-69- AECD-3446 A decay curve of the calcium oxalate isolated from the coral sands of Runit gland collected 200 yards from the crater and counted in a RCL nucleometeris a hown in Figure 1. From this data the half-life of the radioactive substance antes is 180 + 5 days. This corresponds to the accepted half-life for ca4® The results obtained from the chemical separation and the decay curve “pdicate the presenceof ca*®, That it is present in sufficient quantity to be a “dfinite factor in tt.e survival of the plants in the immediate vicinity of the bomb 45 ter is yet to be proved, It is quite evident that Ca constitutes a significant * BE tion of the total radioactivity to which the plants are subjected. This fraction B‘as been deposited within the plants by the normal process of absorption and transre ‘ioc tion. These plants are short-lived and consequently have grown from seed } “since the "test", their normal complement of calcium having been acquired from te coral sands irradiated by the neutron shower. This acquisition of radioactive “material is in sharp contrast to the acquisition of fission products on the surface ‘uquired by direct fallout or by particles "splashed" upon the plant by the action of misdrops on the surface of the soil containing the fission products. e The specific activity (Cat 5 Ca) of plant material and coral sand collected thirty and two hundred yards from the crater on Runit Island is shown in Table 3. Two facts become evident after study of Table 3: (1) Procedure I with limited i : venging is insufficient to removeall fission products as is shown by the lower ‘ecitic activity following the additional scavenging or Procedure II; and (2), the ‘Becific activity of the calcium in the plant material decreases with distance from & crater. When corrections are made for the angle of incidence of the soil sur- lice with the geometric center of the explosion!, the observed results at the two ites agree within 15% of the calculated expected results based on adherence to the verse square law, Under the circumstances of: (1) the elapsed time to collection * samples, (2) the possibilities of mechanical redistribution, (3) irregularities of bl surface and (4) bomb peculiarities, this result is regarded as being highly Patifyi g. It lends much weight to the general conclusions regarding the presence aa 5 in the plants. “Based on the assumption tnat the explosion was initiated atop a 200-foot tower.