For the first time in nearly 30 years, the U.S. Department of Energy has produced a sample of plutonium-238, the radioactive isotope used to power deep space missions, good news for future NASA space probes heading to destinations starved of sunlight. The 50-gram (0.1-pound) sample is a fraction of the plutonium needed to fuel one spacecraft power generator, but the Energy Department said the material represents the first end-to-end demonstration of plutonium-238 production in the United States since 1988. The DOE made the new batch of plutonium-238 at Oak Ridge National Laboratory in Tennessee. Nuclear-powered spacecraft transfer heat generated by the radioactive decay of plutonium-238 pellets into electricity. Plutonium power systems fly aboard NASA’s Curiosity Mars rover, the Cassini orbiter at Saturn and the New Horizons probe that encountered Pluto last year. Nuclear scientists must artificially create plutonium-238 in a reactor because the isotope is not found in nature. Technicians take neptunium-237, an isotope with the same number of neutrons and one fewer proton, mix it with aluminum and crush it into tightly-packed pellets. A reactor at Oak Ridge fires neutrons at the pellets, irradiating the neptunium to generate plutonium-238.
Space Flight Now 7th Jan 2016 read more »