JP2012500986A - Method for manufacturing nuclear material transport and / or storage container using weld shrinkage phenomenon - Google Patents

Abstract

The present invention relates to a method for manufacturing a nuclear material transport and / or storage container (2), said container comprising an inner ferrule (20), an outer ferrule (22) and a heat transfer means (16), said method Forming a substantially circular casing (22 ') having at least one longitudinal slot defined by two opposing longitudinal edges (42) and welding the opposing longitudinal edges to form an outer ferrule. And the welding step is performed such that the weld shrinkage causes, in the radial direction, a compressive stress of the heat transfer means, and each weld bead only interconnects two connected edges.
[Selection] Figure 4

Description

  The present invention relates generally to the field of manufacturing nuclear material transport and / or storage containers.

  In particular, the present invention relates to a method for manufacturing a nuclear material transport and / or storage container comprising an inner ferrule, an outer ferrule, and a heat conducting means in contact with both the inner and outer ferrules.

  Conventionally, storage means, also called storage “baskets” or “rack”, are used for transporting and / or storing nuclear material. These storage means, customarily cylindrical and essentially circular in cross-section, are suitable for containing nuclear material. This storage means is intended to be contained in a cavity of a container in order to form a container for transporting and / or storing nuclear material together with the container, in which the nuclear material is completely contained.

  The cavity described above is generally defined by a side body extending in the longitudinal direction of the container, which side body together with the radiation protection means forms two annular spaces which together form an annular space in which the heat conduction means is accommodated. A sex-concentric ferrule is customarily included, and in particular forms a barrier against neutrons emitted by nuclear material contained in the cavity.

  Heat transfer means may be released by nuclear material to prevent damage to these materials, damage to the mechanical properties of the materials that make up the container, or the risk of heating that may cause an abnormal increase in pressure in the cavity. It is possible to transfer the generated heat to the outside of the container.

  Incorporation of these heat transfer means in the course of the container manufacturing process is usually time consuming and difficult and consequently relatively expensive.

  Patent Document 1 discloses an example of an embodiment. A heat transfer rib is attached to the interferrule space formed by two ferrule sectors arranged edge to edge, the inner radial end is securely attached to the contact of the inner ferrule, and the outer radial end is attached to the outer ferrule. Fits into the recess. Each ferrule is welded to each rib in the circumferential direction by two ferrule sectors held by clamps on the outer radial ends of the rib. As a result, this process requires the same number of ferrule sectors as the heat conductive ribs and requires the production of as many weld beads as the ferrule sectors. The number of heat-conducting ribs is usually very large, e.g. tens, so that the container manufacturing method incorporates and welds multiple sectors while forming an outer ferrule that holds the heat-conducting ribs in place by clamping. Therefore, it takes much time from the viewpoint of assembly time.

  Furthermore, the container manufacturing time is further increased by machining the vertical edge of the ferrule sector to form a recess that captures the outer radial edge of the heat conducting rib.

  Finally, the performance of containers obtained in this way is limited in terms of heat dissipation. In fact, in the circumferential direction, instead of the essentially uniform temperature of the outer ferrule, conversely, in this ferrule, the presence of hot spots is observed in the region of the outer radial end of the heat conducting rib.

  The object of the present invention is therefore to provide at least a partial solution to the above-mentioned drawbacks compared to prior art embodiments.

To achieve this, an object of the present invention is a method of manufacturing a nuclear material transport and / or storage container, wherein the container contacts the inner ferrule, the outer ferrule, and the inner and outer ferrules respectively. Including conduction means, the method comprising the following steps:
Construction of an essentially circular casing having at least one longitudinal slit defined by two opposing longitudinal edges around the heat conducting means incorporated in the inner ferrule;
-Assembly by welding of opposing longitudinal edges to obtain the outer ferrule from the casing, so that the weld shrinkage causes compressive stress of the heat transfer means between the inner and outer ferrules in the radial direction of the vessel And this welding step is performed so that each weld bead obtained between two opposing longitudinal edges only ties these two longitudinal edges together.

  Therefore, the present invention is used to make contact between the heat conducting means and the two ferrules in the radial direction or to increase the contact strength by utilizing the welding shrinkage phenomenon. In other words, the assembly work by welding allows a reduction in the peripheral length of the casing designed to form the outer ferrule to be obtained as a result of the welding shrinkage, and in the space between the ferrules in the radial direction of the heat transfer means Cause compression. This process creates an essentially uniform radial stress of the heat transfer means between the two ferrules in the circumferential direction, resulting in sufficient contact along the circumferential length.

  The main effect of this method is that, unlike the solution shown in Patent Document 1, the number of angular sectors forming the casing does not require any number of heat conducting elements extending in the radial direction in the space between the ferrules. In addition, the number of heat conducting elements can be substantially increased, which is easy to implement and short in manufacturing time. Here, the angular sector needs to be included as a component of the casing that defines the longitudinal slit.

  Further, the method according to the present invention can be applied regardless of the design of the heat conduction means. Finally, this approach has the advantage that it does not require special machining of the longitudinal edges that basically form the slits of the circular casing.

  In this regard, it should be noted that the manufacturing steps of the casing are performed such that each slit extends discontinuously or continuously along the entire length of the casing in the longitudinal direction. For example, discontinuities are created between opposing longitudinal edges by contact points such as weld points, the purpose of which is to pre-assemble the longitudinal edges prior to the assembly step by welding. This pre-assembly is particularly done when multiple angular casing sectors define their longitudinal edges so that they are supported and arranged relative to each other and are arranged around the heat transfer means. Indeed, such sectors may be arranged one by one around the heat conducting means, with the last angular sector pre-assembled into the previous sector using the contacts described above. This pre-assembly has been found to be particularly sensible when the production steps of the casing are carried out in essentially horizontally arranged containers.

  In the special case where a large number of angular casing sectors are arranged around the heat transfer means to form said casing, the sectors are held and arranged by contacts and / or adjacent before the assembly step by welding. Note that it is held and placed by a tool such as a jack designed for this purpose that places the sectors to expose the slits between the sectors. In the latter case, no contact is required, and it is preferable that the longitudinal slit is continuous in the longitudinal direction.

  Also, the casing formed from a plurality of sectors is otherwise around the conduction means, such as by placing a pre-made casing around the heat conduction means using a plurality of sectors exposing vertical slits. Note that the angular casing sector can be manufactured by gradual placement.

  As described again below, it is possible to design a casing that is formed with a single angular section, ie approximately 360 °, but still exposes the longitudinal slit.

  As described above, the welding step is performed such that each weld bead obtained between two opposing longitudinal edges only ties these two longitudinal edges together. In other words, the outer casing obtained after welding does not constrain the elements that are located in the inter-ferrule space and are radially fixed inward. Thus, each bead secures no other than the two edge beads to be connected, regardless of whether it is placed opposite the heat transfer means, radiation protection means, or any other means incorporated into the inter-ferrule space.

  During the weld shrinkage observed during the assembly step, there is a relative movement in the circumferential direction between the inner surface of the casing and the heat transfer element. The effect of the fact that each weld bead connecting the two edges is not fixed to the heat transfer means is that it does not over-constrain the heat transfer means in the circumferential direction and therefore between these heat transfer means. Prevents damage to radiation protection measures built into the. The heat conducting means is preferably selected to have a first contact component that contacts the inner ferrule and a second contact component that contacts the outer ferrule, wherein the first and second components are circumferential. Alternatingly arranged in the direction, each second contact part is connected to two adjacent first contact parts using two connecting parts respectively.

  Thus, the two connecting parts, preferably extending essentially radially from the inner ferrule to the outer ferrule, provide heat conduction to the second contact part supported on the inner face of the outer ferrule. This second contact part can extend over a given length in the circumferential direction, limiting the presence of hot spots on the outer ferrule and thus favoring the temperature uniformity in the same direction. To do.

  Each unit formed by the second contact part and the two associated connection parts preferably forms a pattern, and a series of patterns in the circumferential direction are connected to each other by the first contact part.

  In this configuration, similarly, each unit formed by the first contact component and two related connecting components arranged on both sides thereof forms a pattern, and a series of patterns in the circumferential direction is They are connected to each other by two contact parts.

  Therefore, a first unit formed by the second contact part and two related connecting parts, and an adjacent second unit formed by the first contact part and two related connecting parts These two units share one of the connecting parts. When the first unit forms the first pattern and the second unit forms the second pattern, the first and second patterns sharing one of the connecting parts are preferably of the same shape However, it is preferred that they are arranged in an inverted manner in the radial direction.

  As an example, each pattern has a slot or wave shape in cross section. In the case of a slot, basically, it may be a square, rectangle, or parallelogram shape without a side, or a trapezoidal shape without a base of either the long base or the short base.

  Each first contact component has a length that is essentially the same as the length of the second contact component, although different lengths may be selected without departing from the scope of the present invention.

  As described above, the casing is made using one or more angular casing sectors, and the number Nf of longitudinal slits, each of which is the position of the weld bead, is the same as the number Ns of angular sectors.

  The number Nf of vertical slits is preferably smaller than the number Np of second contact parts belonging to the heat conducting means. The ratio of these two numbers is preferably 0.02 to 0.5.

  In this regard, the number Nf of longitudinal slits, and thus the number Ns of angular sectors, is preferably 4 or less.

  It should be noted that each slit can be evenly opposed to the first or second contact part of the heat conducting means. If the arrangement faces the second contact part, the weld bead made in the assembly step is preferably made so as not to secure the outer ferrule to this second contact part.

  In this regard, as described above, each second contact component is a part of the outer ferrule after the assembly step, whether or not the second component is supported by a portion of the casing having a weld bead. It is actually preferred that it is simply supported on the sides.

  It is therefore preferred that no further parts are used to secure these parts together.

  As mentioned above, during the weld shrinkage observed during the assembly step, there is relative movement in the circumferential direction between the inner surface of the casing and some or all of the second contact parts supported on this surface. This occurs and thus this movement results from a reduction in the diameter of the casing designed to form the outer ferrule after weld shrinkage. This movement ensures that the heat conducting means is not too constrained in the circumferential direction, in particular for the purpose of preventing damage to the radiation protection means preferably arranged in the pattern of the heat conducting means.

  In order to allow this relative movement, each angular sector has an inner surface shaped like an arc in cross section. Such an arc shape can also be used for the second contact component even in the case of the above-described quadrilateral pattern. Basically, a linear shape is also applicable.

  Finally, given that each angular sector preferably has an outer surface shaped like an arc in cross section, for example, to obtain the desired arc-shaped sector, the initial plate using an appropriate tool The manufacture of such a sector of constant thickness via a simple and inexpensive technique of forming shaped metal is easy as a result.

  Finally, each casing sector may be made from a single part, or preferably using a plurality of parts that are attached to each other, for example by welding, before the sector is placed in the heat transfer means. Please keep in mind.

  Other advantages and features of the present invention will become apparent from the following non-limiting detailed disclosure.

  This description is made with reference to the accompanying drawings.

FIG. 2 shows a cross-sectional view of a nuclear fuel assembly transport and / or storage container including a container obtained by a manufacturing method according to a preferred embodiment of the present invention. FIG. 5 shows a perspective view of the container in the course of the manufacturing method after a casing manufacturing step for later forming the outer ferrule of the container. Fig. 3 shows a cross-sectional view of the container shown in Fig. 2. Fig. 4 shows a partial cross-sectional view of the container, schematically showing the next assembly step by welding of the longitudinal edges of the casing. Fig. 6 shows a casing forming the outer ferrule of a container according to another embodiment.

First, referring to FIG. 1, a container 1 for transporting and / or storing nuclear fuel assemblies can be identified. In this regard, it should be recalled that the present invention is in no way limited to the transport / storage of this type of nuclear fuel. As an example, the present invention is also applicable to the transportation and / or storage of PuO ₂ powder.

  The container 1 generally comprises a container 2 that forms the subject of the present invention, and a storage means 4, also called a storage basket, is present inside the container 1. As schematically shown in FIG. 1, the means 4 is designed to be placed in the receiving cavity 6 of the container 2 and also shows a longitudinal axis 8 of this container which coincides with the longitudinal axis of the storage means and the receiving cavity. Has been.

  Throughout this description, the expression “vertical axis” is understood to be parallel to the vertical axis 8 and the vertical direction of the container, and the expression “horizontal axis” is understood to be orthogonal to this same vertical axis 8. I want to be.

  The container 1 and the means 4 forming the containment vessel of the fuel assembly are here shown in a horizontal / horizontal position, which is customarily employed during transport of the assembly, and has a vertical position for loading / unloading the fuel assembly. Is different.

  In general, the container 2 basically comprises a base (not shown) on which the means 4 are placed in a vertical position, a cover (not shown) arranged at the other longitudinal end of the container, and a circumference of the longitudinal axis 8; And it has the side body 10 extended in the vertical axis | shaft direction, ie, the vertical direction of the container 1. As shown in FIG.

  The side body 10 is basically cylindrical and has a circular cross-section and defines an accommodating cavity 6 with an inner side surface 12 having an axis that coincides with the axis 8.

  The bottom of the container defines the bottom of the cavity 6 where the area of the cover is open, but may be made from a single part with part of the side body 10 without exceeding the scope of the invention.

  Referring again to FIG. 1, the design of the side body 10 can be confirmed in detail, first showing two concentric metal ferrules that jointly form an annular space 14 centered on the longitudinal axis 8 of the container. This is in fact an inner ferrule 20 centered on the axis 8 and here with a double thickness design, and an outer ferrule 22 also centered on the axis 8. The outer ferrule 22 is characterized by being formed by a plurality of ferrule angular sectors 24, for example, four sectors of equal angular range, as shown in FIG. These sectors 24 are assembled by longitudinal weld beads 26 connecting the longitudinal edges two by two with opposing longitudinal edges.

  The annular space 14 is filled by heat conduction means 16 and by radiation protection means 18 designed to form a barrier against neutrons emitted by the fuel assembly contained in the storage means 4. Accordingly, these elements are accommodated between an inner ferrule 20 and an outer ferrule 22 whose inner surface coincides with the inner surface 12 of the cavity 6.

  More specifically, the heat conducting means 16 circulates the first contact component 28 in contact with the outer surface of the inner ferrule 20 and the second contact component 30 in contact with the inner surface of the outer ferrule 22 in the circumferential or tangential direction. Alternately. Each of the second contact parts 30 is connected to two adjacent first contact parts 28 by two connection parts 32 that extend basically radially from the inner ferrule toward the outer ferrule at both ends. Thus, heat is transferred to the second contact component. The second contact part 30 is basically the same angular length as that of the first contact part 28 even if different circumferential lengths are used for the first and second parts 28, 30. Extending over. As an index, the circumferential length of each second component 30 can be such that the ratio of the circumferential length of the inner surface of the outer ferrule 22 is 0.01 or more. This relatively large range limits the appearance of hot spots on the outer ferrule 22 and favors temperature uniformity in the circumferential direction.

  As shown in FIG. 1, each unit formed by the second contact piece 30 and the two associated connecting pieces 32 preferably forms a pattern 34, and the series of patterns 34 is formed by the first contact piece 28. Connected to each other. Similarly, each unit formed by the first contact piece 28 and the two associated connecting pieces 32 disposed on both sides thereof forms a pattern 36, and the series of patterns 36 is formed by the second contact piece 30. Connected to each other. The patterns 34, 36 that are connected to each other and share the connecting parts preferably have the same shape and are arranged in an inverted manner in the radial direction.

  As an example, each pattern 34, 36 has a slot or wave shape in cross section. In a typical case of a slot, for example, it basically has a trapezoidal shape without one base, or other shapes deemed appropriate. The parts 28, 30 preferably comprise a straight segment shape in cross section, or a radius that is essentially equal to that of the surface of the ferrule in contact, in order to increase the contact area and thereby improve the heat transfer. In the shape of an arc. Also, to ensure that such contact exists, the heat transfer means 16 is supported or press-fitted radially between the two ferrules 20, 22 in the manner described below.

  For example, the radiation protection means 18 preferably has the shape of a plurality of radiation protection units 40 that are accommodated to fill the recesses defined by the patterns 34 and 36 with these recesses. Thus, each unit or assembly of units is opposed to this contact part by two adjacent connecting parts 32 in the circumferential direction, firstly by a first or second contact part in the radial direction and secondly. It is delimited by the ferrule surface to do. The unit 40 is made of a material known to those skilled in the art that fulfills the radiation protection function against neutrons, for example a material with a vinyl ester resin base, and the heat transfer means 16 is a light alloy of the aluminum alloy type, for example. Made from an alloy, preferably by sheet metal stretching.

  Here, with reference to FIG. 2 to FIG. 4, the manufacturing method of the container 2 described so far is schematically shown.

  This production includes the production of a casing 22 ′ that is essentially circular and centered about the shaft 8 around the heat transfer means 16 attached to the inner ferrule 20, as can be seen in FIGS. 2 and 3. Yes. The casing 22 'is made with a plurality of angular casing sectors 24', the number Ns being 4 in this case. In fact, each sector 24 ′ forms one of the outer ferrule angle sectors 24 described above when the present technique is implemented. Accordingly, in this case as well, the sector 24 ′ preferably has an inner surface and an outer surface, each having two concentric arcuate shapes, and thus basically has a constant thickness. Furthermore, the angular range is basically the same for each of the four sectors 24 '. The sectors are made from a single part or made using a plurality of elements that are attached to each other, for example, preferably attached to each other by welding in the longitudinal direction before the sectors are placed in the heat transfer means. It is done.

  Sectors 24 ′ are arranged between the edges around the axis 8. Accordingly, a slit 44 exists between two opposing vertical edges 42 belonging to two adjacent sectors 24 ′, respectively, at a weld bead position to be formed later by this manufacturing method. Therefore, the number Nf of the longitudinal slits 44 is the same as the number Ns of the angular sectors 24 ′, that is, 4 in this case. Further, the number Nf of the slits 44 is sufficiently smaller than the number Np of the second contact parts 30, and the ratio of these numbers may be 0.02 to 0.5.

  2 and 3, the sectors 24 'are shown at a distance in the radial direction with respect to the outside of the heat conducting means 16 without means for holding them together. First of all, it should be noted that it is still preferred that a pre-assembly of the angular sector 24 ′ is performed in the region of the longitudinal edge 42 in order to ensure retention and placement relative to each other. In fact, such sectors are arranged one by one around the heat transfer means, using contacts provided in the area of the slit, and each time the last angular sector is pre-attached to the previous sector. Accordingly, at the end of the manufacturing step of the casing 22 ′, each slit 44 extends discontinuously along the casing in the longitudinal direction, and the cut provided by the contact is welded between the opposing longitudinal edges 42. Points can be formed.

  Moreover, it is preferable that the casing is in contact with the heat conducting means 16 at the end of the manufacturing step of the casing 22 ′.

  The next step in this approach is the manufacture of the assembly by welding the opposing longitudinal edges 42 to obtain the outer ferrule 22 from the casing 22 '.

  Referring to FIG. 4, this step is such that the weld shrinkage observed during the generation of the weld bead 26 in the slit designed for welding results in a reduction in the diameter of the casing 22 ′ and becomes the outer ferrule of the container 2. In addition, the conventional welding means 56 is used. The aim of this diameter reduction is to bring the heat transfer means 16 and the ferrule 20 and the casing into contact in the radial direction if not in contact, or to increase this contact strength, which means that the means 16 This is because compression stress is applied between these two elements. This process, represented schematically in FIG. 4, actually results in an essentially uniform radial stress on the heat transfer means 16 between the ferrule 20 and the casing 22 ′, schematically indicated by the arrow 50. As such, its diameter is reduced. The observed radial compression can cause elastic deformation of the second contact component 30 to increase the contact surface with the casing 22 'and provide better heat transfer.

  In this preferred embodiment, each weld bead 26 extending essentially over the entire length of the casing 22 ′ is in contact with one of the second contact parts 30. Nevertheless, the weld bead 26 does not fix the casing 22 ′ to the second contact part 30. In fact, each second contact component is simply supported on the inner surface of the outer ferrule 22 after the assembly step is performed. Thus, during the welding shrinkage observed during the assembly step, there is a relative movement in the circumferential direction between the inner surface of the casing 22 'and some or all of the second contact parts 30 supported on this surface. This movement, thus schematically represented in FIG. 4 by the arrow 52, results from a reduction in the diameter of the casing 22 'designed to form the outer ferrule 22 after weld shrinkage. Conversely, the first contact piece 28 of the conduction means 16 is preferably secured and assembled to the inner ferrule 20 using, for example, weld studs and nuts or other similar means.

  According to another embodiment illustrated in FIG. 5, the casing 22 ′ exposes a longitudinal slit 44 between two opposing edges 42, 42, a single, and therefore approximately 360 °, angular sector 24. ′. The assembly step by welding is then performed in a manner similar to that described above to form a weld bead in the slit designed for welding to obtain the desired weld shrinkage.

  Of course, various modifications may be made by those skilled in the art to the invention which has just been described as non-limiting examples.

EP-A1-0 741 628

Claims (10)

A method of manufacturing a nuclear material transport and / or storage container (2), wherein the container is in contact with an inner ferrule (20), an outer ferrule (22), and each of the inner and outer ferrules ( 16), wherein the method comprises the following steps:
An essentially circular shape having at least one longitudinal slit (44) defined by two opposing longitudinal edges (42, 42) around the heat conducting means (16) incorporated in the inner ferrule (20) The casing (22 ') of the
Assembly by welding the opposing longitudinal edges (42, 42) to obtain the outer ferrule (22) from the casing (22 ');
Welding shrinkage causes compressive stress of the heat transfer means (16) between the inner and outer ferrules (20, 22) in the radial direction of the vessel, and two opposing longitudinal edges (42, 42) The method by which this welding step is performed so that each weld bead obtained between them only ties these two longitudinal edges together. The heat conducting means (16) has a first contact component (28) that contacts the inner ferrule (20) and a second contact component (30) that contacts the outer ferrule (22). Preferably, the first and second parts are arranged alternately in the circumferential direction, and each second contact part (30) is adjacent to each other using two connecting parts (32, 32), respectively. To be connected to two matching first contact parts (28, 28);
The method of claim 1, wherein: Each unit formed by the second contact part (30) and the two related connecting parts (32, 32) forms a pattern (34), and a series of patterns in the circumferential direction is said first Connected to each other by contact parts (28) of
The method according to claim 2. Each pattern (34) has a slot or wave shape in cross section;
The method according to claim 2 or 3, characterized in that Each first contact part (28) has a length essentially the same as the length of each second contact part (30);
The method according to any one of claims 2 to 4, characterized in that: The casing (22 ') is made using one or more angular casing sectors (24'), and the number Nf of longitudinal slits (44), each of which is the position of a weld bead (26), is the angular sector (24 ´) the same as the number Ns,
A method according to any one of claims 1 to 5, characterized in that The number Nf of the longitudinal slits (44) is strictly less than the number Np of the second contact parts (30) belonging to the heat conducting means (16),
7. The method of claim 6 in combination with claim 2. The number Ns of angular sectors (24 ′) is 4 or less,
A method according to claim 6 or 7, characterized in that Each angular sector (24 ') has an arcuate inner surface in cross section;
A method according to any one of claims 6 to 8, characterized in that Each second contact part (30) is simply supported on the inner surface of the outer ferrule (22) after performing the assembly step;
10. A method according to any one of claims 1, 3 to 9 in combination with claim 2.

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