—_— - ann. Operation Ivy was a "high yield" explosion, Test King, from an air drop north of the northwest tip of Runit Island. Associated with the greater yield of Mik§ which was dozens of times greater than previously experienced yields, was a corresponding increase in the ' fallout radiation. Contrary to the usual direction and contrary to expectations, the winds prevailing at the time were from the south or southeast,2. and-so most of the radioactive debris fell on the open seas to the north and northwest. Nevertheless, local fallout did occur on the northern islands of the Atoll. Since these islands continued to be uninhabited, no harm resulted to humans from this local fallout. U.S. tests were conducted only at the Nevada Proving Grounds in 1953, thereupon starting the pattern of tests entirely at the Nevada Proving Grounds or the Pacific Proving Grounds, each on alternate years. The next series of tests in the Pacific was in 1954 under the name Operation Castle.. It involved a task force, which retained the number Task Force Seven of the 1947 force. Five out of the six tests in this series were at Bikini Ato#1, which had not been used for nuclear tests since 1946, and one of these had consequences affecting all testing in the Pacific. “The 15-megaton thermonuclear tests Bravo in this series was conducted on the surface in Bikini Atoll on 28 February 19544210 BEST AVAILABLE COPY The radioactivity of this Bravo event was particularly troublesome by unexpectedly being carried to the east, rather than to the north as had been foreseen. Harmful amounts of radioactivity fell out on the inhabited atolls of Rongelap, Ailinginae, and Rongerik and on the Japanese fishing ship (Lucky Dragon). These events resulted in sharply renewed interest in radiological consequences, with principal focus on the Bikini series of tests. The Atomic Bomb Casualty Commission which had been established after the atomic tow bombing of Japan, became involved. ~ 9. 1n, The Shunkotsu Maru of the Japanese Melvin P. Klein, "Fall-Qut Gamma Ray Intensity" Lawrence Livermore aboratory Rerert, UCRL-5125, (1958) a mee t,o FSs, at ares 4 cee @ etme oe : yee - IRSIRErE ne eT 4