Analysis of Uranium Metal Samples from Germany's World War II Nuclear Program - A Case between Science History and Nuclear Forensics –

In 1998, during clean-up operations in a cellar in the Bavarian town of Garmisch- Partenkirchen, a black cube of 5 cm side length and 2.4 kg in mass was found. It turned out to consist of metallic uranium of natural isotopic composition. The cube had initially been discovered in the 1960's by some boys, playing on a riverbank in Bavaria. In its appearance, the cube is similar to the material used by Werner Heisenberg in his attempts for building a nuclear reactor. A sample of the cube was made available to the Institute for Transuranium Elements (ITU) in order to establish the authenticity of the material. Furthermore, a uranium metal plate was investigated, which is also supposed to date back to the German nuclear program of the early 1940's. Nuclear forensic investigations were carried out in order to prove the authenticity of the uranium metal cube and the plate and to provide further information on the history of the two materials. These investigations included isotope ratio measurements of uranium and strontium, impurity measurements and determination of the last chemical separation of the uranium. Wherever possible, comparison samples were analysed in order to help data interpretation. These investigations illustrate the process of nuclear forensic analysis and attribution. At the same time, they provide insight in a highly interesting episode of science history.