Electrodeposition of Uranium and Transuranic Elements onto Solid Cathode in LiCl-KCl/Cd System for Pyrometallurgical Partitioning

Abstract

A pyrometallurgical partitioning process is being developed for recovering transuranic elements (TRUs) from high-level liquid waste. In the process, actinides are separated from fission product, especially rare earth elements (REs), by means of an electrorefining technique or a reductive-extraction technique. In this study, electrorefining experiments were carried out in LiClKCl/Cd system to recover actinides from salt bath containing actinides and REs. Uranium and neptunium could be depleted from the salt bath and recovered onto a solid cathode with high collection efficiency and high selectivity. Plutonium and americium, however, were difficult to be recovered at high current efficiency because reduction of Nd³⁺ to Nd²⁺ at about—1.7V consumed cathodic current prior to the deposition of Pu or Am. The rotation of the cathode had rather negative effect against deposition of Am and Pu in case of coexistence of much amount of Nd because Nd²⁺ was removed from the cathode surface quickly and the reaction of Nd³⁺ to Nd²⁺ was promoted. At higher current density, Pu and Am could be recovered onto solid cathode but current efficiency became too low. The result indicated that electrorefining technique in the pyro-partitioning was effective for U and Np but not for Pu and Am.

KEYWORDS:

• pyrometallurgical partitioning
• pyro-process
• uranium
• transuranic elements
• rare earth elements
• solid cathode
• deposition
• separation
• molten salt
• liquid cadmium
• high-level liquid waste