Confinement and migration of radionuclides in a nuclear waste deep repository

The safety of the geological disposal of nuclear waste is evaluated, among other factors, through the ability of radionuclides to be confined, first by waste packages then by engineered barriers and host rocks. Deep underground conditions favour the immobilisation of most radionuclides by sorption or precipitation, which means that mobile radionuclides, such as I-129 or Cl-36, may contribute to most of the ultimate dose release during up to a million years. However, degraded evolution scenarios must be taken into account (oxygen intrusion, faults,...) to assess earlier dose releases. (C) 2002 Academie des sciences/Editions scientifiques et medicales Elsevier SAS