Projects: T2GGM – A Coupled Gas Generation Model for Deep Geologic Disposal of Radioactive Waste

Client: Nuclear Waste Management Organization

T2GGM consists of a gas generation model (GGM), which calculates rates of gas generation and water consumption within a deep geologic repository (DGR) due to corrosion and microbial degradation of the waste packages, integrated with the widely used two-phase flow code TOUGH2, which models the subsequent two-phase transport of the gas through the repository and into the DGR shafts and geosphere.

Many new features have also been added to T2GGM by Geofirma, including but not limited to: time-variable boundary conditions; time-variable permeability; a 1D hydromechanical model to simulate glaciation events; consideration of super-critical gas properties; FLAC integration; saturation-dependent permeability for bentonite materials; various features to improve model stability and convergence; and binary formatted output files for improved post-processing. All software development has been performed under control of an ISO 9001:2008 certified QMS and are verified and documented to meet nuclear grade software QA requirements.

T2GGM has been applied to the assessment of gas transport from a proposed low- and intermediate-level radioactive waste DGR (Postclosure Safety Assessment Modelling) and to study the impact of container corrosion in a hypothetical used fuel DGR. T2GGM without the gas generation component has been applied to several projects including FORGE benchmark modelling. The T2GGM model is described in this short paper.

For additional information, please contact John Avis, P.Eng., Head of Modelling.