Plutonium-238 has proved to be an awesomely effective fuel for dozens of NASA missions to the depths of space, such as the Curiosity Mars rover, Cassini, and the Voyager spacecraft twins who are currently cruising through interstellar space.
However, this radioactive isotope has always proved to be a pain to produce – until now. On behalf of the US Department of Energy, scientists at Oak Ridge National Laboratory (ORNL) have found a way to automate the production of neptunium oxide-aluminum pellets. The high-density pellets can then be simply (relatively speaking) irradiated and chemically processed into plutonium-238, meaning production of this invaluable isotope is easier than ever.
“The automation replaces a function our team did by hand and is expected to increase the output of pressed pellets from 80 to 275 per week,” Bob Wham of ORNL said in a statement.
Plutonium-238 is a particular isotope of plutonium that’s capable of steadily pumping out heat due to its natural radioactive decay, yet it remains relatively stable, safe, and emits relatively low levels of beta and gamma radiation. It also has a half-life of 87.7 years, allowing it to produce the same amount of energy for decades. For example, Voyager 1 and Voyager 2 were launched way back in 1977, but their scientific instruments are still powered up and will work for another couple of years thanks to their onboard stores of plutonium-238.
You won’t find plutonium-238 in atomic bombs or nuclear power plants. Although, this isotype used to be created as a by-product of weapons-grade plutonium, plutonium-239.
A few decades ago, towards the close of the Cold War, the world’s stockpiles of plutonium-238 were running low. The US has restarted production of the isotope in recent years, however, it's some margin off NASA’s targets. ORNL has previously stated that NASA only had about 35 kilograms (77 pounds) of plutonium-238 left, just enough for two or three more space exploration missions. It’s hoped that this solution could seriously help to ramp up production to meet NASA’s grand target before dwindling supplies reach crisis point.
“Automating part of the Pu-238 production process is helping push annual production from 50 grams to 400 grams, moving closer to NASA’s goal of 1.5 kilograms per year by 2025," said Wham.