A dynamic analysis on the sodium purification for removing hydrides was carried out from the model equations, composed of mass transfer in terms of mixing and delay functions, and solubility relationship through the cold trap packed with wire meshes. The solutions were determined using a successive iteration procedure including finite difference calculations and allowed to predict the features of inner variables throughout the cold trap. It was observed that dehydrogenation behavior and hydride build-up could be simulated at various purification performances denoted as a mass transfer coefficient. The results showed that an increased purification efficiency could be obtained by using a cold trap with a higher mass-transfer coefficient at the given sodium stream and cooling conditions. This model was found to be useful for not only crystallizer design and checking the packing performance, but also the prediction of regeneration time and tritium build-up during operations of the cold trap.