An unknown source of reactor radionuclides in the Baltic Sea revealed by multi-isotope fingerprints
Jixin Qiao, Haitao Zhang, Peter Steier, Karin Hain, Xiaolin Hou, Vesa-Pekka Vartti, Gideon M. Henderson, Mats Eriksson, Ala Aldahan, Göran Possnert, Robin Golser
Abstract
Abstract We present an application of multi-isotopic fingerprints (i.e., 236 U/ 238 U, 233 U/ 236 U, 236 U/ 129 I and 129 I/ 127 I) for the discovery of previously unrecognized sources of anthropogenic radioactivity. Our data indicate a source of reactor 236 U in the Baltic Sea in addition to inputs from the two European reprocessing plants and global fallout. This additional reactor 236 U may come from unreported discharges from Swedish nuclear research facilities as supported by high 236 U levels in sediment nearby Studsvik, or from accidental leakages of spent nuclear fuel disposed on the Baltic seafloor, either reported or unreported. Such leakages would indicate problems with the radiological safety of seafloor disposal, and may be accompanied by releases of other radionuclides. The results demonstrate the high sensitivity of multi-isotopic tracer systems, especially the 233 U/ 236 U signature, to distinguish environmental emissions of unrevealed radioactive releases for nuclear safeguards, emergency preparedness and environmental tracer studies.