APPENDIX 2 = UCRL 12273 Estimate of Radiation Dose to Thyroids of the RongelapChildren Following the Bravo Event Ralph A. James Lawrence Radiation Laboratory, University of California Livermore, California December 16, 1964 General Information The cloud arrival time is given‘!) as H +4 to 6 hours. The duration of the cioud passage is less well known but probably lies in the range of 8 - 16 hours. In all calculations we will assume that cloud passage was in the interval H + 6 to H + 18. The residents of Rongelap were evacuated at dose rate measurements were not obtained at that rate 3 feet above the ground was measured as 375 the detonation. Assuming t decay the H + 24 ~3.8 rad/hr. H+ 51 hours. Reliable time but the gamma dose mr/hr seven days after hour dose rate was then The sources of exposure to the thyroid which must be considered are: (1) Whole body gamma dose. (2) Internal deposition of iodine isotopes. Whole Body Gamma Dose . 1 The whole body dose was estimated ) to be 175 rad. The exact method of making this estimate is not given, so an independent estimate is made below. In particular, it appears that this estimate does not include the dose from the cloud but only from fallout. If we assume a linear buildup of fallout from H + 6 to H + 18, pl? decay during this interval and use the reading of 375 mr/hr at seven days, the estimated dose from fallout during cloud passage is 47 rad. The dose from the fallout from H + 18 to evacuation at H +51 is 114 rad. Experience from Sedan indicates that the dose from the cloud, itself, is approximately equal to the dose from fallout during cloud passage. The total estimated dose is then 47 + 47 + 114 = 208 rad. Within the error of the measurements and the accuracy of the assumptions, this estimate, which does not contain any correction for the small effect of time indoors, does not differ significantly from the value of 175 rad . We will, therefore, take the average whole body gamma dose as 175 + 25 rad.