EP3391379B1 - Improved heat dissipation structure for natural convection for transport containers and/or storage containers for radioactive material - Google Patents

Description

TECHNICAL AREA

The present invention relates to the field of the evacuation of the heat produced by radioactive materials loaded in a packaging for transport and / or storage of radioactive materials.

More specifically, the present invention relates to a structure of heat dissipation by natural convection, intended to equip the periphery of a package for the transport and / or storage of radioactive materials, for example nuclear fuel assemblies or Radioactive waste.

PRIOR STATE OF THE ART

In the prior art, it is known to assemble an external heat dissipation device around an external surface of a lateral body of a package, with the aim of evacuating the calories to the ambient medium. emitted by radioactive materials contained in the packaging.

This heat removal device is in particular designed so as to limit the temperature reached in service by the various components of the packaging, in particular the seals and the radiological protections, in order to avoid any risk of degradation of these elements.

Furthermore, in addition to being able to perform its main function of heat exchanger with the ambient environment, this device is designed so as to be compatible with the constraints of packaging services, such as decontaminability, resistance in the weather, resistance to atmospheric aggressions, resistance to operating conditions such as immersion during loading and unloading, or even confinement of the neutron shielding resin.

A known solution for this type of external heat dissipation device is in the form of a covering ferrule enveloping the lateral body of the package, and onto which are welded longitudinal straight fins of appropriate section. These fins are also said to be vertical, because they are oriented in the vertical direction when the packaging itself lies vertically.

However, this solution can be improved because in practice, it leads to a temperature profile which gradually increases as a function of the height of the packaging, when the latter rests vertically.

The document DE 29 10 115 A1 teaches a structure of heat dissipation by natural convection, intended to equip the periphery of a packaging with a height of 5.7m for the transport of radioactive materials.

STATEMENT OF THE INVENTION

The object of the invention is therefore to at least partially remedy the drawback mentioned above, relating to the embodiments of the prior art.

• H : la hauteur de chaque demi-structure, dans la direction de la hauteur selon laquelle se succèdent les ailettes primaires inclinées, cette hauteur étant comprise entre 2 et 5 m ;
• h : la hauteur de chaque ailette primaire, comprise entre 10 et 100 mm ;
• d : la largeur de chaque canal primaire de circulation d'air défini entre deux ailettes primaires directement consécutives, cette largeur étant comprise entre 10 et 50 mm ;
• Ep : l'épaisseur de chaque ailette primaire, répondant à la condition d/Ep ≥ 2,5 ;
• L : la largeur de chaque demi-structure selon une direction transversale orthogonale à la direction de la hauteur, ladite largeur L répondant à la condition suivante : $$\mathrm{0,30}.\left(\mathrm{0,35}.{\mathrm{H}}^{\mathrm{0,5}}.{\mathrm{<figure-callout\; id="6"\; label="h"\; filenames="imgf0001.png"\; state="\{\{state\}\}">h</figure-callout>}}^{\mathrm{0,6}}/{\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="imgf0001.png"\; state="\{\{state\}\}">d</figure-callout>}}^{\mathrm{0,1}}\right)\le \mathrm{L}\le \mathrm{3,5}.\left(\mathrm{0,35}.{\mathrm{H}}^{\mathrm{0,5}}.{\mathrm{<figure-callout\; id="6"\; label="h"\; filenames="imgf0001.png"\; state="\{\{state\}\}">h</figure-callout>}}^{\mathrm{0,6}}/{\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="imgf0001.png"\; state="\{\{state\}\}">d</figure-callout>}}^{\mathrm{0,1}}\right)$$
  

To do this, the invention firstly relates to a structure of heat dissipation by natural convection, intended to equip the periphery of a package for the transport and / or storage of radioactive materials, the structure having two adjacent semi-structures each comprising primary fins parallel and inclined with respect to a direction of the height of the structure, the primary fins of the two half-structures forming two by two of the fins in the general shape of an inverted V, when the packaging is arranged vertically with its bottom facing down,
the structure with the following parameters:

• H: the height of each half-structure, in the direction of the height along which the inclined primary fins follow one another, this height being between 2 and 5 m;
• h: the height of each primary fin, between 10 and 100 mm;
• d: the width of each primary air circulation channel defined between two directly consecutive primary fins, this width being between 10 and 50 mm;
• Ep: the thickness of each primary fin, meeting the condition d / Ep ≥ 2.5;
• L: the width of each half-structure in a transverse direction orthogonal to the direction of the height, said width L meeting the following condition: $$0.30.\left(0.35.{\mathrm{H}}^{0.5}.{\mathrm{h}}^{0.6}/{\mathrm{d}}^{0.1}\right)\le \mathrm{The}\le 3.5.\left(0.35.{\mathrm{H}}^{0.5}.{\mathrm{h}}^{0.6}/{\mathrm{d}}^{0.1}\right)$$
  

The specific geometrical conditions defined above make it possible to significantly improve the convective performance of the fins, in particular with respect to the straight vertical fins known from the prior art. In addition, surprisingly, it has been found that with these particular dimensions, there is advantageously a phenomenon of acceleration of the air particles within the primary channels, which gives increased thermal performance. This phenomenon results from the interaction between the air suction zones at the inlet of the primary channels, and the discharge zones located further downstream of these channels. More specifically, part of the air particles from the discharge zones is recycled in the form of a vortex which allows more fresh air to be drawn into the inlet of these same channels. In other words, these swirls created above the fins and primary channels, promote the acceleration of the air in the latter. Thanks to this swirling phenomenon exploited in the present invention, the gains in terms of thermal performance are at least of the order of 10% compared to solutions with vertical fins, with identical heat exchange surfaces.

The invention also has at least one of the following optional features, taken individually or in combination.

The two adjacent half-structures are arranged in a substantially symmetrical manner.

The structure has a possible spacing Ec between the opposite ends of two primary fins jointly forming a fin in the general shape of an inverted V, the two opposite ends forming the point of the V, this spacing Ec meeting the condition Ec / L ≤ 0 2.

The primary fins are straight and inclined by a value between 30 and 60 ° relative to the direction of the height, and preferably inclined by a value of 45 ° relative to this same direction.

The width d is constant and identical for all the primary air circulation channels of each half-structure.

The width L of each half-structure meets the following more precise condition: $$0.55.\left(0.35.{\mathrm{H}}^{0.5}.{\mathrm{h}}^{0.6}/{\mathrm{d}}^{0.1}\right)\le \mathrm{The}\le 1.8.\left(0.35.{\mathrm{H}}^{0.5}.{\mathrm{h}}^{0.6}/{\mathrm{d}}^{0.1}\right)$$

In this limited range of values, the convective performance of the fins is further increased. The gains in terms of thermal performance are at least of the order of 25% compared to solutions with vertical fins, with identical heat exchange surfaces.

The two half-structures are distinct from each other, each having a plate and its own primary fins projecting from the plate. This provides ease of manufacture and assembly.

Alternatively, the two half-structures can be produced on the same plate of height H.

Each half-structure is substantially planar, which also confers ease of manufacture here.

A subject of the invention is also a packaging for the transport and / or storage of radioactive materials comprising a lateral body externally equipped with several heat dissipation structures like that described above, these structures being distributed circumferentially around the lateral body. .

Preferably, a spacing Ec 'between two directly adjacent dissipation structures in the circumferential direction is substantially equal to the spacing Ec.

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

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 représente une vue de face d'un emballage pour l'entreposage et/ou le transport de matières radioactives, comportant une structure de dissipation de chaleur selon un mode de réalisation préféré de la présente invention ;
• la figure 2 représente une vue partielle en coupe prise le long de la ligne II-II de la figure 1 ;
• la figure 3 est une vue agrandie de face d'une partie de la structure de dissipation de chaleur ;
• la figure 4 est une vue en coupe prise le long de la ligne IV-IV de la figure 3 ; et
• la figure 5 est une vue similaire à celle de la figure 3, sur laquelle a été schématisé le principe de tourbillonnement d'air au-dessus des ailettes et des canaux primaires de la structure de dissipation de chaleur.

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

• the figure 1 shows a front view of a package for the storage and / or transport of radioactive materials, comprising a heat dissipation structure according to a preferred embodiment of the present invention;
• the figure 2 shows a partial sectional view taken along line II-II of the figure 1 ;
• the figure 3 is an enlarged front view of part of the heat dissipation structure;
• the figure 4 is a sectional view taken along line IV-IV of the figure 3 ; and
• the figure 5 is a view similar to that of the figure 3 , on which has been schematized the principle of air swirling above the fins and primary channels of the heat dissipation structure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

First of all with reference to figures 1 and 2 , there is shown a package 1 for the storage and / or transport of radioactive materials, such as nuclear fuel assemblies or radioactive waste (not shown).

This package 1 is shown on the figure 1 in the vertical storage position, in which its longitudinal axis 2 is oriented vertically. It rests on a packaging bottom 4, opposite a removable cover 6 in the direction of the height 8, parallel to the longitudinal axis 2. Between the bottom 4 and the cover 6, the packaging 1 has a lateral body s 'extending around the axis 2, and internally defining a cavity 12 for housing the radioactive materials.

The lateral body generally comprises an inner ferrule 14 and an outer concentric ferrule 16, defining an annular space centered on the axis 2. The space is filled by thermal conduction means 20 connecting the two ferrules 14, 16, as well as by neutron protection means 22. The aforementioned means 20, 22 are of conventional design and will therefore not be described further.

The outer shell 16 is produced using a plurality of heat dissipation structures 30 according to the invention. These structures 30 are distributed circumferentially around the axis 2, and each extend at a height H of between 2 and 5 m according to the direction of the height 8. In the example shown on the figure 2 , the structures 30 include bases in the form of rectangular plates, these plates each have two longitudinal edges. These plates are assembled end-to-end by welding at their opposite edges, so as to reconstitute the outer shell 16.

More specifically with reference to the figure 3 , two adjacent structures 30 are shown in the circumferential direction 32 of the package. These two structures 30 are identical, and it is preferably the same for all the structures 30 constituting the outer shell 16, their number possibly being between 5 and 40.

Each heat dissipation structure 30 comprises two half-structures 30a, 30b of similar designs, and being arranged substantially symmetrically with respect to a radial plane Pr of the package. The half-structure 30a comprises straight and parallel primary fins 40a. They are inclined relative to the direction of the height 8 of the package, also corresponding to the height direction of the structure 30. The angle of inclination Aa of the primary fins 40a relative to the direction 8 is preferably around 45 °. Similarly and substantially symmetrically, the half-structure 30b comprises primary fins 40b straight and parallel. They are inclined relative to the direction of the height 8 of the packaging, with an angle of inclination Ab preferably of the order of 45 °. However, the symmetry may not be perfect, for example by providing a small difference in the value of the two angles Aa, Ab, of the order of 10 to 20 °.

The primary fins 40a, 40b of the two half-structures form two by two of the fins 44 in the general shape of an inverted V, when the packaging is arranged vertically with its bottom facing downwards, as in the figures 1 and 3 . Each fin 44 thus formed by one of the primary fins 40a, and the primary fin 40b facing, therefore adopts a chevron shape.

Each half-structure 30a, 30b can be made in one piece in the direction 8, or segmented in the same direction. In the latter case illustrated on the figure 1 , the half-structure segments are then arranged in continuity with each other, being welded end-to-end.

Preferably, the two half-structures 30a, 30b are distinct from each other, that is to say that they each comprise a plate 46 from which the associated primary fins project, as has been shown for the half-structure 30a on the figure 4 . The two plates 46 are assembled together by welding at their edges facing one another in the circumferential direction, so as to reconstitute a structure 30. Thus, the two assembled plates 46 together constitute the abovementioned base in the form of a rectangular plate, participating in reconstitute the outer shell 16.

As illustrated in the figure 3 , the two half-structures 30a, 30b are of symmetrical design. On this same figure 3 , the primary channels 48a, 48b are also shown, delimited respectively by two fins 40a, 40b directly consecutive, in the direction 8.

On the figures 3 and 4 , determining geometric parameters have been identified for obtaining unexpected, particularly high thermal performance.

It is first of all the height H of each half-structure 30a, 30b, corresponding to the height H of the structure 30 composed by these two half-structures. As indicated above, the height H is between 2 and 5 m, and preferably close to 4 m.

It is also the height h of each primary fin 40a, 40b, between 10 and 100 mm, and preferably identical for all the primary fins.

The width d of each primary air circulation channel 48a, 48b is also one of these important parameters. This width d is between 10 and 50 mm, and is found to be constant and identical for all the channels 48a, 48b, over the entire height H.

It is also the thickness Ep of each primary fin 40a, 40b, meeting the condition d / Ep ≥ 2.5. This thickness Ep is also preferably identical for all the primary fins.

Finally, the width L of each half-structure 30a, 30b is also a key parameter. This width L, extending in a transverse direction orthogonal to the direction of the height and comparable to the circumferential direction 32, is identical for the two half-structures and meets the following condition: $$0.30.\left(0.35.{\mathrm{H}}^{0.5}.{\mathrm{h}}^{0.6}/{\mathrm{d}}^{0.1}\right)\le \mathrm{The}\le 3.5.\left(0.35.{\mathrm{H}}^{0.5}.{\mathrm{h}}^{0.6}/{\mathrm{d}}^{0.1}\right)$$

Furthermore, a possible spacing Ec can be provided between the ends opposite two primary fins 40a, 40b, jointly forming a fin in the general shape of an inverted V 44. This spacing, arranged at the point of the fin 44, meets the condition Ec / L ≤ 0.2. The spacings being aligned in direction 8, they together form a sort of vertical air delivery channel 54, at the junction between the two half-structures 30a, 30b of the heat dissipation structure 30.

In addition, a spacing Ec 'is preferably provided between two directly adjacent dissipation structures 30 in the circumferential direction 32. This spacing Ec' is for example substantially equal to the spacing Ec.

This combination of geometric parameters provides very high thermal performance, which is even more important when these parameters meet the following condition: $$0.55.\left(0.35.{\mathrm{H}}^{0.5}.{\mathrm{h}}^{0.6}/{\mathrm{d}}^{0.1}\right)\le \mathrm{The}\le 1.8.\left(0.35.{\mathrm{H}}^{0.5}.{\mathrm{h}}^{0.6}/{\mathrm{d}}^{0.1}\right)$$

Even more preferably, the gains in thermal performance can reach up to 90% compared to the conventional solution with vertical straight fins, when the width L approaches the specific value defined by the following product: 0.35. H ^0.5 . h ^0.6 / d ^0.1 .

In all the cases described above, the gains in thermal performance are explained unexpectedly and surprisingly by obtaining a phenomenon of acceleration of the air particles within the primary channels 48a, 48b. This acceleration of the air in the channels, shown schematically by the arrows 56 on the figure 5 , results from the interaction between the air suction zones 58 at the inlet of the channels 48a, 48b, and the discharge zones 60 located further downstream of these channels. On this figure 5 , the air suction zones 58 correspond to the highly grayed-out parts, in the shape of a triangle with the vertex facing upwards. This is explained by the fact that these suction zones 58, within the channels 48a, 48b, are more extensive going downwards. Conversely, the delivery zones 60 correspond to the less gray parts, in the shape of a triangle with the vertex oriented downwards. This is explained by the fact that these delivery zones are more extensive going upwards.

With the proposed arrangement, when the half-structures are heated, there is a natural convection leading the air to enter the primary channels 48a, 48b, then to propagate upward within these channels, before meeting the air coming from the opposite channels belonging to the other half-structure. This impact at the outlet of the primary channels 48a, 48b, at the point of the inverted Vs, causes the air to be evacuated vertically upwards. But simultaneously, thanks to the controlled proportion between the extent of the suction zones 58 and the extent of the discharge zones 60 resulting from the specific geometric parameters implemented in the invention, air swirls and recirculations are created. above the fins and primary channels 48a, 48b, promoting the acceleration of the air in these channels. These swirls, shown schematically by the arrows 62 on the figure 5 , are obtained from the fact that part of the air particles from the discharge zones 60 is re-aspirated in the primary channels 48a, 48b while being entrained by the suction zones 58, while air particles from the zones suction 58 are driven by the discharge zones 60.

Claims (10)

1. Structure (30) for dissipating heat by natural convection, intended to be provided on the periphery of packaging (1) for the transportation and/or storage of radioactive materials,
   the structure being characterised in that it has two adjacent half-structures (30a, 30b) each comprising primary fins (40a, 40b) that are parallel and inclined with respect to a direction of the height (8) of the structure, the primary fins (40a, 40b) of the two half-structures (30a, 30b) forming, two by two, fins (44) having the overall shape of an inverted V, when the packaging is arranged vertically with its bottom (4) oriented downwards,
   the structure having the following parameters:

   - H: the height of each half-structure (30a, 30b), in the direction of the height (8) along which the inclined primary fins (40a, 40b) are successively arranged, this height being between 2 and 5m;

   - h: the height of each primary fin (40a, 40b), between 10 and 100mm;

   - d: the width of each primary channel (48a, 48b) for circulation of air defined between two directly consecutive primary fins, this width being between 10 and 50mm;

   - Ep: the thickness of each primary fin (40a, 40b), satisfying the condition d/Ep ≥ 2.5;

   - L: the width of each half-structure (30a, 30b) in a transverse direction orthogonal to the direction of the height (8), said width L satisfying the following condition: $$0.30.\left(0.35.{\mathrm{H}}^{0.5}.{\mathrm{h}}^{0.6}/{\mathrm{d}}^{0.1}\right)\le \mathrm{L}\le 3.5.\left(0.35.{\mathrm{H}}^{0.5}.{\mathrm{h}}^{0.6}/{\mathrm{d}}^{0.1}\right)$$

   
2. Structure for dissipating heat according to claim 1, characterised in that the two adjacent half-structures (30a, 30b) are arranged in a substantially symmetrical manner.
3. Structure for dissipating heat according to claim 1 or claim 2, characterised in that the primary fins (40a, 40b) are straight and inclined by a value between 30 and 60° with respect to the direction of the height (8), and preferably inclined by a value of 45° with respect to this same direction.
4. Structure for dissipating heat according to any one of the previous claims, characterised in that the width d is constant and identical for all the primary channels (40a, 40b) for circulation of air of each half-structure (30a, 30b).
5. Structure for dissipating heat according to any one of the previous claims, characterised in that width L of each half-structure (30a, 30b) satisfies the following condition: $$0.55.\left(0.35.{\mathrm{H}}^{0.5}.{\mathrm{h}}^{0.6}/{\mathrm{d}}^{0.1}\right)\le \mathrm{L}\le 1.8.\left(0.35.{\mathrm{H}}^{0.5}.{\mathrm{h}}^{0.6}/{\mathrm{d}}^{0.1}\right)$$

   
6. Structure for dissipating heat according to any one of the previous claims, characterised in that the two half-structures (30a, 30b) are distinct from each other, each having a plate (46) and its own primary fins that protrude from the plate.
7. Structure for dissipating heat according to any one of claims 1 to 5, characterised in that the two half-structures (30a, 30b) are made on the same plate having a height H.
8. Structure for dissipating heat according to any one of the previous claims, characterised in that each half-structure (30a, 30b) is substantially flat.
9. Packaging (1) for the transportation and/or the storage of radioactive materials, comprising a lateral body (10) provided on the outside with a plurality of structures for dissipating heat (30) according to any one of the previous claims, distributed circumferentially around the lateral body (10).
10. Packaging according to the previous claim, characterised in that a spacing Ec' between two dissipation structures (30) directly adjacent in the circumferential direction (32), is substantially equal to the spacing Ec.

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