Сообщение от Sandy
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By automating the production of neptunium oxide-aluminum pellets, Oak Ridge National Laboratory scientists have eliminated a key bottleneck when producing plutonium-238 used by NASA to fuel deep space exploration. Pu-238 provides a constant heat source through radioactive decay, a process that has powered spacecraft such as Cassini and the Mars Rover. “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 ORNL’s Bob Wham. “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.” Once the pellets are pressed and enclosed in aluminum tubing, they are irradiated at ORNL’s High Flux Isotope Reactor and chemically processed into Pu-238 at the Radiochemical Engineering Development Center. In 2012, NASA reached an agreement with the Department of Energy to restart production of Pu-238, and ORNL was selected to lead the project.
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There is about 35 kilograms of plutonium-238 in current U.S. stockpiles available to NASA, said David Schurr, deputy director of the agency’s planetary science division, an amount that includes plutonium purchased from Russia. Of that amount, 17 kilograms is ready for use now, while the other 18 kilograms would need to be mixed with new plutonium in order to be viable for use in RTGs.
Only one NASA mission currently in development requires an RTG: the Mars 2020 rover, which will use an RTG similar to that powering the Curiosity rover. NASA is making available RTGs for the next New Frontiers medium-class planetary mission, which the agency plans to select by mid-2019 for launch in 2025.
Current supplies, plus new production, are enough for those missions and beyond, according to Schurr. “DOE will have sufficient material for fabrication of heat sources for expected planetary science missions through 2030,” he said. “In addition, NASA and DOE have begun exploring options to increase production rates, if needed, to support any increased future demand.”
GAO’s Oakley agreed, noting that limited supplies of plutonium-238 had been a limiting factor in past NASA decisions on what planetary science missions to pursue. “Right now, based on the development of new Pu-238, blended with the old, the needs are met in the near term,” she said. “If this new supply of Pu-238 isn’t established, and the goals aren’t met by DOE, then it could become a limiting factor again in the future.”
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