Castle Yankee

Castle Yankee was the code name given to one of the tests in the Operation Castle series of American tests of thermonuclear bombs.

Jughead

Yankee was originally intended to be a test of a simplified and lightened bomb version (the TX-16, or "emergency capability" EC-16) of the large and complex cryogenic device (the first successful multi-stage fusion device) tested in Ivy Mike. A small number of EC-16s were produced on an emergency basis to provide a stop-gap thermonuclear weapon capability in response to the Russian nuclear weapons program.

The test device, code-named "Jughead", had been prepared as a backup in case the non-cryogenic "Shrimp" fusion device (first tested in Castle Bravo) failed to work. The test of "Jughead" was cancelled when the Bravo device was successful, and the few EC-16s which were actually built were withdrawn and dismantled.

Runt II

Jughead was replaced in the Yankee test by the so-called "Runt II" device (the TX-24 bomb, initially the "emergency capability" EC-24), a modified form of the "Runt" device (the TX-17/EC-17) tested in Castle Romeo. Externally identical, the principal difference between them was in the fuel for the fusion stage. While Runt used natural lithium (with 7.5% of the Lithium-6 isotope), Runt II used the same partially enriched lithium (approximately 40% Lithium-6) as the "Shrimp" device tested in Bravo.

It was detonated on May 5, 1954, at Bikini......
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