FI115570B - Arrangements for holding nuclear fuel rods or sticks in an assembly - Google Patents

Description

115570 Arrangements for Holding Nuclear Fuel Rods or Rods in Combination - Arrangemang för att hälla kärnbränslestavar eller surface i ett aggregat 5

The present invention relates to arrangements for holding nuclear fuel rods or rods in combination. Such an arrangement may form part of a "top nozzle" for this combination.

Such rods or rods are generally held together in a core forming assembly of a nuclear reactor. The fuel itself is usually placed inside the outer casing of each rod or stick. In use, the fuel rods or rods 15 become hot and expandable and the coolant flows over them, generally in an upward flow. Known as the top nozzle, the arrangement is attached to this assembly at its upper end to hold the fuel rods or sticks in place, particularly during use. The upper nozzle 20 also directs the coolant flow out of the assembly, provides suitable features for handling the assembly, and provides a positioning site for the protective tube generally positioned around the assembly.

In accordance with the present invention, there is provided an arrangement for holding nuclear fuel rods or rods in a composite system comprising a plurality of fuel rods or rods: ···. , the retaining plate which is placed on the plate receiving portions of these targeting rods, which is. : 3-0 equipped with holes for the coolant to flow through, and a locking ring set to lock this plate to the alignment rods with a simple twisting motion.

The targeting rods may comprise tubular rods, which in practice contain coolant / retardant fluid such as water flowing through them.

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Each plate receiving section may suitably be provided with a thickening or top having a plug-shaped end portion.

5 The plate may include a plurality of holes, each of which fits on the free end of the corresponding stopper of the corresponding alignment rod, this plate leaning against the shoulder at the end of each plug.

10 The disc may form part of a reconstituted upper nozzle structure.

The locking ring may include a plurality of holes which include an alignment area for loosely aligning the holes for attaching the thickening to the plugs of the alignment rods. Each alignment rod may include an annular recess in its thickening to facilitate such attachment, with the hole attachment area narrower than the alignment area.

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The plate may include a recess receiving the locking ring, wherein the surface of the plate may be approximately flush with the locking ring placed in its recess.

:.: 25 The locking ring may advantageously be provided with a hollow center in a region that may have a plurality of bent portions of the locking::: to form the lugs, with the locking ring · · · · inserted in the disc recess and secured to locking the disc on the targeting rods, these locking lugs extend to the periphery of the hollow region. The disc may include points for attaching these lugs.

The locking ring may include an annular structure, with a plurality of holes formed in the inner part of the tire body and said bent parts extending inwardly from the inner edge of the tire body.

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The retaining plate may include a series of finger-shaped coolant flow openings, the length of which increases as it extends toward the outer edge of the plate. These openings may extend approximately parallel to the outer edge adjacent the plate.

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The board can be attached to other components which together form a so-called "sheet metal". "An upper nozzle". For example, attachment may occur adjacent to the outer edge of the disc. The other nozzle components may be removable from, or fixed to, the plate, for example by welding. The nozzle is completely removable from the rest of the fuel combination by the arrangement of the present invention.

The arrangement of the present invention permits simple and rapid locking and removal of the plate and nozzle components attached thereto when required. For example, if after a certain period of operation it is necessary during the routine shutdown of the reactor to replace one or more fuel rods or rods of the assembly due to malfunction 20, this rod or rod or rods may be removed by rapidly removing the plate and nozzle.

The fuel combination may be formed within this arrangement:,: 2: 5 with external sides of the cross section: '. · Hexagonal, for example WER-::' · reactors used in Eastern Europe. Said plate may have a hexagonal shape corresponding to the shape of the combination. The fuel rods or sticks may be set, for example, in a series of hexagonal spacers in accordance with our pending UK Patent Application No. 9303452.3, the contents of which are incorporated herein by reference. The hexagonal protective tube can cover the combination at the ends of the rods or pins adjacent to the plate.

JS

We have found that six pointing sticks can be used:. instead of the fuel rods or sticks, in such a combination of 4 115570, preferably placed in radial positions at mid-points of the center axis of the combination and at the outer edges of the plate at the six corners of the plate. By using the rods set in this way, as the water passes through them, the hi-5 dast / fuel ratio is increased, but unexpectedly, the same overall cycle energy of the reactor is achieved as with a conventional combination of fuel rods replacing the targeting rods. This results in more efficient fuel recovery without the disadvantages of enrichment, thereby reducing the fuel requirement of each reactor by about 5%, as well as the cost of producing, storing, handling and operating the fuel.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a partial lateral cross-sectional view of the nozzle plate and locking arrangement (taken along line I-I20 of Figure 2);

Figure 2 is a partial top cross-sectional view taken along line II-II taken from the nozzle plate and locking arrangement of Figure 1.

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As shown in the figures, they are intended for the VVER reactor. the combination of the nuclear fuel rods 1 is placed ..... in a hexagonal series inside the hexagonal protective tube 3.

The six alignment rods 5 are placed within the series of fuel rods. 30 The alignment rods 5 are positioned in place of the fuel rods about the middle of the set center to six corners. Each alignment rod 5 comprises a tubular structure having a water inlet. and outlet openings (not shown) to allow water to flow therethrough upstream during use Each alignment rod 5 includes a shoulder 7 and a plug-shaped head 9. An annular slot 11 is formed at the plug end 9.

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A retaining and flow plate 13 is disposed on the plug ends 9 of the six aligning rods 5 against the shoulder 7 of each rod 5. The plate 13 includes a series of elongated holes 15 / extending therethrough in the direction of adjacent hexagonal sides. The upper nozzle 17 is welded to the plate 13 via weld seams 19. The plate 13 is locked to the guide rods 5 by means of a locking ring 21. The locking ring 21 fits into the recess 22 on the upper surface of the plate 13, whereby the upper surface of the ring 21 is flush with the upper surface of the plate 13. The Ren-10 gas 21 includes six holes 25 comprising a portion 25a and a narrower portion 25b.

In use, the ring 21 is disposed loosely at the parts 25a on the stopper ends 9 of the guide rods 5. The 15 ring 21 is then rotated anticlockwise (as shown) until the narrow portion 25b of each hole 25 is secured to the slot 11 by its rod 5. protruding inwardly into the recess 22a from the ring 21 from positions adjacent the narrow portions 25b, leaning against the upper surface of the plate 13 at the recess 22a, thereby assisting in retaining the plate 13 by the locking ring 21.

In use, the coolant flows upwardly through the combination of Figure 1 and passes through plate 13 through holes: 25. Plate 13 firmly holds the rods in place in their combination.

..... The plate 13 and the upper nozzle 17 attached thereto, which together form a single solid structure, can thus be permanently attached to the rods 5 by aligning and rotating the alignment ring in a simple manner. Similarly, once the fuel rods 1 have been used and after the reactor has been placed in its enclosure, it is necessary to remove and replace with a new single rod 1, plate 13 and top, 35 nozzle 17 can be quickly removed by simple quick action as compared to the mounting of the plate # »* 115570 s 13 and the upper nozzle 17), which allows access to the upper end of that rod 1.

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Claims (11)

7 115570 P roductions An arrangement for retaining nuclear fuel rods or pins in a combination comprising a plurality of alignment rods disposed within the fuel rods or pins, each containing a plate receiving portion, a retaining plate inserted into the plate receiving portions of these alignment rods with a cooled stream of holes. through it, and the locking ring, characterized in that the locking ring 10 is set to lock the plate to the guide rods in a single rotation operation. Arrangement according to Claim 1, characterized in that the targeting rods are tubular rods. 15 Arrangement according to Claim 1 or 2, characterized in that each plate receiving part comprises a thickening or an end having a plug-shaped end part. Arrangement according to Claim 3, characterized in that said plate comprises a plurality of holes, each of which fits on the free plug end of the thickening rod of the corresponding alignment rod, the plate leaning against the shoulder at the end of each plug. • »·! . ·. 25 • i · • · t Device according to any one of the preceding claims, characterized in that the plate forms part of a reconstitutable upper nozzle assembly. • f · • · · Device according to any one of claims 3 to 4, characterized in that the locking ring includes a plurality of holes, which include a focus area for movable alignment. : for the plugs of the alignment rods, with these holes ··· [area to be attached to the alignment rod. Apparatus according to claim 6, characterized in that each alignment rod includes an annular recess to facilitate the attachment of the locking ring holes to the alignment rod, the mounting area of these holes being narrower than the alignment area. Device according to any one of the preceding claims, characterized in that the plate is provided with a recess receiving the locking ring, the surface of this plate being approximately flush with the surface of the locking ring placed in the plate recess. Device according to Claim 8, characterized in that the locking ring comprises a hollow region and a plurality of bent portions comprising locking lugs, when the locking ring is disposed in the disc recess and secured to lock the disc on the alignment bars, these locking lugs extend over the periphery of the hollow area. on the existing disk. Apparatus according to any one of the preceding claims, characterized in that the retaining plate comprises a series of finger-shaped coolant flow openings, the length of which increases as it extends towards the outer edge of the plate. Device according to Claim 1, characterized in that it is substantially in accordance with the accompanying drawings. * ·. ·. 25 • »* · *« ·