The United States Department of Energy's Savannah River Site (SRS), near Aiken, South Carolina, USA, stores transuranic waste contaminated with Pu-238 oxide particles. Portions of this waste cannot be shipped to the Waste Isolation Pilot Plant (WIPP) in TRUPACT-II containers due to excessive generation of hydrogen gas as a result of radiolysis of organic constituents in the waste matrix. Decontaminating the organic matrix sufficiently to meet the hydrogen gas concentration limits has the potential of being a simple, safe and effective method of eliminating the need for continued storage at SRS. A glovebox-sized decontamination system was designed, fabricated and tested with non-radioactive simulants to demonstrate the capability of the Sonatol (TM) process as a means of treating legacy Pu-238 waste. In this process, solid test pieces contaminated with a Pu-238 oxide simulant were subjected to liquid shear in a 1% solution of a highly fluorinated surfactant in perfluoroheptane and then rinsed with perfluoroheptane. The used process liquid was filtered through metallic and ceramic filters to remove suspended particles and recycled. The rinse liquid was generated by passing some of the recovered surfactant solution through a bed of activated carbon. Three different combinations of surrogate waste materials, with an organic content that ranged from 17 to 45% were developed to represent divergent Pu-238 waste streams. The surrogates were contaminated with a plutonium oxide simulant that was a mixture of a fluorescent tracer (Osram Sylvania Phosphor 2284C particles), and of a sub-micrometer sized chemical analog of plutonium oxide (cerium oxide). The waste surrogates were contaminated by spraying with dilute (approx. 1000 ppm) suspensions of simulant powders in a volatile, low surface tension liquid (HFE-71-IPA, 3M). After carrying out some optimization tests, decontamination protocols were developed that resulted in > 99% removal of simulated contaminant from a wide range of organic and inorganic test pieces, and > 99.9% capture of the simulant on a ceramic filter.
