GB2089272A

GB2089272A - Storage support for spent fuel elements from nuclear power stations

Info

Publication number: GB2089272A
Application number: GB8039814A
Authority: GB
Original assignee: NOELL G G GmbH
Current assignee: NOELL G G GmbH
Priority date: 1980-12-12
Filing date: 1980-12-12
Publication date: 1982-06-23
Also published as: FR2496960B1; FR2496960A1; GB2089272B

Abstract

A storage support for spent fuel elements from nuclear power stations, comprises a plurality of tubes having a square or rectangular cross-section and which are provided with one or more compartments to receive the fuel elements, characterised by the feature that each tube (2) has at least three horizontal bolts (6), the central axes (a) of which bolts intersect at a point (M), and a base plate is secured on the floor of the storage vessel associated with the bolts (6), the side walls (8) of the base plate have an inclined recess (9) which is upwardly enlarged to a V-shape or substantially to a V-shape, whereby in the lowered position of rest of the tube (2), the central axis through the recess registers with the central axis (a) through the bolt (6). <IMAGE>

Description

SPECIFICATION Storage support for spent fuel elements from nuclear power stations The present invention relates to a storage support or frame for spent fuel elements from nuclear power stations, comprising a plurality of tubes which have a square or rectangular cross-section and which have one or more compartments to receive the fuel elements.

German Offenlegungsschrift 27 30 850 discloses a storage frame in which the individual tubes are provided on the lower end with a threaded pin having a recess which is supported on a spherical dome secured to the base of the storage vessel. In order with the occurrence of horizontal shock forces, as in earthquakes, to absorb the tipping moment acting on the individual tubes, the base plates of the adjacent tubes are combined into a unit, the storage frame. In this manner there is formed a large rigid plate composed of the individual base plates, so that the acceleration forces produced by the horizontal vibrations are unable to liftthestorageframeoffthe spherical domes. Such a structure of a storage frame necessitates that the connection of the individual tubes occurs before or after insertion in the storage frame.With prior connection, storage frames are provided which are no longer transportable, so that smaller units are produced which after lowering into the storage vessel are connected therein. With the height of the storage vessel, however, this is very difficult since with inadequate screw connection at this point, buckling-out occurs with horizontal vibrations.

It is an object of the invention in storage supports or frames of the kind referred to above, to secure each individual tube against horizontal shocks, whereby the securing or locking provided in the storage vessel occurs exclusively by the weight of the tube with the lowering thereof, and unlocking occurs automatically during the raising and drawingout of the tube.

According to the present invention there is provided a storage support for spent fuel elements from nuclear power stations, comprising a plurality of tubes having a square or rectangular cross-section and which are provided with one or more compartments to receive the fuel elements, characterised by the feature that each tube has at least three horizontal bolts, the central axes of which bolts intersect at a point and a base plate is secured on the floor of the storage vessel associated with the bolts, the side walls of the base plate have an inclined recess which is upwardly enlarged to a V-shape or substantially to a V-shape whereby in the lowered position of rest of the tube, the central axis through the recess registers with the central axis through the bolt.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which Figure 1 is a horizontal section in plan through a storage support or frame with externally located base plates; Figure 2 is a section on the line II - II of Figure 1; Figure 3 is a section corresponding to Figure 1 of an alternative embodiment of a storage frame having an internally located base plate.

A bearing support or storage frame 1 is formed by a tube 2 having a square or rectangular cross-section and adapted to receive a plurality of fuel elements by division into a corresponding plurality of compartments 3 - as shown in Figure 1. In a simpler arrangement (not shown) the support is formed by a tube of square or rectangular cross-section and adapted to receive a single spent fuel element. The cross-section of the compartments 3 is adapted to the external dimensions of the fuel elements.

The storage frame 1 may be used for the intermediate storage of fuel elements which on removal from the nuclear reactor still require a decay phase before being sent to a preparation or reprocessing plant. Besides, the frame itself is also suitable for use in the reprocessing plant to store fuel elements delivered until they are further processed.

The tube 2 is covered at the lower end by a plate 4 which has openings 5 formed therein to the compartments 3 to allow cooling water to reach the fuel element in the given chamber 3. Below the plate 4 there are secured at least three and as shown in Figure 1 there are four bolts 6, the central axes a of which intersect substantially at a point M, whereby the end faces of all bolts 6 are equidistantly spaced from point M. In order to absorb tipping moments with the occurrence of horizontal shocks, it is desirable to provide an as large a base as possible and to this end the bolts 6 in the embodiments are located diagonally in the region of the corners of the tube 2.

On the floor of the storage vessel, as shown in Figure 1, square base plates 7 corresponding to the number of tubes to be received and having upwardly projecting side walls 8 are secured, whereby the side wails 8 in plan view form a square or rectangle.

Preferably, the axial extension of the central axis a is the centre-line which bisects the side walls. Each side wall 8 has an inclined and upwardly open recess 9 which is flared upwardly in substantial V-shape, whereby the V-surface 10 and 11 act as guides for the bolts 6. Thus, the diameter of the recess 9 corresponds to the cross-section of the bolts 6 to be received so as to obtain an unrestrained inlet and clearance free mounting of the bolts 6 in the recess 9.

The tube 2 is lowered, in known manner, by a block and tackle into storage vessel. On lowering each bolt 6, due to the weight of the tube 2, drops via the V-shaped surfaces 10 or 11 into the associated recess 9 of the side walls 8 and at the same time executes a rotary movement and is retained therein against being lifted vertically out by the projection 12 formed by the V-surface 10. The side walls 8 may thus be drawn evenly inwardly or in accordance with the supporting circle around point M. Both the transmission of the vertical forces from the weight of the tube 2 and the transmission of the acceleration forces from horizontal shocks or vibrations to the base plates occur via the bolts 6 on the base plate 7.

As evident from Figure 1, each tube 2 has four base plates 7 associated therewith, whereby each base plate is adapted to locking four tubes 2.

In Figure 3 a circular base plate for receiving a tube 2 is provided which simultaneously forms the abutment for transmitting the vertical forces from the tube 2 against the floor of the storage vessel. The circular side wall 8 registers with the supporting plate around the point M and has a recess 9 of the kind described above. The bolts herein only transmit the acceleration forces.

Claims

1. A storage support for spent fuel elements from nuclear power stations, comprises a plurality of tubes having a square or rectangular cross-section and which are provided with one or more compartments to receive the fuel elements, characterised by the feature that each tube has at least three horizontal bolts, the central axes of which bolts intersect at a point, and a base plate is secured on the floor of the storage vessel associated with the bolts, the side walls of the base plate have an inclined recess which is upwardly enlarged to a V-shape or substantially to a V-shape, whereby in the lowered position of rest of the tube, the central axis through the recess registers with the central axis through the bolt.

2. A storage support as claimed in claim 1, in which the recess is enlarged upwardly into a Vshape and the V-surfaces form the guide for the bolts.

3. A storage support as claimed in claims 1 and 2, in which the diameter of the recess corresponds to the diameter of the bolt.

4. A storage support as claimed in claim 1, in which the tube is covered at the lower end by a plate which supports the bolts and is provided with the openings leading to the compartments in the tube.

5. A storage support as claimed in claims 1 to 4, in which the end faces of the bolts of a tube are equidistant from said point.

6. A storage support as claimed in claim 5, in which the bolts are located diagonally in the regions of the corners of the tube.

7. A storage support as claimed in claim 2, in which a projection is formed by the V-shaped surface and the upper wall of the recess which projection covers the bolt at least up to the vertical centre plane when the bolt is mounted in the recess.

8. A storage support as claimed in claim 1, in which the side walls in plan form a square or rectangle on the base plate and are so secured to the base of the storage support that the central bisecting line forms the axial extension.

9. A storage support as claimed in claim 1, in which each tube has four base plates associated therewith and the supporting and securing of the tubes on the base plates is effected exclusively via the bolts.

10. A storage support as claimed in claim 1, in which each tube has an annular base plate associated therewith, the circular side wall registering with the supporting circle and said point being provided with recesses corresponding in number with the bolts provided.

11. A storage support as claimed in claim 10, in which the tube is supported exclusively by the plate on the base plate.

12. A storage support substantially as herein described with reference to and as illustrated in the accompanying drawings.