TRANS URANIC RADIONUCLIDES IN ENEWETAK LAGOON 581 



unclassified documents (U. S. Atomic Energy Commission, 1973; Circeo and Nordyke, 

 1964; Hines, 1962), explams a few conditions responsible for the transuranic distribu- 

 tions and inventories at the Atoll. 



The test series at Enewetak began in 1948 (Operation Sandstone) when 37-, 49-, and 

 18-kt devices were detonated from 200-ft towers on the islands of Janet, Sally, and 

 Yvonne between April 14 and May 14. In 1951, testing was resumed (Operation 

 Greenhouse), and four tower shots were conducted during a 47-day interval. The island of 

 Janet was again the location of two ground zeros. In 1952, the first thermonuclear device 

 (Mike) destroyed the island of Flora on the northwest reef. The Mike event, a 10.4-Mt 

 surface detonation, occurred on October 31. Water surging from the point of the 

 explosion sent a wave over adjacent islands, including Janet, the site of three previous 

 ground zeros. The original crater where Flora had once been had an irregular outline and 

 was more than 1 mile in diameter. Before the crater was partially refilled by the returning 

 rush of coral sediment, it was almost 200 ft deep; it is presently 90 ft deep. The 1952 

 series of tests concluded with the King event, a high-yield airdrop over Yvonne Island. In 

 1954, a single device. Nectar, was detonated on a barge located over Mike crater. Not 

 only did this test greatly disturb the radionuclides already deposited in the crater 

 sediments but it also again sent a surge of contaminated water over adjacent islands, 

 including Janet. In 1956, the Redwing series began with a tower detonation on Yvonne 

 and included two additional cratering events, LaCross and Seminole. LaCross was a 

 39.5-kt device detonated on an earth-filled causeway built on the reef off the north end 

 of Yvonne. Seminole, detonated on the island of Irene, was first placed in a 

 15-ft -diameter tank that was itself then placed in a 50-ft -diameter tank filled with water 

 before it was fired. During 1958, the final year of testing at Enewetak, 22 tests of various 

 types were held at different Atoll locations during an 82-day period. The series opened 

 with an 86,000-ft balloon shot over the Atoll on April 28. On May 5, an 18-kt device 

 produced Cactus crater on the northwest end of Yvonne and west of LaCross crater. 

 During May 1 1 and 12, one of three tests conducted was the Koa event, a 1 .37-Mt nuclear 

 device housed in a tank of water and detonated on the east end of the Gene— Helen island 

 complex. A sizable crater was produced, which connected with Mike crater. On June 8, 

 the Umbrella device was detonated on the floor of the lagoon. Twenty days later, the 

 8.9-Mt Oak device was fired on a barge 4 miles southwest of Alice off the edge of the 

 reef. The test left a crater that breached to the lagoon. The Quince event on Yvonne 

 Island failed to produce a fission yield; so the plutonium within the device was dispersed 

 by a high explosive. Subsequently another nuclear device was successfully detonated over 

 the same area and undoubtedly further dispersed the nonnuclear -generated plutonium. In 

 addition to the nuclear tests, radionuclides were dispersed by plowing on many of the 

 islands during the test years. Unfortunately, none of the radiological safety reports during 

 these operations provided details to determine the eventual fate of the radioactive debris, 

 e.g., location and quantity of the disposal (U. S. Atomic Energy Commission, 1973). 



From this brief summary, we can assume safely that the transuranic elements were 

 introduced to the aquatic environment not only as complicated carbonate particles fused 

 or condensed with other material from the environment or with devices and associated 

 structures but also as soluble and particulate species of transuranium oxide. 



Despite the complexities in the formation processes, much of the behavior of the 

 transuranics is similar to that determined from investigations of fallout and other aquatic 

 pathways. The results from the Atoll studies therefore have great value in predicting 

 transuranic behavior and fate on a global aquatic scale. 



