[en] An irregular concentration/depth profile of uranium in deep-sea turbidities, previously elucidated, has been exploited to obtain in-situ effective diffusion coefficients for the long-lived members of the ²³⁸U natural series. The findings are relevant to the assessment of deep-sea sediments as potential repositories for high-level radioactive waste, because waste actinides decay through the same chains of daughter radionuclides as natural actinides. This work was part of the CEC Mirage project-Second phase, Natural analogues research area