The United States tested a 15-megaton thermonuclear bomb in 1954 at Bikini Atoll. What was the name of this test?

• A. Castle Bravo
• B. Ivy Mike
• C. Sedan
• D. Bravo

Answer: (A)

This question asks you to name the U.S. nuclear test conducted at Bikini Atoll in 1954 that yielded about 15 megatons. That test is Castle Bravo. It was the first test of Operation Castle and the largest U.S. atmospheric nuclear device tested to date, marking a pivotal step in thermonuclear weapon development using a two-stage design with lithium deuteride fuel.

Ivy Mike was the first full-scale thermonuclear test, but it happened in 1952 at Enewetak Atoll and involved a different setup and yield. Sedan was a Nevada test in 1951 focused on crater formation with a much smaller yield and not at Bikini. The name Bravo appears in some references, but the formal designation for this high-yield Bikini Atoll test is Castle Bravo, which is why it’s the best match.