US 5,961,679 AGranted

Recovery of fissile materials from nuclear wastes

AssigneeU. S. Department of Energy

InventorCharles W. Forsberg

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Abstract

A process for recovering fissile materials such as uranium, and plutonium, and rare earth elements, from complex waste feed material, and converting the remaining wastes into a waste glass suitable for storage or disposal. The waste feed is mixed with a dissolution glass formed of lead oxide and boron oxide resulting in oxidation, dehalogenation, and dissolution of metal oxides. Carbon is added to remove lead oxide, and a boron oxide fusion melt is produced. The fusion melt is essentially devoid of organic materials and halogens, and is easily and rapidly dissolved in nitric acid. After dissolution, uranium, plutonium and rare earth elements are separated from the acid and recovered by processes such as PUREX or ion exchange. The remaining acid waste stream is vitrified to produce a waste glass suitable for storage or disposal. Potential waste feed materials include plutonium scrap and residue, miscellaneous spent nuclear fuel, and uranium fissile wastes. The initial feed materials may contain mixtures of metals, ceramics, amorphous solids, halides, organic material and other carbon-containing material.

Claims20

Dependent claims

A method for the conversion of radioactive waste and other waste material into glass comprising the steps of:

a) providing a bath of molten B.sub.2 O.sub.3 and PbO;
b) forming a molten dissolution glass comprising xPbO:B.sub.2 O.sub.3 ;
c) adding said waste to said dissolution glass to form a molten glass/waste mixture, wherein metals and metal compounds in said waste are oxidized to yield metal oxides, molten lead is formed, noble metals are dissolved in said lead, and halogens are converted to lead halides which are gases at the temperature of the molten mixture;
d) separating said gases from said molten mixture;
e) contacting said gases with an aqueous scrubber solution of an alkali metal hydroxide to yield a soluble alkali metal halide and a lead-containing precipitate;
f) separating said molten lead, containing dissolved noble metals, from said molten mixture;
g) adding carbon to said molten mixture to remove lead oxide by converting it to lead and carbon oxides;
h) removing said carbon oxides and said lead from said molten mixture to yield a glassy boron oxide fusion melt containing dissolved metal oxides;
i) adding said fusion melt to an aqueous nitric acid solution wherein said fusion melt, including said metal oxides in said fusion melt, are rapidly and easily dissolved in said acid solution;
j) separating and recovering metals from said acid solution;
and
k) converting said acid solution into a waste glass.

9 more elements

Dependencies are inferred from the claim text.