Identification of a chemical fingerprint linking the undeclared 2017 release of Ru to advanced nuclear fuel reprocessing.

The undeclared release and subsequent detection of ruthenium-106 (Ru) across Europe from late September to early October of 2017 prompted an international effort to ascertain the circumstances of the event. While dispersion modeling, corroborated by ground deposition measurements, has narrowed possible locations of origin, there has been a lack of direct empirical evidence to address the nature of the release. This is due to the absence of radiological and chemical signatures in the sample matrices, considering that such signatures encode the history and circumstances of the radioactive contaminant.