Treatment of solid wastes

• US 5,640,703 A
• Filed: 01/29/1996
• Issued: 06/17/1997
• Est. Priority Date: 04/18/1994
• Status: Expired due to Term

• Current Assignee: Nuclear Decommissioning Authority
• Original Assignee: British Nuclear Technology
• Inventors: Brierley, Kenneth Walter, Ellison, Michael Robert
• Primary Examiner(s): MAI, NGOCLAN THI
• Application Number:
  US08/593,479
• Time in Patent Office: 505 Days
• Field of Search: 588/1, 134/3, 134/10, 134/22.17, 134/22.19, 134/26, 423/20
• US Class Current: 588/1
• CPC Class Codes: G21F 9/30 Processing separating different isotopes of the same chemical element B01D59/00

Abstract

A process for the treatment of solid waste material which is or is suspected to be contaminated with plutonium or compounds thereof with or without other hazardous contaminants, which process includes: contacting the said material with and thereby dissolving contaminants as complexes by a liquid medium which comprises Solution X which comprises an aqueous solution which is free of ingredients which are naturally degradable to non-toxic products with or without mild physical assistance such as heat or ultra-violet radiation, said solution comprising:

(a) carbonated water;

(b) a conditioning agent; and

(c) a complexing agent which comprises the anion of a single or multiple carboxylic acid species having from 2 to 6 carbon atoms in each carboxylic acid species;

and separating the liquid medium from the waste material and recovering the dissolved contaminants from the liquid medium and wherein the step of contacting the waste material with the said liquid medium is preceded by a step of contacting the waste material with a dissolver solution of non-neutral pH different from the pH of the said liquid medium whereby solid contaminant particles are washed from the waste material and/or dissolved as simple ions in the dissolver solution.

Claims

1. A process for the treatment of solid waste material which is or is suspected to be contaminated with plutonium or compounds thereof with or without other hazardous contaminants, which process includes the steps of:

(1) contacting the said material with and thereby complexing the contaminants with a liquid medium which comprises an aqueous solution of (a) carbonated water;

(b) a conditioning agent; and

(c) a complexing agent which comprises the anion of a single or multiple carboxylic acid species having from 2 to 6 carbon atoms in each carboxylic acid species;

wherein said aqueous solution is free of ingredients which are naturally degradable to non-toxic products with or without mild physical assistance; and

(2) separating the liquid medium from the waste material; and

(3) recovering the complexed contaminants from the liquid medium, wherein prior to step (1) the waste material is contacted with an aqueous washing solution of non-neutral pH different from the pH of the said liquid medium whereby solid contaminant particles are washed from the waste material.

2. A process as in claim 1 and wherein the aqueous washing solution comprises a strongly acidic or a strongly alkaline washing solution having a molar acid or alkali concentration greater than about 0.1M.

3. A process as in claim 2 and wherein the reagent concentration of the aqueous solution used in step (1) is less than 0.01M.

4. A process as in claim 1 and wherein at least 90 percent of the plutonium content of the solid waste material is dislodged by the washing solution, the remaining plutonium content being substantially complexed by treatment with the Solution X.

5. A process as in claim 1 wherein the solid waste material is washed with water prior to or after contact with the washing solution.

6. A process as in claim 5 and wherein the waste material is contacted with an aqueous solution or vapor phase organic solvent prior to contact with the washing solution.

7. A process as in claim 1 and wherein the waste material is sorted and shredded or otherwise reduced in size prior to contacting by the washing solution.

8. A process as in claim 1 and wherein the liquid contacting stages are operated as a continuous treatment processes in which solid waste material being treated is passed from one stage to the next.

9. A process as in claim 8 and wherein the process includes the steps of feeding a feedstock of the waste material through a series of treatment stages in which it is contacted with a washing liquid and then separated from the washing liquid, the washing liquid removed from at least one of the stages being passed to the stage previously encountered by the feedstock whereby the feedstock and washing liquid are passed in countercurrent fashion with respect to adjacent stages, at least one of the treatment stages including the step of contacting with the dispersing solution and at least one more of the treatment stages including the step of contacting with the liquid medium used in step (1).

10. A process as in claim 9 and wherein the treatment stages are preceded by another liquid treatment stage in which the feedstock is treated by another extractant solution comprising a surfactant wash organic solvent.