This baseline dataset comprises downcore measurements of the activity of different radionuclides for sediment cores (GC, MUC, ROV-operated PUC) retrieved in the framework of the European collaborative JPI Oceans MiningImpact project onboard R/V SONNE cruise SO268 in 2019. The scientific work during cruise SO268 was part of the second phase of the MiningImpact project (Environmental impacts and risks of deep-sea mining) and is designed to assess the environmental impacts of deep-sea mining of polymetallic nodules in the Clarion-Clipperton Zone (CCZ) in the Pacific Ocean. After performing total acid digestions, the sediments were analyzed by isotope dilution using ICP-SF-MS (Element2, Thermo Scientific) for the determination of radionuclides at the Marine Geochemistry Lab, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven.