Process for the preparation of a borosilicate glass containing nuclear waste
First Claim
1. A process for the preparation of a borosilicate glass containing nuclear waste, wherein The process comprises the steps of:
- (A) mixing1. an inactive borosilicate matrix prepared in an aqueous medium by mixing the following;
2. a silica-based gel precursor,3. a concentrated aqueous solution of a boron compound, and4. a concentrated aqueous solution of a vitrification adjuvant, with stirring at a high rate of shear, at a temperature of between 20°
C. and 80°
C. and at an acid pH, so as to form a gel;
(B) drying the gel to provide a dried gel;
(C) calcining the dried gel to form a calcined material;
(D) melting the calcinated material to form a melted glass;
(E) solidifying the melted glass; and
(F) adding an aqueous solution of nuclear waste or a calcinate thereof to the gel during one of the steps (B), (C) and (D) to form the borosilicate glass immobilizing the nuclear waste.
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Abstract
The invention relates to a process for the preparation of a borosilicate glass containing nuclear waste.
In this process, an inactive borosilicate matrix is prepared in an aqueous medium by mixing the following:
a silica-based gel precursor,
a concentrated aqueous solution of a boron compound, and
a concentrated aqeuous solution of the vitrification adjuvant,
in proportions corresponding to the composition of the final glass minus the waste, with stirring at a high rate of shear, at a temperature of between 20° C. and 80° C., preferably at 65°-70° C., at an acid pH, preferably a pH of between 2.5 and 3.5, so as to form a gelled solution, and the said matrix is heat-treated and the nuclear waste is added at any stage during the said treatment to form, by melting, the final borosilicate glass containing the said waste.
The process according to the invention is applied to the treatment of nuclear waste, especially to solutions of fission products.
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Citations
22 Claims
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1. A process for the preparation of a borosilicate glass containing nuclear waste, wherein The process comprises the steps of:
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(A) mixing 1. an inactive borosilicate matrix prepared in an aqueous medium by mixing the following; 2. a silica-based gel precursor, 3. a concentrated aqueous solution of a boron compound, and 4. a concentrated aqueous solution of a vitrification adjuvant, with stirring at a high rate of shear, at a temperature of between 20°
C. and 80°
C. and at an acid pH, so as to form a gel;(B) drying the gel to provide a dried gel; (C) calcining the dried gel to form a calcined material; (D) melting the calcinated material to form a melted glass; (E) solidifying the melted glass; and (F) adding an aqueous solution of nuclear waste or a calcinate thereof to the gel during one of the steps (B), (C) and (D) to form the borosilicate glass immobilizing the nuclear waste. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A process for immobilizing nuclear waste in the form of a liquid aqueous solution as a waste material, the process comprising the steps of:
A. simultaneously mixing glass-forming materials in an aqueous system, the ingredients comprising; 1. a silica gel precursor for forming silica in the final glass, the precursor being an aqueous suspension of colloidal silica; 2. a boron compound in an aqueous solution for forming boron oxide in the final glass; and - View Dependent Claims (15, 17, 19, 20, 21, 22)
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14. an aqueous solution of vitrification adjuvant, the mixing being done at an acid pH and a temperature of about 20°
- to 80°
C. to provide a gel solidified material;B. drying the resultant solidified material to provide a dried gel; C. calcining the dried gel of Step B at a temperature of about 300°
to 500°
C.;D. melting the calcined product of Step C to form a melted glass; E. solidifying the melted glass to form a borosilicate glass that encapsulates a nuclear waste material; and F. adding an aqueous solution of nuclear waste or a calcinate of the aqueous solution of the nuclear waste to the dried material of step B or the calcined product of step C or the melted product of step D to provide the immobilized waste product. - View Dependent Claims (16, 18)
- to 80°
Specification