Qe hour (start of intake at the beginning of the Ond day after detonation for a duration of four days). Step 1. , Determine the mumber of microcuries at time of ingestion to produce 1.0 rad to the lower large intestine. From Graph Two take the mid point of intake period (72nd hour)-»31 yc. (This is obviously an approximation since the exact times of intake during the four-day period will be unknown). Step 2. Determine the activity at time of intake. From equation (2) 31 s 5 Aok 21.2 [sO _ 120 ~0-27 Ap, = 0.94 ue/hr Since there is assumed a 220 mi/day intake 0.94 x 2k 2200 = 0.010 ue/m) or em IZ. Doses to the Thyroid The following principal assumptions sre used in calculating the doses to the aduit thyroid from intake of activity from fallout material: @. The percentages of the isotopes of iodine in mixed fission products are according to Hunter and Balisu.> b. Twenty percent of the ingested r31 reaches the thyroid. c. The mean energy is 0.22 Mev. d. ‘The thyroid weight is 20 grams. e. The percentages of shorter-lived isotopes of iodine that (See IV. Discussion below) reach the thyroid and their doses are according to reference four. DOE ARCHIVES The method of calculation of doses to the thyroid is illustrated by com- puting that amount of intake of fission products at the 48th hour -ke