It is planned to use hydrogen extensively as a source of clean energy in the new century. As part of our investigation for an International Clean Energy Network Using Hydrogen Conversion (WE-NET), we have been studying to establish a safety scheme to ensure that both existing and new hydrogen technologies are implemented without endangering public safety. In this plan, we consider the transport and storage of a large quantity of hydrogen in a large tank. First we must evaluate the consequence of the postulated accident of liquid hydrogen. Since we have developed the multi-phase hydrodynamics analysis code (CHAMPAGNE), we apply the code to simulate the formation and dispersion of hydrogen vapor clouds. In the present paper we have improved the calculation model in two ways. We added a function to CHAMPAGNE for solving evaporation phenomena realistically, made many parametric calculations and planned the small-scale hydrogen dispersion experiments for the validation of this model. Another improvement is the turbulent mixing of evaporated liquid hydrogen. Now we have completed the basic functions of our simulation code. And these models of CHAMPANGE code must be verified by the experimental data.