Thermal Conductivity Studies on NpO2-Al Cermet Pellets

The ability to produce plutonium-238 here in the United States has become increasingly important as NASA’s supplies begin to dwindle. Pu-238 supplies heat and electrical power to machines sent on deep space missions, including the Cassini and Ulysses spacecraft. ORNL’s Pu-238 Technology Demonstration Project aims to showcase the lab’s ability to produce and consolidate Pu-238 at the High Flux Isotope Reactor (HFIR) and Radiochemical Engineering Development Center (REDC) through the irradiation of neptunium oxide – aluminum cermet pellets. Np-237 oxide and aluminum powders are mixed and pressed into target pellets, and the thermal conductivity of these pellets is a major factor in determining whether or not they can be irradiated for more than one HFIR cycle. Measuring the thermal properties of these pellets continues to be a difficult and inconsistent process. A ThermTest Transient Plane Source 2500S, basic calorimeter and longitudinal heat flow analysis system are being used to better understand the thermal properties of these pellets. Once established, these systems can be used to pursue scientific hypotheses that will help better understand the thermal properties of these cermet pellets.