of the observed amount of a given nuclide to the amount expected from thermal neutron fission of u’™, relative to some reference nuclide, combine the effects of fractionation and variations in fission yield and contain a number of experimental uncertainties. Values between 0.5 and 1.5 cannot be considered significantly different from 1.0.) Selected particles were also weighed so that the numberof fissions per gram could be computed. Radioactivity measurements were made in the gamma well counter (WC) and the 4-7 gamma ionization chamber (GIC), both of which are described in Section 2.2. Because the efficiency of the former decreased with increasing photon energy, while the efficiency of the latter increased, samples were often assayed in both instruments and the ratio of the two measurements (counts per minute per 10¢ fissions to milliamperes per 104 fissions) used as an indication of differences in radionuclide composition. It will be observed that the particles in Table B.7 have been classified according to color and shape. For purposes of comparing radiochemical properties, spheroidal and agglomerated par- ticles have been grouped together and designated as “altered particles,” while irregular particles have been designed “unaltered particles.” The latter should not be interpretedliterally, of course; it will be evident from the foregoing section that the majority of irregular particles have undergone some degree of chemical change. Particles were classified as altered if they exhibited the obvious physical changes of spheroidal or agglomerated particles under the optical microscope. Radiochemical results for all altered and unaltered particles from Shot Zuni are summarized in Table 3.9, and activity ratios of the particles from this shot and Shot Tewa are compared in Table 3.10. The differences in radiochemical composition suggested in the tables are emphasized in Figure 3.20, which shows how the energy-dependent ratios (counts per minute per 10* fissions, milliamperes per 10‘ fissions and counts per minute per milliamperes) varied with time, and in Figure 3.21, wherein the data used for computing the R-values and product/fission (p/f) ratios (number of atoms of induced product formed per fission) in Tables B.7 and B.8 are Presented graphically by plotting the numbers of atoms of each nuclide in a sample versus the mumber of atoms of Mo**’. Data obtained from calibration runs with neutron-irradiated U?® are Plotted in the former for comparison; and the standard cloud sample data for Np*"®, as well as those derived from the estimated device fission yields for Ba‘4° and Sr*®’, are included in the latter. It is interesting to note that these results not only establish that marked differences exist between the two types of particles, but also show the altered particles to be depleted in both Bai“*_12'40 and Sr®®, while the unaltered particles are enriched in Ba‘*-La!° and perhaps slightly depleted in Sr®*, The altered particles are also seen to be about a factor of 100 higher than the umltered in terms of fissions per gram. When these R-values are compared with those obtained from gross fallout samples (Tables 3.17 and 3.21), it is further found that the values for altered Particles resemble those for samples from the lagoon area, while the values for the unaltered Particles resemble those from cloud samples. Activity Relationships. All of the particles whose gammaactivities and physical Properties were measured in the YAG 40 laboratory (Table B.34), as well as several hundred additional particles from the incremental collectors on the other ships and barges, were studied Systematically (Reference 30) in an attempt to determine whether the activities of the particles Were functionally related to their size. These data are listed in Table B.9 and the results are ed in Figures 3.22 and 3.23. Possible relationships between particle activity, weight, and nsity were also considered (Reference 25), using a separate group of approximately 135 parles collected on the YFNB 29 during Shots Zuni and Tewa and the YAG 39 during Shot Tewa oly; Figures 3.24 and 3.25 showthe results. As implied by the differences in radiochemical composition discussed in the preceding section, clea differences exist in the gamma-radiation characteristics of the different types of parti- . Compared with the variations in decay rate and energy spectrum observed for different Particles collected at about the same time on the YAG 40 (Figures B.2, B.3 and B.4), altered erences show large changes relative to unaltered particles. Figures 3.26 and 3.27 from Refe 26 illustrate this point. The former, arbitrarily normalized at 1,000 hours, shows how 51