Lawrence Berkeley National Laboratory

Corrosion of steel canisters, stored in a repository for spent fuel and high-level waste, leads to hydrogen gas generation in the backfilled emplacement tunnels, which may significantly affect long-term repository safety. Previous modeling studies used a constant H2 generation rate. However, iron corrosion and H2 generation rates vary with time, depending on factors such as water chemistry, water availability, and water contact area. To account for these factors and feedback mechanisms, we developed a chemistry model related to iron corrosion, coupled with two-phase (liquid and gas) flow phenomena that are driven by gas pressure buildup and water consumption. Results indicate that if H2 generation rates are dynamically calculated based on a chemistry model, the degree and extent of gas pressure buildup are much smaller compared to a simulation in which the coupling between flow and reactive transport mechansism is neglected.