T2GGM Version 2: Gas Generation and Transport Code

T2GGM Version 2 is a software package that can be used to analyze the generation and transport of gases in a deep geologic repository. The current version is V2.1. It is specifically intended for assessment of a repository for low and intermediate level waste, in which there can be significant amounts of organic materials and metals.
This report provides the documentation for the T2GGM software. It includes the theory for the gas generation model, the design documentation with descriptions of the software inputs and outputs, and verification and validation documentation.
T2GGM includes the following capabilities:
- Corrosion product and hydrogen gas generation from corrosion of steels and other alloys under aerobic and anaerobic conditions;
- CO2 and CH4 gas generation from degradation of organic materials under aerobic and anaerobic conditions;
- H2 gas reactions, including methanogenesis with CO2;
- Biomass generation, decay and recycling;
- Exchange of gas and water between the repository and the surrounding geosphere; and
- Two-phase flow of water and gas within the geosphere.
Key results include the gas pressure and water saturation levels within a repository, as well as flow rates of water and gas within the geosphere. T2GGM does not include radionuclide transport and decay.
T2GGM is comprised of two coupled models: a Gas Generation Model (GGM) used to model the generation of gas within a repository due to corrosion and microbial degradation of the various materials present, and a TOUGH2 model for gas-water transport from the repository through the geosphere.