the samples. In general, the land-surface shots deposited more coral] than the water- surface shots, and the inverse relationship applied to sea water. There was rough cor- relation between fraction of the device and the fallout radiation level at the station. 3.5 RADIOCHEMICAL CHARACTERISTICS OF FALLOUT Decay of the fallout activity was observed by measuring three separate activities: beta disintegrations per minute, gamma photons, and gammaionization. The measured data are summarized in Figures 3.12, 3.13, and 3.14. The beta-decay curve was also calculated by adding contributions from fission products and activities induced in device components (Figure 3.15). These curves were used to extrapolate activity measurements to a common time. Radiochemical studies of the samples have yielded data on capture-to-fission ratios and R-values. (R-values are an indication of the relative abundance of a particular nuclide as compared to its normal abundance in fission products from slow-neutron fission of U5, ) The most-important neutron-~capture activities were due to Np™*, U5", and U2“. The R-values were measured for Sr*?, Ag!!! cdl§, Bal? cel, naif? Sm!53 | Eu5s | Gd! and Tb! using Mo*? as a reference nuclide. The measured capture-to-fission ratios are summarized in Table 3.2. Usually, the R-values for the cloud and fallout samples were consistent. The R-values for the rare earths Agitt and Cd!!5 were usually greater than unity, indicating an enrichment of these isotopes compared to slow-neutron fission products of U™5. The R-values for Sr®® were usually less than unity. Detailed results are reported in the final reports of Projects 2.6a and 2.6b (see Appendix). Two methods of performing material-balance calculations were used: (1) the fraction of the device was computed using a radiochemical Mo" determination as a tracer for the number of fissions contributing to the sample and (2) the absolute beta count of a sample was related to a calculation of beta activity of fission products and induced activities reSulting from fission of a certain number of atomsat various times, as in Figure 3.15. 53