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The Department of Energy (DOE), in collaboration with the National Aeronautics and Space Administration (NASA), has reached an important milestone towards reestablishing the ability to fuel future space exploration missions. Now, a small quantity of newly produced heat source plutonium oxide is destined for use on the Mars 2020 rover.
Like the Curiosity rover that has been exploring Mars since August 2012, the Mars 2020 mission will obtain its electrical power from a radioisotope power system called a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG). A MMRTG converts the heat created by naturally decaying plutonium-238 into electricity that can be used to run a spacecraft and its science instruments. Radioisotope power systems enable or enhance missions where sunlight is infrequent, obscured by dust, or dimmed by distance, making other sources of power impractical or insufficient.
DOE made plutonium-238 at its Savannah River Site from the 1960’s until the 1980’s but that capability was terminated as the site’s reactor operations ended. Since then, the Department and NASA have utilized existing inventories of plutonium-238 and supplemental purchases from Russia to support NASA exploration missions through the mid-2020s.
In 2012, DOE and NASA initiated efforts to reestablish the capability to produce plutonium-238 utilizing existing DOE research reactors at Oak Ridge National Laboratory and Idaho National Laboratory. Late in 2015, DOE produced the first new plutonium-238 in the country in nearly 30 years at Oak Ridge National Laboratory. The plutonium was converted into heat source plutonium oxide this past fall and a portion was shipped to Los Alamos National Laboratory for analysis to verify its acceptance for use in space missions. The plutonium oxide was judged to be acceptable, and the agencies have agreed to a pilot demonstration that will include use of a small portion of the new heat-source plutonium oxide in the MMRTG under construction for Mars 2020 mission. Los Alamos National Laboratory will blend the new heat source material with its existing inventory to make the fueled clads for the radioisotope power system.
Although the new heat source material will have nominal impact on the performance or power of the MMRTG for the Mars 2020 mission, the demonstration of plutonium-238 production through the use of this material is an important strategic step in reestablishing this unique capability. This will exhibit the complete supply chain from isotope production, through use in producing a heat source, to the final fueling of a radioisotope power system. The information gained from this pilot demonstration will be used to ensure that the Department of Energy will continue to meet NASA’s mission needs for exploring space.