In this work, a model for predicting the leakage rate was developed to investigate the effect of irradiation on the sealing performance of ethylene propylene diene monomer (EPDM) O-rings. The model is based on a mesoscopic interfacial gap flow simulation and accurately predicts the sealing performance of irradiated and non-irradiated materials by utilizing the gap height as an indicator in a mechanical simulation of the O-ring under operating conditions. A comparison with vacuum test results indicates that the model is a good predictor of leak initiation. The positive pressure leakage of the O-rings was investigated numerically. The results show the following. The sealing performance of the non-irradiated O-ring is much better than that of the irradiated one. The sealing performance is the worst at 0. 713 MGy and the best at 1.43 MGy, and the seal is maintained at an absorbed dose of 3.55 MGy. A theoretical analysis of the non-monotonic variation using the proposed model shows that the leakage behavior of the O-rings depends not only on the material properties but also on the roughness and prestressing properties. Finally, a method was proposed to classify the sealing performance, using the maximum allowable leakage rate as an indicator.

Prior to salt cavern hydrogen storage operation, the pore space of the surrounding rock is typically saturated with brine. Hydrogen invasion is therefore controlled by gas-liquid displacement, capillary resistance, and phase redistribution rather than by single-phase gas flow alone. In this study, a coupled thermo-hydro-mechanical (THM) model incorporating unsaturated hydrogen-brine transport, heat transfer, and elastoplastic-creep deformation is developed to investigate the effects of operating pressure, injection-withdrawal frequency, and interlayer configuration. Accounting for unsaturated effects reduces the predicted cumulative hydrogen leakage from 6.81% to approximately 0.10% and the volumetric shrinkage from 15.32% to 14.20%. The effective gas-phase permeability is also 2-3 orders of magnitude lower than the intrinsic permeability. Capillary entry resistance, residual brine, and reduced gas-phase relative permeability collectively weaken gas connectivity, restrict far-field pore-pressure transmission, and produce a spatially self-limiting hydrogen migration front. During pressurization, hydrogen transport is dominated by the pressure gradient, whereas capillary effects and gas-liquid redistribution become increasingly important during depressurization. High-permeability interlayers provide preferential migration pathways. Increasing the injection-withdrawal frequency from 1 to 6 cycles/a increases the migration distance by more than 25 m in the most pronounced case. Unsaturated transport produces path-dependent THM feedback, with phase state regulating pore-pressure transmission and effective stress, while deformation feeds back on fluid migration through porosity and permeability evolution.