Hazardous or toxic waste destruction or containment – Containment – Solidification – vitrification – or cementation
Reexamination Certificate
2000-05-04
2001-09-04
Bagnell, David (Department: 3673)
Hazardous or toxic waste destruction or containment
Containment
Solidification, vitrification, or cementation
Reexamination Certificate
active
06283908
ABSTRACT:
BACKGROUND OF THE INVENTION
The Advanced Vitrification System Canister Filling Process is a method for filling a canister with vitrified waste and glass making frit (hereinafter referred to as “waste”) starting with a waste that is cooler than its melting point. The present invention relates generally to a process for vitrifying waste, such as nuclear waste, in a disposable canister.
The disclosure of U.S. Pat. No. 5,678,237, which describes a canister and related method of in-situ vitrification of waste materials in a disposable canister, is incorporated herein by reference. The referenced disposable canister has an inner container and an outer container. The outer container serves as the traditional disposal container typically made of steel, which is insulated from an inner container, typically of made of graphite, by a layer of insulating material. The inner container serves as a crucible to melt a waste, contain the waste in its molten state, and serve as the disposal container for the vitrified product.
In the referenced patent, waste is added to the inner container and heated until it is melted. Then the waste is allowed to cool into a solid vitrified product. This process permits making a vitrified product occupying about 60% of the available container volume, due to the fact that the waste reduces in volume once it is melted. Increasing the fill volume of the container would permit minimizing the number of canisters required to dispose of a given volume of waste. Since reducing the number of canisters reduces the disposal costs, it is highly desirable to increase the fill volume.
Accordingly, this invention is a process for filling the container to a much higher level, that is, approaching 100% of the available volume.
BRIEF SUMMARY OF THE INVENTION
The Advanced Vitrification System Canister Filling Process is a method of filling a canister with vitrified waste starting with a waste that is cooler than its melting point. The invention may be used with any waste requiring isolation from the biosphere, such as high-level radioactive waste, low-level radioactive waste, toxic wastes, hazardous waste and hazardous and radioactive mixed waste. In the preferred embodiment, the process is utilized in a disposable canister consisting of outer and inner containers with thermal insulation therebetween. In its broadest potential, the process is utilized in a disposable canister consisting of a single container made of a material capable of being heated and serving and as a crucible for the melt. In the preferred embodiment, the method of filling a canister with vitrified waste starts with a waste that is cooler than its melting point. In the preferred embodiment, this waste is added incrementally, and more or less continuously, to a canister forming a column of waste capable of being separated into an upper zone and a lower zone. In its broadest use, the waste can be added discontinuously at any rate. The minimum height of the column is defined such that the waste in the lower zone can be dried and melted while maintaining the waste in the upper zone below its melting point. The maximum height of the column is such that the upper zone remains porous enough to permit evolved gases from the lower zone to flow through the upper zone and out of the canister. Heat is applied to the waste in the lower zone to first dry then to raise and maintain its temperature to a target temperature above the melting point of the waste. Then the heat is applied to a new lower zone above the melted waste and the process of adding, drying and melting the waste continues upward in the canister until the entire canister is filled and the entire contents are melted and maintained at the target temperature for the desired period. In the preferred embodiment, cooling of the melted waste takes place from the bottom of the canister to the top forming a vitrified product. In its broadest potential, cooling of the melted waste can take place over the entire surface of the canister.
REFERENCES:
patent: H152 (1986-11-01), Lampe
patent: 4221680 (1980-09-01), Hardwick et al.
patent: 4404129 (1983-09-01), Penberthy et al.
patent: 4581163 (1986-04-01), Meinnger et al.
patent: 5324485 (1994-06-01), White
patent: 5678237 (1997-10-01), Powell et al.
patent: 5947887 (1999-09-01), White et al.
Powell James R.
Reich Morris
Bagnell David
Kreck John
Radioactive Isolation Consortium, LLC
Ventre, Jr. Louis
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