Modelling tritium transport, matrix diffusion and multiphase flow in a concrete cell used for storing radioactive waste at El Cabril (Spain)

Abstract

‘El Cabril’ is the low and intermediate level radioactive waste disposal facility of Spain. Water with high concentration of tritium is collected from a drain, which is situated at the centre of a concrete cell that stores radioactive waste, indicating flow of water within the cell. 2D numerical models have been made in order to develop a qualitative and partial quantitative understanding of the processes that causes this phenomenon. The conceptual model considers evaporation and condensation processes due to temperature gradients, matrix diffusion between a mobile zone (with advection, dispersion and diffusion) and an immobile zone (with only diffusion). Model results suggest that only the tritiated water used to prepare the mortar to refill the containers, which can be in liquid and gas phases, could leave the cell being collected in the drain.