Cermet high level waste forms

Abstract

A system and method for stabilizing fission products in a cermet for long term storage. The method includes forming a metal oxide precipitate, combining the metal oxide precipitate with an undissolved solid, and densifying the combined metal oxide precipitate and the undissolved solid to provide a cermet having a ceramic dispersed phase and a metallic matrix phase, wherein the metallic matrix phase includes metallic content from the undissolved solid. The undissolved solid can include fission product metals from the reprocessing of irradiated nuclear fuel. The cermet waste loading can be greater than approximately 30 percent, reducing waste volume by 50 percent or more when compared to baseline glassified articles.

Description

[0001]This invention was made with government support under Contract No. DE-ACO5-000R22725 awarded by the U.S. Department of Energy. The government has certain rights in the invention.BACKGROUND OF THE INVENTION[0002]The present invention relates to cermets, and more particularly, cermets for high level waste containment.[0003]A number of nuclear processes generate waste with high levels of radioactive decay. These by-products must generally be stored or disposed in a manner that limits their impact on the surrounding environment. Current storage methods include the fixation of waste in glass. For example, one method includes dissolving used fuel components in nitric acid, removing recyclable components, evaporating the residual waste solution, calcining the resulting solids to produce an oxide mixture, heating the oxide mixture with borosilicate glass frit to obtain a melt, and solidifying the melt in a pelletized body. An accumulation of pelletized glass can be surface stored for ...

AI Technical Summary

Benefits of technology

[0010]The present invention provides a cermet having improved properties over glassified waste forms and known cermets. The resulting cermet includes a ceramic phase having low leachability and a metal matrix phase providing improved strength and high thermal conductivity. The disclosed system and method facilitate cost reductions by integrating metal waste and oxide waste into one, efficient waste stream, with little or no additives to tailor the ceramic or metal phases of the resulting cermet.

Problems solved by technology

A number of nuclear processes generate waste with high levels of radioactive decay.

Despite its acceptance, however, the above method suffers from a number of drawbacks.

For example, glass can have less than 30% waste loading, resulting in undesirably large quantities of glass for a given quantity of fission product.

In addition, glass can have poor long-term resistance to leaching, and component materials and equipment can suffer from high levels of corrosion throughout the manufacture of the pelletized glass body.

Despite their advantages, however, conventional cermets have yet to receive widespread acceptance in the reprocessing of used nuclear fuel.

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