WO2020193901A1

WO2020193901A1 - Assembly comprising a packaging for the storage of radioactive materials and support system thereof

Info

Publication number: WO2020193901A1
Application number: PCT/FR2020/050516
Authority: WO
Inventors: Olivier Bardon
Original assignee: Tn International
Priority date: 2019-03-28
Filing date: 2020-03-12
Publication date: 2020-10-01
Also published as: FR3094549A1; EP3928330B1; FR3094549B1; KR20210141967A; EP3928330A1

Abstract

The invention relates to an assembly (100) comprising a packaging (1) for storage of radioactive materials, as well as the support system (3) thereof, comprising a radiative screen (20) for thermal protection of the ground, this screen comprising at least one air passage (24) providing the communication between a zone (32) for circulation of air for cooling the ground defined under a first face (28) of the screen, and a zone (34) for circulation of air for cooling the bottom of the packaging defined between the second face (30) of the screen and the bottom of the packaging (4). The support system (3) comprises elements (36) for supporting the bottom of the packaging, each projecting from the second face (30) of the radiative screen (20) and extending through the zone (34), and it also comprises bearing elements (38) projecting into the zone (32).

Description

DESCRIPTION

TITLE: SET INCLUDING A PACKAGING FOR THE STORAGE OF RADIOACTIVE MATERIALS, AND ITS SUPPORT SYSTEM

TECHNICAL AREA

The present invention relates to the field of storage packaging for radioactive materials, for example radioactive waste placed in drums, or even nuclear fuel assemblies.

The invention relates more particularly to an assembly formed by such a packaging with its support system, the latter providing the interface between the packaging bottom in the vertical storage position, and the floor of the storage site.

STATE OF THE PRIOR ART

Usually, packages are stored in an upright position in a storage site, also referred to as a hall or storage building. These packages are generally placed directly on the floor in the storage building, involving direct contact between the bottom of the package and the floor. As a result, the part of the soil facing the bottom of the package can reach high temperatures, which may exceed the average and maximum tolerated soil temperatures.

DISCLOSURE OF THE INVENTION

To lower the average and maximum temperatures of the ground vis-à-vis a package, the invention relates to an assembly comprising a storage package for radioactive materials as well as a support system for the packaging intended, in a packaging storage configuration, to be arranged between a bottom of the packaging and a floor of a storage building.

According to the invention, the support system comprises a radiative screen for thermal protection of the ground having a first lower face as well as a second upper face opposite the first, the radiative screen comprising a central part provided with at least one passage. air ensuring communication between a zone of circulation of ground cooling air defined under the first face of the radiative screen, and a zone of circulation of cooling air for the bottom of the packaging defined between the second face of the radiative screen and the bottom of the packaging .

Additionally, the support system further comprises a plurality of spaced apart package bottom support members, each support member projecting from the second face of the radiative screen and extending through the cooling air circulation zone of the bottom of the packaging until contact with the latter.

Finally, the support system also comprises a plurality of support elements protruding into the cooling air circulation zone of the ground, from the first face of the radiative screen.

The invention thus makes it possible to reduce the average and maximum temperatures of the part of the ground located opposite the whole, first of all thanks to the support system whose radiative screen limits the radiation of the wrapping towards the ground. In addition to forming a screen against this radiation, the support system makes it possible to cool the ground thanks to an air suction within the zone of circulation of cooling air of the ground defined under the first face of the radiative screen. , this suction being operated radially from the outside to the inside until this air passes through the central air passage (s), then it is discharged by the cooling air circulation zone at the bottom packing.

In other words, the invention provides in a simple manner to combine the effects of heat shield and cooling by natural convection, to limit the rise in temperature of the ground and of the bottom of the package.

The invention can provide for the implementation of one of the following optional characteristics, taken individually or in combination.

The central part of the radiative screen, in which each air passage is circumscribed, has a first diameter DI smaller than the largest transverse dimension D2 of the packaging, so as to correspond to the following relationship: DI <0, 5. D2 This sizing further improves the cooling efficiency of the bottom of the package and the floor, by combining the two effects of heat shielding and cooling by natural convection.

Said at least one air passage has a cumulative surface SI of air circulation, the packaging in storage configuration has a longitudinal central axis orthogonal to the ground and to the radiative screen and centered with respect to the latter, the packaging has a projected surface S2 on the ground, along the longitudinal central axis, and the surfaces SI and S2 correspond to the following relationship:

IF <0.25. S2

Here again, this dimensioning contributes to improving the cooling efficiency of the packaging bottom and of the floor, by combining the two effects of heat shielding and cooling by natural convection.

The supporting elements of the packaging bottom and the supporting elements form two by two of the feet passing through the radiative heat protection screen.

This advantageously results in simplicity of design. Each foot is then preferably produced in one piece, except possibly incorporating a thermal insulation layer at its end in contact with the packaging bottom. Alternatively, the support elements of the packaging bottom and the support elements could be produced by elements independent of each other, aligned or not aligned two by two in the direction of the longitudinal central axis of the packaging. in storage configuration.

In this storage configuration, the support system comprises an envelope carried at the periphery of the radiative screen, the envelope defining an air suction channel around the packaging.

This envelope promotes cooling by natural convection, and provides a chimney effect for the air coming from the cooling air circulation zone of the packaging bottom.

The support elements and / or the support elements are oriented radially or substantially radially with respect to the longitudinal central axis of the packaging on which the support system is also centered. This feature provides better circulation of fresh air towards the air passage (s), as well as better evacuation of heated air after the latter has passed through this / these passages. In other words, the particular orientation of the support and support elements limits the physical barriers generated by the presence of these elements, with respect to the flow of air within the support system.

The support elements and / or the support elements are arranged radially outwards with respect to the central part of the radiative screen.

This makes it possible to avoid direct thermal conduction between the central part of the packaging bottom, the hottest, and the ground, and limits the size of the central part of the radiative screen which includes the air passage (s). .

The radiative screen is equipped with a plurality of mechanical reinforcement elements interconnecting at least part of the bottom support elements and / or the support elements.

The mechanical reinforcement elements have radially inner ends connected to one another at a central connecting member around which are delimited radially inwardly several air passages, each of them also being delimited circumferentially by two reinforcing elements. directly consecutive mechanics.

Each mechanical reinforcement element is secured, at its radially outer end, to one of the support elements and / or to one of the base support elements. The assembly comprises hooking means allowing reversible hooking of the support system on the packaging, the hooking means preferably comprising fixing elements intended to cooperate with handling pins provided on the packaging.

This makes it possible to secure the packaging to the support system, so as to be able to move the assembly in the storage building when handling the packaging vertically, and thus avoid having to move the packaging separately. and the support system. Once the packaging is placed on the support system, the latter is then preferably hung on the pins of the packaging.

Each support element has an end in contact with the packaging bottom taking the form of a thermal insulation layer. This makes it possible to reduce the conduction of heat through the support elements in contact with the packaging bottom, and limits any damage caused to this packaging bottom by these same support elements.

Finally, the subject of the invention is a method for storing a package belonging to an assembly as described above, the method comprising placing the package in place on the support system arranged on the floor, so as to reveal the cooling air circulation zone of the packaging bottom.

Other advantages and characteristics of the invention will appear in the detailed non-limiting description below.

BRIEF DESCRIPTION OF THE DRAWINGS

This description will be made with reference to the accompanying drawings, among which;

[Fig. 1] represents a view in longitudinal axial section of an assembly according to a preferred embodiment of the present invention;

[Fig. 2] is a sectional view taken along the line II-II of Figure 1;

[Fig. 3] is a sectional view taken along the line III-III in Figure 1;

[Fig. 4] shows a view similar to that of Figure 1, with the assembly in the form of another preferred embodiment;

[Fig. 5] shows a top view of a radiative screen similar to that equipping the assembly shown in the preceding figures, but according to another embodiment;

[Fig. 6] shows a top view of a radiative screen, according to yet another embodiment;

[Fig. 7] shows a perspective view of a support system intended to equip the assembly shown in FIG. 4, but taking the form of another preferred embodiment of the invention;

[Fig. 8] is a perspective view of part of the support system shown in Figure 7;

[Fig. 9] is a bottom view of the support system shown in Figures 7 and 8; and [Fig. 10] shows a schematic view of a reversible mechanical connection between the packaging and its support system.

DETAILED PRESENTATION OF PREFERRED EMBODIMENTS

Referring firstly to Figures 1 to 3, there is shown an assembly 100 according to a preferred embodiment of the invention, this assembly comprising a package 1 for the storage of radioactive materials, and its support system 3 on floor 5 of a storage building 7.

The packaging 1 is shown in the vertical storage position, in which its longitudinal central axis 2 is oriented vertically, namely orthogonally to the ground 5. Conventionally, it comprises a packaging bottom 4 opposite to a removable cover 6 according to the direction of the height 8, parallel to the longitudinal central axis 2. In addition to the bottom 4 and the cover 6 spaced from each other along the axis 2, the packaging 1 comprises a lateral body 10 s' extending around this axis 2. The bottom 4 and the cover 6 axially define a housing cavity 12 within which the radioactive materials are received (not shown).

The assembly 100 also includes the support system 3 which, in the packaging storage configuration as shown in FIG. 1, is located between the bottom 4 of the packaging and the floor 5. This support system 3 may reside in a movable system placed on the ground 5, or, alternatively, in a system secured to the ground. The latter case turns out to be particularly advantageous for responding to seismic constraints.

The support system 3 comprises a radiative screen 20 serving for thermal protection of the ground 7. This screen 20 has the shape of a plate, of identical or homothetic geometry to that of the packaging bottom 4. Here, it is a question of of an overall form of a disc centered on the longitudinal central axis 2 of the packaging, this axis 2 also corresponding to the longitudinal central axis of the system 3 and of the assembly 100.

The screen 20 has a central part 22 centered on the axis 2, and of diameter DI smaller than an outside diameter D2 of the lateral packaging body. The ratio between the two diameters DI and D2 is preferably less than 0.5. The outer diameter D3 of the screen 20 is for its part greater than or equal to the outer diameter D2 of the lateral packaging body, the ratio between D3 and D2 preferably being between 1 and 1.3.

The previously mentioned central part 22 corresponds to the part of the screen 20 through which is made one or more air passages 24. In this preferred embodiment, there is provided a single air passage 24, of circular shape and centered on axis 2. This passage 24 has a diameter D4 generating a surface SI. Moreover, the projected surface S2 of the packaging on the ground 5, along the axis 2, is such that the ratio between the surfaces S1 and S2 is preferably less than 0.25. This projected surface S2 can also be considered as the projected surface of the packaging on the radiative screen 20, still along the axis 2, but without taking into account the opening formed by the air passage 24.

The screen 20 has a first lower face 28, as well as a second upper face 30 opposite the first face. The air passage 24 connects these two faces 28, 30. The first lower face 28 is located parallel to and at a distance from the ground 5, so as to define axially between them a zone 32 for circulating air for cooling the ground. Similarly, the second upper face 30 is located in parallel and at a distance from the packaging bottom 4, so as to define axially between them a zone 34 for circulation of cooling air for the packaging bottom. The air passage 24 thus ensures communication between the two zones 32, 34, each open radially outwards.

The support system 3 also comprises, in the zone 34, a plurality of support elements 36 of the packaging bottom, spaced from each other. These support elements 36 are for example provided four in number, even if a different number can be adopted, without departing from the scope of the invention. Further, each support member 36 protrudes vertically from second face 30 of screen 20, extending upwardly through area 34 until it contacts package bottom 4. As is best. visible in Figure 3, each support element 36 is oriented radially or substantially radially in relation to the axis 2, so as to better channel the air flow within the zone 34 of cooling air circulation of the packing background. In addition, these support elements 36 are arranged radially towards outside with respect to the central part 22 of the screen 20. At its upper contact end resting on the packaging bottom 4, each support element 36 can incorporate a thermal insulation layer so as to limit the direct heat transfer from the bottom 4 to the ground 7.

Similarly, the support system 3 comprises in the zone 32 a plurality of support elements 38 on the ground 5, spaced from each other. These support elements 38 are for example provided four in number, even if a different number can be adopted, without departing from the scope of the invention. In addition, each support element 38 protrudes vertically from the first face 28 of the screen 20, extending downwards through the zone 32 until it contacts the ground 5. The contact can be direct, or a thermal insulation layer can be interposed between the support elements and the ground. Alternatively, the support elements 38 can be connected to a plate at their lower end, which plate would then be in contact with the ground to further standardize the temperature. Indeed, this plate makes it possible to limit the risks of hot spots on the ground, vis-à-vis the support elements 38.

As best seen in Figure 2, each support element 38 is oriented radially or substantially radially in relation to the axis 2, so as to better channel the air flow within the zone 32 of circulation. ground cooling air. In addition, these support elements 38 are arranged radially outwardly relative to the central part 22 of the screen 20.

In this preferred embodiment, the support elements 36 and the support elements 38 are grouped together two by two so as to form feet 40 passing through the radiative screen 20, and extending vertically between the packaging bottom 4 and soil 5.

With this preferred embodiment, the fresh outside air is drawn into the zone 32 in which it circulates radially inwards, in the direction of the passage 24 and while being channeled between the feet 40. During this circulation, the air cools the floor 5 which thus sees its temperature decrease, this reduction being accentuated by the effect of limiting the heat radiation provided by the radiative screen 20 arranged between the packaging bottom 4 and the floor 5. After having crossed the passage 24, the air enters the zone 34 in which it circulates radially outwards, also being channeled by the feet 40. This air circulation occurs by natural convection. In addition, this air circulation in the zone 34 participates in the cooling of the packaging bottom 4 followed by this same moving air.

To further accentuate the suction effect by natural convection, the support system 3 may also include, at the periphery of the screen 20, a casing 46 surrounding the lateral body 10 of the packaging. This envelope 46 is visible in FIG. 4, and here adopts a cylindrical shape. It defines with the side body 10 an annular air suction channel 48 around the packaging. This envelope 46, centered on the axis 2 and of a shape homothetic to that of the lateral body 10, can extend over a length greater than the height of the support elements 36 of the bottom of the packaging, that is to say say to be of a length greater than the height of the zone 34. Preferably, this length of the casing 46 is less than a quarter of the total length of this packaging in the storage configuration. Alternatively, the casing 46 may not be cylindrical in shape, but take a conical shape widening towards the top of the packaging, still being centered on the axis 2. This solution is particularly preferred in the case where the ratio between the aforementioned diameters D3 and D2 tends towards 1.

The support system can also comprise, at the outer periphery of the casing 46, an annular radiological protection ring, the height of which is at least greater than that of the support elements 36 of the bottom of the packaging. In addition to its role of radiological protection, this ring which can extend over all or part of the height of the casing 46, also makes it possible to thermally insulate the casing 46 from the outside, to improve the draft due to the increased internal / external temperature difference.

In the previously described modes, the radiative screen 20 is crossed by a single circular air passage. However, several passages 24 can be provided within the central part 22 of the screen 20, such as for example several circular passages 24 regularly distributed around the axis 2 as shown in FIG. 5. According to another embodiment possible shown in Figure 6, the air passages 24 may correspond to angular sectors of rings, separated from each other by ligaments of material 50. Referring now to Figures 7 to 9, there is shown a support structure 3 according to another preferred embodiment of the invention. In this embodiment, there are six feet 40, all arranged radially and regularly distributed around the axis 2. These feet can rest directly on the ground, or be coated with a layer of thermal insulation 52 intended to provide the interface with the ground.

Furthermore, the radiative screen 20 is produced by an alternation, in the circumferential direction, of angular screen sectors 54 and mechanical reinforcement elements 56. More precisely, the angular sectors 54 are ring sections, while that the mechanical reinforcing elements 56 are beams oriented radially and arranged at the interface between two directly consecutive ring sections 54, so as to join them together.

The beams 56 also fulfill the function of connection between the feet 40, since each of the latter is secured to the radially outer end of one of the beams.

On the other hand, at its radially inner end, each beam 56 is secured to a central connection member 58 forming an integral part of the screen 20, this member 58 being cylindrical and centered on the axis 2. Thus, passages d 'air 24 are distributed in a manner similar to that shown on the screen of FIG. 6, each being delimited radially inwards by the central member 58, radially outwards by a section of ring 54 , and circumferentially by the radially inner ends of two directly consecutive beams 56.

FIG. 10 schematically represents a step of a method for storing the packaging 1 in the building 7, aimed at putting this packaging in place on the support system 3 already placed on the floor 5. In this regard, it is noted that for its storage, the package 1 is released from its damping covers which usually equip its axial ends during transport.

The simple fact of placing the packaging 1 on the system 3 reveals the zone 34 of cooling air circulation of the packaging bottom. Once installed, the packaging 1 is preferably fixed temporarily to the support system 3, so that these two entities can be moved simultaneously during handling operations carried out during the storage period in building 7.

To achieve this connection between the packaging 1 and the system 3, the latter can be equipped with reversible hooking means comprising fastening elements 64 intended to grip the pins 62 of the packaging. These journals correspond to the handling journals usually provided near the bottom of the packaging.

Of course, various modifications can be made by those skilled in the art to the invention which has just been described, solely by way of nonlimiting examples and according to the scope defined by the appended claims. In particular, the various preferred embodiments can be combined with one another.

Claims

1. Assembly (100) comprising a package (1) for storing radioactive materials and a support system (3) of the package intended, in a storage configuration of the package, to be arranged between a bottom (4) of the packaging and a floor (5) of a storage building (7), characterized in that the support system (3) comprises a radiative screen (20) for thermal protection of the floor having a first lower face (28) and a second upper face (30) opposite the first, the radiative screen (20) comprising a central part (22) provided with at least one air passage (24) ensuring the communication between a zone (32) of circulation of cooling air of the ground defined under the first face (28) of the radiative screen, and a zone (34) of circulation of cooling air of the packaging bottom defined between the second face (30) of the radiative screen (20) and the packaging bottom (4), the support system (3) further comprising a plurality of elements of s support (36) of the package bottom spaced from each other, each support member (3) projecting from the second face (30) of the radiative shield (20) and extending through the area (34) cooling air circulation of the packaging base (4) until contacting the latter, the support system (3) also comprising a plurality of support elements (38) projecting into the area (32) cooling air circulation of the ground, from the first face (28) of the radiative screen (20).

2. Assembly according to claim 1, characterized in that the central part (22) of the radiative screen, in which each air passage (24) is circumscribed, has a first diameter DI smaller than the largest transverse dimension D2. of the packaging (1), so as to answer the following relation:

ID <0.5. D2

3. An assembly according to claim 1 or claim 2, characterized in that said at least one air passage (24) has a cumulative surface SI of air circulation, in that the packaging (1) in configuration d 'storage has a longitudinal central axis (2) orthogonal to the ground (5) and to the radiative screen (20) and centered with respect to the latter, in that the packaging has a projected surface S2 on the ground (5 ), along the longitudinal central axis (2), and in that the surfaces SI and S2 correspond to the following relation:

IF <0.25. S2

4. Assembly according to any one of the preceding claims, characterized in that the support elements (36) of the packaging bottom and the support elements (38) form two by two of the feet (40) passing through the screen. thermal protection radiative (20).

5. Assembly according to any one of the preceding claims, characterized in that in storage configuration, the support system (3) comprises a casing (46) carried at the periphery of the radiative screen (20), the 'envelope defining an air suction channel (48) around the packaging (1).

6. Assembly according to any one of the preceding claims, characterized in that the support elements (38) and / or the support elements (36) are oriented radially or substantially radially relative to the longitudinal central axis (2 ) of the packaging on which the support system (3) is also centered.

7. Assembly according to any one of the preceding claims, characterized in that the support elements (38) and / or the support elements (36) are arranged radially outwardly relative to the central part (22) of the radiative screen (20).

8. Assembly according to any one of the preceding claims, characterized in that the radiative screen is equipped with a plurality of mechanical reinforcement elements (56) interconnecting at least part of the support elements (36) of the bottom and / or support elements (38).

9. Assembly according to the preceding claim, characterized in that the mechanical reinforcement elements (56) have radially inner ends connected together at a central connecting member (58) around which are delimited radially inwardly several air passages (24), each of them also being delimited circumferentially by two directly consecutive mechanical reinforcement elements (56).

10. Assembly according to claim 8 or 9, characterized in that each mechanical reinforcing element (56) is secured, at its radially outer end, to one of the bearing elements (38) and / or to one support elements (36) of the bottom (4).

11. An assembly according to any one of the preceding claims, characterized in that it comprises hooking means allowing reversible hooking of the support system (3) on the packaging (1), the hooking means preferably comprising fixing elements (64) intended to cooperate with handling journals (62) provided on the packaging (1).

12. An assembly according to any one of the preceding claims, characterized in that each support element (36) has an end of contact with the packaging bottom taking the form of a thermal insulation layer.

13. A method of storing a package (1) belonging to an assembly (100) according to any one of the preceding claims, characterized in that it comprises placing the package (1) on the system. support (3) arranged on the floor (5), so as to reveal the cooling air circulation zone (34) of the packaging base (4).