Fe six for Oak. The fission product ratios none Mo??-to-Kr®* and Mo?2 to-Kr°8 calculated for each shot from the sample analytical data are given in Table 3.1, Also listed are the R-values for Sr 90 and cs!37 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!37, Subject to the assumptions inherent in the method, the fission product ratios give directly that fraction of the total Mo?? formed in the explosion which was left in the cloud at the time of sampling. Maultipli- cation of these numbers by the cloud R-values and division by the device . R-values convert them to the fractions of the nuclides remaining in the clouds. 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 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?9 and Cs!37 in the cloud, based on the Kr88 fission product ratios, are plotted as a function of time in Figures3.1, 3.2 and 3.3. Kr®8 was not determined on the 27-hour samples 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 based on the Mo?9-to-Kr 98 fission product ratios corrected by the Kr 3846.41785 ratio at 12 hours. On Koa the late-time fission ratio is extrapolated and the Sr?9 and C3137 fractions NE Lit SAN BRU 70 7d