Glass manufacturing – Molten glass dispensing means – Discharge orifice below melt level
Patent
1997-01-10
1998-10-13
Silverman, Stanley S.
Glass manufacturing
Molten glass dispensing means
Discharge orifice below melt level
65122, 65126, 65329, 588 11, 588252, 588900, 376272, 222603, C03B 526
Patent
active
058206523
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a sealing system for the engagement of a container beneath a melting furnace. It more particularly applies to the pouring of molten radioactive glass into a container.
The reprocessing of nuclear fuels permits the separation of uranium, plutonium and fission products present in the fuel elements which have spent a time in a reactor.
A process has been developed which is known as vitrification for the inclusion of a certain number of radioactive elements and in particular fission products in a vitreous matrix.
The melting furnace is constituted by a metal container, known as a melting pot and which is heated by induction. Melting takes place at the same time in the melting pot of a glass frit and calcinates of fission products in order to obtain a glass, which is poured into stainless steel containers.
This process has become necessary because it permits the storage over a long period and with very great safety of highly radioactive products.
This operating procedure is widely used, described and demonstrated, particularly at the Marcoule nuclear centre (vitrification works) and more recently in reprocessing plants in La Hague.
In a more general manner, the installation has two levels separated by a slab. At the upper level the melting pot is placed in a furnace. At the lower level the container is positioned vertically with respect to the tapping hole of the pot. An opening in the slab permits pouring or tapping.
The installation must make it possible to strictly confine the molten glass, so that there is no spread of radioactivity, particularly at the time of pouring, into the ambient air and onto the outer wall of the container. It must permit the collection of all the gases, dust and particles given off. It must also permit the expansion of the container under the effect of the temperature rise occurring between the instant when the container is empty and the instant when it is filled with very hot glass.
To this end FR-A-2 616 000 proposed an apparatus permitting the pouring of molten radioactive glass into a container. This apparatus has a static or material seal between the various elements of the apparatus and a dynamic confinement by the extraction of air or gas around the molten glass being poured or tapped. This apparatus, shown in FIG. 1, leaves between the container neck and the pouring nozzle, an annular area opening onto the outside and by which the tapping gases and dust can leak to the outside. This leak is in principle fought by an air extraction. However, if said air extraction is not sufficiently effective, there can be a leak of radioactive dust and gases to the outside contaminating the outer wall of the container. The dynamic sealing apparatus according to the present invention obviates this disadvantage.
Thus, the present invention relates to a dynamic sealing apparatus for the engagement of a container beneath a melting pot containing a molten material, comprising a shell surrounding a nozzle, the nozzle being located in the axis of the container neck and permitting the pouring of material from the melting pot into the container, characterized in that the shell comprises means for tight connection to the nozzle, a base having a bearing surface for receiving a corresponding bearing surface on the container neck, and at least one bellows surrounding the nozzle and connecting the tight connection means to said base, the bellows making it possible to retract the shell along the axis of the nozzle, means for introducing a gas flow between said bearing surfaces being provided in order to permit the circulation of part of said flow towards the nozzle.
The gas flow introduction means can include at least one groove forming a labyrinth seal. Advantageously, the pressure drop in the leakage flow to the nozzle creates in the labyrinth seal an overpressure opposing the leakage to the outside of tapping gases.
The invention will be better understood and other advantages and features will become more clear from reading the following non-limitative description with
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patent: 4980091 (1990-12-01), Joutel
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Bernard Claude
Dollfus Jacques
Meline Fran.cedilla.ois
Roux Patrice
Compagnie Generale des Matieres Nucleaires
Silverman Stanley S.
Vincent Sean
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