ACE? 4 OFTIStAL USE ONLY UCRL-12378 ESTIMATE OF RADIATION DOSE TO THYROIDS OF THE RONGELAP Ralph A. James UNIVERSITY OF CALIFORNIA Lawrence Radiation Laboratory Lawrence Radiation Laboratory, University of California Livermore, California ar rary CHILDREN FOLLOWING THE BRAVO EVENT Livermore, California Contract No. W-7405-eng-48 December 16, 1964 ABSTRACT An estimate is made of the radiation dose to the ithyrcids of Rongelap children following the Bravo event of March 1, 1954. The available expertmental data are used to estimate the dose under two alternate assumptions of ESTIMATE OF RADIATION DOSE TO THYROIDS OF THE RONGELAP CHILDREN FOLLOWING THE BRAVO EVENT ~ Ralph A. James mode of intake: (a) all of the intake was by inhalation, and (b) all of the intake was by oral ingestion. GENERAL INFORMATION December 16, 1964 s- It is concluded that the most probable dose to the thyreid of a 3- to 4-year-old girl is in the range 700 to 1400 rad, The cloud arrival time ia 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 assumethat cloud passage was in the interval H + 6 to H + 18. ns. The residents of Rongelap were evacuated at H +51 hours. Reliable \ Ouax t ydou 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. 3.8 R/hour. Assuming i? decay, the H + 24 hour dose rate was then about . : - 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 . cloud but only from fallout. Sask} OFFICIAL USE ONLY See PS sagt UES In particular, it appears that this estimate does not include the dose from the ertiaea The whole-body dose was eatimated! to be 175-R. The exact method of making this estimate is not given, #0 an independent entimate isitade below.