The effect of a local cooling disturbance caused by an edge-type blockage in a liquid-metal fast breeder reactor (LMFBR) fuel subassembly was investigated with a series of out-of-pile local blockage experiments with water and sodium. The heat exchange layer model first developed for central-type blockage cases applied well to the present edge-type cases. An empirical formula was developed for estimating maximum temperatures in various subassemblies, and the conclusion was reached that a middle size edge-type blockage could lead to sodium boiling. The critical heat flux data of Power Reactor and Nuclear Fuel Development Corporation and Kernforschungszentrum Karlsruhe were correlated with the boiling inception heat flux for various core flow velocities. A linear relation was found between them, suggesting a possible interpretation of the coolability limit within the framework of nonboiling conditions. The theoretical (hypothetical) excess temperature in the absence of boiling, ΔTms (= Tmax − Tsat), seemed to cross a critical value at the instance of permanent dryout. Based on the constant critical ΔTms assumption and the formula for Tmax, an assessment was made of the thermohydraulic consequences for the different blockage size situations of a typical LMFBR.