Electrochemical Processing of Al clad Targets for Selective Extraction

MARK-18A target assemblies were irradiated 44 years ago in a reactor at the Savannah River Site operating in a high-flux mode to produce heavy isotopes for defense purposes, Department of Energy programs, research, and industrial and medical applications. About a quarter of these target assemblies were processed at the time, leaving 65 unprocessed targets to await disposition in a storage pool at the Savannah River Site. For all practical purposes, these unprocessed targets are the only future source of 244Pu, and also contain significant quantities of heavy Cm and Am. The MARK-18A Target Material Recovery Program was established to preserve the unique materials in the remaining targets. As part of that program, it was envisioned that the targets would likely be processed with aqueous methods at the Savannah River Site, prior to select actinides being sent to Oak Ridge National Laboratory for storage and further isotope enrichment and separations. There are several aqueous based options to disposition these materials that are considered viable. However, an alternative approach may be needed to disposition the target assemblies should the planned reprocessing facility reach end of life sooner than anticipated, or complications be encountered in performing the work in other optional facilities. In this paper we investigate the viability of using electrochemical processing to disposition the targets and extract the desired isotopes, as an alternative to the aqueous options. Electrochemical processing can extract the same elements of interest as the aqueous methods, with a small footprint, minimal waste, without H2 gas generation, and may be ideally suited for small batch operations on uncommon fuels or fuel forms. The Mark-18A target assemblies were fabricated from Al and Pu. The target material is highly dispersed in an aluminum matrix potentially making electrorefining more difficult unless the electrorefiner is engineered for this. This study may also be applicable for many types of aluminum based fuels in storage at the Savannah River Site. To investigate the possibility to electrochemically separate Pu and Am from the Al in which it was dispersed, electrochemical separations were investigated with an anodic dissolution basket containing lanthanides as surrogates and Al-1100.