FR2791171A1 - Fixing large rack structures in nuclear fuel ponds to flat surfaces, comprises use of anchors and connector assemblies with controlled rigidity characteristics, preventing excessive stresses in anchor or frame - Google Patents

Abstract

A connector (18) joins the base of the rack structure to each anchor (4). This exhibits (controlled) rigidity characteristics parallel to the support surface (3) and at right angles to it. It is adapted to the position of the anchor on the surface and the structure, to distribute stresses exerted between them in response to demands arising. Thus appearance of excessive stress at any point of the structure, or in one or more anchors, is avoided. An Independent claim is included for a method of rearrangement of a nuclear storage pond.

Description

The invention relates to a method and a device for fixing a

  large structure on a bearing surface and in particular

  of a support structure for racks for storing assembly of

  bustible resting on the bottom of a fuel storage pool of a nuclear power plant. Nuclear power plants and in particular nuclear power plants comprising a reactor cooled by pressurized water include, a fuel deactivation pool in which is stored under water assemblies of irradiated fuel taken out of the reactor core

  nuclear, for example when reloading the nuclear reactor core

  key and possibly the storage of new fuel assemblies used to replace used assemblies in the nuclear reactor core. Inside the deactivation pool or fuel storage pool, the fuel assemblies which generally have a straight prismatic shape and a square section, are arranged inside receiving cells, the walls of which are lined or formed. of neutron-absorbing materials. The fuel assemblies storage cells are grouped and assembled in the form of storage racks.

  storage in which the receiving cells of the assembly

  bustible are arranged in a network whose section is square or rec-

  tangular. Each of the fuel assembly storage racks may include, for example, 72 or 81 assembly receiving cells

of fuel.

  - Each of the fuel assembly storage racks has a base plate closing the lower part of the storage cells which rests on the bottom of the deactivation pool, when the storage rack is in its service position inside the swimming pool

deactivation.

  In some cases, it is necessary to provide anchoring means for fixing the base plates of the storage racks to the bottom of the pool. Such anchoring of the base plates of the storage racks is necessary in particular in the case where the nuclear power plant

  is built in an area where earthquakes can occur.

  The bottom of the fuel deactivation pool is general-

  consisting of a concrete slab coated with a stainless steel skin

  corn. The means for anchoring the storage racks consist of metallic elements, generally made of stainless steel, which are put in place to be partially embedded in the concrete of the bottom of the swimming pool.

  deactivation, during the construction of the fuel building. The ele-

  metal elements of the anchoring means may include for example

  a steel plate which is fixed in the concrete at the bottom of the dice pool

  activation in a position such that the upper surface of the plate is in the same plane as the surface of the slab constituting the bottom of the pool and a rod whose axis is perpendicular to the metal plate and which is engaged in an opening passing through the metal plate in the vicinity of its central part. The rod is placed so that its lower part below the metal plate is embedded in the concrete of the bottom of the pool and that it has an upper part projecting above the plate and the bottom of the pool which is usually threaded. The rod and the metal plate of the anchoring means are fixed one

  on the other by a circular weld. The stainless steel skin covers

  vrant the bottom of the pool has an opening at each of the anchoring means. We carry out a continuity of the metallic coating of the bottom of the swimming pool by ensuring the connection of the covering skin of the bottom

  of the swimming pool with the metal plates at the level of each of the

  vertices of crossing of an anchoring means.

  The anchoring means are therefore put in place definitively, at the time of construction of the deactivation pool and of the reactor building. The anchoring means are distributed over the surface of the bottom of the deactivation pool, so as to ensure good fixing of each of the fuel assembly storage racks and a homogeneous distribution of the forces that can be exerted between the storage racks. storage and anchoring means, in the event that the storage racks undergo

  external stress, for example during an earthquake.

  In some cases, it has been found desirable to modify the position or the distribution of the fuel assembly storage racks on the bottom of the deactivation pool, for example to increase the storage capacity of the deactivation pool. In the case of storage racks fixed by means of anchoring to the bottom of the fuel pool, such a modification of the position or of the distribution of the fuel assembly storage racks is generally not possible the fact that the position of the anchoring means cannot be changed and

  adapted to the new arrangement envisaged for storage racks.

  To solve this problem, in the context of the present invention, it has been imagined to have and fix on the bottom of the pool, by means of the anchoring means, one or more support frames of the

  storage racks made in the form of a truss made of beam-

  the metallic ones. The arrangement of the metal beams of the chassis must be carried out so that the storage racks can be fixed

  in the chosen arrangement, on the upper surface of the beams.

  A difficulty arises from the fact that the large structure

  consisting of the support frame (s) must be fixed to the bottom of the pool

  cine by means of anchoring means which have not been provided to ensure a good distribution of the forces which can be exerted between the structure

  large and anchoring means.

  Until now, no method has been known for ensuring the

  fixing a large structure on a sensitive support surface

  flatly such as the bottom of a swimming pool, using pre-existing anchoring means whose position and distribution have not been chosen to ensure a uniform distribution of the loads of the large structure. More generally, in the case of a large structure of any type, which must be fixed on a substantially flat bearing surface and which must withstand external stresses of various types, for example stresses due to efforts on the structure in service, to earthquakes, to the wind or to climatic variations, no process was known making it possible to carry out in a simple way, the fixing of the structure on the bearing surface, at the level of points

  anchor distributed along the bearing surface, so that the structure

  the anchoring means are not subjected to excessive stresses

  under the effect of stresses which can lead to deterioration of the structure

  ture. In particular, no method was known for ensuring an ideal attachment of such a structure in the case where the anchor points are pre-existing and have a distribution and positions which have not

  were planned according to the structure and in case the structure pre-

  feels parts of less resistance at certain points on its surface resting on the bearing surface. Depending on the nature of the external stresses exerted on the large structure, it may be necessary to take into account only forces exerted in directions

  parallel to the plane of the bearing surface or of the forces exerted perpendicularly

  cularily to this bearing surface or, more generally, ef-

  strong acting both parallel and perpendicular to the sur-

bearing face.

  The object of the invention is therefore to propose a method of fixing a large structure on a substantially flat bearing surface, by means of a plurality of anchoring means having a part projecting from to the support surface each arranged in an area of a plurality of areas distributed along the support surface, consisting of depositing the structure on the support surface and connecting it to each of the anchoring means, this method allowing to distribute the loads exerted

  on the large structure in the case where this structure is often

  stressing of various types, and in particular in the case where the anchoring means are pre-existing and are not distributed over the surface

  support in order to optimize the fixing of the large structure

  if we. '= For this purpose, the structure is connected to each of the anchoring means by a connecting means having stiffness characteristics in one at

  minus the directions parallel to the bearing surface and one direction per-

  pendulum to the bearing surface, adapted to the position of the anchoring means on the bearing surface and relative to the structure, for distributing forces

  acting between the bearing surface and the structure, under the effect of stress

  tions, so as to avoid the appearance of excessive stresses at any point of the large-scale structure, or in at least one of the

anchoring means.

  The invention also relates to a device for fixing a large structure making it possible to implement the method of the invention and comprising a plurality of connecting means each connecting

  a point of the structure to an anchoring means and comprising characteristics

  stiffness ticks adapted to the position of the anchoring means on the surface

  support and compared to the large structure.

  The invention also relates to a connection means the rigidity of which

  dity is suitable for its use for the connection of a large structure. Finally, the invention also relates to the application of the method and of the fixing device to the arrangement of a structure for storing fuel assemblies inside the deactivation pool.

of a nuclear power plant.

  In order to clearly understand the invention, a description will now be given, by way of nonlimiting examples, with reference to the attached figures,

  an embodiment of a structure for storing assembly assemblies

  bustible in a deactivation pool and connecting means of a

  support structure with anchors in the bottom of the deactivation pool

  tivation, according to several embodiments and variants.

  FIG. 1 is a plan view of a deactivation pool of a nuclear power station in which the storage capacity of fuel assemblies has been increased by using the method of the invention for fixing a support assembly for the storage racks storage of assemblies of

  fuel on the bottom of the pool.

  Figure 2 is a sectional view along 2-2 of Figure 1 showing

  fixing the storage racks to the support structure.

  Figure 3 is a top view corresponding enlarged scale

in detail 3 in FIG. 1.

  Figure 4 is a sectional view along 4-4 of Figure 3.

  FIG. 5 is a top view on a larger scale corresponding to

in detail 5 in Figure 1.

  Figure 6 is a sectional view along 6-6 of Figure 5.

  FIGS. 7A to 14A are views in vertical section of eight different embodiments of connection means according to the invention used for

  the distribution of forces exerted parallel to the bottom of the pool.

  Figures 7B to 14B are corresponding top views of

  each of the embodiments of the connecting means.

  Figure 15 and Figure 16 are top views of two varian-

  your realization of connecting means ensuring the distribution of efforts pa-

parallel to the pool plan.

  FIG. 17A is an exploded perspective view of an element in

  housing form of a connecting means according to a preferred embodiment

the invention.

  Figure 17B is a sectional view along B-B of Figure 17A.

  Figure 18 is an exploded perspective view of the connecting means

  of the preferred embodiment of the invention.

  Figures 19, 20, 21 and 22 are vertical section views of four

  three different embodiments of force limiting linkage means

  used in the context of the fixing method according to the invention.

  FIGS. 23A and 23B relate to another embodiment of a connection means for implementing the following connection method

  the invention using a bending bar.

  Figure 23A is a vertical sectional view and Figure 23B is a

top view of the connecting means.

  Figure 24A is an exploded perspective view of another embodiment

  creation of a connecting means for implementing the fixing method

  tion according to the invention using a torsion bar.

  FIG. 24B and FIG. 24C are views respectively in vertical section and from above of connecting means as shown in the figure

  24A associated in pairs at two anchoring means.

  Figure 25A is a vertical sectional view of another embodiment

  use of a connecting means for implementing the fixing method

  according to the invention using a beam in simple support.

  Figure 25B is a top view of connecting means as shown in Figure 25A.

  Figure 26 is a vertical sectional view of another embodiment.

  sation of a connecting means according to the invention using a built-in beam

  very. Figures 27 and 28 relate to two variants of another embodiment of connecting means for implementing the fixing method according to the invention using an S-flange.

  Figure 29A is a vertical sectional view of another embodiment

  reading of a connecting means for implementing the method according to

  the invention using a corrugated U-shaped flange.

  Figure 29B is a top view of the connecting means shown

in Figure 29A.

  Figure 30 is a vertical sectional view of another embodiment.

  sation of a connecting means for implementing the fixing method according to the invention using an O-shaped flange. In FIG. 1, the deactivation pool is seen in a plan view and in section through a horizontal plane. a designated nuclear power plant

  generally by the reference 1.

  The swimming pool 1 is of parallelepiped shape and delimited by pa-

vertical kings 2 and by a bottom 3.

  - The internal surfaces of the vertical walls 2 and the bottom surface 3

  are covered by a coating or skin in stainless steel

  ble which is fixed in contact with the concrete wall, by means of

  these metallic embedded in concrete.

  In FIG. 2 and in FIGS. 4 and 6, the skin 3a has been shown

covering the bottom 3 of the pool.

  Pool 1 has been designed to receive storage racks

  fuel assemblies that can be attached to the bottom 3 of the pis-

  cine, by means of anchoring means generally designated by the reference 4 (and generally represented by crosses) which are grouped in certain areas of the bottom of the pool, depending on the location

  planned fuel storage racks.

  As can be seen in FIG. 4 or in FIG. 6, the anchoring means 4 comprise a plate 5 fixed and embedded in the concrete at the bottom 3 of the swimming pool and a rod 6 whose axis 6 'is perpendicular to the surface of

  bottom 3 of the pool covered by the skin 3a, crossing the metal plate

  5 by a central opening of the plate 5 and embedded by its lower part

  rieure in the concrete of the bottom 3 of the swimming pool.

  The upper part 6a of the rod 6 is threaded to allow the screw-

  wise of fixing elements of storage racks on the bottom of the pis-

  cine. The skin 3a of the bottom 3 of the pool has an opening at the level

  each of the anchoring means 4 allowing the passage of the upper part

  of the fixing rod 6 of the anchoring means 4. The skin 3a is fixed,

  along the edge of the opening, on the metal plate 5, so as to

  sealing at all points of the concrete covering layer.

  The skin 3a for covering the bottom 3 of the swimming pool, the skin for

  covering of the vertical walls of the swimming pool as well as the elements

  titling the anchoring means 4 are made of stainless steel. Rods 6

  anchoring means 4 are made of stainless steel.

  The anchoring means 4, as can be seen in FIG. 1, consist

  either kill successive aligned rows arranged in the vicinity of the longitudinal edges of the swimming pool, each comprising five means

  anchor, or successive rows aligned in long directions

  longitudinal, in the central part of the swimming pool and comprising five pairs of

  anchoring means arranged in close positions.

  The problem facing the company filing this patent was to design a storage system allowing to significantly increase the storage capacity of the pool 1 while ensuring the fixing of the entire storage structure through pre-existing anchoring means 4, the position and distribution of which were provided for storage inside racks occupying only one

  part of the volume of the pool. As indicated above, it is not possible to

  ble to modify the position, the distribution or the number of anchoring means

  4 which were put in place and embedded in concrete at the time of construction.

swimming pool 1.

  To achieve compact storage of fuel assemblies,

  in a maximum volume of the fuel pool 1, the company deposits

  Health had the idea of designing a storage assembly comprising one or more support frames for the fuel assembly storage racks, resting on the bottom 3 of the fuel pool and fixed by

the anchoring means 4.

  Storage rack support assembly must be lowered

  in the bottom of the pool and set up very precisely in use

  sant lifting means, the depth of the pool being of the order of meters. It is therefore necessary to make the support frame in several parts which can be lowered independently of each other to

  inside the fuel pool, so as to limit the mass to

  to place. In fact, the support frames of the storage racks must pre-

  feel great rigidity and therefore a large mass, because they are intended to receive the storage racks which are filled with fuel assemblies in the pool. The storage racks are themselves fixed to the frames, so that the entire storage device is fixed relative to the bottom of the pool, by means

anchor 4.

  To cover the entire bottom 3 of the pool, five frames 7, 7a, 8, 9 and 10 were used which are placed in positions juxtaposed with

  inside the fuel pool.

  The rectangular frames 8, 9 and 10 have a long

  slightly less than the width of the pool and are juxtaposed next

  longitudinal sides parallel to the short sides of the pool.

  Chassis 7 and 7a which are placed successively in the direction

  of the width of the pool have a total length in this direction

  tion equal to the length of the chassis 8, 9 and 10.

  The production of the first frame line 7, 7a in two parts makes it easier to handle and place the frames in the pool. Each of the frames is produced, as can be seen in FIGS. 1, 2, 4 and 6 in particular, in the form of a trellis made up of beams 11 having I-shaped sections. In FIG. 1, so as to make the drawing more Clearly, only the outline of the chassis and the lattice structure have been shown in certain parts of the chassis only. Each of the beams consists of three stainless steel plates welded together, one of the plates placed vertically constituting the core of the beam and the

  two other plates the wings of the beam.

  The beams 11 constituting the support frames are arranged in two directions at 90 and assembled together by welding. Each of the chassis thus constitutes a monobloc mechanically welded assembly produced

  in the form of a wire mesh.

  Each of the chassis 7, 7a, 8, 9 and 10 is produced in such a way that the lines of anchoring means 4 are located, either directly above a space between

  two longitudinal direction beams, either on the edge of one of the frames.

  In the solution chosen by the applicant company, one of the anchor lines is arranged along a longitudinal end edge of the chassis

  7 and along the adjacent longitudinal end edge of the chassis 7a.

  All the other anchor lines are located between two transverse beams of one of the frames. The chassis must be fixed to the bottom of the pool at each of the anchoring means 4,

  so that the entire storage device can withstand stresses

  external tations such as those accompanying an earthquake.

  As can be seen in Figure 2, in the solution adopted by the so-

  depositing society, the storage racks such as the rack 12 shown in FIG. 2 are fixed on the upper horizontal surface of the frames, by means of plates 13 fixed by welding to the upper wing of a beam 11. The plate 13 and the upper wing of the beam 11 are crossed

  by a tapped opening having a vertical axis.

  The storage rack 12 has a base plate 14 which is

  fixed by screws such as 15 and 15 'to the upper surface of the plates 13.

  The storage rack 12 has vertical walls 16 containing

  mant a neutron-absorbing element which delimit cells in each of-

  which is arranged a fuel assembly 17 which rests by means of its lower end piece on a base bearing on the plate

  base 14 of the storage rack.

  As can be seen in FIG. 1, the storage racks 14 represented

  smelled in dashed lines which have a cross section and a substantially square base, mostly rest on two

  chassis juxtaposed across the width of the pool.

  All the racks of the storage device are therefore stably fixed on the upper part of the support assembly constituted by the juxtaposed lattice support frames. However, it is also necessary to secure the support frames to the means

  anchors fixed in the bottom of the pool.

  This fixing of the support frames must be carried out so as to

  from the forces exerted on the storage device, in the event that this

  positive storage is subject to stresses, for example in the case

  an earthquake. The efforts exerted at the various points of the structure of the

  positive storage and in particular at the points of connection of the structure with the anchoring means must be distributed so as to avoid any excessive stress which could lead to destruction or deterioration

part of the structure.

  - A finite element calculation on the whole structure showed

  that such a distribution of forces cannot be obtained by using ele-

  connecting elements of constant rigidity between the anchoring means and the

  points of the structure located at the level of the anchoring means.

  According to the invention, a method has been devised for fixing the support structure of the storage racks to the bottom of the pool, by means of connecting elements having variable rigidities and

  adapted according to the different anchoring points of the support structure.

  The invention also relates to a fastening device comprising at least one and generally a plurality of connecting means, each at

  an anchoring means, having an adapted rigidity.

  Two examples of connecting means with adapted rigidity have been shown.

  felt in Figures 3 and 4 on the one hand and 5 and 6 on the other. The connecting element 18 shown in Figures 3 and 4 is suitable for fixing a frame on an anchoring means 4 located between two beams

11 of the chassis.

  The connecting elements 19 and 19 'shown in Figure 5 are suitable for fixing the edge of a frame such as 7 or 7a on the bottom of the pool. Each of the connecting elements such as a connecting element 18 or a connecting element 19 or 19 'must have stiffness characteristics

  adapted to the chassis attachment point, as defined by the calculation.

  In the case of stresses accompanying an earthquake, the forces exerted on the support structure and on the entire storage device are horizontal forces, that is to say parallel to the plane of the pool and forces vertical, i.e. perpendicular to the bottom plane

  of the pool on which the support structure rests.

  We will now describe with reference to the figures appended in an-

  nexe, means of connection between the support frames and the means

  anchors which distribute the forces parallel to the plane of the pis-

  cine and possibly to distribute the forces exerted perpendicularly

  cularily at the bottom of the pool.

  These devices have rigidities adapted in two directions X and Y perpendicular to each other from a plane parallel to the bottom of the pool and

  possibly a rigidity controlled and adapted in a direction Z per-

pendulum to the pool plan.

  In FIGS. 7A to 14A and 7B to 14B, devices have been shown making it possible to distribute the forces exerted on the storage structure, in a plane parallel to the plane of the swimming pool, that is to say a horizontal plane. Of course, these devices can be combined with devices for controlling and distributing forces in the direction.

perpendicular

  circular to the plane of the swimming pool, that is to say in the vertical direction Z. The elements corresponding to all of FIGS. 7A to 14A and

  7B to 14B have the same references.

  Each of the connecting means generally designated by the reference 20 and ensuring the connection of a part of a support frame consisting of beams 11 with at least one anchoring means 4 fixed in the bottom of the pool comprises a plate 21 of generally rectangular shape which is fixed by welding, along at least one of its longitudinal sides on the base part of at least one beam of a support frame. Plate 21

  is pierced at its central part with an opening making it possible to engage through

  towards plate 21 the part projecting above the bottom of the pool of a

rod 6 of an anchoring means 4.

  In the case of the connecting means shown in FIGS. 7A to

  14A and 7B to 14B, the fixing by welding of the plates 21 of the connecting means

  sound 20 on the beams 11 of the chassis must be made before descending

  dre the chassis in the fuel pool. The support frame must be lowered into the pool, taking great precautions to simultaneously engage the openings of all the plates of the means of

  connection associated with the chassis, on the rods of the corresponding anchoring means

  dantes. It is of course necessary to provide a certain set of engagement of the rods 6, by machining a hole with a diameter greater than the diameter of the

* projecting part of the rod 6 through each of the plates 21. On the figures

  res 7A and 7B there is shown a first embodiment of a connecting means 20 in which the plate 21 is a simple plate pierced in its central part with an opening 22 for passage of the rod 6 of a means of anchoring. Each of the plates 21 of a connecting means 20 is fixed by weld beads 23, along its longitudinal sides, on the longitudinal sides of two wings constituting support bases of two beams

  11 parallel to each other of a support frame.

  The rigidity of the connecting means 20 is defined by the length a of the plate 21, the width b of the plate which is substantially equal to the spacing between the bases of two parallel beams of the chassis and the thickness e of the plate. In particular, the dimensions a and b make it possible to fix the rigidity of the plates 21 in the perpendicular X and Y directions

  between them and parallel to the bottom 3 of the pool.

  The plates 21 can be arranged one after the other in the longitudinal direction of the beams 11 of the chassis, as shown in FIG. 7B, so that the openings 22 are spaced apart

  a pitch corresponding to the spacing of the rods of the anchoring means

  affected in certain areas at the bottom of the pool

  The connection means shown in FIGS. 8A and 8B is overall-

  identical to the device shown in FIGS. 7A and 7B, the plate 21 of the device comprising in addition two through openings 24, aligned in a direction X of the plane parallel to the bottom of the pool constituting an axis of the plate 21 and arranged at equal distance on the part and

  other of the hole 22 for passage of the rod 6.

  In this way, the variables used to adjust the rigidity of the

  connecting means in the X and Y directions are formed by the long

  width a, width b and thickness e of the plate 21 and by the diameter Dx of the

holes 24.

  In the case of the device shown in FIGS. 9A and 9B, the plates

  that 21 are pierced with openings 25 on either side of the central opening

  trale 22 for passage of the rod 6, the openings 25 of diameter Dy allow

  both reduce and adjust the rigidity of the plates 21 of the devices 20

  in the direction Y parallel to the plane of the bottom of the pool.

  In the case of the connecting means 20 shown in Figures 1 OA and 10B, the plate 21 has lateral notches 26 on its sides

  longitudinal and the weld bead 23 of the plate occupies only one part

  tie of the length of the plate, on each of its longitudinal sides, on either side of the notch 26. It is thus possible to modify and adjust the rigidity of the connecting means in the direction Y. This rigidity can be adjusted by adjusting the length c of the notches 26 along which the plates 21 are not connected by the weld beads to the bases of the beams 11

of the support frame.

  The connection means 20 shown in FIGS. 11A and 11B are used to connect the support frames to anchoring means which are

  arranged in pairs, the rods of a pair of anchoring means having a

  Trax very substantially less than the distance between two anchor rods of two successive pairs of anchoring means. The plates 21 then have two passage openings 22 and

  22 'of the anchor rods between which there is a drilling 24 of a diameter

  meter Dx of plate 21 to adjust the rigidity of the double connecting means in the X direction. In this case, the variables used to adjust the stiffness of the connecting means 20 are the dimensions a, b and e (thickness) of the

  plate 21 and the diameter Dx of the hole 24.

  In the case of the connecting means 20 shown in FIGS. 11A and 11B, the hole 24 is in a centered position relative to the holes 22 and 22 '

  passage of the rods 6 while in the case of the connecting means 20

  presented in FIGS. 12A and 12B, the hole 24 'of diameter Dx is in

  an off-center position relative to the holes 22 and 22 'for passage of the rods.

  In this case, the parameters making it possible to determine the rigidities of the connection means consist of the dimensions of the plates 21, the diameters of the openings 24 'and, the distance f between the openings 24' and the openings 22 for passage of the rods thus that the distances c and d between the

  rod passage holes and the ends of the plate 21.

  In the case of the connection means shown in FIGS. 13A and 13B, the plate 21 of the connection means comprises lateral notches 26 and 26 ′ constituting discontinuities in the weld beads of the longitudinal edges of the plates on the beams 11 and an opening 24 ' in

  an off-center position with respect to the two openings 22 and 22 'for passage

  wise two rods of a pair of rods through the plate 21. In this case, the parameters for varying the rigidity of the connecting means are the parameters b, c, e, f, g and h shown in the figures 13A and 13B as well as

the diameter Dx of the openings 24 '.

  The connection means 20 shown in FIGS. 14A and 14B are intended to ensure the connection between the longitudinal edges facing the chassis 7a and 7 with a line of pair of anchoring means 4 disposed

  between the edges facing the chassis 7 and 7a.

  The connecting means 20 comprise a plate 21 fixed by weld beads 23 and 23 'separated from each other by a notch 26, along one of its edges, on a beam 11 of one of the frames 7 and 7a. The plates 21 have an inclined lateral edge, so that the plates 21 can be interposed, in a slot arrangement and

  placed successively with a small spacing in the longi-

  tudinal of the beams 11, while allowing attachment by weld beads 23 and 23 'of sufficient length. Each of the plates 21 of a connecting means 20 is crossed by an opening 22 for the passage of a

rod 6 of an anchoring means.

  The rigidity of the plates 21 is determined by the length of

  the notch 26 separating the two weld beads 23 and 23 '.

  In FIG. 15 and in FIG. 16, variants of the connection means have been shown, the plate of the connection means of substantially rectangular shape being replaced by a connection lug 27 of shape adapted to obtain the desired rigidity of the connection. In the case of FIG. 15, the lug 27 comprises two base parts which are fixed by welding to the lateral parts opposite the bases of two beams 11 of a support frame parallel to one another, by cords of separate weld one of

the other by a notch 28.

  The central part of the tab 27 of generally circular shape has a central opening 22 for passage of a rod of an anchoring means. The shape and dimensional characteristics of the legs as well as the length of the notches 28 make it possible to adjust the rigidity of the

means of connection.

  In the case of FIG. 16, the legs 27 ′ have only one base which is fixed on the longitudinal edge of a support base of a beam 11 of a support frame, in an end part of the chassis. The base has a notch 28 'on either side of which it is fixed by

beam welding 11.

  The plate 27 also includes an opening for the passage of a

  rod 6 of an anchoring means in an end portion of sensitive shape-

  circular. The connection means comprising lugs such as 27 ′ are used to ensure the connection of an end edge of a chassis such as 7 or 7a with the rods of the anchoring means aligned in a zone located

between chassis 7 and 7a.

  Of course, to make all of the anchoring means of a large structure such as a support frame or a set of frames of a fuel assembly storage device, it is possible to use to constitute the means of connection to the various anchor points, as a function of the required rigidities calculated from these connection means in the

  directions X and Y, connecting means of any type as shown

  felt in FIGS. 7A to 14A and 7B to 14B or also in FIGS. 15 and 16

  and, in general, at least one of these connecting means.

  These connection means ensuring a distribution of the forces in a plane parallel to the support plane of the structure, can be associated with force recovery means in a direction perpendicular to the support plane.

  According to a preferred embodiment, as shown in par-

  particular in Figures 3 and 4 and 5 and 6 which have been the subject of a description

  summary in an earlier part of this text, all the means of

  connection 18, 19 or 19 ′ of the support frames and anchoring means can be produced according to a single type making it possible both to distribute the forces in a plane parallel to the plane of the bottom 3 of the pool and in a

  vertical direction perpendicular to the bottom of the pool.

  Another advantage of the connection means according to the embodiment

  The preferred option is that these connecting means can be put in place to ensure the fixing of the support frames, after the removal of the support frames on the bottom of the pool, in their service position. In this case, the engagement of the connecting means on a rod 6 of an anchoring means 4 can be achieved much more easily than the simultaneous engagement on a plurality of anchoring rods of the openings of a plurality of means of

  link fixed on a support frame.

  In FIG. 18 as well as in FIGS. 17A and 17B, there is shown

  a connecting means 18 substantially similar to the connecting means shown

felt in figure 4.

  The connecting means 18 comprises in particular a body 30 called a housing which is shown in perspective and in cross section on the

Figures 17A and 17B.

  The housing 30 comprises a base plate 30a and a top plate

  parallel 30b parallel and connected to each other by four arms 31 perpendicular to

  res to the plates 30a and 30b arranged substantially along four faces of a parallelepiped. The base plate 30a is traversed by an opening 32 whose diameter is slightly greater than the diameter of the rod 6 of a

anchoring means 4.

  The upper plate is traversed by holes 33 for fixing the connection means on the base plates of the beams 11 parallel to each other of a support frame, by means of fixing screws or bolts 34, as it is visible on the Figure 18. The plates 30a and 30b are then

  parallel to the support surface 3.

  A nut 35 is screwed onto the threaded end portion projecting from the rod 6. The nut 35 when screwed onto the threaded end portion of the rod 6 tightens against the upper surface of the upper plate a of the housing 30, of elastic washers of the Belleville type 36. The nut 35 and the Belleville washers 36 make it possible to provide the connection between the anchoring rod 6 and the housing 30 secured to the beams 11 of the chassis by

screws 34.

  The rigidity of the connecting means 18 in horizontal X and Y directions

  zontales, perpendicular to each other and parallel to the bottom 3 of the pool

  can be adjusted by adjusting the dimensional characteristics of the branches

  ches 31 of the housing which are flexible connecting elements between the base a of the housing engaged on the rod 6 and the upper plate 30b of the housing

  fixed to the beams of the support frame.

  The flexibility of the branches 31 of the housing is determined by the dimensions

  sions of these branches 31, namely their length or height h, their thickness-

  sor e and their width 1, as can be seen in FIGS. 17A and 17B.

  The rigidity of the connecting means in the vertical direction Z perpendi-

  ring at the bottom 3 of the pool is regulated by the choice of the number and the

  characteristics of the Belleville washers 36 interposed between the nut 35 and the

  housing 30 and by tightening the nut 35.

  It is possible to use a plurality of relatively flexible Belleville washers or, on the contrary, a very small number or even a single washer of high rigidity, depending on the rigidity sought for the connection, in the direction Z. As indicated above, the connection means such as 18 (or 19 and 19 ′ as shown in FIGS. 5 and 6 in the case of fixing a support frame edge) can be put in place and fixed to the frames after the support frames have been placed in the bottom of the pool in

their service position.

  The establishment and installation of the connecting means 18, 19 and 19 'are

  carried out from the upper level of the switch-off pool

  bustible, using tools attached to the end of long poles

  cheerfully. For the establishment of a connecting means, the support housing 30 is lowered into the bottom of the pool and engaged, through its opening 32 on the rod 6 of an anchoring means 4. The housing 30 is oriented whereby

  its openings 33 are superimposed on threaded openings pre-

  views in the base parts of two beams facing the support frame on either side of the anchoring means 4. The housing 30 is fixed to the beams 11 of the support frame by screwing away from

  screws 34 in the threaded openings of the bases of the beams 11 vis-à-vis

  screws of the openings 33 of the upper plate of the housing. After fixing the box 30 on the support frame, we descend into the fuel pool, a nut 35 on which is fixed, by means of a thin sheet metal casing 35 'a stack of Belleville washers 36, then we screw the nut 35 on the threaded end of the rod 6, until the desired compression of the stack of Belleville washers 36 is obtained. The fixing of the support frame is ensured by successive installation of different connecting means the

  connecting to a set of anchoring means.

  The horizontal forces, in directions parallel to the bottom 3 of the pool are transmitted to the rod 6 of the anchoring means 4, via the housing 30 secured to the beams 11 of the support frame. The transmission

  horizontal forces is conditioned by the flexibility of the arms 31 of the box.

  tier, this flexibility being adjusted to obtain transmission and

  tition of adequate effort at each of the connecting means 18.

  The rigidity of the device in the vertical direction Z is defined by the characteristics of the Belleville washers and by the tightening of the nut 35.

  can thus adjust very precisely, both the rigidities in the di-

  horizontal rection only in the vertical direction of the connecting means of a

support frame.

  In the case of the connection means which have been described so far, we have

  on a transmission and distribution of forces parallel to the support plane of the structure, that is to say the horizontal forces, by means of elements having a rigidity (or flexibility) adapted to the position

of the connecting means.

  It is also possible to use connecting means having a role of limiting the force transmitted in a plane parallel to the support plane,

  that is to say connecting means comprising parts which can move

  cer relatively, when the forces transmitted by the structure exceed

feels a certain limit.

  Such a device is shown in FIG. 19. The device comprises an upper plate 36a which is welded by its lateral sides to two

  parallel beams 11 of the support frame and which is crossed by or-

  screw passage and through a central opening 38 of a diameter

  much greater than the diameter of the rod 6 of the anchoring means as well as a plate

  that lower 36b which is traversed by tapped screw engagement openings and which has a central opening with a diameter very slightly greater than the diameter of the rod 6 of the anchoring means. The connection means is fixed on the support frame, before the lowering

  chassis in the fuel pool. The screws 37 are engaged in or-

  vertices of the upper plate 36a and screwed into the tarau-

  dices of the lower plate 36b of the connecting means, until the screw head abuts on the upper plate 36a. The screws 37 are then

  tightened to the torque, so as to ensure contact with a pressure

  finished from the lower surface of the upper plate 36a and the over-

  upper face of the lower plate 36b of the connecting means, these surfaces

  these constituting sliding surfaces. The fixing of the connection means is completed by screwing a nut fitted with Belleville washers 36 on the threaded part of the rod 6, as

  in the case of the connecting means shown in FIG. 18.

  The through openings for the screws 37, of the upper plate 36a have a diameter much greater than the diameter of the screws and the lower plate 36b has external edges located at a certain

  distance from the lateral edges of the beams 11.

  When the support frame has been installed in the pool, in the event

  stress in a horizontal direction parallel to the bottom 3 of the piss

  cine, there is no displacement of the structure as long as the force exerted is less than a displacement force by sliding of the upper plate 36a on the lower plate 36b of the connecting means which are connected together by the screws 37 tightened to the couple. When the effort exceeds

  the sliding force of the plate 36a on the plate 36b, there is a

  ger displacement of the plates of the connecting means one on the other which ab-

  sorbs the energy communicated to the structure.

  In FIGS. 20 and 21 two variants of the connection means in FIG. 19 have been shown allowing a limitation of the force transmitted by the structure. - In Figure 20, the connecting means comprises, instead of a nut

  and a set of Belleville 36 washers, to ensure vertical rigidity

  wedge of the connecting means, a torsion bar 40 connected to a nut 35 screwed

  on the threaded end part of the rod 6, by a link arm 39.

  In the case of forces in the vertical direction perpendicular to the plane of the bottom of the swimming pool, the bar 40 is biased in torsion via the arm 39. Such a torsion bar device will be described more

in detail later.

  In the case of the variant shown in Figure 21, a bar

  bending 41 substantially parallel to the transverse fixed support surface 3 -

  ment between the two parallel beams 11 of the chassis comes to bear under the head of the nut 35 screwed onto the threaded end part of the anchor rod

6.

  In the event of stress in the vertical direction, the bar 41 undergoes a

  bending and ensures a certain absorption of vertical forces.

  The connection means shown in FIG. 22 which is substantially similar to the horizontal force limiting connection means shown in FIGS. 19, 20 and 21 comprises means for absorbing vertical forces with adjusted rigidity constituted by a nut 35 ' having a deformable part 35 ′ produced in the form of a tubular bellows part comprising several

successive waves.

  In Figures 23A and 23B, there is shown a connecting means 20

  comprising a plate 21 welded between two base parts of two

  trelles 11 resting on the bottom 3 of the swimming pool and comprising a central opening in which is engaged the projecting part of a rod 6 of an anchoring means on the bottom of the swimming pool. The vertical rigidity of the connecting means 20 is ensured by a bending bar 42 engaged and welded to its

  ends in openings crossing webs, 11-beams

  placed on either side of the anchoring means comprising the rod 6.

  The connection between the drawbar 42 and the threaded end of the rod 6 is provided by a stud 43 engaged in a through opening of the

  bending bar 42 and screwed onto the end of the rod 6. The stud 43 comprises

  carries a head bearing on the upper surface of the bending bar. In Figure 23B, two pairs of connecting means are shown.

  each comprising a bending bar ensuring the connection between the

  11 parallel trelles of a support frame and two pairs of means

  anchor aligned in part of the bottom of the pool.

  In FIG. 24A, two parallel beams 11 of a chassis have been shown, between which is placed a connecting device 20 comprising a piece for taking up horizontal forces 44 welded between the base parts of the beams 11; the profiled part 44 has a shape as described above and shown in Figure 15. The connecting means 20 comprises

  in addition a set of recovery of vertical forces whose rigidity is

  ended with the characteristics of a torsion beam 45.

  The torsion beam 45 is engaged and fixed by welding to one of

  its ends, in an opening of a spacer 46 fixed between the pouches

  very 11, in a transverse direction. The torsion beam 45 is available

  placed above the internal base part of one of the beams 11 and comes to bear by a part 45a slightly projecting downwards on the wing

internal of the beam 11.

  At the end of the torsion bar opposite the end fixed on the spacer 46 is attached and welded a force transmission arm 47

  comprising two uprights and a bottom crossed by a passage opening

  wise rod 6 of an anchoring means.

  On the threaded end of the rod 6, is screwed a nut 35 ensuring the

  connection between the force transmission arm 47 and the anchor rod 6.

  The vertical forces exerted on the structure comprising the

  trelles 11 cause a torsional deformation of the beam 45 which cannot

  deform in flexion due to its support 45a on the inner wing of the

  trelle at which it is mounted.

  The stiffness of the link in the vertical direction can be adjusted by

  adjusting the deformation characteristics of the torsion beam 45, that is

  ie by adjusting the geometrical characteristics of this beam.

  In FIGS. 24B and 24C, two connection means 20 and

  20 'comprising a 45 or 45' torsion bar connected by a trans-

  effort mission 47 or 47 ', respectively to a first rod 6 of a first anchoring means and to a second rod 6' of a second anchoring means

  a set of anchoring means aligned between the beams 11.

  The torsion bars of the successive connecting means are available

  entered alternately at a first and at a second

support frame beam.

  In Figures 25A and 25B, there is shown a connecting means 20 between the support frame comprising two parallel beams 11 and a rod

6 of an anchoring means.

  The connecting means 20 comprises a plate 21 welded along two opposite lateral sides on the base parts of the two parallel beams 11 and a set deformable in the vertical direction comprising a beam 48 deformable in bending freely bearing at its ends on the internal wings of the base parts of the beams 11. The rod 6 of an anchoring means passes through the beam 48, in its central part by an opening opening into a counterbore for receiving a nut 25 for fixing the beam 48 on the end of the rod 6. Reinforcement gussets 49 are

  designed to compensate for the loss due to counterbore.

  In Figure 26, there is shown an alternative embodiment of the means

  link 20 comprising a bending beam 48 '.

  The beam 48 'is embedded in an opening crossing the core of

  one of the beams 11 and machined in a gusset reinforcement gusset

be 11.

  The opposite free end of the cantilever beam 48 'is connected to

  the rod 6 of an anchoring means by means of a nut 35.

  As shown in FIGS. 27, 28, 29A, 29B and 30, it is also possible to use connection means comprising a deformable element under the effect of vertical steering forces, with controlled rigidity, constituted by

  a wavy or curved flange.

  In the case of the connecting means 20 shown in FIG. 27, the flange 49 is an S-shaped flange obtained by cutting and drilling

  a metal plate; the flange has branches substantially pa-

  joined together separated by slits and connected together in an S or zigzag shape, the flexion of the different branches of the flange

  producing in the common parts of two successive branches.

  As can be seen in FIG. 28, the branch 49 ′ in a zigzag or in Speut comprise an increased number of successive branches that are substantially parallel. A drilling of the branches of the flange 49 or 49 'makes it possible to engage and screw on an end part of the rod 6 of an anchoring means, a

fixing nut 25.

  In the case of the embodiment shown in FIGS. 29A and 29B, the connection means 20 each comprise a U-shaped flange

  whose substantially vertical branches have wavy shapes.

  The horizontal lower branch of the U is crossed by an opening

  ture allowing the attachment of a rod 6 of an anchoring means by

through a nut 35.

  The connection means shown in FIG. 30 includes a flange 51 produced by folding a metal bar or strip in the form

  of a flattened O which is not fully closed.

  The two substantially parallel and horizontal parts of the O are drilled so as to ensure the passage of the rod 6 of an anchoring means and of a nut 25 for fixing the rod 6 on the free end part of the

flange 51.

  In the case of each of the embodiments of a connecting means

  its represented in FIGS. 27, 28, 29A, 29B and 30, the flange is fixed at one of its ends or at its two ends on one or two beams

11 of the support frame.

  In all cases, the fixing method according to the invention using connecting means having rigidities in the different directions in which the forces are exerted on the large structure, adapted to the position of the fixing points on the structure and at the position of the anchoring means on the bearing surface, makes it possible to distribute the forces between the different fixing points of the structure and thus to limit the stresses undergone by the structure. In particular, this avoids exercising

  excessive stresses in certain parts of the structure,

  that it is subject to stresses such as those accompanying an earthquake, stresses due to climatic variations exerted on the structure or stresses exerted on the structure in service. The rigidities of the connecting means can be easily adapted

  at the various points of connection of the structure, when the ef-

  strong likely to be exerted on the structure, at the fixing points, by

  example by calculation or by modeling.

  As shown in the description, the connecting means can

  present many different shapes from each other and their rigidity

  dity can be set to the selected values in various ways.

  The embodiment and the size of the connecting means depends

  in particular the arrangement of the anchoring means with respect to the structure

  large size and the provision of different means

  anchoring to each other.

  The invention applies not only to the fixing of a storage assembly for fuel assemblies in a deactivation pool, but also in many other cases where it is necessary to ensure the fixing of a large structure. dimension, at anchor points, in particular when the arrangement of anchor points is pre-existing and is not provided according to the characteristics of the large structure. The invention also applies in the case where it is necessary to

  fastening a large structure to a bearing surface

  sion which does not have a homogeneous resistance at all points, regardless of the arrangement of the anchoring points of the structure on the bearing surface. The invention has many applications not only in the case of the construction of nuclear power plants but also in the field of the construction of power plants of other

  types, factories or large industrial installations, buildings

or works of art.

Claims (30)

  1. Method for fixing a large structure on a substantially planar support surface (3), by means of a plurality of anchoring means (4) having a part (6) projecting from to the support surface, each arranged in an area of a plurality of areas distributed along the support surface, consisting in depositing the structure (7, 7a, 8, 9, 10)   on the bearing surface and to connect it to each of the anchoring means (4),   characterized by the fact that the structure is connected to each of the anchoring means (4) by a connecting means (18, 19, 19 ', 20) having rigidity characteristics in at least one of the directions parallel to the support surface and in a direction perpendicular to the support surface, adapted to the position   anchoring means (4) on the bearing surface (3), and relative to the structure   structure (7, 7a, 8, 9, 10), to distribute the forces exerted between the bearing surface (3) and the structure, under the effect of stresses, so as to avoid the appearance of excessive stresses at any point in the structure   (7, 7a, 8, 9, 10) or in at least one of the anchoring means.   2. Method according to claim 1, characterized in that the   connecting means (18, 19, 19 ', 20) have characteristics of rigidity adjusted   tees, in at least one of two directions (X, Y) perpendicular between   them in a plane parallel to the bearing surface (3) and in a direction Z per-   pendulum to the bearing surface (3).   3 Method according to any one of claims 1 and 2, ca-   characterized by the fact that the connecting means (20) are fixed on the large structure (7, 7a, 8, 9, 10), rigidly, in particular by   welding, before the large structure is placed on the surface bearing face (3).   4. Method of fixing according to any one of claims 1   and 2, characterized in that the connecting means (18, 19, 19 ') are fixed to the large structure (7, 7a, 8, 9, 10) after having deposited the   large structure on the support surface (3).   5. Device for fixing a large structure (7, 7a, 8, 9, 10) to a substantially planar support surface (3), by means of a plurality of anchoring means (4 ) having a part (6) projecting by   relative to the bearing surface (3), each arranged in an area of more   reality of zones distributed along the bearing surface (3), characterized in that it comprises a plurality of connecting means (18, 19, 19 ', 20) for connecting   the structure (7, 7a, 8, 9, 10) to each of the anchoring means (4) and that each   each of the connecting means (18, 19, 19 ', 20) has rigidity characteristics in at least one of a direction parallel to the bearing surface (3)   and in a direction perpendicular to the bearing surface (3), adapted to the position   sition of the anchoring means (4) on the bearing surface and relative to the   large structure (7, 7a, 8, 9, 10).   6. Device according to claim 5, characterized in that at least one of the connecting means (20) comprises a plate (21) fixed by welding on at least one part (11) of the large structure and having a through engagement opening on the projecting part (6) of an anchoring means (4).   7. Device according to claim 6, characterized in that the rigidity of the plate (21) of rectangular shape placed in an arrangement parallel to the bearing surface (3), in at least one direction parallel to the surface of support (3) is determined by at least one of the dimensions (a, b) of the plate (21) in a direction parallel to the support surface (3) and by The thickness (e) of the plate.   8. Device according to claim 7, characterized in that the   plate stiffness is adjusted by providing at least one transverse opening   health (24) of determined diameter (Dx, Dy) in a part of the plate.   9. Device according to claim 8, characterized in that the plate has at least two openings (24) aligned in a direction   X or in a direction Y perpendicular to each other and parallel to the surface bearing face (3).   10. Device according to claim 7, characterized in that the rigidity of the plate (21) in at least one of the directions X, Y parallel to the bearing surface (3) is adjusted by at least one notch in an edge of the plate (21) and by the length of at least one weld bead (23,   23 ') connecting the plate (21) to at least part of the structure (11).   11. Device according to any one of claims 6 to 10, ca-   characterized by the fact that the plate (21) is crossed by two openings (22,   22 ') for the passage of a projecting part of an anchoring means (4).   12. Device according to any one of claims 6 to 11, ca-   characterized by the fact that the plate (21) of at least one connecting means (20) is fixed along an external edge of the large structure (7, 7a, 8.9, 10).   13. Device according to claim 5, characterized in that at least one connecting means (20) comprises a fixing lug substantially   plane (27) comprising at least one connection base by welding to a part   tie (11) of the large structure (7, 7a, 8, 9, 10) and a part traversed by an opening (22) for engaging a projecting part of a anchoring means.   14. Device according to claim 5, characterized in that at   at least one connecting means (18) comprises a body or housing (30) comprising   nant a first base plate (30a) pierced with an opening (32) for passage of a projecting part (6) of an anchoring means, a second base (30b) parallel to the first base (30a) through which the fixing means of the housing (20) of the connecting means (18) pass through at least one part (11) of the large structure (7, 7a, 8, 9, 10) and four flexible arms (31) perpendicular to the first plate (30a) and the second plate (30b) of the housing, arranged substantially along the faces of a parallelepiped and ensuring the connection between the first plate (30a) and the second plate (30b) of the housing which are placed in the service position of the connecting means, in arrangements parallel to the bearing surface (3) of the large structure, the bending stiffness of the arms (31) of the housing determining the stiffness of the connecting means under forces parallel to the bearing surface (3). -   15. Device according to claim 14, characterized in that the   connecting means (18) further comprises an assembly (35, 36) having a ri-   adapted gidity, in a Z direction perpendicular to the bearing surface (3)   of the large structure.   16. Device according to claim 15, characterized in that the assembly (35, 36) with rigidity adjusted in the direction Z perpendicular to the bearing surface (3) consists of a nut (35) capable of being screwed onto a threaded part of the projecting part (6) of the anchoring means (4) and at least one elastic washer (36) interposed between a head of the nut (35)   and an upper surface of the housing (30).   17. Device according to claim 5, characterized in that the connecting means (20) comprises an assembly (36a, 36b, 37) force limiter   in at least one direction parallel to the bearing surface (3) and a set   ble (35, 36) with rigidity adjusted in a direction Z perpendicular to the sur- bearing face (3).   18. Device according to claim 17, characterized in that the force limiting assembly (36, 36b, 37) consists of a plate (36a) secured to a part (11) of the large structure ( 7, 7a, 8, 9, 10), a plate (36b) comprising an opening engaged on the projecting part (6) of the anchoring means and screws (37) for tightening a sliding surface of the first plate (36a) on a sliding surface of the second plate (36b) parallel to the bearing surface (3), with a force adjusted support.   19. Device according to Claim 18, characterized in that the assembly (35, 36) with rigidity adjusted in a direction Z perpendicular to the bearing surface (3) consists of a nut (35) which can be engaged by screwing onto a threaded end part of the projecting part (6) of the anchoring means and at least one elastic Belleville type washer (36) interposed between a head of the nut (35) and a bearing surface superior of   the first sliding plate (36a).   20. Device according to claim 18, characterized in that   the assembly (35, 39, 40) with rigidity adjusted in a direction Z perpendicular to   the surface of the support surface (3) consists of a nut (35) capable of being screwed onto a threaded end part of the protruding part (6) of the anchoring means (4), a bar of torsion (40) integral with a part (11) of the large structure (7, 7a, 8, 9, 10) and a link arm (39)   between the nut (35) and the torsion bar (40).   21. Device according to claim 18, characterized in that the assembly (35, 41) with rigidity adjusted in a direction Z perpendicular to the bearing surface (3) consists of a nut (35) capable of being screwed onto a threaded part of the projecting part (6) of the anchoring means and a bending bar (41) fixed to at least one part (11) of the large structure (7, 7a, 8, 9, 10) disposed substantially parallel to the bearing surface (3) and having a through engagement opening of the nut (35).   22. Device according to claim 18, characterized in that the assembly (35 ', 35'a) with rigidity adjusted in a direction Z perpendicular to the bearing surface (3) consists of a nut (35') capable of being screwed onto an end part of the projecting part (6) of the anchoring means (4) comprising a part (35'a) deformable in the direction Z   perpendicular to the bearing surface preferably constituted by a door corrugated bellows.   23. Device according to claim 5, characterized in that at least one connecting means (20) comprises an assembly (42, 43) having a rigidity adjusted in a direction Z perpendicular to the bearing surface (3) consisting by a bending bar (42) fixed at its ends on parts   (11) of the large structure (7, 7a, 8, 9, 10) and crossed to the   twisting of its central part by an opening and a stud (43) capable of being engaged in the through opening of the bending bar (42) and of being fixed by screwing on a threaded end of the projecting part (6 ) of the anchoring means (4), the stud (43) having a head for pressing on the bending bar (42) of the stud screwed onto the threaded part of the projecting part (6) of the anchoring means.   24. Device according to claim 5, characterized in that at least one connecting means (20) comprises an assembly (25, 45, 47) whose rigidity is adjusted in a direction Z perpendicular to the bearing surface ( 3) of the large structure (7, 7a, 8, 9, 10) consisting of a torsion bar (45) fixed at one of its ends on a part (46) of the large structure, a force transmission arm (47) to the projecting part (6) of an anchoring means (4) and a nut (25) capable of being fixed by screwing on a threaded end part of a rod (6) in   projection of the anchoring means (4), to ensure the connection of the transmission arm   effort force (47) integral with the torsion bar (45) and the projecting rod (6) of the anchoring means (4).   25. Device according to claim 5, characterized in that at least one connecting means (20) comprises an assembly with rigidity adjusted in a direction Z perpendicular to the bearing surface (3) constituted by a beam (48, 48 ') substantially parallel to the support surface (3) connected by simple support or by embedding at least one part (11) of the large structure (7, 7a, 8, 9, 10) having a through opening passage of an end part of a rod (6) projecting from the anchoring means (4) and a nut (25) capable of being screwed onto a threaded part   of the projecting rod (6) passing through the opening of the beam (48, 48 ').   26. Device according to claim 5, characterized in that at least one connecting means (20) comprises an assembly with rigidity adjusted in a direction Z perpendicular to the bearing surface (3) constituted by a flange having a shape curved or wavy fixed on a part (11) of the large structure and connected to a part (6) projecting from a means anchor (4).   27. Device according to claim 26, characterized in that the flange (49, 49 ') has a zigzag shape and is obtained by cutting of a metal plate.   28. Device according to claim 26, characterized in that the flange (50) obtained by folding a metal plate has a shape   in U, the branches of the U having wavy shapes.   29. Device according to claim 26, characterized in that the flange obtained by folding a strip or a metal bar has the   form of an O partially closed.   30. Method for refitting a storage pool of a nuclear power station for the storage of fuel assemblies in the pool water, inside storage racks (17) having a bottom (3) substantially flat and horizontal on which are distributed anchoring means (4) each comprising a rod (6) projecting above the bottom (3) of the swimming pool, characterized by the fact: - that at least one support frame is produced consisting of intersecting beams (11), in the form of a trellis, - that at least one support frame (7, 7a, 8, 9, 10) is deposited on the bottom (3) of the storage pool fuel assemblies (1), - that at least one support frame (7, 7a, 8, 9, 10) is fixed to the bottom of the pool (3), to each of the anchoring means ( 4) using a process   fixing according to any one of claims 1 to 4 and,   - that the storage racks (17) of fuel assemblies are fixed to a flat upper part of the at least one support frame (7, 7a, 8.9, 10).