ESTIMA” 7 OF RADIATION DOSE TO THYROIDS OF THE RONGELAP CHILDREN FOLLOWING THE BRAVO EVENT Ralph A. James Lawrence Radiation Laboratory, 'niversity of California Livermore, Calitornia ,; December 16, 1964 ABSTRAC’ An estimate is made of the radiation dose to the thyroids of Rongelap children following the Bravo event of March 1, 1954. The available experi- mental data are used to estimate the dose under two alternate assumptions of mode of intake: (a) all of the intake was by inhalation, and intake was by oral ingestion. (b) all of the It is concluded that the most probable dose to the thyroid of a 3- to 4-year-old girl is in the range 700 to 1400 rad. GENERAL INFORMATION The cloud arrival time is given! as H+4to6 hours. The duration of the cloud passage is less well known, but probably lies in the range of 8 to 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 H +51 hours. Reliable dose-rate measurements were not obtained at that time, but the gamma dose rate 3 feet above the ground was measured as 375 mR/hour 7 days after the ‘detonation, Assuming pi? decay, the H + 24 hour dose rate was then about 3.8 R/hour. 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 R. 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 > — ! cm FT ? cloud but only from fallout,