410176 UNIVERSITY OF WASHINGTON SEATTLE, WASHINGTON 98195 College of Fisheries July 3, 1974 logy ; Laberatory of Radtation Eco Mr. Tommy McCraw Nuclear Explosives Environmental Safety Branch Division of Operational Safety U. S. Atomic Energy Commission Washington, D. C. 20545 Dear Tomny: 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 collected north of Bikini Island in 1974 had slightly higher levels of and 137c¢g compared to mullet collected near Bikini Island in 1969?) but similar levels to concentrations found in mullet collected from Nam in mullet ®9¢o had 1972. The single coconut crab collected on Bikini Island in 1974 had lower levels of 60¢o and 13’cs than the levels found in six eoconut 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). My The concentrations of 60Co 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 50Co and 137cs 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 137Ccs 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. We were unable to collect any crabs on Rongelap Island in 1974. 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