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 Yankee
Although it had been predicted to produce a yield of 6 to 10 megatons, it actually produced a yield of 13.5 megatons, the second-largest ever yield in a U.S. fusion weapon test. Like the Mike, Bravo and Romeo tests, a large percentage of the yield was produced by fast fission of the natural uranium tamper. Of the total yield, 7 megatons were from fission; the other 6.5 megatons were from fusion reactions. The high fusion yield was due to the enriched fuel and set a U.S. record that stood until Hardtack Poplar in 1958.