oa Simulation of Gas Migration in a Waste Disposal in Deep Clay Formation – What Pathways? What Time and Space Scales?

A radioactive waste disposal in a deep clay formation is mainly based on the low, water and gas, permeability of the host rock. This property returns to a low capacity of gases evacuation and hydrogen produced by anoxic corrosion and radiolysis of organic waste, will affect the repository on time. At first raises the phenomenological question at the different space scales: what processes? , what pathways? , what gas pressure? , what couplings? Secondly raises the question of the safety functions: opening of preferential pathways due to gas fracturation?, transfer induced by water displacement due to gas or transfer in gas form? A first answer was brought by Andra in the Dossier 2005-Argile which concluded on the feasibility of the disposal. Since then, Andra has continued (i) researches on characterization of gas migration processes, and (ii) numerical simulation of the production and the migration of gas. The numerical work is covering scales from the disposal cell up to the whole disposal and from operating period to long term post closure. These new results will in term contribute to update a pluriannual program of data acquisitions on fundamental mechanisms of gas production and migration.