EP0173606A1 - Thermal seal surveillance systems for a container enclosing a thermogenic material - Google Patents

Abstract

According to the invention, the monitoring device comprises one or more seals (2), affixed to a surface element (4) of a container, comprising several resistive components (6) electrically connected to each other and enclosed in a structure (8 ) comprising a first material (14b) serving as physical protection and a second material (16b) serving as thermal insulation, this seal (2) being capable of providing an electrical signal representative of the heat flux exchanged between the surface element (4 ) and said seal (2).

Description

The subject of the present invention is devices for monitoring by thermal seal of a container containing in particular calogenic material making it possible to detect any time an attempted break-in of the container and / or the material contained therein, or a theft, even if the thief succeeds in putting the surveillance device back in place.

It applies in particular to the monitoring of a large number of containers (400 to 500 containers for example), fixed or mobile, containing radioactive caLogenic material, regardless of the thermal environment of said container.

In this case, the container containing the heat-generating material comprises parts which, as a result of heat exchanges, have temperatures different from ambient temperature.

There are currently a number of monitoring devices for detecting an attempt to open a container. One of these devices consists in fixing the ends of a cable passing through the toggle or the gills of closure of a container to a housing in which a mass of resin has been poured which has cracked on cooling. These cracks form a definite pattern that we photograph at the start. When someone succeeds in opening and then closing the case, the mass of resin contained in it may move and / or new cracks may appear. A new photograph of The Resin allows us to observe these changes.

However, nothing can be detected in case the thief does not touch the case and Take the precaution of cutting only the cable and then reconstituting it by splicing. In addition, since the monitoring of such a device requires a physical presence, it does not allow continuous monitoring of the containers. In addition, in the case of radioactive materials, this device involves an undesirable exposure of surveillance personnel to the radiation emitted by said materials.

There are also known surveillance devices allowing continuous or real-time monitoring such as those described in document EP-A-0018 198. These devices using optical seals do not make it possible to distinguish between heat-generating materials or not. In addition, they do not detect an intrusion into the container that would leave the seals intact.

The object of the present invention is precisely to inviolable monitoring devices for a container, containing in particular calogenic material, making it possible to remedy these drawbacks and making it possible to detect any attempted break-in and / or theft, and this , regardless of where it was made. It is based on the fact that any modification on the container or its contents disturbs the thermal state of the surface of said container on which the sealing device is attached.

By container, it is necessary to understand any closed enclosure and in particular a room.

The use of thermal sensors associated with a data acquisition system is known and in particular described in the article by H. DUANE ARLOWE, NucLear Materials Management 1982, pages 82 to 88, entitled "A Low cost SNM shelf monitor system" , for Detecting the presence of a container on a base and verification of its heat content. But the latter device allows more qualitative than quantitative measurements on the one hand, and on the other hand does not constitute a sealing device.

The present invention specifically relates to a device for monitoring a container containing in particular heat-generating material, intended to control the presence and the integrity of the container, characterized in that it comprises at least one seal, affixed to a container surface element, comprising at least one resistive component enclosed in a structure serving as physical protection and thermal insulation, this seal being capable of providing an electrical signal representative of the heat flux exchanged between the surface element and said seal and / or the heat flux exchanged between the environment of the seal and itself, and monitoring means sensitive to said signal and located at a distance from the container.

The use of a seal, providing an electrical signal representative of the heat flux exchanged with the surface element on LequeL it is arranged and / or the heat flux exchanged with its environment, makes it possible to detect any variation of this heat flux from a modification of the electrical signal emitted by The seal. Variations in heat flow can be due to a change in the environment of the sealed container (movement of the latter or neighboring containers), a change in the geometry of the seal (change, movement of it), a change particularly heat-generating content, to the presence or intervention of various means (person, robot) on any part of the container.

According to a preferred embodiment of the sealing device of the invention, the structure of the seal or in other words its envelope is made of a single material serving both physical protection and thermal insulation.

According to another preferred embodiment of the sealing device of the invention, said structure is made of two different materials, one serving as physical protection and the other as thermal insulation.

According to another preferred embodiment of the device of the invention, the seal comprises two independent series of resistive components electrically connected to each other, one of the series serving to take into account the variations in the heat flux exchanged between the seal and the surface. the container on which it is affixed, the other series being used to take into account the variations in the heat flow exchanged between the seal and its environment.

Advantageously, one of the series of resistive components of the seal is placed either near the face of the seal which is applied to the surface element of the container, or directly in contact with said surface element on which the seal is affixed. . This arrangement makes it possible to best capture the variation of the heat flux at the level of the surface element on which the seal is affixed. The variation can be caused by a modification of the environment, the geometry of the seal or the possibly calogenic content.

Preferably, the device of the invention comprises several seals providing different electrical signals, these signals being a function of the heat flux exchanged between the surface element and the corresponding affixed seal as well as the electrical characteristics of the resistive components constituting each seal.

The monitoring device according to the invention, in addition to the advantages given above, makes it possible, in the case of a container containing heat-generating material, to also monitor the content of the container.

• - La figure 1 représente schématiquement un dispositif de surveillance, conformément à l'invention, comportant des sceaux thermiques d'un premier mode de réalisation,
• - La figure 2 représente schématiquement un sceau thermique, conformément à L'invention, d'un deuxième mode de réalisation dans LequeL Le matériau servant d'isolation thermique est situé vers L'extérieur,
• - La figure 3 représente schématiquement un sceau thermique, conformément à L'invention, du deuxième mode de réalisation dans LequeL Le matériau servant de protection physique est situé vers L'extérieur,
• - La figure 4 représente schématiquement un sceau thermique, conformément à l'invention, d'un troisième mode de réalisation,
• - La figure 5 représente schématiquement un mode de réalisation du circuit électronique du dispositif de surveillance, selon l'invention, et
• - les figures 6 à 9 illustrent différents exemples de fixation des sceaux thermiques, conformément à l'invention, sur un conteneur à surveiller.

Other characteristics and advantages of the invention will emerge more clearly from the description which follows, given by way of illustration and not limitation, with reference to the appended figures, in which:

• FIG. 1 diagrammatically represents a monitoring device, in accordance with the invention, comprising thermal seals of a first embodiment,
• FIG. 2 schematically represents a thermal seal, in accordance with the invention, of a second embodiment in LequeL The material serving as thermal insulation is located towards the outside,
• FIG. 3 schematically represents a thermal seal, in accordance with the invention, of the second embodiment in LequeL The material serving as physical protection is located towards the outside,
• FIG. 4 schematically represents a thermal seal, according to the invention, of a third embodiment,
• FIG. 5 schematically represents an embodiment of the electronic circuit of the monitoring device according to the invention, and
• - Figures 6 to 9 illustrate different examples of fixing the thermal seals, according to the invention, on a container to be monitored.

In Figure 1, there is shown a monitoring device according to the invention.

This device comprises one or more seals 2 which are affixed to a surface element 4 of a container containing in particular calogenic material, consisting for example of irradiated or non-irradiated materials or radioactive waste. Each seal is a thermal flux meter providing an electrical signal representative of the heat flux exchanged between itself and the surface element 4 on which it is affixed. It comprises one or more resistive elements or components, connected together in series and / or in parallel, enclosed in a structure 8 or envelope serving as physical protection and thermal insulation, these components being supplied by a direct or alternating current.

The resistive components 6 can be resistors with a positive or negative temperature coefficient. They are advantageously placed as close as possible to the face 10 of the seal 2 which is applied to the surface element 4 of the container to be monitored (FIG. 3). In particular, these components can be arranged so that they come into direct contact with the surface to be monitored, as shown in FIG. 1.

The structure 8 serving as physical protection and thermal insulation may consist of a single material 12 fulfilling both the two functions of physical protection and thermal insulation. This material can for example consist of an insulator such as an epoxy resin. In such an embodiment, the fixing of the seal 2 on the surface element 4 of the container can be ensured by gluing.

The structure 8 of the seal 2 can also be made, as shown in FIGS. 2 and 3, of two different materials, one having a role of physical protection and the other of thermal insulation.

In FIG. 2, the material playing the role of physical protection bears the reference 14a and the material playing the role of thermal insulator the reference 16a. The material 14a can for example be formed of a metal cover, in particular of stainless steel, and The material 16a of polyurethane foam.

In the variant shown in FIG. 2, the material 14a playing the role of physical protection (metal cover), is arranged so as to wrap the resistive components 6, The material 16a playing the role of thermal insulator covering the material 14a. An air vacuum 17, between the material 14a and the resistive components 6, can be provided, in particular when this material 14a is metallic. In this variant, the fixing of the seal 2 on the surface element 4 of the container can be ensured by gluing.

Furthermore, the resistive components 6 can be arranged directly in contact with the surface element 4 of the container to be monitored.

In FIG. 3, the material playing the role of physical protection bears the reference 14b and the material playing the role of thermal insulator the reference 16b. The material 14b can for example consist of a metal cover, in particular stainless steel, and The material 16b, of polyurethane foam or a gas such as air.

In the variant shown in Figure 3, the resistive components 6 are completely embedded in the material 16b, thermally insulating, the latter being covered with the protective material 14b; they have no contact with the surface element 4 of the container to be monitored, but are arranged near said element. In this variant, the fixing of the seal 2 on the surface element 4 of the container can be ensured, by gluing, welding, brazing, etc.

The affixing of a seal 2, as shown in FIGS. 1 to 3, on a surface element 4 of a container automatically results in the appearance of a natural thermal gradient of the surface element on which it is affixed; The seal then emits an electrical signal which is representative of the heat flux exchanged between the surface element 4 and itself; this electrical signal is a function of the heat flux exchanged and of the electrical characteristics of the resistive components 6 constituting the seal.

In the case of a container containing non-calogenic material, the resistive components 6 of a seal are supplied with a current sufficient to cause a detectable self-heating of these components. The seal is said to be active.

This electrical signal carried by a cable 18, as shown in FIG. 1, can be detected and then analyzed using an appropriate electronic circuit 20, which will be described later, located at a distance from the container to be monitored.

In Figure 4, there is shown another embodiment of a thermal seal, according to the invention, said quantitative. In this embodiment, the seal 2 comprises two independent series 6a and 6b of resistive components, enclosed in the structure 8. In each series, the electrical components are electrically connected together.

One of the series 6a is arranged, as before, either near the face 10 of the seal 2 which is applied to the surface element 4 of the container (FIG. 3) or in direct contact with the surface to be monitored. It allows, as previously, to provide an electrical signal representative of the heat flux exchanged between the seal 2 and the surface element 4 of the container on which the seal is affixed.

The other series 6b is arranged near the face 21 of the seal 2 opposite to the face 10 of the latter. It provides an electrical signal representative of the heat flux exchanged between the environment of the seal and itself.

In this embodiment, it is preferable, from a practical point of view, that the structure 8 of the seal 2 be made of two different materials, the material 14b playing the role of physical protection being situated towards the outside of the seal and The material 16b playing the role of thermal insulation being enclosed in the material 14b.

In the case of a container containing heat-generating material, it is possible to use a system equivalent to the seal of FIG. 4, consisting of two seals as shown in FIGS. 1 to 3; One of the two seals, called the first seal, provides an electrical signal representative of the heat flow exchanged between itself and the surface of the container on which the iL is affixed, and the second seal provides an electrical signal representative of the heat flow exchanged between it - itself and its environment. In this arrangement, the first seal is placed on a sealed surface of the container and the second seal in particular on a part at ambient temperature of said container.

According to the invention, the same seal 2 can be used "quantitatively" for the monitoring of a container containing calogenic material; then "actively" When this material stops giving off Heat. In other words, the same seal can be used in two different ways depending on whether the content of the container is heat-generating or not.

In the case of the use of calibrated resistive components 6, the seals 2 constitute thermal flow meters able to assist in the quantitative monitoring and management, by means of an appropriate circuit, of the heat-generating materials enclosed in the container to be monitored.

If the heat-generating material to be monitored is well characterized, the measurement of the heat flux makes it possible to know the amount of material present. Otherwise, the measurement of the heat flux and the amount of material present are only correlated.

The use of resistive components whose electrical characteristics are unknown and which are drawn at random, during the constitution of the seals 2, makes it possible to obtain seals having random electrical characteristics. Automatic monitoring of the signal emitted by each random seal 2, by means of an electronic circuit 20, means that these characteristics may remain absolutely unknown, even for the surveillance personnel, and therefore not dupLicabLes.

Furthermore, the use of an appropriate circuit 20 allowing the acquisition and management of the electrical signals transmitted by the seals 2 allows. to constitute an inviolable security device. In particular, a circuit 20 allowing interrogation of each seal 2 continuously, for example every milliseconds, does not make it possible to have a time long enough to carry out a malicious intervention.

In addition, the acquisition and analysis system 20 can be such as to keep track of any particularly malicious intervention on the containers to be monitored.

As the electronic circuit 20 used for the detection of the electrical signals supplied by the thermal seal (s), it is possible in particular to use the circuit shown diagrammatically in FIG. 5.

• - un générateur de courant 30, stabilisé en courant servant à alimenter Les composants résistifs 6,
• - un voltmètre digital 32 enregistrant Les signaux électriques analogiques délivrés par Les composants 6 et Les transformant en données numériques,
• - un calculateur 34 traitant Les signaux issus du voltmètre, tels que comparaison de signaux fournis par Les sceaux apposés sur un même conteneur,
• - des moyens d'enregistrement 36 (sur support papier ou magnétique) des résultats pilotés par Le calcuta- teur 34,
• - des moyens de visualisation 38 de ces mêmes résultats, pilotés aussi par Le calculateur 34, et
• - une éventuelle alarme 40 pilotée encore par Le caLculateur et émettant un signal Lumineux ou sonore, en cas de modification brusque des signaux électriques fournis par Les sceaux thermiques, cette alarme pouvant se trouver à proximité du calculateur et/ou des moyens de visualisation et d'enregistrement, ou bien à distance (plusieurs kilomètres).

This circuit 20 essentially comprises.

• a current generator 30, stabilized in current used to supply the resistive components 6,
• - a digital voltmeter 32 recording the analog electrical signals delivered by the components 6 and transforming them into digital data,
• a computer 34 processing the signals from the voltmeter, such as comparison of signals supplied by the seals affixed on the same container,
• means of recording 36 (on paper or magnetic medium) of the results controlled by the computer 34,
• display means 38 for these same results, also controlled by the computer 34, and
• - a possible alarm 40 still controlled by the computer and emitting a light or sound signal, in the event of an abrupt change in the electrical signals supplied by the thermal seals, this alarm may be located near the computer and / or display and display means. 'recording, or at a distance (several kilometers).

In order to allow continuous interrogation of a large number of seals 2, a channel scanner 42 connected to the restrictive components 6 and to the computer must be provided.

In Figures 6 to 9, there are shown different types of seal arrangements according to the invention. These arrangements are formed by several seals 2 which can be mechanically connected together, for example using metal wires 22 (steel). These seals 2 can for example be affixed, as shown in FIGS. 6 to 8, on the contact area 24 between the cover 26 of the container and the body 28 of the latter, or, as shown in FIG. 7, affixed near this contact area 24, for example on the cover 26 or on the body 28 itself of the container.

In the case of a container containing heat-generating radioactive material, the seals will be avan taggedly affixed outside the contact zone 24 of the lid and of the container body (FIG. 7) in order to allow, for service reasons, to open and then close the container, the seals detecting this intervention and the possible modification of the content from the container without being destroyed.

In the case of a container containing non-calogenic material, it is preferable to use a large number of seals, as shown in FIG. 8, in order to detect any intrusion (introduction of a tool for example) into the container , these seals being advantageously affixed to the contact area of the cover and of the conductive body.

Of course, these different arrangements of seals are given only by way of example.

Claims (10)

1. Device for monitoring a container containing material, intended to control its presence and its integrity, characterized in that it comprises at least one seal (2), affixed to a surface element (4) of the container, comprising at least one resistive component (6, 6a, 6b) enclosed in a structure (8) serving as physical protection and thermal insulation, this seal (2) being capable of providing an electrical signal representative of the heat flux exchanged between the surface element (4) and said seal (2) and / or of the heat flow exchanged between the environment of the seal (2) and itself and monitoring means (20) sensitive to said signal and located at a distance from the container. 2. Monitoring device according to claim 1, characterized in that the seal comprises two series (6a, 6b) independent of resistive components electrically connected to each other, one of the series (6a) serving to supply an electrical signal representative of the flow heat exchanged between the surface element (4) and said seal (2), the other series (6b) used to provide an electrical signal representative of the heat flow exchanged between the environment of the seal and itself. 3. Monitoring device according to claim 2, characterized in that the resistive components of each series are interconnected in series and / or in parallel. 4. Monitoring device according to any one of claims 1 to 3, characterized in that The structure (8) consists of a single material (12) serving both for physical protection and for thermal insulation. 5. Monitoring device according to any one of claims 1 to 3, characterized in that that the structure (8) consists of two different materials, one serving as physical protection (14a, 14b), the other as thermal insulation (16a, 16b). 6. Monitoring device according to any one of claims 2 to 5, characterized in that one of the series of resistive components (6) is placed near the face (10) of the seal (2) which is applied to the surface element (4) of the container. 7. Monitoring device according to any one of claims 2 to 5, characterized in that one of the series of resistive components (6) is placed directly in contact with the surface element (4) on which the seal is affixed. 8. Monitoring device according to any one of claims 1 to 7, characterized in that the resistive component (6) is calibrated and able to assist in the quantitative management of heat-generating materials. 9. Monitoring device according to any one of claims 1 to 7, characterized in that the resistive component (6) is drawn at random, so that its electrical characteristics are unknown. 10. Monitoring device according to any one of claims 1 to 9, characterized in that it comprises several seals (2) providing different electrical signals.

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