Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to a pe~manent storage
container for heat~producing radioactive materials comprising
a basic body and a casing of corrosion-resistant material
enclosing said basic body on all sides and spaced therefrom.
For the permanent storage of heak-producing radioac-
tive materials, as for example, burned-off fuel elements from
nuclear power plants or waste from plants for reprocessing
burned-off fuel elements containers in which the radioactive
substances are safely enclosed, from which the heat produced
can reliably be removed at any time and which are critically
safe are used.
Thick-walled containers, some of which are inter-
nally lined with re~ined steel are usually used. When the
containers are stored below ground, for example, in abandoned
mines, the container walls must be able to absorb the rock
pressure and they must be corrosion-resistant.
For economy multilayer containers are used. For the
basic body a heat-resisting inexpensive material is used.
This material does not have to be corrosion-resistant since it
does not come in contact with corrosive media. The container
is so dimensioned that it resists rock pressure. It does not
have to be gas-tight so that the bottom and the lid can be
screwed in.
For example, suitable and heat-resistant types o~
fine-grained steel are suitable as materials for the baslc
hody. ~part from metallic materials for the basic body con-
crete containers can also be used.
For the external layer, or for the outer casing of
the containers corrosion-resistant materials are used. In
salt mines in which the o~ccurrence of quinary liquors must be
considered at least theoretically, high-alloyed steel, as for
example, Hastelloy, or steel based on zirconium or titanium,
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is suitable.
The thickness of these sheet metals is so selecte~
that they resist the expected corrosion for the d~ra~ion of
the storage and also withstand the internal pressur~ since the
basic body is not gas-tight. After loading the container this
internal pressure builds up due to heating by the stored heat-
producing radioactive material.
The maximum internal pressure building up determines
the planning o~ the thickness of the external casing, i.e.,
because of the internal pressure the corrosion-preventing cas-
ing must be substantially thicker than would be necessary
merely for reasons of protection against corrosion and tight-
ness alone. This applies particularly to flat bottoms and
lids which, for the dimensions to be considered, must be over
proportionally thicker than the cylindrical casings of other
conventional transport and storage containers.
Since the material for the corrosion-preventing cas-
ing is extreme].y costly, these designs are very expensive.
For reasons of production technique it is difficult -to so ~oin
the sheets of the corrosion-preventing casing to the thicker
bottom and lid sheets that stability and tightness are
assured.
Therefore, the present invention provides a perma-
nent storage container for heat-producing radioactive mate-
rials comprising a basic body and a gas-tight casing of corro-
sion-resistant material enclosing said basic body on all sides
and spaced therefrom. The thickness of the gas~tight casing
is designed only for corrosion resistance. The container is
easy to produce and is capable of being tested.
According to the present invention this is achieved
by the casing being connected to the basic body via anchors
made of the same material as the casiny.
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In particularly ~avourable embodiments the anchors
are scr~wed into the basic body and welded to the casing. Ik
is favourable when anchor and casing are made of the same
material.
The present invention will be further illustrated
with reference to the accompanying diagramma-tic drawings, in
which:-
Fig. 1 is a vertical section through a transportand/or storage container according to one embodiment of the
present invention; and
Fig.s 2 to 4 are details of Fig. 1 of various
anchors useful in the container.
Referring to the drawings, the permanent storage
container comprises a basic body (1) with bottom (2) and lid
(3) made of an inexpensive metallic material. The basic body
(1) is disposed in a shielding container (6). The storage
container contains radioactive material (7), for example,
irradiated fuel elements from nuclear reactors or radioactive
wastes from reprocessing plants. sasic body (1), bottom (2)
and lid (3) are surrounded by a gas-tight casing (4) made o~
corrosion-resistant metallic ma-terial. The casing (4) fits
the baslc body ~1) relatively tightly. Therefore, the space
(8) between the casing (4) and basic body (1) and bottom (2)
and lid (3) is ver~ small. This space can be filled with
helium or any other gas to test the tightness of welding seams
in the casing (4) and in the region of lid or bottom. The
casing (4) is connected to the basic body (1) including lid
and bottom regions by means of anchors (5). The numbers and
distribution of the anchors (5) is adapted to the design
requirements in each case. The anchors (5) are protected from
ground corrosion and made of the same material as the casing
(4). They secure the casing (4) against buckling at increased
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internal pressure caused by the stored heat-producing radioac-
tive material. The.
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thicknes~ o~ the casing L4~ is dimensioned with a yieW to
saving material but primarily with re~ard to a possibl~ ex-
pected maximal corrosion att~ck. For this purpose conical
anchors (9) CFiguxe 2~ can be used or bolt~like anchors (10)
(Figure 3) which are provided with one or several steps can
also be used. ~owever, these anchors (9, 10) penetrate the
basic body (1). Therefore, it is favourable when the anchors
are screwed into the basic bod~ as screw anchors (11)
(Figure 4) since in this manner the basic body (1) does not
have to be pierced. This is also the case when the anchors
(S) are let in from the outs~de in the manner of a spreading
dowel or bayonet holder. The corrosion-resistant casing (4)
is secured to the anchors (5) thus let into basic body (1),
for example, by soldering or- riveting. It has been found that
the welding of the anchor (5) to the casing (~) is particularly
favourable. Depending on the requirements the anchor periphery
can be flus~l with the external surface of the casing or set
bac~. When required it is also possible to screw anchor (5)
and casing (~) to each other. The anchor (5) can also be
composed of several materials if this has a favourable effect
on the securing in the basic body.
With the present invention it is surprisingly
possible to minimize the thickness of the corrosion-resistant
casing while saving material and costs but also under the as-
pect of a built-up of internal pressure, taking into account
the actual requirements. The mounting of the casing and of
the anchors is simple and pxoblems concerning metallic connec-
tions do not exist when suitable metal combinations are selected.
Further~ore, all the welding seams ox other kinds of connec-
tiQns can be satisfac~orily tested.
