NUCLEAR-DEBRIS FORMATION a a a a Ltit | Guilt COOLING RATE, °K/ SEC a 15 1 KT 10 KT 3 444 100 KT 1 MT 10 MT 100 MT WwW Fig. 8&—Cooling rates as a function of temperature and total weapon yield, predictions made with the thermodynamic equilibrium model is sensi- tive to yield.* Examination of the previous figures clarifies the nature of another approximation used by the present system. The equilibrium treatment considers fallout formation to occur in two distinct stages. According to this approach, the particles during the first stage form an assembly of liquid drops, and condensing radionuclides distribute themselves among the particles in proportion to their volumes. At 1400°C the particles solidify, and further condensation results in surface distributions. The diffusion data in Fig. 7 show no breaks, either in the neigh- borhood of 1400°C or anywhere else, for any of the silicates studied. *Unfortunately, Hillendahl’s equations are based on data which do not extend below 2000 degrees. Below 2000 degrees radiation becomes less important as a means of cooling than other processes, especially the enguifment of cold air. The cooling rates estimated here are therefore merely lower limits. Storebd*! has attempted to accountfor the engulfment of cold air in air bursts. His cooling equations lead to cooling rates of the order of 103 degrees per second at 1400°C.