of surface-particle activity might provide an explanation, contrary evidence exists in the rapid initial settling rates observed in some profiles, the solid nature of many particles from which only ~ 20 percent of the activity is leachable in 48 hours, and the behavior of Zuni fallout in the YAG 39 decay tank. Relative concentrations of 34, 56, and 100 were observed for samples taken from the latter under tranquil, stirred, and stirred-plus-acidified conditions. (Based on this information and the early Shot Tewa profiles of Figure 3.10, the amount lost is estimated at about 50 percent at the YAG 39 locations in Reference 20.) If on the other hand it is assumed that a certain amount of activity was lost to greater depths, then the curious coincidence that this was nearly equal to the deficit of the maximum OCC collection must be accepted. It is unlikely that any appreciable amount of activity was lost below the stirred layer follow- ing Shots Flathead and Navajo. No active solids other than the solids of the slurry particles, which existed almost completely in sizes too small to have settled below the observed depth in the time available, were collected during these shots (Section 3.3.2). In view of these considerations and the relative reliability of the data (Section 4.2), it is recommended that the maximum platform collections (Table B.12) be utilized as the best estimate of the total amount of activity deposited per unit area. An error of about +50 percent should be associated with each value, however, to allow for the uncertainties discussed above. Although strictly speaking, this procedure is applicable only in those cases where single-wind deposition prevailed, it appears from Table 4.6 that comparable accuracy may be achieved for cases of multiwind deposition by retaining the Same percent error and doubling the mean platform value, 4.3.3 Gross Product Decay. The results presented in Section 3.4.6 allow computation of several other radiological properties of fission products, among them the gross decay exponent. Some discussion is warranted because of the common practice of applying a t~1-* decay function to any kind of shot, at any time, for any instrument. This exponent, popularized by Reference 58,is apparently based on a theoretical approximation to the beta-decay rate of fission products made in 1947 (Reference 59), and some experimental gamma energy-emission rates cited in the same reference. Although these early theo- retical results are remarkably good when restricted to the fission-product properties and times for which they were intended, they have been superseded (References 41, 60, 61, and 62); and, except for simple planning and estimating, the more-exac: results of the latter works should be used. ‘ If fractionation occurs amongthe fission products, they can no longer be considered a standard entity with a fixed set of time-dependent properties; a fractionated mixture has its own set of properties which may vary over a wide range from that for normal fission products. Another source of variation is induced activities which, contrary to Section 9.19 of Reference 47, can significantly alter both the basic fission-product-decav curve shape and gross property magnitudes per fission.| The induced products contributed 63 percent of the total dose raz in the Bikini Lagoon area 110 hours after Shot Zuni; and 65 percent of the dose rate from Shot Navajo products at an age of 301 days was due to induced products, mainly Mn™ and Ta’. Al- though many examples could be found where induced activities are of little concern, the a priori’ assumption that they are of negligible importance is unsound. Because the gross disintegration rate per fission of fission products may vary from shotte shot for the reason mentioned above, it is apparent that gamma-ray properties will also vary, and the measurement of any of these with an instrument whose response varies with photon eaergy further complicates matters. -1.2 Although inspection of any of the decay curves presented may show an approximate t ‘average decay rate when the time period is judiciously chosen, it is evident that the slope “s continuously changing, and more important, that the absolute values of the functions, e.¢-photons per second per fission or roentgens per hour per fissions per square foot, vary Cv" siderably with sample composition. nite As an example of the errors which may be introduced by indiscriminate use of thet ~ -~ 120