Castle Bravo was the first in a series of high-yield thermonuclear weapon design tests conducted Action by the United States at Bikini Atoll , Marshall Islands , as part of `` Operation Castle '' .

Castle Bravo 's yield was 15 megatons of TNT , 2.5 times the predicted 6.0 megatons , due to unforeseen additional reactions involving Cause_to_be_included Li , which led to Causation the unexpected radioactive contamination of areas to the east of Bikini Atoll .

Operation Crossroads was a pair of nuclear weapon tests Testing conducted Action by the United States at Bikini Atoll in mid-1946 .

A fleet of 95 target ships was assembled Come_together in Bikini Lagoon and hit Attack with two detonations of Fat Man plutonium implosion-type nuclear weapons of the kind dropped on Nagasaki , each with a yield of .

The bomb was known as `` Helen of Bikini '' and was detonated Attack underwater on July 25 , 1946 .

Bikini 's native residents agreed Agree_or_refuse_to_act to evacuate Escaping the island , and were evacuated Escaping on board the `` LST-861 '' , with most moving to the Rongerik Atoll .

In the 1950s , a series of large thermonuclear tests rendered Causation Bikini unfit for subsistence farming and fishing because of radioactive contamination .

Bikini remains Presence uninhabited , though it is occasionally visited Traveling by sport divers .

Like the Crossroads tests , the Sandstone tests were carried out Action at the Pacific Proving Grounds , although at Enewetak Atoll rather than Bikini Atoll .