This dataset comprises gamma spectrometric measurements of radioisotopes in samples from polymetallic nodules, which were collected in the framework of the European collaborative JPI Oceans MiningImpact project onboard R/V SONNE cruise SO239 in 2015. Samples were taken from different parts of the nodules (topside surface (s), bottom surface (b), interior (i)). The gamma radiation was measured in a Canberra well-type HPGe detector. Emission lines at 46 keV (Pb-210), 63 keV (U-234 via Th-234), 67 keV (Th-230), 186 keV (Ra-226 in absence of U-235 interference), 295 keV (Ra-226 via Rn-222) and 402 keV (Pa-231 via Rn-219 with some uncertainty on the intermediate Pa-231/Ac-227 equilibrium) were evaluated. The diluted uranium ore standard RGU-1 and the uranium ore standard UREM-11 served as calibration and reference, respectively.

RGU-1 (400 ppm U) was used for calibration. Except for U (186 keV!), activities are very similar to nodules.