A method to prove the origin of uranium cubes believed to have been salvaged from the Nazi atomic bomb programme could help law enforcement investigate illegal trafficking of nuclear material.
The Nazis had two nuclear weapons programmes during the second world war. Some 1200 cubes of uranium were created, and approximately 600 made their way to the US in the closing stages of the war, according to Jon Schwantes at the Pacific Northwest National Laboratory in Washington state.
He estimates that the location of only a dozen of all the cubes is known today, and that the vast majority of those brought to the US were folded into its own nuclear programme.聽One of the cubes now belongs to his lab, but nobody knows how it came to be there. His team is working on techniques to prove its provenance.
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Radio chronometry is often used to date ancient samples of naturally occurring radioactive material in rocks and minerals, but methods that are accurate enough to date rocks billions of years old may not be sufficient to distinguish between a metal processed in 1939 or 1940, for example.
Instead of measuring the amount of a single radioactive element that has decayed into another to date a sample, the researchers analysed pairs of 鈥減arent鈥� and 鈥渄aughter鈥� radioisotopes. For instance, they can measure the amount of thorium-230 produced from the decay of uranium-234, as well as the protactinium-231 produced from the decay of uranium-235.
They are also developing new techniques to speed up and simplify the process of preparing samples for such analysis. This process isolates rare earth elements that can then be used to shed light on the location the ore was mined.
The team hopes to show that the cube is a genuine artefact from the Nazi nuclear programme. They presented their findings at a meeting of the American Chemical Society on 24 August.
