Environmental levels of radiocarbon in lund, sweden, prior to the start of the european spallation source

ABSTRACT The European Spallation Source (ESS) is a neutron-based research facility under construction in Lund in southern Sweden. The spallation reactions will generate not only the desired neutrons, but also many radioactive by-products, including 14 C. As part of the licensing process, and as recommended by the IAEA, various preoperational studies are being carried out, including mapping the “zero-point” radiation environment around the site. As the city of Lund hosts several facilities using 14 C-labeled substances, and since temporary and local 14 C contamination have been observed in the past, 14 C mapping is an important part of these baseline assessments. We here present a summary of 14 C levels in various terrestrial environmental samples in Lund and in southern Sweden during the years 2012 to 2020. These environmental F 14 C do not display significantly elevated levels compared to sites located remote from Lund. We also describe a local 14 C contamination event that was detected at the Lund Radiocarbon Dating Laboratory in 2009. Horse-chestnut leaves collected close to the laboratory exhibited F 14 C values of up to ∼25% above the clean air background. Elevated values of F 14 C were also found in a short tree-ring series, especially in 2007. The source of this contamination was identified and successfully removed.