FR2790588A1 - Container wall structure with pierce-resistant shielding for transporting hazardous materials, has metal and textile layers incorporating netting or chain mail - Google Patents

Abstract

The wall structure is made from a number of layers: an inner layer (1) of a material with a high mechanical resistance, e.g. steel; a thick deformable layer (2) with a high energy absorbing capacity and optional high thermal conductivity; an intermediate layer (3) of metal; a textile layer (4) and an outer metal layer (5). The wall structure is made from a number of layers: an inner layer (1) of a material with a high mechanical resistance, e.g. steel; a thick deformable layer (2) with a high energy absorbing capacity and optional high thermal conductivity; an intermediate layer (3) of metal; a textile layer (4) and an outer metal layer (5). The deformable layer is made from syntactic foam, porous or non-compact concrete, porous clay or wood. The textile layer is a multiple layer of braided, woven, knitted and mesh material with high elasticity and specific resistance, and can incorporate chain mail made from interwoven stainless steel rings; it also has spacers (6) lying perpendicular to its layer and connecting the intermediate and outer metal layers.

Description

WALL STRUCTURE FOR CONTAINER

WITH ANTI-PUNCH SHIELD

DESCRIPTION

  Field of the Invention The invention relates to the field of containers, and in particular containers which are to transport dangerous materials or which could be described as "difficult". These are, in fact, nuclear materials, chemically hazardous or toxic materials, or materials expected to emit

a large amount of heat.

  Prior art and problem posed The containers conventionally defined for the transport of radioactive materials, such as, for example, the fissile assemblies removed from the reactors, consist of an enclosure, generally cylindrical, the wall of which is formed by several successive layers having functions separate techniques. This cylindrical enclosure is closed at one end by a fixed plug and at the other end by a movable plug, used for placing

place or remove content.

  To be approved, nuclear material transport containers are subjected to various qualification tests, such as falls, fires, punching. The development of the qualification standards for these containers has the practical consequence of oversizing certain layers of the structure to satisfy, for example, the punching test, that is to say "the punch". This consequence obviously leads to an increase in the mass of the container, which

  constitutes a handicap for the latter.

  The resistance to the various stresses is taken into account by the resistance of these distinct layers for which several technical and physical characteristics intervene which are as follows: the geometry; - the mass of the elements used; - the mechanical characteristics of the materials used, for example, the elastic modulus, the elastic limit (in static and dynamic stresses), the density; - the thermal characteristics of the materials used, for example, the specific heat,

  thermal conductivity, density.

  The layers have a specific function vis-à-vis the forces imposed on the entire container and are conventionally made of steel. Others have a more specific role, such as, for example, the absorption of radiation emitted by the contents or fire resistance. Another characteristic common to certain containers is to allow good evacuation of the thermal energy emitted by the content. A known type of embodiment consists in providing, through an insulating layer, a large number of rods or blades arranged radially, that is to say perpendicular to the successive layers, and characterized by a strong

  thermal conductivity (steel, aluminum, copper, ...).

  Concerning the punching test, the specificity of the punching stress comes from the localized nature of the aggression of the punch vis-à-vis the wall of the container. The punch test is carried out, depending on the mass of the container, by the fall of a punch on the stationary container or by the fall of the container on a fixed punch, without

  this changes the mechanism of the aggression of the wall.

  When the masses brought into play increase, the perforation threshold of the wall and in particular of the successive layers, which are not necessarily all designed for this aggression, is exceeded. The dimensioning of the resistant layer (s) with respect to the stress due to the punching action currently consists in determining the thickness and the mechanical characteristics of the steel which lead to non-perforation. of this (these) layer (s), in order to maintain the tightness and integrity of the following internal layers. The high level of stress on the punch leads to a crippling oversizing of the layer (s) intended for this function. This results in an increase in mass, which in turn increases the kinetic energy of the container, which can ultimately lead to a technical impasse. The object of the invention is to remedy these drawbacks by proposing a new type of wall structure for the containers, as described above. Summary of the invention For this purpose, the main object of the invention is a container structure with anti-punching armor, for the transport of toxic, radioactive or "difficult" materials, comprising five successive adjacent layers which are: - a rigid middle layer slightly deformable perpendicular to the plane of this middle layer; - a textile layer to absorb mechanical attacks perpendicular to the layer; and a rigid outer layer whose

  mechanical strength is not critical.

  With these three layers, this structure can be added to existing containers to improve their resistance to punching aggression. In the context of an application to containers intended for transporting or containing nuclear materials, it is supplemented with additional layers which are: - a rigid internal layer with high mechanical resistance; and - a deformable layer absorbing the

  shock and pressed against the middle layer.

  The structure is very advantageously completed by spacers placed in the textile layer, perpendicular thereto, and joining the outer layer and the middle layer by a final fixing with the latter, holding the textile layer in place and evacuating, if necessary. , the thermal energy released by the container of the container. In its preferred embodiment, the internal layer is made of a material which is a very good conductor of thermal energy, with the aim of removing the large amount of calories, possibly contained or released by the contents of the container. She is from

preferably steel.

  In its preferred embodiment, the deformable layer is thick, has a large capacity for absorbing energy perpendicular to this deformable layer, and is possibly good.

conductive of heat.

  It is preferably made of syntactic foam, porous or non-compact concrete, clay

porous, or wooden.

  In its preferred embodiment, the

middle layer is metallic.

  In its preferred embodiment, the dry textile layer is of the dry textile type and formed of several successive layers, each consisting of braid or fabric or knitted or mesh. Each layer has a high elasticity and a high specific resistance in the plane of the textile layer. Preferably, the different layers

  successive layers of the textile layer are not stretched.

  In its preferred embodiment, the

outer layer is metallic.

  List of Figures The invention and its various technical characteristics will be better understood on

  reading of the following description, accompanied by

  several figures representing respectively: - Figure 1, in section, the structure according to the invention, during a punching test; - Figures 2A and 2B, two detailed views of a first embodiment of the textile layer of the structure according to the invention before and after the impact of a punch; and - Figures 3A to 3D, detailed views of a second embodiment of the textile layer of the structure according to the invention during the action of a punch.

  Detailed description of a realization of

  the invention FIG. 1 therefore shows, in section, the wall structure according to the invention in an application to a container intended for transporting or storing nuclear materials, during a punching test. An element of the wall is shown horizontal, kept fixed under a punch 7. It mainly consists of five layers, the stacking of which can follow the particular shape of

the object to be protected.

  The first layer is an internal layer with high mechanical resistance 1, formed of a thick sheet of steel constituting the internal shell of the container. The second layer 2 is made of a material deformable in compression, that is to say in a direction perpendicular to that of the layers, that is to say parallel to the direction of vertical movement of the punch 7. This material must also have a quality of compression deformation to be able to absorb possible deformations of the layers attacked by the punch 7. It is thus possible to use syntactic foam, porous clay, non-compact concrete and others

  materials with the same qualities, such as wood.

  This deformable layer 2 is supported on the layer

internal 1.

  The third layer, referenced 3, is the

  middle layer, adjacent to the deformable layer 2.

  It is a layer of high mechanical resistance which performs an important function in the general structure of holding the container. It constitutes the internal skin of the entire structure of the wall which is a sandwich structure. Preferably, it is metallic, but may possibly be made of composite material. It must be deformable in the direction perpendicular to itself, that is to say parallel to the movement of the punch 7, to accompany the end of the movement of the punch, during the

punching test.

  The fourth layer, referenced 4, is a textile layer. More precisely, it consists of a succession of several layers of a textile, arranged parallel to each other. The textile used can be a fabric, braid, net or knitted fabric. Its qualities must be a high initial elasticity and the greatest energy of permanent deformation in the plane of the tissue expressed in kJ / kg. This great elasticity is provided, not only to accompany in its course the shine 8 torn from the outer layer 5, but to slow it down and contribute to its stopping. For this purpose, the various textiles which can be used to constitute this textile layer 4 must be slightly extensible in the plane of the fabric. For this purpose, one can play on the nature of the fiber of the material used and on the shape of the weaving of the textile. In FIG. 1, it can be seen that several successive layers of textile are crushed or lowered by the punch 7. The

  raw materials can even be severed if necessary.

  These which are cut remain under the shine 8 and contribute, by their very high specific resistance in the plane of the tissue, to slow or stop the

hallmark 7.

  The different successive layers of the textile layer 4 are held in place by means of spacers 6 placed perpendicular to these different layers and connecting the middle layer 3 to an external layer 5 by permanent fixings,

such as solders.

  FIG. 2A shows one of the successive layers of a net embodiment of the textile layer held in place by a row of spacers 6. It can be seen that transverse strands 41 are not stretched, as are longitudinal strands 42 This is due to the fact that the textile must match, by its different transverse 41 and longitudinal 42 strands, the shape and location of the spacers 6. Each successive layer of the textile layer 4 is therefore simply placed around the spacers 6, way no

tense, without constraints.

  Figure 2B shows the behavior

  of the same layer of fabric after the impact of the punch.

  We note that some transverse strands 41 are broken, especially on the right, near the impact of the

  punch, where the stretch of each strand is maximum.

  Some longitudinal strands 42 can also be broken at this location. The mesh or weaving of the textile layer being flexible, can therefore adapt to the general stretching of the layer towards the impact of the punch, while being maintained by the spacers 6. It is thus understood that the elastic deformation, then plastic of each successive layer of the textile layer 4 in its plane can be used to cushion and possibly stop the

punch in its course.

  FIGS. 3A to 3B show the evolution of a longitudinal strand 43 of fabric in another embodiment of the textile layer, during the intervention of a punch. The latter acts on the textile on the right of the figure. This has the consequence that one of the wires receiving the punch, or close to it, is stretched to the right and that its

  thickness tends to decrease.

  FIGS. 3C and 3D show the end of this evolution of the longitudinal strand 43, that is to say its thinning and its tendency to apply against successive struts 6. In its terminal phase, that is to say in FIG. 3D, the strand 43 is completely stretched. The elasticity, then the plastic deformation capacity of each longitudinal strand 43

are thus exploited to the maximum.

  It is also planned to use a metallic textile, made of stainless steel or not, used alone or in combination with an organic fiber textile. It is also possible to play on the different weaves of the textiles chosen to constitute this textile layer 4 (weaving, net, etc.). It is understood that the spacers 6, retaining the different successive layers of the textile layer 4 provide energy greater than that of different successive layers stacked without spacers. In addition, by fixing each mesh of the weaving by the spacers 6, the transverse deformation of each successive layer of the textile layer 4 is controlled and maximum use is made

  the deformation energy of this textile.

  Another important function of the spacers 6 is to evacuate the thermal energy released by the container, when the latter consists, for example, of nuclear waste. For this purpose, they are made of steel, copper or some other very material

good conductor of heat.

  The last layer, namely the outer layer 5, is in the form of a steel sheet or possibly a composite material. This outer layer 5 receives the punch 7 first, and is therefore dedicated to being sacrificed, upon the impact of the punch 7. The punch effect is more or less pronounced depending on the elastoplastic response of the material constituting this outer layer 5. It is specified that the latter can also constitute the surface

visible from the container.

  The particular constitution of the different layers and in particular of the textile layer 4 makes it possible to make these layers work in a non-localized manner, but on the contrary over a larger possible surface, without complete rupture of the whole of the wall structure. Indeed, the stress perpendicular to the wall formed by the impact of the punch 7 is transformed into tangential stress, that is to say parallel to the successive layers, in particular in the textile layer 4. In addition, the transverse deformation of the the entire wall is accompanied by an amount of energy absorption

maximum mechanical.

  Although the deformation of the impacted area is different, the operating principle described remains valid when the punch attacks the wall under

an angle different from normal.

  This description relates to a

  wall structure with an inner layer and a deformable layer for a particular application. It is intended not to use these two layers for other applications. It is thus possible to equip existing containers, in order to improve

  specifically resistance to punching aggression.

Claims (12)

RESELL I CAT I ONS   1. Container wall structure with anti-punching shield, for the transport of difficult, toxic, dangerous or radioactive materials, comprising several adjacent successive layers, which are respectively: - a rigid or slightly deformable middle layer (3) perpendicular to the plane of this middle layer (3); - a textile layer (4) to absorb attacks perpendicular to this textile layer (4); and - a rigid outer layer (5), the   mechanical strength is not critical.   2. Wall structure according to claim 1, characterized in that it comprises two other layers which are successively: - an internal layer (1) rigid with high mechanical resistance; and - a deformable layer (2) absorbing shocks perpendicular to the plane of this layer   deformable (2) and pressed against the middle layer (2).   3. Wall structure according to claim 1, characterized in that it comprises spacers (6) placed in the textile layer (4), perpendicular thereto and securing the outer layer (5) to the middle layer (3 ) by a definitive fixing with these, to maintain in position the textile layer (4) and to evacuate, if necessary, the thermal energy released by the container of the container. 4. Wall structure according to claim 2, characterized in that the internal layer (1) is made of a material which is a good thermal conductor. 5. Wall structure according to claim 4, characterized in that the layer internal (1) is made of steel.   6. Wall structure according to claim 2, characterized in that the deformable layer (2) is thick, of high energy absorption capacity, and possibly good thermal conductor.   7. Wall structure according to claim 6, characterized in that the deformable layer (2) is made of a material included in the group comprising syntactic foams, concretes   porous or non-compact, porous clays, wood.   8. Wall structure according to claim 1, characterized in that the layer middle (3) is metallic.   9. Wall structure according to claim 1, characterized in that the textile layer (4) is of the "dry textile" type, composed of several successive layers of a material included in the group of braids, fabrics, knits, nets and having high elasticity and high specific resistance in the plane of the textile layer (4).   10. Wall structure according to claim 9, characterized in that the successive layers of the textile layer (4) are not stretched. 11. Wall structure according to claim 1, characterized in that the layer external (5) is metallic.   12. Wall structure according to claim 1, intended to be attached to an existing container to improve the resistance to punching assault.