The Development and Use of the GGM and T2GGM Codes for the Postclosure Safety Assessment of OPGs Proposed L&ILW Deep Geologic Repository, Canada

Abstract

As part of the postclosure safety assessment of Ontario Power Generation’s (OPG’s) proposed Deep Geologic Repository
(DGR) for Low and Intermediate Level Waste (L&ILW) at the Bruce site, Ontario, a Gas Generation Model (GGM) has been developed
and used to model the detailed generation of gas within the DGR due to corrosion and microbial degradation of the organics
and metals present.
The GGM is based on a kinetic description of the various microbial and corrosion processes that lead to the generation and
consumption of various gases. It takes into account the mass-balance equations for each of the species included in the model,
including three forms of organic waste (cellulose, ion-exchange resins, and plastics and rubbers), four metallic waste forms and
container materials (carbon and galvanised steel, passivated carbon steel, stainless steel and nickel-based alloys, and zirconium
alloys), six gases (CO2, N2, O2, H2, H2S, and CH4), five terminal electron acceptors (O2, NO3, Fe(III), SO4
2-, and CO2), five forms
of biomass (aerobes, denitrifiers, iron reducers, sulphate reducers, and methanogens), four types of corrosion product (FeOOH,
FeCO3, Fe3O4, and FeS), and water. The code includes the possibility of the limitation of both microbial and corrosion reactions
by the availability of water.