GB2194964A - Process for the production of cooling or cooled elements which are subjected to high thermal loading - Google Patents

Abstract

A cooling or cooled element designed to take high thermal loads is produced using a support 1. Cooling tubes are inserted into grooves 2, 3, 4, 5; their ends are sealed into grooves or bores in side parts which fit in recessed regions 6, 7. Copper is electrodeposited over the surface of the support and cooling tubes. It is then machined to a flat surface. Bores 8, 9 contain bolts (19, 20; Figs. 4-6) which become attached to the copper plate (25) formed. These bolts (19, 20) can be pushed upwards to remove the copper plate (25) from the support. The plate may then be turned over and a further layer (28) deposited on the other side. The element is finished off by connecting the cooling tubes to collecting ducts and machining through- passages into the plate. The procedure may be used to make accelerating grids for neutral particle injection in fusion reactors. <IMAGE>

Description

SPECIFICATION Process for the production of cooling or cooled elements which are subjected to high thermal loading The invention relates to a process for the production of cooling or cooled elements which are subjected to high thermal loading and especially but not exclusively accelerating grids which are to be provided with through-passages and which are intended for neutral parti cle injection in fusion reactors. In this process a plurality of spaced-apart cooling ducts are formed in the element by means of at least one material layer applied by electroplating, and the plate so formed is then surface treated.

In the fusion technology field there is a need for actively cooled structures, which in use are subjected to high thermal loading, in the form of grid plates provided with a plurality of through-passages. This applies especially to the injection of neutral particles in fusion reactors, wherein high-energy particles (H+ ions) are produced in an ion source. To accelerate them, these particles are sent through a set of grids, comprising three individual grids namely a plasma grid, accelerating grid, and an earth grid, which are situated at a specific spacing parallel to one another and are secured to grid support elements. The grids are transversely divided with grid halves angled slightly relatively to one another, and have in one specific arrangement a pattern of through-passages through which the ions are accelerated and focussed on a common focal point.

To avoid having the grid plates deformed by the thermal loading, there are arranged in them, between the through-passages, cooling ducts which extend at right angles thereto and through which water flows to dissipate heat.

To avoid local temperature increases, the grid plates are made from material which is a good conductor of heat, preferably high-purity copper. In order on the one hand to keep the plate temperature in the operating state as low as possible, and on the other hand to keep the heating of the water at an inconsiderable level, a sufficient quantity of water must flow through the grid plates. Since the cooling ducts have only small dimensions and thus large pressure losses, the water must be forced through the grid plates with an appropriately high flow pressure. Correspondingly high standards are set as regards the sealingtightness and the strength of the cooling ducts.

Accelerating grids have hitherto almost exclusively been made in accordance with the so-called electroforming method, at least in Europe. In that method, the cooling ducts are first cut into one side of a base plate. Then the cooling ducts are filled with electrically conductive wax. Then an adequately thick covering layer is applied by electrodeposition, so that a copper plate is produced which is smooth at both sides and has cooling ducts arranged therein. Then the wax is removed by heating. During the electrodeposition operation, which is fairly slow-about 0.3 mm increase in thickness per day-tests and heating operations are carried out. After the final test the finished grid plate is produced from the grid blank by appropriate mechanical processing.

Since the bonding surface for the electrodeposited material layer between the through passage holes and the cooling ducts is very small and is frequently less than 1 mm, the electroforming operation needs great care to prevent leakage points occurring. The surfaces to be electrocoppered must be completely free from wax, since otherwise bonding errors may occur. The wax also has to be completely removed from the cooling ducts after the electrodeposition operation. Checks for any wax residues remaining also require considerable outlay. Finally, care has to be taken to prevent cavities or capillaries from forming which could lead to leakages.

It is true that the aforesaid problems can be overcome with careful procedure. But this involves considerable outlay in the production process.

Therefore, the invention has as its object to find a process for the production of cooling elements subjected to high thermal loading which is noteworthy for relatively low production outlay and greater manufacturing consistency.

According the invention process for the production of cooling or cooled elements which are subjected to high thermal loading, preferably accelerating grids which are to be provided with through-passages and which are intended for neutral particle injection in fusion reactors, in which process a plurality of spaced-apart cooling ducts are provided in the said element, which has at least one material layer applied by electroplating, and the surface of the plate is then treated, characterised in that small cooling tubes are used for fqrming the cooling ducts and are laid on a support, and that a plate element is formed by the electrodeposition of at least one material layer on the free surface of cooling tubes and support.

In the invention the plate element-apart from the previously laid cooling tubes and, where appropriate, side parts-is produced completely by electrodeposition. This has the advantage that no leakage points at all occur in the critical region of the through-passages.

The small cooling tubes enclosed by the electrodeposited material can be already tested for sealing-tightness beforehand, so that leaks can no longer occur. Capillaries and relatively small cavities can be tolerated in the electrodeposited material, since they, because the cooling ducts have been arranged as cooling tubes, cannot cause any sealing problems.

Correspondingly, intermediate checks and tests can be dispensed with, which reduces the outlay in the electrodeposition work. If relatively large cavities are found after the conclusion of the electrodeposition operation, these can be repaired in a simple manner. The time-consuming milling of the cooling ducts is also no longer needed, likewise the use of conductive wax with the great care which that required, so that the process in general can be carried out in a simpler way and less expensively, even taking into account the fact that the outlay for the electrodeposition itself is higher.

In one embodiment of the invention it is proposed that, after separation from the support, the plate element is provided on the other side also with at least one layer of material applied by electrodeposition. In this way the cooling tubes are completely embedded in the material of the plate element and surrounded thereby. This also dispenses with the need to use high-purity copper for the cooling tubes. It is sufficient to use for this purpose normal copper or other corrosion-resistant alloys compatible with high-purity copper.

So that the cooling tubes retain their position before and during electrodeposition, they are preferably inserted in grooves formed in the support. It is advantageous to do this in such a manner that they project partly, preferably half way, above the surface of the support, so that after the first electrodeposition step the cooling tubes still project partially at the underside of the electrodeposited material.

This portion of the cooling tubes may then be enveloped in any second electrodeposition step.

After the application of the material layer/layers, it is advantageous to carry out surface treatment of the plate element at one side before it is separated from the support. It can be fixed to the support for this purpose.

A particularly advantageous method consists of inserting pins in holes formed in the support, upstanding as far as the surface of the support, before the first material layer is applied by electrodeposition. By this arrangement the pins are bonded to or even into the material layer by the electrodeposition and thus hold the plate element during the subsequent surface treatment. A particularly good grip is achieved if the pins are connected by a screwed connection, at their lower side, to the support.

As a further step, it is possible, before the electrodeposition, to place side parts against the two ends of the cooling tubes. The end regions of the cooling tubes are advantageously inserted in grooves or bores in the side parts. The support can have appropriate recesses for this purpose. In this way the electrodeposited layer becomes intimately connected with the side parts, and a stable cohesive plate element is produced which has good sealing between the cooling tubes and the side parts. It is possible to solder the cooling tubes to the side parts before the electrodeposition, whereby sealing-tightness between cooling tubes and side parts is always guaranteed.

Ducts (which may be termed manifolds) may also be formed in the side parts after the electrodeposition, so as to establish communication with the cooling tubes but it is also possible to form these ducts beforehand, and then to fill them with wax, which is then removed by heating after the electrodeposition has been carried out.

Since, especially when using the grid plate as an accelerating grid, the through-passages have to be produced with great precision, it is recommendè'd that they be hollowed out only after electrodeposition has been carried out, most preferably by drilling. It is also possible to form the through-passages by means of short tubular elements which are completely closed, i.e. closed at both ends. These may be placed on the support before electrodeposition, and then opened or taken out at the final processing stage. This makes it possible not to have to drill the through-passages-when greater precision is not required.

The invention is shown in more detail with reference to constructional examples in the drawings. In these: Figure 1 shows an oblique view of a support for carrying out the process according to the invention; Figure 2 shows a fragmentary sectional view through the support shown in Fig. 1 with side part and cooling tubes inserted; Figure 3 shows a fragmentary sectional view through the support shown in Fig. 1 with another side part and cooling tubes inserted; Figure 4 shows a cross-section through the support shown in Fig. 1 taken along the line A-A; Figure 5 shows a cross-section through the support shown in Fig. 4 after the first electrodeposition step; Figure 6 shows a cross-section through the support shown in Fig. 5 after the first surface treatment; Figure 7 shows a cross-section through the grid plate element shown in Fig. 6 after its removal from the support; ; Figure 8 shows the grid plate element shown in Fig. 7 in a turned-over position and after the second electrodeposition step; and Figure 9 shows the grid plate element after the final processing.

A support 1 shown in Fig. 1 is constructed as a solid body and is made from an acrylic plastic, in particular, polymethyl methacrylate.

Special steel, steel or other suitable materials may also be used if their surface is so treated that copper electrodeposited thereon does not adhere.

The support 1 comprises a total of four straight grooves 2, 3, 4, 5 and a step-shaped shoulder 6, 7 formed at either end of the grooves. In the region of the central axis two bores 8, 9 are provided which extend through to the underside of the support 1.

As shown in Fig. 4 in the first step in forming a grid plate element, small cooling tubes 11, 12, 13, 14 made of copper are placed in the grooves 2, 3, 4, 5. The height of the rectangular-section cooling tubes 11, 12, 13, 14 is adapted to the depth of the grooves 2, 3, 4, 5 so that the cooling tubes 11, 12, 13, 14 project with half their height above the surface of the support 1. This may also be seen in Figs. 2 and 3, which illustrate the lefthand end region of the support 1 with the step-shaped shoulder 6 and the cooling tube 11. On each step-shaped shoulder there rests a side part 15, 16 of solid material, normally of solid copper material or other suitable material such as e.g. special steel, copper alloys or the like.The side part 15 shown in Fig. 2 extends only as far as the surface of the support 1 and comprises, in its top surface, grooves 17 each of which constitutes a prolongation of the grooves 2, 3, 4, 5 and into which the projecting ends of the cooling tubes 11, 12, 13, 14 project. In Fig. 3 the side part 16 is made higher, and comprises bores 18 as a continuation of the grooves, 2, 3, 4, 5 into which the ends of the cooling tubes 11, 12, 13, 14 project. In both instances, the cooling tubes 11, 12, 13, 14 are closed at the ends by soldering to prevent the entry of electrolyte.

As may be seen in Fig. 4, bolts 19, 20 having their upper ends step-shaped widened portions 21, 22 are inserted in the bores 8, 9. The bolts 19, 20 are locked into the support 1 by nuts 23, 24 screwed-on from below.

The arrangement shown in Fig. 4 is then introduced into a galvanising bath. As a result-as shown in Fig. 5-there is formed, on the surface of the support 1 and on the projecting surfaces of the cooling tubes 11, 12, 13, 14, a material layer 25 which consists of maximum-purity copper for use as an accelerating grid. The material layer becomes intimately bonded with the projecting part of the cooling tubes 11, 12, 13, 14 and also with the tops of the bolts 19, 20, whereas there is no adhesion to the material of the support 1.

The somewhat uneven surface of the material layer 25 is then mechanically treated to produce a plane surface. At this time the material layer 25 is held securely by the bolts 19, 20. The result is to be seen in Fig. 6.

The nuts 23, 24 are then unscrewed, so that the grid plate element 26 can be iifted off from the surface of the support 1, comprising material layer 25, cooling tubes 11, 12, 13, 14 and side parts 15 (not visible), 27. The bolts 19, 20 are removed to provide a grid plate element 26 as shown in Fig. 7.

This grid plate element 26 is then turned through 1800 about the central axis extending parallel to the cooling tubes 11, 12, 1,3, 14.

The parts of the cooling tubes 11, 12, 13, 14 which at first projected downwards from the material layer 25 are thus made to project upwards from the said layer. The grid plate element 26 is then placed again on a support, securely screwed to the support, and introduced a second time into an electrodeposition bath. A further layer of material 28 is then formed by electrodeposition on the upper surface-as shown in Fig. 8. This layer covers the parts of the copper tubes 11, 12, 13, 14 which until then had been still projecting, in a manner corresponding to Fig. 5. The cooling tubes 11, 12, 13, 14 are now completely embedded in the two material layers 25, 28, and these material layers 25, 28, of course, merge into one another and do not have any parting plane between themselves.This similarly applies to the side parts 15, 27, especially at the entry point of the cooling tubes 11, 12, 13, 14 into the side parts 15, 27. Thus, a stable cohesive grid plate element 26 with good sealing of the cooling tubes 11, 12,. 13, 14 relatively to the side parts 16, 27 is provided. The electrodeposition is thus complete.

The grid plate element 26 is then mechanically treated. First the somewhat uneven surface of the material layer 28 is made plane.

Then adjacent the cooling tubes 11, 12, 13, 14 a plurality of through passage holes 29, 30, 31, 32 are drilled, so that a grid structure is obtained. This is shown in Fig. 9, wherein the grid plate element 26 has been turned again through 1800 relatively to the position shown in Fig. 8. Then ducts serving as manifolds are cut into the side parts 15, 27, so as to join up the ends of the cooling tubes 11, 12, 13, 14 which enter the side parts, these ends are simultaneously also finished off.

These ducts are then closed by covers which are soldered, welded, or electrodeposited into place.

The support 1 can be used for producing a large number of identical grid plate elements 26. When the grid plate element 26 is tohave different geometry a new support 1 has to be produced, then this new support can be used again any number of times for the production of identical grid plate elements.

Claims (14)

1. Process for the production of cooling or cooled elements which are subjected to high termal loading, preferably accelerating grids which are to be provided with through-passages and which are intended for neutral particle injection in fusion reactors, in which process a plurality of spaced-apart cooling ducts are provided in the said element, which has at least one material layer applied by electroplat ing, and the surface of the plate is then treated, characterised in that small cooling tubes are used for forming the cooling ducts and are laid on a support, and that a plate element is formed by the electrodeposition of at least one material layer on the free surface of cooling tubes and support.

2. Process according to claim 1, wherein the plate element is also provided on the other side with at least one electrodeposited material layer after separation from the support.

3. Process according to claim 1 or 2 wherein the cooling tubes are laid in grooves formed in the support.

4. Process according to claims 2 and 3, wherein the cooling tubes are laid in the grooves so that they project partly, preferably half way, above the surface of the support.

5. Process according to claims 1 to 4, wherein the plate element is subjected to a surface treatment after application of the material layer/layers on one side, but before it is separated from the support.

6. Process according to claim 5, wherein pins reaching at least as far as the surface of the support are inserted in holes formed in the support before the first material layer is applied.

7. Process according to any one of claims 1 to 6, wherein side parts are arranged on both ends of the cooling tubes before the electrodeposition operation.

8. Process according to claim 7, wherein the ends of the cooling tubes are inserted in grooves or bores in the side parts.

9. Process according to claim 7 or 8, wherein the cooling tubes are soldered to the side parts before the electrodeposition.

10. Process according to any one of claims 7 to 9, wherein ducts are formed in the side parts, so as to communicate with the cooling tubes.

11. Process according to any one of claims 1 to 10, wherein the through-passages are formed after the electrodeposition operation.

12. Process according to any one of claims 1 to 10 wherein for forming the through-passages, tubular elements closed at both ends are put on the support before the electrodeposition and opened or removed when the final processing is carried out.

13. Process substantially as described herein with reference to the drawings.

14. A cooling element produced according to the process of any one of claims 1 to 13.