Abstract: 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.

Abstract: 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.