GB2342769A

GB2342769A - Water nuclear reactor equipped with a receptacle containing deformable inner structures

Info

Publication number: GB2342769A
Application number: GB9922966A
Authority: GB
Inventors: Jacques Marseille
Original assignee: Commissariat a lEnergie Atomique CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 1998-10-14
Filing date: 1999-09-28
Publication date: 2000-04-19
Anticipated expiration: 2019-09-28
Also published as: DE19949583A1; GB2342769B; JP2000121771A; FR2784785B1; DE19949583B4; KR100671903B1; KR20000029087A; FR2784785A1; GB9922966D0

Abstract

In a water reactor, a receptacle (20) is placed underneath the core (12), inside vessel (10) such as to collect the corium formed in the event of accidental fusion of the core (12). To absorb the shock wave produced by a possible vapour explosion, deformable, generally metallic, inner structures (38) are placed inside receptacle (20). Containers (48), for example spherical-shaped, containing a material able to cool the corium, such as silica, may also be placed inside receptacle (20).

Description

1 2342769 WATER NUCLEAR REACTOR EQUIPPED WITH A RECEPTACLE CONTAINING

DEFORMABLE INNER STRUCTURES

DESCRIPTION

Field of the invention

The invention relates to a pressurized water or boiling water nuclear reactor, whose vessel contains a basin-shaped receptacle intended to collect the "'corium", that is to say the solid or liquid debris derived from the core of the reactor in the event of the latter's accidental fusion.

State of the art In nuclear reactors, a large number of systems have been considered and developed over the last few years for the purpose of limiting the consequences of a serious accident causing partial or full fusion of the reactor core.

In particular, as illustrated by document FR-A-2 341 181, a withholding device has already been described which can be placed at the bottom of the nuclear reactor vessel. Such withholding device is intended to avoid perforation of the vessel by the corium which may be formed in the event of accidental fusion of the reactor core. The withholding device comprises several spaced out horizontal plates, positioned underneath the core and fixed to the wall of the vessel. These horizontal plates are crossed by openings which are staggered from plate to plate and whose edges project upwards. In the event of accident, 2 the corium flows down under gravity through the openings made in the plates, and then moves up into a bell-shaped distributor positioned in the centre of the horizontal plates and resting on the bottom of the 5 vessel.

Also, in the particular case of a nuclear reactor cooled by a liquid metal, document US-A-3 964 966 demonstrates that consideration has been given to placing a corium receptacle underneath the core of the nuclear reactor inside the vessel itself. This receptacle is directly suspended from the lower horizontal plate supporting the core. Heat exchange piping crosses the base of the receptacle and projects upwards inside the receptacle. These pipes are closed at their top end and communicate with the inside of the receptacle via holes provided close to this top end.

Irrespective of the geometry of the receptacle device it is considered incorporating inside the vessel of a water reactor, there is a very slight risk that accidental fusion of the core is followed by an explosion. For the corium fragments into small particles while it flows towards the bottom of the vessel. The water contained in the reactor vessel vaporises on contact with the small corium particles. A vapour film is formed around each particle, creating favourable conditions for an explosion likely to cause a high energy shock wave. Given the origin of this type of explosion it is usually called "'vapour explosion".

At the present time, the receptacle devices described to collect and maintain the corium in the bottom of a water reactor vessel are not protected from the effects of said vapour explosion should such occur.

3 Despite the low probability of interaction between the vaporised water and the corium, the possibility of this type of explosion cannot, however, be fully dismissed. The extremely powerful pressure peak generated by the explosion could damage the intactness of the receptacle device and therefore its effectiveness.

Disclosure of the invention

The subject matter of the invention is precisely a pressurized water or boiling water nuclear reactor fitted with a corium. collection device incorporated into the vessel, whose original design can protect it from the effects of a possible vapour explosion and, consequently, can preserve the intactness of the receiving device in the event of accident.

According to the invention, this result is obtained by means of a water nuclear reactor, comprising a vessel and a reactor core housed in the vessel, said reactor being characterized in that it also comprises a basin-shaped receptacle housed in the vessel underneath the core and made, at least in part, of refractory material, said receptacle being able to collect the corium formed during any accidental fusion of the core and containing deformable inner structures, at least in the proximity of an inner surface of the receptacle.

In a nuclear reactor built in this way, the corium formed during accidental fusion of the core flows out and fragments on entering the receptacle. Should a vapour explosion occur, the energy released by the explosion would be dispersed at its source by the deformable inner structures contained in the receptacle. The latter would therefore remain intact 4 allowing it to effectively collect the entirety of the corium derived from the core in fusion.

Also, a large mass of corium at high temperature can cause partial melting of the inner structures contained in the receptacle. The mass of material, such as iron, added to the corium in this event contributes towards gradual lowering of corium temperature. In this way the risk of damage to the receptacle by melting of the refractory material is limited.

Preferably, the deformable inner structures are metal structures arranged such that water can circulate inside said structures. This arrangement contributes towards cooling of the corium and receptacle in the event of accident.

In preferential, but optional, manner the receptacle may also contain containers, in the form of spheres for example, in which a material is placed, preferably a silica-based material. If the containers are crushed the corium comes into contact with this material which constitutes a chemical additive able to lower its temperature.

According to a first embodiment of the invention, the deformable inner structures comprise a lattice-work of crossed bars arranged against the inner surface of the receptacle.

Depending upon the case, the latticed bars may either fill the greater part of the receptacle, or be associated with a structure of perforated metal sheets forming compartments inside the lattice-work. In the first case, the containers filled with a silica-based material for example may possibly be housed between the crossed bars. In the second case, said containers are preferably housed at least in the compartments closest to the lattice- work of crossed bars.

According to a second embodiment of the invention, the deformable inner structures comprise spaced out metal sheets, arranged substantially parallel to the inner surface of the receptacle, and counter-braces connecting the metal sheets together.

In one variant of this second embodiment of the invention, the metal sheets and counter-braces form modules which contain tubes oriented substantially parallel to the inner surface of the receptacle. These tubes may in this case form containers filled with a material, for example a silica-based material.

According to a third embodiment of the invention, the deformable inner structures comprise a honeycomb structure whose partitions are substantially perpendicular to the inner surface of the receptacle.

In this case, the alveoli delimited by the honeycomb structure may form containers filled with a material, for example containing silica.

According to a fourth embodiment of the invention, the deformable inner structures comprise tubes placed in successive layers substantially parallel to the inner surface of the receptacle and leading to a central collector housed in the bottom of the receptacle.

Advantageously, the receptacle may be surmounted by a perforated distribution plate which contributes to spreading out the corium in the receptacle. This perforated distribution plate may in particular have a conical shape whose tip is directed downwards if the 6 deformable inner structures are arranged in successive layers inside the receptacle.

Also, in order to improve the cooling of the receptacle in the event of accident, through water circulation via natural convection, the receptacle is separated from the bottom of the vessel by a space that opens upwards.

Brief description of the drawings

As non-restrictive examples, different embodiments of the invention will be described with reference to the appended drawings in which:

- figure 1 is a vertical cross-section giving a diagram of the lower part of a water nuclear reactor whose vessel incorporates a receptacle according to a first embodiment of the invention; - figure 2 is cross-section view comparable with figure 1, illustrating a first variant of the first embodiment of the invention; - figure 3 is a cross-section view comparable with figures 1 and 2, illustrating a second variant of the first embodiment of the invention; - figure 4 is a cross-section view comparable with figures 1 to 3 illustrating a second embodiment of the invention; - figure 5 is a cross-section view comparable with figures 1 to 4, illustrating a variant of the second embodiment of the invention; figure 6 is a cross-section view comparable with figures 1 to 5, illustrating a third embodiment of the invention; and 7 figure 7 is a cross-section view comparable with figures 1 to 6, illustrating a fourth embodiment of the invention.

Detailed description of several preferred embodiments 5 of the invention

The different embodiments of the invention described below, and their variants, all concern pressurized water nuclear reactors. However, as has already been pointed out, the invention is not limited to this type of reactor and generally concerns all water reactors, in particular boiling water reactors.

The different embodiments and variants which will be described have numerous identical or comparable parts. These different parts will only be described once with reference to figure 1. The same reference figures will be used to denote the said identical or comparable parts in the other figures when clarity of description requires their mention.

The first embodiment of the invention is described with reference to figure 1.

In this figure, reference 10 denotes the reactor vessel. More precisely, only the lower part of the vessel is shown. In its central part, vessel 10 contains reactor core 12 and its associated inner equipment.

Core 12 is usually formed of a large number of assemblies of nuclear fuel, arranged vertically and juxtaposed. The assemblies rest on a horizontal lower plate 14. Plate 14 is perforated next to each of the assemblies of nuclear fuel to enable circulation inside these assemblies of the cooling water contained in 8 vessel 10. A perforated flow distribution plate 16, preferably with a convex lower part, is generally fixed to and below horizontal lower plate 14 Core 12 of the reactor, and its associated inner equipment, such as horizontal lower plate 14 and perforated plate 16, rest on the vertical cylindrical wall of vessel 10 via supporting and guiding devices 18.

It is to be noted that core 12 and its associated inner equipment may be of any shape, different to those shown in figure 1, while remaining within the scope of the invention.

In accordance with the invention and as illustrated in figure 1, a basinshaped receptacle 20 is placed inside vessel 10 underneath core 12 of the reactor. More precisely, receptacle 20 is placed in between perforated plate 16 and the convex, generally hemispherical, base of vessel 10.

Receptacle 20 is designed to collect the cori'Um in the event of accidental fusion of reactor core 12. It is recalled that the term "corium"' denotes the fusion mass that is produced should such an accident occur and generally contains the nuclear fuel, its cladding materials and the cladding materials of the reactor control rods and the internal structures associated with core 12. Receptacle 20 is arranged and dimensioned such as to collect the entirety of the corium in the event that a serious accident should lead to complete fusion of reactor core 12.

Preferably, and as illustrated in figure 1, receptacle 20 is separated from the base of vessel 10 by a space 22 leading upwards between the peripheral 9 upper edge of the receptacle and vessel 10. This space 22 allows circulation of the water contained in reactor vessel 10 as shown by the arrows in figure 1. Should an accident occur, water circulation is set up automatically in this space 22 by natural convection.

The effect produced by this water circulation is to cool receptacle 20.

Receptacle 20 comprises at least one layer of bricks 24 in refractory material. This material is chosen such as to have as high a melting temperature as possible, and good chemical compatibility with the corium. It may in particular be a zirconium-based ceramic material which also has the advantage of being widely available on the industrial market.

As illustrated in the diagram in figure 1, bricks 24 are juxtaposed and preferably have complementing adjacent edges, for example in U or dovetail shape which interlock into one another.

Receptacle 20 also comprises a metal casing inside which bricks 24 are placed. This metal casing may in particular be made of stainless steel. It comprises an inner 26 and an outer skin 28 which fully cover the layer or layers of bricks 24 on the inner and outer surfaces of the receptacle respectively. The metal casing also comprises an upper flange 30 connecting together the upper edges of the inner 26 and outer 28 skins of receptacle 20.

The upper flange 30 may be used to suspend receptacle 20 in vessel 10. In this case it rests on supports 32 provided inside vessel 10 as illustrated in the diagram of figure 1.

As a variant or complement, radiating reinforcements (not shown) having a radial orientation in relation to the vertical axis of vessel 10 may be interposed in space 22 separating the bottom of the S vessel from receptacle 20. In this case the radial reinforcements are provided with holes to contribute towards the circulation of water inside space 22.

In the embodiment shown in figure 1, receptacle 20 has been given a substantially hemispherical shape, concentric with the shape of the base of vessel 10.

In a variant of embodiment not shown, this substantially hemispherical shape may be extended upwards by a substantially cylindrical part centred over the vertical axis of vessel 10. This arrangement may be chosen in particular if the total volume of the corium. likely to be formed during a serious accident exceeds the available volume inside receptacle 20 if the latter is solely formed of a hemispherical part. Evaluation of the volume available inside receptacle 20 is made by taking into consideration the presence of a certain number of structures inside the receptacle, as will be described more in detail below.

So that the entirety of the corium produced by core 12 during a serious accident may be effectively collected in receptacle 20, it is possible to place a ring collector 34 over its upper edge as illustrated in figure 1. Ring collector 34 may in particular rest on upper flange 30 of receptacle 20 via a cross-beam structure 36.

The top surface of ring collector 34 has approximately the shape of a hopper curved inwards and extending upwards as far as the proximity of the wall of vessel 10. More precisely, an allowance limited to a few centimetres is provided between collector 34 and the wall of vessel 10, such as to prevent debris and flow from the core in fusion from penetrating inside space 22 provided between receptacle 20 and the base of vessel 10.

In accordance with one essential characteristic of the invention receptacle 20, at least in the proximity of its inner surface materialized by inner skin 28, contains deformable inner structures 38. The primary purpose of these deformable inner structures 38 is to prevent any possible vapour explosion occurring inside the receptacle from causing damage to the latter. More precisely, the deformation of these structures caused by the shock wave induced by a possible vapour explosion disperses and/or attenuates the energy released by this explosion. Receptacle 20, in particular refractory bricks 24, is therefore protected from the shock wave caused by the explosion.

In the first embodiment of the invention illustrated in figure 1, deformable inner structures 38 comprise a lattice-work of crossed bars 40 arranged over a certain thickness against the inner surface of receptacle 20, materialized by inner skin 26. Crossed bars 40 are welded to one another and to inner skin 26 and are arranged substantially parallel to the inner surface of the receptacle, for example in vertical and horizontal planes. They form a metallic lattice- work providing spaces between the bars that are sufficient to allow circulation of water. The thickness of the lattice-work and the section, distancing and orientation of bars 40 of which it is formed are 12 determined such as to obtained the desired absorbing of the shock wave produced by a possible vapour explosion.

In the embodiment shown in figure 1, the latticework of crossed bars 40 is coated on the inside with a metallic skin 42, in which is placed a structure of thick perforated metal sheets 44 forming another part of deformable inner structures 38. The thick perforated metal sheets 44 are welded to one another and to metallic skin 42. They are placed at regular distances and are arranged for example horizontally and vertically in three perpendicular directions, such that they form compartments 46 between themselves, of cubic shape for example.

As illustrated in figure 1, the compartments 46 closest to metallic skin 42 and the lattice-work of crossed bars 40 contain metallic containers 48, preferably in the form of spheres. These containers 48 contain a material forming a chemical additive able to lower the temperature of the corium should it come into contact with this material after destruction of the container casing. This material is preferably a silicabased material such as silica dioxide.

In the embodiment of figure 1, a perforated distribution plate 50 overhangs receptacle 20 and is supported by flange 30. Plate 50 is metallic and horizontal.

In the event of a serious accident leading to fusion at least in part of reactor core 12, corium C which is produced (figure 1) fragments into small particles while flowing down towards receptacle 20. It enters the latter through plate 50. While continuing to move down inside the structure of perforated metal 13 sheets 44, the small corium particles vaporise the water coming into their contact such that a vapour film forms around each particles. There is therefore a risk that a vapour explosion may occur in the central part of receptacle 20. In this hypothesis, deformable inner structures 38 placed in this receptacle, in particular side compartments 46 filled with spherical containers 48 and the lattice-work of crossed bars 40, create a protective mattress which absorbs the shock wave produced by a possible explosion. The intactness of receptacle 20 is therefore preserved.

Also, in the event of a vapour explosion, the metal sheets forming compartments 46 become deformed and crush containers 48 which release the material they contain which is generally silica-based. Concomitantly with the melted metallic inner structures and with the water contained in the vessel, the addition of this material contributes to lowering the temperature of the corium down to a temperature substantially below the melting point of the refractory material of which bricks 24 are made. By way of illustration, a percentage of 14 % by mass of silica can lower the temperature of the corium by about 4000C. Bearing in mind that the temperature of the corium is approximately equivalent to between 2600'C and 2800'C and that this temperature is generally very close to the temperature which refractory bricks 24 can withstand, this largely'contributes towards maintaining the intactness of these bricks and therefore of receptacle 20.

Figure 2 shows a variant of the first embodiment of the invention just described with reference to figure 1. The main difference between this variant and 14 the embodiment just described concerns the deformable inner structures 38. In this variant, the lattice-work of crossed bars 40 practically fills the entirety of receptacle 20, such that the structure of thick Perforated metal sheets 44 in figure 1 is omitted.

As previously, the crossed metal bars 40 are welded to one another and to inner skin 26 in an arrangement which forms passage-ways between the bars to facilitate the circulation of water.

This variant also differs from the embodiment in figure 1 through the absence of containers housing a material able to lower the temperature of the corium. In this case, lowering of corium temperature is ensured by melting of part of the lattice-work of crossed bars 40 and its mixing with the corium. It is to be noted also that this lattice-work contributes to fragmenting the corium mass, making it more amenable to cooling while providing sufficient space to receive the entirety of the corium inside receptacle 20.

Also, in this variant of figure 2, the horizontal distribution plate 50 of figure 1 is omitted and the upper surface of deformable inner structures 38 contained in receptacle 20 is of conical shape whose tip is directed downwards. This upper surface therefore acts as a permeable hopper which tends to convey the most part of corium C towards a central part of the structure, centered over the centre of receptacle 20. With this arrangement, any vapour explosion is highly likely to occur at a site close to this central region.

The greater part of the thickness of the lattice-work of crossed bars 40 therefore takes part in absorbing the shock wave produced by this explosion.

is In figure 3 a second variant of the first embodiment of the invention is shown.

AS in the first variant, the lattice-work of crossed bars 40 forming deformable inner structures 38 fills the most part of receptacle 20. However the distance between bars 40 is greater, such that containers 48, similar to those described with reference to figure 1, are inserted in between crossed bars 40 inside the lattice-work itself. These containers 48, preferably in the form of spheres, as previously contain a material able to lower the temperature of the corium. such as a silica- based material.

The configuration of the upper surface of deformable inner structures 38 is, for the remainder, comparable with that of the first variant described with reference to figure 2.

A second embodiment of the invention is now described with reference to figure 4.

In this second embodiment of the invention, deformable inner structures 38 comprise metal sheets 52 oriented parallel to the inner surface of receptacle 20 and placed at regular intervals. Metal sheets 52 in the form of spherical caps are connected together by counter-braces 54 positioned in vertical planes passing through the axis of vessel 10. Metal sheets 52 and counter-braces 54 are welded metal parts, arranged such as to enable circulation of water between the metal sheets. For this purpose, holes 56 are provided in counter-braces 54 as shown in figure 4.

In this second embodiment of the invention, a perforated distribution plate 50 overhangs receptacle 16 as in the embodiment shown in figure 1. However, instead of being flat and horizontal, perforated plate 50 is cone-shaped and its tip is directed downwards. As shown in figure 4, the central part of perforated distribution plate 50 can have a central opening of greater size in its part positioned above metal sheet 52 closest to the centre of receptacle 20.

In this second embodiment of the invention, the deformable inner structures formed by metal sheets 52 and counter-braces 54 absorb the shock wave produced by a possible vapour explosion inside receptacle 20. The intactness of the receptacle can therefore be preserved.

In the absence of a particular material able to lower the temperature of the corium, this temperature lowering effect is ensured by the iron contained in metal sheets 52 and counter-braces 54. By reducing the temperature of the corium to a level below the temperature which refractory bricks 24 can withstand, this secondary effect of inner structures 38 also contributes to preserving the intactness of receptacle 20.

In figure 5 a variant of the second embodiment of the invention is shown.

This variant differs essentially from the embodiment just described through the fact that it only comprises a limited number of metal sheets 52 (two for example) arranged in the proximity of the inner surface of receptacle 20. Also, the spaces formed between metal sheets 52 are divided into modules 58 by counter-braces 54 arranged firstly in vertical planes passing though the axis of the vessel and, secondly in planes 17 perpendicular to these vertical planes and metal sheets 52. With the exception of modules 58 located in the bottom of the receptacle, which are approximately cylinder shaped, the other modules 58 are in the form 5 of spherical sectors.

Also, each of modules 58 thus demarcated by metal sheets 52 and counterbraces 54 contains at least two layers of curved tubes arranged substantially parallel to the inner surface of the receptacle. Curved tubes 60 may in particular be arranged in staggered layers.

The deformable inner structures made in this way are more compact than in the embodiment shown in figure 4 which leaves free all the central part of receptacle 20. The effects of shock wave absorption and lowering of corium temperature in the event of a vapour explosion are identical to those described previously.

It is to be noted that all the metal parts formed by metal sheets 52, counter-braces 54 and tubes 60 are welded to one another and that modules 58 formed by these parts are welded together.

In the arrangement just described with reference to figure 5, tubes 60 of each module 58 form containers which may be filled at least in part with a material, for example a silica-based material able to lower the temperature of the corium with which it comes into contact.

A third embodiment of the invention is now described with reference to figure 6.

As illustrated in this figure, deformable inner structures 38 contained in receptacle 20 in this case comprise a honeycomb structure 61 which, over a certain 18 thickness, covers the inner surface of receptacle 20. The partitions of the honeycomb structure 61 are oriented substantially radial to the centre of the receptacle, that is to say substantially parallel to its inner surface. They form alveoli whose section may be of any shape in particular hexagonal or circular.

Honeycomb structure 61 is metallic and coated on the inside with a skin 62 that is also metallic.

The effects of honeycomb structure 61 are similar to those previously described with reference to figures 2 and 4.

It is to be noted that an accelerated cooling effect of the corium collected in receptacle 20 may be obtained by filling, at least in part, the containers formed by the alveoli of honeycomb structure 61 with an appropriate material, for example a silica-based material.

Finally, a fourth embodiment of the invention shall be described with reference to figure 7.

In this case, the deformable inner structures 38 contained in receptacle 20 comprise metal tubes 64 welded to one another and arranged in successive layers substantially parallel to the inner surface of receptacle 20. Tubes 64 are arranged in staggered layers. Their upper ends are welded to perforated distribution plate 50 such they lead to above the plate through the perforations in the plate. The lower end of each of tubes 64 is welded to a perforated cylindrical collar centred over the vertical axis of reactor vessel 10 such as to lead into a central collector 68 through perforations in collar 66. The ends of tubes 64 connected to collar 66 all abut each other, but the 19 tubes gradually diverge from one another as they rise towards perforated distribution plate 50. Collector 68 is closed at its upper end by a perforated plate 70.

In this arrangement, water circulation is set up 5 by natural convection inside tubes 64 towards collector 68 and then upwards through perforated plate 70.

In the event of a vapour explosion, tubes 64, collar 66 and perforatedplate 70 fill functions similar to those previously described with reference in particular to figures 2 and 4.

Evidently, the different embodiments and variants just described only form possible examples of embodiment of deformable inner structures 38 placed inside receptacle 20. It is recalled that, more generally, the invention applies indifferently to any type of water nuclear reactor, irrespective of the arrangement of the core and associated inner equipment. Also, the shape and structure of the receptacle may differ from those described. Furthermore, even if space 22, and ring collector 34 are desirable, their presence may, in some cases, be omitted.

Claims

I. Water nuclear reactor comprising a vessel and a reactor core housed in the vessel, said reactor also comprising a basin-shaped receptacle housed in the vessel below the core and made at least in part of refractory material, said receptacle being able to collect corium formed during accidental fusion of. the core and containing deformable inner structures at least in the proximity of an inner surface of the receptacle.
2. Reactor according to Claim 1 or 2, in which the deformable inner structures comprise metallic structures arranged such as to allow circulation of water in said structures.
3. Reactor according to claim 1, in which the receptacle also contains containers in which is placed a material able to lower the temperature of the corium when in contact with the latter.
4. Reactor according to claim 3, in which the material able to lower the temperature of the corium contains silica.
5. Reactor according to Claim 3 or 4, in which the containers are spheres.
6- Reactor according to any preceding claim, in which the deformable inner structures comprise a lattice-work of crossed bars, arranged against the inner surface of the receptacle.

21
7. Reactor according to claim 6, in which the lattice-work of crossed bars fills the most part of the receptacle.
8. Reactor according to claim 7, in which said 5 containers are housed in between the crossed bars.
9. Reactor according to claim 6, in which the deformable inner structures also comprise, inside the lattice-work of crossed bars, a structure of perforated metal sheets forming compartments, said containers being housed at least in the compartments closesf to the lattice-work of crossed bars.
10. Reactor according to any of Claims 1 - 5, in which the deformable inner structures comprise metal sheets, spaced out from one another and arranged substantially parallel to the inner surface of the receptacle, and counter-braces connecting the metal sheets together.
11. Reactor according to claim 10, in which the metal sheets and counterbraces form modules containing tubes oriented substantially parallel to the inner surface of the receptacle.
12. Reactor according to claim 11, in which the containers are tubes.
13. Reactor according to any of Claims 1 - 5, in which the deformable inner structures comprise a honeycomb structure whose partitions are substantially perpendicular to the inner surface of the receptacle.
14. Reactor according to claim 13, in which the containers are alveoli demarcated by the honeycomb structure.
15. Reactor according to any of Claims 1 - 5, in which the deformable inner structures comprise tubes arranged in 22 successive layers substantially parallel to the inner surface of the receptacle and leading to a central collector housed in the bottom of the receptacle.
16. Reactor according to any preceding claim, in which a perforated distribution plate overhangs the receptacle.
17. Reactor according to claim 16, in which the perforated distribution plate is cone-shaped, the tip of the cone being directed downwards.
18. Reactor according to any preceding claim, in which.the receptacle is separated from the bottom of the vessel by a space which opens upwards.
19. Reactor substantially as hereinbefore described with reference to any one of the accompanying drawings.