SRNL Recovery of Plutonium-244 and Heavy Actinides from Mark-18A Targets

In the 1960s and 1970s, the Savannah River Site (SRS) K Reactor performed high-neutron-flux irradiations to produce unusual and heavy isotopes, including the first significant quantities of californium-252. The 86 Mark-18A target assemblies also produced, as byproducts, most of the world’s supply of plutonium-244 and “heavy” curium. These isotopes are of significant interest for precision analyses, targets for new heavy isotope production, and nonproliferation studies, but the supply from 21 assemblies processed in the 1970s is nearly exhausted and is irreplaceable in existing facilities. In 2015, the Office of Nuclear Materials Integration, of the Department of Energy National Nuclear Security Administration, initiated funding for a program to remove the 65 remaining targets from the SRS L Basin, recover the plutonium-244 and transplutonium ele- ments in the Savannah River National Laboratory (SRNL) Shielded Cells Facility, and transfer the product material as oxide to the Oak Ridge National Laboratory. SRNL is performing key modifications to the cells, developing an optimum onsite shipping cask, and modeling the targets to validate actinide contents and identify other isotopes that may be of interest to the scientific and industrial community.