Expected effects of seawater-induced salinity increase on migration of Radionuclides in Boom Clay

Compared to present-day geochemical conditions in the Mol area, the Boom Clay is subjected also to higher ionic strength pore water, both nowadays in locations more to the west of the Mol site, and in the future as a result of seawater intrusion. This report describes the expected impacts an increased ionic strength/salinity can have on the migration of radionuclides in the Boom Clay. An increased ionic strength may influence the speciation and solubility of radionuclides, the sorption of radionuclides on the Boom Clay surfaces, the diffusion of radionuclides in Boom Clay matrix. Moreover, the behaviour of natural organic matter is expected to vary to large extent when the ionic strength of the pore water increases. These processes are discussed based on existing experimental data, scoping calculations, and literature studies. Future works to tackle the influence of increased salinity on migration of radionuclides in Boom Clay are anticipated.