Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to a method of tightly sealing
a ceramic container for the long-term storage of radioactive
materials such as irradiated nuclear reactor Euel elements.
The invention also relates to such a container.
For the long-term storage or the direct terminal
storage oE irradiated nuclear fuels, cemaric containers have
also been suggested in addition to metal containers. These
ceramic containers have the required strength and maintain
the needed chemical stability over the long period of time
required for the storage of such materials.
According to the present invention there is
provided a method of loading and tightly sealing a ceramic
container in a hot cell of a nuclear facility for the
long-term storage of radioactive materials, the container
comprising a ceramic vessel having an opening at one end
thereof, and a ceramic cover adapted to fit on the vessel to
close the opening, an upper end portion of the vessel and
the peripheral portion of the cover defining respective
joint surfaces which are mutually adjacent and conjointly
define a partition interface between the vessel and the
cover when the cover is sea-ted on said vessel, the method
comprising the steps of:
- placing the vessel, the cover and a solder form
piece in the hot cell;
- loading the vessel with the radioactive materials;
- applying heat to the partition interface and to
said form piece sandwiched between said vessel and said cover
while said container is still in the hot cell causing said
form piece to flow thereby wetting said joint surfaces.
With the method of the invention, it has been shown
that a good joint is achieved between the cover and the
vessel of the container. Because of the invention, a simple
technique is made possible for closing the container in a
so-called hot cell.
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According to one aspect of the present invention,
there is provided a method of loading and tightly sealing a
ceramic container in a hot cell of a nuclear facility for the
long-term storage of radioactive materials such as irradiated
nuclear reactor fuel elements, the container including: a
ceramic vessel having an opening at one end thereof; and, a
ceramic cover adapted to fit on the vessel to close the open-
ing; the vessel having a base and a wall extending upwardly
from said base, the wall terminating in an upper end portion
defining the opening;.- the cover having a peripheral portion
for engaging the vessel; the upperend portion of the
vessel and the peripheral portion of the cover defining
respective joint surfaces, said joint surfaces being mutually
adjacent and conjoi.ntly defining a partition interface between
said vessel and said cover when said cover is seated on said
vessel, the method comprising the steps of:
placing the vessel, the cover and a solder form
piece in the hot cell;
loading the vessel with the radioactive materials;
placing the solder form piece between the joint
surfaces wnile the vessel and the cover are in the hot cell;
and,
applying heat to the partition interface and said
form piece while said container is still in the hot cell and
causing said form piece to flow thereby wetting said joint
surfaces.
According to another preferred embodiment there is
provided a method of loading and sealing, in a hot cell of
a nuclear facility, a ceramic container for the long-term
storage of radioactive materials such as irradiated nuclear
reactor fuel elements, the container including a ceramic
vessel having a base and a wall extending upwardly from
said base, the wall terminating in an upper end portion;
and, a ceramic cover having a peripheral portion for engaging
the vessel; the upper end portion of the vessel and the
peripheral portion of the cover defining respective joint
surfaces, said joint surfaces being mutually adjacent and
conjointly defining a partition interface between said vessel
and said cover when said cover is seated on said vessel, the
method comprising the steps of:
placing the container and a preformed annular solder
piece in the hot cell;
loading the ceramic vessel with the radioactive
l material to be stored therein;
placing the preformed annular solder piece on said
joint surface of said ceramic vessel while the vessel and -the
cover are in the hot cell
placing the ceramic cover upon said vessel to sand--
wich said solder piece between said joint surfaces;
applying heat to the partition interface and to
said solder piece whi.le the container is still in the hot cell
and causing said form piece to flow thereby wetting said
joint surfaces; and,
discontinuing the application of said heat thereby
permitting said partition interface to cool so that a seal-
tight joint is formed between said vessel and said cover.
In this preferred embodiment the solder form
pieces are made to have the profile required for accommoda-ting
the container and are placed between the joint surfaces. By
means of an appropriate heating apparatus, the temperature
is raised until the solder runs and spreads in the area of
the joint surfaces whereby joining forces become effective
between the parts being joined by the solder. This embodiment
of the method of the invention is especially suited for placing
the metal solder piece on the vessel in the hot cell after
the latter has been loaded with the nuclear fuel material.
According to another preferred embodiment, there
is provided a method of loading and sealing, in a hot cell,
a container for the long-term storage o radioactive materials
such as irradiated nuclear reactor fuel elements, the container
including a vessel having a base and a wall extending upwardly
from said base, the wall terminating in an upper end portion;
the cover having a peripheral portion for engaging the vessel;
the upper end portion of the vessel and the peripheral portion
of the cover defining respective joint surfaces, said joint
surfaces being mutually adjacent and defining the partition
interface between said vessel and said cover when said cover
is seated on said vessel, the method comprising the steps of:
precoating said respective joint surfaces of said
vessel and said cover with metal solder outside of the hot
cell;
placing said vessel and said cover in the hot cell;
loading said vessel in the hot cell with the radio-
active material to be stored;
placing said cover on said vessel so as -to cause
said precoated joint surfaces to be in contact with each
other;
applying heat to the metal solder coatings on said
joint surfaces thereby causing said coatings to melt; and
discontinuing the application of said heat thereby
permitting said solder to cool so that a seal-tight joint is
formed between said vessel and said cover.
In this last-mentioned preferred embodiment, the
joint surfaces are already precoated outside of the hot cell
with a metal layer of solder. During the operation of closing
the container in the hot cell, only a short-time melting of
the solder is required. The basic material of which the
vessel and container are made do not have to be heated to
the temperature of solder in this method embodiment of the
invention. This relatively simple melting of the solder
coating can be achieved with a simple inductive warming of
the solder coatings.
- 3a -
According to the present invention there is also
provided a container for the long-term storage of radioactive
comprising:
- a ceramic vessel having an opening at one end
thereof;
- a ceramic cover adapted to fit on the vessel to
close the opening;
- an upper end portion of the vessel and a
peripheral portion of the cover defining respective joint
surfaces, said joint surfaces being mutually adjacent and
conjointly defining a partition interface between said vessel
and said cover when said cover is seated on said vessel,
- a solder form piece being disposed at the inter-
face of said cover and said vessel.
Preferred embodiments of the invention will now be
described as examples, without limitative manner, with refer-
ence to the drawing wherein:
FIG. 1 is an elevation view, in section, illustra-ting
a ceramic container of the invention which is closed and
tightly sealed with respect to the ambient pursuant to a
method according to one embodiment of the invention; and
FIG. 2 is an elevation view, in section, showing
a ceramic container wherein the joint surfaces have been
precoated pursuant to another embodiment of the method
according to the invention.
The ceramic container shown in FIG. l includes a
vessel l of cylindrical configuration and open at one end.
Reference numeral 2 designates the cover of the container.
An annular form piece 3 made of metal solder is sandwiched
between the vessel l and the cover 2. The joint surfaces
4 and 5 of the vessel l and cover 2, respectively, are
configured so as to have a stepped profile. The metal
solder form piece 3 is
- 3b -
formed to correspond -to this stepped profile.
The container is loaded with irradiated nuclear fuel
ma-terial in a shielded room which is a so-called hot cell.
This loading operation is conducted with remotely-controlled
apparatus. When the vessel 1 is loaded wi-th irradiated nuclear
fuel materials, the annular or ring-shaped solder form piece 3
is placed upon the joint surface 4 of vessel 1. The cover 2
has a joint surface 5 formed to correspond to that of the joint
surface 4 of the vessel. AEter placing the form piece 3 in
position, the cover 2 is placed upon the ring-shaped solder
form piece 3 so that the latter is sandwiched between the
vessel and cover.
By means of an appropriate heating device (not shown), the
solder form piece 3 as well as the vessel 1 and cover 2 are
heated in the area of the par-tition interface to the extent
that the solder melts and wets the joint surfaces whereafter
connecting forces between the vessel and cover become effective.
The vessel 1 and cover 2 can be made of A12o3. TiPd -
solder is used as the metal solder because titanium has a high
affinity to oxygen.
FIG. 2 shows how the vessel 11 and cover 12 of a ceramic
container can be precoated with metal solder at their
respective joint surfaces 14 and 15. According to another
embodiment of a method of the invention, these precoatings 16
and 17 are applied outside of the hot cell. In this way, the
vessel and cover are equipped with the solder coa-tings when
they are brought into the hot cell thereby reducing the steps
which have to be performed in this facility. This is a very
substantial advantage because operations in a hot cell such as
placing pieces of a container assembly in position must be
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performed with remotely-controlled apparatus. Thus, in this
embodiment of the method of the invention, the step of placing
a solder form piece in position is eliminated.
After the vessel is filled with radioactive waste in the
hot cell, heat is applied inductively to only the solder
coatings 16 and 17 and only for a time long enough to cause the
solder to melt. The induction heating device is shown
schematically in FIG. and is identified therein by reference
numeral 18. With this embodiment, the ceramic material of the
vessel 11 and cover 12 does not have to be raised to the
soldering temperature.
It is understood that the foregoing description is that of
the preferred embodiments of the invention and that various
changes and modifications may be made thereto without departing
from the spirit and scope of the invention, as defined in the
appended claims.
