Vitrified chemically bonded phosphate ceramics for immobilization of radioisotopes

Patent metadata

Field	Value
Publication number	US-9305672-B2
Application number	US-201414291980-A
Country	US
Kind code	B2
Filing date	May 30, 2014
Priority date	May 30, 2014
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

A method of immobilizing a radioisotope and vitrified chemically bonded phosphate ceramic (CBPC) articles formed by the method are described. The method comprises combining a radioisotope-containing material, MgO, a source of phosphate, and optionally, a reducing agent, in water at a temperature of less than 100° C. to form a slurry; curing the slurry to form a solid intermediate CBPC article comprising the radioisotope therefrom; comminuting the intermediate CBPC article, mixing the comminuted material with glass frits, and heating the mixture at a temperature in the range of about 900 to about 1500° C. to form a vitrified CBPC article comprising the radioisotope immobilized therein.

First claim

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of immobilizing a radioisotope comprising the steps of:
(a) combining a radioisotope-containing material, MgO, a source of phosphate, and optionally, a reducing agent, in water at a temperature of less than 100° C. to form a slurry;
(b) curing the slurry to form an intermediate chemically bonded phosphate ceramic (CBPC) article comprising the waste material therefrom;
(c) comminuting the intermediate ceramic into fine particles;
(d) mixing the fine particles of CBPC with borosilicate glass frits; and
(e) heating the mixture resulting from step (d) at a temperature in the range of about 900 to about 1500° C. to form a vitrified CBPC article comprising the radioisotope immobilized therein.

2. The method of claim 1 wherein the radioisotope-containing material comprises at least one radioisotope selected from the group consisting of a radioisotope of Cs, Sr, and I.

3. The method of claim 1 wherein the radioisotope-containing material comprises a radioisotope of Tc and the slurry comprises a reducing agent for reducing Tc(VII) to Tc(IV).

4. The method of claim 3 wherein the reducing agent comprises Sn(II).

5. The method of claim 1 wherein the radioisotope-containing material comprises a solid material, a liquid material, or a combination thereof.

6. The method of claim 1 wherein the radioisotope-containing material comprises a radioactive waste sludge.

7. The method of claim 1 wherein the step of heating is performed at a temperature in the range of about 1100 to about 1300° C.

8. The method of claim 1 wherein the source of phosphate comprises KH 2 PO 4 .

9. The method of claim 1 wherein the slurry is prepared with a molar ratio of MgO-to-KH 2 PO 4 -to-water of about 1:1:5.

10. The method of claim 1 wherein the slurry further comprises one or more additional an oxide or salt of an element selected from the group consisting of an alkaline earth metal, a transition metal, a main group metal, a lanthanide, an actinide, and a metalloid.

11. The method of claim 1 wherein the slurry further comprises one or more extenders selected from fly ash, wollastonite, and silica sand.

Assignees

• Uchicago Argonne Llc

Inventors

• Wagh Arun S

Classifications

• C03C4/0042

  for glass comprising or including particular isotopes · CPC title

• C03C2214/20

  Glass-ceramics matrix · CPC title

• G21F9/162

  in an inorganic matrix, e.g. clays, zeolites · CPC title

• C03C2214/14

  Waste material, e.g. to be disposed of · CPC title

• C04B35/447

  based on phosphates {, e.g. hydroxyapatite} · CPC title