2A or FIG. 2B, the plating electrolytic cell 10 covers two or three adjacent surface portions 5S1, 5S2, or 5S1 to 5S3 of the spacer pad portion 5 so as to cover them. The plurality of surface portions 5S can be plated simultaneously with various dimensions and shapes.

  The plating method of the fuel assembly wrapper tube of the present invention can efficiently form a high-quality chrome plating layer without using a large plating electrolyzer, and manufactures a fast reactor fuel assembly wrapper tube. It can be used preferably.

It is sectional drawing which shows a part of the state which is implementing the plating method of the trumpet pipe for fuel assemblies by one form of this invention. 1 shows a plating method for a fuel assembly trumpet tube according to a different embodiment of the present invention. FIG. 1A is a schematic cross-sectional view showing a state in which two adjacent surface portions of a spacer pad portion are plated at a time. (B) is a schematic cross-sectional view of a state in which three adjacent surface portions of the spacer pad portion are plated at a time. It is a perspective view which fractures | ruptures and shows a part of fuel assembly.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel assembly 2 Trumpet pipe 3 Fuel pin 4 Entrance nozzle 5 Spacer pad part 5S, 5S1, 5S2, 5S3 Surface part 10 Plating electrolytic cell 12 Seal 14 Plating electrolytic cell main body 14a Opening 14b Wall opposite to the opening 16 Anode 16M steel sheet

Claims (5)

In a plating method of a trumpet tube, in which a hard chrome plating layer is applied to a spacer pad portion of a polygonal trumpet tube that houses a focusing body of fuel pins, at least one surface portion of the spacer pad portion of the trumpet tube is covered with a plating electrolytic cell, Plating is performed on the surface portion of the spacer pad portion that contacts the plating electrolytic bath, and then the other surface portion of the spacer pad portion is covered with the plating electrolytic bath, and the spacer pad portion of the trumpet tube is sequentially plated. A method for plating a trumpet tube for a fuel assembly. 2. The method of plating a fuel assembly trumpet tube according to claim 1, wherein an anode is disposed in the plating electrolyzer with a predetermined distance from a surface portion of the spacer pad portion to be plated. A method of plating a trumpet tube for a fuel assembly characterized by the above. 2. The method of plating a fuel assembly trumpet tube according to claim 1, wherein the surface of the spacer pad portion of the trumpet tube is covered with a single plating electrolytic cell over a plurality of partial surfaces. A method of plating a trumpet tube for a fuel assembly, wherein a plurality of surface portions of the part are plated simultaneously under the same conditions. 4. The method of plating a fuel assembly trumpet tube according to claim 1, wherein a plurality of surface portions of spacer pad portions of the trumpet tube are respectively covered with a plurality of corresponding plating electrolyzers, A plating method for a fuel assembly trumpet tube, wherein a plurality of surface portions of the spacer pad portion are simultaneously plated by simultaneously operating the plating electrolytic cell. 5. A plating electrolytic cell used in the plating method for a fuel assembly trumpet tube according to claim 1, wherein the surface of the trumpet tube spacer pad portion to be plated is kept in liquid-tight contact. A plating electrolytic cell comprising: a plating tank main body having a seal to be opened on an opening surface; and an anode fixed in the plating tank main body.