Westinghouse Electric Corporation

Other

Dwight F Goad

Thomas S Snyder

David C Grant

Gregory F Boris

Laura J Ayers

Carol Lynn Kelly

Kevin D Robbins

Martin Brownstein

James T Hallman

Chuck A Cooney

Lori West

Darrell B Watkins

The present invention provides methods and processes for immobilizing and solidifying harmful heavy metal and radioactive species within a waste material. The processes of the present invention are also particularly advantageous for immobilizing and solidifying nitrate compounds with a waste material. One embodiment of the present invention is a method that can be carried out by admixing the waste material with cement and a complexant compound to form a grout admixture. Preferably, the complexant compound is an iron compound that can form a hydrated iron oxide in the presence of an aqueous solution. This grout admixture is then allowed to cure and solidify. The grout admixture is placed within a suitable containment vessel for final storage and disposal.

Process for solidification and immobilization of harmful waste species

A novel method for decontaminating radio-contaminated nickel comprising, in an electrorefining cell having a semi-permeable membrane, cathodically depositing substantially contaminant-free nickel from an alkaline solution containing electrolyte, nickel ions, and radioactive ions. Preferably, the electrolyte solution is ammonium sulfate maintained at a pH of least about 10 (as measured at cell temperature). The electrorefining methods of the invention eliminate the need for separate dissolving and plating tanks, and may be operated by a single power source. These methods are particularly useful for remediating nickel contaminated by technetium, uranium and actinide metals.

Electrochemical decontamination of radioactive metals by alkaline

Technetium-contaminated nickel is decontaminated by electrolytically dissolving nickel having a gross beta activity of at least about 74 Bq in a sulfuric acid solution having a pH between about 0.5 and 2.0. The applied voltage is from 2.0 v/cell to 5.0 v/cell for dissolving the nickel and contaminants while cathodically producing hydrogen gas. Technetium (+4) species in the acid solution is oxidized to the technetium (+7) species. The pH of the technetium-containing acid solution is adjusted to between 2.5 to 4.5. Particulates in the acid solution are filtered from the solution for reducing the gross beta activity of the acid solution to less than about 50 Bq/gm. Radioactive ions (including technetium complexes) are sorbed in an anionic exchanger and a cationic exchanger for reducing the gross beta activity of the acid solution to less than about 20 Bq/gm. After verifying the gross beta activity of the acid solution, the acid solution is either recycled or charged to a electrowinning step. Acid solution having an activity of more than about 20 Bq/gm is recycled to upstream of the anion exchanger and the cationic exchanger. Acid solution having a gross beta activity of less than about 20 Bq/gm is charged to the electrowinning step. Nickel is plated at a voltage of about 2 v/cell to about 6 v/cell while oxygen gas is anodically generated. The pH of barren metal acid solution from the electrowinning step is reduced to less than about 2 and the barren metal acid solution is recycled for dissolving additional contaminated nickel.

Decontamination of radioactive metals

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Kingston, TN, United States of America

Dwight F Goad