410301 UNIVERSITY OF WASHINGTON SEATTLE, WASHINGTON 98195 College ot Fishertes July 3, 1974 Tathor wor of Radiation Ecology Mr. Tommy McCraw Nuclear Explosives Environmental Safety Branch Division of Operational Safety U. S. Atomic Energy Commission Washington, D. C. 20545 Dear Tommy: Gamma-spectrum analysis of the 38 samples collected in April, 1974, on Bikini Island and Rongelap Atoll, and later selected for analysis during FY 1974 as outlined in the Second Supplement to the Johnston Atoll Bioenvironmental Program, has been completed. After division of the fish and coconut crabs into tissue fractions, a total of 57 gamma-spectrum analyses were performed. The results of these analyses are given in Tables 1 through 5 which are attached. The gamma-emitting radionuclide content of the single goatfish collected about two miles north of Bikini Island is less than the levels found in goatfish collected near Bikini Island in 1969 and near Nam Island in 1972. The mullet collected north of Bikini Island in 1974 had slightly higher levels of 60¢o and 137¢s compared to mullet collected near Bikini Island in 1969, but had similar levels to concentrations found in mullet collected from Nam in 1972. The single coconut crab collected on Bikini Island in 1974 had lower levels of 60¢o and 13’7cg than the levels found in six coconut crabs collected on Bikini Island in 1969 (i.e, a 137cs level in the muscle of 380 pCi/g, dry, versus a range of 429 to 933 pCi/g, dry, in the six 1969 crabs). The concentrations of ®0¢o and 137cs in the coconut crabs from Rongelap Atoll are less, by factors of 4 to 10, than those found in the Bikini crab. Crabs from Kabelle Island, located at the northeast tip of Rongelap Atoll, had higher levels of ©0¢o and 137¢s compared to crabs from Busch and Arbar Islands in the southern part of the atoll. A single coconut crab collected on Rongelap Island in 1971 had muscle, hepatopancreas, and exoskeleton 137¢5 concentrations of 32, 35, and 7.9 pCi/g, dry, respectively. These levels, except for the muscle concentration which is slightly lower, are similar to those found in the crabs collected on the other islands in 1974. unable to collect any crabs on Rongelap Island in 1974. We were The results of the analyses of the soil profiles indicate that most of the gamma-emitting radionuclides are found in the surface 25 cm of soil. Cesium-137, however, is detectable even in the deepest samples from all three profiles and