[LINK] "Manhattan Project Plutonium, Lost to Obscurity, Recovered by Scientists"

[rfmcdonald]

Scientific American's Andy Extance reports on the recovery of a remarkable historical artifact.

“Fat Man,” the atomic bomb dropped by the U.S. on Nagasaki, Japan, in 1945, carried about 6.2 kilograms of enriched plutonium, roughly the size of a softball. The origin of that deadly hunk of metal can be traced back via a tiny sliver weighing less than three millionths of a gram, created in the labs of Manhattan Project researchers. It is a historic fragment, embodying both stunning scientific achievement and deep tragedy—that one bomb killed and wounded at least 64,000 people (estimates vary) as well as hastened Japan’s surrender. And in 2007 this historic sample, the first plutonium ever seen by researchers, vanished from the public eye.

Now it has resurfaced in a plastic box in a windowless, secure six-foot by six-foot room in the University of California, Berkeley’s Hazardous Material Facility. The tiny lump, derived from Nobel Prize–winning chemist Glenn Seaborg’s original discovery of the element, was accompanied by only limited documentation about its origins. But a Berkeley team has found radioactive fingerprints indicating the sliver indeed comes from the Manhattan Project. They published their findings on the arXiv physics preprint server on December 24, and are now pushing to return this bit of history to public display.

The sliver’s story starts in 1941, when the world’s warring powers were racing to develop an atomic bomb, focusing largely on nuclear fission of uranium. At Berkeley that year, Seaborg, along with Arthur Wahl and Joseph Kennedy, synthesized an entirely new element: plutonium. Although they only produced vanishingly small traces of it by bombarding uranium 238 with deuterons—particles made of one proton and one neutron—they quickly determined it had explosive potential as nuclear bomb material.

By the start of 1942, scientists studying the nuclear chain reaction, such as physicist Enrico Fermi, and plutonium chemistry, such as Seaborg, were ordered to the University of Chicago to begin the work of the A-bomb–developing Manhattan Project. (Seaborg wrote about synthesizing plutonium, and several other elements, for Scientific American in an April 1950 article that includes a grainy photograph of one sample made in Chicago.