The pressure-temperature history model of incipient boiling of liquid alkali metals is applied to a single subassembly blockage accident of a liquid-metal-cooled fast breeder reactor (LMFBR) where boiling is caused by a sudden flow stoppage with continued heating. The model predicts that the maximum superheat that would be expected to occur under most LMFBR operating conditions for this type of accident is 50 to 100°C. Several mechanisms are indicated, however, that can reduce this value, such as failed fuel, entrained gas, etc.