U.S. patent application number 13/059115 was filed with the patent office on 2011-06-16 for method for manufacture of a package for the transport and/or storage of nuclear material, using the phenomenon of welding shrinkage.
This patent application is currently assigned to TN INTERNATIONAL. Invention is credited to Gilles Bonnet, Celine Fontanet, Julien Laborde.
Application Number | 20110142571 13/059115 |
Document ID | / |
Family ID | 40717128 |
Filed Date | 2011-06-16 |
United States Patent
Application |
20110142571 |
Kind Code |
A1 |
Bonnet; Gilles ; et
al. |
June 16, 2011 |
METHOD FOR MANUFACTURE OF A PACKAGE FOR THE TRANSPORT AND/OR
STORAGE OF NUCLEAR MATERIAL, USING THE PHENOMENON OF WELDING
SHRINKAGE
Abstract
A method for the manufacture of a package for the transport
and/or storage of nuclear materials, where the package includes an
inner ferrule, an outerferrule and means of thermal conduction, and
where the method includes: the construction of an essentially
circular casing having at least one lengthways slit defined by two
facing lengthways edges; and the welding of the facing lengthways
edges, in order to obtain the outer ferrule, where this step is
accomplished such that the welding shrinkage causes a compression
stress of the means of thermal conduction between the ferrules, in
a radial direction, and such that each welding bead only fastens
the two edges which it links one on to the other.
Inventors: |
Bonnet; Gilles; (Cherbourg,
FR) ; Fontanet; Celine; (Bazainville, FR) ;
Laborde; Julien; (Dampierre en Yvelines, FR) |
Assignee: |
TN INTERNATIONAL
Montigny Le Bretonneux
FR
|
Family ID: |
40717128 |
Appl. No.: |
13/059115 |
Filed: |
August 26, 2009 |
PCT Filed: |
August 26, 2009 |
PCT NO: |
PCT/EP2009/060962 |
371 Date: |
February 15, 2011 |
Current U.S.
Class: |
413/1 |
Current CPC
Class: |
G21F 5/008 20130101;
G21F 5/10 20130101 |
Class at
Publication: |
413/1 |
International
Class: |
B21D 51/26 20060101
B21D051/26 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 27, 2008 |
FR |
08 55738 |
Claims
1. A method for manufacture of a package for the transport and/or
storage of nuclear materials, where the said package includes an
inner ferrule, an outer ferrule and also means for thermal
conduction in contact with each of the inner and outer ferrules,
where the said method includes the following steps: the
construction, around the means of thermal conduction fitted to the
inner ferrule, of an essentially circular casing having at least
one lengthways slit defined by two facing lengthways edges; and the
assembly by welding of the facing lengthways edges, in order to
obtain, starting from the said casing, the said outer ferrule,
where this step is implemented such that the welding shrinkage
causes a compression stress of the means of thermal condition
between the inner and outer ferrules in a radial direction of the
package, and in such a way that each welding bead obtained between
two facing lengthways edges only fastens these two lengthways edges
onto one another.
2. A method according to claim 1, characterised in that the said
means of thermal conduction are preferably chosen such that they
have first parts of contact intended to be in contact with the
inner ferrule, and second parts of contact intended to be in
contact with the outer ferrule, where the said first and second
parts are arranged in alternating fashion in the circumferential
direction, with each second part of contact linked to the first two
parts of contact being directly consecutive to it, using
respectively two joining parts.
3. A method according to claim 2, characterised in that each unit
formed by a second part of contact and its two associated joining
parts forms a pattern, where the successive patterns in the
circumferential direction are linked to one another by the said
first parts of contact.
4. A method according to claim 2, characterised in that each
pattern takes in its transverse section the shape of a slot or a
wave.
5. A method according to claim 1, wherein each part of contact has
a length essentially identical to that of each second part of
contact.
6. A method according to claim 1, wherein said casing is made using
one or more angular casing sectors, where the number Nf of
lengthways slits, each intended to be the location of a welding
bead, is identical to the number Ns of angular sectors.
7. A method according to claim 6, wherein the number Nf of
lengthways slits is strictly lower than the number Np of second
parts of contact belonging to the means of thermal conduction.
8. A method according to claim 6, characterised in that the said
number Ns of angular sectors is less than or equal to four.
9. A method according to claim 6, characterised in that each
angular sector has an inner surface with, in its transverse
section, the shape of an arc of a circle.
10. A method according to claim 2, wherein each second part of
contact is intended simply to be supported on an inner surface of
the outer ferrule, after implementation of the said assembly step.
Description
DISCLOSURE
[0001] 1. Technical Field
[0002] The present invention relates generally to the field of the
manufacture of packages for the transport and/or storage of nuclear
material.
[0003] In particular, the invention concerns a method for
manufacture of a package for the transport and/or storage of
nuclear materials, including an inner ferrule, an outer ferrule and
also means for thermal conduction in contact with both the inner
and outer ferrules.
[0004] 2. State of the Prior Art
[0005] Traditionally, for the transport and/or storage of nuclear
materials, storage devices, also called storage "baskets" or
"racks", are used. These storage devices, habitually cylindrical in
shape and essentially circular in section, are suitable for
receiving nuclear materials. The storage device is intended to be
housed in the cavity of a package in order to form jointly with the
latter a container for the transport and/or storage of nuclear
materials, in which they are completely confined.
[0006] The abovementioned cavity is generally defined by a lateral
body extending in a lengthways direction of the package, where this
lateral body habitually includes two metal concentric ferrules
jointly forming an annular space inside which are housed means for
thermal conduction, together with a radiological protection device,
in particular to form a barrier against the neutrons emitted by the
nuclear material housed in the cavity.
[0007] The means of thermal conduction enable the heat released by
the nuclear materials to be conducted outside the container, in
order to prevent any risk of overheating, which might cause damage
to these materials, an impairment of the mechanical properties of
the materials constituting the package, or again an abnormal rise
in pressure in the cavity.
[0008] The installation of these means of thermal conduction in the
course of the method of manufacture of the package is often lengthy
and difficult, and as a consequence relatively expensive.
[0009] An example of an embodiment is disclosed in document EP-A1-0
741 628. Thermal conduction ribs are installed in the inter-ferrule
space, with an inner radial end attached securely to a part of
contact of the inner ferrule, and an outer radial end in a recess
of the outer ferrule, formed by the two ferrule sectors positioned
edge-to-edge. For each rib it is the assembly by welding of the two
ferrule sectors which creates the maintenance by clamping of the
outer radial end of the rib, in the circumferential direction. As a
consequence, this procedure requires as many ferrule sectors as
there are thermal conduction ribs, and also requires the production
of as many welding beads as there are ferrule sectors. Since the
number of thermal conduction ribs is generally very high, able to
reach, for example, several tens, the method of manufacture of the
package is therefore greatly hindered, in terms of assembly time,
by the installation and welding of the many sectors forming the
outer ferrule which holds in place, by clamping, the thermal
conduction ribs.
[0010] Moreover, the package manufacturing time is hindered further
by the machining on the lengthways edges of the ferrule sectors,
intended to form the recesses gripping the outer radial ends of the
thermal conduction ribs.
[0011] Lastly, the performance of a package obtained in this
manner, in terms of heat evacuation, is limited. Indeed, instead of
an essentially uniform temperature of the outer ferrule, in the
circumferential direction, on the contrary the existence of hot
points on this ferrule is observed, in the area of the outer radial
ends of the thermal conduction ribs.
SUMMARY OF THE INVENTION
[0012] The purpose of the invention is therefore to provide at
least partially a solution to the disadvantages mentioned above,
compared with the embodiments of the prior art.
[0013] To accomplish this, the object of the invention is a method
for manufacture of a package for the transport and/or storage of
nuclear materials, where the said package includes an inner
ferrule, an outer ferrule and also means for thermal conduction in
contact with each of the inner and outer ferrules, where the said
method includes the following steps:
[0014] the construction, around the means of thermal conduction
fitted to the inner ferrule, of an essentially circular casing
having at least one lengthways slit defined by two facing
lengthways edges; and
[0015] the assembly by welding of the facing lengthways edges, in
order to obtain, starting from the said casing, the said outer
ferrule, where this step is undertaken in such a way that the
welding shrinkage causes a compression stress of the means of
thermal conduction between the inner and outer ferrules, in a
radial direction of the package, and in such a way that each
welding bead obtained between two facing lengthways edges only
fastens these two lengthways edges on to one another.
[0016] Thus, the invention makes use of the phenomenon of welding
shrinkage, which is put to use to obtain the contact, or increase
the intensity of this contact of the means of thermal conduction
with the two ferrules, in the radial direction. In other words, the
operation of assembly by welding allows, as a consequence of the
welding shrinkage, a reduction of the perimeter of the casing
designed to form the outer ferrule to be obtained, leading to a
radial compression of the means of thermal conduction in the
inter-ferrule space. This procedure leads to an essentially uniform
radial stress of the means of thermal conduction between the two
ferrules, in the circumferential direction, giving satisfactory
contact along the length of the latter.
[0017] The principal benefit of this method lies in the simplicity
of implementation and the short manufacturing time since, unlike
the solution presented in document EP-A1-0 741 628, the number of
angular sector(s) forming the casing is not conditional in any way
on the number of thermal conduction elements extending radially in
the inter-ferrule space, and this latter number can, indeed, be
substantially higher. Here, it is stipulated that the angular
sector(s) must be included as the constituent elements of the
casing, defining the lengthways slits.
[0018] In addition, the method according to the invention is
applicable whatever the design of the means of thermal conduction.
Finally, it does not advantageously require any particular
machining of the lengthways edges forming the slit(s) of the
essentially circular casing.
[0019] With this regard, it is noted that the step of production of
this casing may be implemented such that each slit extends
discontinuously or continuously along the full length of this
casing in the lengthways direction. By way of example,
discontinuities may be created by points of tangency, such as
welding points, between the facing lengthways edges, the aim being
to pre-assemble the latter before the step of assembly by welding.
This pre-assembly is sought in particular when many angular casing
sectors are to define these lengthways edges, and to be arranged
around the means of thermal conduction, in order to hold and
position them relative to one another. Indeed, such sectors may be
positioned one-by-one around the means of thermal conduction, each
time pre-assembling the final angular sector on the previous
sector, using the points of tangency mentioned above. This
pre-assembly then proves to be particularly judicious when this
step of manufacture of the casing is implemented with the package
positioned essentially horizontally.
[0020] It is noted that in this particular case, in which a large
number of angular casing sectors are arranged around the means of
thermal conduction to form the said casing, the sectors can be held
and positioned, before the step of assembly by welding, by the
points of tangency, and/or by tools designed for this purpose, such
as jacks positioning the sectors in order to reveal the said slits
between the directly consecutive sectors. In this latter case the
points of tangency are no longer required, and the lengthways slits
are then preferentially continuous in the lengthways direction.
[0021] Moreover, it is noted that the casing formed from several
sectors could be produced otherwise than by gradually arranging
angular casing sectors around the means of conduction, such as, for
example by positioning a prefabricated casing around these means of
thermal conduction, using several sectors revealing the lengthways
slits.
[0022] As will be recalled below, it is also possible to design a
casing formed from a single angular section, therefore close to
360.degree., but which nonetheless reveals a lengthways slit.
[0023] As mentioned above, the step of welding is implemented such
that each welding bead obtained between two facing lengthways edges
only fastens these two lengthways edges on to one another. In other
words, the outer casing obtained after welding is free relative to
the elements located in the inter-ferrule space, against which it
is pinned radially towards the interior. Each bead therefore
provides no other fastening than that of the two edges which it
links, whether it is positioned opposite the means of thermal
conduction, the means of radiological protection, or again opposite
any other means which may be installed in the inter-ferrule
space.
[0024] During the welding shrinkage observed during the assembly
step, a relative movement is created in the circumferential
direction between the inner surface of the casing and the thermal
conduction elements. The advantageous consequence of the fact that
each welding bead linking two edges is not fastened on to the means
of thermal conduction is that it does not excessively constrain the
latter in the circumferential direction, thus preventing damaging
the means of radiological protection which may be installed between
these means of thermal conduction. The said means of thermal
conduction are preferably chosen such that they have first parts of
contact intended to be in contact with the inner ferrule, and
second parts of contact intended to be in contact with the outer
ferrule, where the said first and second parts are arranged in
alternating fashion in the circumferential direction, with each
second part of contact linked to the first two parts of contact
being directly consecutive to it, using respectively two joining
parts.
[0025] Thus, it is the two joining parts, preferably extending
essentially radially from the inner ferrule to the outer ferrule,
which provide the heat transfer to the second part of contact,
which is supported on the inner surface of the outer ferrule. This
second part of contact can extend over a given length in the
circumferential direction, which limits the appearance of hot
points on the outer ferrule, therefore favoring its temperature
uniformity in this same direction.
[0026] Each unit formed by a second part of contact and its two
associated joining parts preferably forms a pattern, where the
successive patterns in the circumferential direction are linked to
one another by the said first parts of contact.
[0027] In this configuration it can similarly be observed that each
unit formed by a first part of contact and its two associated
joining parts, positioned either side of the part of contact, forms
a pattern, where the successive patterns in the circumferential
direction are linked to one another by the said second parts of
contact.
[0028] Thus, if a first unit formed by a second part of contact and
its two associated joining parts, and a second, directly
consecutive unit formed by a first part of contact and its two
associated joining parts, are considered, then these two units have
one of the joining parts in common. If the first unit forms a first
pattern and the second unit forms a second pattern, then,
preferably, the first and second patterns sharing one of the
joining parts are preferably of the same shape, but arranged in an
inverted fashion relative to one another, in the radial
direction.
[0029] As an example, each pattern takes in its transverse section
the shape of a slot or a wave. In the case of the slot this may be
an essentially square, rectangular or parallelogram shape, without
one of the sides, or again a trapezoid shape without one of its
bases, either the larger or the smaller base.
[0030] Each first part of contact preferably has a length
essentially identical to that of the second part of contact, even
if different lengths could be chosen, without going beyond the
scope of the invention.
[0031] As mentioned above, the said casing is made using one or
more angular casing sectors, where the number Nf of lengthways
slits, each intended to be the location of a welding bead, is
identical to the number Ns of angular sectors.
[0032] The number Nf of lengthways slits is preferably lower than
the number Np of second parts of contact belonging to the means of
thermal conduction. The ratio between these two numbers is
preferably between 0.02 and 0.5.
[0033] With this regard, the number Nf of lengthways slits, and
therefore also the said number Ns of angular sectors, is less than
or equal to four.
[0034] It is noted that each slit may equally be facing a first or
second part of contact of the means of thermal conduction. If the
positioning faces a second part of contact, it is however done
preferably such that the welding bead made in the assembly step
does not become secured to the outer ferrule on this second part of
contact.
[0035] With this regard, as mentioned above, each second part of
contact is, indeed, preferably intended to be simply supported on
an inner surface of the outer ferrule, after implementation of the
said assembly step, whether or not the second part is supported on
a part of the casing having a welding bead.
[0036] Preferably, therefore, no additional element is used to
fasten these elements pinned one on to the other.
[0037] As was explained above, during the welding shrinkage
observed during the assembly step, a relative movement is created
in the circumferential direction between the inner surface of the
casing and some or all of the second parts of contact supported on
this surface, and this movement therefore results from the
reduction of the diameter in the casing designed to form the outer
ferrule, after welding shrinkage. This movement ensures that the
means of thermal conduction are not excessively constrained in the
circumferential direction, notably with a view to preventing
damaging the means of radiological protection, which are preferably
arranged in the patterns of the means of thermal conduction.
[0038] To facilitate this relative movement each angular section
has an inner surface shaped like the arc of a circle in its
transverse section. Such an arc of a circle shape can moreover be
adopted for the second parts of contact, even in the cases of
patterns with a quadrilateral shape mentioned above. An essentially
straight shape is also suitable.
[0039] Finally, given that each angular sector also preferably has
an outer surface shaped like the arc of a circle in its transverse
section, it is consequently easy to manufacture such sectors, of
constant thickness, for example through a simple and inexpensive
technique seeking to shape, using an appropriate tool, an initially
flat sheet of metal, in order to obtain the desired arc-shaped
sector.
[0040] Finally, it is noted that each casing sector may be made
from a single part, or alternatively using several elements added
attached to one another, for example by welding, preferably before
the sector is positioned on the means of thermal conduction.
[0041] Other advantages and characteristics of the invention will
appear in the non-restrictive detailed disclosure below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] This description will be made with reference to the attached
illustrations, among which
[0043] FIG. 1 represents a transverse section view of a container
for the transport and/or storage of assemblies of nuclear fuel,
including a package obtained by a method of manufacture according
to the preferred embodiment of the present invention;
[0044] FIG. 2 represents a perspective view of the package in the
course of the manufacturing method, after the step of production of
the casing intended subsequently to form the outer ferrule of the
package;
[0045] FIG. 3 represents a transverse section view of the package
shown in FIG. 2;
[0046] FIG. 4 represents a partial transverse section view of the
package, representing schematically the next step of assembly by
welding of the lengthways edges of the casing; and
[0047] FIG. 5 represents a casing intended to form the outer
ferrule of the package, according to an alternative embodiment.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0048] Firstly, with reference to FIG. 1, a container 1 for the
transport and/or storage of assemblies of nuclear fuel can be seen.
It is with this regard recalled that the invention is not limited
in any way to the transport/storage of this type of nuclear
material. As an example, the invention can also be applied to the
transport/storage of PuO.sub.2 powder.
[0049] Container 1 comprises globally a package 2 forming the
subject of the present invention, inside which is a storage device
4, also called a storage basket. Device 4 is designed to be
positioned in a receptacle cavity 6 of package 2, as is shown
schematically in FIG. 1, where it is also possible to note the
lengthways axis 8 of this package, merged with the lengthways axes
of the storage device and the receptacle cavity.
[0050] Throughout the disclosure the term "lengthways" must be
understood as being parallel to the lengthways axis 8 and to the
lengthways direction of the package, and the term "transverse" must
be understood as being orthogonal to this same lengthways axis
8.
[0051] Container 1 and device 4 forming reception receptacles of
the fuel assemblies are shown here in a horizontal/lying position,
which is habitually adopted during the transport of the assemblies,
and which differs from the vertical position for loading/unloading
of the fuel assemblies.
[0052] Generally, package 2 essentially has a base (not
represented) on which the device 4 is intended to rest in its
vertical position, a cover (not represented) positioned at the
other lengthways end of the package, and a lateral body 10
extending around and in lengthways axis 8, i.e. in the lengthways
direction of container 1.
[0053] It is this lateral body 10 which defines the receptacle
cavity 6, using a lateral inner surface 12, of essentially
cylindrical shape and circular section, and having an axis merged
with axis 8.
[0054] The base of the package, which defines the base of cavity 6
which is open in the area of the cover, may be manufactured from a
single part with a part of lateral body 10, without going beyond
the scope of the invention.
[0055] Again with reference to FIG. 1, it is possible to see in
detailed fashion the design of lateral body 10, which firstly
presents two concentric metal ferrules forming jointly an annular
space 14 centred on the lengthways axis 8 of the package. This is,
indeed, an inner ferrule 20 centred on axis 8, which is here of a
double-thickness design, and an outer ferrule 22, which is also
centred on axis 8. This outer ferrule 22 has the feature that it is
formed by a number of angular sectors of ferrule 24, for example
four such sectors, of equal angular extent, as has been represented
in FIG. 1. These sectors 24 are assembled on to one another by
their facing lengthways edges, by means of lengthways welding beads
26 linking these lengthways edges two-by-two.
[0056] The annular space 14 is filled by means of thermal
conduction 16, and also by a radiological protection device 18
designed to form a barrier against the neutrons emitted by the fuel
assemblies housed in the storage device 4. Thus, these elements are
housed between inner ferrule 20, the inner surface of which matches
the lateral inner surface 12 of cavity 6, and outer ferrule 22.
[0057] More specifically, the means of thermal conduction 16 have,
alternating in the circumferential or tangential direction, first
parts of contact 28 in contact with the outer surface of the inner
ferrule 20, and also second parts of contact 30 in contact with the
inner surface of the outer ferrule 22. In addition, each second
part of contact 30 is linked at its ends with the first two parts
of contact 28 which are directly consecutive to it, by means
respectively of two joining parts 32 extending essentially radially
from the inner ferrule to the outer ferrule, providing by this
means the heat transfer to the second part of contact. The second
parts of contact 30 extend over an angular length which may be
essentially identical to that of the first parts 28, even if a
different circumferential length could be used for the first and
second parts 28, 30. As an indication, the circumferential length
of each second part 30 can be such that its ratio with the
perimeter of the inner surface of the outer ferrule 22 is greater
than 0.01. This relatively great extent limits the appearance of
hot points on the outer ferrule 22, and favours its temperature
uniformity in the circumferential direction.
[0058] As can be seen in FIG. 1, each unit formed by a second part
of contact 30 and its two associated joining parts 32 preferably
forms a pattern 34, where the successive patterns are linked to one
another by the first parts of contact 28. Similarly, each unit
formed by a first part of contact 28 and its two associated joining
parts 32 positioned either side of the latter forms a pattern 36,
where the successive patterns 36 are linked to one another by the
second parts of contact 30. The patterns 34, 36 which succeed one
another, and which share the joining parts, preferably have the
same shape, but arranged in a reverse fashion relative to one
another, in the radial direction.
[0059] By way of example, each pattern 34, 36 takes in its
transverse section the shape of a slot or a wave. In the
represented case of a slot this has, for example, an essentially
trapezoid shape without one of its bases, or again any other shape
deemed appropriate. Parts 28, 30 can take in their transverse
section the shape of segments of a straight line, or again arcs of
a circle, preferably with a radius essentially identical to that of
the surface of the ferrule with which they are in contact, in order
to increase the extent of this contact and by this means improve
the thermal transfer. Moreover, to ensure that such a contact
exists, the means of thermal conduction 16 are held, or compressed
radially between the two ferrules 20, 22, in a manner which will be
described in detail in due course.
[0060] The radiological protection device 18, for its part,
preferably takes the shape of multiple radiological protection
units 40, housed in the recesses defined by the patterns 34, 36, in
order to fill these recesses. Thus, each unit or assembly of units
is demarcated circumferentially by two directly consecutive joining
parts 32, and radially firstly by means of a first or second part
of contact, and secondly by means of the ferrule surface facing
this latter part of contact. The units 40 are made from any
material known to the skilled man in the art to fulfil a
radiological protection function with regard to neutrons, such as,
for example, a material with a base of vinyl ester resin, and the
means of thermal conduction 16 are, for example, made from a light
alloy of the aluminium alloy type, preferably by drawing of sheet
metal.
[0061] With reference at present to FIGS. 2 to 4, a method of
manufacture of package 2 which has just been described is
represented schematically.
[0062] The manufacture includes the production, around the means of
thermal conduction 16 fitted to the inner ferrule 20, of a casing
22' which is essentially circular, centred on axis 8, as is visible
in FIGS. 2 and 3. This casing 22' is made using several angular
casing sectors 24', the number Ns of which is four in this case.
Indeed, each sector 24' is intended to form, when the method is
implemented, one of the outer ferrule angular sectors 24 described
above. Thus, in this case also, sectors 24' preferably have an
inner surface and an outer surface which have respectively the
shape of two arcs of a circle with the same centre, and therefore
of essentially constant thickness. Furthermore, the angular extent
is also essentially the same for each of the four sectors 24'. The
latter are made either from a single part, or using several
elements attached to one another, for example attached to one
another by welding in the lengthways direction, preferably before
the sector is positioned on the means of thermal conduction.
[0063] Sectors 24' are arranged edge-to-edge around axis 8. Thus,
between two facing lengthways edges 42, belonging respectively to
two directly consecutive sectors 24', there is a slit 44 intended
to be the location of a welding bead, which will be made later
during the manufacturing method. Thus, the number Nf of lengthways
slits 44 is identical to the number Ns of angular sectors 24', i.e.
four in the present case. In addition, the number Nf of slits 44 is
well below the number Np of second parts of contact 30, and the
ratio between these two numbers may be between 0.02 and 0.5.
[0064] In the schematic views of FIGS. 2 and 3 the sectors 24' have
been represented without any means to hold them one to another, and
at a distance radially towards the outside of the means of thermal
conduction 16. Firstly, it is noted that a pre-assembly of the
angular sectors 24' is nonetheless preferentially undertaken in the
area of the lengthways edges 42, in order to ensure that they are
held and positioned one relative to another. Indeed, such sectors
may be positioned one-by-one around the means of thermal
conduction, each time pre-assembling the final angular sector on
the previous sector, using points of tangency made in the area of
the slit. Thus, at the end of the step of production of the casing
22', each slit 44 can extend discontinuously along this casing, in
the lengthways direction, and these discontinuities created by the
points of tangency can take the form of welding points between the
facing lengthways edges 42.
[0065] In addition, at the end of the step of production of casing
22' the latter is preferably in contact with the means of thermal
conduction 16.
[0066] The following step of the method consists in producing the
assembly by welding of the facing lengthways edges 42, in order to
obtain, from the casing 22', the outer ferrule 22.
[0067] With reference to FIG. 4, this step is undertaken with
conventional welding means 56 such that the welding shrinkage,
observed during the production of the welding beads 26 in the slits
designed for this purpose, causes a reduction of the diameter of
the casing 22', which then becomes the outer ferrule of package 2.
The aim of this reduction of diameter is to obtain the contact, if
it has not yet been made, or to emphasise the intensity of this
contact, of the means of thermal conduction 16 with the ferrule 20
and the casing, in the radial direction, since these means 16 are
subjected to a compression stress between these two elements. This
procedure, which is represented schematically in FIG. 4, indeed
leads to an essentially uniform radial stress of the means of
thermal conduction 16 between the ferrule 20 and the casing 22',
the diameter of which is reduced, as is shown schematically by the
arrows 50. The observed radial compression may lead to an elastic
deformation of the second parts of contact 30 with a view to
increasing the surface of this contact with the casing 22', and
thus providing better thermal transfer.
[0068] In this preferred embodiment, each welding bead 26, which
extends essentially over the entire length of casing 22', is
intended to be facing, and in contact with, one of the second parts
of contact 30. Nonetheless, it is however made such that the
welding bead 26 does not become secured to the casing 22' on this
second part of contact 30. Indeed, each second part of contact is
simply supported on the inner surface of the outer ferrule 22 after
the implementation of the assembly step. Thus, during the welding
shrinkage observed during the assembly step, a relative movement is
created in the circumferential direction between the inner surface
of the casing 22' and some or all of the second parts of contact 30
supported on this surface, and this movement, represented
schematically by arrow 52 in FIG. 4, therefore results from the
reduction of the diameter of the casing 22' designed to form the
outer ferrule 22, after welding shrinkage. Conversely, it is
stipulated that the first parts of contact 28 of the means of
conduction 16 are preferably assembled securely on the inner
ferrule 20, for example using welded studs and nuts, or any other
similar means.
[0069] According to an alternative embodiment represented
diagrammatically in FIG. 5, casing 22' is formed from a single
angular sector 24', therefore close to 360.degree., revealing a
lengthways slit 44 between its two facing edges 42, 42. The step of
assembly by welding is then undertaken in a manner similar to that
set out above, making a welding bead in the slit designed for this
purpose, in order to obtain the desired welding shrinkage.
[0070] Naturally, various modifications can be made by the skilled
man in the art to the invention which has just been described,
solely as non-restrictive examples.
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