Introduction of tritium transfer step at surface layer of breeder grain for modeling of tritium release behavior from solid breeder materials

It has been observed in modeling of the tritium release behavior from solid breeder materials by the present authors that the overall mass transfer coefficients representing such surface reactions as adsorption or isotope exchange reactions on breeder surface should be as small as one-several thousandth of the coefficients obtained from experiments where tritium was introduced to the breeder surface from the purge gas. The mass transfer resistance representing tritium transfer from grain surface layer to surface water is newly introduced in this study. It is considered that the mass transfer resistance when tritium is transferred from gas phase to surface water is the same as that from surface water to gas phase. The estimated tritium release curves using the new model presented in this study give good agreement with the observed tritium release curves from Li4SiO4, Li2TiO3, Li2ZrO3 or LiAlO2. Comparison of the estimated release curve with the experimental release curve is discussed in this study for the case when a purge gas with water vapor is applied to extract bred tritium from various solid breeder materials.