Abstract: In order to predict the accident scenario caused by total inlet blockage of single subassembly at full power in a fast reactor,a calculational model was developed according to SCARABEE-N subassembly melting and propagation tests.In the model,sodium thermal-hydraulics was described by a two-fluid sub-channel model.The motion of melting cladding and melting fuel was dealt with very simple approach similar to that of SURFASS code.The behavior of UO₂-steel mixed boiling pool was determined by a one dimen-sional semi-empirical model,in which the distribution of void fraction was calculated by drift flux model,heat transfer coefficient between the boiling pool and the wall was determined by modified Greene correla-tion,the temperature field and thickness of solidified UO₂ crust were obtained by solving enthalpy model.Calculation for SCARABEE BE+1 experiment was performed to validate the model,the results approxi-mately agree with the experimental observation.