Contaminated soil restoration method

• US 5,045,240 A
• Filed: 05/01/1989
• Issued: 09/03/1991
• Est. Priority Date: 05/01/1989
• Status: Expired due to Term

• Current Assignee: Duratek Services Inc (Rockwell Holdco, Inc.)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Skriba, Michael C., Grant, David C.
• Primary Examiner(s): Stoll, Robert L.
• Assistant Examiner(s): ANTHONY, JOSEPH DAVID
• Application Number:
  US07/345,852
• Time in Patent Office: 855 Days
• Field of Search: 252/626, 252/628, 210/682, 210/688
• US Class Current: 588/7
• CPC Class Codes: B09C 1/02 Extraction using liquids, e.g. washing, leaching , flotation
• CPC Class Codes: G21F 9/28 Treating solids

Abstract

Waste material containing hazardous or radio-active species is treated by: separating a portion of the waste material and identifying the particle size range of the severely contaminated fraction by use of a sieving apparatus (6) and a contamination detection apparatus (8); passing the waste material (15) near a contamination detection apparatus (12) to identify the waste material that is contaminated and segregate that material by a diverter (17) to provide contaminated portion (19); passing the contaminated portion (19) into a fluidized bed apparatus (16) where an aqueous leaching solution (21), effective to leach soluble, contamination species, contacts the contaminated material at an upward velocity effective to remove the particle size range that is determined to contain the severely contaminated fraction of the waste material, to provide a severely contaminated effluent slurry (24); and removing the leach solution from the slurry in a dewatering apparatus (26) to provide a solution (27) containing solubilized, severely contaminated species.

Claims

1. A method of treating waste material contaminated with soluble radioactive species comprising the steps:

(1) providing waste material containing soluble radioactive species and separating that portion of the waste material found to be contaminated, to provide contaminated waste material;

(2) crushing the contaminated waste material so that it has a particle size below 420 micrometers, determining the contaminant, the contaminated waste material density, and identifying the particle size range of the most severely contaminated fraction of the contaminated waste material by separation into a plurality of particle size fractions and scanning each fraction for radioactivity or chemically analyzing each fraction;

(3) passing the contaminated waste material, having a known density, into a fluidized bed apparatus where an aqueous leach solution, having a chemical composition effective to leach soluble contaminants present in the contaminated waste material, contacts the contaminated waste material at an upward velocity effective to entrain and remove, at the top of the apparatus, particles including the particle size range that is determined to contain the most severely contaminated fraction of the contaminated waste material, to provide a severely contaminated, top effluent slurry containing solubilized, severely contaminated species, and a bottom effluent slurry containing disposable, cleaned waste where each slurry contains the aqueous leach solution;

(4) removing the leach solution from the severely contaminated effluent slurry, to provide aqueous leach solution containing solubilized, severely contaminated species, and cleaned solids waste; and

(5) passing the aqueous leach solution from step (4) through an ion removal apparatus effective to remove the solubilized, severely contaminated species from the aqueous leach solution, to provide cleaned, aqueous leach solution.

2. The method of claim 1, where the contaminated waste contains radioactive species which contains at least one of radioactive radium, radioactive uranium, and radioactive thorium present at concentrations of over 5 picocuries/gram, and where the ion removal apparatus is selected from an ion exchange column containing ion exchange material or a precipitator.

3. The method of claim 1, where, after step (4), water is added to the solid waste, to provide a mixture of residual contaminated water and cleaned waste material, where the contaminated water is passed through the ion removal apparatus in step (5), and the cleaned waste is dried.

4. The method of claim 1, where the cleaned, aqueous leach solution from step (5) is passed through a reverse osmosis apparatus, to provide:

(a) cleaned, concentrated, aqueous leach solution having a chemical composition effective to leach contaminants present in the contaminated waste material and identified in step (2), which aqueous leach solution is passed to step (3); and

(b) purified water, which is added to the solids waste segregated in step (4).

5. The method of claim 1, where the contaminated waste material contains radioactive radium, and the aqueous leaching solution used in step (3) is selected from the group consisting of hydrochloric acid, nitric acid, sodium carbonate, sodium chloride, and mixtures thereof.

6. The method of claim 1, where the contaminated waste material contains radioactive uranium, and the aqueous leaching solution used in step (3) is selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, sodium carbonate, sodium chloride, and mixtures thereof.

7. The method of claim 1, where the contaminated waste material contains radioactive thorium, and the aqueous leaching solution used in step (3) is selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, and mixtures thereof.

8. The method of claim 1, where the contaminated waste material passed into the fluidized bed apparatus in step (3) has a density of from 1.4 g/ml to 3.2 g/ml, the upward velocity of the leaching solution is from 5 gpm/ft² to 30 gpm/ft², and where, in step (5), an ion exchange column is used to provide cleaned aqueous leach solution.

9. The method of claim 1, where the contaminated waste contains at least one of radioactive radium and radioactive uranium, the radioactive material is passed through the fluidized bed apparatus in step (3) and has a particle size below 420 micrometers, and an ion exchange column is used in step (5) to provide cleaned aqueous leach solution.