4 FREILING, CROCKER, AND ADAMS PREDICTION OF FRACTIONATION EFFECTS Clarification of Concepts If thereader will permit a heterodox interpretation of the title of this subproject, it is appropriate to begin this discussion with the effect of fractionation on thought and communication—the semantic effect, if you will. With a realization of the existence and significance of fractionation, many terms previously used to describe and discuss fallout have become undefined and meaningless. Thus phrases like “bomb fraction,” “fissions in the sample,” and “kilotons per square mile” are no longer “OK terms.” Moreover, as our understanding of fractionation has increased, deviation of fission-product abundances from those expected in instantaneous thermal-neutron fission of *°U and of decay rates from the Way—Wigner t7!? rule are no longer conSidered significant criteria or acceptable measures of fractionation effects. We have considered it an important part of our effort to suggest new definitions and, where possible, operational definitions for many of these terms. These are listed in the appendix to this paper. The essential features of some ofthese definitions are soundly grounded in the fundamental properties of the debris. Accidental features (e.g., the choice of standards for measuring fractionation) can be varied if sufficient justification appears for doing so. Other terms and definitions are merely matters of convenience, and these are appropriately indicated in the appendix. The adoption of these or similar definitions will be of great assistance, not only in promoting clear thinking and improving the signal-to-noise ratio when fractionation is discussed but also in planning analyses of those properties of nuclear debris affected by this phenomenon. Further background and justification for these definitions can be found in our set of reports with the series title ‘Fractionation.”!—4 First Phase of Predicting Fractionation Effects Early in the program we came to the conclusion that the prediction of fractionation effects could best be carried out in two concurrent phases.° The first of these phases consisted of rapidly assembling a prediction system that would give answers to urgent questions in as reasonable a manner as time allowed. The second phase consisted of a more fundamental long-range approach. The effects of interest are gross radiological effects (exposure-dose rate, exposure dose, decay rate, gamma Spectra); radiochemical-composition effects (radionuclide partition between local and worldwide fallout, radionuclide ratios in particles of different size, type, and location, and relative biological availability); effects related to mass deposit (specific activity, mass— dose ratio); and various combinations of these (e.g., '*'I—dose ratio).