Chapter 3 RESULTS AND DISCUSSION ’ 3.1 DISCUSSION AND INTERPRETATION OF THE DATA Tt is noted that the achievement of Objectives 1,2, and 3 depended wholly or in part on the proper functioning of the rocket samplers.. Because of their failure, there are no results to be reported on the vertical and radial distribution of particies in the clouds, which was Objective 3. However, Objectives 1 and 2 were partially met, and 4 was fully met by the aircraft samples. Referring to the nuclides listed in Section 1.3.5, it is to be observed that a number of them were included for the purpose of developing a general background of information on nuclide fractionation. Although this material could serve as the basis for a separate report, it is not being considered here, because it was not a primary concern of Project 2.8. Only the data that has a bearing on the distribution of Sr™ and Cs‘*’ tn the fallout will be covered in this chapter. The radiochemical resuits for each of the different types of samples collected contri- bute something to the overall evaluation. 3.1.1 Cloud Data. For the coincident samples from the light and variable wind layer, there are two sets available for Shot Koa, five for Shot Walnut, and six for Shot Oak. The ratio of total fissions, as calculated from the sample analytical data for Mo", Kr®® and Krare given in Table 3.1. Also listed are the R-values for Sr™® and Cs'*" from the gross particulate samples collected from the cloud at the same time. The measured Sr™ and Cs'*’ R-values for the devices are listed in Tables B.1, B.3, and B.5. Subject to the assumptions inherent in the method, which include among others that the ratio of Mo” to Kr*® in the sampled portion is representative of the entire cloud, the ratio of Mo” fissions to Kr™ fissions gives directly that fraction of the total Mo’ formed in the explosion which was left in the cloud at the time of sam- pling (Appendix E). Multiplication of these ratios by the cloud R-values and division by the device R-values convert them to the fractions of the nuclides remaining in the clouds, e.g., ( Mo”? =z) Kr™/ajoud x R(Sr™) cioud = fraction of Sr® remaining in cloud. 3 RUST) device The last step is necessary to correct for the difference in fission yields between device neutrons and thermal neutrons (Section 1.2.1). The assumption is made here that the ratios of Mo’® to Sr® and Cs‘5* are. constant throughout the cloud. The samples in the table are identified by aircraft numbers, as in Appendix B to which reference should be made for further details. The calculated fractions of Mo”, Sr™, and Cs*" in the cloud, based on the Kr®® fission prod- uct ratios, are plotted-as a function of time in Figures 3.1 through 3.3. Kr*® was not determined on the 27-hour samples from Walnut and Oak because of its low counting rate at that time. The points on the curves for these shots at 27 hours are based on the fission ratios of Mo" to Kr", corrected by the ratio of Kr®® to Kr*® at 12 hours. On Koa the late-timefission ratio is extrap- olated, and the Sr® and Cs!" fractions are calculated from R-values averaged from the partic- ulate samples taken {n the main cloud on the same aircraft as the gas samples. The fractions for Oak are also from averages, here in the light and variable stratum, whereas for Walnut the stabilized condition shown in Figure 3.1 1s used. Sample 980L for Oak is not included because of the poor sampling conditions. The fractions of these nuclides remaining in the cloud after 1 day are given in Table 3.2. 37