Hydrogen (H2) has emerged as a crucial component of the global energy transition, mainly as an energy carrier for energy storage. Salt caverns are the most appealing and suitable choice for large-scale H2 storage due to their inert properties and general impermeability. Salt caverns have been used to store natural gas and other hydrocarbon materials for several decades. However, few research has investigated the possibility of underground hydrogen storage in Canada. This study investigates the feasibility of underground H2 storage in Lotsberg Salt Formation (LSF) in Alberta, exploring H2 diffusion and potential geochemical reactions. This research hypothesizes that 1) H2 may diffuse into salt rocks and the preferential flow paths for H2 diffusion are grain boundaries and microcracks; 2) diffused H2 may react with salt rock and brine, changing transport properties of the salt rocks; 3) some minerals dissolved in brine such as calcite and anhydrite may react with H2 and cause H2 consumption. To test the hypotheses, this research was conducted in four phases: 1) characterizing salt-rock heterogeneity of Lotsberg salt rocks in terms of mineralogy, crystal size, and pore morphology; 2) measuring helium and H2 diffusion through salt rocks and analyzing salt-rock permeability to H2; 3) evaluating hydrogen geochemical reactions experimentally; and 4) modelling H2-related geochemical reactions. Different salt-rock samples were selected to represent various depths, rock types, and mineralogical compositions along the walls of an existing cavern. Compositional analysis and CT scans were used to assess the mineralogy, crystal structure, and pore characteristics of these samples, investigating the core-scale heterogeneity. Then helium and hydrogen diffusion tests were conducted using a custom-designed cell and a modified pressure pulse decay (PPD) system respectively, evaluating the transport properties of salt rocks. Additionally, experimental H2-related geochemical reactions were conducted, coupled with geochemical modeling using PHREEQC, to predict potential H2-brine-salt interactions, assess the extent of by-product generation, and investigate the corresponding H2 loss and impurities. Lotsberg Salt mainly consists of halite with trace amounts of carbonate impurities, while Lotsberg Marlstone comprises halite with a carbonate matrix containing carbonates, clays, quartz, and muscovite. Helium diffusion through pure and intact halite samples is negligible, and the micro-scale halite crystal boundaries are non-open for helium diffusion. Halite samples with macro-scale grain boundaries and carbonate impurities show higher helium diffusion rates due to the more interconnected pore networks. The formation of secondary halite veins between grain boundaries can lead to tightly sealed boundaries that have poor connectivity, limiting helium diffusion within the sample. We also assessed the permeability of different salt-rock samples. All samples demonstrated ultra-low permeability levels, which validates the effectiveness of the engineered cement barriers used in our trials. However, for salt-rock samples with very small pore sizes (<5-10 nm), the use of advanced slip/Knudsen flow models is required to accurately model hydrogen transport through these samples. The geochemical experiments suggest that non-reductive dissolution is the predominant reaction in the H₂-brine-salt rock systems and that the presence of H₂ does not induce observable redox reactions under the experimental conditions if there is no presence of microbial activity. The geochemical modelling demonstrates that silicate and clay minerals exposed in H2-saturated brine maintain geochemical stability, having negligible effects on H2 consumption. However, the presence of carbonates and anhydrite can induce the dissociation process of H2 in brine and result in the potential production of methane and H2S if considering microbial activity. Though hydrogen loss and by-product generation are expected in salt caverns, kinetic modeling reveals that the time elapsed before such reactions pose any concerns is significantly long. Therefore, caverns developed in salt formations with limited impurities are considered preferable options for underground hydrogen storage.