Nuclear Forensic Science has recently emerged as a new multi-disciplinary research area. It comprises a variety of chemistry and physics methods to identify recovered nuclear material of unknown origin and to determine the source of this material. Illicit trafficking of nuclear material and other radioactive sources is a phenomenon which has emerged in the early 1990s, facilitated by the collapse of the Soviet Union with its large inventory of such material and its underdeveloped control and security infrastructure. Hundreds of illicit traficking incidents have been reported and are listed in the IAEA database. They include both nuclear material and radioactive sources used in medicine and research. Of the former, mostly depleted, natural or low enriched uranium appears on the black market. There have also been a number of cases involving weapon-utilisable highly enriched uranium and plutonium, however, in quantities to small to make a nuclear weapon. Of the latter, mostly Cs-137 and Co-60 sources were recovered. This material could be used to build radiological weapons, so-called dirty bombs.

The talk will provide an introduction into some of the established as well as recently developed methods used in the context of nuclear forensics. Experimental techniques such as gamma-, alpha-, and mass-spectrometry are used for the identification of the recovered material and the determination of its isotopic composition. Other analytical tools reveal chemical and morphological characteristics which can be compared to reference material databanks. All this information taken together helps determining the age of the material and the manufacturing or reprocessing plant out of which it originated. In Bremen, we are currently advancing a supplementary method, based on a systematic survey of the burnup characteristics of different nuclear reactors. This method may help in the future to determine with more confidence the type of the reactor from which the recovered nuclear material was taken. The methods presented here are also of high significance for arms control verification purposes and in view of a possible fissile material cut-off treaty.