AbstractA generalized method for estimating the energy release in hypothetical fast-reactor meltdown accidents is formulated. A modification of the Bethe-Tait method is derived from this more general formulation, and comparisons are made to an improved method, programmed for the IBM-7090 computer. Two basic assumptions are utilized: that the reactivity effects during disassembly can be calculated from perturbation theory, and that the decrease in density during disassembly can be ignored in the equations of hydrodynamics. It is shown that the threshold equation of state used in the Bethe-Tait method tends to cause an overestimate of the energy release for weak and moderate excursions, and that the saturated vapor pressure must be considered in those cases. The dependence of energy release upon prompt-neutron generation time, initial power level, rate of reactivity insertion, and Doppler effect is investigated.