This research developed a Kinetic Monte Carlo (KMC) method for simulating hydrogen diffusion in tungsten bulk. The KMC inputs such as diffusion paths and energy barriers are taken from DFT calculation results from the literatures. In this simulation model, stable hydrogen interstitial sites in tungsten are the tetrahedral sites on each surface of the bcc lattice, and each site has four tetrahedral neighboring sites, with two neighbors on the same lattice surface and the other two on the adjacent two perpendicular surfaces. A MATLAB script has been developed to perform the diffusion modeling for any given hydrogen concentration and substrate temperature. To compare the simulation results with experiment measurements, modeling configuration of low hydrogen concentration and temperature of 300 K to 2500 K mirroring the experiment conditions was used. The calculated diffusion coefficients at various temperatures match the experiment reference very well. The calculated diffusion coefficients are also fitted to the Arrhenius equation as:

D [m2/s] = 5.59×10−7 exp(−0.426/kBT)

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