“…Indeed, Eu is considered to be a chemical homologue of certain trivalent actinides, such as Am or Cm, present in radioactive waste (Kautenburger and Beck, 2010). Europium retention values published in the literature are high and range from 5×10 4 to 10 5 L kg -1 for trace concentrations, thus reflecting a strong interaction with COx clay rock (ANDRA, 2005a;Descostes et al, 2017;Schott et al, 2012). Retention data obtained in the compact state are compared herein with data measured in the dispersed state and then discussed in light of both modeling results and a study of naturallyoccurring Eu in COx clay rock.…”