APPENDIX 2 # UCRKL 12273 Estimate of Radiation Dose to Thyroids of the Rongelap Children Following the Bravo Event Ralph A. James Lawrence Radiation Laboratory, Livermore, University of California 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 yere evacuated at H +51 hours, Reliable dose rate measurements were not obtained at thar time but the gamma dose rate 3 feet above the ground,was measured as 375 mr/hr seven days after the detonation. ~3.8 rad/hr. Assuming t ~°" decay the H + 24 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 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, phe? 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, equal to the dose from fallout during cloud passage. is then 47 +47 + 114 = 208 rad. is approximately The total estimated dose Within the error of the measurements and the accuracy of the assumptions, this estimate, which does not contain any correction for the small effege of . We time indoors, does not differ significantly from the value of 175 rad will, therefore, take the average whole body gamma dose as 175 + 25 rad.