Internal Deposition of Iodine Isotopes Unfortunately, no direct measurement was possible on the radioactive iodine content of individuals from Roggelap. Urine samples were taken from which the average thyroid burden of I has been estimated. The Los Alamos Scientific Laboratopy collected pooled 24-hour samples 15 days, gost detonation and estimated the l-day thyroid content as 11.2 uc of I. USNRDL collected samples from each member of the exposed group 43 and 46 days post detonation, and, by an in¢girgst method, estimated the average thyroid content as 6.4 uc I at 1549y, The LASL estimate of 11.2 pc was obtained by direct counting of I in the urine and should be more reliable than the NRDL estimate, The value of 11.2 prc will be used as a basis for all following considerations, This estimate was based on the assumption of 0.1% of the maximum thyroid burden being excreted in the urine on the 15th day. Variation in the biological half-life and othey, factors indicate that a range of 0.05 - 0.2% should be placed on this number (see feljowing section by Ng). We, therefore, take 5.6 - 22.4 uc as the range of adult I thyroid burden. The pooled samples represent all age groups. The number of individuals in these age groups,apg the volume of urine from each age group is approximately as follows: ‘"’ age Group <5 5 - 16 > 16 Number of Volume of Individuals Urine(ml) 7 % of Total | Volume 1155 11 31 4.8 4829 18011 20.1 75.0 The urine samples are typical of adults and the calculated thyroid burdens are presumably also those of adults. 135 Associated with this 131, are the shorter lived isotopes 132) 133) and I. If the iodine entered by way of inhalation, the time of intake was H + 6 to H + 18. On the other hand, if water (and food) were the principal source, the time of ingestion would be extended from H + 6 to H +51. Three items contribute to the differences in dose from the various iodine isotopes. These are: (1) radioactive decay before inhalation gr oral ingestion, (2) differences in the fission yields. of the chains, 6 and (3) the average energy deposited in the, ghyroid PSE disinteg ration. These factors are presented in Table I for I and I. inhalation, uniform distribution in the cloud was assumed. it was assumed that, on the average, 2/3 at H + 30. In the case of For oral ingestion 1/3 of the intake occurred at H + 10 and BO