FRACTION OF TOTAL 0.2 LOCAL FALLOUT 7) 1.0 " WORLDWIDE FALLOUT 0.8 0.4 “d 0.6 0.6 0.4 0.8 E 0.2 FRACTION OF TOTAL WORLDWIDE FALLOUT 0 Fig. 4—-Semiempirical model prediction of radionuclide partition in a land-surface burst. In the case of volatile-chain enrichment under extreme conditions (base surge from an underwater burst or gas venting from a subsurface burst), the ratio of dose rate to the unfractionated dose rate calculated from the mass-95 chain may greatly exceed a factor of 10. Another point of interest predicted by our model is that debris may adhere more closely to the Way—Wigner t™'-? decay ruleif it is fractionated than if it is unfractionated; this is supported by unpublished observations on fallout from weaponstests. Finally, the model has been used to predict the partition of various mass chains amonglocal fallout (particles of 50 or greater in diame- ter), intermediate fallout (particles between 25 and 50 in diameter), and worldwide fallout (particles less than 25u in diameter). The predictions are shown in Fig. 4and are compared in Table 1 with partitions inferred from fallout analysis.*!° The data from the high-yield coral- surface burst are of poor reliability and show only qualitative agree- ment. The data from the low-yield silicate-surface burst agree much better. The agreement is somewhat fortuitous, however, because the