COMPOSITE WASTE FORM FOR IMMOBILIZATION OF RADIONUCLIDES FROM FUKUSHIMA DECOMMISSIONING BY POWDER METALLURGY HOT ISOSTATIC PRESSING

Abstract

The waste form development is a key issue for the decommissioning of the Fukushima Daiichi nuclear power plant. There are various radionuclides and wastes, some of which are troublesome nuclide in the waste management such as iodine-129 due to the extremely long-half life and mobility through the repository to biosphere. To immobilize the key nuclides, we propose the composite waste form that consists of primary wastes bearing objected radionuclides and a secondary metallic matrix which is the protection barrier for dissolution with high corrosion resistance. To demonstrate this concept, the representative composite waste form consists of silver iodide (AgI) and stainless steel was synthesized by powder metallurgy hot isostatic pressing (HIP). The powdery stainless steels were well sintered turning into the ingot matrix. No specific changes were observed for the AgI particles that they were individually dispersed and confined into the metal matrix. Based on the approved corrosion rate of stainless steel under an assumed repository condition, this composite waste form will immobilize the radionuclides for at least hundreds of thousands of years.