Hepa filter dissolution process
AssigneeThe United States of America as represented by the United States Department of Energy
InventorsKen N. Brewer, James A. Murphy
Life of this patent
Estimating the term…
Abstract
A process for dissolution of spent high efficiency particulate air (HEPA) filters and then combining the complexed filter solution with other radioactive wastes prior to calcining the mixed and blended waste feed. The process is an alternate to a prior method of acid leaching the spent filters which is an inefficient method of treating spent HEPA filters for disposal.
Claims26
A process for reducing the volume of a contaminated HEPA filter comprising dissolving the HEPA filter media in hydrofluoric acid solution of a strength required to have a minimal amount of free hydrofluoric acid at the end of the dissolution to provide that filter dissolution is complete, silica gel (SiO.sub.2) is minimized, and silicon fluoride (SiF.sub.4) is maximized.
The process of claim wherein the dissolution chemical reaction equations are:
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A process for dissolving and calcining a radioactive contaminated HEPA filter comprising:
- a. baking the HEPA filter;
- b. dissolving the HEPA filter media in a hydrofluoric (HF) acid solution of a strength required to minimize formation of both silica gel and precipitates, forming an HF/filter solution;
- c. complexing the HF/filter solution with an aluminum nitrate (AlNO.sub.3) solution forming a complexed filter waste solution;
- d. mixing the complexed filter waste solution with a radioactive solution forming a complexed filter/radioactive waste solution;
- e. performing a second complexing on the complexed filter/radioactive waste solution by addition of calcium nitrate (Ca(NO.sub.3).sub.2), forming a blended feed solution;
- and then
- f. calcining the blended feed solution, thereby forming a calcined particulate and fines.
A process for dissolving and calcining a radioactive contaminated HEPA filter comprising:
- a. baking the HEPA filter;
- b. dissolving the HEPA filter media in a hydrofluoric (HF) acid solution in an amount that gives a molar ratio of fluoride-to-silicon of about 7:1, forming an HF/filter solution;
- c. complexing the HF/filter solution with an aluminum nitrate (AlNO.sub.3) solution forming a complexed filter waste solution;
- d. mixing the complexed filter waste solution with a radioactive solution forming a complexed filter/radioactive waste solution;
- e. performing a second complexing on the complexed filter/radioactive waste solution by addition of calcium nitrate (Ca(NO.sub.3).sub.2), forming a blended feed solution;
- and then
- f. calcining the blended feed solution, thereby forming a calcined particulate and fines.
A process for dissolving and calcining a radioactive contaminated HEPA filter comprising:
- a. baking the HEPA filter at about 550.degree. C. for about 3 hours;
- b. dissolving the HEPA filter media in a hydrofluoric (HF) acid solution in an amount that gives a molar ratio of fluoride-to-silicon of about 7:1, forming an HF/filter solution;
- c. complexing the HF/filter solution with an amount of 2.2 molar aluminum nitrate (AlNO.sub.3) solution that gives a fluoride-to-aluminum molar ratio of between 20:1 and 40:1, forming a complexed filter waste solution;
- d. mixing the complexed filter waste solution with a radioactive solution forming a complexed filter/radioactive waste solution;
- e. performing a second complexing on the complexed filter/radioactive waste solution by addition of an amount of calcium nitrate (Ca(NO.sub.3).sub.2), to obtain a calcium-to-fluoride molar ratio of about 0.7:1, forming a blended feed solution;
- and then
- f. calcining the blended feed solution, thereby forming a calcined particulate and fines.
Dependencies are inferred from the claim text.