0018933 six for Oak. The ratio of total fissions, as calculated from the sample analytical data for Mo, Krand kr°® are given in Table 3.1. Also Msted are the R-values _ for sr? and 5137 from the gross particulate samples collected from the cloud at the same time. R-values characteristic of megaton range detonations are 0.77 for sr’? and 0.90 for Cs!2”* Subject to the assumptions inherent in the method, which include among others that the ratio of Mo?? to Kroe in the sampled portion is repres~ entative 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 sampling. Multiplication of these ratios by the cloud R-values and division by the device R-values convert them to the fractions of the nuclides re- maining in the clouds. remaining in cloud. eog- 99 var cloud x rv BEES} clozS device . 0 = fraction of sr? The last step is necessary to correct for the difference in fission yields between device neutrons and thermal neutrons (see Section 1.2.1). The assumption is made here that the Mo9 to sr79 and Cs137 ratios are constant throughou- the cloud. The samples in the table are identified by aircraft numbers as in Appendi: B, to which reference should be made for further details. The calculated fractions of Mo??, sr?° and e513? in the cloud, based on the Kr 88 fission product ratios, are plotted as a function oi tinue in Figures 3.1, 3.2 and 3.3. KrS was not determined on the 27-hour sazples from Walnut and Oak due to its low counting rate at that time. The points on the curves for these shots at 27 hours are hourse On Koa the late-time fission ratio is extrapolated &8 _to-Kr®? ratio at 12 90 and Cs 1 37 and the Sr’ based on the Mo99_to-Kr®? fission ratios corrected by the Kr fractions 73