This database provides all the measurements of dissolved radioactivity in seawater performed by IRSN in north-western European seas. It concerns Sb125, Ru106, Co60, Cs137, Cs134 and tritium (H3). Measurements concern 80 oceanographic campaigns performed between 1982 and 2016 (39642 stations). The areas sampled are mainly the English Channel, North Sea, Biscay Bay, Celtic Sea, Irish Sea and the northern Atlantic. This database comes together with the liquid releases database issued from English and French nuclear plants. It allows qualitative and quantitative comparison between quantities released and measured and validation of hydrodynamic models at all scales.