Articles | Volume 2
Conference Abstract
06 Sep 2023
Conference Abstract |  | 06 Sep 2023

Two-phase reactive transport modeling of heterogeneous gas production in a low- and intermediate-level waste repository

Falko Vehling and Haibing Shao

The widely proposed approach to dispose of low- and intermediate-level radioactive waste is to store it in a deep underground repository with multiple barriers. A typical gallery is filled with concrete containers accommodating cemented steel drums of waste. Inside a container, different gases may be produced by (bio)chemical reactions, which include pH-dependent anoxic corrosion of metals and the degradation of organic matter. Both reactions consume water and may lead to pressure buildup and transport of gas, both within and around the repository.

In order to investigate the controlling factors of this gas production process, a coupled reactive transport model of component-based two-phase flow in the OpenGeoSys framework is adopted here. The numerical study of Huang et al. (2021) has shown that a realistic internal structure of a waste package, including the heterogeneous distribution of materials with different chemical and hydrological properties, and the exchange of mass at the boundaries are key factors that determine the evolution of the waste package. Based on the study of Huang et al. (2021), the geometric configuration of the model has been further extended to reflect the various conditions of a multi-container disposal in a gallery. In a two-dimensional setup several model scenarios have been designed and simulated to study the change in gas production rate over time in relation to water availability in various geological and waste storage setups.

In this presentation, we show simulation results covering the geochemical evolution of a waste package over 500 years. It is found that the initial water content in the waste compartment only controls the gas production rate for the first 40 to 60 years. The early pressure buildup and gas release rates are largely controlled by several critical parameters, including the permeability of cement material and water availability at the boundary. The sensitivity of these parameters is currently being investigated in detail.

Financial support

This study is part of the work package ACED (Assessment of Chemical Evolution of ILW and HLW Disposal Cells) within the EURAD project. EURAD has received funding form the European Union's Horizon 2020 research and innovation program under grant no. 847593; (last access: 5 August 2023).


Huang, Y., Shao, H., Wieland, E., Kolditz, O., and Kosakowski, G.: Two-phase Transport in a Cemented Waste Package Considering Spatio-Temporal Evolution of Chemical Conditions, npj Mater. Degrad., 5, 4,, 2021. 

Short summary
In a geological waste repository, gas production is caused by water-consuming chemical reactions, the anoxic corrosion of metals or the degradation of organic waste. For safety assessment, it is required to consider the maximum pressure buildup and the induced transport of radionuclides. This 2D numerical study comprises a single container filled with 12 waste drums and aims to better understand the controlling parameter of the geochemical evolution and to improve full gallery simulations.