DE1197302B - Device for electrolytic pickling and electroplating of cylindrical metal objects, especially uranium rods - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C23b

German class: 48 a-5/68

Number: 1197 302

File number: E 22238 VI b / 48 a

Filing date: January 12, 1962

Opening day: July 22, 1965

The invention relates to a device for electrolytic pickling and electroplating of cylindrical Metal objects, in particular uranium rods for fuel elements of nuclear reactors.

It is known that in nuclear reactors with natural uranium, the fuel rods to protect the uranium from the corrosive effects of the flowable coolant are enclosed in aluminum shells. It is also known that, even at relatively low temperatures (200 ^° C.), a phenomenon of very rapid diffusion of uranium into the aluminum shell is observed with the formation of compounds which, due to their brittleness, are easily corroded by the fluid coolant circulating in the reactor and can be destroyed.

In order to remedy this deficiency, attempts have been made to prevent the diffusion phenomenon from occurring prevent the task of diffusion protection between the uranium rod and the aluminum shell filling thin layer of metal, an alloy or an oxide.

The essential material of an effective diffusion protection must besides a certain number of quite precise properties (good thermal conductivity, between the expansion coefficient of uranium and the expansion coefficient of aluminum, lower effective neutron absorption cross-section, the ability to diffuse uranium in aluminum even at lower temperatures and vice versa) have the property that I apply it to the uranium rod in this way allows the coating obtained to adhere very strongly, not to be brittle, but to be massive and constant everywhere Thickness has.

Investigations on diffusion protection layers have already been carried out in various countries and methods of applying thin metal coatings by electroplating have been found elaborated on a uranium surface. However, the precipitates obtained by these known methods are not entirely satisfactory because they do not adhere sufficiently strongly to the uranium, are too porous and are too brittle and have a thickness that is not constant at all points.

In fact, the galvanic application of deposits on uranium still causes considerable difficulties due to the peculiarity of this element (orthorhombic crystal structure, high oxidizability). In addition, the quality of the precipitation depends on the properties of the bath used, from the device for pickling the uranium device for electrolytic pickling and electroplating of cylindrical metal objects,
especially of uranium rods

Applicant:

European Atomic Energy Community (Euratom),

Brussels

Representative:

Dipl.-Ing. R. Müller-Borner

and Dipl.-Ing. H.-H. Wey, patent attorneys,

Berlin 33, Podbielskiallee 68

Named as inventor:

Francesco Brossa, Poirino, Turin (Italy);

Denis Tytgat, Mol (Belgium)

Claimed priority:

Italy of January 14, 1961 (52/489)

area and ultimately depends on whether the different Place the surface of the uranium rod in the bath more during the electrolytic treatment or less evenly exposed.

It is already a process for the electrolytic pickling of a uranium surface and for Subsequent coating of this area has been proposed, with the coated area after it has been pickled according to this process to absorb adhesive and massive galvanic deposits different metals is suitable. However, the uranium surface obtained in this way is very active, due to oxide easily attackable and therefore quite sensitive.

The disadvantages shown are avoided according to the invention by a bath container edge horizontally mounted axis that can be set in oscillating rotary motion, on which two semi-cylindrical sheet metal electrodes with their open side axially against each other via cross members and two mutually inclined, the metal objects

509 627/256

carrying circular, electrically insulated carriers approximately coaxially over a radius exceeding the radii of the cylindrical sheet metal electrodes a frame rigidly connected to the axle are attached, and by parallel guides for prevention a displacement of the metal objects in the axial direction, which via a central part, which is a flexible metal band for making electrical contact with the metal body on its underside, connected are. In this way, the metal objects are forced to roll on a carrier in such a way that that their positions in relation to the electrodes are constantly changing and those for achieving a uniform one Corrosion and a uniform coating of their surfaces created optimal conditions will.

This enables the electrolytic pickling of cylindrical metal objects in various baths and the transport of the pickled object into the electroplating bath by means of a simple operation when executed faster. Contact with the metal objects is also prevented and the resulting in the range of high activity and high oxidizability of the pickled Area-resulting disadvantages are avoided.

The invention is described below for an exemplary embodiment with reference to the drawings. It shows

F i g. Figure 1 is a perspective view of an embodiment of the mounted on a plating trough Device according to the invention,

F i g. 2 shows a vertical section along the line I-I in Fig. 1 and

F i g. 3 a vertical section along the line II-II in FIG. 2.

The device consists essentially of two semi-cylindrical sheet metal electrodes 3 and 4, which are rigidly connected to the axilla of the cylinder by means of two crossbars 2 and 2 '. The two sheet-metal electrodes 3 and 4, which are made of perforated sheet metal to facilitate degassing during electrolytic pickling and electroplating, generally have different diameters from one another. One electrode is used for pickling and the other for electroplating. A frame 5 is rigidly connected to the axis 1, to which two ring-shaped, mutually inclined, polyethylene-coated metal supports 6 and 6 'are attached. The cylindrical object 7 to be exposed to the pickling and electroplating process rests on these carriers.

The ends of the axilla lie in suitable depressions provided on the edge of the trough 8. One of the ends is connected to a drive device (not shown) via a crank device 9. This drive device gives the entire device an oscillating movement, through which the cylindrical object? forced to do so will alternately roll in one direction or the other. It also changes this movement steadily the support point of the object on the mutually inclined carriers 6 and 6 'as well as the the surface portion facing the electrodes.

Such an oscillating movement does not change the anode-cathode distance. The possible movements of the cylindrical object 7 in directions transverse to the circular, to each other inclined supports 6 and 6 'are prevented by a device placed on the floor.

This device contains two rectilinear, parallel to the supports 6 and 6 'and through a Central part 11 held separately from one another guides 10 and 10 'made of polyethylene. In the middle of this Spacer, parallel to the guides 10 and 10 ', a flexible part 12 is arranged, the one with the cylindrical object? at its lower section, i.e. at one point that it does not interfere with the electrolysis, is in contact.

The flexibility of the contact part is chosen so that any risk of abrasion for the cylindrical Item 7 is prevented.

The pickling electrode (cathode) consists of nickel or stainless steel sheet. It is interchangeable and has a diameter that is larger, the smaller the cylindrical object to be pickled or the higher the electrical resistance of the pickling bath. The electrode (anode) for electroplating is made up of from the material to be applied or, for example, in the case of a chrome plating process an inert metal like lead. In general, the diameter of the anodes is in the interest of The homogeneity of the deposit is less than that of the cathode.

The operations required to coat a cylindrical Objects, such as a uranium rod, to be carried out with the device according to the invention are as follows: Object in the area of the drum intended for pickling, between the guides and on the circular, The carrier, which is inclined to one another, dips the whole thing into the acidic liquid Tub and carries out the pickling process. Then you lift the drum out of the pickling trough and submerges the entire facility for washing the rod in water. Then you turn the drum by 180 ° around its own axis, so that the rod is in the section of the drum intended for the coating transforms. Finally, the drum is placed in the electroplating trough.

Claims (4)

Patent claims: 1. Device for electrolytic pickling and electroplating of cylindrical metal objects, in particular uranium rods for fuel elements of nuclear reactors, characterized by one that is mounted horizontally on a bath tank rim and can be set in an oscillating rotary motion Axis (1), on which two semi-cylindrical sheet metal electrodes (3,4) with their open side against each other axially via cross members (2, 2 ') and two mutually inclined, the metal objects (7) receiving circular, electrically insulated support with one of the radii of the cylindrical sheet metal electrodes crossed approximately coaxially over a rigid with the frame (5) connected to the axis are attached and by parallel guides (10, 10 ') to prevent a displacement of the metal objects (7) in the axial direction over a central part (11), which is a flexible metal strip (12) for making electrical contact with the metal body its underside is connected. 2. Apparatus according to claim 1, characterized by semi-cylindrical sheet metal electrodes (3, 4) made of perforated sheet metal and unequal radii. 5 3. Device according to claim 1 and 2, characterized by electrolyte inert metal for electroplating by a sheet metal electrode from process. Nickel or stainless steel for the pickling 4. Apparatus according to claim 1 to 3, ge process and a second sheet metal electrode from denotes by against those of other radii the one to be applied or one that can be exchanged for the S. 1 sheet of drawings 509 627/256 7.65 © Bundesdruckerei Berlin