Acute and chronic intakes of fallout radionuclides @ S. L. SIMoNn ET AL. As described in Beck et al. (2010), it was also necessary to estimate the degree of fractionation and to modify the reported Hicks (1984) calculations to obtain NDestimates for these estimated fractionation ratios. The estimated fractionation ratios for Bravo for Rongelap, Ailinginae, and Rongerik were 1.4, 1.3, and 1.5, respectively (Becket al. 2010). (3) Relationship between ground deposition den- sity and acute intake. The acute intake was assumed to be instantaneous and to be directly proportional to the ground deposition density of each radionuclide. Thus, the ratio of intake to ground deposition density, in all settings, was assumed to be independent of the radionuclide considered. The ratios of the intakes to ground deposition densities for any radionuclide were, thus, derived from the measured intakes of '*'T and from the 161 atolls are presented in Table | as derived from estimated TOAs (Beck et al. 2010, Table 6). TOAs ranged from about 4 h for Bravo test fallout at Ailinginae to about 170 h for the most distant atolls and, thus, intakes there were assumed to have taken place at 6 h and 238 h post-detonation, respectively. As discussed in Becketal. (2010), the fallout at distant atolls often occurred over extended periods and, therefore, the assumption that all of the intake took place at TOI may, in somecases, result in a slightly conservative estimate of intake for some radionuclides. (2) Ground deposition density at TOI. As discussed above, in case of the Bravo test, the ND factors were calculated taking into account the degree of frac- tionation (Beck et al. 2010). The atom ratios of various nuclides released from the detonations of different nu- corresponding estimates of ground deposition density at Rongelap, Ailinginae, and Rongerik. In summary, the average intakes, Q (Bq), of any clear weaponsvaried dueto differencesin fissile material Ailinginae, and Rongerik, were estimated by means of to thermonuclear tests. Although many radionuclide ratios varied only slightly between the types of test radionuclide, Z, other than '*'I, by adults at Rongelap, eqn (2): and device construction (Hicks 1981). As shown in Beck et al. (2010), the '*'I to '*’Cs ratio was quite insensitive to the particular test, even for non-thermonuclear compared (thermonuclear vs. non-thermonuclear), some of the ND(Z)pravo at TOI O(Z) pravo = OCD pave X ———————_ radionuclide ratios differed significantly, reflecting the different fission yields for **’Pu fission compared to **U (2) Estimation of the intakes by adults of any radionuclide on any inhabited atoll following any test. The methodology used for Rongelap, Ailinginae, and Rongerik following the Bravo test wasalso used for all other tests and all other atolls. The intake of any radionuclide at any atoll was assumedto be proportional to the estimated deposition density of that radionuclide at that atoll, 1.e., the pathways of acute intake were assumed to similar for all atolls and all tests. This simplifying assumption may not be strictly valid for atolls at large distances from the test site where fallout duration was much longer and particle sizes much smaller than at Rongelap. However, we believe that this model provides reasonable estimates of acute intake without any substantial bias at those atolls, though it is recognized that these estimates are more uncertain than the estimates of ‘I intake following deposition of fallout at Rongelap, Ailinginae, and Rongerik from the Bravotest. fast fission. Most of the fission occurring in the thermo- nuclear tests was from fast fission of 7*°U (Glasstone and Dolan 1977). In this work, the radionuclide mixture for the Bravo test was used for deposition-density estimates for all thermonuclear tests, while for non-thermonuclear tests, the radionuclide mixture for the Tesla nuclear test, a typical *’Pu-fueled device tested at the NTS in 1955 (Hicks 1981), was taken to be representative of the non-thermonuclear tests conducted in the Marshall Is- lands (Beck et al. 2010). Regression equations as a function of time for the ND factors for all nuclides considered were developed and used to interpolate the values to specific times not provided by Hicks (1981, 1984), but needed for the estimated times of intake and for the assumed fractionation ratios. Note that because of the long half-life of '*’Cs and the short half-lives of its precursors, the ND values for '’’Cs activity can be considered to be constant and equal to unity over the range of TOAs and TOIs that were considered. The '°’Cs deposition densities at TOI that were used to compute deposition from each test at each atoll from (1) Timeof intake (TOI). Here again, we assumed equations 3 and 4 described below were, therefore, taken directly from Table 7 in Beck et al. (2010). sition, 1.e., TOI = 1.4 X TOA. Estimated TOIs for fallout (3) Relationship between ground deposition density and intake. As indicated above, the relationship that the acute intake at a given atoll following a giventest occurred slightly before midway in the period of depofrom 20 tests for the 26 population groups residing at 25 between ground deposition density and intake, for a