[en] Within the framework of the activitites at EIR related to fast breeder reactor safety, the concept of a molten pool experiment was developed in which freezing phenomena would play an important role. In order to gain some insight into the physical basis of the freezing process the different freezing models in common usage are first reviewed and then, in the context of the experiment envisaged, the heat conduction model of freezing is examined in detail. In this connection a simple analytical expression for crust growth is derived and propagation of the freezing front in a UO2 (or water) bath is calculated. In addition, some basic results given in the literature are discussed in detail, this enabling interesting features of the freezing process to be identified. In summary, the work aims to develop physical understanding of the freezing process in molten pool conditions. (author)