Radioactivity in Manganese Nodules

The dataset contains specific activities of naturally occurring radionuclides in bulk and surface samples of deep-sea manganese nodules, and activity ratios of of selected nuclides. Polymetallic Nodules from the deep sea are currently being targeted for mineral exploration as they are a significant resource for various critical metals. In addition to accumulating such metals, nodules are also known to adsorb naturally occurring radioactive nuclides. With the possibility of exploitation of nodules becoming more likely within the next years, it is important to assess the potential radiation exposures resulting from the handling of polymetallic nodules. In this study we present, for the first time, specific activities of all dose-relevant alpha and gamma emitters from the natural decay chains of Uranium-238, Uranium-235 and Thorium-232, as well as the radon exhalation rate. The results show elevated specific activities for the nuclides Th-230, Ra 226, Pb-210 and Po-210 in accordance with prior reported activities. However, in contrast to assumptions made in previous studies, our analyses show that Pa-231 is not in equilibrium with its daughter nuclide Ac-227. The results presented here are a key ingredient to assess radiation exposure of humans from mining and processing polymetallic nodules.