Es to parts of the gastrointestinal tract as a function of time.) Therefore, Graph Two is based on the activity at time of ingestion to produce one read of dose to the lower intestine. For example, Graph Two shows that if about 48 microcuries are ingested on the 2kth hour after detonation, the lower large intestine may receive one rad of radiation dose. This was calculated in the following manner. Step 1. Determine the total number of disintegrations in the lower large intestine necessary to produce 1.0 rad. From equation (1) (Number of disintegrations) (0.4) 8.0 x 1079) =1 150 Number of disintegrations = 4.7 x 101° Step 2. Determine jhe activity at time of intake to produce 7.7 x 107 disintegrations within the large intestine. 0 4D = 5.2 x 107° aisintegrations intake required (assuming From equation (2) 10% solubility). 5.2 x 101 = (5) (A37) (377°®) 977°"? 5570-27 . A37 © 3.7 x 107 d/hr. Ap, 3 6.2 x 109 a/hr. Ap, = 47 ue * If the time of intake is the 2kth hour, then the start of irradiation of the lower large intestine is 24 + 13 = 37t2 hour. DOE ARCHIVES Graph Two has been used in estimating radiation doses to the lower large intestine for prolonged periods of ingestion (Table Two). The fol- lowing calculations are illustrative for the period of 2kth to the 120th -3-