Tiny plutonium sample proven to come from Manhattan Project

Scientific American : In 2008 a 2.77-µg sample of plutonium was found encased in a plastic box in the Hazardous Material Facility at the University of California, Berkeley. It was accompanied by a placard describing its origins in the 1940s lab of Glenn Seaborg, one of the many scientists who had been tapped to develop a nuclear weapon for the Manhattan Project. To prove that the sample was authentic, researchers used a germanium ionization detector to search for the gamma and x rays that are emitted as plutonium decays. As further evidence, they failed to find any traces of americium, which indicates that the sample was probably plutonium-239, the particular isotope created by Seaborg. Plutonium-239 decays to uranium-238; plutonium-241, which was produced in later research, decays to americium. The unique sample may one day be put on display in the same Berkeley chemistry lab where Seaborg’s team did its historic work.