Abandoned weapons-grade plutonium traced back to second world war
A jug found in a battered safe at a disused waste burial ground in the US held the world's oldest sample of weapons-grade plutonium, produced during the Manhattan Project.
The safe containing the one-gallon vessel was unearthed in 2004 during a clean-up operation of a waste trench at the Hanford nuclear site in Washington state. The clean-up team noticed the jug was partially filled with a mysterious white slurry and sent it for testing.
Scientists at Pacific Northwest National Laboratory in Richland have now revealed that the jug contained several hundred milligrams of bomb-grade plutonium, which they have dated to 1944 when the US nuclear programme was still in its infancy.
Analysis of the jug's contents shows that the material did not originate at Hanford but can be traced back to the world's first industrial-scale nuclear reprocessing site in Oak Ridge, Tennessee.
Jon Schwantes, who led the team of investigators, describes their work as "nuclear archaeology" in the latest issue of the journal Analytical Chemistry.
The US nuclear bomb programme was set up in 1939 in response to fears that Nazi Germany was developing a similar weapon. Research and production for the project was based at three sites–Hanford, Oak Ridge and Los Alamos in New Mexico–under the watchful eye of Robert Oppenheimer.
During the Second World War, the Hanford facility produced bomb-grade plutonium for Trinity, the first nuclear weapon to be tested, and later for the atomic bomb dropped on Nagasaki in Japan.
Schwantes said the forensic techniques used to identify the nuclear relic will come in useful for tracing material confiscated from smugglers caught with black market nuclear materials.
"It is likely that with the current nuclear renaissance and greater access to these materials by the public, smuggling events involving fissionable materials may rise in the near future," Schwantes said.