Castle Yankee was the code name given to one of the tests in the Operation Castle series of American tests of thermonuclear bombs . It was originally intended as a test of a TX-16 / EC-16 '' Jughead '' bomb , but the design became obsolete after the Castle Bravo test was successful . The test device was replaced with a TX-24 / EC-24 '' Runt II '' bomb which was detonated on May 5 , 1954 , at Bikini Atoll . It released energy equivalent to 13.5 megatons of TNT , the second-largest yield ever in a U.S. fusion weapon test
Castle Bravo
Castle Bravo
Castle Yankee