Development of pyro-metallurgical process for end crops of magnox spent fuel

At the Tokai-1 magnox nuclear power station, end fittings are cropped from irradiated magnox fuel elements. These end crops stored in alkaline water for several years prior to planned grating in cement within drums for further storage and eventual disposal. This study proposes a new pyro-metallurgical process to reduce the waste volume of transuranium elements (TRUs) of magnox end crops. The process combines melt separation and electrorefining in molten salts. The feasibility of the new pyro-metallurgical process has been confirmed experimentally. This paper outlines the study of the separation mechanism of magnox alloy from uranium by electrorefining in molten salts. The decontamination factor (DF) of magnox alloy from uranium in electrorefining in molten salts was estimated to be more than 10⁴. The electrochemical behaviors of U and Mg in KCl-LiCl eutectic salt were analyzed using cyclic voltammetry. The redox potential difference between U and Mg was about 250 mV, which is much larger than the 80 mV value that was estimated from thermodynamic data for standard states. U was separated from Mg and selectively deposited on the solid cathode in molten salts. (author)