Experiments using a small-scale apparatus with 30 ml of actual high-level liquid waste from the Tokai Reprocessing Plant were carried out to show that the hydrogen concentration in the gas phase reaches a steady-state value of much less than 4% (lower explosive limit) in the absence of sweeping air. The H2 concentration reached a steady-state value as was expected, and it was compared with a value predicted from an equation with parameters that had been obtained using the simulated solution. Satisfactory agreement showed that the Pd-ion catalytic H2 consumption reaction previously found in the simulated solution proceeded equally well in the actual solution.