C: -3(4) (5) The composition of the radioactive material at the time of measure- ment is that given in an article by H. F. Hunter and N. E. Ballou, "Fission Produit Decay Rates," published in Volume 9 of Nucleonics, page Ce2, November 1951: The gamma radiation received by the counter from the surface of the fish is as great as would be received from material of the same activity per unit area spread on a plane circular disc 20 cm in radius; (This assumption makes the problem amenable to normal methods of computation. The actual response of the instrument will depend on the size of the fish. This is one of the limitations om accuracy inherent in a practical method of field monitoring.) (6) The level of radioactivity, measured in microcuries per gram of fish, if distributed as assumed in (2) above, should not exceed the value computed for this mixture of radioisotopes on the basis of the re- commendations given in NBS Handhook 52. Examination of the relative maxinum permissible concentrations of the fission products concentrating in various body tissues show that at 1) days or later the tissue receiving the highest radiation dose from the inrestion of the radioactivity will be the bone. Nearly.all of the dose to the bone is due to deposition of the three radioisotopes sr59 sr70 ana 23°40, at 1h days, the respective concentrations of these radioisotopes in residual fallout material are about 3.8%, 0.03% and 13.5%, while the respective maximum permissible concentrations in water listed in Table 3 of Handbook 52, measured in microcuries per gram are 7 x 1079, 8 x 107! and 2 x 1073. If G is the conce:.tration of the gross or total fission product activity in the total supply of food and water which would result in the ingestion these materials at the maximum rate permitted under the recommendations of Handbook 52. 9.073 7x 10-> Gg + 0.0003 g 8 x 107! + (0-135 g = 3 2x 1073 G=1/990=1 x 10°73 microcuries per gram. a _ 79 /? On the basis of assumption (2) above this would correspond to 5 microcuries per square centimeter of surface. On the basis of assumption (5) above, it is estimated that this would result in a radiation level of about 0.1 milliroentgen per hour at 5 cm from the surface. (This is computed by the use of integral calculus, using the following additional information; The average gamma energy emitted per disintegration from this material is approximately 0.35 million electron volts. The intensity of the gamma radiation at a distance r from a point source of radiation is given apzroximately by the equation, T = 5.6 cE/r@, where I is measured in mr/hr, C is measured in microcuries, r is measured in centimeters, and E is the average gamma energy per disintegration measured in millions of electron volts.) Since the conclusion of the recent series of weapons tests in the Pacific Proving Grounds, any radioactive material which might be acquired by fish in DOS ARCHIVES