Castle Bravo

Castle Bravo
Castle Bravo mushroom cloud
Information
Country	United States
Test series	Operation Castle
Test site	Bikini Atoll
Date	March 1, 1954
Test type	Atmospheric
Yield	15 Mt (approx. 63 PJ)

SHRIMP
The SHRIMP device in its shot cab
Type	Teller-Ulam design thermonuclear weapon
Production history
Designer	Ben Diven-project engineer
Designed	24 February 1953 (GMT)
Manufacturer	Los Alamos National Laboratory
Unit cost	About $2,666,000 (1954 USD)
Produced	October 1953 (GMT)
Number built	1
Variants	TX-21C, TX-26
Specifications
Weight	10,659 kilograms (23,499 lb)
Length	455.93 centimeters (179.50 in)
Diameter	136.90 centimeters (53.90 in)
Filling	Lithium-6 deuteride
Filling weight	400 kilograms (880 lb)
Blast yield	15 megatons of TNT (63 PJ)

Castle Bravo was the code name given to the first United States test of a dry fuel hydrogen bomb, detonated on March 1, 1954, at Bikini Atoll, Marshall Islands, as the first test of Operation Castle. Castle Bravo was the most powerful nuclear device ever detonated by the United States, with a yield of 15 megatons of TNT (30% of the energy produced by the most powerful device ever detonated, the Tsar Bomba). That yield, far exceeding the expected yield of 4 to 8 megatons, combined with shifting winds, led to the most significant accidental radioactive contamination ever caused by the United States.

Fallout from the detonation—intended to be a secret test—fell on residents of Rongelap and Utirik atolls and spread around the world. The islanders were not evacuated until three days later and suffered radiation sickness. They were returned to the islands three years later but were removed again when their island was found to be unsafe. The 23 crewmembers of the Japanese fishing vessel Daigo Fukuryū Maru ("Lucky Dragon No. 5") were also contaminated by fallout, experiencing acute radiation syndrome. The blast created an international reaction about atmospheric thermonuclear testing.

The device was a very large cylinder weighing 23,500 pounds (10.7 t) and measuring 179.5 inches (4.56 m) in length and 53.9 inches (1.37 m) in diameter. It was mounted in a "shot cab" on an artificial island built on a reef off Namu Island, in the Bikini Atoll. A sizable array of diagnostic instruments was trained on it, including high-speed cameras trained through an arc of mirror towers around the shot cab.