Numerical simulation on dispersion of hydrogen leaked in particle layers of glass beads and soil

Terada, Atsuhiko; Nagaishi, Ryuji

Nuclear Technology, 210(10), p.1871 - 1887, 2024/10

https://doi.org/10.1080/00295450.2024.2302747

In order to understand dispersion of H leaked in packed beds of non-porous/porous particles in a partially open space practically, the dispersion of H in the particle layers of glass beads and soil was analytically studied using a CFD code to be compared with the experiments and to elucidate the effects of particle layer. H flowed out from a single leak point in the particle layer of non-porous glass beads was affected by buoyancy around the leak point, and diffused directly above the leak point in an elliptical shape faster than in the horizontal direction. After that, when it reached the air layer in the head space above the particle layer, H spread horizontally, formed a large concentration gradient near the boundary between the particle layer and the air layer, and further diffused in the air layer until the H concentration became about 1/3 or less of the concentration near the surface of particle layer. The calculations largely reproduced the experimental concentration distributions. When the particle layer was porous decomposed granite soil, the diffusion behavior of H in the particle layer proceeded in the same manner as in the case of glass beads. However, a large concentration gradient was formed near the boundary between the particle layer and the air layer, and then H diffused in the air layer until the H concentration became below the lower combustion limit. It was suggested through sensitivity analysis that the air permeability coefficient had a large effect on the time course of H concentration distribution. Based on the above, we further simulated H behavior in the vessel containing the H leaked particle layer. By inserting multiple vent pipes without considering H generation distribution and particle properties in the particle layer, H accumulated from one pipe was discharged by buoyancy without depending on the H generation distribution and particle properties in the particle layer, and air flowed in from the other pipe.