For the first time in nearly three decades, American scientists have produced a plutonium-238 sample, with a research team at the Department of Energy’s Oak Ridge National Laboratory in Tennessee announcing the feat in a statement released on Tuesday.
Plutonium-238 is a radioactive isotope that produces heat as it decays, and the new sample is in the same oxide power form used to manufacture heat sources for power systems, including those used in spacecraft instruments, they explained. It is the first sample of the substance produced in the US since the late 1980s, when production at a South Carolina plant was halted.
Officials at the laboratory will now analyze the sample to ensure its plutonium-238 content and its chemical purity. Once that is finished, they will ensure that the production process is at peak efficiency and make any necessary adjustments, and then the isotope will be produced en masse.
“Once we automate and scale up the process, the nation will have a long-range capability to produce radioisotope power systems such as those used by NASA for deep space exploration,” said Bob Wham of the ORNL’s Nuclear Security and Isotope Technology Division.
Process could ultimately produce up to 1.5 kg of plutonium
The plutonium-238 production process, which has been underway for two years and is funded in part by NASA, could allow ORNL and colleagues at Idaho National Laboratory to provide up to 300 to 400 grams of the material per year for NASA to use as a power source.
The production process begins in Idaho, where neptunium-237 feedstock is housed and shipped to the Tennessee facility as needed. Engineers mix neptunium oxide with aluminum, the research team explained, then press it into high-density pellets that are irradiated. This process turns them into neptunium-238, which rapidly decays into plutonium-238.
The pellets are dissolved, and ORNL staff separate the plutonium from leftover neptunium using a special chemical process. Plutonium is then converted into an oxide and shipped to Los Alamos National Laboratory for storage, while the remaining neptunium is recycled and used to produce more plutonium-238. Currently, about 35 kg worth are available for NASA missions.
“With this initial production of plutonium-238 oxide, we have demonstrated that our process works and we are ready to move on to the next phase of the mission,” said Wham. Once they are able to scale-up and automate the process, he and his colleagues believe that they will be able to produce an average of1.5 kg of the substance per year.
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Feature Image: Oak Ridge National Laboratory
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