Glass melting treatment method

Details Glass melting treatment method Glass melting treatment method

1995-02-23

1996-10-08

Mai, Ngoclan

Hazardous or toxic waste destruction or containment

Destruction or containment of radioactive waste

By fixation in stable solid media

651357, 651356, 373146, G21F 900

Patent

active

055641024

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to a method of subjecting a high-level radioactive liquid waste to a vitrification treatment by using cold-crucible induction melting.
2. Description of Related Art
A high-level radioactive liquid waste generated from a reprocessing plant is subjected at present to a vitrification or glassification treatment. The reasons why glass is used are because (1) glass is capable of uniformly solid-solving or dispersing almost all components of waste, (2) glass has an excellent stability, and (3) an industrial glass manufacturing method can be applied to manufacture the glass to be used.
In order to obtain a vitrified body, a glass melting furnace of a directly supplied current type has heretofore been used. Concretely speaking, a mixture of a high-level radioactive liquid waste and a raw glass material is charged into the melting furnace, and the glass is melted by applying heat thereto by using a preheater. When an electric current is supplied between electrodes disposed in the melting furnace, it flows into the molten glass, which is thereby heated to keep all of the materials charged into the furnace melted.
In the conventional melting technique, glass, an object material to be melted contacts directly a structural material (refractory furnace wall and crucible wall) of a melting apparatus under the object material melting temperature conditions. Therefore, the conventional technique poses important problems including the measures for preventing the high-temperature corrosion of the structural materials (i.e. provision of a margin for corrosion or replacement of the structural materials) and limitation on a melting temperature (i.e. setting the highest temperature, at which the strength of the structural materials can be secured, as an upper limit).


SUMMARY OF THE INVENTION

An object of the present invention is to provide a glass melting treatment method capable of simultaneously solving the problem of the high-temperature corrosion of the structural materials of a melting apparatus and the problem of the limitation of a melting operation temperature set on the basis of the heat resisting temperature of the structural materials of the melting apparatus.
To solve these problems, the present invention utilizes a cold crucible induction melting method. When a material to be melted is a metal in the cold-crucible induction melting method, a floating force working on the material occurs due to an operation of an electromagnetic field, so that the material can be melted without causing the same to contact a melting furnace body. Therefore, the characteristics of this method reside in its capability of minimizing the corrosion of the furnace body with the molten material in addition to its capability of melting a material having a high melting point. Accordingly, this method is utilized for melting special metals in the iron and steel industries at present. However, when the cold-crucible induction melting method is used, an object material to be melted necessarily has a conductivity, and this method cannot be utilized as it is for melting glass.
The glass melting treatment method according to the present invention comprises the steps of charging a radioactive liquid waste and a glass material into the interior of a melting furnace in a cold-crucible induction melting apparatus, inserting a conductor the melting point of which is higher than that of the glass material into the interior of the melting furnace, supplying a high-frequency current to a high-frequency coil in the melting apparatus so as to generate heat in the conductor and indirectly heat the glass material with the generated heat, withdrawing the conductor after a part of the glass material has been put in a molten state, and thereafter keeping the glass material as a whole in a molten state while maintaining the induction heating by the molten glass material. The conductor inserted into the melting furnace is, for example, a silicon carbide rod.
A mixture of a radioactive l

REFERENCES:
patent: 3205292 (1965-09-01), Descarsin
Preliminary Report of 1993 (31st) Spring Meeting of the Atomic Energy Society of Japan (Mar. 27-29, 1993); "H34 application of cold-crucible to melting of waste glass" and its English translation.

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