10 . FREILING, CROCKER, AND ADAMS Table 1~-COMPARISON OF RADIONUCLIDE PARTITIONS PREDICTED BY THE SEMIEMPIRICAL METHOD WITH OTHERS INFERRED FROM ANALYSIS OF NUCLEAR DEBRIS _ Predicted fractions Radionuclide Local Intermediate* Worldwide BICs ar Sr M40Ba— Mp4, 132Te %27r—*Nb %3Mo (coral) 0.1 0.1 0.15 0.25 0.25 0.65 0.65 0.1 0.1 0.1 0.1 0.2 0.2 0.1 0.8 0.8 0.75 0.65 0.65 0.25 0.25 Fractions in 24-hr cloud of a highyield, coralsurface burst 0.36 + 0,36 0.11 + 0.11 0,02 + 0.02 Fractions in a low-yield, Silicate-surface burst Local Intermediatet Worldwide 0.00 0.02 0.07 0.20 0.18 0.72 0.72 0,22 0.24 0.24 0.26 0.26 0.19 0.19 0.78 0.74 0.69 0.54 0.56 0.09 0.09 *Intermediate fraction taken as 25 to 50 yw in diameter, tIntermediate fraction taken as 18 to about 90 » in diameter. particle-size distribution in the latter case differed considerably from that used in the model. In summary, the present state of the art puts us in the position of the meteorologist who has to predict the weather even though he can’t. We make the most reasonable attempt our knowledge permits and cross our fingers. Second Phase of Predicting Fractionation Effects We will now discuss the second, long-term phase of predicting fractionation effects, the phase concerned with piecewise refinement of weak links in the calculational chain. Figure 5 showsthe fallout- formation processes that have to be taken into account in a fundamental approach, Our thinking on this is still the same as when we presented this diagram at the last conference.’ Perhaps the weakest links are the definition of particle size and the absence of accounting for agglomeration effects, and next inimportanceis the transition from an equilibrium (thermodynamic) to a nonequilibrium (kinetic) approach. However, the definitive work being done by Russell on the first problem’? and the need to properly plan our high-temperature experimental work has led us to attack the last problem first. Our efforts in this direction form the subject of this section of the report. One should not jumpto the conclusion that the thermodynamic equilibrium treatment is inapplicable or that, even if it were, thermodynamic data are no longer required. AS will be seen, each approachhasits place in the overall development. The plan of developing a kinetic model has been, first, to decide on a mechanism; second, to assemble useful, available theoretical and experimental results; and, third, to integrate these and fill in the missing steps to obtain the complete treatment. We are now in stage two. We are obviously not concerned so muchat this point with developing a new theory of fallout formation as with the application of established theory.