t3ggm: A coupled gas generation model for deep geologic disposal of radioactive waste

T3GGM consists of a gas generation model (GGM) integrated with the widely-used two-phase flow code TOUGH3. GGM calculates rates of gas generation and water consumption due to corrosion and microbial degradation of radioactive waste packages within a deep geological repository (DGR). TOUGH3 models the subsequent two-phase transport of gas through the repository and into the DGR shafts and geosphere.

Many features have been added to T3GGM by Geofirma, including but not limited to:
• Time-variable permeability,
• 1D Hydromechanical Model for simulation of glaciation events,
• Super-critical gas properties,
• Saturation-dependent permeability for bentonite materials,
• Features to improve model stability and convergence; and
• Linking models at different scales.

All software development has been performed under Geofirma’s ISO 9001 certified QMS and are verified and documented to meet nuclear grade software QA requirements.
T3GGM, and its predecessor T2GGM, has been applied to:
• Assessment of gas transport from a proposed low- and intermediate-level radioactive waste DGR (Postclosure Safety Assessment Modelling),
• Studying the impact of container corrosion in a hypothetical used fuel DGR,
• Studying the impact of gas generation on proposed high-level waste DGR, including glaciation impacts.
• FORGE benchmark modelling.

The T2GGM model is described in this short paper: T2GGM TOUGH Symposium.

For additional information, please contact John Avis, P.Eng.