A consistent phenomenological model for natural organic matter linked migration of Tc(IV), Cm(III), Np(IV), Pu(III/IV) and Pa(V) in Boom Clay

Long-term sequential migration experiments with Tc, Cm, Np, Pu and Pa through Boom Clay cores were used to interpret organic matter (OM) linked radionuclide (RN) transport. Interaction of these elements with mobile OM results in an enhanced transport, as stabilised RN-OM species. However, this interaction is known to be governed by association/dissociation kinetics. The stability of these complexes are therefore a key factor for describing the mobility of these RN-OM species. To describe the RN-OM linked transport for Safety/Performance Assessment evaluations, a consistent phenomenological model is proposed that accounts for the RN-OM transport undergoing slow dissociation and sorption of both RN-OM and RN to the solid phase.