Castle Bravo
Castle Bravo was the first in a series of high-yield thermonuclear weapon design tests conducted by the United States at Bikini Atoll, Marshall Islands, as part of "Operation Castle". Detonated on March 1, 1954, the device was the most powerful nuclear device detonated by the United States and its first lithium deuteride fueled thermonuclear weapon. Castle Bravo's yield was 15 megatons of TNT, 2.5 times the predicted 6.0 megatons, due to unforeseen additional reactions involving Li, which led to the unexpected radioactive contamination of areas to the east of Bikini Atoll.
Castle Bravo
A Japanese fishing boat, "Daigo Fukuryū Maru" (Lucky Dragon No.5), came in direct contact with the fallout, which caused many of the crew to grow ill; one died of a secondary infection. This resulted in an international incident and reignited Japanese concerns about radiation, especially as Japanese citizens were once more adversely affected by US nuclear weapons. The official US position had been that the growth in the strength of atomic bombs was not accompanied by an equivalent growth in radioactivity released. Japanese scientists who had collected data from the fishing vessel disagreed with this.