Nuclear Materials Recovery Based on Oxide Reduction by Electrochemical Amalgamation and Thermal Extraction (OREATE)

Developing a process that can consistently convert actinide and rare earth metal oxides to chemically pure metals in near quantitative yield will have significant impact on many levels, from fundamental science to national security-related applications. In recent years, our team at LANL has been working on the development of OREATE (Oxide Reduction by Electrochemical Amalgamation and Thermal Extraction), a project funded by NA-ESH-12 (DOE). This project was initiated for the recovery of plutonium 244 (Pu-244) from the Mark-18 targets stored at Savanna River National Laboratory (SRNL). Because of the small quantities of Pu-244 available in the world, Pu-244 stored at SRNL was identified as extremely important resources for national security. Therefore, it was decided that recovering Pu-244 required a high yield and metal purity process like OREATE. The design of OREATE includes three basic steps that are integrated in a line of interconnected inert gloveboxes: (i) oxide reduction, to dissolve PuO2 into an acidic media where it is chemically reduced to PuCl3; (ii) electrochemical amalgamation, to reduce PuCl3 into a mercury pool to form PuHgx amalgam; (iii) thermal extraction, to distill and recycle the mercury in a furnace, decompose the amalgam, and obtain pure Pu metal. Thus far, the results obtained using Cerium (Ce) as chemical model demonstrated near quantitative yield of the electrochemical amalgamation (yield > 99%), almost complete mercury recovery during the thermal extraction (Hg recovery > 99.5%), and high purity of the Ce metal product (purity > 99%). Moreover, a variety of system parameters such as metal concentration, reduction potential, temperature, as well as concentration and pH of the buffered solution were explored using silver-based mercury film electrodes (SBMFE) to provide insight into how those variables may affect the electrochemical amalgamation reaction.