Twelve years after the nuclear accident that occurred in Fukushima in March 2011, radioactive contamination remains a major concern in north-eastern Japan. The Japanese authorities completed an unprecedented decontamination programme. The central objective was to not expose local inhabitants to excessive radioactive doses. At the onset of the full reopening of the Difficult-to-Return Zone in 2023, the current review provides an update of a previous synthesis published in 2019.

This dataset provides an original compilation of radioactive dose rates and artificial radionuclide activities in sediment deposited after floods in the rivers draining the main radioactive pollution plume in Fukushuma, Japan, between November 2011 and November 2020. In total, 782 sediment samples collected from 27 to 71 locations during 16 fieldwork campaigns were analysed. This provides a unique post-accidental dataset to better understand the environmental fate of radionuclides.

A number of sites in the Fukushima contaminated area were surveyed for long-term changes in dose equivalent rate above the soil surface during 2015–2017 using D-shuttle dosimeters. D-shuttle readings in most cases decreased faster than if due to radioactive decay only. More rapid decrease can be explained by natural attenuation processes, such as erosion of the topsoil, the vertical migration of radionuclides in the soil and the deposition of cleaner sediments transported by surface runoff.