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.

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.