Plastic and nonmetallic article shaping or treating: processes – Shaping or treating radioactive material
Patent
1995-06-28
1997-01-07
Mai, Ngoclan
Plastic and nonmetallic article shaping or treating: processes
Shaping or treating radioactive material
588 2, 588 16, G21C 2100
Patent
active
055920276
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of compacting, without danger of ignition and/or explosion, metal waste that is liable to ignite and/or explode when compacted in a conventional manner.
Said method is advantageously implemented during treatment of irradiated metal waste, in particular containing zirconium and/or magnesium and/or alloys of said metals. The method is described in greater detail below with reference to this nuclear context, however that does not imply any limitation on its implementation in other contexts. The person skilled in the art will readily understand on reading the text below that the principle of the invention, i.e. internal blanketing, is transposable to numerous fields.
2. Description of the Related Art
The invention proposes a solution to the general problem of compacting waste of pyrophoric tendency.
Such waste is generated, in particular, during retreatment of irradiated nuclear fuel elements. Thus, for example, the shearing of said elements generates both fuel in solution and pieces of tube or "hulls", generally made of zircalloy. At present, said hulls are washed and placed in drums. Said drums are then embedded in cement without being reduced in volume. The same applies to storing other materials, and in particular other structural elements for said fuels, such as grids and endpieces, to storing magnesium. The invention seeks to optimize the final storage volume; to reduce the size of said drums.
Compacting such drums nevertheless poses a problem in that firstly said drums contain oxygen and fines, and secondly compacting makes use of energy that is liable to cause said fines to react violently. There therefore exists a danger of such drums exploding and/or igniting during compacting. The invention proposes reducing and controlling, or even eliminating this danger.
SUMMARY OF THE INVENTION
The compacting method of the invention thus makes it possible, without danger of ignition and/or explosion to apply compression to reducing the volume of metal waste that is nevertheless liable to ignite and/or explode if subjected to such compression in a conventional manner.
Said method of the invention consists in exerting said compression on a container that contains said waste and that is saturated in inert gas.
As mentioned above, internal blanketing is performed so that during compacting the waste remains continuously under an inert atmosphere.
Said blanketing makes use of an inert gas. Solid or liquid blanketing is excluded because of the large quantities of inert materials required and because of the incompressibility of such materials.
The method of the invention may be implemented as follows.
The waste is loaded in bulk into a suitable container. During loading, an inert gas is injected into said container by bubbling so as to fill the voids generated by the expansion of said waste in said container with an inert atmosphere: both voids between pieces of waste and voids between waste and the walls of the container. Air, and thus oxygen, is expelled from said container in this way. Said container is saturated in inert gas. In theory, excess pressure is not generated inside said container since it is not useful. Said container is loaded under atmospheric pressure.
The container loaded in this way is fitted with a cover. It is necessary to ensure that such a cover is sealed only if the inert gas used is lighter than air.
Said container, once loaded and optionally sealed (hermetically plugged) is then inserted in a compacting skirt to be compacted therein under drive from a piston.
The diameter of the compacting skirt is naturally adapted to the dimensions of the container to be compacted. A limited amount of clearance--a few millimeters--is provided between said container and said skirt. The piston whose diameter is also adapted to the diameter of said skirt in application of the usual principles of press design then compresses said container, the waste, and the inert gas present inside the container.
Once the pressu
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Jacq Patrick
Masse Jean C.
Morlaes Isabelle
Compagnie Generale des Matieres Nucleaires
Mai Ngoclan
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